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in the context of the minimal geometric deformation method, in this paper we implement the inverse problem in a black hole scenario. in order to deal with an anisotropic polytropic black hole solution of the einstein field equations with cosmological constant, the deformation method is slightly extended. after obtaining the isotropic sector and the decoupler for an anisotropic (a-)ds polytropic black hole solution, we emphasize a possible relation between anisotropization/isotropization and the violation of the energy conditions. | minimal geometric deformation in asymptotically (a-)ds space-times and the isotropic sector for a polytropic black hole |
multimessenger observations of gw170817 have not conclusively established whether the merger remnant is a black hole (bh) or a neutron star (ns). we show that a long-lived magnetized ns with a poloidal field b ≈ 1012 g is fully consistent with the electromagnetic dataset, when spin-down losses are dominated by gravitational wave (gw) emission. the required ellipticity ɛ ≳ 10-5 can result from a toroidal magnetic field component much stronger than the poloidal component, a configuration expected from an ns newly formed from a merger. abrupt magnetic dissipation of the toroidal component can lead to the appearance of x-ray flares, analogous to the one observed in gamma-ray burst (grb) afterglows. in the x-ray afterglow of gw170817, we identify a low-significance (≳3σ) temporal feature at 155 d, consistent with a sudden reactivation of the central ns. energy injection from the ns spin-down into the relativistic shock is negligible, and the underlying continuum is fully accounted for by a structured jet seen off-axis. whereas radio and optical observations probe the interaction of this jet with the surrounding medium, observations at x-ray wavelengths, performed with adequate sampling, open a privileged window on to the merger remnant. | a long-lived neutron star merger remnant in gw170817: constraints and clues from x-ray observations |
we investigate the properties of pole-skipping of the sound channel in which the translational symmetry is broken explicitly or spontaneously. for this purpose, we analyze, in detail, not only the holographic axion model, but also the magnetically charged black holes with two methods: the near-horizon analysis and quasi-normal mode computations. we find that the pole-skipping points are related with the chaotic properties, lyapunov exponent (λl) and butterfly velocity (vb), independently of the symmetry breaking patterns. we show that the diffusion constant (d) is bounded by d ≥vb2/λl, where d is the energy diffusion (crystal diffusion) bound for explicit (spontaneous) symmetry breaking. we confirm that the lower bound is obtained by the pole-skipping analysis in the low temperature limit. | bound of diffusion constants from pole-skipping points: spontaneous symmetry breaking and magnetic field |
in this paper, we study the deflection angle for wormhole-like static aether solution by using gibbons and werner technique in non-plasma, plasma, and dark matter mediums. for this purpose, we use optical spacetime geometry to calculate the gaussian optical curvature, then implement the gauss-bonnet theorem in weak field limits. moreover, we compute the deflection angle by using a technique known as keeton and petters technique. furthermore, we analyze the graphical behavior of the bending angle ψ with respect to the impact parameter b, mass m as an integration constant, and parameter q in non-plasma and plasma mediums. we examine that the deflection angle is exponentially increasing as direct with charge. also, we observe that for small values of b, ψ increases, and for large values of b the angle decreases. we also considered analysis to the shadow cast of the wormhole relative to an observer at various locations. comparing it the schwarzschild shadow, shadow cast is possible for wormhole as r <2 m . at r >2 m , the schwarzschild is larger. as r →∞ , we have seen that the behavior of the shadow, as well as the weak deflection angle, approaches that of the schwarzschild black hole. overall, the effect of plasma tends to decrease the value of the observables due to the wormhole geometry. | weak gravitational lensing in dark matter and plasma mediums for wormhole-like static aether solution |
we derive a gravitational block formula for the supersymmetric action for a general class of supersymmetric ads solutions, described by gk geometry. extremal points of this action describe supersymmetric ads3 solutions of type iib supergravity, sourced by d3-branes, and supersymmetric ads2 solutions of d =11 supergravity, sourced by m2-branes. in both cases, the branes are also wrapped over a two-dimensional orbifold known as a spindle, or a two-sphere. we develop various geometric methods for computing the gravitational block contributions, allowing us to recover previously known results for various explicit supergravity solutions, and to significantly generalize these results to other compactifications. for the ads3 solutions we give a general proof that our off-shell supersymmetric action agrees with an appropriate off-shell c-function in the dual field theory, establishing a very general exact result in holography. for the ads2 solutions our gravitational block formula allows us to obtain the entropy for supersymmetric, magnetically charged and accelerating black holes in ads4. | gravitational blocks, spindles and gk geometry |
quintessential dark energy with density ρ and pressure p is governed by an equation of state of the form p=ωqρ with the quintessential parameter ω_qin (-1;-1/3). we derive the geometry of quintessential rotating black holes, generalizing thus the kerr spacetimes. then we study the quintessential rotating black hole spacetimes with the special value of ωq = -2/3 when the resulting formulae are simple and easily tractable. we show that such special spacetimes can exist for the dimensionless quintessential parameter c < 1/6 and determine the critical rotational parameter a0 separating the black hole and naked singularity spacetime in dependence on the quintessential parameter c . for the spacetimes with ωq = -2/3 we give all the black hole characteristics and demonstrate local thermodynamical stability. we present the integrated geodesic equations in separated form and study in details the circular geodetical orbits. we give radii and parameters of the photon circular orbits, marginally bound and marginally stable orbits. we stress that the outer boundary on the existence of circular geodesics, given by the so-called static radius where the gravitational attraction of the black hole is balanced by the cosmic repulsion, does not depend on the dimensionless spin of the rotating black hole, similarly to the case of the kerr-de sitter spacetimes with vacuum dark energy. we also give restrictions on the dimensionless parameters c and a of the spacetimes allowing for existence of stable circular geodesics. finally, using numerical methods we generalize the discussion of the circular geodesics to the black holes with arbitrary quintessential parameter ωq. | rotating black hole solutions with quintessential energy |
the final stage of a binary black hole merger is ringdown, in which the system is described by a kerr black hole with quasinormal mode perturbations. it is far from straightforward to identify the time at which the ringdown begins. yet determining this time is important for precision tests of the general theory of relativity that compare an observed signal with quasinormal mode descriptions of the ringdown, such as tests of the no-hair theorem. we present an algorithmic method to analyze the choice of ringdown start time in the observed waveform. this method is based on determining how close the strong field is to a kerr black hole (kerrness). using numerical relativity simulations, we characterize the kerrness of the strong-field region close to the black hole using a set of local, gauge-invariant geometric and algebraic conditions that measure local isometry to kerr. we produce a map that associates each time in the gravitational waveform with a value of each of these kerrness measures; this map is produced by following outgoing null characteristics from the strong and near-field regions to the wave zone. we perform this analysis on a numerical relativity simulation with parameters consistent with gw150914—the first gravitational-wave detection. we find that the choice of ringdown start time of 3 ms after merger used in the gw150914 study [b. p. abbott et al. (<collab>virgo collaboration and ligo scientific collaboration</collab>), phys. rev. lett. 116, 221101 (2016)., 10.1103/physrevlett.116.221101] to test general relativity corresponds to a high dimensionless perturbation amplitude of ∼7.5 ×10-3 in the strong-field region. this suggests that in higher signal-to-noise detections, one would need to start analyzing the signal at a later time for studies that depend on the validity of black hole perturbation theory. | on choosing the start time of binary black hole ringdowns |
the previous studies of the island and double holography mainly focus on codimension-one branes. this paper explores the island on the codimension-two brane in ads/dcft. the codimension-two brane is closely related to conical singularity, which is very different from the codimension-one brane. we analyze the mass spectrum of gravitons on the codimension-two brane and find that the larger the brane tension is, the smaller the gravitational mass is. the massless mode is forbidden by either the boundary or normalization conditions. we prove that the first massive gravitational mode is located on the codimension-two brane; the larger the tension, the better the localization. it is similar to the case of codimension-one brane and builds an excellent physical foundation for the study of black hole evolution on codimension-two branes. we find that the page curve of eternal black holes can be recovered due to the island ending on the codimension-two brane. the new feature is that the extremal surface passing the horizon cannot be defined after some finite time in the no-island phase. fortunately, this unusual situation does not affect the page curve since it happens after page time. | island on codimension-two branes in ads/dcft |
we present new anisotropic black brane solutions in 5d einstein-dilaton-two-maxwell system. the anisotropic background is specified by an arbitrary dynamical exponent ν, a nontrivial warp factor, a non-zero dilaton field, a non-zero time component of the first maxwell field and a non-zero longitudinal magnetic component of the second maxwell field. the blackening function supports the van der waals-like phase transition between small and large black holes for a suitable first maxwell field charge. the isotropic case corresponding to ν = 1 and zero magnetic field reproduces previously known solutions. we investigate the anisotropy influence on the thermodynamic properties of our background, in particular, on the small/large black holes phase transition diagram. we discuss applications of the model to the bottom-up holographic qcd. the rg flow interpolates between the uv section with two suppressed transversal coordinates and the ir section with the suppressed time and longitudinal coordinates due to anisotropic character of our solution. we study the temporal wilson loops, extended in longitudinal and transversal directions, by calculating the minimal surfaces of the corresponding probing open string world-sheet in anisotropic backgrounds with various temperatures and chemical potentials. we find that dynamical wall locations depend on the orientation of the quark pairs, that gives a crossover transition line between confinement/deconfinement phases in the dual gauge theory. instability of the background leads to the appearance of the critical points ( μϑ,b, tϑ,b ) depending on the orientation ϑ of quark-antiquark pairs in respect to the heavy ions collision line. | holographic anisotropic background with confinement-deconfinement phase transition |
the exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. they give us information about their sources in the universe and the properties of the intergalactic medium. moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. on the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. after decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). this review, prepared within the cost action ca18108 "quantum gravity phenomenology in the multi-messenger approach", is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers. | quantum gravity phenomenology at the dawn of the multi-messenger era-a review |
epos is a monte carlo event generator for minimum bias hadronic interactions, used for both heavy ion interactions and cosmic ray air shower simulations. since the last public release in 2009, the large hadron collider (lhc) experiments have provided a number of very interesting data sets comprising minimum bias p -p ,p -pb, and pb-pb interactions. we describe the changes required to the model to reproduce in detail the new data available from the lhc and the consequences in the interpretation of these data. in particular we discuss the effect of the collective hadronization in p -p scattering. a different parametrization of flow has been introduced in the case of a small volume with high density of thermalized matter (core) reached in p -p compared to large volume produced in heavy ion collisions. both parametrizations depend only on the geometry and the amount of secondary particles entering in the core and not on the beam mass or energy. the transition between the two flow regimes can be tested with p -pb data. epos lhc is able to reproduce all minimum bias results for all particles with transverse momentum from pt=0 to a few gev/c . | epos lhc: test of collective hadronization with data measured at the cern large hadron collider |
the icecube neutrino observatory is a cubic-kilometer-scale high-energy neutrino detector built into the ice at the south pole. construction of icecube, the largest neutrino detector built to date, was completed in 2011 and enabled the discovery of high-energy astrophysical neutrinos. we describe here the design, production, and calibration of the icecube digital optical module (dom), the cable systems, computing hardware, and our methodology for drilling and deployment. we also describe the online triggering and data filtering systems that select candidate neutrino and cosmic ray events for analysis. due to a rigorous pre-deployment protocol, 98.4% of the doms in the deep ice are operating and collecting data. icecube routinely achieves a detector uptime of 99% by emphasizing software stability and monitoring. detector operations have been stable since construction was completed, and the detector is expected to operate at least until the end of the next decade. | the icecube neutrino observatory: instrumentation and online systems |
a precision measurement by ams of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 gv is presented based on 3.49 ×1 05 antiproton events and 2.42 ×1 09 proton events. the fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. in the absolute rigidity range ∼60 to ∼500 gv , the antiproton p ¯, proton p , and positron e+ fluxes are found to have nearly identical rigidity dependence and the electron e- flux exhibits a different rigidity dependence. below 60 gv, the (p ¯/p ), (p ¯/e+), and (p /e+) flux ratios each reaches a maximum. from ∼60 to ∼500 gv , the (p ¯/p ), (p ¯/e+), and (p /e+) flux ratios show no rigidity dependence. these are new observations of the properties of elementary particles in the cosmos. | antiproton flux, antiproton-to-proton flux ratio, and properties of elementary particle fluxes in primary cosmic rays measured with the alpha magnetic spectrometer on the international space station |
