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Trees and Islands -- Machine learning approach to nuclear physics: We implement machine learning algorithms to nuclear data. These algorithms
are purely data driven and generate models that are capable to capture
intricate trends. Gradient boosted trees algorithm is employed to generate a
trained model from existing nuclear data, which is used for prediction for data
of damping parameter, shell correction energies, quadrupole deformation,
pairing gaps, level densities and giant dipole resonance for large number of
nuclei. We, in particular, predict level density parameter for superheavy
elements which is of great current interest. The predictions made by the
machine learning algorithm is found to have standard deviation from 0.00035 to
0.73. | nucl-th |
Scaling behavior at high p_T and the p/pi ratio: We first show that the pions produced at high $p_T$ in heavy-ion collisions
over a wide range of high energies exhibit a scaling behavior when the
distributions are plotted in terms of a scaling variable. We then use the
recombination model to calculate the scaling quark distribution just before
hadronization. From the quark distribution it is then possible to calculate the
proton distribution at high $p_T$, also in the framework of the recombination
model. The resultant $p/\pi$ ratio exceeds one in the intermediate $p_T$ region
where data exist, but the scaling result for the proton distribution is not
reliable unless $p_T$ is high enough to be insensitive to the scale-breaking
mass effects. | nucl-th |
Combining phase-space and time-dependent reduced density matrix approach
to describe the dynamics of interacting fermions: The possibility to apply phase-space methods to many-body interacting systems
might provide accurate descriptions of correlations with a reduced numerical
cost. For instance, the so--called stochastic mean-field phase-space approach,
where the complex dynamics of interacting fermions is replaced by a statistical
average of mean-field like trajectories is able to grasp some correlations
beyond the mean-field. We explore the possibility to use alternative equations
of motion in the phase-space approach. Guided by the BBGKY hierarchy, equations
of motion that already incorporate part of the correlations beyond mean-field
are employed along each trajectory. The method is called Hybrid Phase-Space
(HPS) because it mixes phase-space techniques and the time-dependent reduced
density matrix approach. The novel approach is applied to the one-dimensional
Fermi-Hubbard model. We show that the predictive power is improved compared to
the original stochastic mean-field method. In particular, in the weak-coupling
regime, the results of the HPS theory can hardly be distinguished from the
exact solution even for long time. | nucl-th |
$γ^\ast γ\to η, η^\prime$ transition form factors: Using a continuum approach to the hadron bound-state problem, we calculate
$\gamma^\ast \gamma \to \eta, \eta^\prime$ transition form factors on the
entire domain of spacelike momenta, for comparison with existing experiments
and in anticipation of new precision data from next-generation $e^+ e^-$
colliders. One novel feature is a model for the contribution to the
Bethe-Salpeter kernel deriving from the non-Abelian anomaly, an element which
is crucial for any computation of $\eta, \eta^\prime$ properties. The study
also delivers predictions for the amplitudes that describe the light- and
strange-quark distributions within the $\eta, \eta^\prime$. Our results compare
favourably with available data. Important to this at large-$Q^2$ is a sound
understanding of QCD evolution, which has a visible impact on the $\eta^\prime$
in particular. Our analysis also provides some insights into the properties of
$\eta, \eta^\prime$ mesons and associated observable manifestations of the
non-Abelian anomaly. | nucl-th |
A new single-particle basis for nuclear many-body calculations: Predominantly, harmonic oscillator single-particle wave functions are the
choice as a basis in ab-initio nuclear many-body calculations. These
wave-functions, although very convenient in order to evaluate the matrix
elements of the interaction in the laboratory frame, have a too fast fall-off
at large distances. In the past, in alternative to the harmonic oscillator,
other single-particle wave functions have been proposed. In this work we
propose a new single-particle basis, directly linked to the nucleon-nucleon
interaction. This new basis is orthonormal and complete, has the proper
asymptotic behavior at large distances and does not contain the continuum which
would pose severe convergence problems in nuclear many body calculations. We
consider the newly proposed NNLO-opt nucleon-nucleon interaction, without any
renormalization.
We show that unlike other basis, this single-particle representation has a
computational cost similar to the harmonic oscillator basis with the same space
truncation and it gives lower energies for ${}^6He$ and ${}^6Li$. | nucl-th |
O(12) limit and complete classification of symmetry schemes in
proton-neutron interacting boson model: It is shown that the proton-neutron interacting boson model (pnIBM) admits
new symmetry limits with O(12) algebra which break F-spin but preserves the
quantum number M_F. The generators of O(12) are derived and the quantum number
`v' of O(12) for a given boson number N is determined by identifying the
corresponding quasi-spin algebra. The O(12) algebra generates two symmetry
schemes and for both of them, complete classification of the basis states and
typical spectra are given. With the O(12) algebra identified, complete
classification of pnIBM symmetry limits with good M_F is established. | nucl-th |
Growth of Interaction Between Antiprotons (Negative Hyperons) and Nuclei
in Polarized Matter: The Possibility to Study the Spin-Dependent Part of the
Forward Scattering Amplitude in the Range of Low-Energies: The influence of Coulomb interaction on the phenomenon of "optical" spin
rotation of negatively charged particles (antiprotons, etc.) moving in matter
with polarized nuclei is considered. It is shown that because the density of
the antiproton (negative hyperon) wave function on the nucleus increases, the
spin precession frequency grows as the particle decelerates. As a result, spin
rotation of negatively charged particles becomes observable despite their rapid
deceleration. This provides information about the spin--dependent part of the
amplitude of coherent elastic zero--angle scattering in the range of low
energies, where scattering experiments are practically impossible to perform. | nucl-th |
Thermal and transport properties in central heavy-ion reactions around a
few hundred MeV/nucleon: Thermalization process of nuclear matter in central fireball region of
heavy-ion collisions is investigated by employing an extension model of
Boltzmann-Uehling-Uhlenbeck, namely the Van der Waals
Boltzmann-Uehling-Uhlenbeck (VdWBUU) model. Temperature ($T$) is extracted by
the quantum Fermion fluctuation approach and other thermodynamic quantities,
such as density ($\rho$), entropy density ($s$), shear viscosity ($\eta$),
isospin diffusivity ($D_{I}$) and heat conductivity ($\kappa$), are also
deduced. The liquid-like and gas-like phase signs are discussed through the
behavior of shear viscosity during heavy-ion collisions process with the VdWBUU
model. | nucl-th |
Symmetry Energy I: Semi-Infinite Matter: Energy for a nucleus is considered in macroscopic limit, in terms of nucleon
numbers. Further considered for a nuclear system is the Hohenberg-Kohn energy
functional, in terms of proton and neutron densities. Finally,
Skyrme-Hartree-Fock calculations are carried out for a half-infinite
particle-stable nuclear-matter. In each case, the attention is focused on the
role of neutron-proton asymmetry and on the nuclear symmetry energy. We extend
the considerations on the symmetry term from an energy formula to the
respective term in the Hohenberg-Kohn functional. We show, in particular, that
in the limit of an analytic functional, and subject to possible Coulomb
corrections, it is possible to construct isoscalar and isovector densities out
of the proton and neutron densities, that retain a universal relation to each
other, approximately independent of asymmetry. In the so-called local
approximation, the isovector density is inversely proportional to the symmetry
energy in uniform matter at the local isoscalar density. Generalized symmetry
coefficient of a nuclear system is related, in the analytic limit of a
functional, to an integral of the isovector density. We test the relations,
inferred from the Hohenberg-Kohn functional, in the Skyrme-Hartree-Fock
calculations of half-infinite matter. Within the calculations, we obtain
surface symmetry coefficients and parameters characterizing the densities, for
the majority of Skyrme parameterizations proposed in the literature. The
volume-to-surface symmetry-coefficient ratio and the displacement of nuclear
isovector relative to isoscalar surfaces both strongly increase as the slope of
symmetry energy in the vicinity of normal density increases. | nucl-th |
The effect of early chemical freeze out on radial and elliptic flow from
a full 3D hydrodynamic model: We investigate the effect of early chemical freeze-out on radial and elliptic
flow by using a fully three dimensional hydrodynamic model. We find that the
time evolution of temperature and the thermal freeze-out temperature dependence
of average radial flow are different from the results by using a conventional
hydrodynamic model in which chemical equilibrium is always assumed. We also
analyse the p_t spectrum and v_2(p_t) at the RHIC energy and consistently
reproduce experimental data by choosing the thermal freeze-out temperature T_th
= 140 MeV. | nucl-th |
Thermal conductivity in dynamics of first-order phase transition: Effects of thermal conductivity on the dynamics of first-order phase
transitions are studied. Important consequences of a difference of the
isothermal and adiabatic spinodal regions are discussed. We demonstrate that in
hydrodynamical calculations at non-zero thermal conductivity, $\kappa \neq 0$,
onset of the spinodal instability occurs, when the system trajectory crosses
the isothermal spinodal line. Only for $\kappa = 0$ it occurs at a cross of the
adiabatic spinodal line. Therefore ideal hydrodynamics is not suited for an
appropriate description of first-order phase transitions. | nucl-th |
Faddeev-Yakubovsky search for Lambda-Lambda hydrogen-4: Evidence for particle stability of Lambda-Lambda hydrogen-4 (4LLH) has been
suggested by the BNL-AGS E906 experiment. We report on Faddeev-Yakubovsky
calculations for the four-body Lambda-Lambda-p-n system using Lambda-N
interactions which reproduce the observed binding energy of Lambda hydrogen-3
(3LH) within a Faddeev calculation for the Lambda-p-n subsystem. No 4LLH bound
state is found over a wide range of Lambda-Lambda interaction strengths,
although the Faddeev equations for a three-body Lambda-Lambda-d model of 4LLH
admit a 1+ bound state for as weak a Lambda-Lambda interaction strength as
required to reproduce the binding energy of Lambda-Lambda Helium-6 (6LLHe). | nucl-th |
Coupling of pairing and triaxial shape vibrations in collective states
of $γ$-soft nuclei: In addition to shape oscillations, low-energy excitation spectra of deformed
nuclei are also influenced by pairing vibrations. The simultaneous description
of these collective modes and their coupling has been a long-standing problem
in nuclear structure theory. Here we address the problem in terms of
self-consistent mean-field calculations of collective deformation energy
surfaces, and the framework of the interacting boson approximation. In addition
to quadrupole shape vibrations and rotations, the explicit coupling to pairing
vibrations is taken into account by a boson-number non-conserving Hamiltonian,
specified by a choice of a universal density functional and pairing
interaction. An illustrative calculation for $^{128}$Xe and $^{130}$Xe shows
the importance of dynamical pairing degrees of freedom, especially for
structures built on low-energy $0^+$ excited states, in $\gamma$-soft and
triaxial nuclei. | nucl-th |
Elastic and dynamic form factors of an atomic nucleus in the shell model
with correction for the center-of-mass motion: Analytical expressions for the elastic and dynamic form factors (FFs) are
derived in the shell model (SM) with a potential well of finite depth. The
consideration takes into account the motion of the target-nucleus center of
mass (CM). Explanation is suggested for a simultaneous shrinking of the density
and momentum distributions of nucleons in nuclei. The convenient working
formulae are given to handle the expectation values of relevant multiplicative
operators in case of the 1s-1p shell nuclei. | nucl-th |
Nuclear Responses to Electro-Weak Probes and In-Medium Chiral
Perturbation Theory: We discuss two topics concerning the application of chiral perturbation
theory to nuclear physics: (1) the latest developments in the study of possible
kaon condensation in dense baryonic systems; (2) nuclear responses to
electro-weak probes. | nucl-th |
Microscopic predictions for production of neutron rich nuclei in the
reaction $^\mathbf{176}\mathbf{Yb}+{}^\mathbf{176}\mathbf{Yb}$: Background: Production of neutron-rich nuclei is of vital importance to both
understanding nuclear structure far from stability and to informing
astrophysical models of the rapid neutron capture process (r-process).
