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Spinodal decomposition of low-density asymmetric nuclear matter: We investigate the dynamical properties of asymmetric nuclear matter at low
density. The occurrence of new instabilities, that lead the system to a
dynamical fragment formation, is illustrated, discussing in particular the
charge symmetry dependence of the structure of the most important unstable
modes. We observe that instabilities are reduced by charge asymmetry, leading
to larger size and time scales in the fragmentation process. Configurations
with less asymmetric fragments surrounded by a more asymmetric gas are
favoured. Interesting variances with respect to a pure thermodynamical
prediction are revealed, that can be checked experimentally. All these features
are deeply related to the structure of the symmetry term in the nuclear
Equation of State (EOS) and could be used to extract information on the low
density part of the EOS. | nucl-th |
Study of np-scattering for S, P and D Waves using Deng-Fan Potential by
Phase Function Method: In this paper, the np - scattering phase shifts and cross section for S,P and
D partial waves have been obtained for energies below the pion threshold, by
considering Deng-Fan potential as model of interaction. The radial time
independent Schr\"odinger equation has been analytically solved using Nikiforov
- Uvarov method to obtain the energy expression for ground state of np system.
Utilising this, the scattering phase shifts for $^3S_1$ have been obtained
using phase function method. The phase equations for various scattering states
$^1S_0$, $^1P_1$, $^3P_{0,1,2}$, $^1D_2$, and $^3D_{1,2,3}$ have been
numerically solved for obtaining corresponding scattering phase shifts and
their respective partial cross section. The total scattering cross sections
computed at various energies are found to be closely matching with experimental
data. The low energy scattering parameters determined from scattering phase
shifts of $^3S_1$ and $^1S_0$ are reasonably close to experimental ones. Hence,
Deng-Fan potential is a good phenomenological potential to understand the np -
scattering system. | nucl-th |
A microscopic benchmark-study of triaxiality in low-lying states of 76Kr: We report on a seven-dimensional generator coordinate calculation in the two
deformation parameters $\beta$ and $\gamma$ together with projection on
three-dimensional angular momentum and two particle numbers for the low-lying
states in $^{76}$Kr. These calculations are based on covariant density
functional theory. Excellent agreement is found with the data for the spectrum
and the electric multipole transition strengths. This answers the important
question of dynamic correlations and triaxiality in a fully microscopic way. We
find that triaxial configurations dominate both the ground state and the quasi
$\gamma$-band. This yields a different picture from the simple interpretation
in terms of "coexistence of a prolate ground state with an oblate low-lying
excited state", which is based on the measured sign of spectroscopic quadrupole
moments. This study also provides for the first time a benchmark for the
collective Hamiltonian in five dimensions. Moreover, we point out that the
staggering phase of the $\gamma$-band is not a safe signature for rigid
triaxiality of the low-energy structure. | nucl-th |
Foundations of the proxy-SU(3) symmetry in heavy nuclei: We show that within the proxy-SU(3) scheme the wave functions of the normal
parity orbitals in a given nuclear shell are affected very little as a result
of the replacement of the abnormal parity orbitals by their 0[110] proxy-SU(3)
counterparts. | nucl-th |
Kaon fragmentation function from NJL-jet model: The NJL-jet model provides a sound framework for calculating the
fragmentation func- tions in an effective chiral quark theory, where the
momentum and isospin sum rules are satisfied without the introduction of ad hoc
parameters [1]. Earlier studies of the pion fragmentation func- tions using the
Nambu-Jona-Lasinio (NJL) model within this framework showed good qualitative
agreement with the empirical parameterizations. Here we extend the NJL-jet
model by including the strange quark. The corrections to the pion fragmentation
function and corresponding kaon fragmen- tation functions are calculated using
the elementary quark to quark-meson fragmentation functions from NJL. The
results for the kaon fragmentation function exhibit a qualitative agreement
with the empirical parameterizations, while the unfavored strange quark
fragmentation to pions is shown to be of the same order of magnitude as the
unfavored light quark's. The results of these studies are expected to provide
important guidance for the analysis of a large variety of semi-inclusive data. | nucl-th |
From QCD Symmetries to Nuclei and Neutron Stars: Global symmetries and symmetry breaking patterns of QCD with light quarks, in
particular chiral symmetry, provide basic guidance not only for low-energy
hadron physics but also for nuclear forces and the nuclear many-body problem.
Recent developments of Chiral Effective Field Theory applications to nuclear
and neutron matter are summarized, with special emphasis on a
(non-perturbative) extension using functional renormalisation group methods.
Topics include: nuclear thermodynamics, extrapolations to dense baryonic matter
and constraints from neutron star observables. | nucl-th |
Extended parity doublet model with a new transport code: A new transport code "DaeJeon Boltzmann-Uehling-Uhlenbeck (DJBUU)" had been
developed and enables to describe the dynamics of heavy-ion collisions in
low-energy region. To confirm the validity of the new code, we first calculate
Au + Au collisions at Ebeam = 100 and 400A MeV and also perform the box
calculation to check the detail of collisions and Pauli blocking without
mean-field potential as suggested by the Transport Code Comparison Project.
After confirming the validity of new transport code, we study low-energy
heavy-ion collisions with an extended parity doublet model. Since the
distinctive feature of the parity doublet model is the existence of the chiral
invariant mass that contributes to the nucleon mass, we investigate how
physical quantities depend on the chiral invariant mass in heavy ion collisions
at low energies. For this, we calculate physical quantities such as the
effective nucleon mass in central collisions and transverse flow in
semi-central collisions of Au + Au at Ebeam = 400A MeV with different values of
the chiral invariant masses. | nucl-th |
The adjoint neutron transport equation and the statistical approach for
its solution: The adjoint equation was introduced in the early days of neutron transport
and its solution, the neutron importance, has ben used for several applications
in neutronics. The work presents at first a critical review of the adjoint
neutron transport equation. Afterwards, the adjont model is constructed for a
reference physical situation, for which an analytical approach is viable, i.e.
an infinite homogeneous scattering medium. This problem leads to an equation
that is the adjoint of the slowing-down equation that is well-known in nuclear
reactor physics. A general closed-form analytical solution to such adjoint
equation is obtained by a procedure that can be used also to derive the
classical Placzek functions. This solution constitutes a benchmark for any
statistical or numerical approach to the adjoint equation. A sampling technique
to evaluate the adjoint flux for the transport equation is then proposed and
physically interpreted as a transport model for pseudo-particles. This can be
done by introducing appropriate kernels describing the transfer of the
pseudo-particles in phase space. This technique allows estimating the
importance function by a standard Monte Carlo approach. The sampling scheme is
validated by comparison with the analytical results previously obtained. | nucl-th |
The stifness of the supranuclear equation of state (once again): We revisit the present status of the stiffness of the supranuclear equations
of state, particularly the solutions that increase the stiffness in the
presence of hyperons, the putative transition to a quark matter phase and the
robustness of massive compact star observations. | nucl-th |
Spin 1 inversion: a Majorana tensor force for deuteron alpha scattering: We demonstrate, for the first time, successful S-matrix to potential
inversion for spin one projectiles with non-diagonal $S^j_{ll'}$ yielding a
$T_{\rm R}$ interaction. The method is a generalization of the
iterative-perturbative, IP, method. We present a test case indicating the
degree of uniqueness of the potential. The method is adapted, using established
procedures, into direct observable to potential inversion, fitting $\sigma$,
${\rm i}T_{11}$, $T_{20}$, $T_{21}$ and $T_{22}$ for d + alpha scattering over
a range of energies near 10 MeV. The $T_{\rm R}$ interaction which we find is
very different from that proposed elsewhere, both real and imaginary parts
being very different for odd and even parity channels. | nucl-th |
The pp -> p Lambda K+ and pp -> p Sigma0 K+ Reactions in the Chiral
Unitary Approach: We study the pp -> p Lambda K+ and pp -> p Sigma0 K+ reactions near threshold
by using a chiral unitary approach. We consider the single-pion and single-kaon
exchange as well as the final state interactions of nucleon-hyperon, K-hyperon
and K-nucleon systems. Our results on the total cross section of the pp -> p
Lambda K+ reaction is consistent with the experimental data, and the
experimental observed strong suppression of Sigma0 production compared to
Lambda production at the same excess energy can also be explained in our model. | nucl-th |
Electric-dipole transitions in $^6$Li with a fully microscopic six-body
calculation: Exploring new excitation modes and the role of the nuclear clustering has
been of great interest. An interesting speculation was made in the recent
photoabsorption measurement of $^6$Li that implied the importance of the
nuclear clustering. To understand the excitation mechanism of $^6$Li, we
perform a fully microscopic six-body calculation on the electric-dipole ($E1$)
transitions and discuss how $^6$Li is excited by the $E1$ field as a function
of the excitation energy. We show the various cluster components in the
six-body wave functions and discuss the role of the nuclear clustering in the
$E1$ excitations of $^6$Li. | nucl-th |
Pairing correlation involving the continuum states: The Hartree-Fock-Bogoliubov equation for the ground states of even-even
atomic nuclei is solved using the canonical representation in the coordinate
space for zero range interactions like the Skyrme force. The gradient method is
improved for faster convergence to the solutions under constraint of
orthogonality between canonical orbitals. Necessity of the cut-off of the
pairing interaction is shown even when the number of the canonical orbitals are
restricted. A repulsive dependence of the interaction on the pairing density is
introduced as an implementation of the cut-off which leaves the HFB super
matrix state-independent. | nucl-th |
Neutrino-nucleon scattering rate in proto neutron star matter: We present a calculation of the neutrino-nucleon scattering cross section
which takes into account the nuclear correlations in the relativistic random
phase approximation. Our approach is based on a quantum hadrodynamics model
with exchange of $\sigma$, $\omega$, $\pi$, $\rho$ and $\delta$ mesons. In view
of applications to neutrino transport in the final stages of supernova
explosion and protoneutron star cooling, we study the evolution of the neutrino
mean free path as a function of density, proton-neutron asymmetry and
temperature. Special attention was paid to the issues of renormalization of the
Dirac sea, residual interactions in the tensor channel and meson mixing. It is
found that RPA corrections, with respect to the mean field approximation,
amount to only 10% to 15% at high density. | nucl-th |
Nuclear shell structures in terms of classical periodic orbits: Semiclassical periodic-orbit theory (POT) is applied to the physics of
nuclear structures, with the use of a realistic nuclear mean-field model given
by the radial power-law potential. Evolution of deformed shell structures,
which are responsible for various nuclear deformations, are clearly understood
from the contribution of short classical periodic orbits (POs). Bifurcations of
short POs, which imply underlying local dynamical symmetry, play significant
role there. The effect of the spin degree of freedom is also investigated in
relevance to the pseudospin symmetry in spherical nuclei and the prolate-oblate
asymmetry in shell structures of nuclei with quadrupole-type deformations. | nucl-th |
Photodisintegration of the Three-Nucleon Systems and their
Polarizabilities: The total photodisintegration cross sections of three-body nuclei are
calculated with semirealistic NN potentials below pion threshold. Full final
state interaction with Coulomb force is taken into account via the Lorentz
integral transform method. The experimental total cross sections are well
described and the sum rule $\sigma_{-1}(^3$H) agrees with elastic electron
scattering data. The calculated ^3He polarizability is 0.15 fm^3. | nucl-th |
Final state interaction in the pn and nn decay channels of
$^4_Λ$He: We study the effects of final state interactions in the non-mesonic weak
decay $\Lambda N \rightarrow nN$ (n is a neutron and N is either a neutron or a
proton) of the hypernucleus $_\Lambda^4$He. Using a three-body model the
effects of distortion of the interaction of the emitted nucleon pair with the
residual nucleus is considered. We also study the influence of the final state
interaction between the emitted nucleons using the Migdal-Watson model. The
effect of spin symmetries in the final state of the pair is also considered.