the central challenge in building a quantum computer is error correction. unlike classical bits, which are susceptible to only one type of error, quantum bits (qubits) are susceptible to two types of error, corresponding to flips of the qubit state about the x and z directions. although the heisenberg uncertainty principle precludes simultaneous monitoring of x- and z-flips on a single qubit, it is possible to encode quantum information in large arrays of entangled qubits that enable accurate monitoring of all errors in the system, provided that the error rate is low1. another crucial requirement is that errors cannot be correlated. here we characterize a superconducting multiqubit circuit and find that charge noise in the chip is highly correlated on a length scale over 600 micrometres; moreover, discrete charge jumps are accompanied by a strong transient reduction of qubit energy relaxation time across the millimetre-scale chip. the resulting correlated errors are explained in terms of the charging event and phonon-mediated quasiparticle generation associated with absorption of γ-rays and cosmic-ray muons in the qubit substrate. robust quantum error correction will require the development of mitigation strategies to protect multiqubit arrays from correlated errors due to particle impacts. | correlated charge noise and relaxation errors in superconducting qubits |
the pierre auger observatory, located on a vast, high plain in western argentina, is the world's largest cosmic ray observatory. the objectives of the observatory are to probe the origin and characteristics of cosmic rays above 1017 ev and to study the interactions of these, the most energetic particles observed in nature. the auger design features an array of 1660 water cherenkov particle detector stations spread over 3000 km2 overlooked by 24 air fluorescence telescopes. in addition, three high elevation fluorescence telescopes overlook a 23.5 km2, 61-detector infilled array with 750 m spacing. the observatory has been in successful operation since completion in 2008 and has recorded data from an exposure exceeding 40,000 km2 sr yr. this paper describes the design and performance of the detectors, related subsystems and infrastructure that make up the observatory. | the pierre auger cosmic ray observatory |
a precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 gv to 1.8 tv is presented based on 300 million events. knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. we present the detailed variation with rigidity of the flux spectral index for the first time. the spectral index progressively hardens at high rigidities. | precision measurement of the proton flux in primary cosmic rays from rigidity 1 gv to 1.8 tv with the alpha magnetic spectrometer on the international space station |
motivated by principles from the swampland program, which characterize requirements for a consistent uv completion of quantum gravity, combined with observational data, we are led to a unique corner of the quantum gravity landscape. in particular, using the distance/duality conjecture and the smallness of dark energy, we predict the existence of a light tower of states and a unique extra mesoscopic dimension of length l ∼λ−1/4∼10−6m , with extra massless fermions propagating on it. this automatically leads to a candidate for a tower of sterile neutrinos, and an associated active neutrino mass scale mν∼<h>2λ−1/12mpl−2/3. moreover, assuming the mechanism for stabilization of this dark dimension leads to similar masses for active and sterile neutrinos we are led to the prediction of a higgs vev <h >∼λ1/6mpl1/3. another prediction of the scenario is a species scale m ̂∼λ1/12mpl2/3∼109-1010 gev, corresponding to the higher-dimensional planck scale. this energy scale may be related to the resolution of the instability of the higgs effective potential present at a scale of ~1011 gev. we also speculate about the interplay between this energy scale and the gzk limit on ultra-high energy cosmic rays. | the dark dimension and the swampland |
knowledge of the rigidity dependence of the boron to carbon flux ratio (b/c) is important in understanding the propagation of cosmic rays. the precise measurement of the b /c ratio from 1.9 gv to 2.6 tv, based on 2.3 million boron and 8.3 million carbon nuclei collected by ams during the first 5 years of operation, is presented. the detailed variation with rigidity of the b /c spectral index is reported for the first time. the b /c ratio does not show any significant structures in contrast to many cosmic ray models that require such structures at high rigidities. remarkably, above 65 gv, the b /c ratio is well described by a single power law rδ with index δ =-0.333 ±0.014 (fit ) ±0.005 (syst ) , in good agreement with the kolmogorov theory of turbulence which predicts δ =-1 /3 asymptotically. | precision measurement of the boron to carbon flux ratio in cosmic rays from 1.9 gv to 2.6 tv with the alpha magnetic spectrometer on the international space station |
we report the observation of new properties of primary cosmic rays he, c, and o measured in the rigidity (momentum/charge) range 2 gv to 3 tv with 90 ×106 helium, 8.4 ×106 carbon, and 7.0 ×106 oxygen nuclei collected by the alpha magnetic spectrometer (ams) during the first five years of operation. above 60 gv, these three spectra have identical rigidity dependence. they all deviate from a single power law above 200 gv and harden in an identical way. | observation of the identical rigidity dependence of he, c, and o cosmic rays at high rigidities by the alpha magnetic spectrometer on the international space station |
scalable quantum computing can become a reality with error correction, provided that coherent qubits can be constructed in large arrays1,2. the key premise is that physical errors can remain both small and sufficiently uncorrelated as devices scale, so that logical error rates can be exponentially suppressed. however, impacts from cosmic rays and latent radioactivity violate these assumptions. an impinging particle can ionize the substrate and induce a burst of quasiparticles that destroys qubit coherence throughout the device. high-energy radiation has been identified as a source of error in pilot superconducting quantum devices3-5, but the effect on large-scale algorithms and error correction remains an open question. elucidating the physics involved requires operating large numbers of qubits at the same rapid timescales necessary for error correction. here, we use space- and time-resolved measurements of a large-scale quantum processor to identify bursts of quasiparticles produced by high-energy rays. we track the events from their initial localized impact as they spread, simultaneously and severely limiting the energy coherence of all qubits and causing chip-wide failure. our results provide direct insights into the impact of these damaging error bursts and highlight the necessity of mitigation to enable quantum computing to scale. | resolving catastrophic error bursts from cosmic rays in large arrays of superconducting qubits |
sub-gev dark matter particles up-scattered by cosmic rays gain enough kinetic energy to pass the thresholds of large volume detectors on earth. we then use public super-kamiokande and miniboone data to derive a novel limit on the scattering cross section of dark matter with electrons that extends down to sub-kev masses, closing a previously allowed wide region of parameter space. we finally discuss search strategies and prospects at existing and planned neutrino facilities. | light dark matter at neutrino experiments |
models of the production of cosmogenic nuclides typically incorporate an adjustable production rate parameter that is scaled for variations in production with latitude and altitude. in practice, this production rate parameter is set by calibration of the model using cosmogenic nuclide data from sites with independent age constraints. in this paper, we describe a calibration procedure developed during the cosmic-ray produced nuclide systematics on earth (cronus-earth) project and its application to an extensive data set that included both new cronus-earth samples and samples from previously published studies. we considered seven frameworks for elevation and latitude scaling and five commonly used cosmogenic nuclides, 3he, 10be, 14c, 26al, and 36cl. in general, the results show that the calibrated production rates fail statistical tests of goodness-of-fit. one conclusion from the calibration results is that two newly developed scaling frameworks and the widely used lal scaling framework provide qualitatively similar fits to the data, while neutron-monitor based scaling frameworks have much poorer fit to the data. to further test the fitted models, we computed site ages for a number of secondary sites not included in the primary calibration data set. the root-mean-square percent differences between the median computed ages for these secondary sites and independent ages range from 7.1% to 27.1%, differences that are much larger than the typical uncertainties in the site ages. the results indicate that there are substantial unresolved difficulties in modeling cosmogenic nuclide production and the calibration of production rates. | geological calibration of spallation production rates in the cronus-earth project |
technologies that rely on quantum bits (qubits) require long coherence times and high-fidelity operations1. superconducting qubits are one of the leading platforms for achieving these objectives2,3. however, the coherence of superconducting qubits is affected by the breaking of cooper pairs of electrons4-6. the experimentally observed density of the broken cooper pairs, referred to as quasiparticles, is orders of magnitude higher than the value predicted at equilibrium by the bardeen-cooper-schrieffer theory of superconductivity7-9. previous work10-12 has shown that infrared photons considerably increase the quasiparticle density, yet even in the best-isolated systems, it remains much higher10 than expected, suggesting that another generation mechanism exists13. here we provide evidence that ionizing radiation from environmental radioactive materials and cosmic rays contributes to this observed difference. the effect of ionizing radiation leads to an elevated quasiparticle density, which we predict would ultimately limit the coherence times of superconducting qubits of the type measured here to milliseconds. we further demonstrate that radiation shielding reduces the flux of ionizing radiation and thereby increases the energy-relaxation time. albeit a small effect for today's qubits, reducing or mitigating the impact of ionizing radiation will be critical for realizing fault-tolerant superconducting quantum computers. | impact of ionizing radiation on superconducting qubit coherence |
direct detection experiments tend to lose sensitivity in searches for sub-mev light dark matter candidates due to the threshold of recoil energy. however, such light dark matter particles could be accelerated by energetic cosmic rays, such that they could be detected with existing detectors. we derive constraints on the scattering of a boosted light dark matter particle and electron from the xenon100/1t experiment. we illustrate that the energy dependence of the cross section plays a crucial role in improving both the detection sensitivity and also the complementarity of direct detection and other experiments. * supported in part by the national science foundation of china (11725520, 11675002, 11635001). qfx is also supported by the china postdoctoral science foundation (8206300015) | searching for sub-mev boosted dark matter from xenon electron direct detection |
in this report we review the important progress made in recent years towards understanding the experimental data on ultra-high-energy (e ≳ 109 gev) cosmic rays. we begin with a general survey of the available data, including a description of the energy spectrum, the nuclear composition, and the distribution of arrival directions. at this point we also give a synopsis of experimental techniques. after that, we introduce the fundamentals of cosmic ray acceleration and energy loss during propagation, with a view of discussing the conjectured nearby sources. next, we survey the state of the art regarding the high- and ultra-high-energy cosmic neutrinos which may be produced in association with the observed cosmic rays. these neutrinos could constitute key messengers identifying currently unknown cosmic accelerators, possibly in the distant universe, because their propagation is not influenced by background photon or magnetic fields. subsequently, we summarize the phenomenology of cosmic ray air showers. we describe the hadronic interaction models used to extrapolate results from collider data to ultra-high energies and the main electromagnetic processes that govern the longitudinal shower evolution. armed with these two principal shower ingredients and motivation from the underlying physics, we describe the different methods proposed to distinguish the primary particle species. in the end, we explore how ultra-high-energy cosmic rays can be used as probes of beyond standard model physics models. | ultra-high-energy cosmic rays |
the orbiting carbon observatory-2 (oco-2) carries and points a three-channel imaging grating spectrometer designed to collect high-resolution, co-boresighted spectra of reflected sunlight within the molecular oxygen (o2) a-band at 0.765 microns and the carbon dioxide (co2) bands at 1.61 and 2.06 microns. these measurements are calibrated and then combined into soundings that are analyzed to retrieve spatially resolved estimates of the column-averaged co2 dry-air mole fraction, xco2. variations of xco2 in space and time are then analyzed in the context of the atmospheric transport to quantify surface sources and sinks of co2. this is a particularly challenging remote-sensing observation because all but the largest emission sources and natural absorbers produce only small (< 0.25 %) changes in the background xco2 field. high measurement precision is therefore essential to resolve these small variations, and high accuracy is needed because small biases in the retrieved xco2 distribution could be misinterpreted as evidence for co2 fluxes.to meet its demanding measurement requirements, each oco-2 spectrometer channel collects 24 spectra s-1 across a narrow (< 10 km) swath as the observatory flies over the sunlit hemisphere, yielding almost 1 million soundings each day. on monthly timescales, between 7 and 12 % of these soundings pass the cloud screens and other data quality filters to yield full-column estimates of xco2. each of these soundings has an unprecedented combination of spatial resolution (< 3 km2/sounding), spectral resolving power (λ/δλ > 17 000), dynamic range (∼ 104), and sensitivity (continuum signal-to-noise ratio > 400).the oco-2 instrument performance was extensively characterized and calibrated prior to launch. in general, the instrument has performed as expected during its first 18 months in orbit. however, ongoing calibration and science analysis activities have revealed a number of subtle radiometric and spectroscopic challenges that affect the yield and quality of the oco-2 data products. these issues include increased numbers of bad pixels, transient artifacts introduced by cosmic rays, radiance discontinuities for spatially non-uniform scenes, a misunderstanding of the instrument polarization orientation, and time-dependent changes in the throughput of the oxygen a-band channel. here, we describe the oco-2 instrument, its data products, and its on-orbit performance. we then summarize calibration challenges encountered during its first 18 months in orbit and the methods used to mitigate their impact on the calibrated radiance spectra distributed to the science community. | the on-orbit performance of the orbiting carbon observatory-2 (oco-2) instrument and its radiometrically calibrated products |