Multinucleon transfer (MNT) in heavy-ion collisions offers a possibility to
produce neutron-rich nuclei far from stability.
Purpose: The $^{176}\mathrm{Yb}+{}^{176}\mathrm{Yb}$ reaction has been
suggested as a potential candidate to explore the neutron-rich region
surrounding the principal fragments. The current study has been conducted with
the goal of providing guidance for future experiments wishing to study this (or
similar) system.
Methods: Time-dependent Hartree-Fock (TDHF) and its time-dependent
random-phase approximation (TDRPA) extension are used to examine both
scattering and MNT characteristics in $^{176}\mathrm{Yb}+{}^{176}\mathrm{Yb}$.
TDRPA calculations are performed to compute fluctuations and correlations of
the neutron and proton numbers, allowing for estimates of primary fragment
production probabilities.
Results: Both scattering results from TDHF and transfer results from the
TDRPA are presented for different energies, orientations, and impact
parameters. In addition to fragment composition, scattering angles and total
kinetic energies, as well as correlations between these observables are
presented.
Conclusions: $^{176}\mathrm{Yb}+{}^{176}\mathrm{Yb}$ appears to be an
interesting probe for the mid-mass neutron-rich region of the chart of
nuclides. The predictions of both TDHF and TDRPA are speculative, and will
benefit from future experimental results to test the validity of this approach
to studying MNT in heavy, symmetric collisions. | nucl-th |
Transport study of charged current interactions in neutrino-nucleus
reactions: Within a dynamical transport approach we investigate charged current
interactions in neutrino-nucleus reactions for neutrino energies of 0.3 - 1.5
GeV with particular emphasis on resonant pion production channels via the
$\Delta_{33}(1232)$ resonance. The final-state-interactions of the resonance as
well as of the emitted pions are calculated explicitly for $^{12}C$ and
$^{56}Fe$ nuclei and show a dominance of pion suppression at moderate momenta
$p_\pi >$ 0.2 GeV/c. A comparison to integrated $\pi^+$ spectra for $\nu_\mu +
^{12}C$ reactions with the available (preliminary) data demonstrates a
reasonable agreement. | nucl-th |
Odd-Even Staggering of Nuclear Masses: Pairing or Shape Effect?: The odd-even staggering of nuclear masses was recognized in the early days of
nuclear physics. Recently, a similar effect was discovered in other finite
fermion systems, such as ultrasmall metallic grains and metal clusters. It is
believed that the staggering in nuclei and grains is primarily due to pairing
correlations (superconductivity), while in clusters it is caused by the
Jahn-Teller effect. We find that, for light and medium-mass nuclei, the
staggering has two components. The first one originates from pairing while the
second, comparable in magnitude, has its roots in the deformed mean field. | nucl-th |
Towards a new quark-nuclear matter EoS for applications in astrophysics
and heavy-ion collisions: The aim of our work is to develop a unified equation of state (EoS) for
nuclear and quark matter for a wide range in temperature, density and isospin
so that it becomes applicable for heavy-ion collisions as well as for the
astrophysics of neutron stars, their mergers and supernova explosions. As a
first step, we use improved EoS for the hadronic and quark matter phases and
join them via Maxwell construction. We discuss the limitations of a 2-phase
description and outline steps beyond it, towards the formulation of a unified
quark-nuclear matter EoS on a more fundamental level by a cluster virial
expansion. | nucl-th |
A Schematic Model for $ρ$-$a_1$ Mixing at Finite Density and
In-Medium Effective Lagrangian: Based on schematic two-level models extended to $a_1$-meson degrees of
freedom, we investigate possible mechanisms of chiral restoration in the
vector/axialvector channels in cold nuclear matter. In the first part of this
article we employ the massive Yang-Mills framework to construct an effective
chiral Lagrangian based on low-energy mesonic modes at finite density. The
latter are identified through nuclear collective excitations of `meson'-sobar
type such as $\pi\leftrightarrow [\Delta (1232)N^{-1}]\equiv\hat\pi$,
$\rho\leftrightarrow [N^* (1520)N^{-1}]\equiv\hat\rho$, etc.. In a mean-field
type treatment the in-medium gauge coupling $\hat g$, the (axial-) vector meson
masses and $\hat f_\pi$ are found to decrease with density indicating the
approach towards chiral restoration in the language of in-medium effective
fields. In the second part of our analysis we evaluate the (first) in-medium
Weinberg sum rule which relates vector and axialvector correlators to the pion
decay constant. Using in-medium $\rho$/$a_1$ spectral functions (computed in
the two-level model) also leads to a substantial reduction of the pion decay
constant with increasing density. | nucl-th |
Exact solution of equations for proton localization in neutron star
matter: The rigorous treatment of proton localization phenomenon in asymmetric
nuclear matter is presented. The solution of proton wave function and neutron
background distribution is found by the use of the extended Thomas-Fermi
approach. The minimum of energy is obtained in the Wigner- Seitz approximation
of spherically symmetric cell. The analysis of three different nuclear models
suggests that the proton localization is likely to take place in the interior
of neutron star. | nucl-th |
Phenomenological QCD equations of state for neutron star mergers: Thermal QCD equations of state at high baryon density are sensitive to the
phase structure and the resulting excitation modes. The leading contribution at
low temperature can be either ~p_F^2 T^2 (pF: Fermi momentum, T: temperature)
for phases with gapless quarks, or ~T^4 for phases with gapped quarks. In the
latter the thermal pressure is dominated by collective modes. Starting with a
schematic quark model developed for neutron star structure, we estimate the
thermal contributions and zero point energy from the Nambu-Goldstone modes by
building them upon the mean field background for the color-flavor-locked quark
matter. Applying the phase shift representation for thermodynamic potentials,
we include not only the bound state pairs but also resonating pairs. According
to the Levinson's theorem, the high energy contributions tend to cancel the
pole contributions to the thermodynamics, tempering the UV behaviors in the
zero point energy. Our primary target in this talk is the domain with baryon
density nB as large as ~ 5-10n_0 (n_0 = 0.16 fm^{-3}: nuclear saturation
density), and the temperature T of the order ~30-100 MeV. The insights into
this domain may be obtained through the future detection of gravitational waves
from neutron star merging events. | nucl-th |
Transverse mass scaling of dilepton radiation off a quark-gluon plasma: The spectrum of dileptons produced by the quark-gluon plasma in an
ultrarelativistic nucleus-nucleus collision depends only, to a good
approximation, on the transverse mass M_t of the dilepton. This scaling is
exact as long as transverse flow is negligible, and the system is in local
thermal equilibrium. We implement a state-of-the-art modelization of kinetic
and chemical equilibration in the early stages of the evolution to study the
modifications of the spectrum. Violations of M_t scaling resulting from these
effects are evaluated as a function of the shear viscosity to entropy ratio
(eta/s) that controls the equilibration time. We determine the dependence of
the spectrum on system size, centrality, rapidity, and collision energy. We
show that the quark-gluon plasma produces more dileptons than the Drell-Yan
process up to invariant masses of order M = 4 GeV. Due to different kinematics,
for a given M_t , the dependence of the dilepton yield on M is opposite for the
two processes, so that experiment alone can in principle determine which
process dominates. | nucl-th |
An improvement on RPA based on a Boson mapping: We use a solvable model to perform modified dyson mapping and reveal the
unphysical-state effects in the original Random Phase Approximation (RPA). We
then propose a method to introduce the RPA and improve it based on a Boson
mapping. | nucl-th |
Analysis of NN Amplitudes up to 2.5 GeV: An Optical Model and Geometric
Interpretation: We analyse the SM97 partial wave amplitudes for nucleon--nucleon (NN)
scattering to 2.5 GeV, in which resonance and meson production effects are
evident for energies above pion production threshold. Our analyses are based
upon boson exchange or quantum inversion potentials with which the
sub-threshold data are fit perfectly. Above 300 MeV they are extrapolations, to
which complex short ranged Gaussian potentials are added in the spirit of the
optical models of nuclear physics and of diffraction models of high energy
physics. The data to 2.5 GeV are all well fit. The energy dependences of these
Gaussians are very smooth save for precise effects caused by the known $\Delta$
and N$^\star$ resonances. With this approach, we confirm that the geometrical
implications of the profile function found from diffraction scattering are
pertinent in the regime 300 MeV to 2.5 GeV and that the overwhelming part of
meson production comes from the QCD sector of the nucleons when they have a
separation of their centres of 1 to 1.2 fm. This analysis shows that the
elastic NN scattering data above 300 MeV can be understood with a local
potential operator as well as has the data below 300 MeV. | nucl-th |
Gross features of finite nuclei at finite temperatures: A simple expression is obtained for the low temperature behavior of the
energy and entropy of finite nuclei for $20\leq A\leq 250$. The dependence on
