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we show that coupling of ultralight dark matter (udm) to quarks and gluons would lead to an oscillation of the nuclear charge radius for both the quantum chromodynamics (qcd) axion and scalar dark matter. consequently, the resulting oscillation of electronic energy levels could be resolved with optical atomic clocks, and their comparisons can be used to investigate udm-nuclear couplings, which were previously only accessible with other platforms. we demonstrate this idea using the ${}^2s_{1/2} (f=0)\leftrightarrow {}^2f_{7/2} (f=3)$ electric octupole and ${}^2s_{1/2} (f=0)\leftrightarrow \,{}^2d_{3/2} (f=2)$ electric quadrupole transitions in ${}^{171}yb^+$. based on the derived sensitivity coefficients for these two transitions and a long-term comparison of their frequencies using a single trapped ${}^{171}yb^+$ ion, we find bounds on the scalar udm-nuclear couplings and the qcd axion decay constant. these results are at a similar level compared to the tightest spectroscopic limits, and future investigations, also with other optical clocks, promise significant improvements. | oscillating nuclear charge radii as sensors for ultralight dark matter |
we consider the possibility of an enlarged qcd color group, su (3 +n') spontaneously broken to su (3 )c×su (n') with extra vectorlike quarks transforming in the fundamental representation. when the heavy quarks are integrated out below the pq-breaking scale, they generate an axion coupling which simultaneously solves the strong c p problem for both gauge groups. however, the axion mass now receives a new nonperturbative contribution from the su (n') confinement scale, which can be substantially larger than the qcd scale. this can increase the axion mass to be at or above the electroweak scale. this visible axion can then decay into gluons and photons giving rise to observable signals at run ii of the lhc. in particular, if the mass is identified with the 750 gev diphoton resonance, then the new confinement scale is ∼tev and the pq-breaking scale is ∼10 tev . this predicts vectorlike quarks and a pq scalar resonance in the multi-tev range, with the possibility that dark matter is an su (n') baryon. | a visible qcd axion from an enlarged color group |
we point out that the physics at the extreme ir — cosmology — might provide tests of the physics of the extreme uv — the weak gravity conjecture. the current discrepancies in the determination of h0 may hint at a modification of λcdm. an extension which may fit better comprises an early contribution to dark energy which “decays” into relativistic matter. on the other hand, the discourse on wgc to date suggests that fields which support cosmic acceleration may produce relativistic matter after they traverse a ∼ planckian distance in field space. we explain how this offers a simple realization of the requisite cosmic phenomenology. thus, if the resolution of h0 discrepancies is really early dark energy that ends with a shower of relativistic matter and the current ideas on wgc are indicative, this may be a rare opportunity to link the two extreme limits of quantum field theory. | dark energy, h0 and weak gravity conjecture |
understanding ultracold collisions involving molecules is of fundamental importance for current experiments, where inelastic collisions typically limit the lifetime of molecular ensembles in optical traps. here we present a broad study of optically trapped ultracold rbcs molecules in collisions with one another, in reactive collisions with rb atoms, and in nonreactive collisions with cs atoms. for experiments with rbcs alone, we show that by modulating the intensity of the optical trap, such that the molecules spend 75% of each modulation cycle in the dark, we partially suppress collisional loss of the molecules. this is evidence for optical excitation of molecule pairs mediated via sticky collisions. we find that the suppression is less effective for molecules not prepared in the spin-stretched hyperfine ground state. this may be due either to longer lifetimes for complexes in the dark or to laser-free decay pathways. for atom-molecule mixtures, rbcs + rb and rbcs + cs, we demonstrate that the rate of collisional loss of molecules scales linearly with the density of atoms. this indicates that, in both cases, the loss of molecules is rate-limited by two-body atom-molecule processes. for both mixtures, we measure loss rates that are below the thermally averaged universal limit. | molecule-molecule and atom-molecule collisions with ultracold rbcs molecules |
the ultrafast nonradiative relaxation of a molecular ensemble coupled to a cavity mode is considered theoretically and by real-time quantum dynamics. for equal coupling strength of single molecules to the cavity mode, the nonradiative relaxation rate from the upper to the lower polariton states is found to strongly depend on the number of coupled molecules. the coupling of both bright and dark polaritonic states among each other constitutes a special case of (pseudo-)jahn-teller interactions involving collective displacements the internal coordinates of the molecules in the ensemble, and the strength of the first order vibronic coupling depends exclusively on the gradient of the energy gaps between molecular electronic states. for n >2 molecules, the n -1 dark light-matter states between the two optically active polaritons feature true collective conical intersection crossings, whose location depends on the internal atomic coordinates of each molecule in the ensemble, and which contribute to the ultrafast nonradiative decay from the upper polariton. | collective jahn-teller interactions through light-matter coupling in a cavity |
there exist non-trivial stationary points of the euclidean action for an axion particle minimally coupled to einstein gravity, dubbed wormholes. they explicitly break the continuos global shift symmetry of the axion in a non-perturbative way, and generate an effective potential that may compete with qcd depending on the value of the axion decay constant. in this paper, we explore both theoretical and phenomenological aspects of this issue. on the theory side, we address the problem of stability of the wormhole solutions, and we show that the spectrum of the quadratic action features only positive eigenvalues. on the phenomenological side, we discuss, beside the obvious application to the qcd axion, relevant consequences for models with ultralight dark matter and black hole superradiance. we conclude discussing wormhole solutions for a generic coset and the potential they generate. | wormholes and masses for goldstone bosons |
we report on a direct search for sub-gev dark photons (a') which might be produced in the reaction e^- z \to e^- z a' via kinetic mixing with photons by 100 gev electrons incident on an active target in the na64 experiment at the cern sps. the a's would decay invisibly into dark matter particles resulting in events with large missing energy. no evidence for such decays was found with 2.75\cdot 10^{9} electrons on target. we set new limits on the \gamma-a' mixing strength and exclude the invisible a' with a mass < 100 mev as an explanation of the muon g_\mu-2 anomaly. | search for invisible decays of sub-gev dark photons in missing-energy events at the cern sps |
the extension of standard model made by inclusion of additional u (1 ) gauge lμ-lτ symmetry can explain the difference between the measured and the predicted value of the muon magnetic moment and solve the tension in b meson decays. this model predicts the existence of a new, light z' vector boson, predominantly coupled to second and third generation leptons, whose interaction with electrons is due to a loop mechanism involving muons and taus. in this work, we present a rigorous evaluation of the upper limits in the z' parameter space, obtained from the analysis of the data collected by the na64-e experiment at cern sps, that performed a search for light dark matter with 2.84 ×1011 electrons impinging with 100 gev on an active thick target. the resulting limits touch the muon g -2 preferred band for values of the z' mass of order of 1 mev, while the sensitivity projections for the future high-statistics na64-e runs demonstrate the power of the electrons/positron beam approach in this theoretical scenario. | search for a light z' in the lμ-lτ scenario with the na64-e experiment at cern |
we consider the production of dark matter during the process of reheating after inflation. the relic density of dark matter from freeze-in depends on both the energy density and energy distribution of the inflaton scattering or decay products composing the radiation bath. we compare the perturbative and non-perturbative calculations of the energy density in radiation. we also consider the (likely) possibility that the final state scalar products are unstable. assuming either thermal or non-thermal energy distribution functions, we compare the resulting relic density based on these different approaches. we show that the present-day cold dark matter density can be obtained through freeze-in from preheating for a large range of dark matter masses. | freeze-in from preheating |
we present the gambit modules specbit, decaybit and precisionbit. together they provide a new framework for linking publicly available spectrum generators, decay codes and other precision observable calculations in a physically and statistically consistent manner. this allows users to automatically run various combinations of existing codes as if they are a single package. the modular design allows software packages fulfilling the same role to be exchanged freely at runtime, with the results presented in a common format that can easily be passed to downstream dark matter, collider and flavour codes. these modules constitute an essential part of the broader gambit framework, a major new software package for performing global fits. in this paper we present the observable calculations, data, and likelihood functions implemented in the three modules, as well as the conventions and assumptions used in interfacing them with external codes. we also present 3-bit-hit, a command-line utility for computing mass spectra, couplings, decays and precision observables in the mssm, which shows how the three modules can easily be used independently of gambit. | specbit, decaybit and precisionbit: gambit modules for computing mass spectra, particle decay rates and precision observables |
even after decades of research, the problem of first passage time statistics for quantum dynamics remains a challenging topic of fundamental and practical importance. using a projective measurement approach, with a sampling time τ , we obtain the statistics of first detection events for quantum dynamics on a lattice, with the detector located at the origin. a quantum renewal equation for a first detection wave function, in terms of which the first detection probability can be calculated, is derived. this formula gives the relation between first detection statistics and the solution of the corresponding schrödinger equation in the absence of measurement. we illustrate our results with tight-binding quantum walk models. we examine a closed system, i.e., a ring, and reveal the intricate influence of the sampling time τ on the statistics of detection, discussing the quantum zeno effect, half dark states, revivals, and optimal detection. the initial condition modifies the statistics of a quantum walk on a finite ring in surprising ways. in some cases, the average detection time is independent of the sampling time while in others the average exhibits multiple divergences as the sampling time is modified. for an unbounded one-dimensional quantum walk, the probability of first detection decays like (time)(-3 ) with superimposed oscillations, with exceptional behavior when the sampling period τ times the tunneling rate γ is a multiple of π /2 . the amplitude of the power-law decay is suppressed as τ →0 due to the zeno effect. our work, an extended version of our previously published paper, predicts rich physical behaviors compared with classical brownian motion, for which the first passage probability density decays monotonically like (time)-3 /2, as elucidated by schrödinger in 1915. | quantum walks: the first detected passage time problem |
we discuss the 750 gev diphoton excess at the lhc@13tev in the framework of leptophobic u(1)' model inspired by e 6 grand unified theory (gut). in this model, the standard model (sm) chiral fermions carry charges under extra u(1)' gauge symmetry which is spontaneously broken by a u(1)'-charged singlet scalar (φ). in addition, extra quarks and leptons are introduced to achieve the anomaly-free conditions, which is a natural consequence of the assumed e 6 gut. these new fermions are vectorlike under the sm gauge group but chiral under new u(1)', and their masses come entirely from the nonzero vacuum expectation value of φ through the yukawa interactions. then, the cp-even scalar h φ from φ can be produced at the lhc by the gluon fusion and decay to the diphoton via the one-loop diagram involving the extra quarks and leptons, and can be identified as the origin of diphoton excess at 750 gev. in this model, h φ can decay into a pair of dark matter particles as well as a pair of scalar bosons, thereby a few tens of the decay width may be possible. | diphoton excess at 750 gev in leptophobic u(1)' model inspired by e 6 gut |
