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nucl-th/9307014
Calculation of the properties of the rotational bands of $^{155,157}$Gd
We reexamine the long-standing problem of the microscopic derivation of a particle-core coupling model. We base our research on the Klein-Kerman approach, as amended by D\"onau and Frauendorf. We describe the formalism to calculate energy spectra and transition strengths in some detail. We apply our formalism to the ro...
1993-07-14
2008-11-26
[ "nucl-th" ]
Pavlos Protopapas, Abraham Klein, and Niels R. Walet
nucl-th/9307012
Effects of meson-exchange currents on the $(\protect\vec{e},e'p)$ structure functions
The response functions for the unpolarized $(e,e'p)$ and polarized $(\vec{e},e'p)$ reaction are calculated for medium-heavy nuclei under quasifree conditions. The formalism presented here incorporates two-body currents related to meson-exchange and the $\Delta (1232)$ excitation. The final-state interaction of the outg...
1993-07-13
2008-11-26
[ "nucl-th" ]
V. Van der Sluys, J. Ryckebusch and M. Waroquier
nucl-th/9307011
Space-time Structure of Initial Parton Production in Ultrarelativistic Heavy Ion Collisions
The space and time evolution of initial parton production in ultrarelativistic heavy ion collisions is investigated within the framework of perturbative QCD which includes both initial and final state radiations. Uncertainty principle is used to relate the life time of a radiating parton to its virtuality and momentum....
1993-07-12
2009-10-22
[ "nucl-th", "hep-ph" ]
K. J. Eskola and Xin-Nian Wang
nucl-th/9307010
Triton calculations with the new Nijmegen potentials
Triton properties are calculated using new nucleon-nucleon potentials, which were fit to the world nucleon-nucleon data. All potentials are charge dependent and explicitly incorporate the mass difference between the charged and neutral pions. Three of these models have a nearly optimal chi**2 per degree of freedom and ...
1993-07-09
2009-10-22
[ "nucl-th" ]
J.L. Friar, G.L. Payne, V.G.J. Stoks, and J.J. de Swart
nucl-th/9307007
Color Diffusion and Conductivity in a Quark-Gluon Plasma
Color diffusion is shown to be an important dissipative property of quark-gluon plasmas that rapidly damps collective color modes. We derive the characteristic color relaxation time scale, $t_c\approx (3\alpha_s T \log(m_E/m_M ))^{-1}$, showing its sensitivity to the ratio of the static color electric and magnetic scre...
1993-07-07
2009-10-09
[ "nucl-th" ]
Alexei V. Selikhov and Miklos Gyulassy
nucl-th/9307008
Pion-nucleus reactions in a microscopic transport model
We analyse pion-nucleus reactions in a microscopic transport model of the BUU type, which propagates nucleons, pions, deltas and N(1440)-resonances explicitly in space and time. In particular we examine pion absorption and inelastic scattering cross sections for pion kinetic energies T(pi) =85-315MeV and various target...
1993-07-07
2009-10-22
[ "nucl-th" ]
A. Engel, W. Cassing, U. Mosel, M. Sch\"afer, Gy. Wolf, (Institut f\"ur Theoretische Physik, Universit\"at Giessen D--35392 Giessen, Germany)
nucl-th/9307009
Self-consistent solution of the Schwinger-Dyson equations for the nucleon and meson propagators
The Schwinger-Dyson equations for the nucleon and meson propagators are solved self-consistently in an approximation that goes beyond the Hartree-Fock approximation. The traditional approach consists in solving the nucleon Schwinger-Dyson equation with bare meson propagators and bare meson-nucleon vertices; the correct...
1993-07-07
2008-11-26
[ "nucl-th" ]
M.E. Bracco, A. Eiras, G. Krein and L. Wilets
nucl-th/9307005
Mean Field Approximation to two-subsystems: Examples
Using the Funtional Integrals Formulation is developes a self-consistent mean field expansion to evolution operators of a system composed by two subsystems. This is a general expansion and can be generalized for more of two subsystems, which can be as system composed by fermions and bosons with an interaction between t...
1993-07-06
2007-05-23
[ "nucl-th" ]
S.Cruz-Barrios
nucl-th/9307006
Neutron Stars and Nuclei in the Modified Relativistic Hartree Approximation
We have examined the properties of neutron-rich matter and finite nuclei in the modified relativistic Hartree approximation for several values of the renormalization scale, $\mu$, around the standard choice of $\mu$ equal to the nucleon mass $M$. Observed neutron star masses do not effectively constrain the value of $\...
1993-07-06
2009-10-22
[ "nucl-th" ]
M. Prakash, P.J. Ellis, E.K. Heide and S. Rudaz
nucl-th/9307004
Effects of the final-state interaction in ($\gamma$,pn) and ($\gamma$,pp) processes
A model is presented to describe electromagnetically induced two-nucleon emission processes in a shell-model picture. Distortions in the outgoing nucleon waves are accounted for by performing a partial-wave expansion in a real mean-field potential. The antisymmetry condition for the A-body wavefunctions is shown to be ...
1993-07-05
2009-10-22
[ "nucl-th" ]
J. Ryckebusch, M. Vanderhaeghen, L. Machenil and M. Waroquier
nucl-th/9307003
The Single-Particle Spectral Function of $^{16}{\rm O}$
The influence of short-range correlations on the $p$-wave single-particle spectral function in $^{16}{\rm O}$ is studied as a function of energy. This influence, which is represented by the admixture of high-momentum components, is found to be small in the $p$-shell quasihole wave functions. It is therefore unlikely th...