$A$ of these quantities is for the most part due to the presence of the
asymmetry energy. | nucl-th |
Isospin-asymmetric nuclear matter: This study uses classical molecular dynamics to simulate infinite nuclear
matter and study the effect of isospin asymmetry on bulk properties such as
energy per nucleon, pressure, saturation density, compressibility and symmetry
energy. The simulations are performed on systems embedded in periodic boundary
conditions with densities and temperatures in the ranges $\rho$=0.02 to 0.2
fm$^{-3}$ and T = 1, 2, 3, 4 and 5 MeV, and with isospin content of
$x=Z/A$=0.3, 0.4 and 0.5. The results indicate that symmetric and asymmetric
matter are self-bound at some temperatures and exhibit phase transitions from a
liquid phase to a liquid-gas mixture. The main effect of isospin asymmetry is
found to be a reduction of the equilibrium densities, a softening of the
compressibility and a disappearance of the liquid-gas phase transition. A
procedure leading to the evaluation of the symmetry energy and its variation
with the temperature was devised, implemented and compared to mean field theory
results. | nucl-th |
An exact solution of spherical mean-field plus orbit-dependent
non-separable pairing model with two non-degenerate j-orbits: An exact solution of nuclear spherical mean-field plus orbit-dependent
non-separable pairing model with two non-degenerate j-orbits is presented. The
extended one-variable Heine-Stieltjes polynomials associated to the Bethe
ansatz equations of the solution are determined, of which the sets of the zeros
give the solution of the model, and can be determined relatively easily. A
comparison of the solution to that of the standard pairing interaction with
constant interaction strength among pairs in any orbit is made. It is shown
that the overlaps of eigenstates of the model with those of the standard
pairing model are always large, especially for the ground and the first excited
state. However, the quantum phase crossover in the non-separable pairing model
cannot be accounted for by the standard pairing interaction. | nucl-th |
Inhomogeneous freeze-out in heavy-ion collisions: Relative hadron abundances from high-energy heavy-ion collisions reveal
substantial inhomogeneities of temperature and baryon-chemical potential within
the decoupling volume. The freeze-out volume is not perfectly "stirred", i.e.
the concentrations of pions, kaons, (anti-) nucleons etc are inhomogeneous.
Such inhomogeneities in the late stages of the hydrodynamic expansion might be
traces of a first-order phase transition. | nucl-th |
Color Decoherence in In-Medium QCD Cascades: The talk, based on \cite{LN10}, analyzes the consequences of the assumption
that the effects of quantum coherence and the resulting angular ordering in QCD
cascades are disrupted within the hot fireball created in ultrarelativistic
heavy ion collisions. | nucl-th |
Relation between the density-matrix theory and the pairing theory: The time-dependent density-matrix theory (TDDM) gives a correlated ground
state as a stationary solution of the time-dependent equations for one-body and
two-body density matrices. The small amplitude limit of TDDM (STDDM) is a
version of extended RPA theories which include the effects of ground state
correlations. It is shown that the solutions of the Hartree-Fock Bogoliubov
theory and the quasi-particle RPA satisfy the TDDM and STDDM equations,
respectively, when only pairing-type correlations are taken into account in
TDDM and STDDM. | nucl-th |
Microcanonical studies on isoscaling: The exponential scaling of isotopic yields is investigated for sources of
different sizes over a broad range of excitation energies and freeze-out
volumes, in both primary and asymptotic stages of the decay in the framework of
a microcanonical multifragmentation model. It was found that the scaling
parameters have a strong dependence on the considered pair of equilibrated
sources and excitation energy and are affected by the secondary particle
emission of the break-up fragments. No significant influence of the freeze-out
volume on the considered isotopic ratios has been observed. Deviations of
microcanonical results from grandcanonical expectations are discussed. | nucl-th |
State-of-the-art of beyond mean field theories with nuclear density
functionals: We present an overview of beyond mean field theories (BMFT) based on the
generator coordinate method (GCM) and the recovery of symmetries used in
nuclear physics with effective forces. After a reminder of the
Hartree-Fock-Bogoliubov (HFB) theory a discussion of the shortcomings of any
mean field approximation (MFA) is presented. The recovery of the symmetries
spontaneously broken in the HFB approach, in particular the angular momentum,
is necessary, among others, to describe excited states and transitions.
Particle number projection is needed to guarantee the right number of protons
and neutrons. Furthermore a projection before the variation prevents the
pairing collapse in the weak pairing regime. The lack of fluctuations around
the average values of the MFA is a shortcoming of this approach. To build in
correlations in BMFT one selects the relevant degrees of freedom: quadrupole,
octupole and the pairing vibrations as well as the single particle ones. In the
GCM the operators representing these degrees of freedom are used as coordinates
to generate a collective subspace. The highly correlated GCM wave function is
finally written as a linear combination of a projected basis of this space. The
variation of the coefficients of the linear combination leads to the
Hill-Wheeler equation. We discuss the classical beta and gamma vibrations by
considering the quadrupole operators as coordinates. We present pairing
fluctuations by considering the pairing gaps as generator coordinates. Lastly
the explicit consideration of the time reversal symmetry breaking in the HFB
wave function by the cranking procedure allows the alignment of nucleon pairs
opening a new dimension in the BMFT calculations. Abundant calculations with
the Gogny force illustrate the state-of-the-art of BMFTs with density
functionals. We conclude with a thorough discussion on the potential poles of
the theory. | nucl-th |
Antisymmetrization in the Multicluster Dynamic Model of Nuclei and the
Nucleon Exchange Effects: A modified version of the Multicluster Dynamic Model of nuclei is proposed to
construct completely antisymmetrized wave functions of multicluster systems. An
overlap kernel operator is introduced to renormalize the total wave function
after antisymmetrization between nucleons in different clusters. A
group-theoretical method is developed to analyze the role of the exchange
effects arising in the calculation of the various observables of multicluster
systems due to this antisymmetrization.
The Antisymmetrized version of the Multicluster Dynamic Model is applied to
the six-nucleon systems treating them as alpha-2N ones.The static and dynamic
characteristics of the six-nucleon systems manifested in electron and pi-meson
scattering, muon capture, beta-decay, pion photoproduction, etc., are
calculated. | nucl-th |
Is Anomalous Production of Omega and anti-Omega Evidence for Disoriented
Chiral Condensates?: No conventional picture of nucleus-nucleus collisions has yet been able to
explain the abundance of Omega and anti-Omega hyperons in central collisions
between Pb nuclei at 158 A GeV at the CERN SPS. We argue that this is evidence
that they are produced as topological defects arising from the formation of
disoriented chiral condensates (DCC) with an average domain size of about 2 fm. | nucl-th |
Dynamical evolution of critical fluctuations and its observation in
heavy ion collisions: We study time evolution of critical fluctuations of conserved charges near
the QCD critical point in the context of relativistic heavy ion collisions. A
stochastic diffusion equation is employed in order to describe the diffusion
property of the critical fluctuation arising from the coupling of the order
parameter field to conserved charges. We show that the diffusion property gives
rise to a possibility of probing the early time fluctuations through the
rapidity window dependence of the second-order cumulant and correlation
function of conserved charges. It is pointed out that their non-monotonic
behaviors as functions of the rapidity interval are robust experimental signals
for the existence of the critical enhancement around the QCD critical point. | nucl-th |
Multiple chiral doublet candidate nucleus $^{105}$Rh in a relativistic
mean-field approach: Following the reports of two pairs of chiral doublet bands observed in
$^{105}$Rh, the adiabatic and configuration-fixed constrained triaxial
relativistic mean-field (RMF) calculations are performed to investigate their
triaxial deformations with the corresponding configuration and the possible
multiple chiral doublet (M$\chi$D) phenomenon. The existence of M$\chi$D
phenomenon in $^{105}$Rh is highly expected. | nucl-th |
Origin of the mass splitting of elliptic anisotropy in a multiphase
transport model: The mass splitting of elliptic anisotropy ($v_2$) at low transverse momentum
is considered as a hallmark of hydrodynamic collective flow. We investigate a
multiphase transport (AMPT) model where the $v_2$ is mainly generated by an
anisotropic escape mechanism, not of the hydrodynamic flow nature, and where
mass splitting is also observed. We demonstrate that the $v_2$ mass splitting
in AMPT is small right after hadronization (especially when resonance decays
are included); the mass splitting mainly comes from hadronic rescatterings,
even though their contribution to the overall charged hadron $v_2$ is small.
