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Non-flow effects in three-particle mixed-harmonic azimuthal correlations
in small collision systems: The Multi-particle technique has been used to unravel the nature of the
long-range collectivity in small collision systems. A large three-particle
mixed-harmonic correlation signal was recently observed by the ATLAS
Collaboration, but the role of non-flow correlations is not yet studied. We
estimate the influence of non-flow correlations to the three-particle
correlators in $pp$ and $p$+Pb collisions using PYTHIA and HIJING models, and
compare with the ATLAS results. The large non-flow effects from the jet and
dijet production is found to be largely suppressed in $p$+Pb collisions using
the subevent cumulant method by calculating the azimuthal correlation between
two or more longitudinal pseudorapidity ranges. Depending on the experimental
subevent method, however, the non-flow effects may still be significant in $pp$
collisions. | nucl-th |
Spectrum of resonance states in $^6$He. Experimental and theoretical
analysis: We explore the structure of resonance states in $^{6}$He by experimental and
theoretical methods. We present the results of experimental investigations of
the three-body continuous spectrum of $^{6}$He. For this aim, we use the
reaction $^{3}$H$( \alpha,p\alpha)nn$, which is induced by the interaction of
alpha-particles with a triton at the beam energy $E_{\alpha} =$~67.2 MeV. The
theoretical analysis of the resonance structure in $^{6}$He is carried out
within the framework of a three-cluster microscopic model. The model exploits
the hyperspherical harmonics to describe the intercluster dynamics. The set of
new resonance states is discovered by the experimental and theoretical methods.
The energy, width, and dominant decay channels of resonances are determined.The
obtained results are compared in detail with the results of different
theoretical models and experiments as well. | nucl-th |
J/ψ$ Gluonic Dissociation Revisited : III. Effects of Transverse
Hydrodynamic Flow: In a recent paper [Eur. Phys. J {\bf C 44}, 567 (2005)] we developed a very
general formulation to take into account explicitly the effects of hydrodynamic
flow profile on the gluonic breakup of $J/\psi$'s produced in an equilibrating
quark-gluon plasma. Here we apply that formulation to the case when the medium
is undergoing cylindrically symmetric {\it transverse} expansion starting from
RHIC or LHC initial conditions. Our algebraic and numerical estimates
demonstrate that the transverse expansion causes enhancement of local gluon
number density $\ng$, affects the $\pt$-dependence of the average dissociation
rate $\tilg$ through a partial-wave interference mechanism, and makes the
survival probability $\spt$ to change with $\pt$ very slowly. Compared to the
previous case of longitudinal expansion the new graph of $\spt$ is pushed up at
LHC, but develops a rich structure at RHIC, due to a competition between the
transverse catch-up time and plasma lifetime. | nucl-th |
Structural Properties of Finite and Infinite Nuclear Systems and Related
Phenomena: In the present thesis, we have carried a thorough investigation of nuclear
structure properties. We start our investigation from the study of the magic
property of nucleus in the super -heavy region. We know the magic combination
of proton and neutron in the light and medium heavy region. But in the
super-heavy region, it is still unclear. We applied SEI (simple effective
interaction ) and RMF (relativistic mean field ) formalism with a different
parameter sets to predict the magic combinations and it turned out Z=114, 120,
126 with N=184. We have also studied theisoscalar giant monopole resonance
energy of nucleus of Z=114, 120,126, with scaling and constrained method using
RETF formalism. Isoscalar giant monopole resonance (ISGMR) is also known as the
breathing mode. We have a developed a new constrained type calculation for the
ISGMR and IVGDR. Effects of delta meson on the neutron system also discuses
extensively. | nucl-th |
A stabilized pairing functional: We propose a modified pairing functional for nuclear structure calculations
which avoids the abrupt phase transition between pairing and non-pairing
states. The intended application is the description of nuclear collective
motion where the smoothing of the transition is compulsory to remove
singularities. The stabilized pairing functional allows a thoroughly
variational formulation, unlike the Lipkin-Nogami (LN) scheme which is often
used for the purpose of smoothing. First applications to nuclear ground states
and collective excitations prove the reliability and efficiency of the proposed
stabilized pairing. | nucl-th |
The Narrowing of Charge Balance Function and Hadronization Time in
Relativistic Heavy Ion Collisions: The widths of charge balance function in high energy hadron-hadron and
relativistic heavy ion collisions are studied using the Monte Carlo generators
PYTHIA and AMPT, respectively. The narrowing of balance function as the
increase of multiplicity is found in both cases. The mean parton-freeze-out
time of a heavy-ion-collision event is used as the characteristic hadronization
time of the event. It turns out that for a fixed multiplicity interval the
width of balance function is consistent with being independent of hadronization
time. | nucl-th |
Mass dependence of short-range correlations in nuclei and the EMC effect: An approximate method to quantify the mass dependence of the number of
two-nucleon (2N) short-range correlations (SRC) in nuclei is suggested. The
proposed method relies on the concept of the "local nuclear character" of the
SRC. We quantify the SRC and its mass dependence by computing the number of
independent-particle model (IPM) nucleon pairs in a zero relative orbital
momentum state. We find that the relative probability per nucleon for 2N SRC
follows a power law as a function of the mass number $A$. The predictions are
connected to measurements which provide access to the mass dependence of SRC.
