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Effect of short- and long-range correlations on neutron skins of various
neutron-rich doubly magic nuclei: We study the effects of correlations beyond the independent particle model in
the evaluation of neutron skins of various neutron-rich doubly magic nuclei. We
consider short- and long-range correlations to take into account the presence
of the strongly repulsive core of the bare nucleon-nucleon interaction and
collective nuclear phenomena, respectively. Despite the strong sensitivity on
the structure of the nucleus considered, our results indicate that, in general,
correlations increase the values of the neutron skins. | nucl-th |
Parametric estimate of the relative photon yields from the Glasma and
the Quark-Gluon Plasma in heavy-ion collisions: Recent classical-statistical numerical simulations have established the
"bottom-up" thermalization scenario of Baier et al. as the correct weak
coupling effective theory for thermalization in ultrarelativistic heavy-ion
collisions. We perform a parametric study of photon production in the various
stages of this bottom-up framework to ascertain the relative contribution of
the off-equilibrium "Glasma" relative to that of a thermalized Quark-Gluon
Plasma. Taking into account the constraints imposed by the measured charged
hadron multiplicities at RHIC and the LHC, we find that Glasma contributions
are important especially for large values of the saturation scale at both
energies. These non-equilibrium effects should therefore be taken into account
in studies where weak coupling methods are employed to compute photon yields. | nucl-th |
Observable Properties of Quark-Hadron Phase Transition at the Large
Hadron Collider: Quark-hadron phase transition is simulated by an event generator that
incorporates the dynamical properties of contraction due to QCD confinement
forces and randomization due to the thermal behavior of a large quark system on
the edge of hadronization. Fluctuations of emitted pions in the $(\eta,\phi)$
space are analyzed using normalized factorial moments in a wide range of bin
sizes. The scaling index $\nu$ is found to be very close to the predicted value
in the Ginzburg-Landau formalism. The erraticity indices $\mu_q$ are determined
in a number of ways that lead to the same consistent values. They are compared
to the values from the Ising model, showing significant difference in a
transparent plot. Experimental determination of $\nu$ and $\mu_q$ at the LHC
are now needed to check the reality of the theoretical study and to provide
guidance for improving the model description of quark-hadron phase transition. | nucl-th |
Low-lying States of $^{6}$He and $^{6}$Be in Nodal Surface Structure
Analysis: The low-lying states of light nuclei $^6$He and $^6$Be are studied. Using the
inherent nodal surface(INS) analysis approach, we deduce the quantum numbers
and the spatial symmetries of the low-lying states with positive parity and
negative parity of the two nuclei. The energy spectrum obtained agrees well
with the experimental data. | nucl-th |
Alpha Decay in the Complex Energy Shell Model: Alpha emission from a nucleus is a fundamental decay process in which the
alpha particle formed inside the nucleus tunnels out through the potential
barrier. We describe alpha decay of $^{212}$Po and $^{104}$Te by means of the
configuration interaction approach. To compute the preformation factor and
penetrability, we use the complex-energy shell model with a separable T=1
interaction. The single-particle space is expanded in a Woods-Saxon basis that
consists of bound and unbound resonant states. Special attention is paid to the
treatment of the norm kernel appearing in the definition of the formation
amplitude that guarantees the normalization of the channel function. Without
explicitly considering the alpha-cluster component in the wave function of the
parent nucleus, we reproduce the experimental alpha-decay width of $^{212}$Po
and predict an upper limit of T_{1/2}=5.5x10^{-7} sec for the half-life of
$^{104}$Te. The complex-energy shell model in a large valence configuration
space is capable of providing a microscopic description of the alpha decay of
heavy nuclei having two valence protons and two valence neutrons outside the
doubly magic core. The inclusion of proton-neutron interaction between the
valence nucleons is likely to shorten the predicted half-live of $^{104}$Te. | nucl-th |
Effects of the equation of state on the bulk properties of
maximally-rotating neutron stars: Neutron stars are among the densest known objects in the universe and an
ideal laboratory for the strange physics of super-condensed matter. While the
simultaneously measurements of mass and radius of non-rotating neutron stars
may impose constraints on the properties of the dense nuclear matter, the
observation and study of maximally-rotating ones, close to the mass-shedding
limit, may lead to significantly further constraints. Theoretical predictions
allow neutron stars to rotate extremely fast (even more than $2000 \ {\rm
Hz}$). However, until this moment, the fastest observed rotating pulsar has a
frequency of $716 \ {\rm Hz}$, much lower compared to the theoretical
predictions. There are many suggestions for the mechanism which lead to this
situation. In any case, the theoretical study of uniformly rotating neutron
stars, along with the accurate measurements, may offer rich information
concerning the high density part of the equation of state. In addition, neutron
stars through their evolution, may provide us with a criteria to determine the
final fate of a rotating compact star. Sensitivity of bulk neutron stars
properties on the equation of state at the mass-shedding limit are the main
subject of the present study. | nucl-th |
Anisotropic flow in Cu+Au collisions at $\sqrt{s_{NN}}=200$ GeV: The anisotropic flow of charged hadrons in asymmetric Cu+Au collisions at the
Relativistic Heavy Ion Collider is studied in a multi-phase transport model.
Compared with previous results for symmetric Au+Au collisions, charged hadrons
produced around midrapidity in asymmetric collisions are found to have a
stronger directed flow $v_{1}$ and their elliptic flow $% v_{2} $ is also more
sensitive to the parton scattering cross section. While higher-order flows
$v_{3}$ and $v_{4}$ are small at all rapidities, both $% v_{1}$ and $v_{2}$ in
these collisions are appreciable and show an asymmetry in forward and backward
rapidities. | nucl-th |
Nuclear viscosity estimated by dynamics of neck formation in the early
stage of nuclear collision: The very early stage of the coalescence of two nuclei is studied and used to
estimate the nuclear viscosity. The time evolution of the neck region has been
simulated by the unified Langevin equation method, which is used in the
analysis of heavy-ion collisions from the approaching stage to the
fusion-fission stage. It is found that the transition from viscous to inertial
coalescence that appeared in the neck growth of macroscopic drops can also be
seen in the present simulation in nucleus-nucleus collisions. The dynamics of
neck growth is analyzed in terms of the hydrodynamical formula and the
viscosity coefficient of nuclear matter is estimated using the analogy of
macroscopic drops. | nucl-th |
Hans Bethe: The Nuclear Many Body Problem: We discuss the work of Hans Bethe and others in formulating a theoretical
foundation for the nuclear shell model. Written for a general audience, this
article describes the evolution from Brueckner's reaction matrix theory to the
Moszkowski-Scott separation method and ultimately to the Reference Spectrum
method of Bethe, Brandow, and Petschek. We also discuss connections with the
recently developed low momentum nucleon-nucleon interactions. | nucl-th |
Center-of-mass effects on the quasi-hole spectroscopic factors in the
16O(e,e'p) reaction: The spectroscopic factors for the low-lying quasi-hole states observed in the
16O(e,e'p)15N reaction are reinvestigated with a variational Monte Carlo
calculation for the structure of the initial and final nucleus. A computational
error in a previous report is rectified. It is shown that a proper treatment of
center-of-mass motion does not lead to a reduction of the spectroscopic factor
for $p$-shell quasi-hole states, but rather to a 7% enhancement. This is in
agreement with analytical results obtained in the harmonic oscillator model.
The center-of-mass effect worsens the discrepancy between present theoretical
models and the experimentally observed single-particle strength. We discuss the
present status of this problem, including some other mechanisms that may be
relevant in this respect. | nucl-th |
Microscopic Structure of High-Spin Vibrational Excitations in
Superdeformed 190,192,194Hg: Microscopic RPA calculations based on the cranked shell model are performed
to investigate the quadrupole and octupole correlations for excited
superdeformed bands in 190Hg, 192Hg, and 194Hg. The K=2 octupole vibrations are
predicted to be the lowest excitation modes at zero rotational frequency. At
finite frequency, however, the interplay between rotation and vibrations
produces different effects depending on neutron number: The lowest octupole
phonon is rotationally aligned in 190Hg, is crossed by the aligned
two-quasiparticle bands in 192Hg, and retains the K=2 octupole vibrational
character up to the highest frequency in 194Hg. The gamma vibrations are
predicted to be higher in energy and less collective than the octupole
vibrations. From a comparison with the experimental dynamic moments of inertia,
a new interpretation of the observed excited bands invoking the K=2 octupole
vibrations is proposed, which suggests those octupole vibrations may be
prevalent in SD Hg nuclei. | nucl-th |
What can we learn from global spin alignment of $φ$ meson in
heavy-ion collisions?: We propose that a significant positive deviation from 1/3 for the spin
density matrix element $\rho_{00}$ of the $\phi$ meson may indicate the
existence of a mean field of the $\phi$ meson generated in heavy-ion
collisions. This explains why STAR preliminary data for the $\phi$ meson's
$\rho_{00}$ are much larger than 1/3 while the data of $\Lambda$ and
$\bar{\Lambda}$ polarization seem not to allow such a significant and positive
deviation. The contribution may be from the polarization of the strange quark
and antiquark through the $\phi$ field, an effective mode of the gluon field in
strong interaction. We show that $\rho_{00}$ for the $\phi$ meson is a good
analyzer for fields even if they may strongly fluctuate in space-time. | nucl-th |
The Collective Excitation Spectra of $σ, ω$ and $π$ Mesons
in Nuclear Matter: The recent progress on the study of the collective excitation in relativistic
nuclear matter is reviewed. The collective excitation modes are derived by
meson propagators in nuclear matter. The mesons we study are $\sigma, \omega,
\gamma$ and $\pi$ mesons. For pion, we derived not only the relativistic
particle - hole, delta - hole excitations but also antiparticle excitations,
such as particle - antiparticle, antidelta - particle, delta - antiparticle
excitations. By calculating the dispersion relation and the spin - isospin
dependent response function, the effects of all these excitation are studied. | nucl-th |
Continuum random-phase approximation for gamma transition between
excited states in neutron-rich nuclei: A characteristic feature of collective and particle-hole excitations in
neutron-rich nuclei is that many of them couple to unbound neutron in continuum
single-particle orbits. The continuum random phase approximation (cRPA) is a
powerful many-body method that describes such excitations, and it provides a
scheme to evaluate transition strengths from the ground state. In an attempt to
apply cRPA to the radiative neutron capture reaction, we formulate in the
present study an extended scheme of cRPA that describes gamma-transitions from
the excited states under consideration, which decay to low-lying excited states
as well as the ground state. This is achieved by introducing a non-local
one-body operator which causes transitions to a low-lying excited state, and
describing a density-matrix response against this operator. As a demonstration
of this new scheme, we perform numerical calculation for dipole, quadrupole,
and octupole excitations in $^{140}$Sn, and discuss E1 and E2 transitions
decaying to low-lying $2^{+}_{1,2}$ and $3^{-}_{1}$ states. The results point
to cases where the branching ratio to the low-lying states is larger than or
comparable with that to the ground state. We discuss key roles of collectivity
and continuum orbits in both initial and final states. | nucl-th |
Uncertainties in the eta-Nucleon Scattering Length and Effective Range: The coupled eta-N, pi-N, gamma-N system is described by a K-matrix method.