Based on our calculations, we conclude that final state interactions play a
minor role in the kinetic energy spectrum of the emitted nucleon pair. | nucl-th |
Charmonium dissociation in collision with phi meson in hadronic matter: The phi-charmonium dissociation reactions in hadronic matter are studied.
Unpolarised cross sections for 12 reactions are calculated in the Born
approximation, in the quark-interchange mechanism and with a
temperature-dependent quark potential. The potential leads to remarkable
temperature dependence of the cross sections. With the cross sections and the
phi distribution function we calculate the dissociation rates of the charmonia
in the interactions with the phi meson in hadronic matter. The dependence of
the rates on temperature and charmonium momentum is meaningful to the influence
of phi mesons on charmonium suppression. | nucl-th |
An Extended Approximation for the Lowest-lying States in Odd-mass Nuclei: An enhanced model, based on the Extended Boson Approximation, for the
lowest-lying states in odd-mass nuclei is presented. Our approach is built on
the Quasiparticle Phonon Model, extending it to take into account the ground
state correlations due to the action of the Pauli principle more accurately
than in the conventional theory. The derived interaction strengths between the
quasiparticles and the phonons in this model depend on the quasiparticle
occupation numbers explicitly coupling the odd-mass nucleus equations with
those of the even-even core. Within this model we calculated the transition
probabilities in several Te, Xe and Ba isotopes with A$\approx$130. | nucl-th |
Nuclear Masses and Neutron Stars: Precision mass spectrometry of neutron-rich nuclei is of great relevance for
astrophysics. Masses of exotic nuclides impose constraints on models for the
nuclear interaction and thus affect the description of the equation of state of
nuclear matter, which can be extended to describe neutron-star matter. With
knowledge of the masses of nuclides near shell closures, one can also derive
the neutron-star crustal composition. The Penning-trap mass spectrometer
ISOLTRAP at CERN-ISOLDE has recently achieved a breakthrough measuring the mass
of 82Zn, which allowed constraining neutron-star crust composition to deeper
layers (Wolf et al., PRL 110, 2013). We perform a more detailed study on the
sequence of nuclei in the outer crust of neutron stars with input from
different nuclear models to illustrate the sensitivity to masses and the
robustness of neutron-star models. The dominant role of the N=50 and N=82
closed neutron shells for the crustal composition is confirmed. | nucl-th |
The method of multiple internal reflections in a description of
tunneling evolution of nonrelativistic particles and photons: A non-stationary method for tunneling description of non-relativistic
particles and photons through a barrier on the basis of consideration of the
multiple internal reflections of vawe packets in relation of barrier boundaries
is presented. The method is described in details and proved in the case of the
one-dimentional tunneling of the particle through the rectangular barrier. For
problems of the tunneling of the particle through the spherically symmetric
barrier and of the photon through the one-dimensional barrier the amplitudes of
transmitted and reflected wave packets in relation to the barrier, times of the
tunneling and the reflection are found using of the method. Hartman's and
Fletcher's effect is analysed. | nucl-th |
Relativistic descriptions of inclusive quasielastic electron scattering:
application to scaling and superscaling ideas: An analysis of inclusive quasielastic electron scattering is presented using
different descriptions of the final state interactions within the framework of
the relativistic impulse approximation. The relativistic Green's function
approach is compared with calculations based on the use of relativistic purely
real mean field potentials in the final state. Both approaches lead to a
redistribution of the strength but conserving the total flux. Results for the
differential cross section at different energies are presented. Scaling
properties are also analyzed and discussed. | nucl-th |
An effective formulation on quantum hadrodynamics at finite temperatures
and densities: According to Wick's theorem, the second order self-energy corrections of
hadrons in the hot and dense nuclear matter are calculated. Furthermore, the
Feynman rules are summarized, and an effective formulation on quantum
hadrodynamics at finite temperatures and densities is evaluated. As the strong
couplings between nucleons are considered, the self-consistency of this method
is discussed in the framework of relativistic mean-field approximation. Debye
screening masses of the scalar and vector mesons in the hot and dense nuclear
matter are calculated with this method in the relativistic mean-field
approximation. The results are different from those of thermofield dynamics and
Brown-Rho conjecture. Moreover, the effective masses of the photon and the
nucleon in the hot and dense nuclear matter are discussed. | nucl-th |
Gluon distributions in nuclei probed at the CERN Large Hadron Collider: Using updated gluon distributions from global fits to data, we investigate
the sensitivity of direct photoproduction of heavy quarks and exclusive
production of vector mesons to varying strength of gluon modifications.
Implications of using these processes for constraining nuclear gluon
distributions are discussed. | nucl-th |
Isoscalar giant monopole resonance in Sn isotopes using a quantum
molecular dynamics model: The isoscalar giant monopole resonance (ISGMR) in Sn isotopes and other
nuclei is investigated in the framework of the isospin-dependent quantum
molecular dynamics (IQMD) model. The spectrum of GMR is calculated by taking
the root-mean-square (RMS) radius of a nucleus as its monopole moment. The peak
energy, the full width at half maximum (FWHM), and the strength of GMR
extracted by a Gaussian fit to the spectrum have been studied. The GMR peak
energies for Sn isotopes from the calculations using a mass-number dependent
Gaussian wave-packet width $\sigma_r$ for nucleons are found to be
overestimated and show a weak dependence on the mass number compared with the
experimental data. However, it is found that experimental data of the GMR peak
energies for $^{56}$Ni, $^{90}$Zr, and $^{208}$Pb as well as Sn isotopes can be
nicely reproduced after taking into account the isospin dependence in isotope
chains in addition to the mass number dependence of $\sigma_r$ for nucleons in
the IQMD model calculation. | nucl-th |
Ferromagnetism of Nuclear Matter in the Relativistic Approach: We study the spin-polarization mechanism in the highly dense nuclear matter
with the relativistic mean-field approach. In the relativistic Hartree-Fock
framework we find that there are two kinds of spin-spin interaction channels,
which are the axial-vector and tensor exchange ones. If each interaction is
strong and different sign, the system loses the spherical symmetry and holds
the spin-polarization in the high-density region. When the axial-vector
interaction is negative enough, the system holds ferromagnetism. | nucl-th |
Neutron Stars and the High Density Equation of State: One of the key ingredients to understand the properties of neutrons stars is
the equation of state at finite densities far beyond nuclear saturation.
Investigating the phase structure of quark matter that might be realized in the
core of NS inspires theory and observation. We discuss recent results of our
work to point out our view on challenges and possibilities in this evolving
field by means of a few examples. | nucl-th |
Embedding nuclear physics inside the unitary window: The large values of the singlet and triplet scattering lengths locate the
two-nucleon system close to the unitary limit, the limit in which these two
values diverge. As a consequence, the system shows a continuous scale
invariance which strongly constrains the values of the observables, a
well-known fact already noticed a long time ago. The three-nucleon system shows
a discrete scale invariance that can be observed by correlations of the triton
binding energy with other observables as the doublet nucleon-deuteron
scattering length or the alpha-particle binding energy. The low-energy dynamics
of these systems is universal; it does not depend on the details of the
particular way in which the nucleons interact. Instead, it depends on a few
control parameters, the large values of the scattering lengths and the triton
binding energy. Using a potential model with variable strength set to give
values to the control parameters, we study the spectrum of $A=2,3,4,6$ nuclei
in the region between the unitary limit and their physical values. In
particular, we analyze how the binding energies emerge from the unitary limit
forming the observed levels. | nucl-th |
Beyond-mean-field theories with zero-range effective interactions. A way
to handle the ultraviolet divergence: Zero-range effective interactions are commonly used in nuclear physics and in
other domains to describe many-body systems within the mean-field model. If
they are used within a beyond-mean-field framework, contributions to the total
energy that display an ultraviolet divergence are found. We propose a general
strategy to regularize this divergence and we illustrate it in the case of the
second-order corrections to the equation of state (EOF) of uniform symmetric
matter. By setting a momentum cutoff $\Lambda$, we show that for every
(physically meaningful) value of $\Lambda$ it is possible to determine a new
interaction such that the EOS with the second-order corrections reproduces the
empirical EOS, with a fit of the same quality as that obtained at the
mean-field level. | nucl-th |
Microsopic nuclear level densities by the shell model Monte Carlo method: The configuration-interaction shell model approach provides an attractive
framework for the calculation of nuclear level densities in the presence of
correlations, but the large dimensionality of the model space has hindered its
application in mid-mass and heavy nuclei. The shell model Monte Carlo (SMMC)
method permits calculations in model spaces that are many orders of magnitude
larger than spaces that can be treated by conventional diagonalization methods.