the field of particle physics is at the crossroads. the discovery of a higgs-like boson completed the standard model (sm), but the lacking observation of convincing resonances beyond the sm (bsm) offers no guidance for the future of particle physics. on the other hand, the motivation for new physics has not diminished and is, in fact, reinforced by several striking anomalous results in many experiments. here we summarise the status of the most significant anomalies, including the most recent results for the flavour anomalies, the multi-lepton anomalies at the lhc, the higgs-like excess at around 96 gev, and anomalies in neutrino physics, astrophysics, cosmology, and cosmic rays. while the lhc promises up to 4 ab-1 of integrated luminosity and far-reaching physics programmes to unveil bsm physics, we consider the possibility that the latter could be tested with present data, but that systemic shortcomings of the experiments and their search strategies may preclude their discovery for several reasons, including: final states consisting in soft particles only, associated production processes, qcd-like final states, close-by sm resonances, and susy scenarios where no missing energy is produced. new search strategies could help to unveil the hidden bsm signatures, devised by making use of the cern open data as a new testing ground. we discuss the cern open data with its policies, challenges, and potential usefulness for the community. we showcase the example of the cms collaboration, which is the only collaboration regularly releasing some of its data. we find it important to stress that individuals using public data for their own research does not imply competition with experimental efforts, but rather provides unique opportunities to give guidance for further bsm searches by the collaborations. wide access to open data is paramount to fully exploit the lhcs potential. | unveiling hidden physics at the lhc |
the icecube collaboration has previously discovered a high-energy astrophysical neutrino flux using neutrino events with interaction vertices contained within the instrumented volume of the icecube detector. we present a complementary measurement using charged current muon neutrino events where the interaction vertex can be outside this volume. as a consequence of the large muon range the effective area is significantly larger but the field of view is restricted to the northern hemisphere. icecube data from 2009 through 2015 have been analyzed using a likelihood approach based on the reconstructed muon energy and zenith angle. at the highest neutrino energies between 194 {tev} and 7.8 {pev} a significant astrophysical contribution is observed, excluding a purely atmospheric origin of these events at 5.6σ significance. the data are well described by an isotropic, unbroken power-law flux with a normalization at 100 {tev} neutrino energy of ({0.90}-0.27+0.30)× {10}-18 {{gev}}-1 {{cm}}-2 {{{s}}}-1 {{sr}}-1 and a hard spectral index of γ =2.13+/- 0.13. the observed spectrum is harder in comparison to previous icecube analyses with lower energy thresholds which may indicate a break in the astrophysical neutrino spectrum of unknown origin. the highest-energy event observed has a reconstructed muon energy of (4.5+/- 1.2) {pev} which implies a probability of less than 0.005 % for this event to be of atmospheric origin. analyzing the arrival directions of all events with reconstructed muon energies above 200 {tev} no correlation with known γ-ray sources was found. using the high statistics of atmospheric neutrinos we report the current best constraints on a prompt atmospheric muon neutrino flux originating from charmed meson decays which is below 1.06 in units of the flux normalization of the model in enberg et al. | observation and characterization of a cosmic muon neutrino flux from the northern hemisphere using six years of icecube data |
fundamental questions remain about the origin of newly formed atmospheric aerosol particles because data from laboratory measurements have been insufficient to build global models. in contrast, gas-phase chemistry models have been based on laboratory kinetics measurements for decades. we built a global model of aerosol formation by using extensive laboratory measurements of rates of nucleation involving sulfuric acid, ammonia, ions, and organic compounds conducted in the cern cloud (cosmics leaving outdoor droplets) chamber. the simulations and a comparison with atmospheric observations show that nearly all nucleation throughout the present-day atmosphere involves ammonia or biogenic organic compounds, in addition to sulfuric acid. a considerable fraction of nucleation involves ions, but the relatively weak dependence on ion concentrations indicates that for the processes studied, variations in cosmic ray intensity do not appreciably affect climate through nucleation in the present-day atmosphere. | global atmospheric particle formation from cern cloud measurements |
the sun provides the principal energy input into the earth system and solar variability represents a significant external climate forcing. although observations of solar activity (sunspots) cover only the last about 400 years, radionuclides produced by cosmic rays and stored in tree rings or ice cores serve as proxies for solar activity extending back thousands of years. however, the presence of weather-induced noise or low temporal resolution of long, precisely dated records hampers cosmogenic nuclide-based studies of short-term solar variability such as the 11-yr schwabe cycle. here we present a continuous, annually resolved atmospheric 14c concentration (fractionation-corrected ratio of 14co2 to co2) record reconstructed from absolutely dated tree rings covering nearly all of the last millennium (ad 969-1933). the high-resolution and precision 14c record reveals the presence of the schwabe cycle over the entire time range. the record confirms the ad 993 solar energetic particle event and reveals two new candidates (ad 1052 and ad 1279), indicating that strong solar events that might be harmful to modern electronic systems probably occur more frequently than previously thought. in addition to showing decadal-scale solar variability over the last millennium, the high-temporal-resolution record of atmospheric radiocarbon also provides a useful benchmark for making radiocarbon dating more accurate over this interval. | eleven-year solar cycles over the last millennium revealed by radiocarbon in tree rings |
the great pyramid, or khufu’s pyramid, was built on the giza plateau in egypt during the fourth dynasty by the pharaoh khufu (cheops), who reigned from 2509 bc to 2483 bc. despite being one of the oldest and largest monuments on earth, there is no consensus about how it was built. to understand its internal structure better, we imaged the pyramid using muons, which are by-products of cosmic rays that are only partially absorbed by stone. the resulting cosmic-ray muon radiography allows us to visualize the known and any unknown voids in the pyramid in a non-invasive way. here we report the discovery of a large void (with a cross-section similar to that of the grand gallery and a minimum length of 30 metres) situated above the grand gallery. this constitutes the first major inner structure found in the great pyramid since the nineteenth century. the void, named scanpyramids’ big void, was first observed with nuclear emulsion films installed in the queen’s chamber, then confirmed with scintillator hodoscopes set up in the same chamber and finally re-confirmed with gas detectors outside the pyramid. this large void has therefore been detected with high confidence by three different muon detection technologies and three independent analyses. these results constitute a breakthrough for the understanding of the internal structure of khufu’s pyramid. although there is currently no information about the intended purpose of this void, these findings show how modern particle physics can shed new light on the world’s archaeological heritage. | discovery of a big void in khufu’s pyramid by observation of cosmic-ray muons |
high-energy tau neutrinos are rarely produced in atmospheric cosmic-ray showers or at cosmic particle accelerators, but are expected to emerge during neutrino propagation over cosmic distances due to flavor mixing. when high energy tau neutrinos interact inside the icecube detector, two spatially separated energy depositions may be resolved, the first from the charged current interaction and the second from the tau lepton decay. we report a novel analysis of 7.5 years of icecube data that identifies two candidate tau neutrinos among the 60 "high-energy starting events" (hese) collected during that period. the hese sample offers high purity, all-sky sensitivity, and distinct observational signatures for each neutrino flavor, enabling a new measurement of the flavor composition. the measured astrophysical neutrino flavor composition is consistent with expectations, and an astrophysical tau neutrino flux is indicated at 2.8σ significance. | detection of astrophysical tau neutrino candidates in icecube |
the alpha magnetic spectrometer (ams) is a precision particle physics detector on the international space station (iss) conducting a unique, long-duration mission of fundamental physics research in space. the physics objectives include the precise studies of the origin of dark matter, antimatter, and cosmic rays as well as the exploration of new phenomena. following a 16-year period of construction and testing, and a precursor flight on the space shuttle, ams was installed on the iss on may 19, 2011. in this report we present results based on 120 billion charged cosmic ray events up to multi-tev energies. this includes the fluxes of positrons, electrons, antiprotons, protons, and nuclei. these results provide unexpected information, which cannot be explained by the current theoretical models. the accuracy and characteristics of the data, simultaneously from many different types of cosmic rays, provide unique input to the understanding of origins, acceleration, and propagation of cosmic rays. | the alpha magnetic spectrometer (ams) on the international space station: part ii - results from the first seven years |
papers on the properties of the atmospheric and astrophysical neutrino flux submitted to the 35th international cosmic ray conference (icrc 2017, busan, south korea) by the icecube collaboration | the icecube neutrino observatory - contributions to icrc 2017 part ii: properties of the atmospheric and astrophysical neutrino flux |
we present the fourth in a series of catalogs of gamma-ray bursts (grbs) observed with fermi's gamma-ray burst monitor (fermi-gbm). it extends the six year catalog by four more years, now covering the 10 year time period from trigger enabling on 2008 july 12 to 2018 july 11. during this time period gbm triggered almost twice a day on transient events, 2356 of which we identified as cosmic grbs. additional trigger events were due to solar flare events, magnetar burst activities, and terrestrial gamma-ray flashes. the intention of the gbm grb catalog series is to provide updated information to the community on the most important observables of the gbm-detected grbs. for each grb the location and main characteristics of the prompt emission, the duration, peak flux, and fluence are derived. the latter two quantities are calculated for the 50-300 kev energy band, where the maximum energy release of grbs in the instrument reference system is observed and also for a broader energy band from 10-1000 kev, exploiting the full energy range of gbm's low-energy detectors. furthermore, information is given on the settings of the triggering criteria and exceptional operational conditions during years 7 to 10 in the mission. this fourth catalog is an official product of the fermi-gbm science team, and the data files containing the complete results are available from the high-energy astrophysics science archive research center. | the fourth fermi-gbm gamma-ray burst catalog: a decade of data |
new particle formation has been estimated to produce around half of cloud-forming particles in the present-day atmosphere, via gas-to-particle conversion. here we assess the importance of new particle formation (npf) for both the present-day and the preindustrial atmospheres. we use a global aerosol model with parametrizations of npf from previously published cloud chamber experiments involving sulfuric acid, ammonia, organic molecules, and ions. we find that npf produces around 67% of cloud condensation nuclei at 0.2% supersaturation (ccn0.2%) at the level of low clouds in the preindustrial atmosphere (estimated uncertainty range 45-84%) and 54% in the present day (estimated uncertainty range 38-66%). concerning causes, we find that the importance of biogenic volatile organic compounds (bvocs) in npf and ccn formation is greater than previously thought. removing bvocs and hence all secondary organic aerosol from our model reduces low-cloud-level ccn concentrations at 0.2% supersaturation by 26% in the present-day atmosphere and 41% in the preindustrial. around three quarters of this reduction is due to the tiny fraction of the oxidation products of bvocs that have sufficiently low volatility to be involved in npf and early growth. furthermore, we estimate that 40% of preindustrial ccn0.2% are formed via ion-induced npf, compared with 27% in the present day, although we caution that the ion-induced fraction of npf involving bvocs is poorly measured at present. our model suggests that the effect of changes in cosmic ray intensity on ccn is small and unlikely to be comparable to the effect of large variations in natural primary aerosol emissions. | causes and importance of new particle formation in the present-day and preindustrial atmospheres |
knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. a precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 gv to 3 tv based on 50 million events is presented and compared to the proton flux. the detailed variation with rigidity of the helium flux spectral index is presented for the first time. the spectral index progressively hardens at rigidities larger than 100 gv. the rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 gv and then becomes constant; the flux ratio above 45 gv is well described by a single power law. | precision measurement of the helium flux in primary cosmic rays of rigidities 1.9 gv to 3 tv with the alpha magnetic spectrometer on the international space station |
