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8,300 | An Interactive NeXTstep Interface to a Fortran Code for Solving Coupled Differential Equations | nucl-th | This paper describes a user-friendly frontend to a Fortran program that
integrates coupled nonlinear ordinary differential equations. The user
interface is built using the NeXTstep Interface Builder, together with a
public-domain graphical palette for displaying intermediate and final results.
In running the code for a... | physics |
8,301 | Quark Delocalization, Color Screening, and Nuclear Intermediate Range Attraction | nucl-th | We consider the effect of including quark delocalization and color screening,
in the nonrelativistic quark cluster model, on baryon-baryon potentials and
phase shifts. We find that the inclusion of these additional effects allows a
good qualitative description of both. | physics |
8,302 | Quadrupole Contribution to Two Neutron Removal in Heavy Ion Collisions | nucl-th | In this report, electric quadrupole corrections to the two neutron removal
cross section measured in heavy ion collisions are estimated for $^{197}$Au and
$^{59}$Co targets. The quadrupole process is assumed to proceed primarily
through excitation of the giant isovector quadrupole resonance, which then
decays by neutro... | physics |
8,303 | Resonances in $Λd$ Scattering and the $Σ$-hypertriton | nucl-th | Using separable $NN$ and $\Lambda N$-$\Sigma N$ potentials in the Faddeev
equations, we have demonstrated that the predicted enhancement in the $\Lambda
d$ cross section near the $\Sigma d$ threshold is associated with resonance
poles in the scattering amplitude. The positions of these poles, on the second
Riemann shee... | physics |
8,304 | Anatomy of the Soft-Photon Approximation in Hadron-Hadron Bremsstrahlung | nucl-th | A modified Low procedure for constructing soft-photon amplitudes has been
used to derive two general soft-photon amplitudes, a two-s-two-t special
amplitude $M^{TsTts}_{\mu}$ and a two-u-two-t special amplitude
$M^{TuTts}_{\mu}$, where s, t and u are the Mandelstam variables.
$M^{TsTts}_{\mu}$ depends only on the elast... | physics |
8,305 | Saturation in the Nuclear Matter Problem | nucl-th | Once density-dependent meson masses are introduced into the nuclear many-body
problem, conventional mechanisms for saturation no longer operate. We suggest
that a loop correction, essentially the introduction of the axial vector
coupling $g_A(\rho,k)$ as function of density $\rho$ and momentum $k$, can
bring about satu... | physics |
8,306 | Relativistic Corrections to the Triton Binding Energy | nucl-th | The influence of relativity on the triton binding energy is investigated. The
relativistic three-dimensional version of the Bethe-Salpeter equation proposed
by Blankenbecler and Sugar (BbS) is used. Relativistic (non-separable)
one-boson-exchange potentials (constructed in the BbS framework) are employed
for the two-nu... | physics |
8,307 | Riemann's theorem for quantum tilted rotors | nucl-th | The angular momentum, angular velocity, Kelvin circulation, and vortex
velocity vectors of a quantum Riemann rotor are proven to be either (1) aligned
with a principal axis or (2) lie in a principal plane of the inertia ellipsoid.
In the second case, the ratios of the components of the Kelvin circulation to
the corresp... | physics |
8,308 | Effects of Octupole Vibrations on Quasiparticle Modes of Excitation in Superdeformed $^{193}$Hg | nucl-th | A particle-vibration coupling calculation based on the RPA and the cranked
shell model has been carried out for superdeformed rotational bands in
$^{193}$Hg. The result suggests that properties of single-particle motions in
superdeformed nuclei may be significantly affected by coupling effects with
low-frequency octupo... | physics |
8,309 | Monte Carlo methods for the nuclear shell model | nucl-th | We present novel Monte Carlo methods for treating the interacting shell model
that allow exact calculations much larger than those heretofore possible. The
two-body interaction is linearized by an auxiliary field; Monte Carlo
evaluation of the resulting functional integral gives ground-state or thermal
expectation valu... | physics |
8,310 | Skyrmions and the Nuclear Force | nucl-th | The derivation of the nucleon-nucleon force from the Skyrme model is
reexamined. Starting from previous results for the potential energy of
quasistatic solutions, we show that a calculation using the Born-Oppenheimer