dark matter, x, may be generated by new physics at the tev scale during an early matter-dominated (md) era that ends at temperature tr ≪ tev. compared to the conventional radiation-dominated (rd) results, yields from both freeze-out and freeze-in processes are greatly suppressed by dilution from entropy production, making freeze-out less plausible while allowing successful freeze-in with a much larger coupling strength. freeze-in is typically dominated by the decay of a particle b of the thermal bath, b → x. for a large fraction of the relevant cosmological parameter space, the decay rate required to produce the observed dark matter abundance leads to displaced signals at lhc and future colliders, for any mx in the range kev < mx < mb and for values of mb accessible to these colliders. this result applies whether the early md era arises after conventional inflation, when tr is the usual reheat temperature, or is a generic md era with an alternative origin. in the former case, if mx is sufficiently large to be measured from kinematics, the reheat temperature tr can be extracted. our result is independent of the particular particle physics implementation of b → x, and can occur via any operator of dimension less than 8 (4) for a post-inflation (general md) cosmology. an interesting example is provided by dfs axion theories with tev-scale supersymmetry and axino dark matter of mass gev to tev, which is typically overproduced in a conventional rd cosmology. if b is the higgsino, h̃, higgs, w and z particles appear at the displaced decays, h̃ → h̃ a, z ã and h̃± → w± ã. the scale of axion physics, f, is predicted to be in the range (3×108-1012) gev and, over much of this range, can be extracted from the decay length. | freeze-in dark matter with displaced signatures at colliders |
we analyze in detail the lhc prospects at the center-of-mass enery of √{s} = 14 tev for charged electroweakino searches, decaying to leptons, in compressed supersymmetry scenarios, via exclusive photon-initiated pair production. this provides a potentially increased sensitivity in comparison to inclusive channels, where the background is often overwhelming. we pay particular attention to the challenges that such searches would face in the hostile high pile-up environment of the lhc, giving close consideration to the backgrounds that will be present. the signal we focus on is the exclusive production of same-flavour muon and electron pairs, with missing energy in the final state, and with two outgoing intact protons registered by the dedicated forward proton detectors installed in association with atlas and cms. we present results for slepton masses of 120-300 gev and slepton-neutralino mass splitting of 10-20 gev, and find that the relevant backgrounds can be controlled to the level of the expected signal yields. the most significant such backgrounds are due to semi-exclusive lepton pair production at lower masses, with a proton produced in the initial proton dissociation system registering in the forward detectors, and from the coincidence of forward protons produced in pile-up events with an inclusive central event that mimics the signal. we also outline a range of potential methods to further suppress these backgrounds as well as to enlarge the signal yields. | lhc searches for dark matter in compressed mass scenarios: challenges in the forward proton mode |
we show that the excess events observed in a number of recent lhc resonance searches can be simultaneously explained within a nonsupersymmetric left-right inverse seesaw model for neutrino masses with wr mass around 1.9 tev. the minimal particle content that leads to gauge coupling unification in this model predicts gr≃0.51 at the tev scale, which is consistent with data. the extra color singlet, s u (2 )-triplet fermions required for unification can be interpreted as the dark matter of the universe. future measurements of the ratio of same-sign to opposite-sign dilepton events can provide a way to distinguish this scenario from the canonical cases of type-i and inverse seesaw, i.e., provide a measure of the relative magnitudes of the dirac and majorana masses of the right-handed neutrinos in the s u (2 )r doublet of the left-right symmetric model. | unified explanation of the e e j j , diboson, and dijet resonances at the lhc |
in vibrational strong coupling (vsc), molecular vibrations strongly interact with the modes of an optical cavity to form hybrid light-matter states known as vibrational polaritons. experiments show that the kinetics of thermally activated chemical reactions can be modified by vsc. transition-state theory, which assumes that internal thermalization is fast compared to reactive transitions, has been unable to explain the observed findings. here, we carry out kinetic simulations to understand how dissipative processes, namely, those introduced by vsc to the chemical system, affect reactions where internal thermalization and reactive transitions occur on similar timescales. using the marcus-levich-jortner type of electron transfer as a model reaction, we show that such dissipation can change reactivity by accelerating internal thermalization, thereby suppressing nonequilibrium effects that occur in the reaction outside the cavity. this phenomenon is attributed mainly to cavity decay (i.e., photon leakage), but a supporting role is played by the relaxation between polaritons and dark states. when nonequilibrium effects are already suppressed in the bare reaction (the reactive species are essentially at internal thermal equilibrium throughout the reaction), we find that reactivity does not change significantly under vsc. connections are made between our results and experimental observations. | nonequilibrium effects of cavity leakage and vibrational dissipation in thermally activated polariton chemistry |
we assess the impact of searches at flavor factories for new neutral resonances that couple to both photons and gluons. these are well motivated by "heavy axion" solutions of the strong cp problem and by frameworks addressing both dark matter and the higgs hierarchy problem. we use lhcb public diphoton data around the bs mass to derive the current best limit on these resonances for masses between 4.9 and 6.3 gev. we estimate that a future lhcb dedicated search would test an axion decay constant of o(tev) for axion masses in the few-to-tens of gev, being fully complementary to the low mass atlas and cms searches. we also derive the impact of babar searches based on upsilon decays and the future belle-ii reach. | new axion searches at flavor factories |
we investigate cosmological structure formation in fuzzy dark matter (fdm) with the attractive self-interaction (si) with numerical simulations. such a si would arise if the fdm boson were an ultra-light axion, which has a strong cp symmetry-breaking scale (decay constant). although weak, the attractive si may be strong enough to counteract the quantum 'pressure' and alter structure formation. we find in our simulations that the si can enhance small-scale structure formation, and soliton cores above a critical mass undergo a phase transition, transforming from dilute to dense solitons. | cosmological structure formation and soliton phase transition in fuzzy dark matter with axion self-interactions |
we perform frequentist and bayesian statistical analyses of higgs- and z -portal models of dark matter particles with spin 0, 1 /2 , and 1. our analyses incorporate data from direct detection and indirect detection experiments, as well as lhc searches for monojet and monophoton events, and we also analyze the potential impacts of future direct detection experiments. we find acceptable regions of the parameter spaces for higgs-portal models with real scalar, neutral vector, majorana, or dirac fermion dark matter particles, and z -portal models with majorana or dirac fermion dark matter particles. in many of these cases, there are interesting prospects for discovering dark matter particles in higgs or z decays, as well as dark matter particles weighing ≳100 gev . negative results from planned direct detection experiments would still allow acceptable regions for higgs- and z -portal models with majorana or dirac fermion dark matter particles. | statistical analyses of higgs- and z -portal dark matter models |
we introduce the gambit universal model machine (gum), a tool for automatically generating code for the global fitting software framework gambit, based on lagrangian-level inputs. gum accepts models written symbolically in feynrules and sarah formats, and can use either tool along with madgraph and calchep to generate gambit model, collider, dark matter, decay and spectrum code, as well as gambit interfaces to corresponding versions of spheno, micromegas, pythia and vevacious (c ). in this paper we describe the features, methods, usage, pathways, assumptions and current limitations of gum. we also give a fully worked example, consisting of the addition of a majorana fermion simplified dark matter model with a scalar mediator to gambit via gum, and carry out a corresponding fit. | the gambit universal model machine: from lagrangians to likelihoods |
an only early or only late time alteration to λ cdm has been inadequate at resolving both the h0 and s8 tensions simultaneously; however, a combination of early and late time alterations to λ cdm can provide a solution to both tensions. as an illustration, we examine a combined early dark energy, decaying dark matter model. while early dark energy has the ability to resolve the h0 tension, it leads to a discrepancy in s8 measurements. we show that the addition of decaying dark matter helps resolve the s8 discrepancy that would otherwise be enhanced in an early dark energy model, while the latter is able to relieve the h0 disagreement to within the 95th percentile interval. our results show a preference for the combined model over λ cdm with δ aic =-6.72 , hinting that both early and late universe modifications may be necessary to address the cosmological tensions. | h0 and s8 tensions necessitate early and late time changes to λ cdm |
we have studied three realistic benchmark geometries for a new far detector gazelle to search for long-lived particles at the \superkekb accelerator in tsukuba, japan. the new detector would be housed in the same building as belle ii and observe the same $e^+e^-$ collisions. to assess the discovery reach of gazelle, we have investigated three new physics models that predict long-lived particles: heavy neutral leptons produced in tau lepton decays, axion-like particles produced in $b$ meson decays, and new scalars produced in association with a dark photon, as motivated by inelastic dark matter. we do not find significant gains in the new physics discovery reach of gazelle compared to the belle ii projections for the same final states. the main reasons are the practical limitations on the angular acceptance and size of gazelle, effectively making it at most comparable to belle ii, even though backgrounds in the far detector could be reduced to low rates. a far detector for long-lived particles would be well motivated in the case of a discovery by belle ii, since decays inside gazelle would facilitate studies of the decay products. depending on the placement of gazelle, searches for light long-lived particles produced in the forward direction or signals of a confining hidden force could also benefit from such a far detector. our general findings could help guide the design of far detectors at future electron-positron colliders such as the ilc, fcc-ee or cepc. | physics reach of a long-lived particle detector at belle ii |
we perform a theoretical study of radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers. this decay necessarily involves an electronic spin flip. the intrinsic decay mechanism due to interband spin-flip dipole moment perpendicular to the monolayer plane, gives a rate about 100-1000 times smaller than that of bright excitons. however, we find that this mechanism also introduces an energy splitting due to a local field effect, and the whole oscillator strength is contained in the higher-energy component, while the lowest-energy state remains dark and needs an extrinsic spin-flip mechanism for the decay. rashba effect due to a perpendicular electric field or a dielectric substrate, gives a negligible radiative decay rate (about 107 times slower than that of bright excitons). spin flip due to zeeman effect in a sufficiently strong in-plane magnetic field can give a decay rate comparable to that due to the intrinsic interband spin-flip dipole. | spin-flip processes and radiative decay of dark intravalley excitons in transition metal dichalcogenide monolayers |
a search is presented for an excess of events with large missing transverse momentum in association with at least one highly energetic jet, in a data sample of proton-proton collisions at a centre-of-mass energy of 8 tev. the data correspond to an integrated luminosity of 19.7 fb-1 collected by the cms experiment at the lhc. the results are interpreted using a set of simplified models for the production of dark matter via a scalar, pseudoscalar, vector, or axial vector mediator. additional sensitivity is achieved by tagging events consistent with the jets originating from a hadronically decaying vector boson. this search uses jet substructure techniques to identify hadronically decaying vector bosons in both lorentz-boosted and resolved scenarios. this analysis yields improvements of 80% in terms of excluded signal cross sections with respect to the previous cms analysis using the same data set. no significant excess with respect to the standard model expectation is observed and limits are placed on the parameter space of the simplified models. mediator masses between 80 and 400 gev in the scalar and pseudoscalar models, and up to 1.5 tev in the vector and axial vector models, are excluded. [figure not available: see fulltext.] | search for dark matter in proton-proton collisions at 8 tev with missing transverse momentum and vector boson tagged jets |