surface mass balance (smb) provides mass input to the surface of the antarctic and greenland ice sheets and therefore comprises an important control on ice sheet mass balance and resulting contribution to global sea level change. as ice sheet smb varies highly across multiple scales of space (meters to hundreds of kilometers) and time (hourly to decadal), it is notoriously challenging to observe and represent in models. in addition, smb consists of multiple components, all of which depend on complex interactions between the atmosphere and the snow/ice surface, large-scale atmospheric circulation and ocean conditions, and ice sheet topography. in this review, we present the state-of-the-art knowledge and recent advances in ice sheet smb observations and models, highlight current shortcomings, and propose future directions. novel observational methods allow mapping smb across larger areas, longer time periods, and/or at very high (subdaily) temporal frequency. as a recent observational breakthrough, cosmic ray counters provide direct estimates of smb, circumventing the need for accurate snow density observations upon which many other techniques rely. regional atmospheric climate models have drastically improved their simulation of ice sheet smb in the last decade, thanks to the inclusion or improved representation of essential processes (e.g., clouds, blowing snow, and snow albedo), and by enhancing horizontal resolution (5-30 km). future modeling efforts are required in improving earth system models to match regional atmospheric climate model performance in simulating ice sheet smb, and in reinforcing the efforts in developing statistical and dynamic downscaling to represent smaller-scale smb processes. | observing and modeling ice sheet surface mass balance |
cosmic rays were first discovered over a century ago, however the origin of their high-energy component remains elusive. uncovering astrophysical neutrino sources would provide smoking gun evidence for ultrahigh energy cosmic ray production. the icecube neutrino observatory discovered a diffuse astrophysical neutrino flux in 2013 and observed the first compelling evidence for a high-energy neutrino source in 2017. next-generation telescopes with improved sensitivity are required to resolve the diffuse flux. a detector near the equator will provide a unique viewpoint of the neutrino sky, complementing icecube and other neutrino telescopes in the northern hemisphere. here we present results from an expedition to the north-eastern region of the south china sea. a favorable neutrino telescope site was found on an abyssal plain at a depth of $\sim$ 3.5 km. below 3 km, the sea current speed was measured to be $v_{\mathrm{c}}<$ 10 cm/s, with absorption and scattering lengths for cherenkov light of $\lambda_{\mathrm{abs} }\simeq$ 27 m and $\lambda_{\mathrm{sca} }\simeq$ 63 m, respectively. accounting for these measurements, we present the preliminary design and capabilities of a next-generation neutrino telescope, the tropical deep-sea neutrino telescope (trident). with its advanced photon-detection technologies and size, trident expects to discover the icecube steady source candidate ngc 1068 within 2 years of operation. this level of sensitivity will open a new arena for diagnosing the origin of cosmic rays and measuring astronomical neutrino oscillation over fixed baselines. | proposal for a neutrino telescope in south china sea |
we report a novel search for the cosmic-ray boosted dark matter using the 100 tonne .day full dataset of the pandax-ii detector located at the china jinping underground laboratory. with the extra energy gained from the cosmic rays, sub-gev dark matter particles can produce visible recoil signals in the detector. the diurnal modulations in rate and energy spectrum are utilized to further enhance the signal sensitivity. our result excludes the dark matter-nucleon elastic scattering cross section between 10-31 and 10-28 cm2 for dark matter masses from 0.1 mev /c2 to 0.1 gev /c2 , with a large parameter space previously unexplored by experimental collaborations. | search for cosmic-ray boosted sub-gev dark matter at the pandax-ii experiment |
we review progress in the study of antinuclei, starting from dirac's equation and the discovery of the positron in cosmic-ray events. the development of proton accelerators led to the discovery of antiprotons, followed by the first antideuterons, demonstrating that antinucleons bind into antinuclei. with the development of heavy-ion programs at the brookhaven ags and cern sps, it was demonstrated that central collisions of heavy nuclei offer a fertile ground for research and discoveries in the area of antinuclei. in this review, we emphasize recent observations at brookhaven's relativistic heavy ion collider and at cern's large hadron collider, namely, the antihypertriton and the antihelium-4, as well as measurements of the mass difference between light nuclei and antinuclei, and the interaction between antiprotons. physics implications of the new observations and different production mechanisms are discussed. we also consider implications for related fields, such as hypernuclear physics and space-based cosmic-ray experiments. | antinuclei in heavy-ion collisions |
ultrahigh energy cosmic ray air showers probe particle physics at energies beyond the reach of accelerators. here we introduce a new method to test hadronic interaction models without relying on the absolute energy calibration, and apply it to events with primary energy 6-16 eev (ecm=110 - 170 tev ), whose longitudinal development and lateral distribution were simultaneously measured by the pierre auger observatory. the average hadronic shower is 1.33 ±0.16 (1.61 ±0.21 ) times larger than predicted using the leading lhc-tuned models epos-lhc (qgsjetii-04), with a corresponding excess of muons. | testing hadronic interactions at ultrahigh energies with air showers measured by the pierre auger observatory |
the current version of the fermi large area telescope data (p8r2) has been publicly available since june 2015, with the caveat that the residual background of all event classes, except ultracleanveto, was not fully isotropic: it was enhanced by a factor ~2 at 1-3 gev within ~20 deg of the ecliptic compared to the poles. by investigating the residual background using data only, we were able to find two sources of residual background: one due to non-interacting heavy ions and one due to cosmic-ray electrons leaking through the ribbons of the anti-coincidence detector, the latter source being responsible for the background anisotropy. a set of simple cuts allows us to reject these events while losing less than 1% of the source class acceptance. this new selection has been used to produce a new version of the lat data (p8r3). | fermi-lat improved pass~8 event selection |
the protodune-sp detector is a single-phase liquid argon time projection chamber with an active volume of 7.2× 6.1× 7.0 m3. it is installed at the cern neutrino platform in a specially-constructed beam that delivers charged pions, kaons, protons, muons and electrons with momenta in the range 0.3 gev/c to 7 gev/c. beam line instrumentation provides accurate momentum measurements and particle identification. the protodune-sp detector is a prototype for the first far detector module of the deep underground neutrino experiment, and it incorporates full-size components as designed for that module. this paper describes the beam line, the time projection chamber, the photon detectors, the cosmic-ray tagger, the signal processing and particle reconstruction. it presents the first results on protodune-sp's performance, including noise and gain measurements, de/dx calibration for muons, protons, pions and electrons, drift electron lifetime measurements, and photon detector noise, signal sensitivity and time resolution measurements. the measured values meet or exceed the specifications for the dune far detector, in several cases by large margins. protodune-sp's successful operation starting in 2018 and its production of large samples of high-quality data demonstrate the effectiveness of the single-phase far detector design. | first results on protodune-sp liquid argon time projection chamber performance from a beam test at the cern neutrino platform |
the goal of this report is to give a comprehensive overview of the rich field of forward physics, with a special attention to the topics that can be studied at the lhc. the report starts presenting a selection of the monte carlo simulation tools currently available, chapter 2, then enters the rich phenomenology of qcd at low, chapter 3, and high, chapter 4, momentum transfer, while the unique scattering conditions of central exclusive production are analyzed in chapter 5. the last two experimental topics, cosmic ray and heavy ion physics are presented in the chapter 6 and 7 respectively. chapter 8 is dedicated to the bfkl dynamics, multiparton interactions, and saturation. the report ends with an overview of the forward detectors at lhc. each chapter is correlated with a comprehensive bibliography, attempting to provide to the interested reader with a wide opportunity for further studies. | lhc forward physics |
cosmic rays are atomic nuclei arriving from outer space that reach the highest energies observed in nature. clues to their origin come from studying the distribution of their arrival directions. using 3 × 104 cosmic rays with energies above 8 × 1018 electron volts, recorded with the pierre auger observatory from a total exposure of 76,800 km2 sr year, we determined the existence of anisotropy in arrival directions. the anisotropy, detected at more than a 5.2σ level of significance, can be described by a dipole with an amplitude of 6.50.9+1.3 percent toward right ascension αd = 100 ± 10 degrees and declination δd = -24-13+12 degrees. that direction indicates an extragalactic origin for these ultrahigh-energy particles. | observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 × 1018 ev |
papers on atmospheric and astrophysical diffuse neutrino searches of all flavors submitted to the 34th international cosmic ray conference (icrc 2015, the hague) by the icecube collaboration. | the icecube neutrino observatory - contributions to icrc 2015 part ii: atmospheric and astrophysical diffuse neutrino searches of all flavors |
error-corrected quantum computers can only work if errors are small and uncorrelated. here, i show how cosmic rays or stray background radiation affects superconducting qubits by modeling the phonon to electron/quasiparticle down-conversion physics. for present designs, the model predicts about 57% of the radiation energy breaks cooper pairs into quasiparticles, which then vigorously suppress the qubit energy relaxation time (t1 ~ 600 ns) over a large area (cm) and for a long time (ms). such large and correlated decay kills error correction. using this quantitative model, i show how this energy can be channeled away from the qubit so that this error mechanism can be reduced by many orders of magnitude. i also comment on how this affects other solid-state qubits. | saving superconducting quantum processors from decay and correlated errors generated by gamma and cosmic rays |
faser, the forward search experiment, is an experiment dedicated to searching for light, extremely weakly-interacting particles at cern's large hadron collider (lhc). such particles may be produced in the very forward direction of the lhc's high-energy collisions and then decay to visible particles inside the faser detector, which is placed 480 m downstream of the atlas interaction point, aligned with the beam collisions axis. faser also includes a sub-detector, faser$\nu$, designed to detect neutrinos produced in the lhc collisions and to study their properties. in this paper, each component of the faser detector is described in detail, as well as the installation of the experiment system and its commissioning using cosmic-rays collected in september 2021 and during the lhc pilot beam test carried out in october 2021. faser will start taking lhc collision data in 2022, and will run throughout lhc run 3. | the faser detector |
precision measurements of cosmic ray positrons are presented up to 1 tev based on 1.9 million positrons collected by the alpha magnetic spectrometer on the international space station. the positron flux exhibits complex energy dependence. its distinctive properties are (a) a significant excess starting from 25.2 ±1.8 gev compared to the lower-energy, power-law trend, (b) a sharp dropoff above 28 4-64+91 gev , (c) in the entire energy range the positron flux is well described by the sum of a term associated with the positrons produced in the collision of cosmic rays, which dominates at low energies, and a new source term of positrons, which dominates at high energies, and (d) a finite energy cutoff of the source term of es=81 0-180+310 gev is established with a significance of more than 4 σ . these experimental data on cosmic ray positrons show that, at high energies, they predominantly originate either from dark matter annihilation or from other astrophysical sources. | towards understanding the origin of cosmic-ray positrons |
weakly interacting neutrinos are ideal astronomical messengers because they travel through space without deflection by magnetic fields and, essentially, without absorption. their weak interaction also makes them notoriously difficult to detect, with observation of high-energy neutrinos from distant sources requiring kilometer-scale detectors. the icecube project transformed a cubic kilometer of natural antarctic ice at the geographic south pole into a cherenkov detector. it discovered a flux of cosmic neutrinos in the energy range from 10 tev to 10 pev, predominantly extragalactic in origin. their corresponding energy density is close to that of high-energy photons detected by gamma-ray satellites and ultra-high-energy cosmic rays observed with large surface detectors. neutrinos are therefore ubiquitous in the nonthermal universe, suggesting a more significant role of protons (nuclei) relative to electrons than previously anticipated. thus, anticipating an essential role for multimessenger astronomy, icecube is planning significant upgrades of the present instrument as well as a next-generation detector. similar detectors are under construction in the mediterranean sea and lake baikal. | opening a new window onto the universe with icecube |
in september 2017, the icecube neutrino observatory recorded a very-high-energy neutrino in directional coincidence with a blazar in an unusually bright gamma-ray state, txs0506 + 056 (refs1,2). blazars are prominent photon sources in the universe because they harbour a relativistic jet whose radiation is strongly collimated and amplified. high-energy atomic nuclei known as cosmic rays can produce neutrinos; thus, the recent detection may help in identifying the sources of the diffuse neutrino flux3 and the energetic cosmic rays. here we report a self-consistent analysis of the physical relation between the observed neutrino and the blazar, in particular the time evolution and spectral behaviour of neutrino and photon emission. we demonstrate that a moderate enhancement in the number of cosmic rays during the flare can yield a very strong increase in the neutrino flux, which is limited by co-produced hard x-rays and teraelectronvolt gamma rays. we also test typical radiation models4,5 for compatibility and identify several model classes6,7 as incompatible with the observations. we investigate to what degree the findings can be generalized to the entire population of blazars, determine the relation between their output in photons, neutrinos and cosmic rays, and suggest how to optimize the strategy of future observations. | modelling the coincident observation of a high-energy neutrino and a bright blazar flare |