approximation properly taking into account the mixing of nucleon resonances,
leads to substantial centr... | physics |
8,311 | Transverse response functions in the $Δ$-resonance region | nucl-th | We calculate transverse response functions for quasi-elastic electron
scattering at high momentum transfers in a relativistic Hartree approximation
in configuration space. We treat the excitation of the $\Delta$ resonance using
its free mass and width. Good agreement with experiment is found in the dip
region. | physics |
8,312 | Quartets of superdeformed bands and supersymmetry breaking | nucl-th | We examine the prediction of supersymmetric quantum mechanics that bands with
identical gamma-ray energies occur in quartets. The experimental data suggest
that this scenario is actually realized in nature. In the $A=150$ mass region,
four known pairs of isospectral bands can be grouped in two quartets, while
there are... | physics |
8,313 | Electromagnetic Decays of Hyperons (II) | nucl-th | Excited negative parity hyperon masses are calculated in a chiral bag model
in which the pion and the kaon fields are treated as perturbations. We also
calculate the hadronic widths of $\lama$ and $\lamb$ as well as the coupling
constants of the lightest $I=0$ excited hyperon to the meson-baryon channels,
and discuss h... | physics |
8,314 | Coalescence, Percolation and Nuclear Multifragmentation | nucl-th | We show that the coalescence model for fragment formation leads to an
approximate site percolation model. Features characteristic of a percolation
model also appear in microscopic models of disassembly. | physics |
8,315 | Sum Rule Description of Color Transparency | nucl-th | The assumption that a small point-like configuration does not interact with
nucleons leads to a new set of sum rules that are interpreted as models of the
baryon-nucleon interaction. These models are rendered semi-realistic by
requiring consistency with data for cross section fluctuations in proton-proton
diffractive c... | physics |
8,316 | Atomic Parity Nonconservation: Electroweak Parameters and Nuclear Structure | nucl-th | There have been suggestions to measure atomic parity nonconservation (PNC)
along an isotopic chain, by taking ratios of observables in order to cancel
complicated atomic structure effects. Precise atomic PNC measurements could
make a significant contribution to tests of the Standard Model at the level of
one loop radia... | physics |
8,317 | Self-consistent anisotropic oscillator with cranked angular and vortex velocities | nucl-th | The Kelvin circulation is the kinematical Hermitian observable that measures
the true character of nuclear rotation. For the anisotropic oscillator, mean
field solutions with fixed angular momentum and Kelvin circulation are derived
in analytic form. The cranking Lagrange multipliers corresponding to the two
constraint... | physics |
8,318 | $q^2$-Dependence of Meson Mixing in Few-Body Charge Symmetry Breaking: $π^o-η$ Mixing to One Loop in Chiral Perturbation Theory | nucl-th | It is pointed out that the meson mixing matrix elements usually considered
responsible for the bulk of the observed few-body charge symmetry breaking are
naturally $q^2$-dependent in QCD. For $\pi^o-\eta$ mixing, using the usual
representation of the pseudoscalar fields, the leading $q^2$ dependence can be
explicitly c... | physics |
8,319 | On the pion-nucleon coupling constant | nucl-th | In view of persisting misunderstanding about the determination of the
pion-nucleon coupling constants in the Nijmegen multienergy partial-wave
analyses of pp, np, and pbar-p scattering data, we present additional
information which may clarify several points of discussion. We comment on
several recent papers addressing ... | physics |
8,320 | Hot Nuclear Matter : A Variational Approach | nucl-th | We develop a nonperturbative technique in field theory to study properties of
infinite nuclear matter at zero temperature as well as at finite temperatures.
Here we dress the nuclear matter with off-mass shell pions. The techniques of
thermofield dynamics are used for finite temperature calculations. Equation of
state ... | physics |
8,321 | Relativistic Mean Field Calculations of $Λ$ and $Σ$ Hypernuclei | nucl-th | Single--particle spectra of $\Lambda $ and $\Sigma $ hypernuclei are
calculated within a relativistic mean--field theory. The hyperon couplings used
are compatible with the $\Lambda $ binding in saturated nuclear matter,
neutron-star masses and experimental data on $\Lambda $ levels in hypernuclei.