The parameters in this model are adjusted to get an optimal fit to pi-N --->pi-
N$, pi-N --->eta-N$, gamma-N--->pi-N and gamma-N --->eta-N data in an energy
range of about 100MeV or so each side of the eta threshold. The outcome is the
appearance of two solutions one which has an eta-nucleon scattering length (a)
of about 1.0 fm and a second with a~0.2fm. However, the second solution has an
unconventional non-Lorentian form for the T-matrix in the region of the
1535(20)MeV and 1650(30)MeV S-wave pi-N resonances. | nucl-th |
Quark-hadron duality and the nuclear EMC effect: Recent data on polarized proton knockout reactions off He-4 nuclei suggest a
small but nonzero modification of proton electromagnetic form factors in
medium. Using model independent relations derived on the basis of quark-hadron
duality, we relate the medium modification of the form factors to the
modification at large x of the deep-inelastic structure function of a bound
proton. This places strong constraints on models of the nuclear EMC effect
which assume a large deformation of the intrinsic structure of the nucleon in
medium. | nucl-th |
Conservation laws in the $1f_{7/2}$ shell model of $^{48}$Cr: Conservation laws in the $1f_{7/2}$ shell model of $^{48}$Cr found in numeric
studies by Escuderos, Zamick and Bayman [A. Escuderos, L. Zamick, and B. F.
Bayman, arXiv:0506050 (2005)] and me [K. Neerg\aa rd, Phys. Rev. C \textbf{90},
014318 (2014)] are explained by symmetry under particle-hole conjugation and
the structure of the irreps of the symplectic group Sp(4). A generalization is
discussed. | nucl-th |
Uncertainty-quantified phenomenological optical potentials for
single-nucleon scattering: Optical-model potentials (OMPs) continue to play a key role in nuclear
reaction calculations. However, the uncertainty of phenomenological OMPs in
widespread use -- inherent to any parametric model trained on data -- has not
been fully characterized, and its impact on downstream users of OMPs remains
unclear. Here we assign well-calibrated uncertainties for two representative
global OMPs, those of Koning-Delaroche and Chapel Hill '89, using Markov-Chain
Monte Carlo for parameter inference. By comparing the canonical versions of
these OMPs against the experimental data originally used to constrain them, we
show how a lack of outlier rejection and a systematic underestimation of
experimental uncertainties contributes to bias of, and overconfidence in,
best-fit parameter values. Our updated, uncertainty-quantified versions of
these OMPs address these issues and yield complete covariance information for
potential parameters. Scattering predictions generated from our ensembles show
improved performance both against the original training corpora of experimental
data and against a new "test" corpus comprising many of the experimental
single-nucleon scattering data collected over the last twenty years. Finally,
we apply our uncertainty-quantified OMPs to two case studies of
application-relevant cross sections. We conclude that, for many common
applications of OMPs, including OMP uncertainty should become standard
practice. To facilitate their immediate use, digital versions of our updated
OMPs and related tools for forward uncertainty propagation are included as
Supplementary Material. | nucl-th |
Shape/Phase Transitions and Critical Point Symmetries in Atomic Nuclei: Shape/phase transitions in atomic nuclei have first been discovered in the
framework of the Interacting Boson Approximation (IBA) model. Critical point
symmetries appropriate for nuclei at the transition points have been introduced
as special solutions of the Bohr Hamiltonian, stirring the introduction of
additional new solutions describing wide ranges of nuclei. A short review of
these recent developments will be attempted. | nucl-th |
Rescattering of Vector Meson Daughters in High Energy Heavy Ion
Collisions: We consider the role of hadronic rescattering of daughter kaons on the
observed mass spectra from $\phi$ meson decays in ultra-relativistic heavy ion
collisions. A hadronic cascade code (RQMD v2.4) shows that $\sim$26% of all
$\phi$'s decaying to $K^+K^-$ in central Pb+Pb collisions at SPS energies
($E_{beam} = 158 GeV/A$) have a rescattered or absorbed daughter. This
significantly affects the reconstructed invariant mass of the pair and shifts
$\phi$ mesons out of the mass peak. Kaon rescattering depletes the low velocity
region, hardening and broadening the observed phi $m_t$ and rapidity
distributions respectively, relative to the dilepton channel. This effect
produces an apparent change in the experimentally determined branching ratio
not necessarily related to chiral symmetry restoration. Comparisons to recent
experimental measures at CERN energies reveal a possible mechanism to account
for the shape of the observed spectra, though not their absolute relative
magnitude. | nucl-th |
Causal dissipative hydrodynamics obtained from the
nonextensive/dissipative correspondence: We derive the constitutive equations of causal relativistic dissipative
hydrodynamics ($d$-hydrodynamics) from perfect nonextensive hydrodynamics
($q$-hydrodynamics) using the nonextensive/dissipative correspondence (NexDC)
proposed by us recently. The $q$-hydrodynamics can be thus regarded as a
possible model for the $d$-hydrodynamics facilitating its application to high
energy multiparticle production processes. As an example we have shown that
applying the NexDC to the perfect 1+1 $q$-hydrodynamics, one obtains a proper
time evolution of the bulk pressure and the Reynolds number. | nucl-th |
K anti-K N molecule state with I=1/2 and J^P=1/2^+ studied with
three-body calculation: A K \bar{K} N system with I=1/2 and J^P=1/2^+ is investigated with
non-relativistic three-body calculations by using effective \bar K N, K \bar K
and KN interactions. The \bar K N interaction describes the Lambda(1405) as a
\bar K N molecule, and the K\bar K interaction is adjusted to give f_0(980) and
a_0(980) states as K \bar K molecules. The present investigation suggests that
a bound K \bar K N state can be formed below the K \bar K N threshold (1930
MeV) with a 90 ~ 100 MeV width of three-hadron decays, which are dominated by K
bar K N -> K pi Sigma and pi eta N. It is found that the K \bar K N state is a
weakly bound hadron molecular state with a size larger than an alpha particle
because of the repulsive KN interactions. | nucl-th |
Hydrodynamics at RHIC -- how well does it work, where and how does it
break down?: I review the successes and limitations of the ideal fluid dynamic model in
describing hadron emission spectra from Au+Au collisions at the Relativistic
Heavy Ion Collider (RHIC). | nucl-th |
Inverse-Reynolds-Dominance approach to transient fluid dynamics: We consider the evolution equations for the bulk viscous pressure, diffusion
current and shear tensor derived within second-order relativistic dissipative
hydrodynamics from kinetic theory. By matching the higher order moments
directly to the dissipative quantities, all terms which are of second order in
the Knudsen number Kn vanish, leaving only terms of order
$\mathcal{O}(\textrm{Re}^{-1} \textrm{Kn})$ and $\mathcal{O}(\textrm{Re}^{-2})$
in the relaxation equations, where $\textrm{Re}^{-1}$ is the inverse Reynolds
number. We therefore refer to this scheme as the Inverse-Reynolds-Dominance
(IReD) approach. The remaining (non-vanishing) transport coefficients can be
obtained exclusively in terms of the inverse of the collision matrix. This
procedure fixes unambiguously the relaxation times of the dissipative
quantities, which are no longer related to the eigenvalues of the inverse of
the collision matrix. In particular, we find that the relaxation times
corresponding to higher-order moments grow as their order increases, thereby
contradicting the \textit{separation of scales} paradigm. The formal (up to
second order) equivalence with the standard DNMR approach is proven and the
connection between the IReD transport coefficients and the usual DNMR ones is
established. | nucl-th |
An implementation of nuclear time-dependent density-functional theory
and its application to the nuclear isovector electric dipole resonance: Following a previous paper [Y. Shi, Phys. Rev. C 98, 014329(2018)], we
present an extension of the density-functional theory to allow for dynamic
calculations based on the obtained static Hartree-Fock results. We perform
extensive benchmark calculations, by comparing the calculated results with that
of an existing code Sky3D. To perform linear-response calculations using the
TDDFT method, comparisons have been made with the finite-amplitude
quasiparticle random-phase approximation (FAM-QRPA) method. We plan to apply
the TDDFT method to a systematic description of the IVD resonances in the Zr,
Mo, and Ru isotopes.
The strengths of IVD resonances are calculated using two complementary
methods: TDDFT and FAM-QRPA methods. For the TDDFT results, additional
benchmark calculations have been performed using the well-tested code Sky3D. In
these three models, the important ingredients which have major influence on the
results, such as time-odd potentials, boundary conditions, smoothing
procedures, spurious peaks etc., have been carefully examined.
The current TDDFT and the Sky3D codes yield almost identical response
functions once both codes use the same time-odd mean fields and absorbing
boundary conditions. The strengths of the IVD resonances calculated using the
TDDFT and FAM-QRPA methods agree reasonably well with the same position of the
giant dipole resonance. Upon seeing a reasonable accuracy offered by the
implemented code, we perform systematic TDDFT calculations for spherical Zr and
Mo isotopes near $N=50$, where experimental data exist. For neutron-rich Zr,
Mo, and Ru isotopes where shape evolution exist we predict the photoabsorption
cross sections based on oblate and triaxial minima. | nucl-th |
Stability of the $β$-equilibrated dense matter and core-crust
transition in neutron stars: The stability of the $\beta$-equilibrated dense nuclear matter is analyzed
with respect to the thermodynamic stability conditions. Based on the density
dependent M3Y effective nucleon-nucleon interaction, the effects of the nuclear
incompressibility on the proton fraction in neutron stars and the location of
the inner edge of their crusts and core-crust transition density and pressure
are investigated. The high-density behavior of symmetric and asymmetric nuclear
matter satisfies the constraints from the observed flow data of heavy-ion
collisions. The neutron star properties studied using $\beta$-equilibrated
neutron star matter obtained from this effective interaction for a pure
hadronic model agree with the recent observations of the massive compact stars.
