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Quantification of Uncertainties in Nuclear Density Functional theory: Reliable predictions of nuclear properties are needed as much to answer
fundamental science questions as in applications such as reactor physics or
data evaluation. Nuclear density functional theory is currently the only
microscopic, global approach to nuclear structure that is applicable throughout
the nuclear chart. In the past few years, a lot of effort has been devoted to
setting up a general methodology to assess theoretical uncertainties in nuclear
DFT calculations. In this paper, we summarize some of the recent progress in
this direction. Most of the new material discussed here will be be published in
separate articles. | nucl-th |
Residual cut-off dependence and power counting: the deuteron as a case
study: Effective field theories (EFTs) require regularization and renormalization to
gain predictive power. While regularization is inconsequential from the point
of view of the observable predictions of EFT -- in a renormalized theory we
expect predictions to be regulator-independent once the cutoff is removed --
the particular details of regulator dependence might provide interesting
insights into the inner workings of an EFT. In fact, the analysis of regulator
dependence has been frequently suggested as a tool to study the ordering scheme
or power counting of EFTs. We show here that the choice of the regulator might
impact the power law properties of the residual cutoff dependence. If this
conclusion were to be confirmed, it would have consequences on the validity of
this method as a tool to analyze power counting. | nucl-th |
Symmetry background of the stability of the second 0^+ state of 4^He: It was found in this paper that the dominant component of the wave function
of the second 0^+ state of 4^He and the corresponding component of the 3^H+p
channel have different spatial permutation symmetries. This fact will hinder
the wave function to extend from the interior region to the outgoing channel
and will lead to a narrower width. | nucl-th |
Chemical freezeout parameters within generic nonextensive statistics: The particle production in relativistic heavy-ion collisions seems to be
created in a dynamically disordered system which can be best described by an
extended exponential entropy. In distinguishing between the applicability of
this and Boltzmann-Gibbs (BG) in generating various particle-ratios, generic
(non)extensive statistics (GNS) is introduced to the hadron resonance gas
model. Accordingly, the degree of (non)extensivity is determined by the
possible modifications in the phase space. Both BG extensivity and Tsallis
nonextensivity are included as very special cases defined by specific values of
the equivalence classes $(c, d)$. We found that the particle ratios at energies
ranging between $3.8$ and $2760~$GeV are best reproduced by nonextensive
statistics, where $c$ and $d$ range between $\sim0.9$ and $\sim1$. The present
work aims at illustrating that the proposed approach is well capable to
manifest the statistical nature of the system on interest. We don't aim at
highlighting deeper physical insights. In other words, while the resulting
nonextensivity is neither BG nor Tsallis, the freezeout parameters are found
very compatible with BG and accordingly with the well-known freezeout
phase-diagram, which is in an excellent agreement with recent lattice
calculations. We conclude that the particle production is nonextensive but
should not necessarily be accompanied by a radical change in the intensive or
extensive thermodynamic quantities, such as internal energy and temperature.
Only, the two critical exponents defining the equivalence classes $(c, d)$ are
the physical parameters characterizing the (non)extensivity. | nucl-th |
Production of heavy and superheavy nuclei in massive fusion reactions: Within the framework of a dinuclear system (DNS) model, the
evaporation-residue excitation functions and the quasi-fission mass yields in
the $^{48}$Ca induced fusion reactions are investigated systematically and
compared with available experimental data. Maximal production cross sections of
superheavy nuclei based on stable actinide targets are obtained. Isotopic
trends in the production of the superheavy elements Z=110, 112-118 based on the
actinide isotopic targets are analyzed systematically. Optimal evaporation
channels and combinations as well as the corresponding excitation energies are
proposed. The possible factors that influencing the isotopic dependence of the
production cross sections are analyzed. The formation of the superheavy nuclei
based on the isotopes U with different projectiles are also investigated and
calculated. | nucl-th |
Role of three-nucleon forces and many-body processes in nuclear pairing: We present microscopic valence-shell calculations of pairing gaps in the
calcium isotopes, focusing on the role of three-nucleon (3N) forces and
many-body processes. In most cases, we find a reduction in pairing strength
when the leading chiral 3N forces are included, compared to results with
low-momentum two-nucleon (NN) interactions only. This is in agreement with a
recent energy density functional study. At the NN level, calculations that
include particle-particle and hole-hole ladder contributions lead to smaller
pairing gaps compared with experiment. When particle-hole contributions as well
as the normal-ordered one- and two-body parts of 3N forces are consistently
included to third order, we find reasonable agreement with experimental
three-point mass differences. This highlights the important role of 3N forces
and many-body processes for pairing in nuclei. Finally, we relate pairing gaps
to the evolution of nuclear structure in neutron-rich calcium isotopes and
study the predictions for the 2+ excitation energies, in particular for 54Ca. | nucl-th |
Parity-violating nucleon-nucleon interaction from different approaches: Two-pion exchange parity-violating nucleon-nucleon interactions from recent
effective field theories and earlier fully covariant approaches are
investigated. The potentials are compared with the idea to obtain better
insight on the role of low-energy constants appearing in the effective field
theory approach and the convergence of this one in terms of a perturbative
series. The results are illustrated by considering the longitudinal asymmetry
of polarized protons scattering off protons, $\vec{p}+p -> p+p$, and the
asymmetry of the photon emission in radiative capture of polarized neutrons by
protons, $\vec{n}+p -> d+\gamma$. | nucl-th |
Energy Systematics of Jet Tomography at RHIC: sqrt{s} = 62.4 vs 200 AGeV: The collision energy dependence of jet tomography is investigated within the
GLV formalism. The emphasis is on estimating systematic uncertainties resulting
from the interplay of energy loss fluctuations and the rapid increase of the
parton transverse momentum slopes as sqrt{s} decreases from 200 to 62 AGeV. | nucl-th |
Structure of ground and excited states of $^{12}$C: We studied the ground and excited states of $^{12}$C based on variational
calculations after spin-parity projection in a framework of antisymmetrized
molecular dynamics(AMD). The calculations systematically reproduce various
experimental data. It was found that the sub-shell closure and SU(3)-limit
$3\alpha$ cluster components are contained in the ground state, while various
$3\alpha$ cluster structures develop in the excited states. We discussed
effects of $\alpha$ breaking and show the importance of coexistence of the
cluster and shell-model-like aspects. | nucl-th |
Strongly Intensive Cumulants: Fluctuation Measures for Systems With
Incompletely Constrained Volumes: The cumulants of thermal variables are of general interest in physics due to
their extensivity and their correspondence with susceptibilities. They become
especially significant near critical points of phase transitions where they
diverge along with the correlation length. Cumulant measurements have been used
extensively within the field of heavy-ion physics, principally as tools in the
search for a hypothetical QCD critical point along the transition between
hadronic matter and QGP. The volume of individual heavy-ion collisions can be
only partially constrained and, as a result, cumulant measurements are
significantly biased by the limited volume resolution. We propose a class of
moments called strongly intensive cumulants which can be accurately measured in
the presence of unconstrained volume fluctuations. Additionally, they share the
same direct relationship with susceptibilities as cumulants in many cases. | nucl-th |
Determination of matter radius and neutron skin of $^{58}$Ni from
reaction cross section of proton+$^{58}$Ni scattering based on chiral
$g$-matrix model: Background: Using the chiral (Kyushu) $g$-matrix folding model with the
densities calculated with Gogny-HFB (GHFB) with the angular momentum projection
(AMP), we determined the central values of matter radius and neutron skin from
the central values of reaction cross sections $\sigma_{\rm R}({\rm EXP})$ of
p+$^{40,48}$Ca and p+$^{208}$Pb scattering. As for p+$^{58}$Ni scattering,
$\sigma_{\rm R}({\rm EXP})$ are available as a function of incident energy
$E_{\rm in}$. Aim: Our aim is to determine matter radius $r_{m}$ and skin
$r_{\rm skin}$ for $^{58}$Ni from the $\sigma_{\rm R}({\rm EXP})$ of
p+$^{58}$Ni scattering by using the Kyushu $g$-matrix folding model with the
GHFB+AMP densities. Results: For p+$^{58}$Ni scattering, the Kyushu $g$-matrix
folding model with the GHFB+AMP densities reproduces $\sigma_{\rm R}({\rm
EXP})$ in $8.8 \leq E_{\rm in} \leq 81$MeV. For $E_{\rm in}=81$MeV, we define
the factor $F$ as $F=\sigma_{\rm R}({\rm EXP})/\sigma_{\rm R}({\rm
AMP})=0.9775$. The $F\sigma_{\rm R}({\rm AMP})$ be much the same as the center
values of $\sigma_{\rm R}({\rm EXP})$ in $8.8 \leq E_{\rm in} \leq 81$MeV. We
then determine $r_{\rm m}({\rm EXP})$ from the center values of $\sigma_{\rm
R}({\rm EXP})$, using $\sigma_{\rm R}({\rm EXP})=C r_{m}^{2}({\rm EXP})$ with
$C=r_{m}^{2}({\rm AMP})/ (F\sigma_{\rm R}({\rm AMP}))$. The $r_{m}({\rm EXP})$
thus obtained are averaged over $E_{\rm in}$. The averaged value is $r_{m}({\rm
EXP})=3.697$fm. Eventually, we obtain $r_{\rm skin}({\rm EXP})=0.023$fm from
$r_{\rm m}=3.697$fm and $r_p({\rm EXP})=3.685$fm of electron scattering. | nucl-th |
A correlated model for lambda-hypernuclei: We study the properties of hypernuclei containing one lambda hyperon in the
framework of the correlated basis function theory with Jastrow correlations.