We discuss recent progress in the SMMC approach to level densities, and in
particular the calculation of level densities in heavy nuclei. We calculate the
distribution of the axial quadrupole operator in the laboratory frame at finite
temperature and demonstrate that it is a model-independent signature of
deformation in the rotational invariant framework of the shell model. We
propose a method to use these distributions for calculating level densities as
a function of intrinsic deformation. | nucl-th |
On the Delta-Nucleon and Rho - Pi Splittings: A QCD-inspired Look in
Free Hadrons versus Nuclei: Relationships between mass intervals for free hadrons and in nuclei are
studied in two theoretical approaches inspired by QCD: naive quark model and
skyrmion model, taking one example each from mesons and baryons, that of pi-rho
splitting in mesons, and nucleon-Delta splitting in baryons. Possible
deconfinement effects in nuclei are examined. | nucl-th |
Soft Modes, Quantum Transport and Kinetic Entropy: The effects of the propagation of particles which have a finite life-time and
an according width in their mass spectrum are discussed in the context of
transport descriptions. In the first part the coupling of soft photon modes to
a source of charged particles is studied in a classical model which can be
solved completely in analytical terms. The solution corresponds to a
re-summation of certain field theory diagrams. The general properties of broad
resonances in dense finite temperature systems are discussed at the example of
the $\rho$-meson in hadronic matter. The second part addresses the problem of
transport descriptions which also account for the damping width of the
particles. The Kadanoff--Baym equation after gradient approximation together
with the $\Phi$-derivable method of Baym provides a self-consistent and
conserving scheme. Memory effects appearing in collision term diagrams of
higher order are discussed. We derive a generalized expression for the
nonequilibrium kinetic entropy flow, which includes corrections from
fluctuations and mass-width effects. In special cases an $H$-theorem is proved.
Memory effects in collision terms provide contributions to the kinetic entropy
flow that in the Fermi-liquid case recover the famous bosonic type $T^3 \ln T$
correction to the specific heat of liquid Helium-3. | nucl-th |
Nuclear annihilation by antinucleons: We examine the momentum dependence of $\bar p$$p$ and $\bar n$$p$
annihilation cross sections by considering the transmission through a nuclear
potential and the $\bar p p$ Coulomb interaction. Compared to the $\bar n p$
annihilation cross section, the $\bar p p$ annihilation cross section is
significantly enhanced by the Coulomb interaction for projectile momenta below
$p_{\rm lab} <$ 500 MeV/$c$, and the two annihilation cross sections approach
the Pomeranchuk's equality limit [JETP Lett. {\bb 30}, 423 (1956)] at $p_{\rm
lab}\sim 500$ MeV/$c$. Using these elementary cross sections as the basic input
data, the extended Glauber model is employed to evaluate the annihilation cross
sections for $\bar n$ and $\bar p$ interaction with nuclei and the results
compare well with experimental data. | nucl-th |
Explaining Angular Correlations Observed at RHIC with Flow and Local
Charge Conservation: The observation of fluctuations of parity-odd angular observables at RHIC has
been interpreted as a signal of a local parity violation. We show how the
observed signal can be explained by local charge conservation at freeze-out
combined with elliptic flow. Calculations from a blast wave model, which
overlays thermal emission onto a collective flow profile, are shown to account
for the experimentally observed signal. | nucl-th |
Far-from-equilibrium slow modes and momentum anisotropy in expanding
plasma: The momentum distribution of particle production in heavy-ion collisions
encodes information about thermalization processes in the early-stage
quark-gluon plasma. We use kinetic theory to study the far-from-equilibrium
evolution of an expanding plasma with an anisotropic momentum-space
distribution. We identify slow and fast degrees of freedom in the
far-from-equilibrium plasma from the evolution of moments of this distribution.
At late times, the slow modes correspond to hydrodynamic degrees of freedom and
are naturally gapped from the fast modes by the inverse of the relaxation time,
$\tau_R^{-1}$. At early times, however, there are an infinite number of slow
modes with a gap inversely proportional to time, $\tau^{-1}$. From the
evolution of the slow modes we generalize the paradigm of the
far-from-equilibrium attractor to vector and tensor components of the
energy-momentum tensor, and even to higher moments of the distribution function
that are not part of the hydrodynamic evolution. We predict that initial-state
momentum anisotropy decays slowly in the far-from-equilibrium phase and may
persist until the relaxation time. | nucl-th |
Tin-accompanied and true ternary fission of $^{242}$Pu: True ternary fission and Tin-accompanied ternary fission of $^{242}$Pu are
studied by using Three Cluster Model. True ternary fission is considered as
formation of heavy fragments in the region $28\leq Z_1,Z_2,Z_3\leq 38$, with
comparable masses. The possible fission channels are predicted from
potential-energy calculations. Interaction potentials, Q-values and relative
yields for all possible fragmentations in equatorial and collinear
configurations are calculated and compared to each other. It is found out that
ternary fission with formation of a double magic nucleus like $^{132}Sn$ is
more probable than the other fragmentations. Also the kinetic energies of the
fragments for the group $Z_1=32$, $Z_2=32$ and $Z_3=30$ are calculated for all
combinations in the collinear geometry, as a sequential decay. | nucl-th |
Entanglement Maximization in Low-Energy Neutron-Proton Scattering: The entanglement properties of neutron-proton scattering are investigated
using a measure that counts the number of entangled pairs produced by the
action of a scattering operator on a given initial neutron-proton state. All
phase shifts relevant for scattering at laboratory energies up to 350 MeV are
used.
Entanglement is found to be maximized in very low energy scattering. At such
energies the Hamiltonian obeys Wigner SU(4) symmetry, and an entanglement
maximum is a sign of that symmetry. At higher energies the angular dependence
of entanglement is strong and the entanglement is large for many scattering
angles. The tensor force is shown to play a significant role in producing
entanglement at lab kinetic energies greater than about 50 MeV. | nucl-th |
Improved microscopic-macroscopic approach incorporating the effects of
continuum states: The Woods-Saxon-Strutinsky method (the microscopic-macroscopic method)
combined with Kruppa's prescription for positive energy levels, which is
necessary to treat neutron rich nuclei, is studied to clarify the reason for
its success and to propose improvements for its shortcomings. The reason why
the plateau condition is met for the Nilsson model but not for the Woods-Saxon
model is understood in a new interpretation of the Strutinsky smoothing
procedure as a low-pass filter. Essential features of Kruppa's level density is
extracted in terms of the Thomas-Fermi approximation modified to describe
spectra obtained from diagonalization in truncated oscillator bases. A method
is proposed which weakens the dependence on the smoothing width by applying the
Strutinsky smoothing only to the deviations from a reference level density. The
BCS equations are modified for the Kruppa's spectrum, which is necessary to
treat the pairing correlation properly in the presence of continuum. The
potential depth is adjusted for the consistency between the microscopic and
macroscopic Fermi energies. It is shown, with these improvements, that the
microscopic-macroscopic method is now capable to reliably calculate binding
energies of nuclei far from stability. | nucl-th |
Fluctuations in the number of intermediate mass fragments in small
projectile like fragments: The origin of fluctuations in the average number of intermediate mass
fragments seen in experiments in small projectile like fragments is discussed.
We argue that these can be explained on the basis of a recently proposed model
of projectile fragmentation. | nucl-th |
Metric anisotropies and nonequilibrium attractor for expanding plasma: We consider the evolution of a system of chargeless and massless particles in
an anisotropic space-time given by the Bianchi type I metric. Specializing to
the axis-symmetric case, we derive the framework of anisotropic hydrodynamics
from the Boltzmann equation in the relaxation-time approximation. We consider
the case of the axis-symmetric Kasner metric and study the approach to the
emergent attractor in near and far-off-equilibrium regimes. Further, by
relaxing the Kasner conditions on metric coefficients, we study the effect of
expansion geometries on the far-off-equilibrium attractor and discuss its
implications in the context of relativistic heavy-ion collisions. | nucl-th |
From Kuo-Brown to today's realistic shell-model calculations: This paper is an homage to the seminal work of Gerry Brown and Tom Kuo, where
shell model calculations were performed for 18O and 18F using an effective
interaction derived from the Hamada-Johnston nucleon-nucleon potential. That
work has been the first successful attempt to provide a description of nuclear
structure properties starting from the free nucleon-nucleon potential. We shall
compare the approach employed in the 1966 paper with the derivation of a modern
realistic shell-model interaction for sd-shell nuclei, evidencing the progress
that has been achieved during the last decades. | nucl-th |
On a variational principle model for the Nuclear Caloric curve: Following the lead of a recent work we perform a variational principle model
calculation for the nuclear caloric curve. A Skyrme type interaction with and
without momentum dependence is used. The calculation is done for a large
nucleus, i.e, in the nuclear matter limit. Thus we address the issue of volume
fragmentation only. Nonetheless the results are similar to the previous,
largely phenomenological calculation for a finite nucleus. We find the onset of
fragmentation can be sudden as a function of temperature/excitation energy. | nucl-th |
Pairing effects on spinodal decomposition of asymmetric nuclear matter: We investigate the impact of pairing correlations on the behavior of unstable
asymmetric nuclear matter at low temperature. We focus on the relative role of
the pairing interaction, coupling nucleons of the same type (neutrons or
protons), with respect to the symmetry potential, which enhances the
neutron-proton attraction, along the clusterization process driven by spinodal
instabilities. It is found that, especially at the transition temperature from
the normal to the superfluid phase, pairing effects may induce significant
variations in the isotopic content of the clusterized matter. This analysis is
potentially useful to gather information on the temperature dependence of
nuclear pairing and, in general, on the properties of clusterized low-density
matter, of interest also in the astrophysical context. | nucl-th |
Effect of liquid drop model parameters on nuclear liquid gas phase
transition: The phenomenon of liquid-gas phase transition occurring in heavy ion
collisions at intermediate energies is a subject of contemporary interest. In
statistical models of fragmentation, the liquid drop model is generally used to
calculate the ground state binding energies of the fragments. It is well known
that the surface and symmetry energy of the hot fragments at the low density
freeze out can be considerably modified. In addition to this, the level density
parameter also has a wide variation. The effect of variation of these
parameters is studied on fragmentation observables which are related to the
nuclear liquid gas phase transition. The canonical thermodynamical model which
has been very successful in describing the phenomenon of fragmentation is used
for the study. The shift in transition temperature owing to the variation in
liquid drop model parameters has been examined. | nucl-th |
Two-particle correlations at high-energy nuclear collisions,
peripheral-tube model revisited: In this paper, we give an account of the peripheral-tube model, which has
been developed to give an intuitive and dynamical description of the so-called
ridge effect in two-particle correlations in high-energy nuclear collisions.