Special attention is... | physics |
8,322 | Comparison of potential models with the pp scattering data below 350 MeV | nucl-th | We calculate the chi**2 of various NN potential models with respect to the pp
scattering data. We find that only the potential models which were explicitly
fitted to the pp data give a reasonable description of these data. Most models
give a pretty large chi**2 on the very low-energy pp data, due to incorrect 1S0
phase... | physics |
8,323 | The Nuclear Response in Delta-Isobar Region in the ($^3\!$He,t) Reaction | nucl-th | The excitation of a $\Delta$-isobar in a finite nucleus in charge--exchange
($^3\!$He,t) reaction is discussed in terms of a nuclear response function. The
medium effects modifying a $\Delta$- and a pion propagation were considered for
a finite size nucleus. The Glauber approach has been used for distortion of a
$^3\!$... | physics |
8,324 | Exact 1-Fermion Loop Contributions in 1+1 Dimensional Solitons | nucl-th | We find solutions to the 1+1 dimensional scalar-only linear sigma model. A
new method is used to compute 1-fermion loop contributions exactly and
agreement with published results employing other methods is excellent. A
renormalization scheme which differs from that commonly used in such
calculations but similar to that... | physics |
8,325 | Relativistic Nuclear Matter with Self-Consistent Correlation Energy | nucl-th | We study relativistic nuclear matter in the $\sigma - \omega$ model including
the ring-sum correlation energy. The model parameters are adjusted
self-consistently to give the canonical saturation density and binding energy
per nucleon with the ring energy included. Two models are considered,
mean-field-theory where we ... | physics |
8,326 | Microscopic Origin of Quantum Chaos in Rotational Damping | nucl-th | The rotational spectrum of $^{168}$Yb is calculated diagonalizing different
effective interactions within the basis of unperturbed rotational bands
provided by the cranked shell model. A transition between order and chaos
taking place in the energy region between 1 and 2 MeV above the yrast line is
observed, associated... | physics |
8,327 | Poisson and Porter-Thomas Fluctuations in off-Yrast Rotational Transitions | nucl-th | Fluctuations associated with stretched E2 transitions from high spin levels
in nuclei around $^{168}$Yb are investigated by a cranked shell model extended
to include residual two-body interactions. It is found that the gamma-ray
energies behave like random variables and the energy spectra show the Poisson
fluctuation, ... | physics |
8,328 | Hyperfine Populations Prior to Muon Capture | nucl-th | It is shown that the 1S level hyperfine populations prior to muon capture
will be statistical when either target or beam are unpolarised independent of
the atomic level at which the hyperfine interaction becomes appreciable. This
assertion holds in the absence of magnetic transitions during the cascade and
is true beca... | physics |
8,329 | Cross Section Fluctuations and Chaoticity in Heavy-Ion Dynamics | nucl-th | Cross section fluctuations in nuclear scattering are briefly reviewed in
order to show the main important features. Then chaotic scattering is
introduced by means of a very simple model. It is shown that chaoticity
produces the same kind of irregular fluctuations observed in light heavy--ion
collisions. The transition ... | physics |
8,330 | Chiral colour-dielectric model with perturbative quantum pions and gluons | nucl-th | Pionic contributions to static nucleon properties are calculated in a chiral
extension of the colour-dielectric model. The pion field and residual gluon
field are treated perturbatively. It is shown that with a simple choice for the
energy of the scalar confining field and in the chiral limit, the system of
equations d... | physics |
8,331 | Colour Transparency in Hadronic Basis | nucl-th | The dynamics of nuclear transparency in hard nuclear reactions is studied by
an expansion of the correlator of the hard scattering operator on a hadronic
basis. Colour transparency appears as an effect of interference between the
amplitudes corresponding to the final state interaction of different
intermediate baryonic... | physics |
8,332 | High-energy pion-nucleus elastic scattering | nucl-th | We investigate theoretical approaches to pion--nucleus elastic scattering at
high energies (300 $\le T_\pi \le$ 1 GeV). A ``model--exact'' calculation of
the lowest--order microscopic optical model, carried out in momentum space and
including the full Fermi averaging integration, a realistic off--shell
pion--nucleon sc... | physics |
8,333 | Microscopic approach to pion-nucleus dynamics | nucl-th | Elastic scattering of pions from finite nuclei is investigated utilizing a
contemporary, momentum--space first--order optical potential combined with
microscopic estimates of second--order corrections. The calculation of the
first--order potential includes:\ \ (1)~full Fermi--averaging integration
including both the de... | physics |
8,334 | Dynamics of antibaryon-baryon annihilation in the Skyrme model | nucl-th | We examine the dynamics of a baryon number zero lump in the Skyrme picture,
as a model for annihilation in the $\bar{N}N$ system. We find that radiation
propagates at the causal limit as a localized pulse and that the linearized
theory gives a good approximation. Both of these results are contrary to
findings in the Si... | physics |
8,335 | Chaotic Behavior in Warm Deformed Nuclei Induced by Residual Two-Body Interactions | nucl-th | Band mixing calculations in rapidly rotating well-deformed nuclei are
presented, investigating the properties of energy levels and rotational
transitions as a function of excitation energy. Substantial fragmentation of E2
transitions is found for $E_x \gsim$ 800 keV above yrast, which represents the