First, the ratio of the inclusive inelastic electron scattering cross sections
of nuclei to $^{2}$H at large values of the Bjorken variable. Second, the EMC
effect, for which we find a linear relationship between its magnitude and the
predicted number of SRC-prone pairs. | nucl-th |
Study of the neutron and proton capture reactions 10,11b(n, g), 11b(p,
g), 14c(p, g), and 15n(p, g) at thermal and astrophysical energies: We have studied the neutron-capture reactions 10,11B(n, g) and the role of
the 11B(n, g) reaction in seeding r-process nucleosynthesis. The possibility of
the description of the available experimental data for cross sections of the
neutron capture reaction on 10B at thermal and astrophysical energies, taking
into account the resonance at 475 keV, was considered within the framework of
the modified potential cluster model (MPCM) with forbidden states and
accounting for the resonance behavior of the scattering phase shifts. In the
framework of the same model the possibility of describing the available
experimental data for the total cross sections of the neutron radiative capture
on 11B at thermal and astrophysical energies were considered with taking into
account the 21 and 430 keV resonances. Description of the available
experimental data on the total cross sections and astrophysical S-factor of the
radiative proton capture on 11B to the ground state of 12C was treated at
astrophysical energies. The possibility of description of the experimental data
for the astrophysical S-factor of the radiative proton capture on 14C to the
ground state of 15N at astrophysical energies, and the radiative proton capture
on 15N at the energies from 50 to 1500 keV was considered in the framework of
the MPCM with the classification of the orbital states according to Young
tableaux. It was shown that, on the basis of the M1 and the E1 transitions from
different states of the p15N scattering to the ground state of 16O in the p15N
channel, it is quite succeed to explain general behavior of the S-factor in the
considered energy range in the presence of two resonances. | nucl-th |
Kinematic Moment of Inertia of e-e Rare Earths Nuclei: The kinematic moment of inertia of the rare earth even-even nuclei was
calculated using three parametric energy based expression. The plot of
kinematic moment of inertia versus nuclear spin shows a better sensitivity to
back bending than energy plot. | nucl-th |
Effect of revised $R_n$ measurements on extended Gari-Krumpelmann model
fits to nucleon electromagnetic form factors: The extended Gari-Krumpelmann (GK) model of nucleon electromagnetic form
factors, in which the $\rho$, $\rho'$, $\omega$, $\omega'$ and $\phi$ vector
meson pole contributions evolve at high momentum transfer to conform to the
predictions of perturbative QCD (pQCD), was recently shown to provide a very
good overall fit to all the nucleon electromagnetic form factor (emff) data,
including the preliminary $R_p$ and $R_n$ polarization data available in 2002,
but excluding the older $G_{Ep}$ and $G_{En}$ differential cross section data
that was inconsistent with the $R_p$ and $R_n$ data. The recently published
final version of the polarization data of the electric to magnetic ratio $R_p$
differs little from the preliminary values for the former, but the new values
of $R_n$ are midway between the preliminary values and those inferred from the
differential cross section data and the Rosenbluth separation. A new fit of the
parameters of the same model has been made with the final $R_p$ and $R_n$ data
replacing the preliminary values and the addition of some new $R_n$ and
$G_{Mn}$ data. Again there is a good fit to all the data when excluding the
differentialcross section data that is inconsistent with the polarization data.