the probe of extreme multi-messenger astrophysics (poemma) is designed to accurately observe ultra-high-energy cosmic rays (uhecrs) and cosmic neutrinos from space with sensitivity over the full celestial sky. poemma will observe the air fluorescence produced by extensive air showers (eass) from uhecrs and potentially uhe neutrinos above 20 eev. additionally, poemma has the ability to observe the cherenkov signal from upward-moving eass induced by earth-interacting tau neutrinos above 20 pev. the poemma spacecraft are designed to quickly re-orientate to follow up transient neutrino sources and obtain currently unparalleled neutrino flux sensitivity. developed as a nasa astrophysics probe-class mission, poemma consists of two identical satellites flying in loose formation in 525 km altitude orbits. each poemma instrument incorporates a wide field-of-view (45∘) schmidt telescope with an optical collecting area of over 6 m2. the hybrid focal surface of each telescope includes a fast (1 μs) near-ultraviolet camera for eas fluorescence observations and an ultrafast (10 ns) optical camera for cherenkov eas observations. in a 5-year mission, poemma will provide measurements that open new multi-messenger windows onto the most energetic events in the universe, enabling the study of new astrophysics and particle physics at these extreme energies. | the poemma (probe of extreme multi-messenger astrophysics) observatory |
several studies have pointed out an excess in the ams-02 antiproton spectrum at rigidities of 10-20 gv. its spectral properties were found to be consistent with a dark-matter particle of mass 50-100 gev which annihilates hadronically at roughly the thermal rate. in this paper, we reinvestigate the antiproton excess, including all relevant sources of systematic errors. most importantly, we perform a realistic estimate of the correlations in the ams-02 systematic error which could potentially "fake" a dark-matter signal. the dominant systematics in the relevant rigidity range originate from uncertainties in the cross sections for absorption of cosmic rays within the detector material. we calculate their correlations within the glauber-gribov theory of inelastic scattering. the ams-02 correlations enter our spectral search for dark matter in the form of covariance matrices, which we make publicly available for the cosmic-ray community. we find that the global significance of the antiproton excess is reduced to below 1 σ once all systematics, including the derived ams-02 error correlations, are taken into account. no significant preference for a dark-matter signal in the ams-02 antiproton data is found in the mass range 10-10 000 gev. | dark matter or correlated errors: systematics of the ams-02 antiproton excess |
we present a new version of the hadron interaction event generator sibyll. while the core ideas of the model have been preserved, the new version handles the production of baryon pairs and leading particles in a new way. in addition, production of charmed hadrons is included. updates to the model are informed by high-precision measurements of the total and inelastic cross sections with the forward detectors at the lhc that constrain the extrapolation to ultrahigh energy. minimum-bias measurements of particle spectra and multiplicities support the tuning of fragmentation parameters. this paper demonstrates the impact of these changes on air-shower observables such as xmax and nμ, drawing comparisons with other contemporary cosmic-ray interaction models. | hadronic interaction model sibyll 2.3d and extensive air showers |
results from the icecube neutrino observatory have recently provided compelling evidence for the existence of a high energy astrophysical neutrino flux utilizing a dominantly southern hemisphere data set consisting primarily of νe and ντ charged-current and neutral-current (cascade) neutrino interactions. in the analysis presented here, a data sample of approximately 35 000 muon neutrinos from the northern sky is extracted from data taken during 659.5 days of live time recorded between may 2010 and may 2012. while this sample is composed primarily of neutrinos produced by cosmic ray interactions in earth's atmosphere, the highest energy events are inconsistent with a hypothesis of solely terrestrial origin at 3.7 σ significance. these neutrinos can, however, be explained by an astrophysical flux per neutrino flavor at a level of φ (eν)=9.9-3.4+3.9×10-19 gev-1 cm-2 sr-1 s-1(eν/1 00 tev ) -2 , consistent with icecube's southern-hemisphere-dominated result. additionally, a fit for an astrophysical flux with an arbitrary spectral index is performed. we find a spectral index of 2.2-0.2+0.2 , which is also in good agreement with the southern hemisphere result. | evidence for astrophysical muon neutrinos from the northern sky with icecube |
general considerations in general relativity and quantum mechanics are known to potentially rule out continuous global symmetries in the context of any consistent theory of quantum gravity. assuming the validity of such considerations, we derive stringent bounds from gamma-ray, x-ray, cosmic-ray, neutrino, and cmb data on models that invoke global symmetries to stabilize the dark matter particle. we compute up-to-date, robust model-independent limits on the dark matter lifetime for a variety of planck-scale suppressed dimension-five effective operators. we then specialize our analysis and apply our bounds to specific models including the two-higgs-doublet, left-right, singlet fermionic, zee-babu, 3-3-1 and radiative see-saw models. assuming that (i) global symmetries are broken at the planck scale, that (ii) the non-renormalizable operators mediating dark matter decay have o (1) couplings, that (iii) the dark matter is a singlet field, and that (iv) the dark matter density distribution is well described by a nfw profile, we are able to rule out fermionic, vector, and scalar dark matter candidates across a broad mass range (kev-tev), including the wimp regime. | dark matter and global symmetries |
diffuse cluster radio sources, in the form of radio halos and relics, reveal the presence of cosmic rays and magnetic fields in the intracluster medium (icm). these cosmic rays are thought to be (re)accelerated through the icm turbulence and shock waves generated by cluster merger events. here we characterize the presence of diffuse radio emission in known galaxy clusters in the hetdex spring field, covering 424 deg2. for this, we developed a method to extract individual targets from lofar observations processed with the lotss ddf-pipeline software. this procedure enables improved calibration as well as the joint imaging and deconvolution of multiple pointings of selected targets. the calibration strategy can also be used for lofar low-band antenna and international-baseline observations. the fraction of planck psz2 catalog clusters with any diffuse radio emission apparently associated with the icm is 73 ± 17%. we detect a total of ten radio halos and twelve candidate halos in the hetdex spring field. of these ten radio halos, four are new discoveries, two of which are located in psz2 clusters. five clusters host radio relics, two of which are new discoveries. the fraction of radio halos in planck psz2 clusters is 31 ± 11%, or 62 ± 15% when including the candidate radio halos. based on these numbers, we expect that there will be at least 183 ± 65 radio halos found in the lotss survey in psz2 clusters, in agreement with past predictions. the integrated flux densities for the radio halos were computed by fitting exponential models to the radio images. from these flux densities, we determine the cluster mass (m500) and compton y parameter (y500) 150 mhz radio power (p150 mhz) scaling relations for planck psz2-detected radio halos. using bivariate correlated errors and intrinsic scatter orthogonal regression, we find slopes of 6.13 ± 1.11 and 3.32 ± 0.65 for the m500-p150 mhz and m500-p150 mhz relations, respectively. these values are consistent with the results of previous works. | lofar observations of galaxy clusters in hetdex. extraction and self-calibration of individual lofar targets |
in 1965 it was discovered that cosmic ray air showers emit impulsive radio signals at frequencies below 100 mhz. after a period of intense research in the 1960s and 1970s, however, interest in the detection technique faded almost completely. with the availability of powerful digital signal processing techniques, new attempts at measuring cosmic ray air showers via their radio emission were started at the beginning of the new millennium. starting with modest, small-scale digital prototype setups, the field has evolved, matured and grown very significantly in the past decade. today's second-generation digital radio detection experiments consist of up to hundreds of radio antennas or cover areas of up to 17 km2. we understand the physics of the radio emission in extensive air showers in detail and have developed analysis strategies to accurately derive from radio signals parameters which are related to the astrophysics of the primary cosmic ray particles, in particular their energy, arrival direction and estimators for their mass. in parallel to these successes, limitations inherent in the physics of the radio signals have also become increasingly clear. in this article, we review the progress of the past decade and the current state of the field, discuss the current paradigm of the radio emission physics and present the experimental evidence supporting it. finally, we discuss the potential for future applications of the radio detection technique to advance the field of cosmic ray physics. | radio detection of cosmic ray air showers in the digital era |
boron nuclei in cosmic rays (crs) are believed to be mainly produced by the fragmentation of heavier nuclei, such as carbon and oxygen, via collisions with the interstellar matter. therefore, the boron-to-carbon flux ratio (b/c) and the boron-to-oxygen flux ratio (b/o) are very essential probes of the cr propagation. the energy dependence of the b/c ratio from previous balloon-borne and space-based experiments can be well described by a single power-law up to about 1 tev/n within uncertainties. this work reports direct measurements of b/c and b/o in the energy range from 10 gev/n to 5.6 tev/n with 6 years of data collected by the dark matter particle explorer, with high statistics and well controlled systematic uncertainties. the energy dependence of both the b/c and b/o ratios can be well fitted by a broken power-law model rather than a single power-law model, suggesting the existence in both flux ratios of a spectral hardening at about 100 gev/n. the significance of the break is about $5.6\sigma$ and $6.9\sigma$ for the geant4 simulation, and $4.4\sigma$ and $6.9\sigma$ for the alternative fluka simulation, for b/c and b/o, respectively. these results deviate from the predictions of conventional turbulence theories of the interstellar medium, which point toward a change of turbulence properties of the interstellar medium (ism) at different scales or novel propagation effects of crs, and should be properly incorporated in the indirect detection of dark matter via anti-matter particles. | detection of spectral hardenings in cosmic-ray boron-to-carbon and boron-to-oxygen flux ratios with dampe |
the latest icecube data suggest that the all-flavor cosmic neutrino flux may be as large as 10-7 gev cm-2 s-1 sr-1 around 30 tev. we show that, if sources of the tev-pev neutrinos are transparent to γ rays with respect to two-photon annihilation, strong tensions with the isotropic diffuse γ -ray background measured by fermi are unavoidable, independently of the production mechanism. we further show that, if the icecube neutrinos have a photohadronic (p γ ) origin, the sources are expected to be opaque to 1-100 gev γ rays. with these general multimessenger arguments, we find that the latest data suggest a population of cosmic-ray accelerators hidden in gev-tev γ rays as a neutrino origin. searches for x-ray and mev γ -ray counterparts are encouraged, and tev-pev neutrinos themselves will serve as special probes of dense source environments. | hidden cosmic-ray accelerators as an origin of tev-pev cosmic neutrinos |
we report a measurement of the energy spectrum of cosmic rays for energies above 2.5 ×1018 ev based on 215,030 events recorded with zenith angles below 60°. a key feature of the work is that the estimates of the energies are independent of assumptions about the unknown hadronic physics or of the primary mass composition. the measurement is the most precise made hitherto with the accumulated exposure being so large that the measurements of the flux are dominated by systematic uncertainties except at energies above 5 ×1019 ev . the principal conclusions are(1) the flattening of the spectrum near 5 ×1018 ev , the so-called "ankle," is confirmed. (2) the steepening of the spectrum at around 5 ×1019 ev is confirmed. (3) a new feature has been identified in the spectrum: in the region above the ankle the spectral index γ of the particle flux (∝e-γ) changes from 2.51 ±0.03 (stat ) ±0.05 (syst ) to 3.05 ±0.05 (stat ) ±0.10 (syst ) before changing sharply to 5.1 ±0.3 (stat ) ±0.1 (syst ) above 5 ×1019 ev . (4) no evidence for any dependence of the spectrum on declination has been found other than a mild excess from the southern hemisphere that is consistent with the anisotropy observed above 8 ×1018 ev . | measurement of the cosmic-ray energy spectrum above 2.5 ×1018 ev using the pierre auger observatory |
interactions of cosmic ray protons, atomic nuclei, and electrons in the interstellar medium in the inner part of the milky way produce a γ-ray flux from the galactic ridge. if the γ-ray emission is dominated by proton and nuclei interactions, a neutrino flux comparable to the γ-ray flux is expected from the same sky region. data collected by the antares neutrino telescope are used to constrain the neutrino flux from the galactic ridge in the 1-100 tev energy range. neutrino events reconstructed both as tracks and showers are considered in the analysis and the selection is optimized for the search of an excess in the region | l | < 30 °, | b | < 2 °. the expected background in the search region is estimated using an off-zone region with similar sky coverage. neutrino signal originating from a power-law spectrum with spectral index ranging from γν = 1 to 4 is simulated in both channels. the observed energy distributions are fitted to constrain the neutrino emission from the ridge. the energy distributions in the signal region are inconsistent with the background expectation at ∼ 96% confidence level. the mild excess over the background is consistent with a neutrino flux with a power law with a spectral index 2.45-0.34+0.22 and a flux normalization dnν/deν = 4.0-2.0+2.7 ×10-16 gev-1 cm-2 s-1 sr-1 at 40 tev reference energy. such flux is consistent with the expected neutrino signal if the bulk of the observed γ-ray flux from the galactic ridge originates from interactions of cosmic ray protons and nuclei with a power-law spectrum extending well into the pev energy range. | hint for a tev neutrino emission from the galactic ridge with antares |