1993-07-02
2008-11-26
[ "nucl-th" ]
H. M\"uther and W.H. Dickhoff
nucl-th/9307002
Absorption mechanisms in photon induced two-body knockout
Calculations have been performed for the $^{16}$O($\gamma$,pn) and the $^{16}$O($\gamma$,pp) reaction in the photon-energy range $E_{\gamma}$ = 60-300 MeV. Besides the contribution from the more common photoabsorption on the pionic degrees of freedom, we have investigated the influence of heavier meson exchange ($\rho,...
1993-07-02
2009-10-22
[ "nucl-th" ]
L. Machenil, M. Vanderhaeghen, J. Ryckebusch and M. Waroquier
nucl-th/9307001
A Full $PF$ Shell Model Study of a~=~48 Nuclei
Exact diagonalizations with a minimally modified realistic force lead to detailed agreement with measured level schemes and electromagnetic transitions in $^{48}$Ca, $^{48}$Sc, $^{48}$Ti, $^{48}$V, $^{48}$Cr and $^{48}$Mn. Gamow-Teller strength functions are systematically calculated and reproduce the data to within th...
1993-07-01
2009-10-22
[ "nucl-th" ]
E. Caurier, A. P. Zuker, A. Poves, and G. Martinez-Pinedo
nucl-th/9306026
Improved Coupled Channels and R-Matrix Models: Predictions to 1 Gev
The $NN$ scattering near inelastic threshold is sensitive to the long-range diagonal interaction in the produced isobar channel. Earlier models included meson exchange potentials in the $NN$ sector and connecting that sector to isobar channels, as well as an $R$-matrix description of short-range quark effects. Includin...
1993-06-29
2007-05-23
[ "nucl-th" ]
P. LaFrance, E. L. Lomon, and M. Aw
nucl-th/9306025
Proton halo of $^8$B in a microscopic model
The experimentally predicted existence of a proton halo in $^8$B is confirmed by dynamical microscopic multiconfiguration cluster model calculations. The thickness of the proton halo in $^8$B is 0.5 $fm$ while in $^8$Li a 0.4 $fm$ thick neutron halo has been found. It is shown that the huge quadrupole moment of $^8$B p...
1993-06-29
2009-10-22
[ "nucl-th" ]
Attila Csoto
nucl-th/9306024
A Collective Model of Baryons
We propose an algebraic description of the geometric structure of baryons in terms of the algebra $U(7)$. We construct a mass operator that preserves the threefold permutational symmetry and discuss a collective model of baryons with the geometry of an oblate top.
1993-06-27
2007-05-23
[ "nucl-th", "hep-ph" ]
R. Bijker, F. Iachello and A. Leviatan
nucl-th/9306023
Microscopic multicluster description of neutron-halo nuclei with a stochastic variational method
To test a multicluster approach for halo nuclei, we give a unified description for the ground states of $^6$He and $^8$He in a model comprising an $\alpha$ cluster and single-neutron clusters. The intercluster wave function is taken a superposition of terms belonging to different arrangements, each defined by a set of ...
1993-06-25
2009-10-22
[ "nucl-th" ]
K. Varga, Y. Suzuki and R. G. Lovas
nucl-th/9306022
Iterative Solution for Effective Interactions in a System with Non-degenerate Unperturbed Energies
We generalize the Lee-Suzuki iteration method for summing the folded diagram series to the case where the unperturbed model-space energies are non-degenerate. A condition is derived for the convergence of the iteration scheme and this depends on the choice of the model space projection operators. Two choices are examin...
1993-06-23
2009-10-22
[ "nucl-th" ]
K. Suzuki, R. Okamoto, P.J. Ellis and T.T.S. Kuo
nucl-th/9306021
A Quark Transport Theory to describe Nucleon--Nucleon Collisions
On the basis of the Friedberg-Lee model we formulate a semiclassical transport theory to describe the phase-space evolution of nucleon-nucleon collisions on the quark level. The time evolution is given by a Vlasov-equation for the quark phase-space distribution and a Klein-Gordon equation for the mean-field describing ...
1993-06-22
2009-10-22
[ "nucl-th" ]
U. Kalmbach, T. Vetter, T. S. Biro and U. Mosel (Institut fuer Theoretische Physik, Universitaet Giessen 35392 Giessen, West Germany)
nucl-th/9306020
Antiproton Production in p-Nucleus and Nucleus-Nucleus Collisions within a Relativistic Transport Approach
The production of antiprotons in proton-nucleus and nucleus-nucleus reactions is calculated within the relativistic BUU approach employing proper selfenergies for the baryons and antiprotons and treating the p-bar annihilation nonperturbatively. The differential cross section for the antiprotons is found to be very sen...
1993-06-21
2009-10-22
[ "nucl-th" ]
Stefan Teis, Wolfgang Cassing, Tomoyuki Maruyama and Ulrich Mosel (Institut fuer Theoretische Physik, Universitaet Giessen D-35392 Giessen, Germany)
nucl-th/9306019
Charge-Symmetry Breaking, Rho-Omega Mixing and the Quark Propagator
The momentum-dependence of the $\rho^0$-$\omega$ mixing contribution to charge-symmetry breaking (CSB) in the nucleon-nucleon interaction is compared in a variety of models. We focus in particular on the role that the structure of the quark propagator plays in the predicted behaviour of the $\rho^0$-$\omega$ mixing amp...