Fermi hypernetted chain integral equations are derived and used to evaluate
energies and one-body densities of lambda hypernuclei having a doubly closed
shell nucleonic core in the jj coupling scheme, from Carbon to Lead. We also
study hypernuclei having the least bound neutron substituted by the lambda
particle. The semi-realistic Afnan and Tang nucleon-nucleon potential and
Bodmer and Usmani lambda-nucleon potential are adopted. The effect of many-body
forces are considered by means either of a three body lambda-nucleon-nucleon
potential of the Argonne type or of a density dependent modification of the
lambda-nucleon interaction, fitted to reproduce the lambda binding energy in
nuclear matter. While Jastrow correlations underestimate the attractive
contribution of the three body $\la$ interaction, the density dependent
potential provides a good description of the lambda binding energies over all
the nuclear masses range, in spite of the relative simplicity of the model. | nucl-th |
Indication of Collective Flow and Transparency in p-p Collisions at LHC: The mid-rapidity transverse momentum spectra of hadrons and the available
rapidity distributions of the strange hadrons produced in p-p collisions at LHC
energy root(snn) = 0.9 TeV and root(snn)= 7.0 TeV have been studied using a
unified statistical thermal freeze-out model. The calculated results are found
to be in good agreement with the experimental data. The theoretical fits of the
transverse momentum spectra using the model calculations provide the thermal
freeze-out conditions in terms of the temperature and collective flow
parameters for different hadronic species. The study reveal the presence of
significant collective flow and a well defined temperature in the system thus
indicating the formation of a thermally equilibrated hydrodynamic system in p-p
collisions at LHC. Moreover, the fits to the available experimental rapidity
distributions data of strange hadrons show the effect of almost complete
transparency in p-p collisions at LHC. The transverse momentum distributions of
protons and Kaons produced in p-p collisions at root(snn) = 200 GeV and
root(snn)= 2.76 TeV have also been reproduced successfully. The model
incorporates longitudinal as well as a transverse hydrodynamic flow. The
contributions from heavier decay resonances have also been taken into account.
We have also imposed the criteria of exact strangeness conservation in the
system. | nucl-th |
Symmetry energy from fragment observables in the canonical thermodynamic
model: Different formulas relying measurable fragment isotopic observables to the
symmetry energy of excited nuclei have been proposed and applied to the
analysis of heavy ion collision data in the recent literature. In this paper we
examine the quality of the different expressions in the framework of the McGill
Canonical Thermodynamic Model. We show that even in the idealized situation of
canonical equilibrium and in the absence of secondary decay, these formulas do
not give a precise reconstruction of the symmetry energy of the fragmenting
source. However, both isotopic widths and isoscaling appear very well
correlated to the physical symmetry energy. | nucl-th |
Isovector deformation and its link to the neutron shell closure: DWBA analysis of the inelastic $^{30-40}$S$(p,p')$ and $^{18-22}$O$(p,p')$
scattering data measured in the inverse kinematics has been performed to
determine the isoscalar ($\delta_0$) and isovector ($\delta_1$) deformation
lengths of the 2$^+_1$ excitations in the Sulfur and Oxygen isotopes using a
compact folding approach. A systematic $N$-dependence of $\delta_0$ and
$\delta_1$ has been established which shows a link between $\delta_1$ and the
neutron-shell closure. Strong isovector deformations were found in several
cases, e.g., the 2$^+_1$ state in $^{20}$O where $\delta_1$ is nearly three
times larger than $\delta_0$. These results confirm the relation
$\delta_1>\delta_0$ anticipated from the core polarization by the valence
neutrons in the open-shell (neutron rich) nuclei. The effect of neutron shell
closure at N=14 or 16 has been discussed based on the folding model analysis of
the inelastic $^{22}$O+$p$ scattering data at 46.6 MeV/u measured recently at
GANIL. | nucl-th |
Heavy quark(onium) at LHC: the statistical hadronization case: We discuss the production of charmonium in nuclear collisions within the
framework of the statistical hadronization model. We demonstrate that the model
reproduces very well the availble data at RHIC. We provide predictions for the
LHC energy where, dependently on the charm production cross section, a
dramatically different behaviour of charmonium production as a function of
centrality might be expected. We discuss also the case in elementary
collisions, where clearly the statistical model does not reproduce the
measurements. | nucl-th |
Breakup of $^8$B and the $^7$Be($p,γ)^8$B reaction: The calculated rate of events in some of the existing solar neutrino
detectors is directly proportional to the rate of the $^7$Be($p,\gamma)^8$B
reaction measured in the laboratory at low energies. However, the low-energy
cross sections of this reaction are quite uncertain as various measurements
differ from each other by 30-40 %. The Coulomb dissociation process which
reverses the radiative capture by the dissociation of $^8$B in the Coulomb
field of a target, provides an alternate way of accessing this reaction. While
this method has several advantages (like large breakup cross sections and
flexibility in the kinematics), the difficulties arise from the possible
interference by the nuclear interactions, uncertainties in the contributions of
the various multipoles and the higher order effects, which should be considered
carefully. We review the progress made so far in the experimental measurements
and theoretical analysis of the breakup of $^8$B and discuss the current status
of the low-energy cross sections (or the astrophysical $S$-factor) of the
$^7$Be($p,\gamma)^8$B reaction extracted therefrom. The future directions of
the experimental and theoretical investigations are also suggested. | nucl-th |
Breakup reactions of the halo nuclei Be11 and B8: We calculate the nuclear induced breakup of Be11 and B8 using a more
realistic treatment of the diffraction and stripping processes than in previous
work. The breakup is treated in the eikonal approximation with a profile
function calculated from a realistic optical potential at low energies and from
free nucleon-nucleon cross sections at high energies. This treatment gives a
good description of measured breakup cross sections, as well as the
longitudinal momentum distribution of the core-like fragments, which is
narrower than predicted in the transparent limit. The real part of the
potential is found to be significant and enhances the diffractive breakup at
low energies. | nucl-th |
Back-to-back relative-excess observable in search for the chiral
magnetic effect: $\textbf{Background:}$ The chiral magnetic effect (CME) is extensively
studied in heavy-ion collisions at RHIC and LHC. In the commonly used reaction
plane (RP) dependent, charge dependent azimuthal correlator ($\Delta\gamma$),
both the close and back-to-back pairs are included. Many backgrounds contribute
to the close pairs (e.g. resonance decays, jet correlations), whereas the
back-to-back pairs are relatively free of those backgrounds.
$\textbf{Purpose:}$ In order to reduce those backgrounds, we propose a new
observable which only focuses on the back-to-back pairs, namely, the relative
back-to-back opposite-sign (OS) over same-sign (SS) pair excess
($r_{\text{BB}}$) as a function of the pair azimuthal orientation with respect
to the RP ($\varphi_{\text{BB}}$).
$\textbf{Methods:}$ We use analytical calculations and toy model simulations
to demonstrate the sensitivity of $r_{\text{BB}}(\varphi_{\text{BB}})$ to the
CME and its insensitivity to backgrounds.
$\textbf{Results:}$ With finite CME, the $\varphi_{\text{BB}}$ distribution
of $r_{\text{BB}}$ shows a clear characteristic modulation. Its sensitivity to
background is significantly reduced compared to the previous $\Delta\gamma$
observable. The simulation results are consistent with our analytical
calculations.
$\textbf{Conclusions:}$ Our studies demonstrate that the
$r_{\text{BB}}(\varphi_{\text{BB}})$ observable is sensitive to the CME signal
and rather insensitive to the resonance backgrounds. | nucl-th |
Two neutrino double beta decay within the $ξ$-approximation: We examine the contributions of odd-parity nuclear operators to the
two-neutrino double beta decay $0^+\rightarrow 0^+$ amplitude, which come from
the $P$-wave Coulomb corrections to the electron wave functions and the recoil
corrections to the nuclear currents. Although they are formally of higher order
in $\alpha Z/2$ or $v/c$ of the nucleon than the usual Fermi and Gamow-Teller
matrix elements, explicit calculations performed within the QRPA show that they
are significant when confronted with the experimental data. | nucl-th |
First Excited 2+ Energy State Estimations of Even-even Nuclei by Using
Artificial Neural Networks: The first excited 2+ energy states of nuclei give many substantial
information related to the nuclear structure. Including these levels, all
excited states of nuclei are shown regularities in spin, parity and energy. In
the even-even nuclei, the first excited state is generally 2+ and the energy
values of them increase as the closed shells are approached. The excited levels
in nuclei can be investigated by using theoretical nuclear models such nuclear
shell model. In the present study for the first time, we have used artificial
neural networks for the determination of the energies of first 2+ states in the
even-even nuclei in nuclidic chart as a function of Z, N and A numbers. We have
used adopted literature values for the estimations. According to the results,
the method is convenient for this goal and one can confidently use the method
for the determination of first 2+ state energy values whose experimental values
do not exist in the literature. | nucl-th |
Bifurcation in kinetic equation for interacting Fermi systems: The finite duration of collisions appear as time-nonlocality in the kinetic
equation. Analyzing the corresponding quantum kinetic equation for dense
interacting Fermi systems a delay differential equation is obtained which
combines time derivatives with finite time stepping known from the logistic
mapping. The responsible delay time is explicitly calculated and discussed. As
a novel feature oscillations in the time evolution of the distribution function
itself appear and bifurcations up to chaotic behavior can occur. The
temperature and density conditions are presented where such oscillations and
bifurcations arise indicating an onset of phase transition. | nucl-th |
Recent developments in the constituent quark model including
quark-antiquark pairs: We present the formalism for a new generation of unquenched quark models for
baryons in which the effects of quark-antiquark pairs (u anti-u, d anti-d and s
anti-s) are taken into account in an explicit form via a microscopic,
QCD-inspired, quark-antiquark creation mechaniscm. The present approach is an
extension of the flux-tube breaking model of Geiger and Isgur in which now the
contributions of quark-antiquark pairs an be studied for any initial baryon and
for any flavor of the q anti-q pair. It is shown that the inclusion of q anti-q
paris leads to a large contribution of orbital angular momentum to the proton
spin. | nucl-th |
Analysis of Chiral Mean-Field Models for Nuclei: An analysis of nuclear properties based on a relativistic energy functional
containing Dirac nucleons and classical scalar and vector meson fields is
discussed. Density functional theory implies that this energy functional can
include many-body effects that go beyond the simple Hartree approximation.
Using basic ideas from effective field theory, a systematic truncation scheme
is developed for the energy functional, which is based on an expansion in
powers of the meson fields and their gradients.