The density, pressure and proton fraction at the inner edge separating the
liquid core from the solid crust of neutron stars are determined to be
$\rho_t=$ 0.0938 fm$^{-3}$, P$_t=$ 0.5006 MeV fm$^{-3}$ and x$_{p(t)}=$ 0.0308,
respectively. | nucl-th |
Comment on piNN Coupling from High Precision np Charge Exchange at 162
MeV: In this updated and expanded version of our delayed Comment we show that the
np backward cross section, as presented by the Uppsala group, is seriously
flawed (more than 25 sd.). The main reason is the incorrect normalization of
the data. We show also that their extrapolation method, used to determine the
charged piNN coupling constant, is a factor of about 10 less accurate than
claimed by Ericson et al. The large extrapolation error makes the determination
of the coupling constant by the Uppsala group totally uninteresting. | nucl-th |
The Proton-Deuteron Break-Up Process in a Three-Dimensional Approach: The pd break-up amplitude in the Faddeev scheme is calculated by employing a
three-dimensional method without partial wave decomposition (PWD). In a first
step and in view of higher energies only the leading term is evaluated and this
for the process d(p,n)pp. A comparison with the results based on PWD reveals
discrepancies in the cross section around 200 MeV. This indicates the onset of
a limitation of the partial wave scheme. Also, around 200 MeV relativistic
effects are clearly visible and the use of relativistic kinematics shifts the
cross section peak to where the experimental peak is located. The theoretical
peak height, however, is wrong and calls first of all for the inclusion of
rescattering terms, which are shown to be important in a nonrelativistic full
Faddeev calculation in PWD. | nucl-th |
$δ$ meson effects on neutron stars in the modified quark-meson
coupling model: The properties of neutron stars are investigated by including $\delta$ meson
field in the Lagrangian density of modified quark-meson coupling model. The
$\Sigma^-$ population with $\delta$ meson is larger than that without $\delta$
meson at the beginning, but it becomes smaller than that without $\delta$ meson
as the appearance of $\Xi^-$. The $\delta$ meson has opposite effects on
hadronic matter with or without hyperons: it softens the EOSes of hadronic
matter with hyperons, while it stiffens the EOSes of pure nucleonic matter.
Furthermore, the leptons and the hyperons have the similar influence on
$\delta$ meson effects. The $\delta$ meson increases the maximum masses of
neutron stars. The influence of $(\sigma^*,\phi)$ on the $\delta$ meson effects
are also investigated. | nucl-th |
Renormalization of nuclear chiral effective field theory with
non-perturbative leading order interactions: We extend the renormalizability study of the formulation of chiral effective
field theory with a finite cutoff, applied to nucleon-nucleon scattering, by
taking into account non-perturbative effects. We consider the nucleon-nucleon
interaction up to next-to-leading order in the chiral expansion. The
leading-order interaction is treated non-perturbatively. In contrast to the
previously considered case when the leading-order interaction was assumed to be
perturbative, new features related to the renormalization of the effective
field theory are revealed. In particular, more severe constraints on the
leading-order potential are formulated, which can enforce the renormalizability
and the correct power counting for the next-to-leading order amplitude. To
illustrate our theoretical findings, several partial waves in the
nucleon-nucleon scattering, $^3P_0$, $^3S_1-{^3D_1}$ and $^1S_0$ are analyzed
numerically. The cutoff dependence and the convergence of the chiral expansion
for those channels are discussed. | nucl-th |
Momentum Distribution in Nuclear Matter and Finite Nuclei: A simple method is presented to evaluate the effects of short-range
correlations on the momentum distribution of nucleons in nuclear matter within
the framework of the Green's function approach. The method provides a very
efficient representation of the single-particle Green's function for a
correlated system. The reliability of this method is established by comparing
its results to those obtained in more elaborate calculations. The sensitivity
of the momentum distribution on the nucleon-nucleon interaction and the nuclear
density is studied. The momentum distributions of nucleons in finite nuclei are
derived from those in nuclear matter using a local-density approximation. These
results are compared to those obtained directly for light nuclei like $^{16}O$. | nucl-th |
Enlarged deformation region in neutron-rich Zr isotopes by the second
intruder orbit: Nuclear deformations and density profiles of neutron-rich even-even Zr
isotopes are investigated using the Skyrme-Hartree-Fock-Bogoliubov method.
Large quadrupole and hexadecapole deformations are predicted along with large
enhancement of the total reaction cross sections at the neutron number
$N=60$-74. Strong nuclear deformation starting at $N=60$ is induced by the
occupation of the intruder orbit with the asymptotic quantum number
$[nn_z\Lambda]\Omega$ = [550]1/2 originating from the spherical $0h_{11/2}$
orbit. The deformation region is further enlarged from $N=72$ to 74 owing to
the occupation of the next intruder orbit with [530]1/2 originating from the
spherical $1f_{7/2}$ orbit. This characteristic nuclear deformation is
crucially reflected in the systematic behavior of the nuclear radii and the
density profiles near the nuclear surface. | nucl-th |
Neutral baryonic systems with strangeness: We review the status as regards the existence of three- and four-body bound
states made of neutrons and $\Lambda$ hyperons. For interesting cases, the
coupling to neutral baryonic systems made of charged particles of different
strangeness has been addressed. There are strong arguments showing that the
$\Lambda nn$ system has no bound states. $\Lambda\Lambda nn$ strong stable
states are not favored by our current knowledge of the strangeness $-1$ and
$-2$ baryon-baryon interactions. However, a possible $\Xi^- t$ quasibound state
decaying to $\Lambda\Lambda nn$ might exist in nature. Similarly, there is a
broad agreement about the nonexistence of $\Lambda\Lambda n$ bound states.
However, the coupling to $\Xi NN$ states opens the door to a resonance above
the $\Lambda\Lambda n$ threshold. | nucl-th |
Search for time-reversal-invariance violation in double polarized
antiproton-deuteron scattering: Apart from the $pd$ reaction also the scattering of antiprotons with
transversal polarization $p_y^p$ on deuterons with tensor polarization $P_{xz}$
provides a null-test signal for time-reversal-invariance violating but parity
conserving effects. Assuming that the time-reversal-invariance violating $\bar
NN$ interaction contains the same operator structure as the $NN$ interaction,
we discuss the energy dependence of the null-test signal in $\bar pd$
scattering on the basis of a calculation within the spin-dependent Glauber
theory at beam energies of 50-300 MeV. | nucl-th |
Probing halo nucleus structure through intermediate energy elastic
scattering: This work addresses the question of precisely what features of few body
models of halo nuclei are probed by elastic scattering on protons at high
centre-of-mass energies. Our treatment is based on a multiple scattering
expansion of the proton-projectile transition amplitude in a form which is well
adapted to the weakly bound cluster picture of halo nuclei. In the specific
case of $^{11}$Li scattering from protons at 800 MeV/u we show that because
core recoil effects are significant, scattering crosssections can not, in
general, be deduced from knowledge of the total matter density alone.
We advocate that the optical potential concept for the scattering of halo
nuclei on protons should be avoided and that the multiple scattering series for
the full transition amplitude should be used instead. | nucl-th |
$α$-Particle Spectrum in the Reaction p+$^{11}$B$\to α+
^8Be^*\to 3α$: Using a simple phenomenological parametrization of the reaction amplitude we
calculated $\alpha$-particle spectrum in the reaction p+$^{11}$B$\to \alpha +
^8Be^*\to 3\alpha$ at the resonance proton energy 675 KeV. The parametrization
includes Breit-Wigner factor with an energy dependent width for intermediate
$^8Be^*$ state and the Coulomb and the centrifugal factors in $\alpha$-particle
emission vertexes. The shape of the spectrum consists of a well defined peak
corresponding to emission of the primary $\alpha$ and a flat shoulder going
down to very low energy. We found that below 1.5 MeV there are 17.5% of
$\alpha$'s and below 1 MeV there are 11% of them. | nucl-th |
A new scheme for heavy nuclei: proxy-SU(3): The SU(3) symmetry realized by J. P. Elliott in the sd nuclear shell is
destroyed in heavier shells by the strong spin-orbit interaction. However, the
SU(3) symmetry has been used for the description of heavy nuclei in terms of
bosons in the framework of the Interacting Boson Approximation, as well as in
terms of fermions using the pseudo-SU(3) approximation. We introduce a new
fermionic approximation, called the proxy-SU(3), and we discuss how some of its
novel predictions come out as a consequence of the short range of the
nucleon-nucleon interaction and the Pauli principle. | nucl-th |
Verification of Models for Calculation of E1 Radiative Strength: Photoabsorption cross sections and gamma-decay strength function are
calculated and compared with experimental data to test the existing models of
dipole radiative strength functions (RSF) for the middle-weight and heavy
atomic nuclei. Simplified version of the modified Lorentzian model are
proposed. New tables of giant dipole resonance (GDR) parameters are given. It
is shown that the phenomenological closed-form models with asymmetric shape can
be used for overall estimates of the dipole RSF in the gamma -ray energy region
up to about 20 MeV when GDR parameters are known or the GDR systematics can be
adopted. Otherwise, the HFB-QRPA microscopic model and the semi-classical
approach with moving surface appear to be more adequate methods to estimate the
dipole photoabsorption RSF. | nucl-th |
Is perturbative study of ground-state correlations valid?: Perturbative approaches have often been used to include the effects of
ground-state correlations in extended theories of the random-phase
approximation. Validity of such approaches is investigated for a solvable model
where comparison with exact solutions can be made. It is pointed out that there
is a case where perturbative approaches give good results in spite of the fact
that interaction strength is far beyond a perturbative region. | nucl-th |
Particle-number projection method in time-dependent Hartree-Fock theory:
Properties of reaction products: Background: The time-dependent Hartree-Fock (TDHF) theory has been successful
in describing low-energy heavy ion collisions. Recently, we have shown that
multinucleon transfer processes can be reasonably described in the TDHF theory
combined with the particle-number projection technique. Purpose: In this work,
we propose a theoretical framework to analyze properties of reaction products
in TDHF calculations. Methods: TDHF calculation in three-dimensional Cartesian
grid representation combined with particle number projection method. Results:
We develop a theoretical framework to calculate expectation values of operators
in the TDHF wave function after collision with the particle-number projection.