This includes a very good fit of the $R_p$ data, which was not possible when
the differential cross section $G_(En)$ data was used in place of the
polarization $R_n$ data. Thus the change between the preliminary and final
$R_n$ data, while substantial, has not impeded the good simultaneous fit to the
neutron and proton data. The parameters, fit to the data and predictions of the
new model are compared to those of the previous models. Low momentum structures
that appear in some data analyses are partially reproduced by the model. | nucl-th |
A New Renormalization Group for Hamiltonian Field Theory: The Schrodinger equation with a two-dimensional delta-function potential is a
simple example of an asymptotically free theory that undergoes dimensional
transmutation. Renormalization requires the introduction of a mass scale, which
can be lowered perturbatively until an infrared cutoff produced by
non-perturbative effects such as bound state formation is encountered. We
outline the effective field theory and similarity renormalization group
techniques for producing renormalized cutoff hamiltonians, and illustrate the
control of logarithmic and inverse-power-law errors both techniques provide. | nucl-th |
Nuclear collective excitations using correlated realistic interactions:
the role of explicit RPA correlations: We examine to which extent correlated realistic nucleon-nucleon interactions,
derived within the Unitary Correlation Operator Method (UCOM), can describe
nuclear collective motion in the framework of first-order random-phase
approximation (RPA). To this end we employ the correlated Argonne V18
interaction in calculations within the so-called "Extended" RPA (ERPA) and
investigate the response of closed-shell nuclei. The ERPA is a renormalized RPA
version which considers explicitly the depletion of the Fermi sea due to
long-range correlations and thus allows us to examine how these affect the
excitation spectra. It is found that the effect on the properties of giant
resonances is rather small. Compared to the standard RPA, where excitations are
built on top of the uncorrelated Hartree-Fock (HF) ground state, their centroid
energies decrease by up to 1 MeV, approximately, in the isovector channel. The
isoscalar response is less affected in general. Thus, the disagreement between
our previous UCOM-based RPA calculations and the experimental data are to be
attributed to other effects, mainly to a residual three-body force and
higher-order configurations. Ground-state properties obtained within the ERPA
are compared with corresponding HF and perturbation-theory results and are
discussed as well. The ERPA formalism is presented in detail. | nucl-th |
The Maximum Lifetime of the Quark-Gluon Plasma: The width $\Delta T$ of the deconfinement transition region is shown to
influence strongly the flow structure in the (Landau-) hydrodynamical expansion
of a quark-gluon plasma. For a sharp first order transition ($\Delta T=0$) the
mixed phase is rather long-lived, with a lifetime that has a maximum when the
initial energy density is at the phase boundary between mixed and pure
quark-gluon matter. For increasing $\Delta T$, however, the lifetime decreases
rapidly. Hadronic matter, however, remains long-lived as a consequence of the
rapid change in the degrees of freedom in the transition region and the
corresponding ``softening'' of the equation of state. | nucl-th |
A Poincaré-covariant current operator for interacting systems and
deuteron electromagnetic form factors: In front-form dynamics a current operator for systems of interacting
particles, which fulfills Poincar\'e, parity and time reversal covariance,
together with hermiticity, can be defined. The electromagnetic form factors can
be extracted without any ambiguity and in the elastic case the continuity
equation is automatically satisfied. Applications to the calculation of
deuteron form factors are presented, and the effects of different
nucleon-nucleon interactions, as well as of different nucleon form factors are
investigated. | nucl-th |
Neutral Meson Photoproduction in $SU_f(3)$ $χ$PT: We present the results for the electric dipole amplitude for $\gamma N \to
\pi^0 N$ at threshold at the $O(p^2)$ level in SU$_f$(3) chiral perturbation
theory. We find that the SU$_f$(3) results differ only slightly from the
SU$_f$(2) results. At the $O(p^3)$ level one encounters new, unknown
counterterms to fix which one is likely to need the threshold photoproduction
data themselves, thus losing predictive power. We suggest, instead, that the
{\it difference} between the proton and neutron $\pi^0$ photoproduction
amplitudes may provide a test of the convergence properties of the $\chi$PT in
the present context. We urge that the neutron's electric dipole amplitude be
measured. | nucl-th |
Structure of low-lying quadrupole states in nuclei near 132Sn: The properties of the low-lying 2^+ states in the even-even nuclei around
132Sn are studied within the quasiparticle random phase approximation. Starting
from a Skyrme interaction in the particle-hole channel and a density-dependent
zero-range interaction in the particle-particle channel, we use the finite rank
separable approach in our investigation. It is found that the fourth 2^+ state
in 132Te could be a good candidate for a mixed-symmetry state. | nucl-th |