Chiral models are analyzed by considering specific lagrangians that realize
the spontaneously broken chiral symmetry of QCD in different ways and by
studying them at the Hartree level. Models that include a light scalar meson
playing a dual role as the chiral partner of the pion and the mediator of the
intermediate-range nucleon-nucleon interaction, and which include a
"Mexican-hat" potential, fail to reproduce basic ground-state properties of
nuclei. In contrast, chiral models with a nonlinear realization of the symmetry
are shown to contain the full flexibility inherent in the general energy
functional and can therefore successfully describe nuclei. | nucl-th |
Fusion rates in nuclear plasmas: Energy and momentum of the elementary excitations become independent
variables in medium: energy and momentum statistical distributions are not
identical. The momentum distribution and not the energy distribution is
relevant for barrier penetration. The deviations of the momentum distribution
from the Maxwell-Boltzmann energy distribution can be expressed in terms of the
imaginary part of the self-energy of the quasi-particle. It is possible to
obtain an effective Tsallis' distribution for the kinetic energy. These effects
are different from static or dynamical screening and can have important
consequences for reaction rates in stars. | nucl-th |
Hindered alpha decays of heaviest high-K isomers: To find candidates for long-lived high-K isomers in even-even Z=106-112
superheavy nuclei we study dominant alpha-decay channel of two- and
four-quasi-particle configurations at a low excitation. Energies are calculated
within the microscopic - macroscopic approach with the deformed Woods-Saxon
potential. Configurations are fixed by a standard blocking procedure and their
energy found by a subsequent minimization over deformations. Different
excitation energies of a high-K configuration in parent and daughter nucleus
seem particularly important for a hindrance of the alpha-decay. A strong
hindrance is found for some four-quasi-particle states, particularly $K^{\pi} =
20^{+}$ and/or $19^{+}$ states in $^{264-270}$Ds. Contrary to what was
suggested in experimental papers, it is rather a proton configuration that
leads to this strong hindrance. If not shortened by the electromagnetic decay,
alpha half-lives of $\sim$ 1 s could open new possibilities for studies of
chemical/atomic properties of related elements. | nucl-th |
A model for nuclear matter fragmentation: phase diagram and cluster
distributions: We develop a model in the framework of nuclear fragmentation at thermodynamic
equilibrium which can be mapped onto an Ising model with constant
magnetization. We work out the thermodynamic properties of the model as well as
the properties of the fragment size distributions. We show that two types of
phase transitions can be found for high density systems. They merge into a
unique transition at low density. An analysis of the critical exponents which
characterize observables for different densities in the thermodynamic limit
shows that these transitions look like continuous second order transitions. | nucl-th |
Single and double pi^{-}/pi^{+} ratios in heavy-ion reactions as probes
of the high-density behavior of the nuclear symmetry energy: Based on an isospin- and momentum-dependent hadronic transport model IBUU04,
effects of the nuclear symmetry energy on the single and double
pi^{-}/pi^{+}ratios in central reactions of ^{132}Sn+^{124}Sn and
^{112}Sn+^{112}Sn at a beam energy of 400 MeV/nucleon are studied. It is found
that around the Coulomb peak of the single pi^{-}/pi^{+} ratio the double
pi^{-}/pi^{+} ratio taken from the two isotopic reactions retains about the
same sensitivity to the density dependence of nuclear symmetry energy. Because
the double pi^{-}/pi^{+}ratio can reduce significantly the systematic errors,
it is thus a more effective probe for the high-density behavior of the nuclear
symmetry energy. | nucl-th |
Landau-Ginzburg method applied to finite fermion systems: Pairing in
Nuclei: Given the spectrum of a Hamiltonian, a methodology is developed which employs
the Landau-Ginsburg method for characterizing phase transitions in infinite
systems to identify phase transition remnants in finite fermion systems. As a
first application of our appproach we discuss pairing in finite nuclei. | nucl-th |
Nonperturbative QCD Phenomenology and Light Quark Physics: Recent progress in modeling QCD for hadron physics through truncated
Dyson-Schwinger equations is reviewed. Special emphasis is put upon comparison
of dressed quark propagators and the dressed quark-gluon vertex with
lattice-QCD results. | nucl-th |
Uncertainties in nuclear transition matrix elements for neutrinoless
$ββ$ decay within the PHFB model: The nuclear transition matrix elements $M^{(0\nu)}$ for the neutrinoless
double beta decay of $^{94,96}$Zr, $^{98,100}$Mo, $^{104}$Ru, $^{110}$Pd,
$^{128,130}$Te and $^{150}$Nd isotopes in the case of $0^{+}\rightarrow 0^{+}$
transition are calculated using the PHFB wave functions, which are eigenvectors
of four different parameterizations of a Hamiltonian with pairing plus
multipolar effective two-body interaction. \QCOM{35}{In addition, the
consideration of} Employing two (three) different parameterizations of
Jastrow-type short range correlations, \QCOM{19}{provides us with} a set of
eight (twelve) different nuclear transition matrix elements $M^{(0\nu)}$ is
built for each decay, whose averages in conjunction with their standard
deviations provide an estimate of the model uncertainties. | nucl-th |
SU(2) Chiral sigma model and the properties of neutron stars: We discuss the {\it SU}(2) chiral sigma model in the context of nuclear
matter using a mean field approach at high density. In this model we include a
dynamically generated isoscalar vector field and higher-order terms in the
scalar field. With the inclusion of these, we reproduce the empirical values of
the nuclear matter saturation density, binding energy, and nuclear
incompressibility. The value of the incompressibility is chosen according to
recently obtained heavy-ion collision data. We then apply the same dynamical
model to neutron-rich matter in beta equilibrium, related to neutron star
structure. The maximum mass and corresponding radius of stable non-rotating
neutron stars are found to be in the observational limit. | nucl-th |
The Non-perturbative Interaction of the Pseudovector Coupling for the
Pion-nucleon Scattering: The effect of the non-perturbative term is investigated for the pion-nucleon
scattering. Including the self-energy of nucleon the cross section of the
elastic scattering results in a constant value at the laboratory momentum $p_L
\to \infty$. The amplitude of the forward direction is applied to the
dispersion relation. | nucl-th |
Formation Of Quark Matter In Neutron Stars: At very large densities and/or temperatures a quark-hadron phase transition
is expected to take place. Simulations of QCD on lattice at zero baryon density
indicate that the transition occurs at $T_c \sim 150-170$ MeV. The calculations
indicate that transition is likely to be second order or a cross over
phenomenon. Although the lattice simulations have not given any indication on
when the transition occurs at nonzero baryon density, the transition is
expected to occur around the densities of few times nuclear matter density.
Also, there is a strong reason to believe that the quark matter formed after
the phase transition is in colour superconducting phase. The matter densities
in the interior of neutron stars are expected to be several times the nuclear
matter density and therefore the neutron star cores may possibly consist of
quark matter. One then expects that this quark matter is formed during the
collapse of supernova. Starting with the assumption that the quark matter, when
formed consists of predominantly u and d quarks, we consider the evolution of
strange quarks by weak interactions in the present work. The reaction rates and
time required to reach the chemical equilibrium are computed here. Our
calculations show that the chemical equilibrium is reached in about $10^{-7}$
seconds. Further more during and immediately after the equilibration process
enormous amount of energy is released and copious numbers of neutrinos are
produced. We show that for reasonable models of nuclear equations of state the
amount of energy released could be as high as $10^{53}$ ergs and as many as
$10^{58}$ neutrinos may be emitted during the quark matter formation. | nucl-th |
The anatomy of the simplest Duflo-Zuker mass formula: The simplest version of the Duflo-Zuker mass model (due entirely to the late
Jean Duflo) is described by following step by step the published computer code.
The model contains six macroscopic monopole terms leading asymptotically to a
Liquid Drop form, three microscopic terms supposed to mock configuration mixing
(multipole) corrections to the monopole shell effects, and one term in charge
of detecting deformed nuclei and calculating their masses. A careful analysis
of the model suggests a program of future developments that includes a
complementary approach to masses based on an independently determined monopole
Hamiltonian, a better description of deformations and specific suggestions for
the treatment of three body forces. | nucl-th |
Hyperspherical cluster model for bosons: application to sub-threshold
halo states in helium drops: To describe long-range behaviour of one particle removed from a few- or a
many-body system, a hyperspherical cluster model has been developed. It has
been applied to the ground and first excited states of helium drops with five,
six, eight and ten atoms interacting via a two-body soft gaussian potential.
Convergence of the hyperspherical cluster harmonics expansion is studied for
binding energies, root-mean-squared radii and overlaps of the wave functions of
two helium drops differing by one atom. It was shown that with increasing model
space the functional form of such overlaps at large distances converges to the
correct asymptotic behaviour. The asymptotic normalization coefficients that
quantify the overlaps' amplitudes in this region are calculated. It was also
shown that in the first excited state one helium atom stays far apart from the
rest forming a two-body molecule, or a halo. The probability of finding the
halo atom in the classically-forbidden region of space depends on the
definition of the latter and on the number of atoms in the drop. The total norm
of the overlap integrals, the spectroscopic factor, represents the number of
partitions of a many-body state into a chosen state of the system with one
particle removed. The spectroscopic factors have been calculated and their sum
rules are discussed giving a further insight into the structure of helium
drops. | nucl-th |
Isospin Properties of ($K^-$, $N$) Reactions for the Formation of
Deeply-bound Antikaonic Nuclei: The formation of deeply-bound antikaonic $K^-/\bar{K}^0$ nuclear states by
nuclear ($K^-$, $N$) reactions is investigated theoretically within a
distorted-wave impulse approximation (DWIA), considering the isospin properties
of the Fermi-averaged $K^-+ N \to N + \bar{K}$ elementary amplitudes. We
calculate the formation cross sections of the deeply-bound $\bar{K}$ states by
the ($K^-$, $N$) reactions on the nuclear targets, $^{12}$C and $^{28}$Si, at
incident $K^-$ lab momentum $p_{K^-}$ = 1.0 GeV/c and $\theta_{\rm lab} =
0^{\circ}$, introducing a complex effective nucleon number $N_{\rm eff}$ for
unstable bound states in the DWIA. The results show that the deeply-bound
$\bar{K}$ states can be populated dominantly by the ($K^-$, $n$) reaction via
the total isoscalar $\Delta T=0$ transition owing to the isospin nature of the
$K^-+ N \to N + \bar{K}$ amplitudes, and that the cross sections described by
${\rm Re}N_{\rm eff}$ and ${\rm Arg}N_{\rm eff}$ enable to deduce the structure
of the $\bar{K}$ nuclear states; the calculated inclusive nucleon spectra for a
deep $\bar{K}$-nucleus potential do not show distinct peak structure in the
bound region. The few-body $\bar{K}\otimes [NN]$ and $\bar{K}\otimes [NNN]$
states formed in ($K^-$, $N$) reactions on $s$-shell nuclear targets, $^3$He,
$^3$H and $^4$He, are also discussed. | nucl-th |
Extracting meson-baryon contributions to the electroexcitation of the
$N(1675){\frac{5}{2}}^-$ nucleon resonance: We report on the determination of the electrocouplings for the transition
from the proton to the $N(1675){\frac{5}{2}}^-$ resonance state using recent
differential cross section data on $e p \rightarrow e\pi^+ n$ by the CLAS
collaboration at $1.8 \le Q^2 < 4.5$GeV$^2$. The data have been analyzed using
two different approaches, the unitary isobar model and fixed-t dispersion
relations. The extracted $\gamma^* p\rightarrow N(1675){\frac{5}{2}}^-$
helicity amplitudes show considerable coupling through the $A^p_{1/2}$
amplitude, that is significantly larger than predicted three-quark contribution
to this amplitude. The amplitude $A^p_{3/2}$ is much smaller. Both results are
consistent with the predicted sizes of the meson-baryon contributions at $Q^2
\geq 1.8 $GeV$^2$ from the dynamical coupled-channel model. | nucl-th |
Dynamical and sequential decay effects on isoscaling and density
dependence of the symmetry energy: The isoscaling properties of the primary and final products are studied via
isospin dependent quantum molecular dynamics
(IQMD) model and the followed sequential decay model GEMINI, respectively. It
is found that the isoscaling parameters $\alpha$ of both primary and final
products keep no significant change for light fragments, but increases with the
mass for intermediate and heavy products. The dynamical effects on isoscaling
are exhibited by that $\alpha$ value decreases a little with the evolution time
of the system, and opposite trend for the heavy products. The secondary decay
effects on isoscaling are reflected in the increasing of the $\alpha$ value for
the final products which experiences secondary decay process.