onset of rotational... | physics |
8,336 | Electromagnetic Dissociation of Nuclei in Heavy-Ion Collisions | nucl-th | Large discrepancies have been observed between measured Electromagnetic
Dissociation(ED) cross sections and the predictions of the semiclassical
Weiz\"acker-Williams-Fermi(WWF) method. In this paper, the validity of the
semiclassical approximation is examined. The total cross section for
electromagnetic excitation of a... | physics |
8,337 | The Momentum Dependence of the $ρ-ω$ Mixing Amplitude in a Hadronic Model | nucl-th | We calculate the momentum dependence of the $\rho-\omega$ mixing amplitude in
a purely hadronic model. The basic assumption of the model is that the mixing
amplitude is generated by $N{\bar{N}}$ loops and thus driven entirely by the
neutron-proton mass difference. The value of the amplitude at the
$\omega$-meson point ... | physics |
8,338 | Neutron matter - Quark matter phase transition and Quark star | nucl-th | We consider the neutron matter quark matter phase transition along with
possible existence of hybrid quark stars. The equation of state for neutron
matter is obtained using a nonperturbative method with pion dressing of the
neutron matter and an analysis similar to that of symmetric nuclear matter. The
quark matter sec... | physics |
8,339 | Pion interaction with the trinucleon up to the eta production threshold | nucl-th | Pion elastic, charge exchange scattering and induced eta production on the
trinucleon systems are investigated in a coupled-channels approach in momentum
space with Fadeev wave functions. The channel $\pi N \rightarrow \eta N$ is
included using an isobar model with S-, P-, and D-wave resonances. While the
coherent reac... | physics |
8,340 | Revealing Intermittency in Nuclear Multifragmentation with 4$\PI$ Detectors | nucl-th | The distortion on the intermittency signal, due to detection efficiency and
to the presence of pre--equilibrium emitted particles, is studied in a
schematic model of nuclear multi- fragmentation. The source of the
intermittency signal is modeled with a percolating system. The efficiency is
schematized by a simple funct... | physics |
8,341 | Near-Threshold Production of $η$-Mesons | nucl-th | It is shown that the striking energy variation in the $p\, d \rightarrow
\mbox{$^{\, 3}{\rm He}$}\, \eta$ cross section near threshold is probably due
to a final state interaction associated with a large (complex) $\eta
-\mbox{$^{3}{\rm He}$}$ scattering length. The consequences of this hypothesis
are studied for the p... | physics |
8,342 | A Quark Model of Antilambda-Lambda Production in Pbar-P Interactions | nucl-th | A quark model which includes both scalar and vector contributions to the
reaction mechanism is used in a DWBA calculation of total and differential
cross-sections, polarizations, and spin correlation coefficients for the
reaction $\bar p p \rightarrow \bar \Lambda \Lambda$ at laboratory momenta from
threshold to 1.92 G... | physics |
8,343 | Correlation measurements in high-multiplicity events | nucl-th | Requirements for correlation measurements in high--multiplicity events are
discussed. Attention is focussed on detection of so--called hot spots,
two--particle rapidity correlations, two--particle momentum correlations (for
quantum interferometry) and higher--order correlations. The signal--to--noise
ratio may become l... | physics |
8,344 | Chemical equilibration of $π$, $ρ$ and $ω$ mesons in ultra--relativistic nuclear collisions | nucl-th | I estimate the degree of local chemical equilibration for $\pi$, $\rho$ and
$\omega$ mesons in ultra--relativistic nuclear collisions. The $\pi$ and $\rho$
mesons remain near chemical equilibrium in all cases, while the $\omega$ meson
density is typically 30--50\% higher than the equilibrium value for O+Ag
collisions a... | physics |
8,345 | Analysis techniques for high-multiplicity collisions | nucl-th | I discuss methods for identifying and quantifying phase transitions in
particle collisions, concentrating on two techniques for use in
ultra-relativistic nuclear collisions. The first technique is to use rapidity
correlation measurements to determine the correlation length, while the second
is to use the transverse mas... | physics |
8,346 | Extracting Nuclear Transparency from p-A Cross sections | nucl-th | We study nuclear structure effects on the transparency in high transverse
momentum $(p,2p)$ and $(e,e'p)$ reactions. We show that in the DWIA-eikonal
approximation, even when correlations are included, one can get a factorized
expression for the transparency. This depends only on the average nucleon
density $\rho(r)$ a... | physics |
8,347 | Relativistic Ring-Diagram Nuclear Matter Calculations | nucl-th | A relativistic extension of the particle-particle hole-hole ring-diagram
many-body formalism is developed by using the Dirac equation for
single-particle motion in the medium. Applying this new formalism, calculations
are performed for nuclear matter. The results show that the saturation density
is improved and the equ... | physics |
8,348 | Exact Solutions of Model Hamiltonian Problems with Effective Interactions | nucl-th | We demonstrate with soluble models how to employ the effective Hamiltonian
approach of Lee and Suzuki to obtain all the exact eigenvalues of the full
Hamiltonian. We propose a new iteration scheme to obtain the effective
Hamiltonian and demonstrate its convergence properties. | physics |
8,349 | Momentum distribution of fragments in heavy ion reactions: Dependence on the stochastic collision process | nucl-th | Momentum distribution of fragments produced in 12C+12C reaction at 28.7
MeV/nucleon is analyzed with antisymmetrized version of molecular dynamics
(AMD). Calculations are made for several cases of stochastic collisions and the
projectile fragmentation peak in momentum distribution is reproduced by the