1993-06-18
2009-10-22
[ "nucl-th" ]
G. Krein, A.W. Thomas and A.G. Williams
nucl-th/9306018
Algebraic Treatment of Collective Excitations in Baryon Spectroscopy
We present an algebraic U(7) model for baryons which encompasses both single-particle and collective forms of quark dynamics. The mass operator by construction preserves the permutation symmetry between identical quarks. The underlying geometric structure of baryons is discussed in terms of a rigid rotating and vibrati...
1993-06-17
2007-05-23
[ "nucl-th" ]
R. Bijker and A. Leviatan
nucl-th/9306017
Thermo Field Dynamics and Kinetic Coefficients of a Charged Boson Gas
Thermo Field Dynamics for inhomogeneous systems is generalized to quantum fields with a continuous single-particle mass spectrum. The modification of the hamiltonian in states with a local thermal Bogoliubov symmetry is used to calculate thermal conductivity and diffusion coefficient of pions interacting with hot, comp...
1993-06-17
2009-10-22
[ "nucl-th" ]
P.A.Henning
nucl-th/9306016
Selfconsistent Description of a Thermal Piongas
We examine a hot pion gas by including medium modifications of the two-body scattering amplitude as well as mean-field effects selfconsistently. In contrast to earlier calculations, the in-medium T-matrix is rather close to the free one while the mean-field potential agrees well with lowest-order estimates. We also dis...
1993-06-16
2009-10-22
[ "nucl-th" ]
R. Rapp and J. Wambach
nucl-th/9306015
Exotic Heavy Baryons at LHC?
We speculate about a heavy bottom-charm six-quark baryon. A semiclassical and a gaussian estimate reveal that the octet-octet bbb-ccc configuration can be energetically favored with respect to the singlet-singlet one. This result suggests that a confined bbb-ccc six-quark state may exist. Such objects may be produced i...
1993-06-15
2007-05-23
[ "nucl-th" ]
T.S.Biro and J.Zimanyi
nucl-th/9306014
Minimizing Effective Many-Body Interactions
A simple two-level model is developed and used to test the properties of effective interactions for performing nuclear structure calculations in truncated model spaces. It is shown that the effective many-body interactions sensitively depend on the choice of the single-particle basis and they appear to be minimized whe...
1993-06-14
2009-10-22
[ "nucl-th" ]
B. R. Barrett, D. C. Zheng, R. J. McCarthy and J. P. Vary
nucl-th/9306013
Generalized transparency in semi-inclusive processes
It is argued that the transparency of a medium for passage of a nucleon, knocked-out in a semi-inclusive $(e,e'p)$ reaction and subsequently scattered elastically, is not the same as the one measured in purely elastic scattering. Expressions are given for the properly generalized transparency and those are compared wit...
1993-06-13
2009-10-22
[ "nucl-th" ]
A.S. Rinat and B.K. Jennings
nucl-th/9306012
Dirac sea effects in $K^+$ scattering from nuclei
The ratio $R_T$ of $K^+-^{12}C$ to $K^+-d$ cross sections has been calculated microscopically using a boson-exchange $KN$ amplitude in which the $\sigma$ and $\omega$ mesons are dressed by the modifications of the Dirac sea in nuclear matter. In spite of the fact that this dressing leads to a scaling of the mesons effe...
1993-06-11
2011-08-17
[ "nucl-th" ]
J.C. Caillon and J. Labarsouque
nucl-th/9306011
Levinson's Theorem for Dirac Particles
Levinson's theorem for Dirac particles constraints the sum of the phase shifts at threshold by the total number of bound states of the Dirac equation. Recently, a stronger version of Levinson's theorem has been proven in which the value of the positive- and negative-energy phase shifts are separately constrained by the...
1993-06-10
2008-11-26
[ "nucl-th", "hep-th" ]
J. Piekarewicz
nucl-th/9306010
Exact response of the non-relativistic harmonic oscillator
Using Green$'$s function and operator techniques we give a closed expression for the response of a non-relativistic system interacting through confining, harmonic forces. The expression for the incoherent part permits rapid evaluation of coefficients in a 1/q expansion. A comparison is made with standard approximation ...
1993-06-10
2009-10-22
[ "nucl-th" ]
E. Pace, G. Salme and A.S. Rinat
nucl-th/9306009
Relativistic three-particle scattering equations
We derive a set of relativistic three-particle scattering equations in the three-particle c.m. frame employing a relativistic three-particle propagator suggested long ago by Ahmadzadeh and Tjon in the c.m. frame of a two-particle subsystem. We make the coordinate transformation of this propagator from the c.m. frame of...
1993-06-08
2008-11-26
[ "nucl-th" ]
Sadhan K. Adhikari, Lauro Tomio, and T. Frederico
nucl-th/9306005
Alpha scattering and capture reactions in the A = 7 system at low energies
Differential cross sections for $^3$He-$\alpha$ scattering were measured in the energy range up to 3 MeV. These data together with other available experimental results for $^3$He $+ \alpha$ and $^3$H $+ \alpha$ scattering were analyzed in the framework of the optical model using double-folded potentials. The optical po...
1993-06-07
2008-11-26
[ "nucl-th" ]
P. Mohr, H. Abele, R. Zwiebel, G. Staudt, H. Krauss, H. Oberhummer, A. Denker, J.W. Hammer, G. Wolf
nucl-th/9306006
Simple relativistic model of a finite-size particle
Soluble model of a relativistic particle describing a bag of matter with fixed radius held together in perfect balance by a self-consistent combination of three forces generated by electromagnetic and massive scalar and vector fields is presented. For realistic values of parameters the bag radius becomes that of a prot...