we combine 23 hubble constant measurements based on cepheids-sn ia, trgb-sn ia, miras-sn ia, masers, tully fisher, surface brightness fluctuations, sn ii, time-delay lensing, standard sirens and γ-ray attenuation, obtaining our best optimistic h0 estimate, that is h0 = 72.94 ± 0.75 km s-1 mpc-1 at 68 per cent cl. this is in 5.9σ tension with the λcdm model, therefore we evaluate its impact on the extended dark energy cosmological models that can alleviate the tension. we find more than 4.9σ evidence for a phantom dark energy equation of state in the wcdm scenario, the cosmological constant ruled out at more than 3σ in a w0wacdm model and more than 5.7σ evidence for a coupling between dark matter and dark energy in the ide scenario. finally, we check the robustness of our results; and we quote two additional combinations of the hubble constant. the ultra-conservative estimate, h0 = 72.7 ± 1.1 km s-1 mpc-1 at 68 per cent cl, is obtained removing the cepheids-sn ia and the time-delay lensing based measurements, and confirms the evidence for new physics. | a combined analysis of the h0 late time direct measurements and the impact on the dark energy sector |
a new analysis of the data set from the pierre auger observatory provides evidence for anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate angular scale, which is indicative of excess arrivals from strong, nearby sources. the data consist of 5514 events above 20 {eev} with zenith angles up to 80° recorded before 2017 april 30. sky models have been created for two distinct populations of extragalactic gamma-ray emitters: active galactic nuclei from the second catalog of hard fermi-lat sources (2fhl) and starburst galaxies from a sample that was examined with fermi-lat. flux-limited samples, which include all types of galaxies from the swift-bat and 2mass surveys, have been investigated for comparison. the sky model of cosmic-ray density constructed using each catalog has two free parameters, the fraction of events correlating with astrophysical objects, and an angular scale characterizing the clustering of cosmic rays around extragalactic sources. a maximum-likelihood ratio test is used to evaluate the best values of these parameters and to quantify the strength of each model by contrast with isotropy. it is found that the starburst model fits the data better than the hypothesis of isotropy with a statistical significance of 4.0σ, the highest value of the test statistic being for energies above 39 {eev}. the three alternative models are favored against isotropy with 2.7σ-3.2σ significance. the origin of the indicated deviation from isotropy is examined and prospects for more sensitive future studies are discussed. any correspondence should be addressed to . | an indication of anisotropy in arrival directions of ultra-high-energy cosmic rays through comparison to the flux pattern of extragalactic gamma-ray sources |
we present new constraints on light dark matter boosted by cosmic rays (crdm) using the 205.4 kg day data of the cdex-10 experiment conducted at the china jinping underground laboratory. the monte carlo simulation package cjpl_ess was employed to evaluate the earth shielding effect. several key factors have been introduced and discussed in our crdm analysis, including the contributions from heavier cr nuclei than proton and helium, the inhomogeneity of cr distribution, and the impact of the form factor in the earth attenuation calculation. our result excludes the dark matter-nucleon elastic scattering cross section region from 1.7 ×10-30 to 10-26 cm2 for dark matter of 10 kev /c2 to 1 gev /c2 . | constraints on sub-gev dark matter boosted by cosmic rays from the cdex-10 experiment at the china jinping underground laboratory |
cosmic-ray neutron probes are widely used to monitor environmental water content near the surface. the method averages over tens of hectares and is unrivaled in serving representative data for agriculture and hydrological models at the hectometer scale. recent experiments, however, indicate that the sensor response to environmental heterogeneity is not fully understood. knowledge of the support volume is a prerequisite for the proper interpretation and validation of hydrogeophysical data. in a previous study, several physical simplifications have been introduced into a neutron transport model in order to derive the characteristics of the cosmic-ray probe's footprint. we utilize a refined source and energy spectrum for cosmic-ray neutrons and simulate their response to a variety of environmental conditions. results indicate that the method is particularly sensitive to soil moisture in the first tens of meters around the probe, whereas the radial weights are changing dynamically with ambient water. the footprint radius ranges from 130 to 240 m depending on air humidity, soil moisture, and vegetation. the moisture-dependent penetration depth of 15 to 83 cm decreases exponentially with distance to the sensor. however, the footprint circle remains almost isotropic in complex terrain with nearby rivers, roads or hill slopes. our findings suggest that a dynamically weighted average of point measurements is essential for accurate calibration and validation. the new insights will have important impact on signal interpretation, sensor installation, data interpolation from mobile surveys, and the choice of appropriate resolutions for data assimilation into hydrological models. | footprint characteristics revised for field-scale soil moisture monitoring with cosmic-ray neutrons |
the majority of the matter in the universe is still unidentified and under investigation by both direct and indirect means. many experiments searching for the recoil of dark-matter particles off target nuclei in underground laboratories have established increasingly strong constraints on the mass and scattering cross sections of weakly interacting particles, and some have even seen hints at a possible signal. other experiments search for a possible mixing of photons with light scalar or pseudo-scalar particles that could also constitute dark matter. furthermore, annihilation or decay of dark matter can contribute to charged cosmic rays, photons at all energies, and neutrinos. many existing and future ground-based and satellite experiments are sensitive to such signals. finally, data from the large hadron collider at cern are scrutinized for missing energy as a signature of new weakly interacting particles that may be related to dark matter. in this review article we summarize the status of the field with an emphasis on the complementarity between direct detection in dedicated laboratory experiments, indirect detection in the cosmic radiation, and searches at particle accelerators. | indirect and direct search for dark matter |
based on 4 yr ams-02 antiproton (\bar{p}p‾) data, we present bounds on the dark matter (dm) annihilation cross section vs. mass for some representative final state channels. we use recent cosmic-ray propagation models, a realistic treatment of experimental and theoretical errors, and an updated calculation of input \bar{p}p‾ spectra based on a recent release of the pythia code. we find that reported hints of a dm signal are statistically insignificant; an adequate treatment of errors is crucial for credible conclusions. antiproton bounds on dm annihilation are among the most stringent ones, probing thermal dm up to the tev scale. the dependence of the bounds upon propagation models and the dm halo profile is also quantified. a preliminary estimate reaches similar conclusions when applied to the 7 years ams-02 dataset, but also suggests extra caution as for possible future claims of dm excesses. | ams-02 antiprotons and dark matter: trimmed hints and robust bounds |
very recently, the xenon1t collaboration has reported an intriguing electron recoil excess, which may imply light dark matter. to interpret this anomaly, we propose the atmospheric dark matter (adm) from the inelastic collision of cosmic rays (crs) with the atmosphere. because of the boost effect of high-energy crs, we show that the light adm can be fast moving and successfully fit the observed electron recoil spectrum through the adm-electron scattering process. meanwhile, our adm predicts the scattering cross section σe∼o (10-38-10-39 cm2 ) and thus can evade other direct detection constraints. the search for light meson rare decays, such as η →π + et, would provide a complementary probe of our adm in the future. | atmospheric dark matter and xenon1t excess |
we review open questions and prospects for progress in ultrahigh-energy cosmic ray (uhecr) research, based on a series of discussions that took place during the `the high-energy universe: gamma-ray, neutrino, and cosmic-ray astronomy' miapp workshop in 2018. specifically, we overview open questions on the origin of the bulk of uhecrs, the uhecr mass composition, the origin of the end of the cosmic-ray spectrum, the transition from galactic to extragalactic cosmic rays, the effect of magnetic fields on the trajectories of uhecrs, anisotropy expectations for specific astrophysical scenarios, hadronic interactions, and prospects for discovering neutral particles as well as new physics at ultrahigh energies. we also briefly present upcoming and proposed uhecr experiments and discuss their projected science reach. | open questions in cosmic-ray research at ultrahigh energies |
we consider implications of high-energy neutrino emission from blazar flares, including the recent event icecube-170922a and the 2014-2015 neutrino flare that could originate from txs 0506+056. first, we discuss their contribution to the diffuse neutrino intensity taking into account various observational constraints. blazars are likely to be subdominant in the diffuse neutrino intensity at sub-pev energies, and we show that blazar flares like those of txs 0506+056 could make ≲1%-10% of the total neutrino intensity. we also argue that the neutrino output of blazars can be dominated by the flares in the standard leptonic scenario for their γ-ray emission, and energetic flares may still be detected with a rate of ≲ 1 {yr}}-1. second, we consider multi-messenger constraints on the source modeling. we show that luminous neutrino flares should be accompanied by luminous broadband cascade emission, emerging also in x-rays and γ-rays. this implies that not only γ-ray telescopes like fermi but also x-ray sky monitors such as swift and maxi are critical to test the canonical picture based on the single-zone modeling. we also suggest a two-zone model that can naturally satisfy the x-ray constraints while explaining the flaring neutrinos via either photomeson or hadronuclear processes. | blazar flares as an origin of high-energy cosmic neutrinos? |
we report on the observation of new properties of secondary cosmic rays li, be, and b measured in the rigidity (momentum per unit charge) range 1.9 gv to 3.3 tv with a total of 5.4 ×106 nuclei collected by ams during the first five years of operation aboard the international space station. the li and b fluxes have an identical rigidity dependence above 7 gv and all three fluxes have an identical rigidity dependence above 30 gv with the li /be flux ratio of 2.0 ±0.1 . the three fluxes deviate from a single power law above 200 gv in an identical way. this behavior of secondary cosmic rays has also been observed in the ams measurement of primary cosmic rays he, c, and o but the rigidity dependences of primary cosmic rays and of secondary cosmic rays are distinctly different. in particular, above 200 gv, the secondary cosmic rays harden more than the primary cosmic rays. | observation of new properties of secondary cosmic rays lithium, beryllium, and boron by the alpha magnetic spectrometer on the international space station |
the dark matter particle explorer (dampe), one of the four scientific space science missions within the framework of the strategic pioneer program on space science of the chinese academy of sciences, is a general purpose high energy cosmic-ray and gamma-ray observatory, which was successfully launched on december 17th, 2015 from the jiuquan satellite launch center. the dampe scientific objectives include the study of galactic cosmic rays up to ∼ 10 tev and hundreds of tev for electrons/gammas and nuclei respectively, and the search for dark matter signatures in their spectra. in this paper we illustrate the layout of the dampe instrument, and discuss the results of beam tests and calibrations performed on ground. finally we present the expected performance in space and give an overview of the mission key scientific goals. | the dark matter particle explorer mission |
a neutrino with energy ∼290 tev, icecube-170922a, was detected in coincidence with the bl lac object txs 0506+056 during enhanced gamma-ray activity, with chance coincidence being rejected at ∼3σ level. we monitored the object in the very-high-energy (vhe) band with the major atmospheric gamma-ray imaging cherenkov (magic) telescopes for ∼41 hr from 1.3 to 40.4 days after the neutrino detection. day-timescale variability is clearly resolved. we interpret the quasi-simultaneous neutrino and broadband electromagnetic observations with a novel one-zone lepto-hadronic model, based on interactions of electrons and protons co-accelerated in the jet with external photons originating from a slow-moving plasma sheath surrounding the faster jet spine. we can reproduce the multiwavelength spectra of txs 0506+056 with neutrino rate and energy compatible with icecube-170922a, and with plausible values for the jet power of ∼ {10}45-4× {10}46 {erg} {{{s}}}-1. the steep spectrum observed by magic is concordant with internal γγ absorption above ∼100 gev entailed by photohadronic production of a ∼290 tev neutrino, corroborating a genuine connection between the multi-messenger signals. in contrast to previous predictions of predominantly hadronic emission from neutrino sources, the gamma-rays can be mostly ascribed to inverse compton upscattering of external photons by accelerated electrons. the x-ray and vhe bands provide crucial constraints on the emission from both accelerated electrons and protons. we infer that the maximum energy of protons in the jet comoving frame can be in the range ∼1014 - 1018 ev. | the blazar txs 0506+056 associated with a high-energy neutrino: insights into extragalactic jets and cosmic-ray acceleration |
the origins of the high-energy cosmic neutrino flux remain largely unknown. recently, one high-energy neutrino was associated with a tidal disruption event (tde). here we present at2019fdr, an exceptionally luminous tde candidate, coincident with another high-energy neutrino. our observations, including a bright dust echo and soft late-time x-ray emission, further support a tde origin of this flare. the probability of finding two such bright events by chance is just 0.034%. we evaluate several models for neutrino production and show that at2019fdr is capable of producing the observed high-energy neutrino, reinforcing the case for tdes as neutrino sources. | candidate tidal disruption event at2019fdr coincident with a high-energy neutrino |
imaging x-ray polarimetry explorer (ixpe) is a small explorer mission by nasa and agenzia spaziale italiana, launched on 2021 december 9, dedicated to investigating x-ray polarimetry allowing angular-, time-, and energy-resolved observations in the 2-8 kev energy band. ixpe is in the science observation phase since 2022 january; it is comprised of three identical telescopes with grazing-incidence mirrors, each one having in the focal plane a gas pixel detector. in this paper, we present a possible guideline to obtain an optimal background selection in polarimetric analysis, and a rejection strategy to remove instrumental background. this work is based on the analysis of ixpe observations, aiming to improve as much as possible the polarimetric sensitivity. in particular, the developed strategies have been applied as a case study to the ixpe observation of the 4u 0142+61 magnetar. | handling the background in ixpe polarimetric data |