incorporation of ... | physics |
8,350 | Correlation between the quenching of total GT+ strength and the increase of E2 strength | nucl-th | Relations between the total beta+ Gamow-Teller (GT+) strength and the E2
strength are further examined. It is found that in shell-model calculations for
N=Z nuclei, in which changes in deformation are induced by varying the
single-particle energies, the total GT+ or GT- strength decreases monotonically
with increasing ... | physics |
8,351 | Shadowing in Deuterium | nucl-th | We calculate nuclear shadowing in lepton-deuteron deep inelastic scattering,
which arises from the double scattering of the virtual photon from both
nucleons in the deuteron. The total correction to the deuteron structure
function is found to be less than about 1\% at small Bjorken-x, but dependent
on the model deutero... | physics |
8,352 | Role of Vector Mesons in High-Q^2 Lepton-Nucleon Scattering | nucl-th | The possible role played by vector mesons in inclusive deep inelastic
lepton-nucleon scattering is investigated. In the context of the convolution
model, we calculate self-consistently the scaling contribution to the nucleon
structure function using the formalism of time-ordered perturbation theory in
the infinite mome... | physics |
8,353 | The Astrophysical S-Factor of the Reaction $^7$be(p,$γ$)$^8$B in the Direct Capture Model | nucl-th | The astrophysical $S$-factor for the reaction $^7$Be(p,$\gamma$)$^8$B up to
an energy of 2~MeV (c.m.) and the capture cross section of
$^7$Li(n,$\gamma$)$^8$Li up to 1~MeV (c.m.) are calculated using the Direct
Capture model (DC). Both calculations are in good agreement with experimental
data. | physics |
8,354 | Nucleon-Nucleon Potentials in Comparison: Physics or Polemics? | nucl-th | Guided by history, we review the major developments concerning realistic
nucleon-nucleon (NN) potentials since the pioneering work by Kuo and Brown on
the effective nuclear interaction. Our main emphasis is on the physics
underlying various models for the NN interaction developed over the past
quarter-century. We comme... | physics |
8,355 | Comment on Shadow model for sub-barrier fusion applied to light systems | nucl-th | We demonstrate that the cross sections derived from the "shadow model" for
reactions between light nuclei disagree with low-energy laboratory data and
exhibit unphysical behavior at energies below those for which data exist. As a
consequence, the large thermonuclear reaction rates obtained by Scalia and
Figuera [Phys. ... | physics |
8,356 | Self-Similarity and Scaling Behavior in Nuclear Collision | nucl-th | A simple model is used to explore issues related to self-similarity,
intermittency and scaling behavior in nuclear collisions. Both scaled factorial
moments and power moments are considered in the investigation of these
features. The product mass yields are used to construct probability
distributions and generalized Re... | physics |
8,357 | Geometry, Scaling and Universality in the Mass Distributions in Heavy Ion Collisions | nucl-th | Various features of the mass yields in heavy ion collisions are studied. The
mass yields are discussed in terms of iterative one dimensional discrete maps.
These maps are shown to produce orbits for a monomer or for a nucleus which
generate the mass yields and the distribution of cluster sizes. Simple
Malthusian dynami... | physics |
8,358 | Medium corrections to the tensor interaction in nuclei: Energy difference of T=1 and T=0 J=0- states in 16O | nucl-th | It has been shown in the past that in a shell model calculation, restricted
to 1Hbar*Omega 1p-1h configurations, the energy splitting between the lowest
J=0-, T=0 and J=0-, T=1 states in 16O is mainly due to the tensor component of
the nucleon-nucleon interaction. In this work, we extend the calculation to
include 3Hba... | physics |
8,359 | Relativistic and Nuclear Structure Effects in Parity-Violating Quasielastic Electron Scattering | nucl-th | The parity violating longitudinal asymmetry ${\cal A}$ is calculated for
quasielastic electron scattering. We use a variety of relativistic mean field
models for the response of nuclear matter and $^{12}$C at a momentum transfer
of q=550 MeV/c. Relativistic effects from a reduced nucleon mass, RPA
correlations and vacu... | physics |
8,360 | Can Plasma Scattering Mimic a Cosmological Red-Shift? | nucl-th | We investigate the extent to which the scattering of light from plasma
fluctuations can mimic a cosmological red-shift, as has been suggested by Wolf
et al. A plasma model for the plasma structure function results in a spectrum
of scattered light very different from that associated with a constant
red-shift, implying t... | physics |
8,361 | The Beta Decay of 44V | nucl-th | We have calculated the $\beta^+$ decay of the proton rich nuclei $^{44}$V in
a full fp-shell valence space. We obtain a theoretical half-life of 71~ms
compared with the experimental value t$_{1/2}$ = 90 $\pm$ 25 ms. Besides, we
make predictions for the Gamow-Teller strength functions corresponding to the
decays of the ... | physics |
8,362 | NN Core Interactions and Differential Cross Sections from One Gluon Exchange | nucl-th | We derive nonstrange baryon-baryon scattering amplitudes in the
nonrelativistic quark model using the ``quark Born diagram" formalism. This
approach describes the scattering as a single interaction, here the
one-gluon-exchange (OGE) spin-spin term followed by constituent interchange,
with external nonrelativistic baryo... | physics |
8,363 | The $^3S_1-^3D_1$ effective-range parameters of some realistic nucleon-nucleon potentials | nucl-th | We consider the $P$- and $Q$-shape parameters in the eigenphase and `bar'
phase shift representations for the two Reid potentials and the more recent