1993-06-07
2011-07-19
[ "nucl-th" ]
Iwo Bialynicki-Birula
nucl-th/9306008
Non-Linear Mean Field Dynamics in the Nuclear Spinodal Zone
We demonstrate, by numerical simulations, that the dynamics of nuclear matter mean field inside the spinodal region is chaotic. Spontaneous symmetry-breaking - no explicit fluctuating term is considered - occurs leading to wild unpredictable density fluctuations. A proper recipe to calculate an average Lyapunov exponen...
1993-06-07
2009-10-22
[ "nucl-th" ]
G.F. Burgio, M. Baldo and A. Rapisarda
nucl-th/9306007
Correlation Effects in the Final-State Interaction for Quasielastic $(e,e'p)$ Scattering
Color transparency predicts that, in $(e,e'p)$ reactions at large $Q^2$, the final-state interaction becomes weaker than the reference value predicted from the free-nucleon cross section. This reference value is usually evaluated in the dilute-gas approximation to Glauber's multiple-scattering theory. We derive the lea...
1993-06-07
2009-10-22
[ "nucl-th" ]
N.N.Nikolaev, A.Szczurek, J.Speth, J.Wambach, B.G.Zakharov, V.R.Zoller
nucl-th/9306004
Dilepton Production in Nucleon-Nucleon Reactions With and Without Hadronic Inelasticities
We calculate elementary proton-proton and neutron-proton bremsstrahlung and their contribution to the $e^+e^-$ invariant mass distribution. At 4.9 GeV, the proton-proton contribution is larger than neutron-proton, but it is small compared to recent data. We then make a first calculation of bremsstrahlung in nucleon-nuc...
1993-06-04
2008-11-26
[ "nucl-th", "hep-ph" ]
Kevin Haglin and Charles Gale
nucl-th/9306002
Hamiltonian Dynamics of Yang-Mills Fields on a Lattice
We review recent results from studies of the dynamics of classical Yang-Mills fields on a lattice. We discuss the numerical techniques employed in solving the classical lattice Yang-Mills equations in real time, and present results exhibiting the universal chaotic behavior of nonabelian gauge theories. The complete spe...
1993-06-02
2008-11-26
[ "nucl-th", "hep-lat", "hep-th" ]
T.S. Biro, C. Gong, B. Mueller, and A. Trayanov
nucl-th/9306003
Multiple Collisions and Induced Gluon Bremsstrahlung in QCD
Induced soft gluon bremsstrahlung associated with multiple collisions is calculated via perturbative QCD. We derive the non-abelian analog of the Landau-Pomeranchuk effect that suppresses induced soft radiation with formation times exceeding the mean free path, $\lambda$. The dependence of the suppression effect on the...
1993-06-02
2009-10-09
[ "nucl-th", "hep-ph" ]
Mikols Gyulassy and Xin-Nian Wang
nucl-th/9306001
From Skyrmions to NN phaseshifts
We study the $NN$ phaseshifts in a Hamiltonian obtained from quantization of the collective modes in the Skyrme model. We show that a combination of an adiabatic and diabatic approximation gives a good $NN$ force, with sufficient attraction to produce a bound deuteron. The description of the repulsive core appears to b...
1993-06-02
2008-11-26
[ "nucl-th" ]
Niels R. Walet
nucl-th/9305017
Momentum and Coordinate Space Three-nucleon Potentials
In this paper we give explicit formulae in momentum and coordinate space for the three-nucleon potentials due to $\rho$ and $\pi$ meson exchange, derived from off-mass-shell meson-nucleon scattering amplitudes which are constrained by the symmetries of QCD and by the experimental data. Those potentials have already bee...
1993-05-31
2008-11-26
[ "nucl-th" ]
S. A. Coon, M. T. Pena
nucl-th/9305016
Quantum Interference Effects in N* Electroproduction and Propagation in Nuclei
We discuss the unexpected enhancement of the $N^*$ electroproduction on nuclei recently observed in the $(\gamma^*,p\pi^-)$ measurement. A mechanism which is able to explain this result is proposed. To clarify the situation, we suggest to perform a new kind of experiment within well specified kinematic conditions.
1993-05-27
2008-11-26
[ "nucl-th" ]
A. Bianconi, S. Boffi and D.E. Kharzeev
nucl-th/9305015
Temperature induced alignment in hot rotating nuclei
Employing a cranking Hamiltonian, in the static path approximation to the partition function, we have studied the behaviour of the moment of inertia of $^{64}Zn$ at a few values of temperatures as a function of the rotation frequency. At a low temperature T = 0.5 MeV and J=16 rotational alignment of $0g_{9/2}$ orbitals...
1993-05-20
2009-10-22
[ "nucl-th" ]
B. K. Agrawal and A. Ansari
nucl-th/9305014
Three-Nucleon Force and the $\Delta$-Mechanism for Pion Production and Pion Absorption
The description of the three-nucleon system in terms of nucleon and $\Delta$ degrees of freedom is extended to allow for explicit pion production (absorption) from single dynamic $\Delta$ de-excitation (excitation) processes. This mechanism yields an energy dependent effective three-body hamiltonean. The Faddeev equati...