Quantum field theoretic model of metastable resonant spin-singlet state
of the np pair: The np pair in the spin-singlet state is treated as a Cooper np-pair within
the extension of the Nambu-Jona-Lasinio model of light nuclei, describing the
deuteron as a Cooper np-pair in the spin-triplet state. For the Cooper np-pair
in the spin-singlet state we compute the binding energy and express the S-wave
scattering length of np scattering in the spin-singlet state in terms of the
binding energy. The theoretical value of the S-wave scattering length of np
scattering agrees well with the experimental data. | nucl-th |
The chiral restored quark stars can exist in the universe: In this paper, the equation of state (EOS) of deconfined quark stars is
studied in the framework of the two-flavor NJL model, and the self-consistent
mean field approximation is employed by introducing a parameter $\alpha$
combining the original Lagrangian and the Fierz-transformed Lagrangian,
$\mathcal{L}_R= (1-\alpha)\mathcal{L}+\alpha\mathcal{L}_F$, to measure the
weights of different interaction channels. It is believed that the
deconfinement of phase transition happens along with the chiral phase
transition. Thus, due to the lack of description of confinement in the NJL
model, the vacuum pressure is set to confine quarks at low densities, which is
the pressure corresponding to the critical point of chiral phase transition. We
find that deconfined quark stars can reach over two-solar-mass, and the bag
constant therefore shifts from $(130 ~\mathrm{MeV})^4$ to $(150
~\mathrm{MeV})^4$ as $\alpha$ grows. In addition, the tidal deformability
$\Lambda$ is yielded ranging from 253 to 482 along with the decrease of
$~\alpha$, which satisfies the astronomical constraint of $\Lambda<800$ for
1.4-solar-mass neutron stars. | nucl-th |
Potential turning points in cluster radioactivity: Effects of various nuclear interaction potentials on the decay lifetimes and
the turning points of the WKB action integral has been studied. The microscopic
nuclear potential obtained by folding in the density distribution functions of
the two clusters with a realistic effective interaction has also been used to
calculate the turning points. Half lives of alpha and ^{20}O cluster emissions
from ^{228}Th have been calculated within the superasymmetric fission model
using various phenomenological and the microscopic double folding potentials.
Calculations of half lives with the microscopic double folding potentials are
found to be in good agreement with the observed experimental data. Present
calculations put the superasymmetric fission model on a firm theoretical basis. | nucl-th |
Systematic study of high-K isomers in the midshell Gd and Dy nuclei: High-K isomers are well known in the rare-earth region and provide unique
access to the high spin structures of the nuclei. With the current interest in
the study of neutron-rich rare-earth nuclei at Radioactive Ion Beam (RIB)
facilities, we present here theoretical results of the band structures of
neutron-rich Gd and Dy nuclei, including the high K-isomers. Apart from the
already known K-isomers, we predict some more K-isomers and these are suggested
for future studies at RIB facilities. Self-consistent Deformed Hartree-Fock and
Angular Momentum Projection theories are used to get the intrinsic structures,
band-spectra and electromagnetic transitions probabilities of the ground band
as well as bands based on isomers. | nucl-th |
The properties of \bar{K} in the nuclear medium: The self-energy of the K^- meson in nuclear matter is calculated in a
self-consistent microscopic approach, using a \bar{K}N interaction obtained
from the lowest-order meson-baryon chiral Lagrangian. The effective \bar{K}N
interaction in the medium is derived by solving the coupled-channel
Bethe-Salpeter equation including Pauli blocking on the nucleons, mean-field
binding potentials for the baryons and the self-energy of the \pi and \bar{K}
mesons. The incorporation of the self-consistent {\bar K} self-energy in the
description, in addition to the Pauli blocking effects, yields a weaker
attractive in-medium {\bar K}N interaction and a \Lambda(1405) which dissolves
faster with increasing matter density, as a result of the {\bar K} spectral
function being spread out over a wide range of energies. These effects are
further magnified when the intermediate pions are dressed. | nucl-th |
Symmetry broken and restored coupled-cluster theory I. Rotational
symmetry and angular momentum: We extend coupled-cluster theory performed on top of a Slater determinant
breaking rotational symmetry to allow for the exact restoration of the angular
momentum at any truncation order. The main objective relates to the description
of near-degenerate finite quantum systems with an open-shell character. As
such, the newly developed many-body formalism offers a wealth of potential
applications and further extensions dedicated to the ab initio description of,
e.g., doubly open-shell atomic nuclei and molecule dissociation. The formalism,
which encompasses both single-reference coupled cluster theory and projected
Hartree-Fock theory as particular cases, permits the computation of usual sets
of connected diagrams while consistently incorporating static correlations
through the highly non-perturbative restoration of rotational symmetry.