To show how our method works in practice, the method is applied to
$^{24}$O+$^{16}$O collisions for two quantities, angular momentum and
excitation energy. The analyses revealed following features of the reaction:
The nucleon removal proceeds gently, leaving small values of angular momentum
and excitation energy in nucleon removed nuclei. Contrarily, nuclei receiving
nucleons show expectation values of angular momentum and excitation energy
which increase as the incident energy increases. Conclusions: We have developed
a formalism to analyze properties of fragment nuclei in the TDHF theory
combined with the particle-number projection technique. The method will be
useful for microscopic investigations of reaction mechanisms in low-energy
heavy ion collisions as well as for evaluating effects of particle evaporation
on multinucleon transfer cross sections. | nucl-th |
Faddeev-type calculation of eta-d threshold scattering: The scattering length for the eta-meson collision with deuteron is calculated
on the basis of rigorous few-body equations (AGS) for various eta-N input. The
results obtained strongly support the existence of a resonance or quasi-bound
state close to the eta-d threshold. | nucl-th |
The $πρ$ Cloud Contribution to the $ω$ Width in Nuclear Matter: The width of the $\omega$ meson in cold nuclear matter is computed in a
hadronic many-body approach, focusing on a detailed treatment of the medium
modifications of intermediate $\pi\rho$ states. The $\pi$ and $\rho$
propagators are dressed by their selfenergies in nuclear matter taken from
previously constrained many-body calculations. The pion selfenergy includes
$Nh$ and $\Delta h$ excitations with short-range correlations, while the $\rho$
selfenergy incorporates the same dressing of its $2\pi$ cloud with a full
3-momentum dependence and vertex corrections, as well as direct resonance-hole
excitations; both contributions were quantitatively fit to total
photo-absorption spectra and $\pi N\to\rho N$ scattering. Our calculations
account for in-medium decays of type $\omega N\to \pi N^{(*)}, \pi\pi
N(\Delta)$, and 2-body absorptions $\omega NN\to NN^{(*)},\pi NN$. This causes
deviations of the in-medium $\omega$ width from a linear behavior in density,
with important contributions from spacelike $\rho$ propagators. The $\omega$
width from the $\rho\pi$ cloud may reach up to 200 MeV at normal nuclear matter
density, with a moderate 3-momentum dependence. This largely resolves the
discrepancy of linear $T$-$\varrho$ approximations with the values deduced from
nuclear photoproduction measurements. | nucl-th |
In-medium $Λ$ isospin impurity from charge symmetry breaking in
the ${_Λ^4}{\rm H}-{_Λ^4}{\rm He}$ mirror hypernuclei: The $\Lambda$ separation energies in the mirror hypernuclei
${_{\Lambda}^4}{\rm H}-{_{\Lambda}^4}{\rm He}$ exhibit large charge symmetry
breaking (CSB). Analyzing this CSB within pionless effective field theory while
using partially conserved baryon-baryon SU(3) flavor symmetry, we deduce a
$\Lambda -\Sigma^0$ induced in-medium admixture amplitude ${\cal
A}_{I=1}\approx 1.5\%$ in the dominantly isospin $I=0$ $\Lambda$ hyperon. Our
results confirm the free-space value ${\cal A}^{(0)}_{I=1}$ inferred directly
within the SU(3) baryon octet by Dalitz and von-Hippel in 1964 and reaffirmed
in a recent QCD+QED lattice calculation. Furthermore, exploring the
consequences of SU(3) flavor symmetry on the $\Lambda$-nucleon interaction, we
find that CSB is expected to impact the $S=1$ and $S=0$ spin channels in
opposite directions, with the latter dominating by an order of magnitude. These
observations explain a recent deduction of $\Lambda$-nucleon CSB strengths. | nucl-th |
Charge Form Factor and Cluster Structure of $^6$Li Nucleus: The charge form factor of ${}^6$Li nucleus is considered on the basis of its
cluster structure. The charge density of ${}^6$Li is presented as a
superposition of two terms. One of them is a folded density and the second one
is a sum of ${}^4$He and the deuteron densities. Using the available
experimental data for ${}^4$He and deuteron charge form factors, a good
agreement of the calculations within the suggested scheme is obtained with the
experimental data for the charge form factor of ${}^6$Li, including those in
the region of large transferred momenta. | nucl-th |
Threshold $π^0$ photoproduction in relativistic chiral perturbation
theory: We present a calculation of $\pi^0$ photoproduction on the proton in
manifestly Lorentz-invariant baryon chiral perturbation theory up to and
including chiral order $q^4$. With the results we analyze the latest $\pi^0$
photoproduction data in the threshold region obtained at the Mainz Microtron.
In the calculation of observables and the fit of the low-energy constants, we
take $S$, $P$, and $D$ waves into account. We compare the results for the
multipoles with the corresponding single-energy analysis. Furthermore, we also
fit the $O(q^4)$ heavy-baryon chiral perturbation theory calculation and
compare both results. We provide predictions for several polarization
observables for future experiments. Finally, we discuss the $\beta$ parameter
of the unitarity cusp which is related to the breaking of isospin symmetry. | nucl-th |
Shape of atomic nuclei in heavy ion collisions: In the hydrodynamic model description of heavy ion collisions, the
final-state anisotropic flow $v_n$ are linearly related to the strength of the
multi-pole shape of the distribution of nucleons in the transverse plane
$\varepsilon_n$, $v_n\propto \varepsilon_n$. The $\varepsilon_n$, for
$n=1,2,3,4$, are sensitive to the shape of the colliding ions, characterized by
the quadrupole $\beta_2$, octupole $\beta_3$ and hexadecapole $\beta_4$
deformations. This sensitivity is investigated analytically and also in a Monte
Carlo Glauber model. One observes a robust linear relation,
$\langle\varepsilon_n^2\rangle = a_n'+b_n'\beta_n^2$, for events in a fixed
centrality. The $\langle\varepsilon_1^2\rangle$ has a contribution from
$\beta_3$ and $\beta_4$, and $\langle\varepsilon_3^2\rangle$ from $\beta_4$. In
the ultra-central collisions, there are little cross contributions between
$\beta_2$ and $\varepsilon_3$ and between $\beta_3$ and $\varepsilon_2$, but
clear cross contributions are present in non-central collisions. Additionally,
$\langle\varepsilon_n^2\rangle$ are insensitive to non-axial shape parameters
such as the triaxiality. This is good news because the measurements of $v_2$,
$v_3$ and $v_4$ can be used to constrain simultaneously the $\beta_2$,
$\beta_3$, and $\beta_4$ values. This is best done by comparing two colliding
ions with similar mass numbers and therefore nearly identical $a_n'$, to obtain
simple equation that relates the $\beta_n$ of the two species. This opens up
the possibility to map the shape of the atomic nuclei at a timescale
($<10^{-24}$s) much shorter than probed by low-energy nuclear structure physics
($<10^{-21}$s), which ultimately may provide information complementary to those
obtained in the nuclear structure experiments. | nucl-th |
Initializing BSQ with Open-Source ICCING: While it is well known that there is a significant amount of conserved
charges in the initial state of nuclear collisions, the production of these due
to gluon splitting has yet to be thoroughly investigated. The ICCING (Initial
Conserved Charges in Nuclear Geometry) algorithm reconstructs these quark
distributions, providing conserved strange, baryon, and electric charges, by
sampling a given model for the $g \rightarrow q\bar{q}$ splitting function over
the initial energy density, which is valid at top collider energies, even when
$\mu_B=0$. The ICCING algorithm includes fluctuations in the gluon longitudinal
momenta, a structure that supports the implementation of dynamical processes,
and the c++ version is now open-source. A full analysis of parameter choices on
the model has been done to quantify the effect these have on the underlying
physics. We find there is a sustained difference across the different charges
that indicates sensitivity to hot spot geometry. | nucl-th |
Diffuseness parameter as a bottleneck for accurate half-life
calculations: An investigation of the calculated $\alpha$ decay half-lives of super heavy
nuclei (SHN) reveals that the diffuseness parameter is a great bottleneck for
achieving accurate results and predictions. In particular, when universal
proximity function is adopted for nuclear potential, half-life is found to vary
significantly and nonlinearly as a function of diffuseness parameter. To
overcome this limiting hurdle, a new semiempirical formula for diffuseness that
is dependent on charge and neutron numbers is proposed in this work. With the
model at hand, half-lives of 218 SHN are computed, for 68 of which there exists
available experimental data and 150 of which are predicted. The calculations of
half-lives for 68 SHN are compared against experimental data and the calculated
data obtained by using deformed Woods-Saxon, deformed Coulomb potentials model,
and six semiempirical formulas. The predictions of 150 SHN are compared against
the predictions of seven of the current best semiempirical formulas.