1993-05-20
2008-11-26
[ "nucl-th" ]
M. T. Pe\~na, P. U. Sauer, A. Stadler, and G. Kortemeyer
nucl-th/9305012
Collective Dipole Oscillations in Atomic Nuclei and Small Metal Particles
(The systematics of photon absorption cross sections in nuclei and small metal particles are examined as a function of the number of constituent fermions $A$. It is pointed out that the shell-structure-linked oscillations in the full width at half maximum (FWHM) of the photoneutron cross section in nuclei, earlier reco...
1993-05-19
2016-09-08
[ "nucl-th", "cond-mat" ]
R. S. Bhalerao and M. Barma
nucl-th/9305013
Proof of stability of the hydrogen molecule
We sketch two rigorous proofs of the stability of the hydrogen molecule in quantum mechanics. The first one is based on an extrapolation of variational estimates of the groundstate energy of a positronium molecule to arbitrary mass ratios. The second one is an extension of Heitler-London theory to nuclei of finite mass...
1993-05-19
2016-08-14
[ "nucl-th" ]
J.M. Richard, J. Fr\"ohlich, G.M. Graf and M. Seifert
nucl-th/9305011
A Theorem on Light-Front Quantum Models
I give a sufficient condition for a relativistic front-form quantum mechanical model to be scattering equivalent (unitarily equivalent with the same S-matrix elements) to a relativistic front-form quantum model with an interaction-independent front-form spin.
1993-05-18
2009-10-22
[ "nucl-th", "hep-ph" ]
Wayne N. Polyzou
nucl-th/9305010
Relativistic meson spectroscopy
In this paper a relativistic quantum theory introduced by de Groot and \mbox{Ruijgrok} in 1975, is used as a quark model in momentum space. The complete spectrum, with the exception of the selfconjugate light unflavoured mesons, is calculated. The potential used consists of an one-gluon-exchange (OGE) part and a confin...
1993-05-18
2007-05-23
[ "nucl-th", "hep-ph" ]
H. Hersbach
nucl-th/9305009
Monte Carlo evaluation of path integrals for the nuclear shell model
We present in detail a formulation of the shell model as a path integral and Monte Carlo techniques for its evaluation. The formulation, which linearizes the two-body interaction by an auxiliary field, is quite general, both in the form of the effective `one-body' Hamiltonian and in the choice of ensemble. In particula...
1993-05-14
2008-11-26
[ "nucl-th" ]
G. H. Lang, C. W. Johnson, S. E. Koonin, and W. E. Ormand
nucl-th/9305008
Effective Kaon Mass in Baryonic Matter and Kaon Condensation
The effective kaon mass in dense baryonic matter is calculated based on PCAC, current algebra and the Weinberg smoothness hypothesis. The off-shell behavior of the K-N scattering amplitudes is treated consistently with PCAC, and the effects of the subthreshold K-N resonances are also included. The effective kaon mass i...
1993-05-13
2009-10-22
[ "nucl-th" ]
Hiroyuki Yabu, Shinji Nakamura, F. Myhrer, and K. Kubodera
nucl-th/9305007
The column vector calculus for Thermo Field Dynamics of relativistic quantum fields
A formalism is discussed which simplifies the calculation of Feynman diagrams at finite temperature.
1993-05-12
2009-10-22
[ "nucl-th" ]
P.A.Henning
nucl-th/9305006
Composition, Structure and Evolution of Neutron Stars with Kaon Condensates
We investigate the possibility of kaon condensation in the dense interior of neutron stars through the s--wave interaction of kaons with nucleons. We include nucleon--nucleon interactions by using simple parametrizations of realistic forces, and include electrons and muons in $\beta$--equilibrium. The conditions under ...
1993-05-11
2009-10-22
[ "nucl-th", "astro-ph" ]
V. Thorsson, M. Prakash and J. M. Lattimer
nucl-th/9305005
Vacuum Structures in Hamiltonian Light-Front Dynamics
Hamiltonian light-front dynamics of quantum fields may provide a useful approach to systematic non-perturbative approximations to quantum field theories. We investigate inequivalent Hilbert-space representations of the light-front field algebra in which the stability group of the light-front is implemented by unitary t...
1993-05-10
2010-11-01
[ "nucl-th", "hep-ph" ]
F. Coester and W. Polyzou
nucl-th/9305004
Neural Filters for Jet Analysis
We study the efficiency of a neural-net filter and deconvolution method for estimating jet energies and spectra in high-background reactions such as nuclear collisions at the relativistic heavy-ion collider and the large hadron collider. The optimal network is shown to be surprisingly close but not identical to a linea...
1993-05-09
2009-10-22
[ "nucl-th" ]
Dawei W Dong and Miklos Gyulassy (Lawrence Berkeley Laboratory)
nucl-th/9305001
Localization of shadow poles by complex scaling
Through numerical examples we show that the complex scaling method is suited to explore the pole structure in multichannel scattering problems. All poles lying on the multisheeted Riemann energy surface, including shadow poles, can be revealed and the Riemann sheets on which they reside can be identified.
1993-05-05
2009-10-22
[ "nucl-th" ]
Attila Csoto
nucl-th/9305003
Thermal properties of a rotating nucleus in a fluctuating mean field approach
The static path approximation to the path integral representation of partition function provides a natural microscopic basis to deal with thermal fluctuations around mean field configurations. Using this approach for one-dimensional cranking Hamiltonian with quadrupole- quadrupole interaction term we have studied a f...