Moscow potential. The values of these parameters were obtained from integrals
of the zero-energy wave function in a similar manner to that for the effective
range. Such e... | physics |
8,364 | Model for the Quasifree Polarization-Transfer Measurements in the (p,n) reaction at 495 MeV | nucl-th | The recent (p,n) polarization transfer experiments at LAMPF are explained in
terms of a dropping rho-meson mass in the medium. | physics |
8,365 | Determination of two-body potentials from n-body spectra | nucl-th | We show how the two-body potential may be uniquely determined from n-body
spectra where the hypercentral approximation is valid. We illustrate this by
considering an harmonic oscillator potential which has been altered by changing
the energy or normalisation constant of the ground state of the n-body system
and finding... | physics |
8,366 | Modeling Complex Nuclear Spectra - Regularity versus Chaos | nucl-th | A statistical analysis of the spectrum of two particle - two hole doorway
states in a finite nucleus is performed. On the unperturbed mean-field level
sizable attractive correlations are present in such a spectrum. Including
particle-hole rescattering effects via the residual interaction introduces
repulsive dynamical ... | physics |
8,367 | Pre-equilibrium dileptons look thermal | nucl-th | The dilepton mass distribution from pre-equilibrium matter in
ultrarelativistic nuclear collisions is indistinguishable from a thermally
produced distribution. | physics |
8,368 | The Coulomb Sum and Proton-Proton Correlations in Few-Body Nuclei | nucl-th | In simple models of the nuclear charge operator, measurements of the Coulomb
sum and the charge form factor of a nucleus directly determine the
proton-proton correlations. We examine experimental results obtained for
few-body nuclei at Bates and Saclay using models of the charge operator that
include both one- and two-... | physics |
8,369 | Particle-particle correlations and the space-time structure of heavy ion collisions | nucl-th | The present status of the use of two-particle intensity interferometry as a
diagnostic tool to study the space-time dynamics of intermediate energy heavy
ion collisions is examined. Calculations for the two-proton and two-pion
correlation functions are presented and compared to experiment. The
calculations are based on... | physics |
8,370 | M1 Resonances in Unstable Magic Nuclei | nucl-th | Within a microscopic approach which takes into account RPA configurations,
the single-particle continuum and more complex $1p1h\otimes phonon$
configurations isoscalar and isovector M1 excitations for the unstable nuclei
${56,78}$Ni and ${100,132}$Sn are calculated. For comparison, the
experimentally known M1 excitatio... | physics |
8,371 | Generalized $^3P_0$ and $^3S_1$ Annihilation Potentials for $\bar{p}p$ Decay into Two Mesons based on a Simple Quark Model | nucl-th | Within the quark model a generalization is proposed of the commonly used
annihilation potential to describe antiproton-proton annihilation into two
mesons, the so-called $^3P_0$ and $^3S_1$ mechanisms. This generalized
potential treats the two mechanisms in a more symmetric way, has additional
angular dependence, and r... | physics |
8,372 | Atomic parity nonconservation and neutron radii in cesium isotopes | nucl-th | The interpretation of future precise experiments on atomic parity violation
in terms of parameters of the Standard Model could be hampered by uncertainties
in the atomic and nuclear structure. While the former can be overcome by
measurement in a series of isotopes, the nuclear structure requires knowledge
of the neutro... | physics |
8,373 | Off-shell Behavior of the $π\!-\!η$ Mixing Amplitude | nucl-th | We extend a recent calculation of the momentum dependence of the
$\rho-\omega$ mixing amplitude to the pseudoscalar sector. The $\pi\!-\!\eta$
mixing amplitude is calculated in a hadronic model where the mixing is driven
by the neutron-proton mass difference. Closed-form analytic expressions are
presented in terms of a... | physics |
8,374 | The Onset of Color Transparency in $(e,e'p)$ Reactions on Nuclei | nucl-th | Quantum filtering of the ejectile wave packet from hard $ep$ scattering on
bound nucleons puts stringent constraints on the onset of color transparency in
$(e,e'p)$ reactions in nuclei at moderate energies. Based on
multiple-scattering theory, we derive a novel formula for nuclear transparency
and discuss its energy de... | physics |
8,375 | The neutron halo of $^6$He in a microscopic model | nucl-th | The two--neutron separation energy of $^6$He has been reproduced for the
first time in a realistic parameter--free microscopic multicluster model
comprising the $\alpha +n+n$ and $t+t$ clusterizations, with $\alpha$ cluster
breathing excitations included. The contribution of the $t+t$ channel is
substantial. A very thi... | physics |
8,376 | Relation between the phenomenological interactions of the algebraic cluster model and the effective two--nucleon forces | nucl-th | We determine the phenomenological cluster--cluster interactions of the
algebraic model corresponding to the most often used effective two--nucleon
forces for the $^{16}$O + $\alpha$ system. | physics |
8,377 | The response of non-relativistic confined systems | nucl-th | We study the non-relativistic response of a 'diquark' bound by confining
forces, for which perturbation theory in the interaction fails. As
non-perturbative alternatives we consider the Gersch-Rodriguez-Smith theory and
a summation method. We show that, contrary to the case of singular repulsive
forces, the GRS theory ... | physics |
8,378 | Ghost Poles in the Nucleon Propagator: Vertex Corrections and Form Factors | nucl-th | Vertex corrections are taken into account in the Schwinger-Dyson equation for
the nucleon propagator in a relativistic field theory of fermions and mesons.