Furthermore the density dependence of the symmetry energy has also been
explored, it is observed that in the low densities the symmetry energy
coefficient has the form of $C_{sym}(\rho)\sim C_{0}(\rho/\rho_{0})^{\gamma}$,
where $\gamma = 0.7 \sim 1.3$ for both primary and final products, but $C_{0}$
have different values for primary and final products. It is also suggested that
it might be more reasonable to describe the density dependence of the symmetry
energy coefficient by the $C_{sym}(\rho/\rho_{0})\approx
C_{1}(\rho/\rho_{0})^{\gamma_{soft}} + C_{2}(\rho/\rho_{0})^{\gamma_{stiff}}$
with $\gamma_{soft}\leq 1$, $\gamma_{stiff}\geq 1$ and $C_{1}, C_{2}$ constant
parameters. | nucl-th |
Improving proton-induced one-nucleon removal in intranuclear cascade: It is a well-established fact that intranuclear-cascade models generally fail
to consistently reproduce the cross sections for one-proton and one-neutron
removal from stable nuclei by a high-energy proton beam. We use simple
shell-model calculations to investigate the reasons of this deficiency. We find
that a refined description of the neutron skin and of the energy density in the
nuclear surface is crucial for the aforementioned observables, and that neither
ingredient is sufficient if taken separately. As a by-product, the predictions
for removal of several nucleons are also improved by the refined treatment. | nucl-th |
Compressional properties of nuclear matter in the relativistic mean
field theory with the excluded volume effects: Compressional properties of nuclear matter are studied by using the mean
field theory with the excluded volume effects of the nucleons. It is found that
the excluded volume effects make it possible to fit the empirical data of the
Coulomb coefficient $K_{c}$ of nucleus incompressibility, even if the volume
coefficient $K$ is small($\sim 150$MeV). However, the symmetry properties favor
$K=300\pm 50$MeV as in the cases of the mean field theory of point-like
nucleons. | nucl-th |
Mass asymmetry effects on geometry of vanishing flow: Mass asymmetry effects on geometry of vanishing flow. | nucl-th |
Net-proton number fluctuations in the presence of the QCD critical point: Event-by-event fluctuations of the net-proton number studied in heavy-ion
collisions provide an important means in the search for the conjectured
critical end point (CP) in the QCD phase diagram. We propose a phenomenological
model in which the fluctuations of the chiral critical mode couple to protons
and anti-protons. This allows us to study the behavior of the net-proton number
fluctuations in the presence of the CP. Calculating the net-proton number
cumulants, $C_n$ with n=1,2,3,4, along the phenomenological freeze-out line we
show that the ratio of variance and mean $C_2/C_1$, as well as kurtosis
$C_4/C_2$ resemble qualitative properties observed in data in heavy-ion
collisions as a function of beam energy obtained by the STAR Collaboration at
RHIC. In particular, the non-monotonic structure of the kurtosis and smooth
change of the $C_2/C_1$ ratio with beam energy could be due to the CP located
near the freeze-out line. The skewness, however, exhibits properties that are
in contrast to the criticality expected due to the CP. The dependence of our
results on the model parameters and the proximity of the chemical freeze-out to
the critical point are also discussed. | nucl-th |
Role of non-gaussian quantum fluctuations in neutrino entanglement: The flavor evolution of neutrinos in environments with large neutrino number
densities is an open problem at the nexus of astrophysics and neutrino flavor
physics. Among the many unanswered questions pertaining to this problem, it
remains to be determined whether neutrino-neutrino coherent scattering can give
rise to nontrivial quantum entanglement among neutrinos, and whether this can
affect the flavor evolution in a meaningful way. To gain further insight into
this question, here we study a simple system of two interacting neutrino beams,
and obtain the exact phase-space explored by this system using the Husimi
quasi-probability distribution. We observe that the entanglement induced by the
coupling leads to strong delocalization in phase-space with largely
non-Gaussian quantum fluctuations. The link between the neutrino entanglement
and quantum fluctuations is illustrated using the one- and two-neutrino
entropy. In addition, we propose an approximate phase-space method to describe
the interacting neutrinos problem, where the exact evolution is replaced by a
set of independent mean-field evolutions with a statistical sampling of the
initial conditions. The phase-space approach provides a simple and accurate
method to describe the gross features of the neutrino entanglement problem.
Applications are shown using time-independent and time-dependent Hamiltonians
in the non-adiabatic regime. | nucl-th |
On the structure in the $ΛN$ cross section at the $ΣN$
threshold: The complexity of threshold phenomena is exemplified on a prominent and
long-known case - the structure in the $\Lambda p$ cross section (invariant
mass spectrum) at the opening of the $\Sigma N$ channel. The mass splitting
between the $\Sigma$ baryons together with the angular momentum coupling in the
$^3S_1$-$^3D_1$ partial wave imply that, in principle, up to six channels are
involved. Utilizing hyperon-nucleon potentials that provide an excellent
description of the available low-energy $\Lambda p$ and $\Sigma N$ scattering
data, the shape of the resulting $\Lambda p$ cross section is discussed and the
poles near the $\Sigma N$ threshold are determined. Evidence for a strangeness
$S=-1$ dibaryon is provided, in the form of a deuteron-like (unstable) $\Sigma
N$ bound state. Predictions for level shifts and widths of $\Sigma^-p$ atomic
states are given. | nucl-th |
Nonperturbative Quantum Field Evolution: We introduce a nonperturbative, first-principles approach to time-dependent
problems in quantum field theory. In this approach, the time-evolution of
quantum field configurations is calculated in real time and at the amplitude
level. This method is particularly suitable for treating systems interacting
with a time-dependent background field. As a test problem, we apply this
approach to QED and study electron acceleration and the associated photon
emission in a time- and space-dependent electromagnetic background field. | nucl-th |
A Monte Carlo approach to study neutron and fragment emission in
heavy-ion reactions: Quantum Molecular Dynamics models (QMD) are Monte Carlo approaches targeted
at the description of nucleon-ion and ion-ion collisions. We have developed a
QMD code, which has been used for the simulation of the fast stage of ion-ion
collisions, considering a wide range of system masses and system mass
asymmetries. The slow stage of the collisions has been described by statistical
methods. The combination of both stages leads to final distributions of
particles and fragments, which have been compared to experimental data
available in literature. A few results of these comparisons, concerning neutron
double-differential production cross-sections for C, Ne and Ar ions impinging
on C, Cu and Pb targets at 290 - 400 MeV/A bombarding energies and fragment
isotopic distributions from Xe + Al at 790 MeV/A, are shown in this paper. | nucl-th |
Density-dependent effective nucleon-nucleon interaction from chiral
three-nucleon forces: We derive density-dependent corrections to the in-medium nucleon-nucleon
interaction from the leading-order chiral three-nucleon force. To this order
there are six distinct one-loop diagrams contributing to the in-medium
nucleon-nucleon scattering T-matrix. Analytic expressions are presented for
each of these in both isospin-symmetric nuclear matter as well as nuclear
matter with a small isospin asymmetry. The results are combined with the
low-momentum nucleon-nucleon potential V(low-k) to obtain an effective
density-dependent interaction suitable for nuclear structure calculations. The
in-medium interaction is decomposed into partial waves up to orbital angular
momentum L = 2. Our results should be particularly useful in calculations where
an exact treatment of the chiral three-nucleon force would otherwise be
computationally prohibitive. | nucl-th |
Emergence of low-energy monopole strength in the neutron-rich calcium
isotopes: The isoscalar monopole response of neutron-rich nuclei is sensitive to both
the incompressibility coefficient of symmetric nuclear matter and the density
dependence of the symmetry energy. The main goal of this paper is to explore
the emergence, evolution, and origin of low energy monopole strength along the
even-even calcium isotopes: from 40Ca to 60Ca. The distribution of isoscalar
monopole strength is computed in a relativistic random phase approximation
(RPA) using three effective interactions that have been calibrated to the
properties of finite nuclei and neutron stars. A non-spectral approach is
adopted that allows for an exact treatment of the continuum without any
reliance on discretization. For the stable calcium isotopes, no evidence of
low-energy monopole strength is observed, even as the 1f7/2 neutron orbital is
being filled and the neutron-skin thickness progressively grows. Further, in
contrast to experimental findings, a mild softening of the monopole response
with increasing mass number is predicted. Beyond 48Ca, a significant amount of
low-energy monopole strength emerges as soon as the weak-binding neutron
orbitals (2p and 1f5/2) become populated. The emergence and evolution of
low-energy strength is identified with transitions from these weakly-bound
states into the continuum. Moreover, given that models with a soft symmetry
energy tend to reach the neutron-drip line earlier than their stiffer
counterparts, we identify an inverse correlation between the neutron-skin
thickness and the inverse energy weighted sum. | nucl-th |
Near threshold laser-modified proton emission in nuclear photoeffect: The change of the probability of proton emission in nuclear photoeffect due
to an intense coherent (laser) field is discussed near the threshold, where the
hindering effect of the Coulomb field of the remainder nucleus is essential.