These findings are qualitatively the same as those from hybrid models that
combine hydrodynamics with a hadron cascade. We further show that there is no
qualitative difference between heavy ion collisions and small system
collisions. Our results indicate that the $v_2$ mass splitting is not a unique
signature of hydrodynamic collective flow and thus cannot distinguish whether
the elliptic flow is generated mainly from hydrodynamics or the anisotropic
parton escape. | nucl-th |
Separable potential model for $K^{-}N$ interactions at low energies: The effective separable meson-baryon potentials are constructed to match the
equivalent chiral amplitudes up to the second order in external meson momenta.
We fit the model parameters (low energy constants) to the threshold and low
energy $K^{-}p$ data. In the process, the $K^{-}$-proton bound state problem is
solved exactly in the momentum space and the 1s level characteristics of the
kaonic hydrogen are computed simultaneously with the available low energy
$K^{-}p$ cross sections. The model is also used to describe the $\pi \Sigma$
mass spectrum and the energy dependence of the $K^{-}n$ amplitude. | nucl-th |
Pions in magnetic field at finite temperature: Pions in external magnetic field are investigated in the frame of a
Pauli-Villars regularized Nambu--Jona-Lasinio model. The meson propagators in
terms of quark bubbles in Ritus and Schwinger schemes are analytically derived,
and pion masses are numerically calculated in the Ritus scheme. For neutral and
charged pions at finite temperature, there exist respectively one and three
mass jumps at the corresponding Mott transition points, due to the discrete
energy levels of the two constituent quarks in magnetic field. | nucl-th |
Systematic study of proton radioactivity half-lives based on the
relationship between the Skyrme-Hartree-Fock and the macroscopic quantities
of nuclear matter: In the present work, we systematically study the proton radioactivity
half-lives of 33 spherical nuclei based on the relationship between the Skyrme
parameters and the macroscopic quantities of nuclear matter. Using the
two-potential approach with the spherical Skyrme-Hartree-Fock model, the
correlation between proton radioactivity half-life and macroscopic quantities
was analyzed. Moreover, we obtained a new Skyrme parameter set by fitting the
two most weighted macroscopic quantities. Compared with Skyrme parameters MSL0
and the theoretical model of proton radioactivity UDLP, the theoretical proton
radioactivity half-life calculated by the new Skyrme parameter set can better
reproduce the experimental data. | nucl-th |
Fusion dynamics of symmetric systems near barrier energies: The enhancement of the sub-barrier fusion cross sections was explained as the
lowering of the dynamical fusion barriers within the framework of the improved
isospin-dependent quantum molecular dynamics (ImIQMD) model. The numbers of
nucleon transfer in the neck region are appreciably dependent on the incident
energies, but strongly on the reaction systems. A comparison of the neck
dynamics is performed for the symmetric reactions $^{58}$Ni+$^{58}$Ni and
$^{64}$Ni+$^{64}$Ni at energies in the vicinity of the Coulomb barrier. An
increase of the ratios of neutron to proton in the neck region at initial
collision stage is observed and obvious for neutron-rich systems, which can
reduce the interaction potential of two colliding nuclei. The distribution of
the dynamical fusion barriers and the fusion excitation functions are
calculated and compared them with the available experimental data. | nucl-th |
Systematics of semi-microscopic proton-nucleus optical potential at low
energies relevant to nuclear astrophysics: Astrophysical models studying the origin of the p-nuclei require knowledge of
the reaction rates of photodisintegrations and capture reactions. Since
experimental data at astrophysically relevant energies are limited, reaction
rate calculations rely on Hauser-Feshbach (HF) theory predictions. The HF
theory requires nuclear physics input such as masses, level densities,
$\gamma$-ray strength functions and proton-nucleus optical potentials (pOMP).
The scope of this work is to improve a global semi-microscopic pOMP at energies
relevant to the p-process. This is achieved by adjusting the normalization
parameters of the OMP to all available proton-capture cross sections measured
at low energies. By establishing the systematic behaviour of these parameters,
one expects to enhance the predictive power of the pOMP when expanding to mass
regions where no data exists. The HF calculations were obtained using TALYS
code. The normalization parameters for the real and imaginary central
potentials ($\lambda_V$ and $\lambda_W$) were adjusted to fit the proton data
in the energy range where the cross-section are independent of the other
nuclear inputs. Results show that the $\lambda_V$ parameter has a strong mass
dependence that can be described by a second-degree polynomial function for A
$\leq$ 100 and an exponential increase for 100 < A < 162. Though variations of
the $\lambda_W$ have a smaller effect on the calculations, a global increase by
50$\%$ improves the results for certain nuclei without affecting the rest of
the cases. The resulting adjustment functions were obtained by fitting all
suitable proton data and can be used with reasonable confidence to generate the
global semi-microscopic pOMP for nuclei in the medium to heavy mass region. For
better statistics, more low-energy (p,$\gamma$) cross section data are needed
for heavier nuclei with mass A $>$ 100. | nucl-th |
Event-by-event $v_n$ correlations of soft hadrons and heavy mesons in
heavy ion collisions: In this paper heavy quark energy loss models are embedded in full
event-by-event viscous hydrodynamic simulations to investigate the nuclear
suppression factor and azimuthal anisotropy of D$^0$ mesons in PbPb collisions
at 5.02 TeV in the $p_T$ range 8-40 GeV. In our model calculations, the
$R_\text{AA}$ of D$^0$ mesons is consistent with experimental data from the CMS
experiment. We present the first calculations of heavy flavor cumulants
$v_2\{2\}$ and $v_3\{2\}$ (and also discuss $v_2\{4\}$), which is also
consistent with experimental data. Event-shape engineering techniques are used
to compute the event-by-event correlation between the soft hadron $v_n$ and the
heavy meson $v_n$. We predict a linear correlation between these observables on
an event-by-event basis. | nucl-th |
Two-scale scalar mesons in nuclei: We generalize the linear sigma model in order to develop a chiral-invariant
model of nuclear structure. The model is natural, and contains not only the
usual sigma meson which is the chiral partner of the pion but also a new
chiral-singlet that is responsible for the medium-range nucleon-nucleon
attraction. This approach provides significant advantages in terms of its
description of nuclear matter and finite nuclei in comparison with conventional
models based on the linear sigma model. | nucl-th |
Low Energy Theorems For Nucleon-Nucleon Scattering: Low energy theorems are derived for the coefficients of the effective range
expansion in s-wave nucleon-nucleon scattering valid to leading order in an
expansion in which both $m_\pi$ and $1/a$ (where $a$ is the scattering length)
are treated as small mass scales. Comparisons with phase shift data, however,
reveal a pattern of gross violations of the theorems for all coefficients in
both the $^1S_0$ and $^3S_1$ channels. Analogous theorems are developed for the
energy dependence $\epsilon$ parameter which describes $^3S_1 - ^3D_1$ mixing.
These theorems are also violated. These failures strongly suggest that the
physical value of $m_\pi$ is too large for the chiral expansion to be valid in
this context. Comparisons of $m_\pi$ with phenomenological scales known to
arise in the two-nucleon problem support this conjecture. | nucl-th |
Covariant kinetic theory for effective fugacity quasi particle model and
first order transport coefficients for hot QCD matter: An effective relativistic kinetic theory has been constructed for an
interacting system of quarks, anti-quarks and gluons within a quasi-particle
description of hot QCD medium at finite temperature and baryon chemical
potential, where the interactions are encoded in the gluon and quark effective
fugacities with non-trivial energy dispersions. The local conservations of
stress-energy tensor and number current require the introduction of a mean
field term in the transport equation which produces non-vanishing contribution
to the first order transport coefficients. Such contribution has been observed
to be significant for the temperatures which are closer to the QCD transition
tem- perature, however, induces negligible contributions beyond a few times the
transition temperature. As an implication, impact of the mean field
contribution on the the temperature dependence of the shear viscosity, bulk
viscosity and thermal conductivity of a hot QCD medium in the presence of
binary, elastic collisions among the constituents, has been investigated.