The usual Hartree-Fock approximation for the nucleon propagator is known to
produce the appearance of complex (ghost) poles which violate basic theorems of
quantum ... | physics |
8,379 | Orbital M1 versus E2 strength in deformed nuclei: A new energy weighted sum rule | nucl-th | Within the unified model of Bohr and Mottelson we derive the following linear
energy weighted sum rule for low energy orbital 1$^+$ excitations in even-even
deformed nuclei $$S_{\rm LE}^{\rm lew} (M_1^{\rm orb}) \cong (6/5) \epsilon
(B(E2; 0^+_1 \rightarrow 2_1^+ K=0)/Z e^2<r^2>^2) \mu^2_N$$ with B(E2) the E2
strength ... | physics |
8,380 | Left-Right Asymmetry in $\bar{p}p \rightarrow π^- π^+$ | nucl-th | Results for d$\sigma$/d$\Omega$ and $A_N$ in the reaction $\bar{p}p
\rightarrow \pi^- \pi^+$ are predicted by a simple quark model. They are
compared to recent experimental data from LEAR, as well as to previous
predictions from nucleon-exchange models. At low energy the quark model does
better than the nucleon-exchang... | physics |
8,381 | Angular Momentum Analysis of Spin 1/2 x 1/2 Scattering including Singlet-Triplet Mixing | nucl-th | The angular momentum (partial wave) reduction of the Lippmann--Schwinger
equation describing the interaction of two spin 1/2 particles is extended to
the case in which the spin singlet and triplet states are coupled. A straight
forward method for obtaining the angular momentum decomposition of the general
potential is ... | physics |
8,382 | Critical test of multi-{\it j} supersymmetries from magnetic moment measurements | nucl-th | Magnetic moment measurements in odd nuclei directly probe the distribution of
fermion states and hence provide one of the most critical tests for multi-$j$
supersymmetries in collective nuclei. Due to complexity of calculations and
lack of data, such tests have not been performed in the past. Using the
Mathematica soft... | physics |
8,383 | Probing Hadronic Structure with The Decay $Δ\rightarrow Nl^+l^-$ | nucl-th | We compute the branching ratio for $\Delta\rightarrow Ne^+e^-$ and
$\Delta\rightarrow N\mu^+\mu^-$ in chiral perturbation theory and find that
both decays should be observable at CEBAF. With sufficiently low thresholds on
the $e^+e^-$ invariant mass a branching ratio of $\sim 10^{-5}$ may be observed
for $\Delta\righta... | physics |
8,384 | Nuclear effects in Deep Inelastic Scattering of polarized electrons off polarized 3He and the neutron spin structure functions | nucl-th | It is shown that the nuclear effects playing a relevant role in Deep
Inelastic Scattering of polarized electrons by polarized $^3$He are mainly
those arising from the effective proton and neutron polarizations generated by
the $S'$ and $D$ waves in $^3$He. A simple and reliable equation relating the
neutron, $g_1^n$, a... | physics |
8,385 | Quantum theory of large amplitude collective motion and the Born-Oppenheimer method | nucl-th | We study the quantum foundations of a theory of large amplitude collective
motion for a Hamiltonian expressed in terms of canonical variables. In previous
work the separation into slow and fast (collective and non-collective)
variables was carried out without the explicit intervention of the Born
Oppenheimer approach. ... | physics |
8,386 | Dirac Hartree-Fock for Finite Nuclei Employing realistic Forces | nucl-th | We discuss two different approximation schemes for the self-consistent
solution of the {\it relativistic} Brueckner-Hartree-Fock equation for finite
nuclei. In the first scheme, the Dirac effects are deduced from corresponding
nuclear matter calculations, whereas in the second approach the local-density
approximation i... | physics |
8,387 | On the Spectacular Large Asymmetry in $\pbarppipi$ and $\pbarpKK$ Reactions} | nucl-th | An illustrative analysis is presented to show the origin of the
energy-independent maximal asymmetry observed for wide ranges of angles in the
reactions $\pbarppipi$ and $\pbarpKK$. % The general nature of our simple
relation between helicity -flip and -nonflip partial wave amplitudes enforces
the notion that % these f... | physics |
8,388 | Exclusive Hadronic Reactions at High $Q^2$ ($90\degree$) and Polarization Phenomena, An Experimental Proposal} | nucl-th | Arguments are presented for the expected behaviour of $\piNpiN$ scattering
and the $\pbarppipi$ reaction at high energy and large scattering angles. % The
annihilation reaction has close to maximal asymmetry ($\approx$ 1) for $p_{lab}
\siml $ 2.2 GeV/c. % As will be presented for fixed (90$\degree$) angle this
large as... | physics |