Interestingly, the yrast spectroscopy of the system, i.e. the lowest energy
associated with each angular momentum, is accessed within a single calculation.
A key difficulty presently overcome relates to the necessity to handle
generalized energy {\it and} norm kernels for which naturally terminating
coupled-cluster expansions could be eventually obtained. The present work
focuses on $SU(2)$ but can be extended to any (locally) compact Lie group and
to discrete groups, such as most point groups. In particular, the formalism
will be soon generalized to $U(1)$ symmetry associated with particle number
conservation. This is relevant to Bogoliubov coupled cluster theory that was
recently formulated and applied to singly open-shell nuclei. | nucl-th |
Compton scattering off proton in the third resonance region: Compton scattering off the proton in the third resonance region is analyzed
for the first time, owing to the full combined analysis of pion- and
photo-induced reactions in a coupled-channel effective Lagrangian model with
K-matrix approximation. Two isospin $I=3/2$ resonances $D_{33}(1700)$ and
$F_{35}(1930)$ are found to be essential in the range of 1.6 - 1.8 GeV. The
recent beam asymmetry data of Compton scattering from the GRAAL facility are
used to determine the helicity couplings of these resonances, and strong
constraints are coming also from $\pi N$ and $K\Sigma$ photoproduction data.
The possible spin and parity of new narrow resonances is discussed. | nucl-th |
Influence of non-statistical properties in nuclear structure on emission
of prompt fission neutrons: The Hauser-Feshbach Fission Fragment Decay (HF$^3$D) model is extended to
calculate the prompt fission neutron spectrum (PFNS) for the thermal neutron
induced fission on $^{235}$U, where the evaporated neutrons from all possible
fission fragment pairs are aggregated. By studying model parameter
sensitivities on the calculated PFNS, as well as non-statistical behavior of
low-lying discrete level spin distribution, we conclude that discrepancies
between the aggregation calculation and the experimental PFNS seen at higher
neutron emission energies can be attributed to both the primary fission
fragment yield distribution and the possible high spin states that are not
predicted by the statistical theory of nuclear structure. | nucl-th |
Intrinsic operators for the electromagnetic nuclear current: The intrinsic electromagnetic nuclear meson exchange charge and current
operators arising from a separation of the center-of-mass motion are derived
for a one-boson-exchange model for the nuclear interaction with scalar,
pseudoscalar and vector meson exchange including leading order relativistic
terms. Explicit expressions for the meson exchange operators corresponding to
the different meson types are given in detail for a two-nucleon system. These
intrinsic operators are to be evaluated between intrinsic wave functions in
their center-of-mass frame. | nucl-th |
Three-body resonances Lambda-n-n and Lambda-Lambda-n: Possible bound and resonant states of the hypernuclear systems $\Lambda nn$
and $\Lambda\Lambda n$ are sought as zeros of the corresponding three-body Jost
functions calculated within the framework of the hyperspherical approach with
local two-body S-wave potentials describing the $nn$, $\Lambda n$, and
$\Lambda\Lambda$ interactions. Very wide near-threshold resonances are found
for both three-body systems. The positions of these resonances turned out to be
sensitive to the choice of the $\Lambda n$-potential. Bound $\Lambda nn$ and
$\Lambda\Lambda n$ states only appear if the two-body potentials are multiplied
by a factor of $\sim 1.5$. | nucl-th |
Dense nuclear matter and symmetry energy in strong magnetic fields: The properties of nuclear matter in the presence of a strong magnetic field,
including the density-dependent symmetry energy, the chemical composition and
spin polarizations, are investigated in the framework of the relativistic mean
field models FSU-Gold. The anomalous magnetic moments (AMM) of the particles
and the nonlinear isoscalar-isovector coupling are included. It is found that
the parabolic isospin-dependence of the energy per nucleon of asymmetric
nuclear matter remains valid for values of the magnetic field below
$10^{5}B_{c}^{e}$, $B_{c}^{e}=4.414\times10^{13}$G being the electron critical
field. Accordingly, the symmetry energy can be obtained by the difference of
the energy per nucleon in pure neutron matter and that in symmetric matter. The
symmetry energy, which is enhanced by the presence of the magnetic field,
significantly affects the chemical composition and the proton polarization. The
effects of the AMM of each component on the energy per nucleon, symmetry
energy, chemical composition and spin polarization are discussed in detail. | nucl-th |
Magicity of the $^{52}$Ca and $^{54}$Ca isotopes and tensor contribution
within a mean--field approach: We investigate the magicity of the isotopes $^{52}$Ca and $^{54}$Ca, that was
recently confirmed by two experimental measurements, and relate it to
like--particle and neutron--proton tensor effects within a mean--field
description. By analyzing Ca isotopes, we show that the like--particle tensor
contribution induces shell effects that render these nuclei more magic than
they would be predicted by neglecting it. In particular, such induced shell