Starting from a realistic event-by-event fluctuating hydrodynamical model
calculation, we first show the emergence of ridge + shoulders in the so-called
two-particle long-range correlations, reproducing the data. In contrast to the
commonly used geometric picture of the origin of the anisotropic flow, we can
explain such a structure dynamically in terms of the presence of high
energy-density peripheral tubes in the initial conditions. These tubes
violently explode and deflect the near radial flow coming from the interior of
the hot matter, which in turn produces a two-ridge structure in single-particle
distribution, with approximately two units opening in azimuth. When computing
the two-particle correlation, this will result in characteristic three-ridge
structure, with a high near-side ridge and two symmetric lower away-side ridges
or shoulders. Several anisotropic flows, necessary to producing ridge +
shoulder structure, appear naturally in this dynamical description. Using this
simple idea, we can understand several related phenomena, such as centrality
dependence and trigger-angle dependence. | nucl-th |
Dynamics of rotation in chiral nuclei: The dynamics of chiral nuclei is investigated for the first time with the
time-dependent and tilted axis cranking covariant density functional theories
on a three-dimensional space lattice in a microscopic and self-consistent way.
The experimental energies of the two pairs of the chiral doublet bands in
$^{135}$Nd are well reproduced without any adjustable parameters beyond the
well-defined density functional. A novel mechanism, i.e., chiral precession, is
revealed from the microscopic dynamics of the total angular momentum in the
body-fixed frame, whose harmonicity is associated with a transition from the
planar into aplanar rotations with the increasing spin. This provides a fully
microscopic and dynamical view to understand the chiral excitations in nuclei. | nucl-th |
Symmetry preserving truncations of the gap and Bethe-Salpeter equations: Ward-Green-Takahashi (WGT) identities play a crucial role in hadron physics,
e.g. imposing stringent relationships between the kernels of the one- and
two-body problems, which must be preserved in any veracious treatment of mesons
as bound-states. In this connection, one may view the dressed gluon-quark
vertex, $\Gamma_\mu^a$, as fundamental. We use a novel representation of
$\Gamma_\mu^a$, in terms of the gluon-quark scattering matrix, to develop a
method capable of elucidating the unique quark-antiquark Bethe-Salpeter kernel,
$K$, that is symmetry-consistent with a given quark gap equation. A strength of
the scheme is its ability to expose and capitalise on graphic symmetries within
the kernels. This is displayed in an analysis that reveals the origin of
$H$-diagrams in $K$, which are two-particle-irreducible contributions,
generated as two-loop diagrams involving the three-gluon vertex, that cannot be
absorbed as a dressing of $\Gamma_\mu^a$ in a Bethe-Salpeter kernel nor
expressed as a member of the class of crossed-box diagrams. Thus, there are no
general circumstances under which the WGT identities essential for a valid
description of mesons can be preserved by a Bethe-Salpeter kernel obtained
simply by dressing both gluon-quark vertices in a ladder-like truncation; and,
moreover, adding any number of similarly-dressed crossed-box diagrams cannot
improve the situation. | nucl-th |
Chiral properties of hadron correlators in nuclear matter: The constraints imposed by chiral symmetry on hadron correlation functions in
nuclear medium are discussed. It is shown that these constraints imply a
certain structure for the in-medium hadron correlators and lead to the
cancelation of the order $\rho m_\pi$ term in the in-medium nucleon correlator.
We also consider the effect of mixing of the chiral partners correlation
functions arising from the interaction of nuclear pions with corresponding
interpolating currents. It reflects the phenomena of partial restoration of
chiral symmetry. The different scenarios of such restoration are briefly
discussed. | nucl-th |
Freezeout systematics due to the hadron spectrum: We investigate systematics of the freezeout surface in heavy ion collisions
due to the hadron spectrum. The role of suspected resonance states that are yet
to be confirmed experimentally in identifying the freezeout surface has been
investigated. We have studied two different freezeout schemes - unified
freezeout scheme where all hadrons are assumed to freezeout at the same thermal
state and a flavor dependent sequential freezeout scheme with different
freezeout thermal states for hadrons with or without valence strange quarks.
The data of mean hadron yields as well as scaled variance of net proton and net
charge distributions have been analysed. We find the freezeout temperature $T$
to drop by $\sim5\%$ while the dimensionless freezeout parameters $\mu_B/T$ and
$VT^3$ ($\mu_B$ and $V$ are the baryon chemical potential and the volume at
freezeout respectively) are insensitive to the systematics of the input hadron
spectrum. The observed hint of flavor hierarchy in $T$ and $VT^3$ with only
confirmed resonances survives the systematics of the hadron spectrum. It is
more prominent between $\sqrt{s_{NN}}\sim10 - 100$ GeV where the maximum
hierarchy in $T\sim10\%$ and $VT^3\sim40\%$. However, the uncertainties in the
thermal parameters due to the systematics of the hadron spectrum and their
decay properties do not allow us to make a quantitative estimate of the flavor
hierarchy yet. | nucl-th |
Bohr Hamiltonian with Hulthen plus ring-shaped potential for triaxial
nuclei with deformation-dependent mass term: In this work, we present a new version of the Bohr collective Hamiltonian for
triaxial nuclei within Deformation-Dependent Mass formalism (DDM) using the
Hulth\'en potential. We shall call the developed model Z(5)-HD. Analytical
expressions for energy spectra are derived by means of the recent version of
the Asymptotic Iteration Method. The calculated numerical results of energies
and B(E2) transition rates are compared with the experimental data, and several
theoretical results from Z(5) model, the model Z(5)-H using the Hulth\'en
potential without DDM formalism as well as theoretical predictions of Z(5)-DD
model with Davidson potential using DDM formalism. The obtained results show an
overall agreement with experimental data and an important improvement in
respect to the other models. | nucl-th |
On the nuclear interaction. Potential, binding energy and fusion
reaction: The nuclear interaction is responsible for keeping neutrons and protons
joined in an atomic nucleus. Phenomenological nuclear potentials, fitted to
experimental data, allow one to know about the nuclear behaviour with more or
less success where quantum mechanics is hard to be used. A nuclear potential is
suggested and an expression for the potential energy of two nuclear entities,
either nuclei or nucleons, is developed. In order to estimate parameters in
this expression, some nucleon additions to nuclei are considered and a model is
suggested as a guide of the addition process. Coulomb barrier and energy for
the addition of a proton to each one of several nuclei are estimated by taking
into account both the nuclear and electrostatic components of energy. Studies
on the binding energies of several nuclei and on the fusion reaction of two
nuclei are carried out. | nucl-th |
Averaged transverse momentum correlations of hadrons in relativistic
heavy-ion collisions: We compile experimental data for the averaged transverse momentum
($\left\langle p_{T}\right\rangle $) of proton, $\Lambda$, $\Xi^{-}$,
$\Omega^{-}$ and $\phi$ at mid-rapidity in Au+Au collisions at $\sqrt{s_{NN}}=$
200, 39, 27, 19.6, 11.5, 7.7 GeV and in Pb+Pb collisions at $\sqrt{s_{NN}}=$
2.76 TeV, and find that experimental data of these hadrons exhibit systematic
correlations. We apply a quark combination model with equal-velocity
combination approximation to derive analytic formulas of hadronic $\left\langle
p_{T}\right\rangle $ in the case of exponential form of quark $p_{T}$ spectra
at hadronization. We use them to successfully explain the systematic
correlations exhibited in $\left\langle p_{T}\right\rangle $ data of
$p\Lambda$, $\Lambda\Xi^{-}$, $\Xi^{-}\Omega^{-}$ and $\Xi^{-}\phi$ pairs. We
also use them to successfully explain the regularity observed in $\left\langle
p_{T}\right\rangle $ of these hadrons as the function of
$(dN_{ch}/dy)/(N_{part}/2)$ at mid-rapidity in central heavy-ion collisions at
both RHIC and LHC energies. Our results suggest that the constituent quark
degrees of freedom and the equal-velocity combination of these constituent
quarks at hadronization play important role in understanding the production of
baryons and $\phi$ meson at these RHIC and LHC energies. | nucl-th |
Spinodal Instability at the Onset of Collective Expansion in Nuclear
Collisions: Using transport theory to model central Au + Au collisions in the energy
region of 20 - 110 MeV/u, at impact parameters b <= 5 fm, we predict a
measurable impact of spinoidal instability as the collective expansion sets in
with energy. Two transport models are employed, the pBUU model, solving a
Boltzmann-Uehling-Uhlenbeck equation, and the Brownian Motion (BM) model,
solving a set of Langevin equations to describe the motion of individual
nucleons in a noisy nuclear medium. We find without ambiguity, for the first
time, that a combination of delayed equilibration, onset of collective
expansion and the spinodal instability produces a pair of transient ring
structures, made of the projectile and target remnants, with spectator nucleons
predicted to end in the entities reminiscent of stones in jewelry, on the
rings. The ring structures, calculated in the configuration space and mapped
onto the velocity space, could be detected in experimental collective flow
data. | nucl-th |
Effects of the Lorentz invariance violation in Coulomb interaction in
nuclei and atoms: Anisotropy in the speed of light that has been constrained by
Michelson-Morley-type experiments also generates anisotropy in the Coulomb
interactions. This anisotropy can manifest itself as an energy anisotropy in
nuclear and atomic experiments. Here the experimental limits on Lorentz
violation in 21Ne are used to improve the limits on the Lorentz symmetry in the
photon sector, namely the anisotropy of the speed of light and the Coulomb
interactions, by 7 orders of magnitude in comparison with previous experiments:
the speed of light is isotropic to a part in E-28. | nucl-th |
Does the quark cluster model predict any isospin two dibaryon resonance?: We analyze the possible existence of a resonance in the $J^P=0^-$ channel
with isospin two by means of nucleon-$\Delta$ interactions based on the
constituent quark model. We solve the bound state and the scattering problem
using two different potentials, a local and a non-local one. The non-local
potential results to be the more attractive, although not enough to generate
the experimentally predicted resonance. | nucl-th |
Simultaneous Optical Model Analyses of Elastic Scattering, Breakup, and
Fusion Cross Section Data for the $^{6}$He + $^{209}$Bi System at
Near-Coulomb-Barrier Energies: Based on an approach recently proposed by us, simultaneous
$\chi^{2}$-analyses are performed for elastic scattering, direct reaction (DR)
and fusion cross sections data for the $^{6}$He+$^{209}$Bi system at
near-Coulomb-barrier energies to determine the parameters of the polarization
potential consisting of DR and fusion parts. We show that the data are well
reproduced by the resultant potential, which also satisfies the proper
dispersion relation. A discussion is given of the nature of the threshold
anomaly seen in the potential. | nucl-th |
Band-like structures and quartets in deformed N=Z nuclei: We provide a description of deformed $N=Z$ nuclei in a formalism of
$\alpha$-like quartets. Quartets are constructed variationally by resorting to
the use of proper intrinsic states. Various types of intrinsic states are
introduced which generate different sets of quartets for a given nucleus.