axion cold dark matter from standard misalignment typically requires a decay constant fa gtrsim 1011 gev . kinetic misalignment and parametric resonance easily allow lower values of fa when the radial peccei-quinn (pq) symmetry breaking field takes large initial values. here, we consider the effects of inflation on kinetic misalignment and parametric resonance. we assume that the initial pq field value is determined by quantum fluctuations, and is set by the hubble parameter during inflation, hi, and the pq field mass. pq field oscillations begin before or after the completion of reheating after inflation at a temperature tr. we determine the range of fa and the inflationary parameters (hi, tr) consistent with axion dark matter for a quartic potential for the pq field. we find that 108 gev < fa < 1011 gev can consistently produce axion dark matter. a significant portion of the allowed parameter space predicts rare kaon decays, kl → (π0 + missing energy), and/or suppression of structure formation on small scales. | axion kinetic misalignment and parametric resonance from inflation |
a search for new physics is presented in final states with two oppositely charged leptons (electrons or muons), jets identified as originating from b quarks, and missing transverse momentum ($p_\mathrm{t}^\text{miss}$). the search uses proton-proton collision data at $\sqrt{s}=$ 13 tev amounting to 35.9 fb$^{-1}$ of integrated luminosity collected using the cms detector in 2016. hypothetical signal events are efficiently separated from the dominant $\mathrm{t}\overline{\mathrm{t}}$ background with requirements on $p_\mathrm{t}^\text{miss}$ and transverse mass variables. no significant deviation is observed from the expected background. exclusion limits are set in the context of simplified supersymmetric models with pair-produced top squarks. for top squarks, decaying exclusively to a top quark and a neutralino, exclusion limits are placed at 95% confidence level on the mass of the lightest top squark up to 800 gev and on the lightest neutralino up to 360 gev. these results, combined with searches in the single-lepton and all-jet final states, raise the exclusion limits up to 1050 gev for the lightest top squark and up to 500 gev for the lightest neutralino. for top squarks undergoing a cascade decay through charginos and sleptons, the mass limits reach up to 1300 gev for top squarks and up to 800 gev for the lightest neutralino. the results are also interpreted in a simplified model with a dark matter (dm) particle coupled to the top quark through a scalar or pseudoscalar mediator. for light dm, mediator masses up to 100 (50) gev are excluded for scalar (pseudoscalar) mediators. the result for the scalar mediator achieves some of the most stringent limits to date in this model. | search for top squarks and dark matter particles in opposite-charge dilepton final states at $\\sqrt{s}=$ 13 tev |
in monolayers of semiconducting transition metal dichalcogenides, the light helicity (σ+ or σ-) is locked to the valley degree of freedom, leading to the possibility of optical initialization of distinct valley populations. however, an extremely rapid valley pseudospin relaxation (at the time scale of picoseconds) occurring for optically bright (electric-dipole active) excitons imposes some limitations on the development of opto-valleytronics. here, we show that valley pseudospin relaxation of excitons can be significantly suppressed in a wse2 monolayer, a direct-gap two-dimensional semiconductor with the exciton ground state being optically dark. we demonstrate that the already inefficient relaxation of the exciton pseudospin in such a system can be suppressed even further by the application of a tiny magnetic field of about 100 mt. time-resolved spectroscopy reveals the pseudospin dynamics to be a two-step relaxation process. an initial decay of the pseudospin occurs at the level of dark excitons on a time scale of 100 ps, which is tunable with a magnetic field. this decay is followed by even longer decay (>1 ns ), once the dark excitons form more complex pseudo-particles allowing for their radiative recombination. our findings of slow valley pseudospin relaxation easily manipulated by the magnetic field open new prospects for engineering the dynamics of the valley pseudospin in transition metal dichalcogenides. | tuning valley polarization in a wse2 monolayer with a tiny magnetic field |
the formation and decay of metastable bound states can significantly decrease the thermal-relic dark matter density, particularly for dark matter masses around and above the tev scale. incorporating bound-state effects in the dark matter thermal decoupling requires in principle a set of coupled boltzmann equations for the bound and unbound species. however, decaying bound states attain and remain in a quasi-steady state. here we prove in generality that this reduces the coupled system into a single boltzmann equation of the standard form, with an effective cross-section that describes the interplay among bound-state formation, ionisation, transitions and decays. we derive a closed-form expression for the effective cross-section for an arbitrary number of bound states, and show that bound-to-bound transitions can only increase it. excited bound levels may thus decrease the dark matter density more significantly than otherwise estimated. our results generalise the saha ionisation equilibrium to metastable bound states, potentially with applications beyond the dark matter thermal decoupling. | saha equilibrium for metastable bound states and dark matter freeze-out |
excitation of ionic solids with extreme ultraviolet pulses creates localized core-level excitons, which in some cases couple strongly to the lattice. here, core-level-exciton states of magnesium oxide are studied in the time domain at the mg l2 ,3 edge with attosecond transient reflectivity spectroscopy. attosecond pulses trigger the excitation of these short-lived quasiparticles, whose decay is perturbed by time-delayed near-infrared pulses. combined with a few-state theoretical model, this reveals that the infrared pulse shifts the energy of bright (dipole-allowed) core-level-exciton states as well as induces features arising from dark core-level excitons. we report coherence lifetimes for the two lowest core-level excitons of 2.3 ±0.2 and 1.6 ±0.5 fs and show that these are primarily a consequence of strong exciton-phonon coupling, disclosing the drastic influence of structural effects in this ultrafast relaxation process. | attosecond time-domain measurement of core-level-exciton decay in magnesium oxide |
we investigate the quenching of the photoluminescence (pl) from the divacancy defect in 4 h -sic consisting of a nearest-neighbor silicon and carbon vacancies. the quenching occurs only when the pl is excited below certain photon energies (thresholds), which differ for the four different inequivalent divacancy configurations in 4 h -sic. an accurate theoretical ab initio calculation for the charge-transfer levels of the divacancy shows very good agreement between the position of the (0/-) level with respect to the conduction band for each divacancy configuration and the corresponding experimentally observed threshold, allowing us to associate the pl decay with conversion of the divacancy from neutral to negative charge state due to capture of electrons photoionized from other defects (traps) by the excitation. electron paramagnetic resonance measurements are conducted in the dark and under excitation similar to that used in the pl experiments and shed light on the possible origin of traps in the different samples. a simple model built on this concept agrees well with the experimentally observed decay curves. | excitation properties of the divacancy in 4 h -sic |
we explore the possibility that the recently reported diphoton excess at atlas and cms can be accommodated within a minimal extension of a left-right symmetric model. our setup is able to simultaneously explain the run 2 diphoton and run 1 diboson excesses, while providing a standard thermal freeze-out of weak-scale dark matter. in this scenario, the 750 gev neutral right-handed higgs triplet is responsible for the diphoton excess. interactions of this state with the neutral and charged components of dark matter multiplets provide the dominant mechanisms for production and decay. a striking signature of this model is the additional presence of missing energy in the diphoton channel. | diphoton and diboson excesses in a left-right symmetric theory of dark matter |
we compare dark matter production from the thermal bath in the early universe with its direct production through the decay of the inflaton. we show that even if dark matter does not possess a direct coupling with the inflaton, standard model loop processes may be sufficient to generate the correct relic abundance. | radiative production of nonthermal dark matter |
defect induced trap states are essential in determining the performance of semiconductor photodetectors. the de-trap time of carriers from a deep trap could be prolonged by several orders of magnitude as compared to shallow trap, resulting in additional decay/response time of the device. here, we demonstrate that the trap states in two-dimensional res2 could be efficiently modulated by defect engineering through molecule decoration. the deep traps that greatly prolong the response time could be mostly filled by protoporphyrin (h2pp) molecules. at the same time, carrier recombination and shallow traps would in-turn play dominant roles in determining the decay time of the device, which can be several orders of magnitude faster than the as-prepared device. moreover, the specific detectivity of the device is enhanced (as high as ~1.89 x 10^13 jones) due to the significant reduction of dark current through charge transfer between res2 and molecules. defect engineering of trap states therefore provides a solution to achieve photodetectors with both high responsivity and fast response. | defect engineering for modulating the trap states in 2d photoconductors |
this paper presents a search for dark matter in the context of a two-higgs-doublet model together with an additional pseudoscalar mediator, a, which decays into the dark-matter particles. processes where the pseudoscalar mediator is produced in association with a single top quark in the 2hdm+a model are explored for the first time at the lhc. several final states which include either one or two charged leptons (electrons or muons) and a significant amount of missing transverse momentum are considered. the analysis is based on proton-proton collision data collected with the atlas experiment at √{s }=13 tev during lhc run 2 (2015-2018), corresponding to an integrated luminosity of 139 fb-1. no significant excess above the standard model predictions is found. the results are expressed as 95% confidence-level limits on the parameters of the signal models considered. | search for dark matter produced in association with a single top quark in √{s }=13 tev pp collisions with the atlas detector |
rades (relic axion detector exploratory setup) is a project with the goal of directly searching for axion dark matter above the 30μev scale employing custom-made microwave filters in magnetic dipole fields. currently rades is taking data at the lhc dipole of the cast experiment. in the long term, the rades cavities are envisioned to take data in the babyiaxo magnet. in this article we report on the modelling, building and characterisation of an optimised microwave-filter design with alternating irises that exploits maximal coupling to axions while being scalable in length without suffering from mode-mixing. we develop the mathematical formalism and theoretical study which justifies the performance of the chosen design. we also point towards the applicability of this formalism to optimise the madmax dielectric haloscopes. | scalable haloscopes for axion dark matter detection in the 30 μev range with rades |
hadronic showers transfer a relevant amount of their energy to electromagnetic subshowers. we show that the generation of "secondary" dark photons in these subshowers is significant and typically dominates the production at low dark photon masses. the resulting dark photons are however substantially less energetic than the ones originating from mesons decay. we illustrate this point both semianalytically and through monte carlo simulations. existing limits on vector-mediator scenarios for light dark matter are updated with the inclusion of the new production processes. | new production channels for light dark matter in hadronic showers |
we assess the impact of searches at flavor factories for new neutral resonances that couple to both photons and gluons. these are well motivated by "heavy axion" solutions of the strong cp problem and by frameworks addressing both dark matter and the higgs hierarchy problem. we use lhcb public diphoton data around the bsmass to derive the current best limit on these resonances for masses between 4.9 and 6.3 gev. we estimate that a future lhcb dedicated search would test an axion decay constant of o(tev) for axion masses in the few-to-tens of gev, being fully complementary to the low mass atlas and cms searches. we also derive the impact of babar searches based on ϒ decays and the future belle-ii reach. | new axion searches at flavor factories |