Calculations of the present study are in good agreement with the experimental
half-lives outperforming all but ImSahu semiempirical formula. Moreover, the
predictions of our model are consistent with predictions of the semiempirical
formulas. We strongly conclude that more attention should be directed toward
obtaining accurate diffuseness parameter values for using it in nuclear
calculations. | nucl-th |
Properties of nuclear pastas: In this Review we study the nuclear pastas as they are expected to be formed
in neutron star cores. We start with a study of the pastas formed in nuclear
matter (composed of protons and neutrons), we follow with the role of the
electron gas on the formation of pastas, and we then investigate the pastas in
neutron star matter (nuclear matter embedded in an electron gas). | nucl-th |
Direct capture in the $^{130}$Sn(n,$γ$)$^{131}$Sn and
$^{132}$Sn(n,$γ$)$^{133}$Sn reactions under $r$-process conditions: The cross sections of the $^{130}$Sn(n,$\gamma$)$^{131}$Sn and
$^{132}$Sn(n,$\gamma$)$^{133}$Sn reactions are calculated in the direct capture
model at low energies below 1.5\,MeV. Using recent data from (d,p) transfer
experiments on $^{130}$Sn and $^{132}$Sn, it is possible to avoid global input
parameters with their inherent uncertainties and to determine all input to the
direct capture model by local adjustments. The calculated direct capture cross
sections of $^{130}$Sn and $^{132}$Sn are almost identical and have
uncertainties of less than a factor of two. The stellar reaction rates $N_A <
\sigma v >$ show a slight increase with temperature. Finally an estimate for
the influence of low-lying resonances to the stellar reaction rates is given. | nucl-th |
Neutrino-nucleus reactions on ^{12}C and ^{16}O: Exclusive and inclusive $(\nu_\mu, \mu^-), (\nu_e, e^-)$ cross-sections and
$\mu^-$-capture rates are calculated for ^{12}C and ^{16}O using the consistent
random phase approximation (RPA) and pairing model. After a pairing correction
is introduced to the RPA results the flux-averaged theoretical $(\nu_\mu,
\mu^-), (\nu_e, e^-)$ cross-sections and $\mu^-$-capture rates in $^{12}$C are
in good agreement with experiment. In particular when one takes into account
the experimental error bars, the recently measured range of values for the
$(\nu_\mu, \mu^-)$ cross-section is in agreement with the present theoretical
results. Predictions of $(\nu_\mu, \mu^-)$ and $(\nu_e, e^-)$ cross-sections in
^{16}O are also presented. | nucl-th |
Rescaling of Nuclear Structure Functions: It is shown that nucleonic structure functions are $x-$ and $Q^{2}-$rescaled
in nuclei. The $x-$rescaling accounts for nuclear effects in the case of exact
scaling, while the $Q^{2}-$rescaling is responsible for a corresponding
modification of quantum corrections. This result is obtained in the leading
order for all flavour combinations and connects the two known models for the
EMC-effect. Electroproduction and gluonic nuclear structure functions are
calculated. | nucl-th |
On the complexion of pseudoscalar mesons: A strongly momentum-dependent dressed-quark mass function is basic to QCD. It
is central to the appearance of a constituent-quark mass-scale and an
existential prerequisite for Goldstone modes. Dyson-Schwinger equation (DSEs)
studies have long emphasised this importance, and have proved that QCD's
Goldstone modes are the only pseudoscalar mesons to possess a nonzero leptonic
decay constant in the chiral limit when chiral symmetry is dynamically broken,
while the decay constants of their radial excitations vanish. Such features are
readily illustrated using a rainbow-ladder truncation of the DSEs. In this
connection we find (in GeV): f_{eta_c(1S)}= 0.233, m_{eta_c(2S)}=3.42; and
support for interpreting eta(1295), eta(1470) as the first radial excitations
of eta(548), eta'(958), respectively, and K(1460) as the first radial
excitation of the kaon. Moreover, such radial excitations have electromagnetic
diameters greater than 2fm. This exceeds the spatial length of lattices used
typically in contemporary lattice-QCD. | nucl-th |
Limits on the neutrino mass from neutrinoless double-$β$ decay: Neutrinoless double-$\beta$ decay is of fundamental importance for the
determining neutrino mass. By combining a calculation of nuclear matrix
elements within the framework of the microscopic interacting boson model
(IBM-2) with an improved calculation of phase space factors, we set limits on
the average light neutrino mass and on the average inverse heavy neutrino mass
(flavor violating parameter). | nucl-th |
Applications of the chiral potential with the semi-local regularization
in momentum space to the disintegration processes: We apply the chiral potential with the momentum space semi-local
regularization to the $^2$H and $^3$He photodisintegration processes and to the
(anti)neutrino induced deuteron breakup reactions. Specifically, the
differential cross section, the photon analyzing power and the final proton
polarization have been calculated for the deuteron photodisintegration at the
photon energies 30 MeV and 100 MeV. For the $^3$He photodisintegration
predictions for the semi-inclusive and exclusive differential cross sections
are presented for the photon energies up to 120 MeV. The total cross section is
calculated for the (anti)neutrino disintegrations of the deuteron for the
(anti)neutrino energies below 200 MeV. The predictions based on the Argonne V18
potential or on the older chiral force with regularization applied in
coordinate space are used for comparison. Using the fifth order chiral
nucleon-nucleon potential supplemented with dominant contributions from the
sixth order allows us to obtain converged predictions for the regarded
reactions and observables. Our results based on the newest semi-local chiral
potentials show even smaller cutoff dependence for the considered electroweak
observables than the previously reported ones with a coordinate-space
regulator. However, some of the studied polarization observables in the
deuteron photodisintegration process reveal more sensitivity to the regulator
value than the unpolarized cross section. The chiral potential regularized
semi-locally in momentum space yields also fast convergence of results with the
chiral order. These features make the used potential a high quality tool to
study electroweak processes. | nucl-th |
Momentum-space treatment of Coulomb interaction in three-nucleon
reactions with two protons: The Coulomb interaction between the two protons is included in the
calculation of proton-deuteron elastic scattering, radiative proton-deuteron
capture and two-body electromagnetic disintegration of ${}^3\mathrm{He}$. The
hadron dynamics is based on the purely nucleonic charge-dependent (CD) Bonn
potential and its realistic extension CD Bonn + $\Delta$ to a coupled-channel
two-baryon potential, allowing for single virtual $\Delta$-isobar excitation.
Calculations are done using integral equations in momentum space. The screening
and renormalization approach is employed for including the Coulomb interaction.
Convergence of the procedure is found already at moderate screening radii. The
reliability of the method is demonstrated. The Coulomb effect on observables is
seen at low energies for the whole kinematic regime. In proton-deuteron elastic
scattering at higher energies the Coulomb effect is confined to forward
scattering angles; the $\Delta$-isobar effect found previously remains
unchanged by Coulomb. In electromagnetic reactions Coulomb competes with other
effects in a complicated way. | nucl-th |
Ab initio computation of the longitudinal response function in $^{40}$Ca: We present a consistent \emph{ab initio} computation of the longitudinal
response function $R_L$ in $^{40}$Ca using the coupled-cluster and Lorentz
integral transform methods starting from chiral nucleon-nucleon and
three-nucleon interactions. We validate our approach by comparing our results
for $R_L$ in $^4$He and the Coulomb sum rule in $^{40}$Ca against experimental
data and other calculations. For $R_L$ in $^{40}$Ca we obtain a very good
agreement with experiment in the quasi-elastic peak up to intermediate momentum
transfers, and we find that final state interactions are essential for an
accurate description of the data. This work presents a milestone towards
\emph{ab initio} computations of neutrino-nucleus cross sections relevant for
experimental long-baseline neutrino programs. | nucl-th |
Partial Dynamical SU(3) Symmetry and the Nature of the Lowest K=0
Collective Excitation in Deformed Nuclei: We discuss the implications of partial dynamical SU(3) symmetry (PDS) for the
structure of the lowest K=0^{+} (K=0_2) collective excitation in deformed
nuclei. We consider an interacting boson model Hamiltonian whose ground and
gamma bands have good SU(3) symmetry while the K=0_2 band is mixed. It is shown
that the double-phonon components in the K=0_2 wave function arise from SU(3)
admixtures which, in turn, can be determined from absolute E2 rates connecting
the K=0_2 and ground bands. An explicit expression is derived for these
admixtures in terms of the ratio of K=0_2 and gamma bandhead energies. The
SU(3) PDS predictions are compared with existing data and with broken-SU(3)
calculations for ^{168}Er. | nucl-th |
Improved Kelson-Garvey mass relations for proton-rich nuclei: The improved Kelson-Garvey (ImKG) mass relations are proposed from the mass
differences of mirror nuclei. The masses of 31 measured proton-rich nuclei with
$7\leq A\leq41$ and $-5\leq (N-Z)\leq-3$ can be remarkably well reproduced by
using the proposed relations, with a root-mean-square deviation of 0.398 MeV,
which is much smaller than the results of Kelson-Garvey (0.502 MeV) and
Isobar-Mirror mass relations (0.647 MeV). This is because many more masses of
participating nuclei are involved in the ImKG mass relations for predicting the
masses of unknown proton-rich nuclei. The masses for 144 unknown proton-rich
nuclei with $6\leq A\leq74$ are predicted by using the ImKG mass relations. The
one- and two-proton separation energies for these proton-rich nuclei and the
diproton emission are investigated simultaneously. | nucl-th |
Derivation of breakup probabilities from experimental elastic
backscattering data: We suggest simple and useful method to extract breakup probabilities from the
experimental elastic backscattering probabilities in the reactions with toughly
and weakly bound nuclei. | nucl-th |
Microscopic Optical Potentials for Helium-6 Scattering off Protons: The differential cross section and the analyzing power are calculated for
elastic scattering of $^6$He from a proton target using a microscopic folding
optical potential, in which the $^6$He nucleus is described in terms of a
$^4$He-core with two additional neutrons in the valence p-shell. In contrast to
previous work of that nature, all contributions from the interaction of the
valence neutrons with the target protons are taken into account. | nucl-th |
Global superscaling analysis of quasielastic electron scattering with
relativistic effective mass: We present a global analysis of the inclusive quasielastic electron
scattering data with a superscaling approach with relativistic effective mass.
The SuSAM* model exploits the approximation of factorization of the scaling
function $f^*(\psi^*)$ out of the cross section under quasifree conditions. Our
approach is based on the relativistic mean field theory of nuclear matter where
a relativistic effective mass for the nucleon encodes the dynamics of nucleons
moving in presence of scalar and vector potentials. Both the scaling variable
$\psi^*$ and the single nucleon cross sections include the effective mass as a
parameter to be fitted to the data alongside the Fermi momentum $k_F$. Several
methods to extract the scaling function and its uncertainty from the data are
proposed and compared. The model predictions for the quasielastic cross section
and the theoretical error bands are presented and discussed for nuclei along
the periodic table from $A=2$ to $A=238$: $^2$H, $^3$H, $^3$He, $^4$He,
$^{12}$C, $^{6}$Li, $^{9}$Be, $^{24}$Mg, $^{59}$Ni,
$^{89}$Y, $^{119}$Sn, $^{181}$Ta, $^{186}$W, $^{197}$Au, $^{16}$O, $^{27}$Al,
$^{40}$Ca, $^{48}$Ca, $^{56}$Fe, $^{208}$Pb, and $^{238}$U.