Visible effects have been observed for the temperature regime closer to the QCD
transition temperature. | nucl-th |
HFODD (v2.08k): User's Guide: We describe the input data and installation procedures of the code HFODD
(v2.08k). The present write-up contains complete and comprehensive information
that has originally been given in five independent publications. It is enhanced
by the subject index and indexes of variables, input-data keywords,
subroutines, and files that are used in this user guide. | nucl-th |
Pseudo-gauge dependence of quantum fluctuations of energy in a hot
relativistic gas of fermions: Explicit expressions for quantum fluctuations of energy in subsystems of a
hot relativistic gas of spin-$1/2$ particles are derived. The results depend on
the form of the energy-momentum tensor used in the calculations, which is a
feature described as pseudo-gauge dependence. However, for sufficiently large
subsystems the results obtained in different pseudo-gauges converge and agree
with the canonical-ensemble formula known from statistical physics. As
different forms of the energy-momentum tensor of a gas are a priori equivalent,
our finding suggests that the concept of quantum fluctuations of energy in very
small thermodynamic systems is pseudo-gauge dependent. On the practical side,
the results of our calculations determine a scale of coarse graining for which
the choice of the pseudo-gauge becomes irrelevant. | nucl-th |
Quenching of pairing gap at finite temperature in 184W: We extract pairing gap in $^{184}$W at finite temperature for the first time
from the experimental level densities of $^{183}$W, $^{184}$W, and $^{185}$W
using "thermal" odd-even mass difference. We found the quenching of pairing gap
near the critical temperature $T_c = 0.47$ MeV in the BCS calculations. It is
shown that the monopole pairing model with a deformed Woods-Saxon potential
explains the reduction of the pairing correlation using the partition function
with the number parity projection in the static path approximation plus
random-phase approximation. | nucl-th |
New Three-Nucleon-Force Terms in the Three-Nucleon System: We include two new three-nucleon-force terms of pion-range - short-range form
in our momentum-space calculations for the three-nucleon continuum. These two
terms are expected by chiral perturbation theory to be non-negligible. We study
the effects of these terms in elastic neutron-deuteron scattering and pay
special attention to the neutron vector analyzing power $A_y$. | nucl-th |
Kaon effective mass and energy from a novel chiral SU(3)-symmetric
Lagrangian: A new chiral SU(3) Lagrangian is proposed to describe the properties of kaons
and antikaons in the nuclear medium, the ground state of dense matter and the
kaon-nuclear interactions consistently.
The saturation properties of nuclear matter are reproduced as well as the
results of the Dirac-Br\"{u}ckner theory. Our numerical results show that the
kaon effective mass might be changed only moderately in the nuclear medium due
to the highly non-linear density effects. After taking into account the
coupling between the omega meson and the kaon, we obtain similar results for
the effective kaon and antikaon energies as calculated in the
one-boson-exchange model while in our model the parameters of the kaon-nuclear
interactions are constrained by the SU(3) chiral symmetry. | nucl-th |
Low-momentum NN interactions and all-order summation of ring diagrams of
symmetric nuclear matter: We study the equation of state for symmetric nuclear matter using a
ring-diagram approach in which the particle-particle hole-hole ($pphh$) ring
diagrams within a momentum model space of decimation scale $\Lambda$ are summed
to all orders. The calculation is carried out using the renormalized
low-momentum nucleon-nucleon (NN) interaction $V_{low-k}$, which is obtained
from a bare NN potential by integrating out the high-momentum components beyond
$\Lambda$. The bare NN potentials of CD-Bonn, Nijmegen and Idaho have been
employed. The choice of $\Lambda$ and its influence on the single particle
spectrum are discussed. Ring-diagram correlations at intermediate momenta
($k\simeq$ 2 fm$^{-1}$) are found to be particularly important for nuclear
saturation, suggesting the necessity of using a sufficiently large decimation
scale so that the above momentum region is not integrated out. Using
$V_{low-k}$ with $\Lambda \sim 3$ fm$^{-1}$, we perform a ring-diagram
computation with the above potentials, which all yield saturation energies
$E/A$ and Fermi momenta $k_F^{(0)}$ considerably larger than the empirical
values. On the other hand, similar computations with the medium-dependent
Brown-Rho scaled NN potentials give satisfactory results of $E/A \simeq -15$
MeV and $k_F^{(0)}\simeq 1.4$ fm$^{-1}$. The effect of this medium dependence
is well reproduced by an empirical 3-body force of the Skyrme type. | nucl-th |
Evolution of particle density in high-energy pp collisions: We study the evolution of the particle density, dn/d\eta at fixed \eta with
the beam rapidity Y in the framework of string percolation model. Our main
results are: (i) The width of the "plateau" increases proportionally to Y, (ii)
limiting fragmentation is violated, and (iii) the particle density, reduces to
a step function. | nucl-th |
$α$-decay half-lives of superheavy nuclei with $Z=122-125$: For $\alpha$ decay half-life calculations in this work, the Coulomb and
proximity potential model with a new semiempirical formula for diffuseness
parameter developed in previous work [Phys. Rev. C 100, 024601 (2019)] is used.
The present model in this work is compared with the generalized liquid-drop
model (GLDM), universal decay law (UDL), and experimental half-lives in the
region $Z=104-118$. Next, the predicted half-lives of 51 superheavy nuclei
(SHN) with $Z=122-125$ by the present model are compared with those of GLDM,
and UDL. The present model is revealed to be more accurate in reproducing
experimental half-lives compared to GLDM and UDL. Moreover, it is found that
the predictions of the present model and UDL are highly consistent while GLDM
largely deviates from the other two. A study of the competition between
$\alpha$ decay and spontaneous fission (SF) shows that $\alpha$ decay is the
dominant mode. Among the studied SHN with $Z=122-125$, ${}^{295-307}122$ and
${}^{314-320}125$ are identified as potential candidates whose half-lives are
relatively long enough to be experimentally detected in the future through
their $\alpha$-decay chains. The identified candidates are in good agreement
with other recent work. | nucl-th |
Power-law intensity distribution in $γ$-decay cascades -- Nuclear
Structure as a Scale-Free Random Network: By modeling the transition paths of the nuclear $\gamma$-decay cascade using
a scale-free random network, we uncover a universal power-law distribution of
$\gamma$-ray intensity $\rho_I(I) \propto I^{-2}$, with $I$ the $\gamma$-ray
intensity of each transition. This property is consistently observed for all
datasets with a sufficient number of $\gamma$-ray intensity entries in the
National Nuclear Data Center database, regardless of the reaction type or
nuclei involved. In addition, we perform numerical simulations which support
the model's predictions of level population density. | nucl-th |
Superscaling in lepton-nucleus scattering: We suggest that superscaling analyses of few-GeV inclusive electron
scattering from nuclei, both in the quasielastic peak and in the region where
the $\Delta$-excitation dominates, allow one to make reliable predictions for
charge-changing neutrino reactions at energies of a few GeV, relevant for
neutrino oscillation experiments. | nucl-th |
Finite size effect on Dissociation and Diffusion of chiral partners in
Nambu-Jona-Lasinio model: Along with masses of pion and sigma meson modes, their dissociation into
quark medium provide a detail spectral structures of the chiral partners.
Present article has studied a finite size effect on that detail structure of
chiral partners by using the framework of Nambu-Jona-Lasinio model. Through
this dissociation mechanism, their diffusions and conductions are also studied.
The masses, widths, diffusion coefficients, conductivities of chiral partners
are merged at different temperatures in restore phase of chiral symmetry, but
merging points of all are shifted in lower temperature, when one introduce
finite size effect into the picture. The strengths of diffusions and
conductions are also reduced due to finite size consideration. | nucl-th |
Contributions of different neutron pairs in different approaches for
neutrinoless double beta decay: The methods used till now to calculate the neutrinoless double beta decay
matrix elements are: the Quasiparticle Random Phase Approximation (QRPA), the
Shell Model (SM), the angular momentum projected Hartee-Fock-Bogoliubov
approach (HFB) and the Interacting Boson Model (IBM). The different approaches
are compared specifically concerning the the angular momenta and parities of
the neutron pairs, which are changed into two protons by the $0\nu\beta\beta$
decay. The QRPA and SM involve about the same angular momentum and parity
neutron pairs, while the HFB is restricted to $0^{+}, 2^{+}, 4^{+}, ...$, and
IBM to $0^{+}$ and $2^{+}$ nucleon pairs. The differences in the seniority
contributions for the QRPA and the SM are discussed. | nucl-th |
Momentum transport away from a jet in an expanding nuclear medium: We study the transport dynamics of momenta deposited from jets in
ultrarelativistic heavy-ion collisions. Assuming that the high-energy partons
traverse expanding quark-gluon fluids and are subject to lose their energy and
momentum, we simulate dijet asymmetric events by solving relativistic
hydrodynamic equations numerically without linearization in the fully
(3+1)-dimensional coordinate. Mach cones are formed and strongly broadened by
radial flow of the background medium. As a result, the yield of low-$p_{T}$
particles increases at large angles from the jet axis and compensates the dijet
momentum imbalance inside the jet-cone. This provides an intimate link between
the medium excitation by jets and results in dijet asymmetric events observed
by the CMS Collaboration. | nucl-th |
Study of freeze-out dynamics of strange hadrons: We study the chemical freeze-out dynamics of strange particles ($K,\,
\Lambda,\, \Sigma$) from a homogeneous and isotropically expanding hadronic
system of $\pi, K, \rho, N, \Lambda$ and $\Sigma$ with zero net baryon density.