low-scale baryogenesis could be discovered at b factories and the lhc. in the b -mesogenesis paradigm [g. elor, m. escudero, and a. e. nelson, phys. rev. d 99, 035031 (2019), 10.1103/physrevd.99.035031], the c p -violating oscillations and subsequent decays of b mesons in the early universe simultaneously explain the origin of the baryonic and the dark matter of the universe. this mechanism for baryo- and dark matter genesis from b mesons gives rise to distinctive signals at collider experiments, which we scrutinize in this paper. we study c p -violating observables in the bq0-b¯q0 system, discuss current and expected sensitivities for the exotic decays of b mesons into a visible baryon and missing energy, and explore the implications of direct searches for a tev-scale colored scalar at the lhc and in meson-mixing observables. remarkably, we conclude that a combination of measurements at babar, belle, belle ii, lhcb, atlas, and cms can fully test b -mesogenesis. | collider signals of baryogenesis and dark matter from b mesons: a roadmap to discovery |
it has been proposed recently that a previously unobserved neutron decay branch to a dark matter particle (χ ) could account for the discrepancy in the neutron lifetime observed in experiments that use two different measurement techniques. one of the possible final states discussed includes a single χ along with an e+e- pair. we use data from the ucna (ultracold neutron asymmetry) experiment to set limits on this decay channel. coincident electron-like events are detected with ∼4 π acceptance using a pair of detectors that observe a volume of stored ultracold neutrons. the summed kinetic energy (ee+e-) from such events is used to set limits, as a function of the χ mass, on the branching fraction for this decay channel. for χ masses consistent with resolving the neutron lifetime discrepancy, we exclude this as the dominant dark matter decay channel at ≫5 σ level for 100 <ee+e-<644 kev . if the χ +e+e- final state is not the only one, we set limits on its branching fraction of <10-4 for the above ee+e- range at >90 % confidence level. | search for dark matter decay of the free neutron from the ucna experiment: n →χ +e+e- |
a search for a higgs boson produced via vector-boson fusion and decaying into invisible particles is presented, using 20.3 fb$^{-1}$ of proton--proton collision data at a centre-of-mass energy of 8 tev recorded by the atlas detector at the lhc. for a higgs boson with a mass of 125 gev, assuming the standard model production cross section, an upper bound of 0.28 is set on the branching fraction of $h\to$ invisible at 95% confidence level, where the expected upper limit is 0.31. the results are interpreted in models of higgs-portal dark matter where the branching fraction limit is converted into upper bounds on the dark-matter--nucleon scattering cross section as a function of the dark-matter particle mass, and compared to results from the direct dark-matter detection experiments. | search for invisible decays of a higgs boson using vector-boson fusion in $pp$ collisions at $\\sqrt{s}=8$ tev with the atlas detector |
we report on the response of liquid xenon to low energy electronic recoils below 15 kev from beta decays of tritium at drift fields of 92 v /cm , 154 v /cm and 366 v /cm using the xenon100 detector. a data-to-simulation fitting method based on markov chain monte carlo is used to extract the photon yields and recombination fluctuations from the experimental data. the photon yields measured at the two lower fields are in agreement with those from literature; additional measurements at a higher field of 366 v /cm are presented. the electronic and nuclear recoil discrimination as well as its dependence on the drift field and photon detection efficiency are investigated at these low energies. the results provide new measurements in the energy region of interest for dark matter searches using liquid xenon. | signal yields of kev electronic recoils and their discrimination from nuclear recoils in liquid xenon |
we compute the non-perturbative contribution of semileptonic tensor operators (\overline{q}{σ}^{μ ν }q)(\overline{ℓ}{σ}_{μ ν}ℓ ) to the purely leptonic process μ → eγ and to the electric and magnetic dipole moments of charged leptons by matching onto chiral perturbation theory at low energies. this matching procedure has been used extensively to study semileptonic and leptonic weak decays of hadrons. in this paper, we apply it to observables that contain no strongly interacting external particles. the non-perturbative contribution to μ → e processes is used to extract the best current bound on lepton-flavor-violating semileptonic tensor operators, λbsm ≳ 450 tev. we briefly discuss how the same method applies to dark-matter interactions. | non-perturbative effects in μ → eγ |
several extensions of the standard model predict the production of dark matter particles at the lhc. a search for dark matter particles produced in association with a dark higgs boson decaying into w+w− in the ℓ±νq q¯', final states with ℓ = e, μ is presented. this analysis uses 139 fb−1 of pp collisions recorded by the atlas detector at a centre-of-mass energy of 13 tev. the w± → q q ' ¯ decays are reconstructed from pairs of calorimeter-measured jets or from track-assisted reclustered jets, a technique aimed at resolving the dense topology from a pair of boosted quarks using jets in the calorimeter and tracking information. the observed data are found to agree with standard model predictions. scenarios with dark higgs boson masses ranging between 140 and 390 gev are excluded. | search for dark matter produced in association with a dark higgs boson decaying into w+w− in the one-lepton final state at √{s } = 13 tev using 139 fb−1 of pp collisions recorded with the atlas detector |
the standard model of quarks and leptons is extended to include the gauge symmetry u(1)χ which comes from so (10) → su (5) × u(1)χ. the radiative generation of dirac neutrino masses through dark matter is discussed in two examples. one allows for light dirac fermion dark matter. the other allows for self-interacting scalar dark matter with a light scalar mediator which decays only to two neutrinos. | scotogenic u(1)χ dirac neutrinos |
we consider the scattering of dark matter particles from superfluid liquid he 4 , which has been proposed as a target for their direct detection. focusing on dark matter masses below ∼1 mev , we demonstrate from sum-rule arguments the importance of the production of single phonons with energies ω ≲1 mev . we show further that the anomalous dispersion of phonons in liquid he 4 at low pressures [i.e., d2ω (q )/d q2>0 , where q and ω (q ) are the phonon momentum and energy] has the important consequence that a single phonon will decay over a relatively short distance into a shower of lower-energy phonons centered on the direction of the original phonon. thus, the experimental challenge in this regime is to detect a shower of low-energy phonons, not just a single phonon. additional information from the distribution of phonons in such a shower could enhance the determination of the dark matter mass. | searching for low mass dark matter via phonon creation in superfluid he 4 |
the strong light-matter optomechanical coupling offered by coherent scattering set-ups have allowed the experimental realization of quantum ground-state cavity cooling of the axial motion of a levitated nanoparticle [u. delić et al., science 367, 892 (2020), 10.1126/science.aba3993]. an appealing milestone is now quantum two-dimensional (2d) cooling of the full in-plane motion, in any direction in the transverse plane. by a simple adjustment of the trap polarization, one obtains two nearly equivalent modes, with similar frequencies ωx∼ωy and optomechanical couplings gx≃gy —in this experimental configuration we identify an optimal trap ellipticity, nanosphere size, and cavity linewidth which allows for efficient 2d cooling. moreover, we find that 2d cooling to occupancies nx+ny≲1 at moderate vacuum (10−6 mbar) is possible in a "goldilocks" zone bounded by √{κ γ /4 }≲gx,gy≲|ωx−ωy| ≲κ , where one balances the need to suppress dark modes while avoiding far-detuning of either mode or low cooperativities, and κ (γ ) is the cavity decay rate (motional heating rate). with strong-coupling regimes gx,gy≳κ in view one must consider the genuine three-way hybridization between x ,y and the cavity light mode resulting in hybridized bright/dark modes. finally, we show that bright/dark modes in the levitated set-up have a simple geometrical interpretation, related by rotations in the transverse plane, with implications for directional sensing. | coherent-scattering two-dimensional cooling in levitated cavity optomechanics |
a search for dark matter and unparticle production at the lhc has been performed using events containing two charged leptons (electrons or muons), consistent with the decay of a z boson, and large missing transverse momentum. this study is based on data collected with the cms detector in 2015, corresponding to an integrated luminosity of 2.3 fb-1 of proton-proton collisions at the lhc, at a center-of-mass energy of 13 tev. no excess over the standard model expectation is observed. compared to previous searches in this topology, which exclusively relied on effective field theories, the results are interpreted in terms of a simplified model of dark matter production for both vector and axial vector couplings between a mediator and dark matter particles. the first study of this class of models using cms data at √{s}=13 tev is presented. additionally, effective field theories of dark matter and unparticle production are used to interpret the data. [figure not available: see fulltext.] | search for dark matter and unparticles in events with a z boson and missing transverse momentum in proton-proton collisions at √{s}=13 tev |
a search for new physics is presented in final states with two oppositely charged leptons (electrons or muons), jets identified as originating from b quarks, and missing transverse momentum (ptmiss). the search uses proton-proton collision data at √{s }=13 tev amounting to 35.9 fb-1 of integrated luminosity collected using the cms detector in 2016. hypothetical signal events are efficiently separated from the dominant t t ¯ background with requirements on ptmiss and transverse-mass variables. no significant deviation is observed from the expected background. exclusion limits are set in the context of simplified supersymmetric models with pair-produced top squarks. for top squarks, decaying exclusively to a top quark and a neutralino, exclusion limits are placed at 95% confidence level on the mass of the lightest top squark up to 800 gev and on the lightest neutralino up to 360 gev. these results, combined with searches in the single-lepton and all-jet final states, raise the exclusion limits up to 1050 gev for the lightest top squark and up to 500 gev for the lightest neutralino. for top squarks undergoing a cascade decay through charginos and sleptons, the mass limits reach up to 1300 gev for top squarks and up to 800 gev for the lightest neutralino. the results are also interpreted in a simplified model with a dark matter (dm) particle coupled to the top quark through a scalar or pseudoscalar mediator. for light dm, mediator masses up to 100 (50) gev are excluded for scalar (pseudoscalar) mediators. the result for the scalar mediator achieves some of the most stringent limits to date in this model. | search for top squarks and dark matter particles in opposite-charge dilepton final states at √{s }=13 tev |
we show how 21 cm cosmology can test relic neutrino radiative decays into sterile neutrinos. using recent edges results, we derive constraints on the lifetime of the decaying neutrinos. if the edges anomaly will be confirmed, then there are two solutions, one for much longer and one for much shorter lifetimes than the age of the universe, showing how relic neutrino radiative decays can explain the anomaly in a simple way. we also show how to combine edges results with those from radio background observations, showing that potentially the arcade 2 excess can be also reproduced together with the edges anomaly within the proposed non-standard cosmological scenario. our calculation of the specific intensity at the redshifts probed by edges can be also applied to the case of decaying dark matter. | probing relic neutrino radiative decays with 21 cm cosmology |
we investigate the critical dynamics of spin superflow in an easy-plane antiferromagnetic spinor bose-einstein condensate. spin-dipole oscillations are induced in a trapped condensate by applying a linear magnetic field gradient and we observe that the damping rate increases rapidly as the field gradient increases above a certain critical value. the onset of dissipation is found to be associated with the generation of dark-bright solitons due to the modulation instability of the counterflow of two spin components. spin turbulence emerges as the solitons decay because of their snake instability. we identify another critical point for spin superflow, in which transverse magnon excitations are dynamically generated via spin-exchanging collisions, which leads to the transient formation of axial polar spin domains. | critical spin superflow in a spinor bose-einstein condensate |