We find that more than 9000 of the total $\sim 20000$ data fall within the
quasielastic theoretical bands. Predictions for $^{48}$Ti and $^{40}$Ar are
also provided for the kinematics of interest to neutrino experiments. | nucl-th |
A ferro-deformation at the open quantum system with protons, Z = 8,
neutrons, N = 20: 28O: We offer a possibility that the nuclear system with protons, Z = 8 has a
large deformation at neutrons, N = 20; 28O that is beyond the neutron drip
line. According to our previous works [arXiv: 1604.05013, 1604.02786,
1604.01017], it is expected that the ferro-deformation would occur at Z = 8, N
= 20 through a shape phase transition at N = 18 out of N =16. The shape
transition can be explained in terms of isospin dependent spin-orbital
interactions between neutrons in the d3/2 orbital and protons in the d5/2
orbital, by yielding both the neutron and the proton pseudo-shell
configurations built on each combined subshells. We argue that such a large
deformation at N = 18 would be responsible for the 26O to be unbound, leading
to a ground state neutron emitter. The ferro-deformation is mapped on the
nuclear chart such that is around the following critical proton, neutron
coordinates, (Z, N); (64, 104), (40, 64), (20, 40), (8, 20). This configuration
depicts a beautiful pattern coming from a harmonious order in the microscopic
quantum world. | nucl-th |
A study of the correlations between jet quenching observables at RHIC: Focusing on four types of correlation plots, $R_{\rm AA}$ vs. $v_2$, $R_{\rm
AA}$ vs. $I_{\rm AA}$, $I_{\rm AA}$ vs. $v_2^{I_{\rm AA}}$ and $v_2$ vs.\
$v_2^{I_{\rm AA}}$, we demonstrate how the centrality dependence of
\emph{correlations} between multiple jet quenching observables provide valuable
insight into the energy loss mechanism in a quark-gluon plasma. In particular
we find that a qualitative energy loss model gives a good description of
$R_{\rm AA}$ vs.\ $v_2$ only when we take $\Delta E\sim l^3$ and a medium
geometry generated by a model of the Color Glass Condensate. This same $\Delta
E\sim l^3$ model also qualitatively describes the trigger $p_T$ dependence of
$R_{\rm AA}$ vs.\ $I_{\rm AA}$ data and makes novel predictions for the
centrality dependence for this $R_{\rm AA}$ vs.\ $I_{\rm AA}$ correlation.
Current data suggests, albeit with extremely large uncertainty, that
$v_2^{I_{\rm AA}}\gg v_2$, a correlation that is difficult to reproduce in
current energy loss models. | nucl-th |
Two-nucleon knockout contributions to the $^{12}$C$(e,e'p)$ reaction in
the dip and {$Δ$}(1232) regions: The contributions from $^{12}$C$(e,e'pn)$ and $^{12}$C$(e,e'pp)$ to the
semi-exclusive $^{12}$C$(e,e'p)$ cross section have been calculated in an
unfactorized model for two-nucleon emission. We assume direct two-nucleon
knockout after virtual photon coupling with the two-body pion-exchange currents
in the target nucleus. Results are presented at several kinematical conditions
in the dip and $\Delta$(1232) regions. The calculated two-nucleon knockout
strength is observed to account for a large fraction of the measured $(e,e'p)$
strength above the two-nucleon emission threshold. | nucl-th |
Vacuum creation of quarks at the time scale of QGP thermalization and
strangeness enhancement in heavy-ion collisions: The vacuum parton creation in quickly varying external fields is studied at
the time scale of order 1 fm/$c$ typical for the quark-gluon plasma formation
and thermalization. To describe the pre-equilibrium evolution of the system the
transport kinetic equation is employed. It is shown that the dynamics of
production process at times comparable with particle inverse masses can deviate
considerably from that based on classical Schwinger-like estimates for
homogeneous and constant fields. One of the effects caused by non-stationary
chromoelectric fields is the enhancement of the yield of $s\bar{s}$ quark
pairs. Dependence of this effect on the shape and duration of the field pulse
is studied together with the influence of string fusion and reduction of quark
masses. | nucl-th |
$0^+$ to $2^+$ neutrinoless double-$β$ decay of $^{76}$Ge,
$^{82}$Se, $^{130}$Te and $^{136}$Xe in the microscopic interacting boson
model}: Here, we study the neutrinoless double-$\beta$ ($0\nu\beta\beta$) decay
between the ground state and the first $2^+$ state of $^{76}\mbox{Ge}
\rightarrow {}^{76}\mbox{Se}$, $^{82}\mbox{Se} \rightarrow{}^{82}\mbox{Kr}$,
$^{130}\mbox{Te} \rightarrow {}^{130}\mbox{Xe}$ and $^{136}\mbox{Xe}
\rightarrow {}^{136}\mbox{Ba}$ systems. The relevant nuclear matrix elements
(NMEs) involved in the process are calculated within the formalism of the
microscopic interacting boson model (IBM-2). The IBM-2 has been widely used to
obtain predictions for nuclear observables, such as the spectrum, but also to
explore the possible emergence of beyond-the-Standard Model effects in the weak
interactions of nuclei. Our calculations are carried out by considering the
exchange of a Majorana neutrino between two nucleons ($2N$-mechanism). In
addition to NMEs, we calculate the associated leptonic phase-space factors
(PSFs) using electron radial wave functions, which are obtained by solving
numerically the Dirac equation of a screened Coulomb potential that takes into
account finite nuclear size. By combining our IBM-2 results for the NMEs with
those for the PSFs along with experimental half-life limits, we can set limits
on the $\langle \lambda \rangle$ and $\langle \eta \rangle$ couplings of
left-right (L-R) models. | nucl-th |
Role of the isospin diffusion on cluster transfer in $^{12,14}$C +
$^{209}$Bi reactions: Heavy-ion collisions at near-barrier energies provide a crucial pathway for
investigating nucleon correlations and clustering structures.
Recent experimental results showed that the valence neutrons in light
projectiles obviously enhance the $\alpha$ transfer. This finding is extremely
puzzled and fascinating, because it violates the ground-state $Q$ value
systematics unexpectedly. In this work, the time-dependent Hartree-Fock
approach is utilized to investigate the cluster transfer. By comparing the
reactions $^{12,14}$C + $^{209}$Bi, we discover that above puzzling behavior is
because of the strong correlation between isospin diffusion and clustering. Our
calculations clearly show that the equilibrium of neutron-to-proton ratio
strongly inhibits the clustering. This work opens a prospect for investigating
the clustering in open quantum system. | nucl-th |
How well do we understand Beryllium-7 + proton -> Boron-8 + photon? An
Effective Field Theory perspective: We have studied the 7Be(p,photon)8B reaction in the Halo effective field
theory (EFT) framework. The leading order (LO) results were published in
Phys.Rev.C89,051602(2014) after the isospin mirror process, 7Li(n,photon)8Li,
was addressed in Phys.Rev.C89,024613(2014). In both calculations, one key step
was using the final shallow bound state asymptotic normalization coefficients
(ANCs) computed by ab initio methods to fix the EFT couplings. Recently we have
developed the next-to-LO (NLO) formalism (to appear soon), which could
reproduce other model results by no worse than 1% when the 7Be-p energy was
between 0 and 0.5 MeV. In our recent report (arXiv:1507.07239), a different
approach from that in Phys.Rev.C89,051602(2014) was used. We applied Bayesian
analysis to constrain all the NLO-EFT parameters based on measured S-factors,
and found tight constraints on the S-factor at solar energies. Our S(E=0 MeV)=
21.3 + - 0.7 eV b. The uncertainty is half of that previously recommended. In
this proceeding, we provide extra details of the Bayesian analysis, including
the computed EFT parameters' probability distribution functions (PDFs) and how
the choice of input data impacts final results. | nucl-th |
3- and 4- body meson- nuclear clusters: The binding energies and matter distributions for the 3- body systems like
$\phi$- meson + 2N, 2$\phi$ + N and 4- body system like $\phi$+3n are
calculated. For the 3- particle systems two- dimensional Faddeev equations in
the differential form are used. For the 4- body system $\phi$+3n the folding
model is applied. | nucl-th |
The resonance absorption probability function for neutron and
multiplicative integral: The analytical approximations for the moderating neutrons flux density like
Fermi spectra, widely used in reactor physics, involve the probability function
for moderating neutron to avoid the resonant absorption obtained using some
restrictive assumptions regarding the acceptable resonances width. By means of
multiplicative integral (Volterra integral) theory for a commutative algebra an
analytical expression for the probability function is obtained rigorously
without any restrictive assumptions. | nucl-th |
Periodic orbit bifurcations and local symmetry restorations in
exotic-shape nuclear mean fields: The semiclassical origins of the enhancement of shell effects in exotic-shape
mean-field potentials are investigated by focusing attention on the roles of
the local symmetries associated with the periodic-orbit bifurcations. The
deformed shell structures for four types of pure octupole shapes in the nuclear
mean-field model having a realistic radial dependence are analyzed. Remarkable
shell effects are shown for a large Y32 deformation having tetrahedral
symmetry. Much stronger shell effects found in the shape parametrization
smoothly connecting the sphere and the tetrahedron are investigated from the
view point of the classical-quantum correspondence. The local dynamical
symmetries associated with the bridge orbit bifurcations are shown to have
significant roles in emergence of the exotic deformed shell structures for
certain combinations of the surface diffuseness and the tetrahedral deformation
parameters. | nucl-th |
Deuteron disintegration in three dimensions: We compare results from the traditional partial wave treatment of deuteron
electro-disintegration with a new approach that uses three dimensional
formalism. The new framework for the two-nucleon (2N) system using a complete
set of isospin - spin states made it possible to construct simple
implementations that employ a very general operator form of the current
operator and 2N states. | nucl-th |
Newly Evaluated Neutron Reaction Data on Chromium Isotopes: Neutron reaction data for the set of major chromium isotopes were reevaluated
from the thermal energy range up to 20 MeV. In the low energy region, updates
to the thermal values together with an improved $R$-matrix analysis of the
resonance parameters characterizing the cluster of large $s$-wave resonances
for $^{50,53}$Cr isotopes were performed. In the intermediate and high energy
range up to 20 MeV, the evaluation methodology used statistical nuclear
reaction models implemented in the EMPIRE code within the Hauser-Feshbach
framework to evaluate the reaction cross sections and angular distributions.
Exceptionally, experimental data were used to evaluate relevant cross sections
above the resonance region up to 5 MeV in the major $^{52}$Cr isotope.