We use the momentum integrated Boltzmann equation and study their evolution
over the bulk hadronic matter, a condition being similar to the one created at
top RHIC and LHC energies. The cross-sections, which are input to the
equations, are taken either from phenomenological models or parameterized by
comparing against experimental data. From this microscopic calculation we find
that these strange particles freeze-out near transition temperature $\approx
T_c$ due to large relaxation time. The continuous cease of the inelastic
processes due to gradual fall in the temperature and decrease in the number
density, thus lead to early freeze out of strange hadrons $K, \Lambda$ and
$\Sigma$ which happens sequentially near $T_c$. However, freeze-out of these
strange species near Tc appears as a sudden and simultaneous process, which is
mostly predicted by thermal model while explaining the yield of identified
particles at RHIC and LHC energies. | nucl-th |
Chiral three-nucleon force and continuum for dripline nuclei and beyond: Three-nucleon force and continuum play important roles in reproducing the
properties of atomic nuclei around driplines. Therefore it is valuable to build
up a theoretical framework where both effects can be taken into account to
solve the nuclear Schr\"odinger equation. To this end, in this letter, we have
expressed the chiral three-nucleon force within the continuum Berggren
representation, so that bound, resonant and continuum states can be treated on
an equal footing in the complex-momentum space. To reduce the model dimension
and computational cost, the three-nucleon force is truncated at the
normal-ordered two-body level and limited in the $sd$-shell model space, with
the residual three-body term being neglected. We choose neutron-rich oxygen
isotopes as the test ground because they have been well studied experimentally,
with the neutron dripline determined. The calculations have been carried out
within the Gamow shell model. The quality of our results in reproducing the
properties of oxygen isotopes around the neutron dripline shows the relevance
of the interplay between three-nucleon force and the coupling to continuum
states. We also analyze the role played by the chiral three-nucleon force, by
dissecting the contributions of the $2\pi$ exchange, $1\pi$ exchange and
contact terms. | nucl-th |
Deformation and cluster structures in $^{12}$C studied with
configuration mixing using Skyrme interactions: We report an investigation of the structure of $^{12}$C nucleus employing a
newly developed configuration-mixing method. In the three-dimensional
coordinate-space representation, we generate a number of Slater determinants
with various correlated structures using the imaginary-time algorithm. We then
diagonalize a many-body Hamiltonian with the Skyrme interaction in the space
spanned by the Slater determinants with parity and angular momentum
projections. Our calculation reasonably describes the ground and excited states
of $^{12}$C nucleus, both for shell-model-like and cluster-like states. The
excitation energies and transition strengths of the ground-state rotational
band are well reproduced. Negative parity excited states, $1_1^-$, $2_1^-$, and
$3_1^-$, are also reasonably described. The second and third $0^+$ states,
$0_2^+$ and $0_3^+$, appear at around 8.8 MeV and 15 MeV, respectively. The
$0_2^+$ state shows a structure consistent with former results of the
\alpha-cluster models, however, the calculated radius of the $0_2^+$ state is
smaller than those calculations. The three-{\alpha} linear-chain configuration
dominates in the $0_3^+$ state. | nucl-th |
GLISSANDO: GLauber Initial-State Simulation AND mOre: GLISSANDO is a Glauber Monte-Carlo generator for early-stages of relativistic
heavy-ion collisions, written in c++ and interfaced to Root. Several models are
implemented: the wounded-nucleon model, the binary collisions model, the mixed
model, and the model with hot-spots. Subtleties of the distribution of nucleon
in the nucleus are discussed. The original geometric distribution of sources in
the transverse plane can be superimposed with a statistical distribution
simulating the dispersion in the generated transverse energy in each individual
collision. The program generates inter alia the fixed axes (standard) and
variable-axes (participant) two-dimensional profiles of the density of sources
in the transverse plane and their Fourier components. These profiles can be
used in further analyses of physical phenomena, such as the the jet quenching,
event-by-event hydrodynamics, or analysis of the elliptic flow and its
fluctuations. Characteristics of the event (multiplicities, eccentricities,
Fourier coefficients, etc.) are evaluated and stored in a file for further
off-line studies. A number of scripts is provided for that purpose. Supplied
variants of the code can also be used for the proton-nucleus and
deuteron-nucleus collisions. | nucl-th |
Effects of triaxiality and pairing interaction on fission barriers of
actinide nuclei studied by density-dependence relativistic mean-field theory: We employ density-dependent relativistic mean-field theory to study how the
triaxiality and pairing interaction affect the inner fission barriers of
actinide nuclei. It was found that triaxiality reduced the inner fission
barriers and improved agreement with experimental values for many actinides.
However, about 1-2 MeV discrepancy to the experimental values still remained
for some of the considered nuclei. Such a discrepancy could be made further
smaller by increasing the BCS pairing strength parameter. In this work, we
demonstrated that adjusting the paring strength was effective to reproduce the
experimental inner fission barriers as well as "pairing rotational energy" and
binding energy in a consistent manner for nuclei where the effect of the
triaxiality on the inner fission barriers was significant. | nucl-th |
Yrast band in the heavy $N = Z$ nucleus $^{88}$Ru: $α$-cluster
approach: The yrast band in the heavy $N = Z$ nucleus $^{88}$Ru is studied in the
framework of the $\alpha$-cluster model in combination with double-folding
potentials. It is found that the excitation energies of the yrast band in
$^{88}$Ru can be nicely described within the $\alpha$-cluster approach using a
smooth and mildly $L$-dependent adjustment of the potential strength. This
result is similar to well-established $\alpha$-cluster states in nuclei with a
(magic core $\otimes$ $\alpha$) structure. Contrary, the yrast bands in
neighboring $N \ne Z$ nuclei deviate from such a typical $\alpha$-cluster
behavior. Finally, the $\alpha$-cluster model predicts reduced transition
strengths of about 10 Weisskopf units for intraband transitions between
low-lying states in the yrast band of $^{88}$Ru. | nucl-th |
Density dependent magnetic field and the equation of state of hyperonic
matter: We are interested on the effects, caused by strong variable density dependent
magnetic fields, on hyperonic matter, its symmetry energy, equations of state
and mass-radius relations. The inclusion of the anomalous magnetic moment of
the particles involved in a stellar system is performed, and some results are
compared with the cases that do not take this correction under consideration.
The Lagrangian density used follows the nonlinear Walecka model plus the
leptons subjected to an external magnetic field. | nucl-th |
Weak Magnetism Correction to Allowed Beta-decay for Reactor Antineutrino
Spectra: The weak magnetism correction and its uncertainty to nuclear beta-decay play
a major role in determining the significance of the reactor neutrino anomaly.
Here we examine the common approximation used for one-body weak magnetism in
the calculation of fission antineutrino spectra, wherein matrix elements of the
orbital angular momentum operator contribution to the magnetic dipole current
are assumed to be proportional to those of the spin operator. Although we find
this approximation invalid for a large set of nuclear structure situations, we
conclude that it is valid for the relevant allowed beta-decays between fission
fragments. In particular, the uncertainty in the fission antineutrino due to
the uncertainty in the one-body weak magnetism correction is found to be less
than 1%. Thus, the dominant uncertainty from weak magnetism for reactor
neutrino fluxes lies in the uncertainty in the two-body meson-exchange magnetic
dipole current. | nucl-th |
Nuclear excitation cross section of $^{229}$Th via inelastic electron
scattering: Nuclear excitation cross section of $^{229}$Th from the ground state to the
low-lying isomeric state via inelastic electron scattering is calculated, on
the level of Dirac distorted wave Born approximation. With electron energies
below 100 eV, inelastic scattering is very efficient in the isomeric
excitation, yielding excitation cross sections on the order of 10$^{-27}$ to
10$^{-26}$ cm$^2$. Systematic analyses are presented on elements affecting the
excitation cross section, including the ion-core potential, the relativistic
effect, the knowledge of the reduced nuclear transition probabilities, etc. | nucl-th |
Neutrino-nucleus interactions in the T2K experiment: We present a study of neutrino-nucleus interactions at the T2K experiment
based on the GiBUU transport model. The aim of T2K is to measure $\nu_e$
appearance and $\theta_{13}$, but it will also be able to do a precise
measurement of $\nu_\mu$ disappearance. The former requires a good
understanding of $\pi^0$ production while the latter is closely connected with
a good understanding of quasielastic scattering. For both processes we
investigate the influence of nuclear effects and particular final-state
interactions on the expected event rates taking into account the T2K detector
setup. | nucl-th |
High temperature phase of QCD: I give a brief overview of our present understanding of the high temperature
phase of QCD, trying to clarify some of the theoretical issues involved in the
current discussions that emphasize the strongly coupled character of the
quark-gluon plasma produced at RHIC. | nucl-th |
Measurement of the energy of the 8.3-eV isomer of 229mTh with
photoelectric effect: It is proposed to use the photoelectric effect in the inner shells of the
229Th atoms to refine the energy of the 8.3-eV isomer. The calculation was
performed using the Feinberg-Migdal shaking theory, which leads to the
probability of isomer formation up to several units of 10^-4 in the case of the
K shell. As a result, two lines are predicted in the photoelectron spectrum,
their separation energy providing the energy of the isomer. Other ways of using
the method to study the properties of the isomer are also discussed: through
shaking during the formation of radioactive beams in storage rings, etc.