Energy spectra are generated via configuration-iteraction calculations in the
spaces built with these quartets. The approach has been applied to $^{24}$Mg
and $^{28}$Si in the $sd$ shell and to $^{48}$Cr in the $pf$ shell. In all
cases a good description of the low-lying spectra has been achieved. As a
peculiarity of the approach, a close correspondence is observed between the
various sets of quartets employed and the occurrence of well defined band-like
structures in the spectra of the systems under study. | nucl-th |
Exotic Shapes in ^{32}S suggested by the Symmetry-Unrestricted Cranked
Hartree-Fock Calculations: High-spin structure of ^{32}S is investigated by means of the cranked
Skyrme-Hartree-Fock method in the three-dimensional Cartesian-mesh
representation. Some interesting suggestions are obtained: 1) An internal
structure change (toward hyperdeformation) may occur at I>20 in the
superdeformed band, 2) A non-axial Y_{31} deformed band may appear in the yrast
line with 4<I<14. | nucl-th |
Finite temperature calculations for the spin polarized asymmetric
nuclear matter with the LOCV method: The lowest order constrained variational (LOCV) technique has been used to
investigate some of the thermodynamic properties of spin polarized hot
asymmetric nuclear matter, such as the free energy, symmetry energy,
susceptibility and equation of state. We have shown that the symmetry energy of
the nuclear matter is substantially sensitive to the value of spin
polarization.
Our calculations show that the equation of state of the polarized hot
asymmetric nuclear matter is stiffer for the higher values of the polarization
as well as the isospin asymmetry parameter. Our results for the free energy and
susceptibility show that the spontaneous ferromagnetic phase transition cannot
occur for hot asymmetric matter. | nucl-th |
Spin-orbit and tensor interactions in homogeneous matter of nucleons:
accuracy of modern many-body theories: We study the energy per particle of symmetric nuclear matter and pure neutron
matter using realistic nucleon--nucleon potentials having non central tensor
and spin--orbit components, up to three times the empirical nuclear matter
saturation density, $\rho_0=0.16$ fm$^{-3}$. The calculations are carried out
within the frameworks of the Brueckner--Bethe--Goldstone (BBG) and Correlated
Basis Functions (CBF) formalisms, in order to ascertain the accuracy of the
methods. The two hole--line approximation, with the continuous choice for the
single particle auxiliary potential, is adopted for the BBG approach, whereas
the variational Fermi Hypernetted Chain/Single Operator Chain theory, corrected
at the second order perturbative expansion level, is used in the CBF one. The
energies are then compared with the available Quantum and Variational Monte
Carlo results in neutron matter and with the BBG, up to the three hole--line
diagrams. For neutron matter and potentials without spin--orbit components all
methods, but perturbative CBF, are in reasonable agreement up to $\rho\sim$ 3
$\rho_0$. After the inclusion of the LS interactions, we still find agreement
around $\rho_0$, whereas it is spoiled at larger densities. The spin--orbit
potential lowers the energy of neutron matter at $\rho_0$ by $\sim$ 3--4 MeV
per nucleon. In symmetric nuclear matter, the BBG and the variational results
are in agreement up to $\sim$ 1.5 $\rho_0$. Beyond this density, and in
contrast with neutron matter, we find good agreement only for the potential
having spin--orbit components. | nucl-th |
Statistical pairing fluctuation and phase transition in $^{94}Mo$: In the framework of BCS model, we have applied the isothermal probability
distribution to take into account the statistical fluctuations in calculation
of thermodynamical properties of nuclei. The energy and the heat capacity are
calculated in $^{94}Mo$ nucleus using the mean gap parameter. The results are
compared with the values obtained based on the most probable values,
experimental data as well as some other theoretical models. We have shown that
heat capacity versus temperature behaves smoothly instead of singular behaviour
predicted by the standard BCS model. Also a smooth peak in heat capacity is
observed which is a signature of transition from normal to super fluid phase. | nucl-th |
Delta production in $\bar{p}$d-annihilation at rest: We study the $\Delta$-excitation in $\overline{p}d$ annihilation at rest. The
invariant spectra of the $\pi^+p$ and $\pi^-p$ systems selecting the protons
with momenta above 400 MeV/c are analyzed. The calculations reproduces
reasonably the experimental data. | nucl-th |
On the nucleon-nucleon interaction leading to a standing wave
instability in symmetric nuclear matter: We examine a recently proposed nucleon-nucleon interaction, claimed by its
authors both realistic and leading to a standing wave instability in symmetric
nuclear matter. Contrary to these claims, we find that this interaction leads
to a serious overbinding of 4He, 16O and 40Ca nuclei when the Hartree-Fock
method is properly applied. The resulting nuclear densities contradict the
experimental data and all realistic Hartree-Fock results. | nucl-th |
Realistic calculations for $c$-coefficients of the isobaric mass
multiplet equation in $1p0f$ shell nuclei: We present calculations for the $c$-coefficients of the isobaric mass
multiplet equation for nuclei from $A=42$ to $A=54$ based on input from three
realistic nucleon-nucleon interactions. We demonstrate that there is a clear
dependence on the short-ranged charge-symmetry breaking (CSB) part of the
strong interaction and that there is significant disagreement in the CSB part
between the commonly used CD-Bonn, N$^3$LO, and Argonne V18 nucleon-nucleon
interactions. In addition, we show that all three interactions give a CSB
contribution to the $c$-coefficient that is too large when compared to
experiment. | nucl-th |
Fully damped Mott oscillations in sub-barrier elastic scattering of
identical heavy ions and the nuclear interaction: We investigate the possible disappearance of Mott oscillations in the
scattering of bosonic nuclei at sub-barrier energies. This effect is universal
and happens at a critical value of the Sommerfeld parameter. It is also found
that the inclusion of the short-range nuclear interaction has a profound
influence on this phenomenon. Thus we suggest that the study of this lack of
Mott oscillation, which we call, "transverse isotropy" is a potentially useful
mean to study the nuclear interaction. | nucl-th |
Monte Carlo Modelling of the Electron Spectra of 235U- and 239Pu- Films,
Irradiated by Thermal Neutrons, Due to All Possible Mechanisms Excluding
b-Decay. Comparison With Experiment: The electron energy spectra, not connected to b-decay, of 235U- and
239Pu-films, irradiated by thermal neutrons, obtained by a Monte Carlo method
is presented in the given work. The modelling was performed with the help of a
computer code MCNP4C (Monte Carlo Neutron Photon transport code system),
allowing to carry out the computer experiments on joint transport of neutrons,
photons and electrons. The experiment geometry and the parameters of an
irradiation were the same, as in [11] (the thickness of a foil varied only). As
a result of computer experiments, the electron spectra was obtained for the
samples of 235U, 239Pu and uranium dioxide of 93 % enrichment representing a
set of films of 22 mm in diameter and different thickness: 0,001 mm, 0,005 mm,
0,02 mm, 0,01 mm, 0,1 mm, 1,0 mm; and also for the uranium dioxide film of 93 %
enrichment (diameter 22 mm and thickness 0,01mm), located between two
protective 0,025 mm aluminium disks (the conditions of experiment in [11]) and
the electron spectrum was fixed at the output surface of a protective disk. The
comparative analysis of the experimental [11] and calculated b--spectra is
carried out. | nucl-th |
Multi-pomeron repulsion and the Neutron-star mass: A multi-pomeron exchange potential (MPP) is proposed as a model for the
three-body repulsion indicated in neutron-star matter, which works universally
among three- and four-baryons. Its strength is determined by analyzing the
nucleus-nucleus scattering with the G-matrix folding model. The EoS in neutron
matter is obtained including the MPP contribution. The neutron-star mass is
calculated by solving the TOV equation. The maximum mass is obtained to be
larger than the observed one $1.97 M_{solar}$ on the basis of the experimental
data. | nucl-th |
Spin entanglement in neutron-proton scattering: In this Letter, I work out spin entanglement properties of neutron-proton
scattering using the exact S-matrix, generalizing previous works based on S
wave. The dependence of spin entanglement on momentum, scattering angle, and
initial spin configuration is investigated for realistic nuclear forces, while
low-energy properties of spin entanglement are analyzed within the framework of
pionless effective field theory at leading order. New connections are found
between spin entanglement and symmetry enhancement of strong interactions.