Evaluations were benchmarked with Monte Carlo simulations of a small suite of
critical assemblies highly sensitive to Chromium data, and with the Oktavian
shielding benchmark to judge deep penetration performance with a 14-MeV D-T
neutron source. A significant improvement in performance is demonstrated
compared to existing evaluations. | nucl-th |
Searching for small droplets of hydrodynamic fluid in proton--proton
collisions at the LHC: In this paper, we investigate the hydrodynamic collectivity in
high-multiplicity events of proton-proton collisions at $\sqrt{s}=$ 13 TeV,
using iEBE-VISHNU hybrid model with three different initial conditions, namely,
HIJING, super-MC and TRENTo. With properly tuned parameters, hydrodynamic
simulations with each initial model give reasonable descriptions of the
measured two-particle correlations, including the integrated and $p_{\rm
T}$-differential flow for all charged and identified hadrons. However, the
hydrodynamic simulations fail to describe the negative value of the
four-particle cumulant $c_2^v\{4\}$ as measured in experiments. Further
investigations show that the non-linear response between the elliptic flow
$v_2$ and the initial eccentricity $\varepsilon_2$ becomes significant in the
small p-p systems. This leads to a large deviation from linear eccentricity
scaling and generates additional flow fluctuations, which results in a positive
$c_2^v\{4\}$ even with a negative $c_2^\varepsilon\{4\}$ from the initial
state. We also presented the first hydrodynamic calculations of multi-particle
mixed harmonic azimuthal correlations in p-p collisions, such as normalized
asymmetric cumulant $nac_n\{3\}$, normalized Symmetric-Cumulant,
$nsc_{2,3}\{4\}$ and $nsc_{2,4}\{4\}$. Although many qualitative features are
reproduced by the hydrodynamic simulations with chosen parameters, the measured
negative $nsc_{2,3}\{4\}$ cannot be reproduced. The failure of the description
of negative $c_2\{4\}$ and $nsc_{2,3}\{4\}$ triggers the question on whether
hydrodynamics with a fundamentally new initial state model could solve this
puzzle, or hydrodynamics itself might not be the appreciated mechanism of the
observed collectivity in p-p collisions at the LHC. | nucl-th |
Phase transition of the nucleon-antinucleon plasma at different ratios: We investigate phase transitions for the Walecka model at very high
temperatures. As is well known, depending on the parametrization of this model
and for the particular case of a zero chemical potential ($ \mu $), a first
order phase transition is possible \cite{theis}. We investigate this model for
the case in which $ \mu \ne 0 $. It turns out that, in this situation, phases
with different values of antinucleon-nucleon ratios and net baryon densities
may coexist. We present the temperature versus antinucleon-nucleon ratio as
well as the temperature versus the net baryon density for the coexistence
region. The temperature versus chemical potential phase diagram is also
presented. | nucl-th |
Symmetries at and Near Critical Points of Quantum Phase Transitions in
Nuclei: We examine several types of symmetries which are relevant to quantum phase
transitions in nuclei. These include: critical-point, quasidynamical, and
partial dynamical symmetries. | nucl-th |
Strictly finite-range potential for light and heavy nuclei: Strictly finite-range (SFR) potentials are exactly zero beyond their finite
range. Single-particle energies and densities as well as S-matrix pole
trajectories are studied in a few SFR potentials suited for the description of
neutrons interacting with light and heavy nuclei. The SFR potentials considered
are the standard cut-off Woods--Saxon (CWS) potentials and two potentials
approaching zero smoothly: the SV potential introduced by Salamon and Vertse
and the SS potential of Sahu and Sahu. The parameters of these latter were set
so that the potentials may be similar to the CWS shape. The range of the SV and
SS potentials scales with the cube root of the mass number of the core like the
nuclear radius itself. For light nuclei a single term of the SV potential (with
a single parameter) is enough for a good description of the neutron-nucleus
interaction. The trajectories are compared with a bench-mark for which the
starting points (belonging to potential depth zero) can be determined
independently. Even the CWS potential is found to conform to this bench-mark if
the range is identified with the cutoff radius. For the CWS potentials some
trajectories show irregular shapes, while for the SV and SS potentials all
trajectories behave regularly. | nucl-th |
Extracting $σ_{πN}$ from pionic atoms: We discuss a recent extraction of the $\pi N$ $\sigma$ term $\sigma_{\pi N}$
from a large-scale fit of pionic-atom strong-interaction data across the
periodic table. The value thus derived, $\sigma_{\pi N}^{\rm FG}=57\pm 7$ MeV,
is directly connected via the Gell-Mann--Oakes--Renner expression to the
medium-renormalized $\pi N$ isovector scattering amplitude near threshold. It
compares well with the value derived recently by the Bern-Bonn-J\"{u}lich
group, $\sigma_{\pi N}^{\rm RS}=58\pm 5$ MeV, using the Roy-Steiner equations
to control the extrapolation of the vanishingly small near threshold $\pi N$
isoscalar scattering amplitude to zero pion mass. | nucl-th |
Nuclear multifragmentation within the framework of different statistical
ensembles: The sensitivity of the Statistical Multifragmentation Model to the underlying
statistical assumptions is investigated. We concentrate on its micro-canonical,
canonical, and isobaric formulations. As far as average values are concerned,
our results reveal that all the ensembles make very similar predictions, as
long as the relevant macroscopic variables (such as temperature, excitation
energy and breakup volume) are the same in all statistical ensembles. It also
turns out that the multiplicity dependence of the breakup volume in the
micro-canonical version of the model mimics a system at (approximately)
constant pressure, at least in the plateau region of the caloric curve.
However, in contrast to average values, our results suggest that the
distributions of physical observables are quite sensitive to the statistical
assumptions. This finding may help deciding which hypothesis corresponds to the
best picture for the freeze-out stage | nucl-th |
The nuclear configurational entropy approach to dynamical QCD effects: This paper scrutinizes the dynamical QCD effects influence on mesons, namely,
the mean-square root radius of a pion in the holographic light-front wave
function setup, in the context of the AdS/QCD. The nuclear configurational
entropy, associated to mesonic holographic light-front wave functions, is shown
to have a critical point that optimizes the two parameters of the spin-improved
light-front wave function. The mean-square root pion radius and its
cross-section, computed upon these derived values, match the exact existing
experimental data to the precision of 0.14\%, below the experimental error at
the PDG. | nucl-th |
Energy dependence of heavy-ion initial condition in isobar collisions: Collisions of isobar nuclei, those with the same mass number but different
structure parameters, provide a new way to probe the initial condition of the
heavy ion collisions. Using transport model simulation of $^{96}$Ru+$^{96}$Ru
and $^{96}$Zr+$^{96}$Zr collisions at two energies $\sqrt{s_{\mathrm{NN}}}=0.2$
TeV and 5.02 TeV, where $^{96}$Ru and $^{96}$Zr nuclei have significantly
different deformations and radial profiles, we identify sources of
eccentricities contributing independently to the final state harmonic flow
$v_n$. The efficacy for flow generation is different amount these sources,
which qualitatively explains the modest yet significant energy dependence of
the isobar ratios of $v_n$. Experimental measurement of these ratios at the LHC
energy and compared with those obtained at RHIC will provide useful insight
into the collision-energy dependence of the initial condition. | nucl-th |
Path Integral Quantum Monte Carlo Method for Light Nuclei: I describe the first continuous space nuclear path integral quantum Monte
Carlo method, and calculate the ground state properties of light nuclei
including Deuteron, Triton, Helium-3 and Helium-4, using both local chiral
interaction up to next-to-next-to-leading-order and the Argonne $v_6'$
interaction. Compared with diffusion based quantum Monte Carlo methods such as
Green's function Monte Carlo and auxiliary field diffusion Monte Carlo, path
integral quantum Monte Carlo has the advantage that it can directly calculate
the expectation value of operators without tradeoff, whether they commute with
the Hamiltonian or not. For operators that commute with the Hamiltonian, e.g.,
the Hamiltonian itself, the path integral quantum Monte Carlo light-nuclei
results agree with Green's function Monte Carlo and auxiliary field diffusion
Monte Carlo results. For other operator expectations which are important to
understand nuclear measurements but do not commute with the Hamiltonian and
therefore cannot be accurately calculated by diffusion based quantum Monte
Carlo methods without tradeoff, the path integral quantum Monte Carlo method
gives reliable results. I show root-mean-square radii, one-particle number
density distributions, and Euclidean response functions for single-nucleon
couplings. I also systematically describe all the sampling algorithms used in
this work, the strategies to make the computation efficient, the error
estimations, and the details of the implementation of the code to perform
calculations. This work can serve as a benchmark test for future calculations
of larger nuclei or finite temperature nuclear matter using path integral
quantum Monte Carlo. | nucl-th |
The Non-Local Nature of the Nuclear Force and its Impact on Nuclear
Structure: We calculate the triton binding energy with a non-local NN potential that
fits the world NN data below 350 MeV with the almost perfect $\chi^2$/datum of
1.03. The non-locality is derived from relativistic meson field theory. The
result obtained in a 34-channel, charge-dependent Faddeev calculation is 8.00
MeV, which is 0.4 MeV above the predictions by local NN potentials. The
increase in binding energy can be clearly attributed to the off-shell behavior
of the non-local potential. Our result cuts in half the discrepancy between
theory and experiment established from local NN potentials. Implications for
other areas of microscopic nuclear structure, in which underbinding is a
traditional problem, are discussed. | nucl-th |
Correlation Effects in the Final-State Interaction for Quasielastic
$(e,e'p)$ Scattering: Color transparency predicts that, in $(e,e'p)$ reactions at large $Q^2$, the
final-state interaction becomes weaker than the reference value predicted from
the free-nucleon cross section. This reference value is usually evaluated in
the dilute-gas approximation to Glauber's multiple-scattering theory. We derive
the leading-order correction taking into account two-body correlations. Large
cancellations are found so that the overall correlation effect is small. | nucl-th |
Fusion Hindrance and the Role of Shell Effects in the Superheavy Mass
Region: We present the first attempt of the systematical investigation about the
effects of shell correction energy for dynamical processes, which include
fusion, fusion-fission and quasi-fission processes. In the superheavy mass
region, for the fusion process, the shell correction energy plays a very
important role and enhances the fusion probability, when the colliding partner
has strong shell structure. By analyzing the trajectory in the
three-dimensional coordinate space with a Langevin equation, we reveal the
mechanism of the enhancement of the fusion probability caused by shell effects. | nucl-th |
Generalized density functional equation of state for astrophysical
simulations with 3-body forces and quark gluon plasma: We present an updated general purpose nuclear equation of state (EoS) for use
in simulations of core-collapse supernovae, neutron star mergers and black hole
collapse. This EoS is formulated in the context of Density Functional Theory
(DFT) and is generalized to include all DFT EoSs consistent with known nuclear
and astrophysical constraints. This EoS also allows for the possibility of the
formation of material with a net proton excess ($Y_p > 0.5$) and has an
improved treatment of the nuclear statistical equilibrium and the transition to
heavy nuclei as the density approaches nuclear matter density. We include the
effects of pions in the regime above nuclear matter density and incorporate all
of the known mesonic and baryonic states at high temperature.