Moreover, recording the effect in an experiment will provide the isomer's
partial lifetime. | nucl-th |
Emergence of hydrodynamics in expanding relativistic plasmas: I consider a simple set of equations that govern the expansion of
boost-invariant plasmas of massless particles. These equations describe the
transition from a collisionless regime at early time to hydrodynamics at late
time. Their mathematical structure encompasses all versions of second order
hydrodynamics. We emphasize that the apparent success of Israel-Stewart
hydrodynamics at early time has little to do with ``hydrodynamics'' proper, but
rather with a particular feature of Israel-Stewart equations that allows them
to effectively mimic the collisionless regime. | nucl-th |
Strangeness in nuclear physics: Extensions of nuclear physics to the strange sector are reviewed, covering
data and models of Lambda and other hypernuclei, multi-strange matter, and
anti-kaon bound states and condensation. Past achievements are highlighted,
present unresolved problems discussed, and future directions outlined. | nucl-th |
Observation of the Mott Effect in Heavy Ion Collisions: Possibility of observing the Mott momentum in the distribution of the
deuterons produced in the process $p + n \to d + \gamma$, in the first stage of
a nuclear reaction is presented. The correlation of a hard photon with a
deuteron allows to select those deuterons produced at the beginning of a
reaction. | nucl-th |
Shear viscosity to entropy density ratio of a relativistic Hagedorn
resonance gas: The new state of matter produced at Relativistic Heavy Ion Collider reveals a
strongly coupled quark-gluon plasma with an extremely small shear viscosity to
entropy density ratio eta/s. We calculate the eta/s of an equilibrated hadron
matter characterized by a relativistic hadron resonance gas with a Hagedorn
mass spectrum that grows exponentially with the hadron mass. We find with
increase in temperature of the system the eta/s value decreases due to rapid
increase in the multiplicity of massive resonances. In the vicinity of the
critical temperature for deconfinement transition, the minimum value of eta/s
in the Hagedorn resonance gas is found to be consistent with the current
estimates for a strongly coupled quark-gluon plasma. | nucl-th |
On the dominance of J(P)=0(+) ground states in even-even nuclei from
random two-body interactions: Recent calculations using random two-body interactions showed a preponderance
of J(P)=0(+) ground states, despite the fact that there is no strong pairing
character in the force. We carry out an analysis of a system of identical
particles occupying orbits with j=1/2, 3/2 and 5/2 and discuss some general
features of the spectra derived from random two-body interactions. We show that
for random two-body interactions that are not time-reversal invariant the
dominance of 0(+) states in this case is more pronounced, indicating that
time-reversal invariance cannot be the origin of the 0(+) dominance. | nucl-th |
Multiplicity Fluctuations in Limited Segments of Momentum Space in
Statistical Models: Multiplicity fluctuations in limited segments of momentum space are
calculated for a classical pion gas within the statistical model. Results for
the grand canonical, canonical, and micro-canonical ensemble are obtained,
compared and discussed. We demonstrate that even in the large volume limit
correlations between macroscopic subsystems due to energy and momentum
conservation persist. Based on the micro-canonical formulation we make
qualitative predictions for the rapidity and transverse momentum dependence of
multiplicity fluctuations. The resulting effects are of similar magnitude as
the predicted enhancement due to a phase transition from a quark-gluon plasma
to a hadron gas phase, or due to the critical point of strongly interacting
matter, and qualitatively agree with recently published preliminary
multiplicity fluctuation data of the NA49 SPS experiment. | nucl-th |
Covariant density functional analysis of shape evolution in $N =40$
isotones: The structure of low-lying excitation states of even-even $N=40$ isotones is
studied using a five-dimensional collective Hamiltonian with the collective
parameters determined from the relativistic mean-field plus BCS method with the
PC-PK1 functional in the particle-hole channel and a separable paring force in
the particle-particle channel. The theoretical calculations can reproduce not
only the systematics of the low-lying states along the isotonic chain but also
the detailed structure of the spectroscopy in a single nucleus. We find a
picture of spherical-oblate-prolate shape transition along the isotonic chain
of $N=40$ by analyzing the potential energy surfaces. The coexistence of
low-lying excited $0^+$ states has also been shown to be a common feature in
neutron-deficient $N=40$ isotones. | nucl-th |
Mixed phases during the phase transitions: Quest for a new form of matter inside compact stars compels us to examine the
thermodynamical properties of the phase transitions. We closely consider the
first-order phase transitions and the phase equilibrium on the basis of the
Gibbs conditions, taking the liquid-gas phase transition in asymmetric nuclear
matter as an example. Characteristic features of the mixed phase are figured
out by solving the coupled equations for mean-fields and densities of
constituent particles self-consistently within the Thomas-Fermi approximation.
The mixed phase is inhomogeneous matter composed of two phases in equilibrium;
it takes a crystalline structure with a unit of various geometrical shapes,
inside of which one phase with a characteristic shape, called "pasta", is
embedded in another phase by some volume fraction. This framework enables us to
properly take into account the Coulomb interaction and the interface energy,
and thereby sometimes we see the mechanical instability of the geometric
structures of the mixed phase. Thermal effect on the liquid-gas phase
transition is also elucidated.
Similarly hadron-quark deconfinement transition is studied in hyperonic
matter, where the neutrino-trapping effect as well as the thermal effect is
discussed in relation to the properties of the mixed phase. Specific features
of the mixed phase are elucidated and the equation of state is presented. | nucl-th |
Lattice Gauge Theory - QCD from Quarks to Hadrons: Lattice Gauge Theory enables an ab initio study of the low-energy properties
of Quantum Chromodynamics, the theory of the strong interaction. I begin these
lectures by presenting the lattice formulation of QCD, and then outline the
benchmark calculation of lattice QCD, the light-hadron spectrum. I then proceed
to explore the predictive power of lattice QCD, in particular as it pertains to
hadronic physics. I will discuss the spectrum of glueballs, exotics and excited
states, before investigating the study of form factors and structure functions.
I will conclude by showing how lattice QCD can be used to study multi-hadron
systems, and in particular provide insight into the nucleon-nucleon
interaction. | nucl-th |
Isoscalar-Isovector Interferences in $πN \to N e^+ e^-$ Reactions as
a Probe of Baryon Resonance Dynamics: The isoscalar-isovector ($\rho-\omega$) interferences in the exclusive
reactions $\pi^- p \to n e^+ e^-$ and $\pi^+ n \to p e^+ e^-$ near the $\omega$
threshold leads to a distinct difference of the dielectron invariant mass
distributions depending on beam energy. The strength of this effect is
determined by the coupling of resonances to the nucleon vector-meson channels
and other resonance properties. Therefore, a combined analysis of these
reactions can be used as a tool for determining the baryon resonance dynamics. | nucl-th |
Hadronic matter compressibility from event-by-event analysis of
heavy-ion collisions: We propose a method to measure the hadronic matter compressibility by means
of the event-by-event analysis of heavy-ion collisions at high energies. The
method, which utilizes the thermodynamical relation between the compressibility
and the particle number fluctuations, requires a simultaneous measurement of
the particle source size, temperature and particle multiplicity. | nucl-th |
Modeling Nuclear Properties with Support Vector Machines: We have made initial studies of the potential of support vector machines
(SVM) for providing statistical models of nuclear systematics with demonstrable
predictive power. Using SVM regression and classification procedures, we have
created global models of atomic masses, beta-decay halflives, and ground-state
spins and parities. These models exhibit performance in both data-fitting and
prediction that is comparable to that of the best global models from nuclear
phenomenology and microscopic theory, as well as the best statistical models
based on multilayer feedforward neural networks. | nucl-th |
Impact of level densities and $γ$-strength functions on $r$-process
simulations: Studies attempting to quantify the sensitivity of the $r$-process abundances
to nuclear input have to cope with the fact that the theoretical models they
rely on, rarely come with confidence intervals. This problem has been dealt
with by either estimating these intervals and propagating them statistically to
the final abundances using reaction networks within simplified astrophysical
models, or by running more realistic astrophysical simulations using different
nuclear-physics models consistently for all the involved nuclei. Both of these
approaches have their strengths and weaknesses. In this work, we run
$r$-process calculations for five trajectories using 49 different
neutron-capture rate models. Our results shed light on the importance of taking
into account shell effects and pairing correlations in the network
calculations. | nucl-th |
Quark contribution to the nucleon polarizabilities and three-body forces: We study the response of the nucleon, as a system of three bound
(constituent) non relativistic quarks, to external (quasi static) electric and
magnetic fields. The approach, based on a sum rule technique, is applied to a
large class of two and three-body interquark potentials. Lower and upper bounds
to the electric polarizability and para-magnetic susceptibility are explicitly
calculated within a large variety of constituent models and their values
related to the features of the interquark interaction picture. The r\^ole of
three-body forces is investigated in details as well as the effects of SU(6)
breaking terms in the potential model. Our results can be used to extract the
mesonic contributions to the static polarizabilty and susceptibility. The quark
degrees of freedom give a quite sizeable contributions to both and the meson
cloud accounts roughly for 30% and 60% of the electric proton and neutron
polarizability respectively. The quark contribution to the paramagnetic
susceptibility is even higher and the mesonic effects are rather uncertain. | nucl-th |
Flavor and Charge Symmetry in the Parton Distributions of the Nucleon: Recent calculations of charge symmetry violation(CSV) in the valence quark
distributions of the nucleon have revealed that the dominant symmetry breaking
contribution comes from the mass associated with the spectator quark
system.Assuming that the change in the spectator mass can be treated
perturbatively, we derive a model independent expression for the shift in the
parton distributions of the nucleon. This result is used to derive a relation
between the charge and flavor asymmetric contributions to the valence quark
distributions in the proton, and to calculate CSV contributions to the nucleon