The ratio of laser-assisted and laser free differential cross section is
deduced and found to be independent of the polarization state of the $\gamma $
field and the two types of initial nuclear state considered. The numerical
values of this ratio are given at some characteristic parameters of the intense
field. | nucl-th |
Infinite-cutoff renormalization of the chiral nucleon-nucleon
interaction at N3LO: Naively, the "best" method of renormalization is the one where a momentum
cutoff is taken to infinity while maintaining stable results due to a
cutoff-dependent adjustment of counterterms. We have applied this
renormalization method in the non-perturbative calculation of phase-shifts for
nucleon-nucleon (NN) scattering using chiral NN potentials up to
next-to-next-to-next-to-leading order (N3LO). For lower partial waves, we find
that there is either no convergence with increasing order or, if convergence
occurs, the results do not always converge to the empirical values. For higher
partial waves, we always observe convergence to the empirical phase shifts
(except for the 3G5 state). Furthermore, no matter what the order is, one can
use only one or no counterterm per partial wave, creating a rather erratic
scheme of power counting that does not allow for a systematic order-by-order
improvement of the predictions. The conclusion is that infinite-cutoff
renormalization is inappropriate for chiral NN interactions, which should not
come as a surprise, since the chiral effective field theory, these interactions
are based upon, is designed for momenta below the chiral-symmetry breaking
scale of about 1 GeV. Therefore, this value for the hard scale should also be
perceived as the appropriate upper limit for the momentum cutoff. | nucl-th |
Origin of the structures observed in $e^+e^-$ annihilation into
multipion states around the $\bar pp$ threshold: We analyze the origin of the structures observed in the reactions $e^+e^-\to
3(\pi^+\pi^-)$, $2(\pi^+\pi^-\pi^0)$, $\omega\pi^+\pi^-\pi^0$, and $e^+e^-\to
2(\pi^+\pi^-)\pi^0$ around the antiproton-proton ($\bar pp$) threshold. We
calculate the contribution of the two-step process $e^+e^-\to \bar NN \to$
multipions to the total reaction amplitude. The amplitude for $e^+e^-\to \bar
NN$ is constrained from near-threshold data on the $e^+e^-\to \bar pp$ cross
section and the one for $\bar NN \to$ multipions can be likewise fixed from
available experimental information, for all those $5 \pi$ and $6\pi$ states.
The resulting amplitude for $e^+e^-\to$ multipions turns out to be large enough
to play a role for the considered $e^+e^-$ annihilation channels and, in three
of the four reactions, even allows us to reproduce the data quantitatively near
the $\bar NN$ threshold. The structures seen in the experiments emerges then as
a threshold effect due to the opening of the $\bar NN$ channel. | nucl-th |
The basic K nuclear cluster K- pp and its enhanced formation in the p +
p -> K+ + X reaction: We have studied the structure of K- pp nuclear cluster comprehensively by
solving this three-body system exactly in a variational method starting from
the Ansatz that the Lambda(1405) resonance (Lambda*) is a K-p bound state. We
have found that our original prediction for the presence of K-pp as a compact
bound system with M = 2322$ MeV/c2, B = 48 MeV and Gamma = 60 MeV remains
unchanged by varying the Kba-rN and NN interactions widely as far as they
reproduce Lambda(1405). The structure of K- pp reveals a molecular feature,
namely, the K- in Lambda* as an "atomic center" plays a key role in producing
strong covalent bonding with the other proton. We have shown that the
elementary process, p + p -> K+ + Lambda* + p, which occurs in a short impact
parameter and with a large momentum transfer (Q ~ 1.6$ GeV/c), leads to
unusually large self-trapping of Lambda* by the participating proton, since the
Lambda*-p system exists as a compact doorway state propagating to K- pp
(R{Lambda*-p} ~ 1.67 fm). | nucl-th |
Double beta decay in heavy deformed nuclei: what have we learned?: The pseudo SU(3) approach is used to describe low lying states and BE(2)
intensities of rare earth and actinide nuclei which are double beta decay
candidates. The double beta half lives of some of these nuclei to the ground
and excited states of the final ones are evaluated for both the two and zero
neutrino emitting modes. The existence of selection rules which strongly
restrict the decays is discussed. These restrictions represent a possible test
of the model. Up to now the predictions are in good agreement with the
available experimental data. | nucl-th |
Relaxation time ansatz and shear and bulk viscosities of gluon matter: Shear and bulk viscosity-to-entropy density ratios are calculated for the
pure gluon matter in a non-equilibrium mean-field quasiparticle approach within
the relaxation time approximation. We study how different approximations used
in the literature affect the results for the shear and bulk viscosities. Though
the results for the shear viscosity turned out to be quite robust, all
evaluations of the shear and bulk viscosities obtained in the framework of the
relaxation time approximation can be considered only as rough estimations. | nucl-th |
Estimate of the location of the neutron drip line for calcium isotopes
from an exact Hamiltonian with continuum pair correlations: The eastern region of the calcium isotope chain of the nuclei chart is,
nowadays, of great activity. The experimental assessment of the limit of
stability is of interest to confirm or improve microscopic theoretical models.
The goal of this work is to provide the drip line of the calcium isotopes from
the exact solution of the pairing Hamiltonian which incorporates explicitly the
correlations with the continuum spectrum of energy. The modified Richardson
equations, which include correlations with the continuum spectrum of energy
modeled by the continuum single particle level density, is used to solve the
many-body system. Three models are used, two isospin independent models with
core 40Ca and 48Ca, and one isospin dependent model. One and two-neutron
separation energies and occupation probabilities for bound and continuum states
are calculated from the solution of the Richardson equations. The one particle
drip line is found at the nucleus 57Ca, while the two neutron drip line is
found at the nucleus 60Ca from the isospin independent model and at 66Ca from
the isospin dependent one. | nucl-th |
A New Topological "Twist" to BR Scaling: When vector mesons are considered on the same footing as pions as suggested
by hidden local symmetry, the property of the nuclear tensor forces is strongly
controlled by the behavior of the vector mesons in dense medium. This led to BR
scaling in 1991. When baryons as skyrmions are put on crystal, there can be a
phase transition from skyrmions to half-skyrmions at a density above that of
normal nuclear matter. This topology change can induce fundamental changes to
the parameters in hidden local symmetric Lagrangian, hence BR scaling, and
brings a drastic modification to the structure of nuclear forces, in
particulrar, the tensor forces. This can have far-reaching consequences on the
EoS of compact-star matter and the structure of neutron-rich nuclei. | nucl-th |
From quark and nucleon correlations to discrete symmetry and clustering
in nuclei: Starting with a quark model of nucleon structure in which the valence quarks
are strongly correlated within a nucleon, the light nuclei are constructed by
assuming similar correlations of the quarks of neighboring nucleons. Applying
the model to larger collections of nucleons reveals the emergence of the
face-centered cubic (FCC) symmetry at the nuclear level. Nuclei with closed
shells possess octahedral symmetry. Binding of nucleons are provided by quark
loops formed by three and four nucleon correlations. Quark loops are
responsible for formation of exotic (borromean) nuclei, as well. The model
unifies independent particle (shell) model, liquid-drop and cluster models. | nucl-th |
Refractive Distortions of Two-Particle Correlations: Using optical model calculations it has recently been shown that refractive
phenomena from the collective mean field can significantly alter the sizes
inferred from two-pion correlations. We demonstrate that such effects can be
accounted for in classical calculations if mean field effects are included. | nucl-th |
Hot and Dense Matter Equation of State Probability Distributions for
Astrophysical Simulations: We add an ensemble of nuclei to the equation of state for homogeneous
nucleonic matter to generate a new set of models suitable for astrophysical
simulations of core-collapse supernovae and neutron star mergers. We implement
empirical constraints from (i) nuclear mass measurements, (ii) proton-proton
scattering phase shifts, and (iii) neutron star observations. Our model is also
guided by microscopic many-body theory calculations based on realistic nuclear
forces, including the zero-temperature neutron matter equation of state from
quantum Monte Carlo simulations and thermal contributions to the free energy
from finite-temperature many-body perturbation theory. We ensure that the
parameters of our model can be varied while preserving thermodynamic
consistency and the connection to experimental or observational data, thus
providing a probability distribution of the astrophysical hot and dense matter
equation of state. We compare our results with those obtained from other
available equations of state. While our probability distributions indeed
represent a large number of possible equations of state, we cannot yet claim to
have fully explored all of the uncertainties, especially with regard to the
structure of nuclei in the hot and dense medium. | nucl-th |
J/Ψproduction, $χ$ polarization and Color Fluctuations: The hard contributions to the heavy quarkonium-nucleon cross sections are
calculated based on the QCD factorization theorem and the nonrelativistic
quarkonium model. We evaluate the nonperturbative part of these cross sections
which dominates at $\sqrt{s_{NN}}\approx 20$ GeV at the Cern Super Proton
Synchrotron (SPS) and becomes a correction at $\sqrt{s_{NN}}\approx 6$ TeV at
the CERN Large Hadron Collider (LHC). $\J$ production at the CERN SPS is well
described by hard QCD, when the larger absorption cross sections of the $\chi$
states predicted by QCD are taken into account. We predict an $A$-dependent
polarization of the $\chi$ states. The expansion of small wave packets is
discussed. | nucl-th |
Particle production from off-shell nucleons: Particle production in equilibrium and nonequilibrium quantum systems is
calculated. The effects of the off-shell propagation of nucleons in medium on
the particle production are discussed. Comparision to the semiclassical
production rate is given. | nucl-th |
Effect of the Quark-Gluon Vertex on Dynamical Chiral Symmetry Breaking: In this work, we investigate how the details of the quark-gluon interaction
vertex affect the quantitative description of chiral symmetry breaking through
the gap equation for quarks. We start from two gluon propagator models widely
used in literature and constructed in direct connection with our gradually
improved understanding of infrared quantum chromodynamics coupled with its
exact one-loop limit. The gap equation is then solved by employing a variety of
vertex \emph{Ans\"atze}, which have been constructed in order to implement some
of the key aspects of quantum chromodynamics, namely, multiplicative
renormalizability of the quark propagator, gauge invariance, matching with
perturbation theory in the weak coupling regime, independence from unphysical
kinematic singularities as well as manifestly correct transformation properties
under charge conjugation and parity operations. On general grounds, all
truncation schemes exhibit the same qualitative and quantitative pattern of
chiral symmetry breaking, ensuring the overall robustness of this approach and
its potentially reliable description of the hadron spectrum and properties. | nucl-th |
Dynamical coupled-channel study of K+ Lambda photoproduction: Results for the reaction gamma p --> K+ Lambda, studied within a constituent
quark model and a dynamical coupled-channel approach, are presented and
compared with recent data. Issues related to the search for missing baryon
resonances are briefly discussed and the role played by a third S_{11}
resonance is underlined. | nucl-th |