effects are stronger in the nucleus $^{52}$Ca and the single--particle gaps are
increased in both isotopes due to the tensor force. By studying $N=32$ and
$N=34$ isotones, neutron--proton tensor effects may be isolated and their role
analyzed. It is shown that neutron--proton tensor effects lead to increasing
$N=32$ and $N=34$ gaps, when going along isotonic chains, from $^{58}$Fe to
$^{52}$Ca, and from $^{60}$Fe to $^{54}$Ca, respectively.
The mean--field calculations are perfomed by employing one Skyrme parameter
set, that was introduced in a previous work by fitting the tensor parameters
together with the spin--orbit strength. The signs and the values of the tensor
strengths are thus checked within this specific application. The obtained
results indicate that the employed parameter set, even if generated with a
partial adjustment of the parameters of the force, leads to the correct shell
behavior and provides, in particular, a description of the magicity of
$^{52}$Ca and $^{54}$Ca within a pure mean--field picture with the effective
two--body Skyrme interaction. | nucl-th |
The 3D structure of anisotropic flow in small collision systems at the
Relativistic Heavy Ion Collider: We present (3+1)D dynamical simulations of asymmetric nuclear collisions at
the Relativistic Heavy Ion Collider (RHIC). Employing a dynamical initial state
model coupled to (3+1)D viscous relativistic hydrodynamics, we explore the
rapidity dependence of anisotropic flow in the RHIC small system scan at 200
GeV center of mass energy. We calibrate parameters to describe central
$^3$He+Au collisions and make extrapolations to d+Au and p+Au collisions. Our
calculations demonstrate that approximately 50% of the $v_3(p_T)$ difference
between the measurements by the STAR and PHENIX Collaborations can be explained
by the use of reference flow vectors from different rapidity regions. This
emphasizes the importance of longitudinal flow decorrelation for anisotropic
flow measurements in asymmetric nuclear collisions, and the need for (3+1)D
simulations. We also present results for the beam energy dependence of particle
spectra and anisotropic flow in d+Au collisions. | nucl-th |
Four-body structure of neutron-rich hypernucleus $^6_Λ$H: The structure of heavy hyperhydrogen $^6_{\Lambda}$H is studied within the
framework of a $tnn\Lambda$ four-body cluster model. Interactions among the
constituent subunits are determined so as to reproduce reasonably well the
observed low-energy properties of the $tn, t\Lambda$ and $tnn$ subsystems. As
long as we reproduce the energy and width of $^5$H within the error bar, the
ground state of $^6_{\Lambda}$H is obtained as a resonant state. | nucl-th |
Formation of Few-Body Clusters in Nuclear Matter: Starting from a suitably modified three-body equation to include dominant
medium effects such as self energy corrections and Pauli blocking I present
results on several observables relevant for the formation of light clusters in
a heavy ion collision at moderate energies. Properly taking into account the
medium leads to the Mott effect, larger reaction rates, in turn, faster time
scales for the deuteron life time and chemical relaxation time. Within a
Boltzmann-Uehling-Uhlenbeck approach to simulate the heavy ion reactions, also
the total number of deuterons and the energy spectrum are significantly changed
due to medium effects in the elementary cross sections entering into the
collision integrals. | nucl-th |
Thermal Properties of Asymmetric Nuclear Matter: The thermal properties of asymmetric nuclear matter are investigated in a
relativistic mean- field approach. We start from free space NN-interactions and
derive in-medium self-energies by Dirac-Brueckner theory. By the DDRH procedure
we derive in a self-consistent approach density- dependent meson-baryon
vertices. At the mean-field level, we include isoscalar and isovector scalar
and vector interactions. The nuclear equation of state is investigated for a
large range of total baryon densities up to the neutron star regime, the full
range of asymmetries from symmetric nuclear matter to pure neutron matter, and
temperatures up to T~100 MeV. The isovector-scalar self-energies are found to
modify strongly the thermal properties of asymmetric nuclear matter. A striking
result is the change of phase transitions when isovector-scalar self-energies
are included. | nucl-th |
Modification of magicity towards the dripline and its impact on
electron-capture rates for stellar core-collapse: The importance of microphysical inputs from laboratory nuclear experiments
and theoretical nuclear structure calculations in the understanding of the core
collapse dynamics, and the subsequent supernova explosion, is largely
recognized in the recent literature. In this work, we analyze the impact of the
masses of very neutron rich nuclei on the matter composition during collapse,
and the corresponding electron capture rate. To this aim, we introduce an
empirical modification of the popular Duflo-Zuker mass model to account for
possible shell quenching far from stability, and study the effect of the
quenching on the average electron capture rate. We show that the preeminence of
the $N=50$ and $N=82$ closed shells in the collapse dynamics is considerably
decreased if the shell gaps are reduced in the region of $^{78}$Ni and beyond.