sea. The CSV contribution to the Gottfried sum rule is also estimated, and
found to be small. | nucl-th |
The sound generated by a fast parton in the quark-gluon plasma is a
crescendo: The total energy deposited into the medium per unit length by a fast parton
traversing a quark-gluon plasma is calculated. We take the medium excitation
due to collisions to be given by the well known expression for the collisional
drag force. The parton's radiative energy loss contributes to the energy
deposition because each radiated gluon acts as an additional source of
collisional energy loss in the medium. In our model, this leads to a length
dependence on the differential energy loss due to the interactions of radiated
gluons with the medium. The final result, which is a sum of the primary and the
secondary contributions, is then treated as the coefficient of a local
hydrodynamic source term. Results are presented for energy density wave induced
by two fast, back-to-back partons created in an initial hard interaction. | nucl-th |
Bethe-Salpeter approach with the separable interaction for the deuteron: Recent developments of the covariant Bethe-Salpeter (BS) approach with the
use of the separable interaction for the deuteron are reviewed. It is shown
that the BS formalism allows a covariant description of various electromagnetic
reactions like the lepton-deuteron scattering, deuteron electro-disintegration,
deep inelastic scattering (DIS) of leptons on light nuclei. The procedure of
the construction of the separable nucleon-nucleon (NN) interaction is
discussed. The BS formalism facilitates analysis of the role of the P-waves
(negative energy components) in the electromagnetic properties of the deuteron
and its comparison with the nonrelativistic results. Furthermore the covariant
BS approach makes it possible to analyze DIS of leptons from the deuteron in a
model independent way and to extend the formalism to DIS reactions on the light
nuclei. | nucl-th |
A deformed QRPA formalism for single and two-neutrino double beta decay: We use a deformed QRPA formalism to describe simultaneously the energy
distributions of the single beta Gamow-Teller strength and the two-neutrino
double beta decay matrix elements. Calculations are performed in a series of
double beta decay partners with A = 48, 76, 82, 96, 100, 116, 128, 130, 136 and
150, using deformed Woods-Saxon potentials and deformed Skyrme Hartree-Fock
mean fields. The formalism includes a quasiparticle deformed basis and residual
spin-isospin forces in the particle-hole and particle-particle channels. We
discuss the sensitivity of the parent and daughter Gamow-Teller strength
distributions in single beta decay, as well as the sensitivity of the double
beta decay matrix elements to the deformed mean field and to the residual
interactions. Nuclear deformation is found to be a mechanism of suppression of
the two-neutrino double beta decay. The double beta decay matrix elements are
found to have maximum values for about equal deformations of parent and
daughter nuclei. They decrease rapidly when differences in deformations
increase. We remark the importance of a proper simultaneous description of both
double beta decay and single Gamow-Teller strength distributions. Finally, we
conclude that for further progress in the field it would be useful to improve
and complete the experimental information on the studied Gamow-Teller strengths
and nuclear deformations. | nucl-th |
Triple-Gluon and Triple-Quark Elastic Scatterings and Early
Thermalization: Three-gluon to three-gluon scatterings lead to rapid thermalization of gluon
matter created in central Au-Au collisions at RHIC energies. Thermalization of
quark matter is studied from three-quark to three-quark scatterings. | nucl-th |
Strangeness in the cores of neutron stars: The measurement of the mass 1.97 +/- 0.04 M_sun for PSR J1614-2230 provides a
new constraint on the equation of state and composition of matter at high
densities. In this contribution we investigate the possibility that the dense
cores of neutron stars could contain strange quarks either in a confined state
(hyperonic matter) or in a deconfined one (strange quark matter) while
fulfilling a set of constraints including the new maximum mass constraint. We
account for the possible appearance of hyperons within an extended version of
the density-dependent relativistic mean-field model, including the phi-meson
interaction channel. Deconfined quark matter is described by the color
superconducting three-flavor NJL model. | nucl-th |
Manifestly-covariant chiral PT calculation of nucleon Compton scattering: We compute the Compton scattering off the nucleons in the framework of
manifestly covariant baryon chiral perturbation theory (B$\chi$PT). The results
for observables differ substantially from the corresponding calculations in
heavy-baryon chiral perturbation theory (HB$\chi$PT), most appreciably in the
forward kinematics. We verify that the covariant $p^3$ result fulfills the
forward-Compton-scattering sum rules. We also explore the effect of the
$\Delta$(1232) resonance at order $p^4/\varDelta$, with $\varDelta\approx 300$
MeV, the resonance excitation energy. We find that the substantial effect of
the $\Delta$-excitation on the nucleon polarizabilities can naturally be
accommodated in the manifestly covariant calculation. | nucl-th |
Induced pseudoscalar form factor of the nucleon at two-loop order in
chiral perturbation theory: We calculate the imaginary part of the induced pseudoscalar form factor of
the nucleon $G_P(t)$ in the framework of two-loop heavy baryon chiral
perturbation theory. The effect of the calculated three-pion continuum on the
pseudoscalar constant $g_P = (m_\mu/2M) G_P(t=-0.877m_\mu^2)$ measurable in
ordinary muon capture $\mu^-p\to \nu_\mu n$ turns out to be negligibly small.
Possible contributions from counterterms at two-loop order are numerically
smaller than the uncertainty of the dominant pion-pole term proportional to the
pion-nucleon coupling constant $g_{\pi N}= 13.2\pm 0.2$. We conclude that a
sufficiently accurate representation of the induced pseudoscalar form factor of
the nucleon at low momentum transfers $t$ is given by the sum of the pion-pole
term and the Adler-Dothan-Wolfenstein term: $G_P(t) = 4g_{\pi N} M f_\pi/
(m_\pi^2 -t)- 2g_A M^2 < r_A^2 >/3$, with $<r_A^2> = (0.44 \pm 0.02)$ fm$^2$
the axial mean square radius of the nucleon. | nucl-th |
Microscopic calculation of the wobbling excitations by using the
Woods-Saxon potential as a nuclear mean-field: The wobbling excitations of the triaxial superdeformed (TSD) bands in the Lu
and Hf region are studied by the microscopic framework of the cranked
mean-field and the random-phase approximation (RPA). In contrast to the
previous works, where the Nilsson potential was used, the more realistic
Woods-Saxon potential is employed as a nuclear mean-field. The wobbling-like
RPA solutions have been found systematically in the nuclei studied and their
characteristic properties are investigated in details. This confirms the
wobbling phonon excitations in TSD nuclei from the microscopic calculations.
The result of $B(E2)$ values indicates that the triaxial deformation is
increasing as a function of spin in the observed TSD bands in $^{163}$Lu. | nucl-th |
Search for Quasi Bound $η$ Mesons: The search for a quasi bound $\eta$ meson in atomic nuclei is reviewed. This
tentative state is studied theoretically as well as experimentally. The theory
starts from elastic $\eta$ nucleon scattering which is derived from production
data within some models. From this interaction the $\eta$ nucleus interaction
is derived. Model calculations predict binding energies and widths of the quasi
bound state. Another method is to derive the $\eta$ nucleus interaction from
excitation functions of $\eta$ production experiments. The $s$ wave interaction
is extracted from such data via final state interaction theorem. We give the
derivation of $s$ wave amplitudes in partial wave expansion and in helicity
amplitudes and their relation to observables. Different experiments extracting
the final state interaction are discussed as are production experiments. So far
only three experiments give evidence for the existence of the quasi bound
state: a pion double charge exchange experiment, an effective mass measurement,
and a transfer reaction at recoil free kinematics with observation of the decay
of the state. | nucl-th |
Bulk properties of nuclear matter in the relativistic Hartree
approximation with cut-off regularization: A method of cut-off regularization is proposed to evaluate vacuum corrections
in nuclear matter in the framework of the Hartree approximation. Bulk
properties of nuclear matter calculated by this method are a good agreement
with results analyzed by empirical values. The vacuum effect is quantitatively
evaluated through a cut-off parameter and its role for saturation property and
compressional properties is clarified. | nucl-th |
Spherical to deformed shape transition in the nucleon-pair shell model: A study of the shape transition from spherical to axially deformed nuclei in
the even Ce isotopes using the nucleon-pair approximation of the shell model is
reported. As long as the structure of the dominant collective pairs is
determined using a microscopic framework appropriate to deformed nuclei, the
model is able to produce a shape transition. However, the resulting transition
is too rapid, with nuclei that should be transitional being fairly well
deformed, perhaps reflecting the need to maintain several pairs with each
angular momentum. | nucl-th |
An analytic hydrodynamical model of rotating 3D expansion in heavy-ion
collisions: A new exact and analytic solution of non-relativistic fireball hydrodynamics
is presented. It describes an expanding triaxial ellipsoid that rotates around
one of its principal axes. The observables are calculated using simple analytic
formulas. Azimuthal oscillation of the off-diagonal Bertsch-Pratt radii of
Bose-Einstein correlations as well as rapidity dependent directed and third
flow measurements provide means to determine the magnitude of the rotation of
the fireball. Observing this rotation and its dependence on collision energy
may lead to new information on the equation of state of the strongly
interacting quark gluon plasma produced in high energy heavy ion collisions. | nucl-th |
Possible bound nuclei beyond the two-neutron drip line in the
$50\leqslant Z \leqslant 70$ region: Possible bound nuclei beyond the two-neutron drip line in the $50\leqslant Z
\leqslant 70$ region are investigated by using the deformed relativistic
Hartree-Bogoliubov theory in continuum with density functional PC-PK1. Bound
nuclei beyond the drip lines of $_{56}$Ba, $_{58}$Ce, $_{62}$Sm, $_{64}$Gd and
$_{66}$Dy are predicted, forming peninsulas of stability in nuclear landscape.
Near these peninsulas, several multi-neutron emitters are predicted. The
underlying mechanism of the peninsulas of stability is investigated by studying
the total energy, Fermi surface, quadrupole deformation and the single-neutron
spectrum in the canonical basis. It is found that the deformation effect is
crucial for forming the peninsulas of stability, and pairing correlations are
also essential in specific cases. The dependence on the deformation evolution
is also discussed. The decay rates of multi-neutron radioactivity in Ba and Sm
isotopic chains are estimated by using the direct decay model. | nucl-th |
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