1993-05-05
2009-10-22
[ "nucl-th" ]
B. K. Agrawal and A. Ansari
nucl-th/9305002
Quark-based Description of Nuclear Matter with Simulated Annealing
We calculate ground-state properties of a many-quark system in the string-flip model using variational Monte Carlo methods. The many-body potential energy of the system is determined by finding the optimal grouping of quarks into hadrons. This (optimal) assignment problem is solved by using the stochastic optimization ...
1993-05-05
2009-10-22
[ "nucl-th" ]
George M. Frichter and J. Piekarewicz
nucl-th/9304025
Microscopic Calculations of the Spectra of Light Nuclei
We perform large-space shell-model calculations for the low-lying energy spectra of a few light nuclei, $^4\mbox{He}$, $^5\mbox{He}$, $^6\mbox{Li}$ and $^7\mbox{Li}$, in a no-core model space with a realistic effective two-body interaction (Brueckner G-matrix). Our G-matrices are calculated for the Reid-soft-core poten...
1993-04-27
2008-11-26
[ "nucl-th" ]
D.C. Zheng, B.R. Barrett, L. Jaqua, J.P. Vary, and R.J. McCarthy
nucl-th/9304023
Effects of Negative Energy Components in the Constituent Quark Model
Relativistic covariance requires that in the constituent quark model for mesons the positive energy states as well as the negative energy states are included. Using relativistic quasi-potential equations the contribution of the negative energy states is studied for the light and charmonium mesons. It is found that thes...
1993-04-27
2008-11-26
[ "nucl-th", "hep-ph" ]
Peter C. Tiemeijer and J.A. Tjon
nucl-th/9304024
Approximate Particle Number Projection for Rotating Nuclei
Pairing correlations in rotating nuclei are discussed within the Lipkin-Nogami method. The accuracy of the method is tested for the Krumlinde-Szyma\'nski R(5) model. The results of calculations are compared with those obtained from the standard mean field theory and particle-number projection method, and with exact sol...
1993-04-27
2008-11-26
[ "nucl-th" ]
P. Magierski, S. \'Cwiok, J. Dobaczewski, and W. Nazarewicz
nucl-th/9304022
Comment on "Comparison of Potential Models with the PP Scattering Data Below 350 Mev"
We point out two flaws in the recent test of nucleon-nucleon (NN) potentials conducted by Stoks and de Swart. First, in some cases, the neutron-proton ($np$) version of an NN potential was compared to the proton-proton ($pp$) data, which is improper and yields (large) $\chi^2$ that are essentially meaningless. Second, ...
1993-04-27
2007-05-23
[ "nucl-th" ]
G. Q. Li and R. Machleidt (University of Idaho)
nucl-th/9304021
The Off Shell $\rho$-$\omega$ Mixing in the QCD Sum Rules
The $q^2$ dependence of the $\rho-\omega$ mixing amplitude is analyzed with the use of the QCD sum rules and the dispersion relation. Going off shell the mixing decreases, changes sign at $q^2 \simeq 0.4 m_{\rho}^2 > 0$ and is negative in the space like region. Implications of this result to the isospin breaking part o...
1993-04-26
2008-11-26
[ "nucl-th", "hep-ph" ]
T. Hatsuda, E.M. Henley, Th. Meissner and G. Krein
nucl-th/9304020
No-Lose `Theorem' for Parity Violating Nucleon-Nucleon Scattering Experiments
A purely left-chiral model of the weak interactions is used to show that the total parity-violating asymmetry in quark-quark scattering must grow with increasing energy. In the absence of other new physics, non-observation of a large asymmetry can therefore be used to infer an upper bound on the mass scale for new righ...
1993-04-25
2007-05-23
[ "nucl-th", "hep-ph" ]
T. Goldman
nucl-th/9304019
Supershell Effect and Stability of Classical Periodic Orbits in Reflection-Asymmetric Superdeformed Oscillator
A semiclassical analysis is made of the origin of an undulating pattern in the smoothed level density for a reflection-asymmetric superdeformed oscillator potential. It is suggested that, when the octupole-type deformation increases, an interference effect between two families of periodic orbit with the ratio of period...
1993-04-23
2023-02-06
[ "nucl-th" ]
Ken-ichiro Arita
nucl-th/9304018
Electromagnetic Dipole Response as a Test of the $^{\bf 11}$Li g.s. Structure and the n-$^{\bf 9}$Li Interaction
The electric dipole response of the halo nucleus $^{11}$Li is calculated in a hyperspherical three-body formulation, and is studied as a function of the interaction employed for $n-^9$Li to reflect the Pauli principle. Strength concentrations at lower energies are found but no narrow resonances. Only one possible scena...
1993-04-23
2007-05-23
[ "nucl-th" ]
B.V. Danilin, M.V. Zhukov, J.S.Vaagen, I.J.Thompson, J.M.Bang
nucl-th/9304017
Quasielastic neutrino scattering from oxygen and the atmospheric neutrino problem
We examine several phenomena beyond the scope of Fermi-gas models that affect the quasielastic scattering (from oxygen) of neutrinos in the 0.1 -- 3.0 GeV range. These include Coulomb interactions of outgoing protons and leptons, a realistic finite-volume mean field, and the residual nucleon-nucleon interaction. None o...
1993-04-22
2010-11-01
[ "nucl-th", "hep-ph" ]
J.Engel, E. Kolbe, K. Langanke, P. Vogel
nucl-th/9304015
Colour transparency: a novel test of QCD in nuclear interactions
Colour transparency is a cute and indispensable property of QCD as the gauge theory of strong interaction. CT tests of QCD consist of production of the perturbative small-sized hadronic state and measuring the strngth of its non-perturbative diffraction nteraction in a nuclear matter. The energy depenednce of the final...