the qcd axion cosmology depends crucially on whether the qcd axion is present during inflation or not. we point out that contrary to the standard criterion, the peccei-quinn (pq) symmetry could remain unbroken during inflation, even when the axion decay constant, fa, is (much) above the inflationary hubble scale, hi. this is achieved through the heavy lifting of the pq scalar field due to its leading nonrenormalizable interaction with the inflaton, encoded in a high-dimensional operator which respects the approximate shift symmetry of the inflaton. the mechanism opens up a new window for the post-inflationary qcd axion and significantly enlarges the parameter space, in which the qcd axion dark matter with fa>hi could be compatible with high-scale inflation and free from constraints on axion isocurvature perturbations. there also exist nonderivative couplings, which still keep the inflaton shift symmetry breaking under control, to achieve the heavy lifting of the pq field during inflation. additionally, by introducing an early matter domination era, more parameter space of high fa could yield the observed dm abundance. | opening up a window on the postinflationary qcd axion |
in this paper we study a leptophilic dark matter scenario involving feeble dark matter coupling to the standard model (sm) and compressed dark matter-mediator mass spectrum. we consider a simplified model where the sm is extended with one majorana fermion, the dark matter, and one charged scalar, the mediator, coupling to the sm leptons through a yukawa interaction. we first discuss the dependence of the dark matter relic abundance on the yukawa coupling going continuously from freeze-in to freeze-out with an intermediate stage of conversion driven freeze-out. focusing on the latter, we then exploit the macroscopic decay length of the charged scalar to study the resulting long-lived-particle signatures at collider and to explore the experimental reach on the viable portion of the parameter space. | a feeble window on leptophilic dark matter |
we investigate the capability of the future electron collider cepc in probing the parameter space of several dark matter models, including millicharged dark matter models, z ' portal dark matter models, and effective dark matter operators. in our analysis, the monophoton final state is used as the primary channel to detect dark matter models at cepc. to maximize the signal to background significance, we study the energy and angular distributions of the monophoton channel arising from dark matter models and from the standard model to design a set of detector cuts. for the z ' portal dark matter, we also analyze the z ' boson visible decay channel which is found to be complementary to the monophoton channel in certain parameter space. the cepc reach in the parameter space of dark matter models is also put in comparison with xenon1t. we find that cepc has the unprecedented sensitivity to certain parameter space for the dark matter models considered; for example, cepc can improve the limits on millicharge by one order of magnitude than previous collider experiments for o(1)-100 gev dark matter. | probing dark matter particles at cepc |
the deap-3600 experiment is searching for weakly interacting massive particles dark matter with a 3.3 ×1 03 kg single phase liquid argon (lar) target, located 2.1 km underground at snolab. the experimental signature of dark matter interactions is kilo electron volt-scale 40ar nuclear recoils producing 128 nm lar scintillation photons observed by photomultiplier tubes. the largest backgrounds in deap-3600 are electronic recoils (ers) induced by β and γ rays originating from internal and external radioactivity in the detector material. a background model of the er interactions in deap-3600 was developed and is described in this work. the model is based on several components which are expected from radioisotopes in the lar, from ex situ material assay measurements, and from dedicated independent in situ analyses. this prior information is used in a bayesian fit of the er components to a 247.2 d dataset to model the radioactivity in the surrounding detector materials. pulse-shape discrimination separates er and nr events. however, detailed knowledge of the er background and activity of detector components sets valuable constraints on nr backgrounds including neutrons and alphas. in addition, the activity of 42ar in lar in deap-3600 is determined by measuring the daughter decay of 42k. this cosmogenically activated trace isotope is a relevant background at higher energies for other rare event searches using atmospheric argon, e.g., darkside-20k, gerda, or legend. the specific activity of 42ar in the atmosphere is found to be 40.4 ±5.9 μ bq /kg of argon. | electromagnetic backgrounds and potassium-42 activity in the deap-3600 dark matter detector |
we investigate the prospects for producing new, light, hidden states at a future e + e - collider in a higgsed dark u(1) dmodel, which we call the double dark portal model. the simultaneous presence of both vector and scalar portal couplings immediately modifies the standard model higgsstrahlung channel, e + e - → zh, at leading order in each coupling. in addition, each portal leads to complementary signals which can be probed at direct and indirect detection dark matter experiments. after accounting for current constraints from lep and lhc, we demonstrate that a future e + e - higgs factory will have unique and leading sensitivity to the two portal couplings by studying a host of new production, decay, and radiative return processes. besides the possibility of exotic higgs decays, we highlight the importance of direct dark vector and dark scalar production at e + e - machines, whose invisible decays can be tagged from the recoil mass method. | a tale of two portals: testing light, hidden new physics at future e + e - colliders |
a search for supersymmetry (susy) is performed in final states comprising one or more jets and missing transverse momentum using data from proton-proton collisions at a centre-of-mass energy of 13 tev. the data were recorded with the cms detector at the cern lhc in 2016 and correspond to an integrated luminosity of 35.9 fb-1. the number of signal events is found to agree with the expected background yields from standard model processes. the results are interpreted in the context of simplified models of susy that assume the production of gluino or squark pairs and their prompt decay to quarks and the lightest neutralino. the masses of bottom, top, and mass-degenerate light-flavour squarks are probed up to 1050, 1000, and 1325 gev, respectively. the gluino mass is probed up to 1900, 1650, and 1650 gev when the gluino decays via virtual states of the aforementioned squarks. the strongest mass bounds on the neutralinos from gluino and squark decays are 1150 and 575 gev, respectively. the search also provides sensitivity to simplified models inspired by split susy that involve the production and decay of long-lived gluinos. values of the proper decay length cτ 0 from 10-3 to 105 mm are considered, as well as a metastable gluino scenario. gluino masses up to 1750 and 900 gev are probed for cτ 0 = 1 mm and for the metastable state, respectively. the sensitivity is moderately dependent on model assumptions for cτ 0 ≳ 1 m. the search provides coverage of the cτ 0 parameter space for models involving long-lived gluinos that is complementary to existing techniques at the lhc. [figure not available: see fulltext.] | search for natural and split supersymmetry in proton-proton collisions at √{s}=13 tev in final states with jets and missing transverse momentum |
we report results of a search for dark-matter-nucleon interactions via a dark mediator using optimized low-energy data from the pandax-4t liquid xenon experiment. with the ionization-signal-only data and utilizing the migdal effect, we set the most stringent limits on the cross section for dark matter masses ranging from 30 mev /c2 to 2 gev /c2 . under the assumption that the dark mediator is a dark photon that decays into scalar dark matter pairs in the early universe, we rule out significant parameter space of such thermal relic dark-matter model. | search for dark-matter-nucleon interactions with a dark mediator in pandax-4t |
the measurement of the triple gauge couplings (tgcs) is a central part of diboson studies at the lhc. in this letter we consider the zγ process and include anomalous tgcs (atgcs) in the event generation at next-to-next-to-leading order qcd accuracy (nnlo+ps) within the minnlops framework. while our implementation is fully general and applies to both z →ℓ+ℓ- and z → ν ν bar decays, we focus here on the ν ν bar γ final state. after validation of our simulation of ν ν bar γ events, for which nnlo+ps accuracy is achieved for the first time, the effects of atgcs on various distributions are studied. moreover, we show the relevance of nnlo+ps accuracy for the ν ν bar γ background to photon plus missing energy signatures in dark-matter searches, and we compare minnlops predictions for ν ν bar γ production to recent 13 tev data. | anomalous couplings in zγ events at nnlo+ps and improving ν ν bar γ backgrounds in dark-matter searches |
the clockwork axion refers to a family of aligned multi-axion models that lead to an exponential hierarchy between the scale of peccei-quinn symmetry breaking and the scale of the axion decay constant. the clockworking can bring the peccei-quinn-scale particles to within reach of collider experiments. in this work we are interested in whether cosmological observations impose any new constraints on the clockwork axion. if the universe reheats above the scale of peccei-quinn breaking, then the ensuing cosmological phase transition produces a network of topological defects, which have a qualitatively different behavior from the string-wall network in the usual axion models. we estimate the relic abundances of axion dark matter and dark radiation that arise from the emission of axions by the defect network, and we infer a constraint on the scale of peccei-quinn breaking and the mass spectrum. we find that the defect contribution to the axion dark matter relic abundance is generally negligible. however, the defect production of relativistic axion dark radiation becomes significant if the scale of peccei-quinn symmetry breaking is larger than 100 tev, and measurements of δ n eff provide a new probe of this class of models. | cosmological aspects of the clockwork axion |
we propose to use fermionic atoms with degenerate ground and excited internal levels (fg→fe), loaded into the motional ground state of an optical lattice with two atoms per lattice site, to realize dark states with no radiative decay. the physical mechanism behind the dark states is an interplay of pauli blocking and multilevel dipolar interactions. the dark states are independent of lattice geometry, can support an extensive number of excitations, and can be coherently prepared using a raman scheme taking advantage of the quantum zeno effect. these attributes make them appealing for atomic clocks, quantum memories, and quantum information on decoherence free subspaces. | dark states of multilevel fermionic atoms in doubly filled optical lattices |
there exist non-trivial stationary points of the euclidean action for an axion particle minimally coupled to einstein gravity, dubbed wormholes. they explicitly break the continuos global shift symmetry of the axion in a non-perturbative way, and generate an effective potential that may compete with qcd depending on the value of the axion decay constant. in this paper, we explore both theoretical and phenomenological aspects of this issue. on the theory side, we address the problem of stability of the wormhole solutions, and we show that the spectrum of the quadratic action features only positive eigenvalues. on the phenomenological side, we discuss, beside the obvious application to the qcd axion, relevant consequences for models with ultralight dark matter, black hole superradiance, and the relaxation of the electroweak scale. we conclude discussing wormhole solutions for a generic coset and the potential they generate. | wormholes and masses for goldstone bosons |
we examine the sensitivity of the large hadron collider (lhc) to light lepton portal dark matter with its mass below 10 gev. the model features an extra doublet scalar field and singlet dirac dark matter, which have yukawa interactions with left-handed leptons. to correctly produce the dark matter abundance via the thermal freeze-out, a large mass splitting among the extra scalars is required, thus providing a light neutral scalar below o (10 )gev and heavy neutral and charged scalars at the electroweak scale. in this paper, we focus on the electroweak pair-production of the extra scalars with subsequent model-specific scalar decays and evaluate the current constraints with the lhc run 2 data and the discovery potential at the high luminosity lhc (hl-lhc). it turns out that a large part of the theoretically allowed parameter space can be tested at the hl-lhc by taking into account complementarity between slepton searches and mono-z plus missing transverse energy search. we also discuss same-sign charged scalar production as a unique prediction of the model, and the implication of the collider searches in the thermal dark matter scenario. | light lepton portal dark matter meets the lhc |