These results lead to a more complete understanding of how spin entanglement is
generated via neutron-proton interaction. They also lay the theoretical
foundation for controllable production of entangled nucleon-nucleon pairs in
future experiments. | nucl-th |
Nuclear recoil measurements in Superheated Superconducting Granule
detectors: The response of Superheated Superconducting Granule (SSG) devices to nuclear
recoils has been explored by irradiating SSG detectors with a 70Me$\!$V neutron
beam. In the past we have tested Al SSG and more recently, measurements have
been performed with Sn and Zn detectors. The aim of the experiments was to test
the sensitivity of SSG detectors to recoil energies down to a few ke$\!$V. In
this paper, the preliminary results of the neutron irradiation of a SSG
detector made of Sn granules 15-20$\mu$m in diameter will be discussed. For the
first time, recoil energy thresholds of $\sim$1ke$\!$V have been measured. | nucl-th |
Systematic study of the $α$ decay preformation factor of nuclei
around the $\boldsymbol{Z=82}$, $\boldsymbol{N=126}$ shell closures within a
generalized liquid drop model: In this work, we systematically study the $\alpha$ decay preformation factors
$P_{\alpha}$ and $\alpha$ decay half-lives of 152 nuclei around $Z$ = 82, $N$ =
126 closed shells based on a generalized liquid drop model while $P_{\alpha}$
is extracted from the ratio of the calculated $\alpha$ decay half-life to the
experimental one. The results show that there is an obvious linear relationship
between $P_{\alpha}$ and the product of valance protons (holes) $N_p$ and
valance neutrons (holes) $N_n$. At the same time, we extract the $$P_{\alpha}$
values of even-even nuclei around $\emph{Z}$ = 82, $\emph{N}$ = 126 closed
shells from the work of Sun \textit{et al.} [\href
{https://doi.org/10.1088/1361-6471/aac981} {J. Phys. G: Nucl. Part. Phys.
$\bm{45}$, 075106 (2018)}], in which the $P_{\alpha}$ can be calculated by two
different microscopic formulas. We find that the $P_{\alpha}$ are also related
to $N_pN_n$. Combining with our previous works [Sun \textit{et al.}, \href
{https://doi.org/10.1103/PhysRevC.94.024338} {Phys. Rev. C $\bm{94}$, 024338
(2016)}; Deng \textit{et al.}, \href {https://doi.org/10.1103/ PhysRevC
96.024318} {ibid. $\bm{96}$, 024318 (2017)}; Deng \textit{et al.}, \href
{https://doi.org/10.1103/PhysRevC.97.044322} {ibid. $\bm{97}$, 044322 (2018)}]
and the work of Seif \textit{et al.} [\href
{http://dx.doi.org/10.1103/PhysRevC.84.064608}{Phys. Rev. C $\bm{84}$, 064608
(2011)}], we suspect that this phenomenon of linear relationship for the nuclei
around those closed shells is model independent. It may be caused by the effect
of the valence protons (holes) and valence neutrons (holes) around the shell
closures. Finally, using the formula obtained by fitting the $P_{\alpha}$
calculated by the generalized liquid drop model (GLDM), we calculate the
$\alpha$ decay half-lives of these nuclei. The calculated results are agree
with the experimental data well. | nucl-th |
The Proton Electric Pygmy Dipole Resonance: The evolution of the low-lying E1 strength in proton-rich nuclei is analyzed
in the framework of the self-consistent relativistic Hartree-Bogoliubov (RHB)
model and the relativistic quasiparticle random-phase approximation (RQRPA).
Model calculations are performed for a series of N=20 isotones and Z=18
isotopes. For nuclei close to the proton drip-line, the occurrence of
pronounced dipole peaks is predicted in the low-energy region below 10 MeV
excitation energy. From the analysis of the proton and neutron transition
densities and the structure of the RQRPA amplitudes, it is shown that these
states correspond to the proton pygmy dipole resonance. | nucl-th |
Nuclear asymmetry energy and isovector stiffness within the effective
surface approximation: The isoscalar and isovector particle densities and the surface tension
coefficients at the average binding energy are used to derive analytical
expressions of the neutron skin thickness and the isovector stiffness of sharp
edged proton-neutron asymmetric nuclei. For most Skyrme forces these quantities
are significantly larger than the well known ones. Using the analytical
isovector surface energy constants in the framework of the hydrodynamical and
the Fermi-liquid droplet models the mean energies and the sum rules of the
isovector giant dipole resonances are in fair agreement with the experimental
data. | nucl-th |
Scaling Of Chiral Lagrangians And Landau Fermi Liquid Theory For Dense
Hadronic Matter: We discuss the Fermi-liquid properties of hadronic matter derived from a
chiral Lagrangian field theory in which Brown-Rho (BR) scaling is incorporated.
We identify the BR scaling as a contribution to Landau's Fermi liquid
fixed-point quasiparticle parameter from "heavy" isoscalar meson degrees of
freedom that are integrated out from a low-energy effective Lagrangian. We show
that for the vector (convection) current, the result obtained in the chiral
Lagrangian approach agrees precisely with that obtained in the
semi-phenomenological Landau-Migdal approach. This precise agreement allows one
to determine the Landau parameter that enters in the effective nucleon mass in
terms of the constant that characterizes BR scaling. When applied to the weak
axial current, however, these two approaches differ in a subtle way. While the
difference is small numerically, the chiral Lagrangian approach implements
current algebra and low-energy theorems associated with the axial response that
the Landau method misses and hence is expected to be more predictive. | nucl-th |
Uniform description of bulk observables in the hydrokinetic model of A+A
collisions at RHIC and LHC: A simultaneous description of hadronic yields; pion, kaon, and proton
spectra; elliptic flows; and femtoscopy scales in the hydrokinetic model of A+A
collisions is presented at different centralities for the top BNL Relativistic
Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC) 2.76-TeV
energies. The initial conditions are based on the Glauber Monte-Carlo
simulations. When going from RHIC to LHC energy in the model, the only
parameters changed are the normalization of the initial entropy defined by the
number of all charged particles in most central collisions, contribution to
entropy from binary collisions and baryonic chemical potential. The
hydrokinetic model is used in its hybrid version (hHKM), which provides the
correct match (at the isochronic hypersurface) of the decaying hadron matter
evolution with hadronic ultrarelativistic quantum molecular dynamics cascade.
The results are compared with the standard hybrid models where hydrodynamics
and hadronic cascade are matching just at the non-space-like hypersurface of
chemical freeze-out or on the isochronic hypersurface. The modification of the
particle number ratios at LHC caused, in particular, by the particle
annihilations at the afterburn stage is also analyzed. | nucl-th |
Implications of PREX--2 data on the electron--neutrino opacity in dense
matter: Motivated by the recent measurement of the neutron distribution radius of
${}^{208}$Pb from the PREX--2 data, I study the effects of the new G3(M)
parameter set constrained by PREX--2 data on the electron--neutrino scattering
in dense matter using the extended relativistic mean field (E--RMF) model. I
employ the G3(M) parameter set to describe the nuclear matter. The obtained
equation of state for the G3(M) parameter set has an excellent agreement with
experimental data and the chiral effective field theory calculation with
N$^3$LO 3N forces. I analyze both differential cross section of
electron--neutrino and electron--neutrino mean free path to observe their
sensitivity to the G3(M) parameter set. One finds that the differential cross
sections of electron--neutrino for different baryon densities have higher
values compared with that obtained for the TM1e and FSU Garnet parameter sets.
The higher cross section decreases the electron--neutrino mean free path. | nucl-th |
Effects of multiple single-particle basis states in scattering systems: Low-lying baryon resonances have been explored using Hamiltonian Effective
Field Theory (HEFT), in a formalism where resonances with a three-quark
component are described by both two-particle meson-baryon states and a bare
basis state. Here, we investigate the use of multiple bare states in the
Hamiltonian, to extend the formalism to higher energy ranges, and represent a
larger portion of the low-lying baryon spectrum. Introducing a second bare
state into a toy model extension of the low-energy $\Delta(1232)$ system, we
explore the influence of the second bare state on the position of poles in the
infinite-volume $T$-matrix. Considering the same system in a finite-volume, we
analyse the finite-volume energy spectrum in the presence of a second bare
state, providing insight into the interplay between two bare basis states,
representing quark-model states, and the relationship between infinite-volume
poles and finite-volume eigenstates. | nucl-th |
How low-energy weak reactions can constrain three-nucleon forces and the
neutron-neutron scattering length: We show that chiral symmetry and gauge invariance enforce relations between
the short-distance physics that occurs in a number of electroweak and pionic
reactions on light nuclei. Within chiral perturbation theory this is manifested
via the appearance of the same axial isovector two-body contact term in pi- d
-> n n gamma, p-wave pion production in NN collisions, tritium beta decay, pp
fusion, nu d scattering, and the hep reaction. Using a Gamow-Teller matrix
element obtained from calculations of pp fusion as input we compute the neutron
spectrum obtained in pi- d -> n n gamma. With the short-distance physics in
this process controlled from p p -> d e+ nu_e the theoretical uncertainty in
the nn scattering length extracted from pi- d -> n n gamma is reduced by a
factor larger than three, to <~0.05 fm. | nucl-th |
Hard probes in isobar collisions as a probe of the neutron skin: We present an estimate of the yield of hard probes expected for collisions of
the isobars $^{96}_{44}$Ru and $^{96}_{40}$Zr at collision energies reachable
at RHIC and the LHC\@. These yields are proportional to the number of binary
nucleon-nucleon interactions, which is characteristically different due to the
presence of the large neutron skin in $^{96}_{40}$Zr. This provides an
independent opportunity to measure the difference between the neutron skin of
$^{96}_{44}$Ru and $^{96}_{40}$Zr, which can provide an important constraint on
the Equation of State of cold neutron-rich matter. | nucl-th |
CFNS Ad-Hoc meeting on Radiative Corrections Whitepaper: Current precision scattering experiments and even more so many experiments
planed for the Electron Ion Collider will be limited by systematics. From the
theory side, a fundamental source of systematic uncertainty is the correct
treatment of radiative effects. To gauge the current state of technique and
knowledge, help the cross-pollination between different direction of nuclear
physics, and to give input to the yellow report process, the community met in
an ad-hoc workshop hosted by the Center for Frontiers in Nuclear Science, Stony
Brook University. This whitepaper is a collection of contributions to this
workshop. | nucl-th |
Dynamics of light hypernuclei in collisions of $^{197}$Au+$^{197}$Au at
GeV energies: The dynamics of light hypernuclei and nuclear clusters produced in
$^{197}$Au+$^{197}$Au collisions has been investigated thoroughly with a
microscopic transport model. All possible channels of hyperon production and
transportation of hyperons in nuclear medium are implemented into the model.