As a consequence, local modifications of the overall electron capture rate up
to 30\% can be expected, with integrated values strongly dependent on the
stiffness of magicity quenching and progenitor mass and potential important
consequences on the entropy generation, the neutrino emissivity, and the mass
of the core at bounce. Our work underlines the importance of new experimental
measurements in this region of the nuclear chart, the most crucial information
being the nuclear mass and the Gamow-Teller strength. Reliable microscopic
calculations of the associated elementary rate, in a wide range of temperatures
and electron densities, optimized on these new empirical information, will be
additionally needed to get quantitative predictions of the collapse dynamics. | nucl-th |
The Nuclear Shell Model Toward the Drip Lines: We describe the "islands of inversion" that occur when approaching the
neutron drip line around the magic numbers N=20, N=28 and N=40 in the framework
of the Interacting Shell Model in very large valence spaces. We explain these
configuration inversions (and the associated shape transitions) as the result
of the competition between the spherical mean field (monopole) which favors
magicity and the correlations (multipole) which favor deformed intruder states.
We also show that the N=20 and N=28 islands are in reallity a single one, which
for the Magnesium isotopes is limited by N=18 and N=32. | nucl-th |
Isospin breaking in the reaction np --> dpi^0 at threshold: The model for charge symmetry breaking in the reaction np --> dpi^0 applied
earlier around the Delta region is used to calculate the integrated
forward-backward asymmetry of the cross section close to threshold. The mixing
of the pi and eta mesons appears as strongly dominant at these energies. This
contrasts elastic np scattering experiments, where the np mass difference in
OPE dominates, or np --> d\pi^0 closer to the Delta region. | nucl-th |
Invariant amplitudes for coherent electromagnetic pseudoscalar
production from a spin-one target (II): crossing, multipoles and observables: The formal properties of the recently derived set of linearly independent
invariant amplitudes for the electromagnetic production of a pseudoscalar
particle from a spin-one particle have been further exploited. The crossing
properties are discussed in detail. Since not all of the amplitudes have simple
crossing behaviour, we introduce an alternative set of basic amplitudes which
are either symmetric or antisymmetric under crossing. The multipole
decomposition is given, and the representation of the multipoles as integrals
over the invariant functions weighted with Legendre polynomials is derived.