Microscopic in-medium nucleon-nucleon cross sections with improved Pauli
blocking effects: We present updated predictions of effective elastic nucleon-nucleon cross
sections intended for use in nucleus-nucleus reactions. A novel characteristic
of the present approach combines all microscopic medium effects included in the
Dirac-Brueckner-Hartree-Fock G-matrix with a Pauli blocking mechanism which is
more appropriate for applications in ion-ion reaction models as compared to a
previous approach. The effective in-medium cross section is found to be quite
sensitive to the description of Pauli blocking in the final configurations. | nucl-th |
Gamow-Teller GT+ distributions in nuclei with mass A=90-97: We investigate the Gamow-Teller strength distributions in the
electron-capture direction in nuclei having mass A=90-97, assuming a 88Sr core
and using a realistic interaction that reasonably reproduces nuclear
spectroscopy for a wide range of nuclei in the region as well as experimental
data on Gamow-Teller strength distributions. We discuss the systematics of the
distributions and their centroids. We also predict the strength distributions
for several nuclei involving stable isotopes that should be experimentally
accessible for one-particle exchange reactions in the near future. | nucl-th |
Fully antisymmetrised dynamics for bulk fermion systems: The neutron star's crust and mantel are typical examples of non-uniform bulk
systems with spacial localisations. When modelling such systems at low
temperatures, as is the case in the crust, one has to work with antisymmetrised
many-body states to get the correct fermion behaviour. Fermionic molecular
dynamics, which works with an antisymmetrised product of localised wave
packets, should be an appropriate choice. Implementing periodic boundary
conditions into the fermionic molecular dynamics formalism would allow the
study of the neutron star's crust as a bulk quantum system. Unfortunately, the
antisymmetrisation is a non-local entanglement which reaches far out of the
periodically repeated unit cell. In this proceeding, we give a brief overview
how periodic boundary conditions and fermionic molecular dynamics can be
combined without truncating the long-range many-body correlation induced by the
antisymmetry of the many-body state. | nucl-th |
Dynamical Model for Meson Production off Nucleon and Application to
Neutrino-Nucleus Reactions: I explain the Sato-Lee (SL) model and its extension to the neutrino-induced
pion production off the nucleon. Then I discuss applications of the SL model to
incoherent and coherent pion productions in the neutrino-nucleus scattering. I
mention a further extension of this approach with a dynamical coupled-channels
model developed in Excited Baryon Analysis Center of JLab. | nucl-th |
Breakup Reactions of 11Li within a Three-Body Model: We use a three-body model to investigate breakup reactions of 11Li (n+n+9Li)
on a light target. The interaction parameters are constrained by known
properties of the two-body subsystems, the 11Li binding energy and
fragmentation data. The remaining degrees of freedom are discussed. The
projectile-target interactions are described by phenomenological optical
potentials. The model predicts dependence on beam energy and target,
differences between longitudinal and transverse momentum distributions and
provides absolute values for all computed differential cross sections. We give
an almost complete series of observables and compare with corresponding
measurements. Remarkably good agreement is obtained. The relative neutron-9Li
p-wave content is about 40%. A p-resonance, consistent with measurements at
about 0.5 MeV of width about 0.4 MeV, seems to be necessary. The widths of the
momentum distributions are insensitive to target and beam energy with a
tendency to increase towards lower energies. The transverse momentum
distributions are broader than the longitudinal due to the diffraction process.
The absolute values of the cross sections follow the neutron-target cross
sections and increase strongly for beam energies decreasing below 100 MeV/u. | nucl-th |
Precise comparison of the Gaussian expansion method and the Gamow shell
model: We perform a detailed comparison of results of the Gamow Shell Model (GSM)
and the Gaussian Expansion Method (GEM) supplemented by the complex scaling
(CS) method for the same translationally-invariant cluster-orbital shell model
(COSM) Hamiltonian. As a benchmark test, we calculate the ground state $0^{+}$
and the first excited state $2^{+}$ of mirror nuclei $^{6}$He and $^{6}$Be in
the model space consisting of two valence nucleons in $p$-shell outside of a
$^{4}$He core. We find a good overall agreement of results obtained in these
two different approaches, also for many-body resonances. | nucl-th |
The nucleon resonances in the $J/ψ\to p\bar{p}η'$ decay: We are aiming to study the $J/\psi \to p\bar{p}\eta'$ decay in an isobar
model and the effective Lagrangian approach. After a careful exploration of the
contributions of the $S_{11}(1535)$, $P_{11}(1710)$, $P_{13}(1900)$,
$S_{11}(2090)$ and $P_{11}(2100)$ resonances, we conclude that either a
subthreshold resonance or a broad $P$-wave state in the near threshold range
seems to be indispensable to describe present data of the $\pi N \to \eta'N$.
Furthermore, at least one broad resonance above $\eta'N$ threshold is
preferred. With this detailed analysis, we could give the invariant mass
spectrum and Dalitz plot of the $J/\psi \to p\bar{p}\eta'$ decay for the
purpose of assisting the future detailed partial wave analysis. It is found
that the $J/\psi \to p\bar{p}\eta'$ data are useful for disentangling the above
or below threshold resonant contribution, though it still further needs the
differential cross section data of $\pi N \to \eta'N$ to realize some of the
resonant and the non-resonant contribution. Our results are enlightening for
the $\eta'N$ production mechanism and the properties of the nucleon resonances
with the mass around 2.0~GeV. | nucl-th |
Transfer/Breakup Channel Couplings in Sub-barrier Fusion Reactions: With the recent availability of state-of-the-art radioactive ion beams, there
has been a renew interest in the investigation of nuclear reactions with heavy
ions near the Coulomb barrier. The role of inelastic and transfer channel
couplings in fusion reactions induced by stable heavy ions can be revisited.
Detailed Analysis of recent experimental fusion cross sections by using
standard coupled-channel calculations is first discussed. Multi-neutron
transfer effects are introduced in the fusion process below the Coulomb barrier
by analyzing 32S+90,96Zr as benchmark reactions. The enhancement of fusion
cross sections for 32S+96Zr is well reproduced at sub-barrier energies by NTFus
code calculations including the coupling of the neutron-transfer channels
following the Zagrebaev semi-classical model. Similar effects for 40Ca+90Zr and
40Ca+96Zr fusion excitation functions are found. The breakup coupling in both
the elastic scattering and in the fusion process induced by weakly bound stable
projectiles is also shown to be crucial. In the second part of this work, full
coupled-channel calculations of the fusion excitation functions are performed
by using the breakup coupling for the more neutron-rich reaction and for the
more weakly bound projectiles. we clearly demonstrate that
Continuum-Discretized Coupled-Channel calculations are capable to reproduce the
fusion enhancement from the breakup coupling in 6Li+59Co. | nucl-th |
Generic Constraints on the Relativistic Mean-Field and
Skyrme-Hartree-Fock Models from the Pure Neutron Matter Equation of State: We study the nuclear symmetry energy S(rho) and related quantities of nuclear
physics and nuclear astrophysics predicted generically by relativistic
mean-field (RMF) and Skyrme-Hartree-Fock (SHF) models. We establish a simple
prescription for preparing equivalent RMF and SHF parametrizations starting
from a minimal set of empirical constraints on symmetric nuclear matter,
nuclear binding energy and charge radii, enforcing equivalence of their Lorenz
effective masses, and then using the pure neutron matter (PNM) equation of
state (EoS) obtained from ab-initio calculations to optimize the pure isovector
parameters in the RMF and SHF models. We find the resulting RMF and SHF
parametrizations give broadly consistent predictions of the symmetry energy J
and its slope parameter L at saturation density within a tight range of <~2 MeV
and <~6 MeV respectively, but that clear model dependence shows up in the
predictions of higher-order symmetry energy parameters, leading to important
differences in (a) the slope of the correlation between J and L from the
confidence ellipse, (b) the isospin-dependent part of the incompressibility of
nuclear matter K_tau, (c) the symmetry energy at supra-saturation densities,
and (d) the predicted neutron star radii. The model dependence can lead to
about 1-2 km difference in predictions of the neutron star radius given
identical predicted values of J, L and symmetric nuclear matter (SNM)
saturation properties. Allowing the full freedom in the effective masses in
both models leads to constraints of 30<~J<~31.5 MeV, 35<~L<~60 MeV,
-330<~K_tau<~-216 MeV for the RMF model as a whole and 30<~J<~33 MeV, 28<~L<~65
MeV, -420<~K_tau<~-325 MeV for the SHF model as a whole. Notably, given PNM
constraints, these results place RMF and SHF models as a whole at odds with
some constraints on K_tau inferred from giant monopole resonance and neutron
skin experimental results. | nucl-th |
Removal of $K$-mixing in angular momentum projected nuclear wave
functions: Angular momentum projection plays a key role in studying nuclei and other
quantum many-body systems with rotational invariance. In this Letter, we report
a new fundamental feature of the angular momentum projection, which clearly
tells us the frequently discussed $K$-mixing in the angular momentum projected
nuclear wave function can be safely removed. At a given spin $J$, one can
generate $2J+1$ angular momentum projected states from a deformed Slater
determinant. These projected states are labeled with different $K$ numbers.
Usually, a nuclear wave function with $K$-mixing can be expressed as an
expansion in terms of all these $2J+1$ projected states. The coefficients in
this expansion can be obtained by solving the Hill-Wheeler equation.
Strikingly, we found that such nuclear wave function with $K$-mixing can always
be equivalently replaced by a single projected state generated from another
Slater determinant. Consequently, such nuclear wave function can be
significantly simplified, especially for high-spin states. This also reminds us
that the $K$-mixing in the angular momentum projected nuclear wave functions,
adopted by many present-day nuclear models, does not carry any physical
meaning, and is essentially different from that $K$-mixing caused by the
Coriolis force in the cranked shell model. | nucl-th |
Short History of Nuclear Many-Body Problem: This is a very short presentation regarding developments in the theory of
nuclear many-body problems, as seen and experienced by the author during the
past 60 years with particular emphasis on the contributions of Gerry Brown and
his research-group. Much of his work was based on Brueckner's formulation of
the nuclear many-body problem. It is reviewed briefly together with the
Moszkowski-Scott separation method that was an important part of his early
work. The core-polarisation and his work related to effective interactions in
general are also addressed. | nucl-th |
Nuclear response for the Skyrme effective interaction with zero-range
tensor terms. II. Sum rules and instabilities: The formalism of linear response theory for Skyrme forces including tensor
terms presented in article [1] is generalized for the case of a Skyrme energy
density functional in infinite matter. We also present analytical results for
the odd-power sum rules, with particular attention to the inverse energy
weighted sum rule, $M_{-1}$, as a tool to detect instabilities in Skyrme
functionals. | nucl-th |
Proto-Strange Quark Star Structure: In this paper, we investigate the newborn strange quark stars with constant
entropy. We also use the MIT bag model to calculate the thermodynamic
properties in two cases; the density-dependent bag constant and the fixed bag
constant (B = 90 MeV). We show that the equation of state becomes stiffer by
using the density dependent bag constant and by increasing the entropy.