We analyze how a 3-body nuclear force term in the DFT at high densities
stiffens the EoS to satisfy the maximum neutron star constraint, however the
density dependence of the symmetry anergy and the formation of pions at high
temperatures allows for a softening of the central core in supernova collapse
calculations leading to a robust explosion. We also add the possibility of a
transition to a QCD chiral-symmetry-restoration and deconfinement phase at
densities above nuclear matter density. This paper details the physics, and
constraints on, this new EoS and presents an illustration of its implementation
in both neutron stars and core-collapse supernova simulations. We present the
first results from core-collapse supernova simulations with this EoS. | nucl-th |
Three-alpha-cluster structure of the 0^+ states in ^{12}C and the
effective alpha-alpha interactions: The $0^{+}$ states of $^{12}\mathrm{C}$ are considered within the framework
of the microscopic three-$\alpha$-cluster model. The main attention is paid to
accurate calculation of the width of the extremely narrow near-threshold
$0^+_2$ state which plays a key role in stellar nucleosynthesis. It is shown
that the $0^{+}_2$-state decays by means of the sequential mechanism
${^{12}\mathrm{C}} \to \alpha+{^8\mathrm{Be}} \to 3\alpha$. Calculations are
performed for a number of effective $\alpha - \alpha$ potentials which are
chosen to reproduce both energy and width of $^8\mathrm{Be}$. The parameters of
the additional three-body potential are chosen to fix both the ground and
excited state energies at the experimental values. The dependence of the width
on the parameters of the effective $\alpha - \alpha$ potential is studied in
order to impose restrictions on the potentials. | nucl-th |
Unifying Nucleon and Quark Dynamics at Finite Baryon Number Density: We present a model of baryonic matter which contains free constituent quarks
in addition to bound constituent quarks in nucleons. In addition to the common
linear sigma-model we include the exchange of vector-mesons. The percentage of
free quarks increases with baryon density but the nucleons resist a restoration
of chiral symmetry. | nucl-th |
q- Deformed Boson Expansions: A deformed boson mapping of the Marumori type is derived for an underlying
$su(2)$ algebra. As an example, we bosonize a pairing hamiltonian in a two
level space, for which an exact treatment is possible. Comparisons are then
made between the exact result, our q- deformed boson expansion and the usual
non - deformed expansion. | nucl-th |
Proton-Neutron Pairing Amplitude as a Generator Coordinate for
Double-Beta Decay: We treat proton-neutron pairing amplitudes, in addition to the nuclear
deformation, as generator coordinates in a calculation of the neutrinoless
double-beta decay of 76Ge. We work in two oscillator shells, with a Hamiltonian
that includes separable terms in the quadrupole, spin-isospin, and pairing
(isovector and isoscalar) channels. Our approach allows larger single-particle
spaces than the shell model and includes the important physics of the
proton-neutron quasiparticle random-phase approximation (QRPA) without
instabilities near phase transitions. After comparing the results of a
simplified calculation that neglects deformation with those of the QRPA, we
present a more realistic calculation with both deformation and proton-neutron
pairing amplitudes as generator coordinates. The future should see
proton-neutron coordinates used together with energy-density functionals. | nucl-th |
Self-Consistent Separable Rpa Approach for Skyrme Forces: Axial Nuclei: The self-consistent separable RPA (random phase approximation) method is
formulated for Skyrme forces with pairing. The method is based on a general
self-consistent procedure for factorization of the two-body interaction. It is
relevant for various density- and current-dependent functionals. The
contributions of the time-even and time-odd Skyrme terms as well as of the
Coulomb and pairing terms to the residual interaction are taken
self-consistently into account. Most of the expression have a transparent
analytical form, which makes the method convenient for the treatment and
analysis. The separable character of the residual interaction allows to avoid
diagonalization of high-rank RPA matrices and thus to minimize the calculation
effort. The previous studies have demonstrated high numerical accuracy and
efficiency of the method for spherical nuclei. In this contribution, the method
is specified for axial nuclei. We provide systematic and detailed presentation
of formalism and discuss different aspects of the model. | nucl-th |
Time-Dependent Hartree-Fock Approach to Nuclear Pasta at Finite
Temperature: We present simulations of neutron-rich matter at subnuclear densities, like
supernova matter, with the time-dependent Hartree-Fock approximation at
temperatures of several MeV. The initial state consists of $\alpha$ particles
randomly distributed in space that have a Maxwell-Boltzmann distribution in
momentum space. Adding a neutron background initialized with Fermi distributed
plane waves the calculations reflect a reasonable approximation of
astrophysical matter. This matter evolves into spherical, rod-like, and
slab-like shapes and mixtures thereof. The simulations employ a full Skyrme
interaction in a periodic three-dimensional grid. By an improved morphological
analysis based on Minkowski functionals, all eight pasta shapes can be uniquely
identified by the sign of only two valuations, namely the Euler characteristic
and the integral mean curvature. In addition, we propose the variance in the
cell density distribution as a measure to distinguish pasta matter from uniform
matter. | nucl-th |
Bimodality - a Sign of Critical Behavior in Nuclear Reactions: The recently discovered coexistence of multifragmentation and residue
production for the same total transverse energy of light charged particles can
be well reproduced in numerical simulations of the heavy ion reactions. A
detailed analysis shows that fluctuations (introduced by elementary
nucleon-nucleon collisions) determine which of the exit states is realized.
Thus we observe for the first time nonlinear dynamics in heavy ion reactions.
Also the scaling of the coexistence region with beam energy is well reproduced
in these results from the QMD simulation program. | nucl-th |
Comparative tests of isospin-symmetry-breaking corrections to
superallowed 0+-to-0+ nuclear beta decay: We present a test with which to evaluate the calculated
isospin-symmetry-breaking corrections to superallowed 0+-to-0+ nuclear beta
decay. The test is based on the corrected experimental Ft values being required
to satisfy conservation of the vector current (CVC). When applied to six sets
of published calculations, the test demonstrates quantitatively that only one
set -- the one based on the shell model with Saxon-Woods radial wave functions
-- provides satisfactory agreement with CVC. This test can easily be applied to
any sets of calculated correction terms that are produced in future. | nucl-th |
Thermal description of particle production in ultra-relativistic
heavy-ion collisions: The grand-canonical version of the thermal model is used to analyze the
ratios of particle abundances measured in ultra-relativistic heavy-ion
collisions. Exactly the same model is applied to study the heavy-ion reactions
at BNL AGS, CERN SPS, and BNL RHIC. A very good description is achieved for
Pb+Pb collisions at SPS, and for Au+Au collisions at RHIC. In these two cases
the value of the temperature characterizing the chemical freeze-out is
practically same: T=168 MeV at SPS and T=165 MeV at RHIC. On the other hand,
the particle ratios measured in the collisions of lighter nuclei are described
only in the qualitative way. We discuss also the effect of the possible
in-medium modifications of hadron masses and widths on the thermal fits. For
Pb+Pb collisions at SPS and Au+Au collisions at RHIC we find that the chi^2
fits favor slightly a moderate (20%) decrease of the masses. In-medium
modifications of the widths have little effect on the fits, unless they are
increased by a factor larger than 2. We study in detail the thermodynamic
conditions characterizing the chemical freeze-out. In particular, we find that
the average baryon energy is 1.6 GeV and the average meson energy is 0.9 GeV.
This difference reflects a different behavior of the mass spectra of mesons and
baryons. | nucl-th |
Charge-Exchange Reaction pD->n(pp) in the Bethe-Salpeter Approach: The deuteron charge - exchange reaction pD->n(pp) for the low values of
momentum transfer and small excitation energies of final pp - pair is
considered in the framework of Bethe - Salpeter approach. The method of
calculation of the observables is developed for the case, when the pp - pair is
in $^1S_0$ - state. The methodical numerical calculations of the differetial
cross sections and tensor analysing powers are presented. The reaction under
consideration is predicted to be a solid base for construction of the deuteron
tensor polarimeter at high energies, and also to obtain some additional
information about elementary nucleon - nucleon charge - exchange amplitude. | nucl-th |
Heavy ion collisions at intermediate energies in a quark-gluon exchange
framework: Heavy ion collisions at intermediate energies can be studied in the context
of the Vlasov-Uehling-Uhlenbeck (VUU) model. One of the main features in this
model is the nucleon-nucleon (NN) cross section in the collisional term. Quark
interchange plays a role in the NN interaction and its effect can be observed
in the cross section. We explore the possibility that quark interchange effects
can appear in observables at energies lower than RHIC. | nucl-th |
Probing the resonance of Dirac particle by the application of complex
momentum representation: Resonance plays critical roles in the formation of many physical phenomena,
and several methods have been developed for the exploration of resonance. In
this work, we propose a new scheme for resonance by solving the Dirac equation
in complex momentum representation, in which the resonant states are exposed
clearly in complex momentum plane and the resonance parameters can be
determined precisely without imposing unphysical parameters. Combining with the
relativistic mean-field theory, this method is applied to probe the resonances
in $^{120}$Sn with the energies, widths, and wavefunctions being obtained.
Comparing with other methods, this method is not only very effective for narrow
resonances, but also can be reliably applied to broad resonances. | nucl-th |
Pre-equilibrium dynamics and heavy-ion observables: To bracket the importance of the pre-equilibrium stage on relativistic
heavy-ion collision observables, we compare simulations where it is modeled by
either free-streaming partons or fluid dynamics. These cases implement the
assumptions of extremely weak vs. extremely strong coupling in the initial
collision stage. Accounting for flow generated in the pre-equilibrium stage, we
study the sensitivity of radial, elliptic and triangular flow on the switching
time when the hydrodynamic description becomes valid. Using the hybrid code
iEBE-VISHNU we perform a multi-parameter search, constrained by particle
ratios, integrated elliptic and triangular charged hadron flow, the mean
transverse momenta of pions, kaons and protons, and the second moment $\langle
p_T^2\rangle$ of the proton transverse momentum spectrum, to identify optimized
values for the switching time $\tau_s$ from pre-equilibrium to hydrodynamics,
the specific shear viscosity $\eta/s$, the normalization factor of the
temperature-dependent specific bulk viscosity $(\zeta/s)(T)$, and the switching
temperature $T_\mathrm{sw}$ from viscous hydrodynamics to the hadron cascade
UrQMD. With the optimized parameters, we predict and compare with experiment
the $p_T$-distributions of $\pi$, $K$, $p$, $\Lambda$, $\Xi$ and $\Omega$
yields and their elliptic flow coefficients, focusing specifically on the
mass-ordering of the elliptic flow for protons and Lambda hyperons which is
incorrectly described by VISHNU without pre-equilibrium flow. | nucl-th |
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