1993-04-20
2015-06-26
[ "nucl-th" ]
N.N.Nikolaev
nucl-th/9304014
Nucleon polarization in deuteron electrodisintegration
Outgoing nucleon polarization in exclusive deuteron electrodisintegration is studied at the quasi-elastic peak in the standard theory with emphasis on the effect of nucleonic and pionic relativistic corrections. The cases of polarized beam or/and polarized target are considered. Sizeable relativistic effects are pointe...
1993-04-20
2008-11-26
[ "nucl-th" ]
B. Mosconi, J. Pauschenwein and P. Ricci
nucl-th/9304016
Color Magnetic Corrections to Quark Model Valence Distributions
We calculate order $\alpha_s$ color magnetic corrections to the valence quark distributions of the proton using the Los Alamos Model Potential wavefunctions. The spin-spin interaction breaks the model SU(4) symmetry, providing a natural mechanism for the difference between the up and down distributions. For a value of ...
1993-04-20
2008-11-26
[ "nucl-th" ]
C.J. Benesh, T.Goldman, and G.J. Stephenson Jr
nucl-th/9304013
Electromagnetic Scattering from Relativistic Bound States
The quasipotential formalism for elastic scattering from relativistic bound states is formulated based on the instant constraint in the Breit frame. The quasipotential electromagnetic current is derived from Mandelstam's five-point kernel and obeys a two-body Ward identity. Breit-frame wave functions are obtained direc...
1993-04-17
2008-11-26
[ "nucl-th" ]
N. K. Devine and S. J. Wallace
nucl-th/9304011
Determination of Dipole Polarization Effects in $^7$Li and $^{11}$Li
The structure of $^6$Li, $^7$Li and $^{11}$Li nuclei is investigated in a model space which includes all configurations with oscillator energy up to $3\hbar\omega$ above the ground state configuration. The energy spectra and electromagnetic properties of the low-lying states are determined with various two-body interac...
1993-04-15
2009-10-22
[ "nucl-th" ]
L.D. Skouras, H. M\"uther, M.A. Nagarajan
nucl-th/9304012
Semi-Classical Description of Antiproton Capture on Atomic Helium
A semi-classical, many-body atomic model incorporating a momentum-dependent Heisenberg core to stabilize atomic electrons is used to study antiproton capture on Helium. Details of the antiproton collisions leading to eventual capture are presented, including the energy and angular momentum states of incident antiproton...
1993-04-15
2009-10-22
[ "nucl-th" ]
W. A. Beck, L. Wilets and M. A. Alberg
nucl-th/9304010
Model Analysis of Time Reversal Symmetry Test in the Caltech Fe-57 Gamma-Transition Experiment
The CALTECH gamma-transition experiment testing time reversal symmetry via the E2/M1 mulipole mixing ratio of the 122 keV gamma-line in Fe-57 has already been performed in 1977. Extending an earlier analysis in terms of an effective one-body potential, this experiment is now analyzed in terms of effective one boson exc...
1993-04-13
2008-11-26
[ "nucl-th", "hep-ph" ]
Michael Beyer
nucl-th/9304009
Maximum Azimuthal Anisotropy of Neutrons from Nb-Nb Collisions at 400 AMeV and the Nuclear Equation of State
We measured the first azimuthal distributions of triple--differential cross sections of neutrons emitted in heavy-ion collisions, and compared their maximum azimuthal anisotropy ratios with Boltzmann--Uehling--Uhlenbeck (BUU) calculations with a momentum-dependent interaction. The BUU calculations agree with the triple...
1993-04-13
2009-10-22
[ "nucl-th" ]
M. Elaasar, R. Madey, W. M. Zhang, J. Schambach, D. Keane, B. D. Anderson, A. R. Baldwin, J.W. Watson, G. D. Westfall, G. Krebs, H. Wieman, C. Gale and K. Haglin
nucl-th/9304007
Chiral Baryon with Quantized Pions
We study a hybrid chiral model for the nucleon based on the linear sigma model with explicit quarks. We solve the model using a Fock-space configuration consisting of three quarks plus three quarks and a pion as the ground state ansatz in place of the ``hedgehog'' ansatz. We minimize the expectation value of the chiral...
1993-04-08
2007-05-23
[ "nucl-th" ]
J. A. McNeil and C. E. Price
nucl-th/9304006
Diagonalization of full finite temperature Green's function by quasi-particles
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...
1993-04-08
2009-10-22
[ "nucl-th" ]
P.A.Henning and H.Umezawa
nucl-th/9304008
Nuclear Flow Excitation Function
We consider the dependence of collective flow on the nuclear surface thickness in a Boltzmann--Uehling--Uhlenbeck transport model of heavy ion collisions. Well defined surfaces are introduced by giving test particles a Gaussian density profile of constant width. Zeros of the flow excitation function are as much influen...
1993-04-08
2008-11-26
[ "nucl-th" ]
D. Klakow, G. Welke, and W. Bauer
nucl-th/9304005
The Delta-Hole model at Finite Temperature
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...
1993-04-08
2009-10-22
[ "nucl-th" ]
P.A.Henning and H.Umezawa
nucl-th/9304003
Collective Modes in a Slab of Interacting Nuclear Matter: The effects of finite range interactions
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...
1993-04-06
2015-06-26
[ "nucl-th" ]
W.M. Alberico, P. Czerski, A. De Pace and V.R. Manfredi
nucl-th/9304002
The Pion in Electromagnetic and Weak Neutral Current Nuclear Response Functions
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...