we unveil the dynamical formation of multiple localized structures in the form of dark-bright and dark-antidark solitary waves that emerge upon quenching a one-dimensional particle-imbalanced bose-bose mixture. interspecies interaction quenches drive the system out of equilibrium while the so-called miscible-immiscible threshold is crossed in a two-directional manner. dark-bright entities are spontaneously generated for quenches towards the phase separated regime and dark-antidark states are formed in the reverse process. the distinct mechanisms of creation of the aforementioned states are discussed in detail and their controlled generation is showcased. in both processes, it is found that the number of solitary waves generated is larger for larger particle imbalances, a result that is enhanced for stronger postquench interspecies interactions. additionally the confining geometry highly affects the production of both types of states with a decaying solitary wave formation occurring for tighter traps. furthermore, in both of the aforementioned transitions, the breathing frequencies measured for the species differ significantly for highly imbalanced mixtures. finally, the robustness of the dynamical formation of dark-bright and dark-antidark solitons is also demonstrated in quasi-one-dimensional setups. | spontaneous generation of dark-bright and dark-antidark solitons upon quenching a particle-imbalanced bosonic mixture |
we consider the gauged u (1) clockwork theory with a product of multiple gauge groups and discuss the continuum limit of the theory to a massless gauged u (1) with linear dilaton background in five dimensions. the localization of the lightest state of gauge fields on a site in the theory space naturally leads to exponentially small effective couplings of external matter fields localized away from the site. we discuss the implications of our general discussion with some examples, such as mediators of dark matter interactions, flavor-changing b-meson decays as well as d-term susy breaking. | gauged u(1) clockwork theory |
we present a search for the decays of $b^0$ mesons into a final state containing a $\lambda$ baryon and missing energy. these results are obtained from a $711\text{fb}^{-1}$ data sample that contains $772 \times 10^6$ $b{\kern 0.18em}\overline{\kern -0.18em b}$ pairs and was collected near the $\upsilon(4s)$ resonance with the belle detector at the kekb asymmetric-energy $e^+e^-$ collider. we use events in which one $b$ meson is fully reconstructed in a hadronic decay mode and require the remainder of the event to consist of only a single $\lambda$. no evidence for these decays is found and we set $90\%$ confidence level upper limits on the branching fractions in the range $2.1$-$3.8\times 10^{-5}$. this measurement provides the world's most restrictive limits, with implications for baryogenesis and dark matter production. | search for $b^0$ meson decays into $\\lambda$ and missing energy with a hadronic tagging method at belle |
it has been proposed that in a part of the parameter space of the standard model completed by three generations of kev…gev right-handed neutrinos, neutrino masses, dark matter, and baryon asymmetry can be accounted for simultaneously. here we numerically solve the evolution equations describing the cosmology of this scenario in a 1+2 flavour situation at temperatures t ≤ 5 gev, taking as initial conditions maximal lepton asymmetries produced dynamically at higher temperatures, and accounting for late entropy and lepton asymmetry production as the heavy flavours fall out of equilibrium and decay. for 7 kev dark matter mass and other parameters tuned favourably, ∼ 10% of the observed abundance can be generated. possibilities for increasing the abundance are enumerated. | sterile neutrino dark matter via gev-scale leptogenesis? |
the recent observation of an excess in the electronic recoil data by the xenon1t detector has drawn many attentions as a potential hint for an extension of the standard model (sm). absorption of a vector boson with the mass of ma‧ ∈ (2kev , 3kev) is one of the feasible explanations to the excess. in the case where the vector boson explains the dark matter (dm) population today, it is highly probable that the vector boson belongs to a class of the warm dark matter (wdm) due to its suspected mass regime. in such a scenario, providing a good fit for the excess, the kinetic mixing κ ∼10-15 asks for a non-thermal origin of the vector dm. in this letter, we consider a scenario where the gauge boson is nothing but the u(1) b - l gauge boson and its non-thermal origin is attributed to the decay of the coherently oscillating scalar of which condensation induces the spontaneous breaking of u(1) b - l. we discuss implications for the early universe physics when the warm nature of the vector dm serves as a resolution to both the small scale problems that λcdm model encounters and the xenon1t anomaly. | feebly interacting u(1)b-l gauge boson warm dark matter and xenon1t anomaly |
a search for dark matter (dm) particles produced in association with a hadronically decaying vector boson is performed using $pp$ collision data at a centre-of-mass energy of $\sqrt{s}=13$ tev corresponding to an integrated luminosity of 36.1 fb$^{-1}$, recorded by the atlas detector at the large hadron collider. this analysis improves on previous searches for processes with hadronic decays of $w$ and $z$ bosons in association with large missing transverse momentum (mono-$w/z$ searches) due to the larger dataset and further optimization of the event selection and signal region definitions. in addition to the mono-$w/z$ search, the as yet unexplored hypothesis of a new vector boson $z^\prime$ produced in association with dark matter is considered (mono-$z^\prime$ search). no significant excess over the standard model prediction is observed. the results of the mono-$w/z$ search are interpreted in terms of limits on invisible higgs boson decays into dark matter particles, constraints on the parameter space of the simplified vector-mediator model and generic upper limits on the visible cross sections for $w/z$+dm production. the results of the mono-$z^\prime$ search are shown in the framework of several simplified-model scenarios involving dm production in association with the $z^\prime$ boson. | search for dark matter in events with a hadronically decaying vector boson and missing transverse momentum in $pp$ collisions at $\\sqrt{s} = 13$ tev with the atlas detector |
in higgs portal models of fermion dark matter, scalar couplings are unavoidably suppressed by strong bounds from direct detection experiments. as a consequence, thermal dark matter relics must coexist with mediators in a compressed spectrum of dark particles. small couplings and small mass splittings lead to slow mediator decays, leaving signatures with displaced vertices or disappearing tracks at colliders. we perform a comprehensive analysis of long-lived mediators at the lhc in the context of a minimal dark matter model with a naturally small higgs portal, also known as the wino-bino scenario in supersymmetry. existing searches for disappearing charged tracks and displaced hard leptons already exclude tiny portal couplings that cannot be probed by current direct and indirect detection experiments. for larger portal couplings, we predict new signatures with displaced soft leptons, which are accessible with run-ii data. searches for displaced particles are sensitive to weakly coupling mediators with masses up to the tev scale, well beyond the reach of prompt signals. | long live the higgs portal! |
cold atoms experiments offer invaluable information on superfluid dynamics, including decay cascades of topological defects. while the cascade properties are well established for bose systems, our understanding of their behavior in fermi counterparts is very limited, in particular in spin-imbalanced systems, where superfluid (paired) and normal (unpaired) particles naturally coexist giving rise to complex spatial structure of the atomic cloud. here we show, based on a newly developed microscopic approach, that the decay cascades of topological defects are dramatically modified by the spin polarization. we demonstrate that decay cascades end up at different stages: "dark soliton," "vortex ring," or "vortex line," depending on the polarization. we reveal that it is caused by sucking of unpaired particles into the soliton's internal structure. as a consequence vortex reconnections are hindered and we anticipate that quantum turbulence phenomenon can be significantly affected, indicating new physics induced by polarization effects. | suppressed solitonic cascade in spin-imbalanced superfluid fermi gas |
we calculate the accurate spectrum of the stochastic gravitational-wave background from u(1) gauge fields produced by axion dark matter. the explosive production of gauge fields soon invalidates the applicability of the linear analysis and one needs nonlinear schemes. we make use of numerical lattice simulations to properly follow the nonlinear dynamics such as backreaction and rescattering which gives important contributions to the emission of gravitational waves. it turns out that the axion with the decay constant f ∼1016 gev and the mass m ∼10-14 ev which gives the correct dark matter abundance predicts the circularly polarized gravitational-wave signature detectable by ska. we also show that the resulting gravitational-wave spectrum has a potential to explain nanograv 12.5 yr data. | nano-hz gravitational-wave signature from axion dark matter |
the discovery of diffuse sub-pev gamma-rays by the tibet asγ collaboration promises to revolutionize our understanding of the high-energy astrophysical universe. it has been shown that these data broadly agree with prior theoretical expectations. we study the impact of this discovery on a well-motivated new physics scenario: pev-scale decaying dark matter (dm). considering a wide range of final states in dm decay, a number of dm density profiles, and numerous astrophysical background models, we find that these data provide the most stringent limit on dm lifetime for various standard model final states. in particular, we find that the strongest constraints are derived for dm masses in between a few pev to a few tens of pev. near-future data of these high-energy gamma-rays can be used to discover pev-scale decaying dm. | search for dark matter using sub-pev γ -rays observed by tibet asγ |
we perform a systematic study of the fermionic dm absorption interactions on electron target in the context of effective field theory. the fermionic dm absorption is not just sensitive to sub-mev dm with efficient energy release, but also gives a unique signature with clear peak in the electron recoil spectrum whose shape is largely determined by the atomic effects. fitting with the xenon1t and pandax-ii data prefers dm mass at mχ = 59 kev and 105 kev, respectively, while the cut-off scale is probed up to around 1 tev. the dm overproduction in the early universe, the invisible decay effect on the cosmological evolution, and the visible decay signal collected by the astrophysical x(gamma)-ray observations (insight-hxmt, nustar, heao-1, and integral) are thoroughly explored to constrain the dm absorption interactions. with stringent bounds on the tensor and pseudo-scalar operators, the other fermionic dm operators are of particular interest at tonne-scale direct detection experiments such as pandax-4t, xenonnt, and lz. | revisiting the fermionic dark matter absorption on electron target |
an axion-like-particle (alp) in the post-inflationary scenario with domain wall number n > 1 can be dark matter if the residual &z;n symmetry has a small explicit breaking. although we cannot determine the full dynamics of the system reliably, we provide evidence that such an alp can account for the observed dark matter abundance while having a relatively small decay constant and consequently a possibly large coupling to photons. in particular, we determine the number of domain walls per hubble patch around the time when they form using numerical simulations and combine this with analytic expectations about the subsequent dynamics. we show that the strongest constraint on the decay constant is likely to come from the dark matter alps being produced with large isocurvature fluctuations at small spatial scales. we also comment on the uncertainties on the dark matter small-scale structure that might form from these overdensities, in particular pointing out the importance of quantum pressure in the n = 1 case. | post-inflationary axions: a minimal target for axion haloscopes |
we argue that demanding a consistent cosmological history, including the absence of domain walls and strongly interacting relics at the peccei-quinn scale, singles out two concrete realizations of hadronic qcd axions as viable dark matter models. these realizations generally feature flavor-violating axion couplings to standard model quarks that are unsuppressed at low energies. as a consequence, experiments looking for flavor-violating hadronic processes involving the axion can be sensitive probes of qcd axion dark matter models. in particular, we show that the na62 and koto experiments could detect the k → π + a decay for axions consistent with the observed dark matter abundance via the post-inflationary misalignment mechanism. | the flavor of qcd axion dark matter |