Furthermore, we show that the adiabatic index of the system reaches to 4/3 at
high densities. Later, we calculate the structure of a strange quark star using
the equation of state and the general relativistic equations of hydrostatic
equilibrium, the Tolman-Oppenheimer-Volkoff (TOV) equations. We show that the
gravitational mass of the star decreases by increasing the entropy and the
maximum gravitational mass is larger when we use the density-dependent bag
constant at fixed central energy density. It is shown that the mass-radius
relation for this system obeys M R^ 3 for different cases of the calculations.
Finally, we show that for a given stellar mass considering the fixed bag
constant, the maximum gravitational red shift of a strange quark star occurs at
larger values of entropy. | nucl-th |
Daejeon16 NN Interaction: We have developed a realistic nucleon-nucleon (NN) interaction, dubbed
Daejeon16. We start from a SRG (similarity renormalization group) evolved
chiral N3LO interaction. We then apply PETs (phase-equivalent transformations)
to the SRG-evolved interaction. It turned out that the obtained in such a way
Daejeon16 NN interaction provides a good description of various observables in
light nuclei without NNN forces. In this contribution, we present our new
results for some selected nuclei using the ab initio no-core shell model (NCSM)
with the Daejeon16 interaction. One of the interesting results is that the ab
initio NCSM with Daejeon16 clearly demonstrates the phenomenon of parity
inversion in Be-11, i.e., the ground state in Be-11 has the spin-parity (1/2,
+) in experiments contrary to the expectation from the conventional shell model | nucl-th |
Heavy Ion Dynamics and Neutron Stars: Some considerations are reported, freely inspired from the presentations and
discussions during the Beijing Normal University Workshop on the above Subject,
held in July 2007. Of course this cannot be a complete summary but just a
collection of personal thougths aroused during the meeting. | nucl-th |
Surface effects in color superconducting strange-quark matter: Surface effects in strange-quark matter play an important role for certain
observables which have been proposed in order to identify strange stars, and
color superconductivity can strongly modify these effects. We study the surface
of color superconducting strange-quark matter by solving the
Hartree-Fock-Bogoliubov equations for finite systems ("strangelets") within the
MIT bag model, supplemented with a pairing interaction. Due to the bag-model
boundary condition, the strange-quark density is suppressed at the surface.
This leads to a positive surface charge, concentrated in a layer of ~1 fm below
the surface, even in the color-flavor locked (CFL) phase. However, since in the
CFL phase all quarks are paired, this positive charge is compensated by a
negative charge, which turns out to be situated in a layer of a few tens of fm
below the surface, and the total charge of CFL strangelets is zero. We also
study the surface and curvature contributions to the total energy. Due to the
strong pairing, the energy as a function of the mass number is very well
reproduced by a liquid-drop type formula with curvature term. | nucl-th |
Isospin-symmetry breaking in superallowed Fermi beta-decay due to
isospin-nonconserving forces: We investigate isospin-symmetry breaking effects in the sd-shell region with
large-scale shell-model calculations, aiming to understand the recent anomalies
observed in superallowed Fermi beta-decay. We begin with calculations of
Coulomb displacement energies (CDE's) and triplet displacement energies (TDE's)
by adding the T=1,J=0 isospin nonconserving (INC) interaction into the usual
isospin-invariant Hamiltonian. It is found that CDE's and TDE's can be
systematically described with high accuracy. A total number of 122 one- and
two-proton separation energies are predicted accordingly, and locations of the
proton drip-line and candidates for proton-emitters are thereby suggested.
However, attempt to explain the anomalies in the superallowed Fermi beta-decay
fails because these well-fitted T=1,J=0 INC interactions are found no effects
on the nuclear matrix elements. It is demonstrated that the observed large
isospin-breaking correction in the 32Cl beta-decay, the large isospin-mixing in
the 31Cl beta-decay, and the small isospin-mixing in the 23Al beta-decay can be
consistently understood by introducing additional T=1,J=2 INC interactions
related to the s1/2 orbit. | nucl-th |
Microscopic analysis of quasielastic scattering and breakup reactions of
neutron-rich nuclei $^{12,14}$Be: A microscopic analysis of the optical potentials (OPs) and cross sections of
quasielastic scattering of $^{12,14}$Be on $^{12}$C at 56 MeV/nucleon and on
protons at energy near 700 MeV is carried out. For lower energy scattering the
real part of the OP is calculated by using of double-folding procedure
accounting for the anti-symmetrization effects, while the imaginary part is
obtained on the base of the high-energy approximation (HEA). The HEA is also
applied to the calculations of both real and imaginary OPs when solving the
relativistic equation for the high-energy proton-nucleus elastic scattering.
The neutron and proton density distributions computed in different microscopic
models for $^{12}$Be and $^{14}$Be are used. In the present hybrid model of the
optical potential the only free parameters are the depths of the real and
imaginary parts of OP obtained by fitting the experimental data. The role of
the inelastic scattering channel to the first excited $2^{+}$ and $3^{-}$
states in $^{12}$C when calculating the quasielastic cross sections, as well as
the modified density of the $^{12}$C target accounting for the surface effects
are studied. In addition, the cluster model, in which $^{14}$Be consists of a
$2n$-halo and the $^{12}$Be core, is applied to calculate the cross sections of
diffraction breakup and stripping reactions in $^{14}$Be+$^{12}$C scattering
and longitudinal momentum distributions of $^{12}$Be fragments at energy of 56
MeV/nucleon. A good agreement of the theoretical results with the available
experimental data of both quasielstic scattering and breakup processes is
obtained. | nucl-th |
Nuclear deformation in the laboratory frame: We develop a formalism for calculating the distribution of the axial
quadrupole operator in the laboratory frame within the rotationally invariant
framework of the configuration-interaction shell model. The calculation is
carried out using a finite-temperature auxiliary-field quantum Monte Carlo
method. We apply this formalism to isotope chains of even-mass samarium and
neodymium nuclei, and show that the quadrupole distribution provides a
model-independent signature of nuclear deformation. Two technical advances are
described that greatly facilitate the calculations. The first is to exploit the
rotational invariance of the underlying Hamiltonian to reduce the statistical
fluctuations in the Monte Carlo calculations. The second is to determine
quadruple invariants from the distribution of the axial quadrupole operator.
This allows us to extract effective values of the intrinsic quadrupole shape
parameters without invoking an intrinsic frame or a mean-field approximation. | nucl-th |
The role of the likelihood for elastic scattering uncertainty
quantification: Background: Analyses of elastic scattering with the optical model (OMP) are
widely used in nuclear reactions.
Purpose: Previous work compared a traditional frequentist approach and a
Bayesian approach to quantify uncertainties in the OMP. In this study, we
revisit this comparison and consider the role of the likelihood used in the
analysis.
Method: We compare the Levenberg-Marquardt algorithm for $\chi^{2}$
minimization with Markov Chain Monte Carlo sampling to obtain parameter
posteriors. Following previous work, we consider how results are affected when
$\chi^{2}$/N is used for the likelihood function, N being the number of data
points, to account for possible correlations in the model and underestimation
of the error in the data.
Results: We analyze a simple linear model and then move to OMP analysis of
elastic angular distributions using a) a 5-parameter model and b) a 6-parameter
model. In the linear model, the frequentist and Bayesian approaches yield
consistent optima and uncertainty estimates. The same is qualitatively true for
the 5-parameter OMP analysis. For the 6-parameter OMP analysis, the parameter
posterior is no longer well-approximated by a Gaussian and a covariance-based
frequentist prediction becomes unreliable. In all cases, when the Bayesian
approach uses $\chi^{2}$/N in the likelihood, uncertainties increase by
$\sqrt{N}$.
Conclusions: When the parameter posterior is near-Gaussian and the same
likelihood is used, the frequentist and Bayesian approaches recover consistent
parameter uncertainty estimates. If the parameter posterior has significant
higher moments, the covariance-only frequentist approach becomes unreliable and
the Bayesian approach should be used. Empirical coverage can serve as an
important internal check for uncertainty estimation, providing red flags for
uncertainty analyses. | nucl-th |
A hydrodynamic study of hyperon spin polarization in relativistic heavy
ion collisions: We perform a systematic study of the spin polarization of hyperons in
heavy-ion collisions using the MUSIC hydrodynamic model with A Multi-Phase
Transport (AMPT) pre-equilibrium dynamics. Our model calculations nicely
describe the measured collision-energy, centrality, rapidity, and $p_T$
dependence of $\Lambda$ polarization. We also study and predict the global spin
polarization of $\Xi^-$ and $\Omega^-$ as a function of collision energy, which
provides a baseline for the studies of the magnetic moment, spin, and mass
dependence of the spin polarization. For the local spin polarization, we
calculate the radial and azimuthal components of the transverse $\Lambda$
polarization and find specific modulating behavior which could reflect the
circular vortical structure. However, our model fails to describe the
azimuthal-angle dependence of the longitudinal and transverse $\Lambda$
polarization, which indicates that the hydrodynamic framework with the spin
Cooper-Frye formula under the assumption of thermal equilibrium of spin degree
of freedom needs to be improved. | nucl-th |
Effects of momentum conservation on the analysis of anisotropic flow: We present a general method for taking into account correlations due to
momentum conservation in the analysis of anisotropic flow, either by using the
two-particle correlation method or the standard flow vector method. In the
latter, the correlation between the particle and the flow vector is either
corrected through a redefinition (shift) of the flow vector, or subtracted
explicitly from the observed flow coefficient. In addition, momentum
conservation contributes to the reaction plane resolution. Momentum
conservation mostly affects the first harmonic in azimuthal distributions,
i.e., directed flow. It also modifies higher harmonics, for instance elliptic
flow, when they are measured with respect to a first harmonic event plane such
as one determined with the standard transverse momentum method. Our method is
illustrated by application to NA49 data on pion directed flow. | nucl-th |
Stable Bose-Einstein correlations: The shape of Bose-Einstein (or HBT) correlation functions is determined for
the case when particles are emitted from a stable source, obtained after
convolutions of large number of elementary random processes. The two-particle
correlation function is shown to have a {\it stretched exponential} shape,
characterized by the L\'evy index of stability $ 0 < \alpha \le 2$ and the
scale parameter $R$. The normal, Gaussian shape corresponds to a particular
case, when $\alpha = 2$ is selected. The asymmetry parameter of the stable
source, $\beta$ is shown to be proportional to the angle, measured by the
normalized three-particle cumulant correlations. | nucl-th |
Open charm in nuclear matter at finite temperature: We study the properties of open-charm mesons ($D$ and $\bar {D}$) in nuclear
matter at finite temperature within a self-consistent coupled-channel approach.