The light complex fragments are recognized with the Wigner density approach at
the stage of freeze out in nuclear collisions. The isospin diffusion in the
collisions is responsible for the neutron-rich cluster formation. The
collective flows of nuclear clusters are consistent with the experimental data
from FOPI collaboration. It is found that the influence of the hyperon-nucleon
potential on the free hyperons is negligible, but available for the light
hypernuclide formation. The directed and elliptic flows of $^{3}_{\Lambda}$H
and $^{4}_{\Lambda}$H at incident energies of 2, 2.5, 3, 3.5 and 4 GeV/nucleon
are investigated thoroughly and manifest the same structure with the nuclear
clusters. The hypernuclear yields are produced in a wide rapidity and momentum
regime with increasing the beam energy. | nucl-th |
The Local Potential Approximation for the Brueckner G-matrix: The Brueckner G-matrix for a slab of nuclear matter is analyzed in the
singlet $^1S$ and triplet $^3S+^3D$ channels. The complete Hilbert space is
split into two domains, the model subspace $S_0$, in which the two-particle
propagator is calculated explicitly, and the complementary one, $S'$, in which
the local potential approximation is used. This kind of local approximation was
previously found to be quite accurate for the $^1S$ pairing problem. A set of
model spaces $S_0(E_0)$ with different values of the cut-off energy $E_0$ is
considered, $E_0$ being the upper limit for the single-particle energies of the
states belonging to $S_0$. The independence of the G-matrix of $E_0$ is assumed
as a criterion of validity of the local potential approximation. Such
independence is obtained within few percent for $E_0=10 \div 20$ MeV for both
the channels under consideration. | nucl-th |
Theta+ formation in inclusive gamma D -> pK- X: We analyze the possibility to produce an intermediate Theta^+ via a
KN->\Theta+ formation process in gamma D-> pK^- X (X=nK^+,pK^0) reactions at
some specific kinematical conditions, in which a pK^- pair is knocked out in
the forward direction and its invariant mass is close to the mass of
Lambda(1520). The \Theta^+ signal may appear in the [\gamma D,pK^-] missing
mass distribution. The ratio of the signal (cross section at the \Theta^+ peak
position) to the smooth background processes varies from 0.7 to 2.5 depending
on the spin and parity of Theta+, and it decreases correspondingly if the pK^-
invariant mass is outside of the Lambda(1520)-resonance region. We analyze the
recent CLAS search for the Theta+ in the gamma D ->pK^-nK^+ reaction and show
that the conditions of this experiment greatly reduce the Theta+ formation
process making it difficult to extract a Theta+ peak from the data. | nucl-th |
Study of the $J/ψ\to φ(ω) f_2(1270)$, $J/ψ\to φ
(ω) f'_2(1525)$ and $J/ψ\to K^{*0}(892) \bar{K}^{* 0}_2(1430)$
decays: We present an approach to study the decay modes of the $J/\psi$ into a vector
meson and a tensor meson, taking into account the nature of the $f_2(1270)$,
$f'_2(1525)$, $\bar{K}^{* 0}_2(1430)$ resonances as dynamically generated
states from the vector meson-vector meson interaction. We evaluate four ratios
of partial decay widths in terms of a flavor dependent OZI breaking parameter
and the results obtained compare favorably with experiment. The fit to the data
is possible due to the particular strength and sign of the couplings of the
resonances to pairs of vector mesons given by the theory, thus providing a
nontrivial test for the idea of these tensor states as dynamically generated
from the vector-vector interaction. | nucl-th |
Proxy-$SU(4)$ symmetry in A=60-90 region: Applications of the proxy-$SU(3)$ model of Bonatsos and collaborators to
nuclei in A=60-90 region introduces proxy-$SU(4)$ symmetry. Shell model spaces
with single particle (sp) orbits $^1p_{3/2}$, $^1p_{1/2}$, $^0f_{5/2}$ and
$^0g_{9/2}$ are essential for these nuclei and also protons and neutrons in
this region occupy the same sp orbits. With this and applying the "proxy
scheme", the $^0g_{9/2}$ changes to $^0f_{7/2}$ giving the SGA $U(40) \supset
[U(10) \supset G \supset SO(3)] \otimes [SU(4) \supset SU_S(2) \otimes
SU_T(2)]$. With $G=SU(3)$, we have the proxy-$SU(3)$ model. It is easy to see
that proxy-$SU(3)$ symmetry implies goodness of the $SU(4)$ symmetry appearing
above, i.e. proxy-$SU(4)$ symmetry. Shell model calculations pointing out the
need for $^0g_{9/2}$ orbit, ground state masses, shape changes and shape
co-existence in A=60-90 region and GT distributions clearly show the importance
of proxy-$SU(4)$ in this mass region. Besides presenting this evidence, new
proxy schemes with $G=SU(5)$, $SO(6)$ and $SO(10)$ that are generated by good
proxy-$SU(4)$ symmetry are described in some detail. An important feature is
that the four proxy symmetries $SU(3)$, $SO(6)$, $SU(5)$ and $SO(10)$ appear
twice. | nucl-th |
Isovector dipole-resonance structure within the effective surface
approximation: The nuclear isovector-dipole strength structure is analyzed in terms of the
main and satellite (pygmy) peaks within the Fermi-liquid droplet model. Such a
structure is sensitive to the value of the surface symmetry-energy constant
obtained analytically for different Skyrme forces in the leptodermous effective
surface approximation. Energies, sum rules and transition densities of the main
and satellite peaks for specific Skyrme forces are qualitatively in agreement
with the experimental data and other theoretical calculations. | nucl-th |
Photoproduction of the Lambda(1405) on the proton and nuclei: We study the gamma p ---> K^+ Lambda(1405) reaction at energies close to
threshold using a chiral unitary model where the resonance is generated
dynamically from K^-p interaction with other channels constructed from the
octets of baryons and mesons. Predictions are made for cross sections into
several channels and it is shown that the detection of the K^+ is sufficient to
determine the shape and strength of the Lambda(1405) resonance. The
determination of the resonance properties in nuclei requires instead the
detection of the resonance decay channels. Pauli blocking effects on the
resonance, which have been shown to be very important for the resonance at rest
in the nucleus, are irrelevant here where the resonance is produced with a
large momentum. The nuclear modifications here would thus offer information on
the resonance and K^- nucleus dynamics complementary to the one offered so far
by K^- atoms. | nucl-th |
Systematic analysis of hadron spectra in p+p collisions using Tsallis
distribution: Using the experimental data from the STAR, PHENIX, ALICE and CMS programs on
the rapidity and energy dependence of the $p_T$ spectra in p+p collisions, we
show that a universal distribution exists. The energy dependence of temperature
$T$ and parameter $n$ of the Tsallis distribution are also discussed in detail.
A cascade particle production mechanism in p+p collisions is proposed. | nucl-th |
Clustering effects in the $^6$Li(p,$^3$He)$^4$He reaction at
astrophysical energies: Background: The understanding of nuclear reactions between light nuclei at
energies below the Coulomb barrier is important for several astrophysical
processes, but their study poses experimental and theoretical challenges. At
sufficiently low energies, the electrons surrounding the interacting ions
affect the scattering process. Moreover, the clustered structure of some of
these nuclei may play a relevant role on the reaction observables.
Purpose: In this article, we focus on a theoretical investigation of the role
of clustered configurations of $^6$Li in reactions of astrophysical interest.
Methods: The $^6$Li(p,$^3$He)$^4$He reaction cross section is described
considering both the direct transfer of a deuteron as a single point-like
particle in Distorted Wave Born Approximation (DWBA), and the transfer of a
neutron and a proton in second-order DWBA. A number of two- and three-cluster
structure models for $^6$Li are compared.
Results: Within the two-cluster structure model, we explore the impact of the
deformed components in the $^6$Li wave-function on the reaction of interest.
Within the three-cluster structure model, we gauge the degree of $\alpha$-d
clustering and explicitly probe its role on specific features of the reaction
cross section. We compare the energy trend of the astrophysical $S$ factor
deduced in each case.