8,389 | The Quasi-Elastic Nuclear Response | nucl-th | We explore the nuclear responses at intermediate energies, particularly in
the spin longitudinal and spin transverse isovector channels, within the
continuum random phase approximation framework. We also employ an extension of
the standard random phase approximation to account for the spreading width of
the single part... | physics |
8,390 | Comment on Neutron-Proton Spin-Correlation Parameter A_{ZZ} at 68 Mev | nucl-th | We present two arguments indicating that the large value for the $\epsilon_1$
mixing parameter at 50 MeV, which the Basel group extracted from their recent
$A_{zz}$ measurement, may be incorrect. First, there are nucleon-nucleon (NN)
potentials which predict the $\epsilon_1$ at 50 MeV substantially below the
Basel valu... | physics |
8,391 | Correlations in Nuclei: Self-Consistent Treatment and the BAGEL Approach | nucl-th | An approach is presented which allows a self-consistent description of the
fragmentation of single-particle strength for nucleons in finite nuclei
employing the Greens function formalism. The self-energy to be considered in
the Dyson equation for the single-particle Greens function contains all terms
of first (Hartree-... | physics |
8,392 | Light front dynamics and the binding correction | nucl-th | It is shown that the nuclear binding correction in deep inelastic lepton
scattering is essentially the same in light front and instant form
representations. Some contradicting papers are discussed. | physics |
8,393 | Gauge Invariance and the Electromagnetic Current of Composite Pions | nucl-th | The Global Color-symmetry Model of QCD is extended to deal with a background
electromagnetic field and the associated conserved current is identified for
composite $\bar{q}q$ pion modes of the model. Although the analysis is limited
to tree level in the bilocal fields that bosonize the model, the identified
photon-pion... | physics |
8,394 | Nambu-Jona-Lasinio Models Beyond the Mean Field Approximation | nucl-th | Inspired by the model of Nambu and Jona-Lasinio, various Lagrangians are
considered for a system of interacting quarks. Employing standard techniques of
many-body theory, the scalar part of the quark self-energy is calculated
including terms up to second-order in the interaction. Results obtained for the
single-particl... | physics |
8,395 | The Pion in Electromagnetic and Weak Neutral Current Nuclear Response Functions | nucl-th | The impact of pionic correlations and meson--exchange currents in determining
the (vector) response functions for electroweak quasielastic lepton scattering
from nuclei is discussed. The approach taken builds on previous work where the
Fermi gas model is used to maintain consistency in treating forces and currents
(gau... | physics |
8,396 | Collective Modes in a Slab of Interacting Nuclear Matter: The effects of finite range interactions | nucl-th | We consider a slab of nuclear matter and investigate the collective
excitations, which develop in the response function of the system. We introduce
a finite-range realistic interaction among the nucleons, which reproduces the
full G-matrix by a linear combination of gaussian potentials in the various
spin-isospin chann... | physics |
8,397 | Role of heavy-meson exchange in pion production near threshold | nucl-th | Recent calculations of $s$-wave pion production have severely underestimated
the accurately known $pp\rightarrow pp\pi^0$\ total cross section near
threshold. In these calculations, only the single-nucleon axial-charge operator
is considered. We have calculated, in addition to the one-body term, the
two-body contributi... | physics |
8,398 | The Delta-Hole model at Finite Temperature | nucl-th | The spectral function of pions interacting with a gas of nucleons and
Delta-33-resonances is investigated using the formalism of Thermo Field
Dynamics. After a discussion of the zero Delta-width approximation at finite
temperature, we take into account a constant width of the resonance. Apart from
a full numerical calc... | physics |
8,399 | Diagonalization of full finite temperature Green's function by quasi-particles | nucl-th | For thermal systems, standard perturbation theory breaks down because of the
absence of stable, observable asymptotic states. We show, how the introduction
of {\it statistical} quasi-particles (stable, but not observable) gives rise to
a consistent description. Statistical and spectral information can be cleanly
separa... | physics |
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