The meson-baryon interactions are adopted from a type of broken SU(4) s-wave
Tomozawa-Weinberg terms supplemented by an attractive scalar-isoscalar
attraction. The in-medium solution at finite temperature incorporates Pauli
blocking effects, mean-field binding on all the baryons involved, and $\pi$ and
open-charm meson self-energies in a self-consistent manner. In the $DN$ sector,
the $\Lambda_c$ and $\Sigma_c$ resonances, generated dynamically at 2593 MeV
and 2770 MeV in free space, remain close to their free-space position while
acquiring a remarkable width due to the thermal smearing of Pauli blocking as
well as from the nuclear matter density effects. As a result, the $D$ meson
spectral density shows a single pronounced peak for energies close to the $D$
meson free-space mass that broadens with increasing matter density with an
extended tail particularly towards lower energies. The $\bar D$ potential shows
a moderate repulsive behavior coming from the dominant I=1 contribution of the
$\bar D N$ interaction. The low-density theorem is, however, not a good
approximation for the $\bar D$ self-energy in spite of the absence of
resonance-hole contributions close to threshold in this case. We speculate the
possibility of $D$-mesic nuclei as well as discuss some consequences for the
$J/\Psi$ suppression in heavy-ion collisions, in particular for the future CBM
experiment at FAIR. | nucl-th |
Continuum and three-nucleon force in Borromean system: The 17Ne case: Starting from chiral two-nucleon (2NF) and chiral three-nucleon (3NF)
potentials, we present a detailed study of 17Ne, a Borromean system, with the
Gamow shell model which can capture continuum effects. More precisely, we take
advantage of the normal-ordering approach to include the 3NF and the Berggren
representation to treat bound, resonant and continuum states on equal footing
in a complex-momentum plane. In our framework, 3NF is essential to reproduce
the Borromean structure of 17Ne, while the continuum is more crucial for the
halo property of the nucleus. The two-proton halo structure is demonstrated by
calculating the valence proton density and correlation density. The
astrophysically interesting $3/2^-$ excited state has its energy above the
threshold of the proton emission, and therefore the two-proton decay should be
expected from the state. | nucl-th |
Local nucleon-nucleon and three-nucleon interactions within chiral
effective field theory: To obtain an understanding of the structure and reactions of nuclear systems
from first principles has been a long-standing goal of nuclear physics. In this
respect, few- and many-body systems provide a unique laboratory for studying
nuclear interactions. During the past decades, the development of accurate
representations of the nuclear force has undergone substantial progress.
Particular emphasis has been devoted to chiral effective field theory (EFT), a
low-energy effective representation of quantum chromodynamics (QCD). Within
chiral EFT, many studies have been carried out dealing with the construction of
both the nucleon-nucleon ($N\!N$) and three-nucleon ($3N$) interactions. The
aim of the present article is to give a detailed overview of the chiral
interaction models that are local in configuration space, and show recent
results for nuclear systems obtained by employing these local chiral forces. | nucl-th |
Deformation effects in the Coulomb breakup of 31Ne: We present a fully quantum mechanical theory to study the effects of
deformation on various reaction observables in the Coulomb breakup of neutron
rich exotic medium mass nuclei on heavy targets within the framework of finite
range distorted wave Born approximation by using a deformed Woods-Saxon
potential. As an application of this theory, we calculate the one-neutron
removal cross section, relative energy spectra, parallel momentum distributions
and angular distributions in the breakup of 31Ne on Pb and Au targets at 234
MeV/u. We suggest ways to put constraints on the large uncertainty in the
one-neutron separation energy of 31Ne and also argue that if 31Ne is indeed a
halo nucleus then it should be a deformed one. | nucl-th |
Nuclear matter with three-body forces from self-consistent spectral
calculations: We calculate the equation of state of nuclear matter in the self-consistent
T-matrix scheme including three-body nuclear interactions. We study the effect
of the three-body force on the self-energies and spectral functions of nucleons
in medium. | nucl-th |
Towards a New Strategy of Searching for QCD Phase Transition in Heavy
Ion Collisions: We reconsider the Hung and Shuryak arguments in favour of searching for the
deconfinement phase transition in heavy ion collisions {\em downward} from the
nominal SPS energy, at $E_{lab} \approx 30 \ GeV/A$ where the fireball lifetime
is the longest one. Using the recent lattice QCD data and the mixed phase
model, we show that the deconfinement transition might occur at the bombarding
energies as low as $E_{lab}=3 - 5 \ GeV/A$. Attention is drawn to the study of
the mixed phase of nuclear matter in the collision energy range $E_{lab}= 2-10
\ GeV/A$. | nucl-th |
Wavelet Methods in the Relativistic Three-Body Problem: In this paper we discuss the use of wavelet bases to solve the relativistic
three-body problem. Wavelet bases can be used to transform momentum-space
scattering integral equations into an approximate system of linear equations
with a sparse matrix. This has the potential to reduce the size of realistic
three-body calculations with minimal loss of accuracy. The wavelet method leads
to a clean, interaction independent treatment of the scattering singularities
which does not require any subtractions. | nucl-th |
The $S_{E1}$ factor of radiative $α$ capture on $^{12}$C in
effective field theory: The $S_{E1}$ factor of radiative $\alpha$ capture on $^{12}$C is studied in
effective field theory. We briefly discuss the strategy for the calculation of
the reaction and report a first result of $S_{E1}$ at the Gamow-peak energy,
$E_G=0.3$~MeV. | nucl-th |
Bayesian inference of neutron-star observables based on effective
nuclear interactions: Based on the Skyrme-Hartree-Fock model (SHF) as well as its extension (the
Korea-IBS-Daegu-SKKU (KIDS) model) and the relativistic mean-field (RMF) model,
we have studied the constraints on the parameters of the nuclear matter
equation of state (EOS) from adopted astrophysical observables using a Bayesian
approach. While the masses and radii of neutron stars generally favors a stiff
isoscalar EOS and a moderately soft nuclear symmetry energy, model dependence
on the constraints is observed and mostly originates from the incorporation of
higher-order EOS parameters and difference between relativistic and
non-relativistic models. At twice saturation density, the value of the symmetry
energy is constrained to be $48^{+15}_{-11}$ MeV in the standard SHF model,
$48^{+8}_{-15}$ MeV in the KIDS model, and $48^{+5}_{-6}$ MeV in the RMF model,
around their maximum {\it a posteriori} values within $68\%$ confidence
intervals. Our study helps to obtain a robust constraint on nuclear matter EOS,
and meanwhile, to understand the model dependence of the results. | nucl-th |
Coupled fermion and boson production in a strong background mean-field: We derive quantum kinetic equations for fermion and boson production starting
from a phi^4 Lagrangian with minimal coupling to fermions. Decomposing the
scalar field into a mean-field part and fluctuations we obtain spontaneous pair
creation driven by a self-interacting strong background field. The produced
fermion and boson pairs are self-consistently coupled. Consequently back
reactions arise from fermion and boson currents determining the time dependent
self-interacting background mean-field. We explore the numerical solution in
flux tube geometry for the time evolution of the mean-field as well as for the
number- and energy densities for fermions and bosons. We find that after a
characteristic time all energy is converted from the background mean-field to
particle creation. Applying this general approach to the production of
``quarks'' and ``gluons'' a typical time scale for the collapse of the flux
tube is 1.5 fm/c. | nucl-th |
First Order Variational Calculation of Form Factor in a Scalar
Nucleon--Meson Theory: We investigate a relativistic quantum field theory in the particle
representation using a non-perturbative variational technique. The theory is
that of two massive scalar particles, `nucleons' and `mesons', interacting via
a Yukawa coupling. We calculate the general Euclidean Green function involving
two external nucleons and an arbitrary number of external mesons in the
quenched approximation for the nucleons. The non-perturbative renormalization
and truncation is done in a consistent manner and results in the same
variational functional independent of the number of external mesons. We check
that the calculation agrees with one-loop perturbation theory for small
couplings. As an illustration the special case of meson absorption on the
nucleon is considered in detail. We derive the radius of the dressed particle
and numerically investigate the vertex function after analytic continuation to
Minkowski space. | nucl-th |
Porter-Thomas distribution in unstable many-body systems: We use the continuum shell model approach to explore the resonance width
distribution in unstable many-body systems. The single-particle nature of a
decay, the few-body character of the interaction Hamiltonian, and collectivity
that emerges in non-stationary systems due to the coupling to the continuum of
reaction states are discussed. Correlations between structures of the parent
and daughter nuclear systems in the common Fock space are found to result in
deviations of decay width statistics from the Porter-Thomas distribution. | nucl-th |
Equilibration and locality: Experiments motivated by predictions of quantum mechanics indicate
non-trivial correlations between spacelike-separated measurements. The
phenomenon is referred to as a violation of strong-locality and, after
Einstein, called ghostly action at a distance. An intriguing and previously
unasked question is how the evolution of an assembly of particles to
equilibrium-state relates to strong-locality. More specifically, whether, with
this respect, indistinguishable particles differ from distinguishable ones.
To address the question, we introduce a Markov-chain based framework over a
finite set of microstates. For the first time, we formulate conditions needed
to obey the particle transport- and strong-locality for indistinguishable
particles.
Models which obey transport-locality and lead to equilibrium-state are
considered. We show that it is possible to construct models obeying and
violating strong-locality both for indistinguishable particles and for
distinguishable ones. However, we find that only for distinguishable particles
strongly-local evolution to equilibrium is possible without breaking the
microstate-symmetry. This is the strongest symmetry one can impose and leads to
the shortest equilibration time.
We hope that the results presented here may provide a new perspective on a
violation of strong-locality, and the developed framework will help in future
studies. Specifically they may help to interpret results on high-energy nuclear
collisions indicating a fast equilibration of indistinguishable particles. | nucl-th |
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