Conclusions: Clustered $^6$Li configurations lead in general to a significant
enhancement of the astrophysical factor in the energy region under study. This
effect only originates from clustering, whereas static deformations of the
ground-state configuration play a negligible role at very low energies. | nucl-th |
A Chiral Mean-Field Equation-of-State in UrQMD: Effects on the Heavy Ion
Compression Stage: It is shown that the initial compression in central heavy ion collisions at
beam energies of $E_\mathrm{lab}=1-10A$~GeV depends dominantly on the
underlying equation of state and only marginally on the model used for the
dynamical description. To do so, a procedure to incorporate any equation of
state in the UrQMD transport model is introduced. In particular we compare the
baryon density, temperature and pressure evolution as well as produced entropy
in a relativistic ideal hydrodynamics approach and the UrQMD transport model,
where the same equation of state is used in both approaches. Not only is the
compression similar if the same equation of state is used in either dynamical
model, but it also strongly depends on the actual equation of state. These
results indicate that the equation of state can be studied with observables
which are sensitive to the initial compression phase and maximum compression
achieved in heavy ion collisions at these beam energies. | nucl-th |
Generalized entropy and temperature in nuclear multifragmentation: In the framework of a 2D Vlasov model, we study the time evolution of the
"coarse-grained" Generalized Entropy (GE) in a nuclear system which undergoes a
multifragmentation (MF) phase transition. We investigate the GE both for the
gas and the fragments (surface and bulk part respectively). We find that the
formation of the surface causes the growth of the GE during the process of
fragmentation. This quantity then characterizes the MF and confirms the crucial
role of deterministic chaos in filling the new available phase-space: at
variance with the exact time evolution, no entropy change is found when the
linear response is applied. Numerical simulations were used also to extract
information about final temperatures of the fragments. From a fitting of the
momentum distribution with a Fermi-Dirac function we extract the temperature of
the fragments at the end of the process. We calculate also the gas temperature
by averaging over the available phase space. The latter is a few times larger
than the former, indicating a gas not in equilibrium. Though the model is very
schematic, this fact seems to be very general and could explain the discrepancy
found in experimental data when using the slope of light particles spectra
instead of the double ratio of isotope yields method in order to extract the
nuclear caloric curve. | nucl-th |
Application of the coherent density fluctuation model to study the
nuclear matter properties of finite nuclei within the relativistic mean-field
formalism: We obtained a density-dependent analytical expression of binding energy per
nucleon for different neutron-proton asymmetry of the nuclear matter (NM) with
a polynomial fitting, which manifests the results of effective field theory
motivated relativistic mean-field (E-RMF) model. This expression has the edge
over the Br$\ddot{u}$ckner energy density functional [Phys. Rev. {\bf 171},
1188 (1968)] since it resolves the Coster-Band problem. The NM parameters like
incompressibility, neutron pressure, symmetry energy, and its derivatives are
calculated using the acquired expression of energy per nucleon. Further, the
weight function calculated by E-RMF densities are folded with calculated NM
parameters within coherent density fluctuation model to find the properties of
closed/semi-closed-shell even-even $^{16}$O, $^{40}$Ca, $^{48}$Ca, $^{56}$Ni,
$^{90}$Zr, $^{116}$Sn, and $^{208}$Pb nuclei. The values obtained for the
neutron pressure $P^{A}$, symmetry energy $S^{A}$ and its derivative
$L_{sym}^A$ known as slope parameter, lie within a narrow domain whereas there
is a large variation in isoscalar incompressibility $K^{A}$ and surface
incompressibility $K_{sym}^{A}$ while moving from light to heavy nuclei. The
sizable variation in $K^{A}$ and $K_{sym}^{A}$ for light and heavy nuclei
depicts their structural dependence due to the peculiar density distribution of
each nucleus. A comparison of surface quantities calculated in the present work
has also been made with ones obtained via Br$\ddot{u}$ckner energy density
functional. | nucl-th |
Theoretical analysis of $^8$Li + $^{208}$Pb reaction and the critical
angular momentum for complete fusion: In a theoretical approach, the complete and incomplete fusions are
investigated by considering the $^8$Li+$^{208}$Pb reaction. By decreasing the
projectile ground-state binding energy $\varepsilon_b$ from its known
experimental value, the complete fusion is shown to have insignificant
dependence on such variations, whereas the incomplete fusion strongly depends
on that. The complete and incomplete fusion cross sections are calculated by
using a combination of both continuum-discretized coupled-channel and sum-rule
models. To this end, an incident-energy dependent cut-off angular momentum
$L_c$ is first obtained by using the available complete fusion experimental
data, within an approach which is extended to model results obtained for other
incident-energies. An approximated fitted expression linking $L_c$ to the
well-known critical value $L_{\rm crit}$ derived by Wilczy\'nski [Nucl. Phys. A
216 (1973) 386] suggests a generalization of the corresponding sum-rule model
to energies around and below the Coulomb barrier. | nucl-th |
Pseudo-Spin Symmetry and its Applications: The pseudo-spin symmetry is reviewed. A mapping that produces the separation
of the total angular momentum into pseudo-orbital and pseudo-spin degrees of
freedom is discussed, together with the analytic transformations that take us
from the normal parity space to the eigenstates of a pseudo-oscillator with one
quanta less. The many-particle version of the unitary transformation to the
pseudo-SU(3) space is established. As an example, these symmetries are used to
describe the double beta decay phenomenon in heavy deformed nuclei. | nucl-th |
Cronin effect from backward to forward rapidity: I discuss recent experimental data on the Cronin effect in deuteron-gold
collisions at the top RHIC energy, in a pseudorapidity range [-2,3]. Two
theoretical approaches are compared and contrasted: the pQCD-based
Glauber-Eikonal model and Colour Glass Condensate models. Neither can describe
the Cronin effect over the whole pseudorapidity interval up to now explored
experimentally, its most mysterious and intriguing part being at negative
rapidity. | nucl-th |
Covariant kinetic freeze out description through a finite space-time
layer: We develop and analyze a covariant FO probability valid for a finite
space-time layer. | nucl-th |
Neutron star mass formula with nuclear saturation parameters for
asymmetric nuclear matter: Low-mass neutron stars are directly associated with the nuclear saturation
parameters because their central density is definitely low. We have already
found a suitable combination of nuclear saturation parameters for expressing
the neutron star mass and gravitational redshift, i.e., $\eta\equiv
(K_0L^2)^{1/3}$ with the incompressibility for symmetric nuclear matter, $K_0$,
and the density-dependent nuclear symmetry energy, $L$. In this study, we newly
find another suitable combination given by $\eta_\tau\equiv (-K_\tau
L^5)^{1/6}$ with the isospin dependence of incompressibility for asymmetric
nuclear matter, $K_\tau$, and derive the empirical relations for the neutron
star mass and gravitational redshift as a function of $\eta_\tau$ and the
normalized central number density. With these empirical relations, one can
evaluate the mass and gravitational redshift of the neutron star, whose central
number density is less than threefold the saturation density, within $\sim
10\%$ accuracy, and the radius within a few \% accuracies. In addition, we
discuss the neutron star mass and radius constraints from the terrestrial
experiments, using the empirical relations, together with those from the
astronomical observations. Furthermore, we find a tight correlation between
$\eta_\tau$ and $\eta$. With this correlation, we derive the constraint on
$K_\tau$ as $-348\le K_\tau\le -237$ MeV, assuming that $L=60\pm 20$ and
$K_0=240\pm 20$ MeV. | nucl-th |
Role of magnetic fields on the outer crust in a magnetar: We explore the properties of 4110 nuclides from Z = 5 to Z = 82 with the
Sky3D code and the composition of the outer crust in the magnetars under
extreme magnetic fields. The effects of the variation of the nuclear masses due
to the magnetic fields on the outer crust are comprehensively studied. The
neutron-drip transition pressure, the equation of state and neutron fraction in
the outer crust have also been discussed. | nucl-th |
Multipole expansion of densities in the deformed relativistic
Hartree-Bogoliubov theory in continuum: The deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) has
been proved one of the best models to probe the exotic structures in deformed
nuclei. In DRHBc, the potentials and densities are expressed in terms of the
multipole expansion with Legendre polynomials, the dependence on which has only
been touched for light nuclei so far. In this paper, taking a light nucleus
$^{20}$Ne and a heavy nucleus $^{242}$U as examples, we investigated the
dependence on the multipole expansion of the potentials and densities in DRHBc.
It is shown that the total energy converges well with the expansion truncation
both in the absence of and presence of the pairing correlation, either in the
ground state or at a constrained quadrupole deformation. It is found that to
reach a same accuracy of the total energy, even to a same relative accuracy by
percent, a larger truncation is required by a heavy nucleus than a light one.
The dependence of the total energy on the truncation increases with
deformation. By decompositions of the neutron density distribution, it is shown
that a higher-order component has a smaller contribution. With the increase of
deformation, the high-order components get larger, while at the same
deformation, the high-order components of a heavy nucleus play a more important
role than that of a light one. | nucl-th |
Coupled-channel continuum eigenchannel basis: The goal of this paper is to calculate bound, resonant and scattering states
in the coupled-channel formalism without relying on the boundary conditions at
large distances. The coupled-channel solution is expanded in eigenchannel bases
i.e. in eigenfunctions of diagonal Hamiltonians. Each eigenchannel basis may
include discrete and discretized continuum (real or complex energy) single
particle states. The coupled-channel solutions are computed through
diagonalization in these bases. The method is applied to a few two-channels
problems. The exact bound spectrum of the Poeschl-Teller potential is well
described by using a basis of real energy continuum states. For deuteron
described by Reid potential, the experimental energy and the S and D contents
of the wave function are reproduced in the asymptotic limit of the cutoff
energy. For the Noro-Taylor potential resonant state energy is well reproduced
by using the complex energy Berggren basis. It is found that the expansion of
the coupled-channel wave function in these eigenchannel bases require less
computational efforts than the use of any other basis. The solutions are stable
and converge as the cutoff energy increases. | nucl-th |
Description of resonant states in the shell model: A technique for describing scattering states within the nuclear shell model
is proposed. This technique is applied to scattering of nucleons by $\alpha$
particles based on ab initio No-Core Shell Model calculations of $^5$He and
$^5$Li nuclei with JISP16 NN interaction. | nucl-th |
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