cosmic birefringence is predicted if an axionlike particle (alp) moves after the recombination. we show that this naturally happens if the alp is coupled to the dark matter density because it then acquires a large effective mass after the matter-radiation equality. our scenario applies to a broad range of the alp mass mϕ≲10-28 ev , even smaller than the present hubble constant. we give a simple model to realize this scenario, where dark matter is made of hidden monopoles, which give the alp such a large effective mass through the witten effect. the mechanism works if the alp decay constant is of order of the grand unified theory scale without a fine-tuning of the initial misalignment angle. for smaller decay constant, the hidden monopole can be a fraction of dark matter. we also study the implications for the qcd axion, and show that the domain wall problem can be solved by the effective mass. | cosmic birefringence triggered by dark matter domination |
a new scheme for lightest supersymmetric particle (lsp) dark matter is introduced and studied in theories of tev supersymmetry with a qcd axion, a, and a high reheat temperature after inflation, tr . a large overproduction of axinos ( ã) and gravitinos (\tilde{g}) from scattering at tr , and from freeze-in at the tev scale, is diluted by the late decay of a saxion condensate that arises from inflation. the two lightest superpartners are ã, with mass of order the tev scale, and \tilde{g} with mass m 3/2 anywhere between the kev and tev scales, depending on the mediation scale of supersymmetry breaking. dark matter contains both warm and cold components: for \tilde{g} lsp the warm component arises from \tilde{a}\to \tilde{g}a , while for ã lsp the warm component arises from \tilde{g}\to \tilde{a}a . the free-streaming scale for the warm component is predicted to be of order 1 mpc (and independent of m 3/2 in the case of \tilde{g} lsp). trcan be as high as 1016 gev, for any value of m 3/2, solving the gravitino problem. the pq symmetry breaking scale v pq depends on trand m 3/2 and can be anywhere in the range (1010 - 1016) gev. detailed predictions are made for the lifetime of the neutralino losp decaying to ã+ h/z and \tilde{g}+h/z/γ , which is in the range of (10-1 -106)m over much of parameter space. for an axion misalignment angle of order unity, the axion contribution to dark matter is sub-dominant, except when v pq approaches 1016 gev. | gravitino or axino dark matter with reheat temperature as high as 1016 gev |
recently, we have witnessed two hints of physics beyond the standard model: a 3.3σ local excess (ma 0 = 52 gev) in the search for h0 → a0a0 → bb ¯μ+μ− and a 4.2σ deviation from the sm prediction in the (g − 2)μ measurement. the first excess was found by the atlas collaboration using 139 fb−1 data at √{s } = 13 tev. the second deviation is a combination of the results from the brookhaven e821 and the recently reported fermilab e989 experiment. we attempt to explain these deviations in terms of a renormalizable simplified dark matter model. inspired by the null signal result from dark matter (dm) direct detection, we interpret the possible new particle, a0, as a pseudoscalar mediator connecting dm and the standard model. on the other hand, a new vector-like muon lepton can explain these two excesses at the same time while contributing to the dm phenomenology. | shedding light on dark matter with recent muon (g − 2) and higgs exotic decay measurements |
in natural supersymmetry models, higgsinos are always light because μ2 cannot be much larger than mz2, while squarks and gluinos may be very heavy. unless gluinos are discovered at lhc13, the commonly assumed unification of gaugino mass parameters will imply correspondingly heavy winos and binos, resulting in a higgsino-like lightest supersymmetric particle (lsp) and small inter-higgsino mass splittings. the small visible energy release in higgsino decays makes their pair production difficult to detect at the lhc. relaxing gaugino mass universality allows for relatively light winos and binos without violating lhc gluino mass bounds and without affecting naturalness. in the case where the bino mass m1≲μ , then one obtains a mixed bino-higgsino lsp with instead sizable w∼1-z∼1 and z∼2-z∼1 mass gaps. the thermal neutralino abundance can match the measured dark matter density in contrast to models with a higgsino-like lsp where weakly interacting massive particles are underproduced by factors of 10-15. if instead m2≲μ , then one obtains a mixed wino-higgsino lsp with large z∼2-z∼1 but small w∼1-z∼1 mass gaps with still an underabundance of thermally produced weakly interacting massive particles. we discuss dark matter detection in other direct and indirect detection experiments and caution that the bounds from these must be interpreted with care. finally, we show that lhc13 experiments should be able to probe these nonuniversal mass scenarios via a variety of channels including multilepton+etmiss events, w z +etmiss events, w h +etmiss events, and w±w±+etmiss events from electroweak chargino and neutralino production. | natural susy with a bino- or wino-like lsp |
production of the matter-antimatter asymmetry in the b-mesogenesis mechanism is directly related to the branching fraction of seemingly baryon number violating decays of b mesons into a light standard model baryon and missing energy. achieving the observed baryon asymmetry requires that the branching fraction for such decays be greater than about 10-7-10-5. experimental searches at b factories and hadron colliders target specific decay modes. therefore, computing the exclusive branching fraction for each decay is a critical step towards testing mesogenesis. in this work we use qcd light cone sum rules to compute the form factors and branching fractions of the various possible channels contributing to the baryon asymmetry. using the results, we comment on implications for current and future experimental searches. | branching fractions of b meson decays in mesogenesis |
we revisit the multilepton (m l )+ et+x signatures of the inert doublet model (idm) of dark matter in future lhc experiments for m =3 , 4 and simulate, for the first time, the m =5 case. here x stands for any number of jets. we illustrate these signals with benchmark points consistent with the usual constraints like unitarity, perturbativity, the precision electroweak data, the observed dark matter relic density of the universe and, most importantly, the stringent lhc constraints from the post-higgs (h ) discovery era like the measured mh and the upper bound on the invisible width of h decay, which were not included in earlier analyses of multilepton signatures. we find that if the idm is embedded in a grand desert scenario so that the unitarity constraint holds up to a very high scale, the whole of the highly restricted parameter space allowed by the above constraints can be probed at the lhc via the 3 l signal for an integrated luminosity ∼3000 fb-1 . on the other hand, if any new physics shows up at a scale ∼10 tev , only a part of the enlarged allowed parameter space can be probed. the 4 l and 5 l signals can help to discriminate among different idm scenarios as and when sufficient integrated luminosity accumulates. | exploring collider signatures of the inert higgs doublet model |
dark matter axion condensates may experience stimulated decays into photon pairs. this effect has been often interpreted as a parametric resonance of photons from the axion-photon coupling, leading to an exponential growth of the photon occupation number in a narrow instability band. most of the previous literature does not consider the possible evolution of the axion field due to the photon growth. we revisit this effect presenting a mean field solution of the axion-photon kinetic equations, in terms of number of photons and pair correlations. we study the limit of no axion depletion, recovering the known instability. moreover, we extend the results including a possible depletion of the axion field. in this case we find that the axion condensate exhibits the behavior of an inverted pendulum. we discuss the relevance of these effects for two different cases: a homogeneous axion field at recombination and a localized axion clump and discuss constraints that could result from the induced photon background. | dynamical evolution of axion condensates under stimulated decays into photons |
as any e+e- scattering process can be accompanied by a hard photon emission from the initial state radiation, the analysis of the energy spectrum and angular distributions of those photons can be used to search for hard processes with an invisible final state. thus high energy e+e- colliders offer a unique possibility for the most general search of dark matter (dm) based on the mono-photon signature. we consider production of dm particles at the international linear collider (ilc) and compact linear collider (clic) experiments via a light mediator exchange. detector effects are taken into account within the delphes fast simulation framework. limits on the light dm production in a simplified model are set as a function of the mediator mass and width based on the expected two-dimensional distributions of the reconstructed mono-photon events. the experimental sensitivity is extracted in terms of the dm production cross section. limits on the mediator couplings are then presented for a wide range of mediator masses and widths. for light mediators, for masses up to the centre-of-mass energy of the collider, coupling limits derived from the mono-photon analysis are more stringent than those expected from direct resonance searches in decay channels to sm particles. | sensitivity of future linear e+e- colliders to processes of dark matter production with light mediator exchange |
a <mml:mmultiscripts>rn 220 </mml:mmultiscripts> source is deployed on the xenon100 dark matter detector in order to address the challenges in calibration of tonne-scale liquid noble element detectors. we show that the <mml:mmultiscripts>pb 212 </mml:mmultiscripts> beta emission can be used for low-energy electronic recoil calibration in searches for dark matter. the isotope spreads throughout the entire active region of the detector, and its activity naturally decays below background level within a week after the source is closed. we find no increase in the activity of the troublesome <mml:mmultiscripts>rn 222 </mml:mmultiscripts> background after calibration. alpha emitters are also distributed throughout the detector and facilitate calibration of its response to <mml:mmultiscripts>rn 222 </mml:mmultiscripts> . using the delayed coincidence of <mml:mmultiscripts>rn 220 </mml:mmultiscripts>- <mml:mmultiscripts>po 216 </mml:mmultiscripts> , we map for the first time the convective motion of particles in the xenon100 detector. additionally, we make a competitive measurement of the half-life of <mml:mmultiscripts>po 212 </mml:mmultiscripts> , t1 /2=(293.9 ±(1.0 )stat±(0.6 )sys) ns . | results from a calibration of xenon100 using a source of dissolved radon-220 |
we demonstrate optically induced switching between bright and dark charged divacancy defects in 4h-sic. photoluminescence excitation and time-resolved photoluminescence measurements reveal the excitation conditions for such charge conversion. for an energy below 1.3 ev (above 950 nm), the pl is suppressed by more than two orders of magnitude. the pl is recovered in the presence of a higher energy repump laser with a time-averaged intensity less than 0.1% that of the excitation field. under a repump of 2.33 ev (532 nm), the pl increases rapidly, with a time constant 30 μs. by contrast, when the repump is switched off, the pl decreases first within 100-200 μs, followed by a much slower decay of a few seconds. we attribute these effect to the conversion between two different charge states. under an excitation at energy levels below 1.3 ev, vsivc0 are converted into a dark charge state. a repump laser with an energy above 1.3 ev can excite this charged state and recover the bright neutral state. this optically induced charge switching can lead to charge-state fluctuations but can be exploited for long-term data storage or nuclear-spin-based quantum memory. | optical switching of defect charge states in 4h-sic |
180mta is the longest-lived metastable state presently known. its decay has not been observed yet. in this work, we report a new result on the decay of 180mta obtained with a 2015.12-g tantalum sample measured for 527.7 d with an ultra-low background hpge detector in the stella laboratory of the laboratori nazionali del gran sasso (lngs), in italy. before the measurement, the sample has been stored deep-underground for ten years, resulting in subdominant background contributions from cosmogenically activated 182ta . we observe no signal in the regions of interest and set half-life limits on the process for the two channels ec and β-: t1 /2 ,ec>1.6 ×1018 year and t1 /2 ,β->1.1 ×1018 year (90% c. i.), respectively. we also set the limit on the γ de-excitation / ic channel: t1 /2 ,ic>4.1 ×1015 year (90% c. i.). these are, as of now, the most stringent bounds on the decay of 180mta worldwide. finally, we test the hypothetical scenarios of de-excitation of 180mta by cosmological dark matter and constrain new parameter space for strongly-interacting dark-matter particle with mass up to 105 gev. | deep-underground search for the decay of 180mta with an ultra-low-background hpge detector |