while active galactic nuclei with relativistic jets have long been prime candidates for the origin of extragalactic cosmic rays and neutrinos, the bl lac object txs 0506+056 is the first astrophysical source observed to be associated with some confidence (∼3σ) with a high-energy neutrino, icecube-170922a, detected by the icecube observatory. the source was found to be active in high-energy γ-rays with fermi-lat and in very-high-energy γ-rays with the magic telescopes. to consistently explain the observed neutrino and multiwavelength electromagnetic emission of txs 0506+056, we investigate in detail single-zone models of leptohadronic emission, assuming cospatial acceleration of electrons and protons in the jet, and synchrotron photons from the electrons as targets for photohadronic neutrino production. the parameter space concerning the physical conditions of the emission region and particle populations is extensively explored for scenarios where the γ-rays are dominated by either (1) proton synchrotron emission or (2) synchrotron-self-compton emission, with a subdominant but non-negligible contribution from photohadronic cascades in both cases. we find that the latter can be compatible with the neutrino observations, while the former is strongly disfavoured due to the insufficient neutrino production rate. | leptohadronic single-zone models for the electromagnetic and neutrino emission of txs 0506+056 |
the irreducible upscattering of cold dark matter by cosmic rays opens up the intriguing possibility of detecting even light dark matter in conventional direct detection experiments or underground neutrino detectors. the mechanism also significantly enhances sensitivity to models with very large nuclear scattering rates, where the atmosphere and rock overburden efficiently stop standard non-relativistic dark matter particles before they could reach the detector. in this article, we demonstrate that cosmic-ray upscattering essentially closes the window for strongly interacting dark matter in the (sub-)gev mass range. arriving at this conclusion crucially requires a detailed treatment of both nuclear form factors and inelastic dark matter-nucleus scattering, as well as including the full momentum-transfer dependence of scattering amplitudes. we illustrate the latter point by considering three generic situations where such a momentum-dependence is particularly relevant, namely for interactions dominated by the exchange of light vector or scalar mediators, respectively, and for dark matter particles of finite size. as a final concrete example, we apply our analysis to a putative hexaquark state, which has been suggested as a viable baryonic dark matter candidate. once again, we find that the updated constraints derived in this work close a significant part of otherwise unconstrained parameter space. | no room to hide: implications of cosmic-ray upscattering for gev-scale dark matter |
gas-rich dwarf galaxies located outside the virial radius of their host are relatively pristine systems and have ultralow gas cooling rates. this makes them very sensitive to heat injection by annihilation or decay of dark matter (dm). such dwarfs are particularly sensitive to dm producing e± with energies 1-100 mev or photons with energies 13.6 ev-1 kev, because these products can be efficiently thermalized in the neutral hydrogen gas of the dwarfs. following the methodology of wadekar and farrar [phys. rev. d 103, 123028 (2021), 10.1103/physrevd.103.123028], we require the rate of heat injection by dm to not exceed the ultralow radiative cooling rate of gas in the leo t dwarf galaxy. this gives model-independent bounds on (i) the decay lifetime of dm to e± (photons), which are stronger than all the previous literature for mdm∼1 - 10 mev (mdm∼0.02 - 1 kev ), (ii) annihilation of dm to e± comparable to constraints from cosmic microwave background and x /γ -ray surveys. we also translate our bounds for the case of the following dm models: axionlike particles (alps), sterile neutrinos, excited dm states, higgs portal scalars, and dark baryons. observations of gas-rich low-mass dwarfs from upcoming 21 cm and optical surveys can therefore be powerful probes of a multitude of models of dm. | strong constraints on decay and annihilation of dark matter from heating of gas-rich dwarf galaxies |
this paper focuses on the interactions between the fast solar wind from coronal holes and the intervening slower solar wind, leading to the creation of stream interaction regions that corotate with the sun and may persist for many solar rotations. stream interaction regions have been observed near 1 au, in the inner heliosphere (at ∼ 0.3-1 au) by the helios spacecraft, in the outer and distant heliosphere by the pioneer 10 and 11 and voyager 1 and 2 spacecraft, and out of the ecliptic by ulysses, and these observations are reviewed. stream interaction regions accelerate energetic particles, modulate the intensity of galactic cosmic rays and generate enhanced geomagnetic activity. the remote detection of interaction regions using interplanetary scintillation and white-light imaging, and mhd modeling of interaction regions will also be discussed. | solar wind stream interaction regions throughout the heliosphere |
the low energy x-ray telescope (le) is one of the three main instruments of the insight-hard x-ray modulation telescope (insight-hxmt). it is equipped with swept charge device (scd) sensor arrays with a total geometrical area of 384 cm and an energy band from 0.7 to 13 kev. in order to evaluate the particle induced x-ray background and the cosmic x-ray background simultaneously, le adopts collimators to define four types of field of views (fovs), i.e., 1.6°×6°, 4°×6°, 50°-60°×2°-6° and the blocked ones which block the x-ray by an aluminum cover. le is constituted of three detector boxes (leds) and an electric control box (leb) and achieves a good energy resolution of 140 ev@5.9 kev, an excellent time resolution of 0.98 ms, as well as an extremely low pileup (<1%@18000 cts/s). detailed performance tests and calibration on the ground have been performed, including energy-channel relation, energy response, detection efficiency and time response. | the low energy x-ray telescope (le) onboard the insight-hxmt astronomy satellite |
high-energy cosmic rays are observed indirectly by detecting the extensive air showers initiated in earth's atmosphere. the interpretation of these observations relies on accurate models of air shower physics, which is a challenge and an opportunity to test qcd under extreme conditions. air showers are hadronic cascades, which give rise to a muon component through hadron decays. the muon number is a key observable to infer the mass composition of cosmic rays. air shower simulations with state-of-the-art qcd models show a significant muon deficit with respect to measurements; this is called the muon puzzle. by eliminating other possibilities, we conclude that the most plausible cause for the muon discrepancy is a deviation in the composition of secondary particles produced in high-energy hadronic interactions from current model predictions. the muon discrepancy starts at the tev scale, which suggests that this deviation is observable at the large hadron collider. an enhancement of strangeness production has been observed at the lhc in high-density events, which can potentially explain the puzzle, but the impact of the effect on forward produced hadrons needs further study, in particular with future data from oxygen beam collisions. | the muon puzzle in cosmic-ray induced air showers and its connection to the large hadron collider |
light elements were produced in the first few minutes of the universe through a sequence of nuclear reactions known as big bang nucleosynthesis (bbn)1,2. among the light elements produced during bbn1,2, deuterium is an excellent indicator of cosmological parameters because its abundance is highly sensitive to the primordial baryon density and also depends on the number of neutrino species permeating the early universe. although astronomical observations of primordial deuterium abundance have reached percent accuracy3, theoretical predictions4-6 based on bbn are hampered by large uncertainties on the cross-section of the deuterium burning d(p,γ)3he reaction. here we show that our improved cross-sections of this reaction lead to bbn estimates of the baryon density at the 1.6 percent level, in excellent agreement with a recent analysis of the cosmic microwave background7. improved cross-section data were obtained by exploiting the negligible cosmic-ray background deep underground at the laboratory for underground nuclear astrophysics (luna) of the laboratori nazionali del gran sasso (italy)8,9. we bombarded a high-purity deuterium gas target10 with an intense proton beam from the luna 400-kilovolt accelerator11 and detected the γ-rays from the nuclear reaction under study with a high-purity germanium detector. our experimental results settle the most uncertain nuclear physics input to bbn calculations and substantially improve the reliability of using primordial abundances to probe the physics of the early universe. | the baryon density of the universe from an improved rate of deuterium burning |
we evaluate dark matter (dm) limits from cosmic-ray antiproton observations using the recent precise ams-02 measurements. we properly take into account cosmic-ray propagation uncertainties, fitting dm and propagation parameters at the same time and marginalizing over the latter. we find a significant indication of a dm signal for dm masses near 80 gev, with a hadronic annihilation cross section close to the thermal value, ⟨σ v ⟩ ≈3 ×10-26 cm3 s-1 . intriguingly, this signal is compatible with the dm interpretation of the galactic center gamma-ray excess. confirmation of the signal will require a more accurate study of the systematic uncertainties, i.e., the antiproton production cross section, and the modeling of the effect of solar modulation. interpreting the ams-02 data in terms of upper limits on hadronic dm annihilation, we obtain strong constraints excluding a thermal annihilation cross section for dm masses below about 50 gev and in the range between approximately 150 and 500 gev, even for conservative propagation scenarios. except for the range around ∼80 gev , our limits are a factor of ∼4 stronger than the limits from gamma-ray observations of dwarf galaxies. | novel dark matter constraints from antiprotons in light of ams-02 |
the icecube neutrino observatory was designed primarily to search for high-energy (tev-pev) neutrinos produced in distant astrophysical objects. a search for ≳100 tev neutrinos interacting inside the instrumented volume has recently provided evidence for an isotropic flux of such neutrinos. at lower energies, icecube collects large numbers of neutrinos from the weak decays of mesons in cosmic-ray air showers. here we present the results of a search for neutrino interactions inside icecube's instrumented volume between 1 tev and 1 pev in 641 days of data taken from 2010-2012, lowering the energy threshold for neutrinos from the southern sky below 10 tev for the first time, far below the threshold of the previous high-energy analysis. astrophysical neutrinos remain the dominant component in the southern sky down to a deposited energy of 10 tev. from these data we derive new constraints on the diffuse astrophysical neutrino spectrum, φν=2.0 6-0.3+0.4×1 0-18(eν/1 05 gev ) -2.46 ±0.12gev-1 cm-2 sr-1 s-1 for 25 tev <eν<1.4 pev , as well as the strongest upper limit yet on the flux of neutrinos from charmed-meson decay in the atmosphere, 1.52 times the benchmark theoretical prediction used in previous icecube results at 90% confidence. | atmospheric and astrophysical neutrinos above 1 tev interacting in icecube |
context. the hot plasma in a galaxy cluster is expected to be heated to high temperatures through shocks and adiabatic compression. the thermodynamical properties of the gas encode information on the processes leading to the thermalization of the gas in the cluster's potential well and on non-gravitational processes such as gas cooling, agn feedback, shocks, turbulence, bulk motions, cosmic rays and magnetic field.aims: in this work we present the radial profiles of the thermodynamic properties of the intracluster medium (icm) out to the virial radius for a sample of 12 galaxy clusters selected from the planck all-sky survey. we determine the universal profiles of gas density, temperature, pressure, and entropy over more than two decades in radius, from 0.01r500 to 2r500.methods: we exploited x-ray information from xmm-newton and sunyaev-zel'dovich constraints from planck to recover thermodynamic properties out to 2r500. we provide average functional forms for the radial dependence of the main quantities and quantify the slope and intrinsic scatter of the population as a function of radius.results: we find that gas density and pressure profiles steepen steadily with radius, in excellent agreement with previous observational results. entropy profiles beyond r500 closely follow the predictions for the gravitational collapse of structures. the scatter in all thermodynamical quantities reaches a minimum in the range [0.2 - 0.8]r500 and increases outward. somewhat surprisingly, we find that pressure is substantially more scattered than temperature and density.conclusions: our results indicate that once accreting substructures are properly excised, the properties of the icm beyond the cooling region (r > 0.3r500) follow remarkably well the predictions of simple gravitational collapse and require few non-gravitational corrections. | universal thermodynamic properties of the intracluster medium over two decades in radius in the x-cop sample |
the formation of the first galaxies during cosmic dawn and reionization (at redshifts z = 5-30), triggered the last major phase transition of our universe, as hydrogen evolved from cold and neutral to hot and ionized. the 21-cm line of neutral hydrogen will soon allow us to map these cosmic milestones and study the galaxies that drove them. to aid in interpreting these observations, we upgrade the publicly available code 21cmfast. we introduce a new, flexible parametrization of the additive feedback from: an inhomogeneous, h2-dissociating (lyman-werner; lw) background; and dark matter - baryon relative velocities; which recovers results from recent, small-scale hydrodynamical simulations with both effects. we perform a large, 'best-guess' simulation as the 2021 installment of the evolution of 21-cm structure (eos) project. this improves the previous release with a galaxy model that reproduces the observed uv luminosity functions (uvlfs), and by including a population of molecular-cooling galaxies. the resulting 21-cm global signal and power spectrum are significantly weaker, primarily due to a more rapid evolution of the star formation rate density required to match the uvlfs. nevertheless, we forecast high signal-to-noise detections for both hera and the ska. we demonstrate how the stellar-to-halo mass relation of the unseen, first galaxies can be inferred from the 21-cm evolution. finally, we show that the spatial modulation of x-ray heating due to relative velocities provides a unique acoustic signature that is detectable at z ≈ 10-15 in our fiducial model. ours are the first public simulations with joint inhomogeneous lw and relative-velocity feedback across the entire cosmic dawn and reionization, and we make them available at this link https://scholar.harvard.edu/julianbmunoz/eos-21. | the impact of the first galaxies on cosmic dawn and reionization |