1993-04-06
2009-10-22
[ "nucl-th" ]
W.M. Alberico, M.B. Barbaro, A. De Pace, T.W. Donnelly and A. Molinari
nucl-th/9304004
Role of heavy-meson exchange in pion production near threshold
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...
1993-04-06
2008-11-26
[ "nucl-th" ]
C. J. Horowitz, H. O. Meyer and D. Griegel
nucl-th/9304001
Nambu-Jona-Lasinio Models Beyond the Mean Field Approximation
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...
1993-04-01
2008-11-26
[ "nucl-th" ]
P. Domitrovich, D. B\"uckers, H. M\"uther
nucl-th/9303026
Boson-fermion mappings for odd systems from supercoherent states
We extend the formalism whereby boson mappings can be derived from generalized coherent states to boson-fermion mappings for systems with an odd number of fermions. This is accomplished by constructing supercoherent states in terms of both complex and Grassmann variables. In addition to a known mapping for the full so(...
1993-03-31
2008-11-26
[ "nucl-th", "hep-th" ]
J. Dobaczewski, F.G. Scholtz, and H.B. Geyer
nucl-th/9303025
Gauge Invariance and the Electromagnetic Current of Composite Pions
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...
1993-03-30
2008-11-26
[ "nucl-th" ]
M.R. Frank and P.C.Tandy
nucl-th/9303024
Light front dynamics and the binding correction
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.
1993-03-29
2007-05-23
[ "nucl-th" ]
S.V.Akulinichev
nucl-th/9303023
Correlations in Nuclei: Self-Consistent Treatment and the BAGEL Approach
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-...
1993-03-29
2009-10-22
[ "nucl-th" ]
H. M\"uther and L.D. Skouras
nucl-th/9303022
Comment on Neutron-Proton Spin-Correlation Parameter A_{ZZ} at 68 Mev
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...
1993-03-27
2009-10-22
[ "nucl-th" ]
R. Machleidt and I. Slaus
nucl-th/9303018
Dirac Hartree-Fock for Finite Nuclei Employing realistic Forces
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...
1993-03-26
2009-10-22
[ "nucl-th" ]
R.Fritz H.M\"uther and R.Machleidt
nucl-th/9303019
On the Spectacular Large Asymmetry in $\pbarppipi$ and $\pbarpKK$ Reactions}
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...
1993-03-26
2019-08-17
[ "nucl-th" ]
S. Takeuchi, F. Myhrer and K. Kubodera (Department of Physics and Astronomy, University of South Carolina, Columbia, SC29208)
nucl-th/9303020
Exclusive Hadronic Reactions at High $Q^2$ ($90\degree$) and Polarization Phenomena, An Experimental Proposal}
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...
1993-03-26
2007-05-23
[ "nucl-th" ]
F. Myhrer (Department of Physics and Astronomy, University of South Carolina, Columbia, SC29208)
nucl-th/9303021
The Quasi-Elastic Nuclear Response
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...
1993-03-26
2009-09-25
[ "nucl-th" ]
A. De Pace and M. Viviani
nucl-th/9303017
Quantum theory of large amplitude collective motion and the Born-Oppenheimer method
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. ...
1993-03-20
2008-11-26
[ "nucl-th" ]
Abraham Klein and Niels R. Walet
nucl-th/9303015
Probing Hadronic Structure with The Decay $\Delta\rightarrow Nl^+l^-$
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...
1993-03-18
2008-11-26
[ "nucl-th" ]
Malcolm N. Butler, Martin J. Savage, Roxanne P. Springer
nucl-th/9303016
Nuclear effects in Deep Inelastic Scattering of polarized electrons off polarized 3He and the neutron spin structure functions
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...
1993-03-18
2008-11-26
[ "nucl-th" ]
C.Ciofi degli Atti, S.Scopetta, E.Pace, G.Salme
nucl-th/9303013
Angular Momentum Analysis of Spin 1/2 x 1/2 Scattering including Singlet-Triplet Mixing
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 ...
1993-03-18
2009-09-25
[ "nucl-th" ]
T. Mefford and R. H. Landau
nucl-th/9303014
Critical test of multi-{\it j} supersymmetries from magnetic moment measurements
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...
1993-03-18
2008-11-26
[ "nucl-th" ]
Serdar Kuyucak and Andrew E. Stuchbery
nucl-th/9303012
Left-Right Asymmetry in $\bar{p}p \rightarrow \pi^- \pi^+$
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...
1993-03-16
2008-11-26
[ "nucl-th" ]
George Bathas and W.M. Kloet
nucl-th/9303011
Orbital M1 versus E2 strength in deformed nuclei: A new energy weighted sum rule
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 ...
1993-03-16
2008-11-26
[ "nucl-th" ]
E. Moya de Guerra and L. Zamick
nucl-th/9303010
Ghost Poles in the Nucleon Propagator: Vertex Corrections and Form Factors
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 ...
1993-03-15
2008-11-26
[ "nucl-th" ]
G. Krein, M. Nielsen, R.D. Puff and L. Wilets
nucl-th/9303009
The response of non-relativistic confined systems
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 ...
1993-03-14
2008-11-26
[ "nucl-th" ]
S.A. Gurvitz and A.S. Rinat
nucl-th/9303007
The neutron halo of $^6$He in a microscopic model
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...
1993-03-11
2008-11-26
[ "nucl-th" ]
Attila Csoto