quantum emitters in confined arrays exhibit geometry dependent collective dynamics. in particular, nanoscopic regular polygon-shaped arrays can possess sub-radiant states with an exciton lifetime growing exponentially with emitter number. we show that by placing an extra resonant absorptive dipole at the ring center, such a structure becomes a highly efficient single-photon absorber with tailorable frequency. interestingly, for exactly nine emitters in a nonagon, as it appears in a common biological light-harvesting complex (lhc2), we find a distinct minimum for its most dark state decay rate and a maximum of the effective absorption cross-section, surpassing that for a single absorptive emitter. the origin of this optimum for nine emitters can be geometrically traced to the fact that the sum of coupling strengths of a single ring emitter to all others including the center ring closely matches the coupling of the center to all ring emitters. the emerging dark collective eigenstate has dominant center occupation facilitating efficient energy absorption and fast transport. the resonance frequency can be tuned via ring size and dipole polarization. in analogy to parabolic antennas, the ring concentrates the incoming radiation at the center without being significantly excited, which minimizes transport loss and time. | efficient nano-photonic antennas based on dark states in quantum emitter rings |
we consider the production of dark matter in association with a pair of top quarks, mediated by a scalar or pseudoscalar particle in a generic simplified model. we demonstrate that the difference of azimuthal angle between the two leptons δ ϕℓℓ, in the dileptonic top decay mode, can directly probe the c p -properties of the mediator. we estimate the constraints to strength and c p -structure of dark matter production for these well-motivated simplified models from the lhc run ii. | constraining the strength and c p structure of dark production at the lhc: the associated top-pair channel |
a weighted average weak mixing angle θw derived from relatively low q2 experiments is compared with the standard model prediction obtained from precision measurements. the approximate 1.8 sigma discrepancy is fit with an intermediate mass (∼10 - 35 gev ) "dark" z boson zd, corresponding to a u (1 )d gauge symmetry of hidden dark matter, which couples to our world via kinetic and z - zd mass mixing. constraints on such a scenario are obtained from precision electroweak bounds and searches for the rare higgs decays h →z zd→4 charged leptons at the lhc. the sensitivity of future anticipated low q2 measurements of sin2θw(q2) to intermediate mass zd is also illustrated. this dark z scenario can provide interesting concomitant signals in low energy parity violating measurements and rare higgs decays at the lhc over the next few years. | low q2 weak mixing angle measurements and rare higgs decays |
the deap-3600 detector searches for the scintillation signal from dark matter particles scattering on a 3.3 tonne liquid argon target. the largest background comes from 39ar beta decays and is suppressed using pulse-shape discrimination (psd). we use two types of psd estimator: the prompt-fraction, which considers the fraction of the scintillation signal in a narrow and a wide time window around the event peak, and the log-likelihood-ratio, which compares the observed photon arrival times to a signal and a background model. we furthermore use two algorithms to determine the number of photons detected at a given time: (1) simply dividing the charge of each pmt pulse by the mean single-photoelectron charge, and (2) a likelihood analysis that considers the probability to detect a certain number of photons at a given time, based on a model for the scintillation pulse shape and for afterpulsing in the light detectors. the prompt-fraction performs approximately as well as the log-likelihood-ratio psd algorithm if the photon detection times are not biased by detector effects. we explain this result using a model for the information carried by scintillation photons as a function of the time when they are detected. | pulse-shape discrimination against low-energy ar-39 beta decays in liquid argon with 4.5 tonne-years of deap-3600 data |
in the framework of seesaw neutrino masses from heavy fermion triplets (σ+ ,σ0 ,σ-), the addition of a light fermion singlet n and a heavy scalar triplet (ρ+ ,ρ0 ,ρ-) has some important consequences. the new particles are assumed to be odd under a new z2 symmetry which is only broken softly, both explicitly and spontaneously. with n -σ0 mixing, freeze-in long-lived dark matter through higgs decay becomes possible. at the same time, the w mass is shifted slightly upward, as suggested by a recent precision measurement. | type iii neutrino seesaw, freeze-in long-lived dark matter, and the w mass shift |
we implement inflation in a nonsupersymmetric s u (5 ) model based on a nonminimal coupling of the axion field to gravity. the isocurvature fluctuations are adequately suppressed, axions comprise the dark matter, proton lifetime estimates are of order 8 ×1034- 3 ×1035 yr , and the observed baryon asymmetry arises via nonthermal leptogenesis. the presence of low-scale colored scalars ensures unification of the standard model gauge couplings and also helps in stabilizing the electroweak vacuum. | axion inflation, proton decay, and leptogenesis in s u (5 )×u (1 )p q |
we study bino-wino coannihilation scenario in the so-called spread or mini-split supersymmetry. we show that, in this model, a neutral wino has a macroscopic decay length in a wide range of parameter space. this characteristic feature could be observed as a displaced vertex plus missing transverse energy event at the lhc. in this paper, we study the current constraints and future prospects on the scenario based on the displaced vertex search performed by the atlas collaboration. it is found that a sizable parameter region can be probed at the 8 tev lhc run. this search strategy will considerably extend its reach at the next stage of the lhc running, and thus play a crucial role to examine a possibility of bino dark matter in the mini-split type supersymmetric models. | probing bino-wino coannihilation at the lhc |
we propose using quantum dots as novel targets to probe sub-gev dark matter-electron interactions. quantum dots are nanocrystals of semiconducting material, which are commercially available, with gram-scale quantities suspended in liter-scale volumes of solvent. quantum dots can be efficient scintillators, with near unity single-photon quantum yields, and their band-edge electronic properties are determined by their characteristic size, which can be precisely tuned. examples include lead sulfide and lead selenide quantum dots, which can be tuned to have sub-ev optical gaps. a dark-matter interaction can generate one or more electron-hole pairs (excitons), with the multiexciton state decaying via the emission of two photons with an efficiency of about 10% of the single-photon quantum yield. an experimental setup using commercially available quantum dots and two photomultiplier-tubes for detecting the coincident two-photon signal can already improve on existing dark-matter bounds, while using photodetectors with lower dark-count rates can improve on current constraints by orders of magnitude. | dark matter direct detection with quantum dots |
in this work we consider a simple model for dark matter and identify regions of parameter space where the relic abundance is set via kinematic thresholds, which open and close due to thermal effects. we discuss instantaneous freeze-out, where dark matter suddenly freezes-out when the channel connecting dark matter to the thermal bath closes, and decaying dark matter, where dark matter freezes-out while relativistic and later decays when a kinematic threshold temporarily opens. these mechanisms can occur in the vicinity of a one-step or a two-step phase transition. in all cases thermal effects provide this dynamic behaviour, while ensuring that dark matter remains stable until the present day. | variations on the vev flip-flop: instantaneous freeze-out and decaying dark matter |
oscura is a planned light-dark matter search experiment using skipper-ccds with a total active mass of 10 kg. as part of the detector development, the collaboration plans to build the oscura integration test (oit), an engineering test with 10% of the total mass. here we discuss the early science opportunities with the oit to search for millicharged particles (mcps) using the numi beam at fermilab. mcps would be produced at low energies through photon-mediated processes from decays of scalar, pseudoscalar, and vector mesons, or direct drell-yan productions. estimates show that the oit would be a world-leading probe for mcps in the mev mass range. | searching for millicharged particles with 1 kg of skipper-ccds using the numi beam at fermilab |
we study the dark matter (dm) discovery prospect and its spin discrimination in the theoretical framework of gauge invariant and renormalizable higgs portal dm models at the ilc with √{s} = 500 gev. in such models, the dm pair is produced in association with a z boson. in the case of the singlet scalar dm, the mediator is just the sm higgs boson, whereas for the fermion or vector dm there is an additional singlet scalar mediator that mixes with the sm higgs boson, which produces significant observable differences. after careful investigation of the signal and backgrounds both at parton level and at detector level, we find the signal with hadronically decaying z boson provides a better search sensitivity than the signal with leptonically decaying z boson. taking the fermion dm model as a benchmark scenario, when the dm-mediator coupling g_χ is relatively small, the dm signals are discoverable only for benchmark points with relatively light scalar mediator h_2. the spin discriminating from scalar dm is always promising, while it is difficult to discriminate from vector dm. as for g_χ approaching the perturbative limit, benchmark points with the mediator h_2 in the full mass region of interest are discoverable. the spin discriminating aspects from both the scalar and the fermion dm are quite promising. | characterizing higgs portal dark matter models at the ilc |
we experimentally characterize the optical nonlinear response of a cold atomic medium placed inside an optical cavity, and excited to rydberg states. the excitation to s and d rydberg levels is carried out via a two-photon transition in an electromagnetically induced transparency configuration, with a weak (red) probe beam on the lower transition, and a strong (blue) coupling beam on the upper transition. the observed optical nonlinearities induced by s states for the probe beam can be explained using a semi-classical model with van der waals’ interactions. for the d states, it appears necessary to take into account a dynamical decay of rydberg excitations into a long-lived dark state. we show that the measured nonlinearities can be explained by using a rydberg bubble model with a dynamical decay. | rydberg-induced optical nonlinearities from a cold atomic ensemble trapped inside a cavity |
we present the results of a direct detection search for mirror dark matter interactions, using data collected from the large underground xenon experiment during 2013, with an exposure of 95 live -days ×118 kg . here, the calculations of the mirror electron scattering rate in liquid xenon take into account the shielding effects from mirror dark matter captured within the earth. annual and diurnal modulation of the dark matter flux and atomic shell effects in xenon are also accounted for. having found no evidence for an electron recoil signal induced by mirror dark matter interactions we place an upper limit on the kinetic mixing parameter over a range of local mirror electron temperatures between 0.1 and 0.9 kev. this limit shows significant improvement over the previous experimental constraint from orthopositronium decays and significantly reduces the allowed parameter space for the model. we exclude mirror electron temperatures above 0.3 kev at a 90% confidence level, for this model, and constrain the kinetic mixing below this temperature. | first direct detection constraint on mirror dark matter kinetic mixing using lux 2013 data |
using a fundamental discrete symmetry, zn, we construct a two-axion model with the qcd axion solving the strong-c p problem, and an ultralight axion (ula) with mula≈1 0-22 ev providing the dominant form of dark matter (dm). the ula is light enough to be detectable in cosmology from its imprints on structure formation, and may resolve the small-scale problems of cold dm. the necessary relative dm abundances occur without fine-tuning in constructions with decay constants fula∼1017 gev , and fqcd∼1011 gev . an example model achieving this has n =24 , and we construct a range of other possibilities. we compute the ula couplings to the standard model, and discuss prospects for direct detection. the qcd axion may be detectable in standard experiments through the e →.b → and g g ∼ couplings. in the simplest models, however, the ula has identically zero coupling to both g g ∼ of qcd and e →.b → of electromagnetism due to vanishing electromagnetic and color anomalies. the ula couples to fermions with strength g ∝1 /fula. this coupling causes spin precession of nucleons and electrons with respect to the dm wind with period t ∼ months. current limits do not exclude the predicted coupling strength, and our model is within reach of the casper-wind experiment, using nuclear magnetic resonance. | an ultralight pseudoscalar boson |
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