a simple extension of the standard model consists of a scalar field that can potentially constitute the dark matter (dm). significant attention has been devoted to probing light o (≲ 10 ev) scalar dm, with a multitude of experimental proposals based on condensed matter systems as well as novel materials. however, the previously overlooked effective in-medium mixing of light scalars with longitudinal plasmons can strongly modify the original sensitivity calculations of the direct detection experiments. we implement the in-medium effects for scalar dm detection, using thermal field theory techniques, and show that the reach of a large class of direct dm detection experiments searching for light scalars is significantly reduced. this development identifies setups based on dirac materials and tunable plasma haloscopes as particularly promising for scalar dm detection. further, we also show that scalars with significant boost with respect to halo dm, such as those produced in the sun, decay of other particles or by cosmic rays, will not suffer from in-medium suppression. hence, multi-tonne direct dm detection experiments, such as those based on xenon or argon, also constitute a favorable target. we also discuss scalar mediated dm scattering. | scalar direct detection: in-medium effects |
in this letter of intent (loi) we propose the construction of mathusla (massive timing hodoscope for ultra-stable neutral particles), a dedicated large-volume displaced vertex detector for the hl-lhc on the surface above atlas or cms. such a detector, which can be built using existing technologies with a reasonable budget in time for the hl-lhc upgrade, could search for neutral long-lived particles (llps) with up to several orders of magnitude better sensitivity than atlas or cms, while also acting as a cutting-edge cosmic ray telescope at cern to explore many open questions in cosmic ray and astro-particle physics. we review the physics motivations for mathusla and summarize its llp reach for several different possible detector geometries, as well as outline the cosmic ray physics program. we present several updated background studies for mathusla, which help inform a first detector-design concept utilizing modular construction with resistive plate chambers (rpcs) as the primary tracking technology. we present first efficiency and reconstruction studies to verify the viability of this design concept, and we explore some aspects of its total cost. we end with a summary of recent progress made on the mathusla test stand, a small-scale demonstrator experiment currently taking data at cern point 1, and finish with a short comment on future work. | a letter of intent for mathusla: a dedicated displaced vertex detector above atlas or cms |
climate change increases the occurrence and severity of droughts due to increasing temperatures, altered circulation patterns, and reduced snow occurrence. while europe has suffered from drought events in the last decade unlike ever seen since the beginning of weather recordings, harmonized long-term datasets across the continent are needed to monitor change and support predictions. here we present soil moisture data from 66 cosmic-ray neutron sensors (crnss) in europe (cosmos-europe for short) covering recent drought events. the crns sites are distributed across europe and cover all major land use types and climate zones in europe. the raw neutron count data from the crns stations were provided by 24 research institutions and processed using state-of-the-art methods. the harmonized processing included correction of the raw neutron counts and a harmonized methodology for the conversion into soil moisture based on available in situ information. in addition, the uncertainty estimate is provided with the dataset, information that is particularly useful for remote sensing and modeling applications. this paper presents the current spatiotemporal coverage of crns stations in europe and describes the protocols for data processing from raw measurements to consistent soil moisture products. the data of the presented cosmos-europe network open up a manifold of potential applications for environmental research, such as remote sensing data validation, trend analysis, or model assimilation. the dataset could be of particular importance for the analysis of extreme climatic events at the continental scale. due its timely relevance in the scope of climate change in the recent years, we demonstrate this potential application with a brief analysis on the spatiotemporal soil moisture variability. the dataset, entitled "dataset of cosmos-europe: a european network of cosmic-ray neutron soil moisture sensors", is shared via forschungszentrum jülich: https://doi.org/10.34731/x9s3-kr48 (bogena and ney, 2021). | cosmos-europe: a european network of cosmic-ray neutron soil moisture sensors |
recent upper bounds from the hydrogen epoch of reionization array (hera) on the cosmological 21-cm power spectrum at redshifts $z \approx 8, 10$, have been used to constrain $l_{\rm x<2 \, kev}/{\rm sfr}$, the soft-band x-ray luminosity measured per unit star formation rate (sfr), strongly disfavoring values lower than $\approx 10^{39.5} \, {\rm erg} \;{\rm s}^{-1} \;{\rm m}_{\odot}^{-1} \;{\rm yr}$. this conclusion is derived from semi-numerical models of the 21-cm signal, specifically focusing on contributions from atomic cooling galaxies that host popii stars. in this work, we first reproduce the bounds on $l_{\rm x<2 \, kev}/{\rm sfr}$ and other parameters using a pipeline that combines machine learning emulators for the power spectra and the intergalactic medium characteristics, together with a standard markov chain monte carlo parameter fit. we then use this approach when including molecular cooling galaxies that host popiii stars in the cosmic dawn 21-cm signal, and show that lower values of $l_{\rm x<2 \, kev}/{\rm sfr}$ are hence no longer strongly disfavored. the revised hera bound does not require high-redshift x-ray sources to be significantly more luminous than high-mass x-ray binaries observed at low redshift. | hera bound on x-ray luminosity when accounting for population iii stars |
the null signal from collider and dark matter (dm) direct detector experiments makes the interaction between dm and visible matter too small to reproduce the correct relic density for many thermal dm models. the remaining parameter space indicates that two almost degenerated states in the dark sector, the inelastic dm scenario, can co-annihilate in the early universe to produce the correct relic density. regarding the direct detection of the inelastic dm scenario, the virialized dm component from the nearby halo is nonrelativistic and not able to excite the dm ground state, even if the relevant couplings can be considerable. thus, a dm with a large mass splitting can evade traditional virialized dm direct detection. in this study, we connect the concept of cosmic-ray accelerated dm in our milky way and the direct detection of inelastic scattering in underground detectors to explore spectra that result from several interaction types of the inelastic dm. we find that the mass splitting δ <o (1 gev ) can still be reachable for cosmic ray accelerated dm with mass range 1 mev <mχ 1< 100 gev and sub-gev light mediator using the latest pandax-4t data, even though we conservatively use the astrophysical parameter (effective length) deff = 1 kpc. | revising inelastic dark matter direct detection by including the cosmic ray acceleration |
a precision measurement of the nitrogen flux with rigidity (momentum per unit charge) from 2.2 gv to 3.3 tv based on 2.2 ×106 events is presented. the detailed rigidity dependence of the nitrogen flux spectral index is presented for the first time. the spectral index rapidly hardens at high rigidities and becomes identical to the spectral indices of primary he, c, and o cosmic rays above ∼700 gv . we observed that the nitrogen flux φn can be presented as the sum of its primary component φnp and secondary component φns, φn=φnp+φns, and we found φn is well described by the weighted sum of the oxygen flux φo (primary cosmic rays) and the boron flux φb (secondary cosmic rays), with φnp=(0.090 ±0.002 )×φo and φns=(0.62 ±0.02 )×φb over the entire rigidity range. this corresponds to a change of the contribution of the secondary cosmic ray component in the nitrogen flux from 70% at a few gv to <30 % above 1 tv. | precision measurement of cosmic-ray nitrogen and its primary and secondary components with the alpha magnetic spectrometer on the international space station |
limits on gravitational čerenkov radiation by cosmic rays are obtained and used to constrain coefficients for lorentz violation in the gravity sector associated with operators of even mass dimensions, including orientation-dependent effects. we use existing data from cosmic-ray telescopes to obtain conservative two-sided constraints on 80 distinct lorentz-violating operators of dimensions four, six, and eight, along with conservative one-sided constraints on three others. existing limits on the nine minimal operators at dimension four are improved by factors of up to a billion, while 74 of our explicit limits represent stringent first constraints on nonminimal operators. prospects are discussed for future analyses incorporating effects of lorentz violation in the matter sector, the role of gravitational čerenkov radiation by high-energy photons, data from gravitational-wave observatories, the tired-light effect, and electromagnetic čerenkov radiation by gravitons. | constraints on lorentz violation from gravitational čerenkov radiation |
we present high-statistics, precision measurements of the detailed time and energy dependence of the primary cosmic-ray electron flux and positron flux over 79 bartels rotations from may 2011 to may 2017 in the energy range from 1 to 50 gev. for the first time, the charge-sign dependent modulation during solar maximum has been investigated in detail by leptons alone. based on 23.5 ×106 events, we report the observation of short-term structures on the timescale of months coincident in both the electron flux and the positron flux. these structures are not visible in the e+/e- flux ratio. the precision measurements across the solar polarity reversal show that the ratio exhibits a smooth transition over 830 ±30 days from one value to another. the midpoint of the transition shows an energy dependent delay relative to the reversal and changes by 260 ±30 days from 1 to 6 gev. | observation of complex time structures in the cosmic-ray electron and positron fluxes with the alpha magnetic spectrometer on the international space station |
we present the implementation and the first results of cosmic ray (cr) feedback in the feedback in realistic environments (fire) simulations. we investigate cr feedback in non-cosmological simulations of dwarf, sub-l⋆ starburst, and l⋆ galaxies with different propagation models, including advection, isotropic, and anisotropic diffusion, and streaming along field lines with different transport coefficients. we simulate cr diffusion and streaming simultaneously in galaxies with high resolution, using a two-moment method. we forward-model and compare to observations of γ-ray emission from nearby and starburst galaxies. we reproduce the γ-ray observations of dwarf and l⋆ galaxies with constant isotropic diffusion coefficient κ ∼ 3× 10^{29} cm^{2 s^{-1}}. advection-only and streaming-only models produce order of magnitude too large γ-ray luminosities in dwarf and l⋆ galaxies. we show that in models that match the γ-ray observations, most crs escape low-gas-density galaxies (e.g. dwarfs) before significant collisional losses, while starburst galaxies are cr proton calorimeters. while adiabatic losses can be significant, they occur only after crs escape galaxies, so they are only of secondary importance for γ-ray emissivities. models where crs are `trapped' in the star-forming disc have lower star formation efficiency, but these models are ruled out by γ-ray observations. for models with constant κ that match the γ-ray observations, crs form extended haloes with scale heights of several kpc to several tens of kpc. | cosmic ray feedback in the fire simulations: constraining cosmic ray propagation with gev γ-ray emission |
we present the first measurement of the fluctuations in the number of muons in extensive air showers produced by ultrahigh energy cosmic rays. we find that the measured fluctuations are in good agreement with predictions from air shower simulations. this observation provides new insights into the origin of the previously reported deficit of muons in air shower simulations and constrains models of hadronic interactions at ultrahigh energies. our measurement is compatible with the muon deficit originating from small deviations in the predictions from hadronic interaction models of particle production that accumulate as the showers develop. | measurement of the fluctuations in the number of muons in extensive air showers with the pierre auger observatory |
cosmic-ray astrophysics has advanced rapidly in recent years, and its impact on other astronomical disciplines has broadened. many new experiments measuring these particles, both directly in the atmosphere or space and indirectly via î³ rays and synchrotron radiation, have widened the range and quality of the information available on their origin, propagation, and interactions. the impact of low-energy cosmic rays on interstellar chemistry is a fast-developing topic, including the propagation of these particles into the clouds in which the chemistry occurs. cosmic rays, via their î³-ray production, also provide a powerful way to probe the gas content of the interstellar medium. substantial advances have been made in the observations and modelling of the interplay between cosmic rays and the interstellar medium. focusing on energies up to 1 tev, these interrelating aspects are covered at various levels of detail, giving a guide to the state of the subject. | the nine lives of cosmic rays in galaxies |
the early star-forming universe is still poorly constrained, with the properties of high-redshift stars, the first heating sources and reionization highly uncertain. this leaves observers planning 21-cm experiments with little theoretical guidance. in this work, we explore the possible range of high-redshift parameters including the star formation efficiency and the minimal mass of star-forming haloes; the efficiency, spectral energy distribution and redshift evolution of the first x-ray sources; and the history of reionization. these parameters are only weakly constrained by available observations, mainly the optical depth to the cosmic microwave background. we use realistic semi-numerical simulations to produce the global 21-cm signal over the redshift range z = 6-40 for each of 193 different combinations of the astrophysical parameters spanning the allowed range. we show that the expected signal fills a large parameter space, but with a fixed general shape for the global 21-cm curve. even with our wide selection of models, we still find clear correlations between the key features of the global 21-cm signal and underlying astrophysical properties of the high-redshift universe, namely the ly α intensity, the x-ray heating rate and the production rate of ionizing photons. these correlations can be used to directly link future measurements of the global 21-cm signal to astrophysical quantities in a mostly model-independent way. we identify additional correlations that can be used as consistency checks. | charting the parameter space of the global 21-cm signal |
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