Furthermore, differential cross section and polarization observables are
expressed in terms of the corresponding invariant functions. | nucl-th |
Meson Condensation in Dense Matter Revisited: The results for meson condensation in the literature vary markedly depending
on whether one uses chiral perturbation theory or the current-algebra-plus-PCAC
approach. To elucidate the origin of this discrepancy, we re-examine the role
of the sigma-term in meson condensation. We find that the resolution of the
existing discrepancy requires a knowledge of terms in the Lagrangian that are
higher order in density than hitherto considered. | nucl-th |
Using Continuum Level Density in the Pairing Hamiltonian: BCS and Exact
Solutions: Pairing plays a central role in nuclear systems. The simplest model for the
pairing is the constant-pairing Hamiltonian. The aim of the present paper is to
include the continuum single particle level density in the constant pairing
Hamiltonian and to make a comparison between the approximate BCS and the exact
Richardson solutions. The continuum is introduced by using the continuum single
particle level density. It is shown that the continuum makes an important
contribution to the pairing parameter even in those case when the continuum is
weakly populated. It is shown that while the approximate BCS solution depends
on the model space the exact Richardson solution does not. | nucl-th |
Diabatic Mean-Field Description of Rotational Bands in Terms of the
Selfconsistent Collective Coordinate Method: Diabatic description of rotational bands provides a clear-cut picture for
understanding the back-bending phenomena, where the internal structure of the
yrast band changes dramatically as a function of angular momentum. A
microscopic framework to obtain the diabatic bands within the mean-field
approximation is presented by making use of the selfconsistent collective
coordinate method. Applying the framework, both the ground state rotational
bands and the Stockholm bands are studied systematically for the rare-earth
deformed nuclei. An overall agreement has been achieved between the calculated
and observed rotational spectra. It is also shown that the inclusion of the
double-stretched quadrupole-pairing interaction is crucial to obtain an overall
agreement for the even-odd mass differences and the rotational spectra
simultaneously. | nucl-th |
Aspects of meson properties in dense nuclear matter: We investigate the modification of meson spectral densities in dense nuclear
matter at zero temperature. These effects are studied in a fully relativistic
mean field model which goes beyond the linear density approximation and also
includes baryon resonances. In particular, the role of N*(1520) and N*(1720) on
the rho meson spectral density is highlighted. Even though the nucleon-nucleon
loop and the nucleon-resonance loop contribute with the opposite sign, an
overall reduction of rho meson mass is still observed at high density.
Importantly, it is shown that the resonances cause substantial broadening of
the rho meson spectral density in matter and also induces non-trivial momentum
dependence. The spectral density of the a0 meson is also shown. We study the
dispersion relations and collective oscillations induced by the rho meson
propagation in nuclear matter together with the influence of the mixing of rho
with the a0 meson. The relevant expression for the plasma frequency is also
recovered analytically in the appropriate limit. | nucl-th |
Quantum Monte Carlo calculations of magnetic moments and M1 transitions
in $A \le 9$ nuclei: We present Quantum Monte Carlo calculations of magnetic moments and M1
transitions in $A\le 9$ nuclei which take into account contributions of
two-body electromagnetic currents. The Hamiltonian utilized to generate the
nuclear wave functions includes the realistic Argonne-{\it v}$_{18}$
two-nucleon and the Illinois-7 three-nucleon interactions. The nuclear two-body
electromagnetic currents are derived from a pionful chiral effective field
theory including up to one-loop corrections. These currents involve unknown Low
Energy Constants which have been fixed so as to reproduce a number of
experimental data for the two- and three-nucleon systems, such as $np$ phase
shifts and deuteron, triton, and $^3$He magnetic moments. This preliminary
study shows that two-body contributions provide significant corrections which
are crucial to bring the theory in agreement with the experimental data in both
magnetic moments and M1 transitions. | nucl-th |
Deformation effect on nuclear density profile and radius enhancement in
light- and medium-mass neutron-rich nuclei: Mass number dependence of the nuclear radii is closely related to the nuclear
matter properties. It is known that the most of nuclei exhibit some
deformation. We discuss how the nuclear density profile is modified by the
nuclear deformation to elucidate the enhancement mechanism of the nuclear radii
through a systematic investigation of neutron-rich Ne, Mg, Si, S, Ar, Ti, Cr,
and Fe isotopes. Skyrme-Hartree-Fock calculations are performed in a
three-dimensional Cartesian grid to describe the nuclear deformation in a
non-empirical way. The role of the nuclear deformation on the nuclear density
profiles is explored in comparison to calculations with spherical limit. We
find correlations between the nuclear deformation and the internal nuclear
density. The evolution of the nuclear radii appears to follow the core swelling
mechanism recently proposed in spherical nuclei [Phys. Rev. C 101, 061301(R)
(2020)], and the radius is further enhanced by the nuclear deformation. This
study demands further theoretical and experimental investigations for the
internal density. | nucl-th |
Ground state energy fluctuations in the Nuclear Shell Model: Statistical fluctuations of the nuclear ground state energies are estimated
using shell model calculations in which particles in the valence shells
interact through well defined forces, and are coupled to an upper shell
governed by random 2-body interactions. Induced ground-state energy
fluctuations are found to be one order of magnitude smaller than those
previously associated with chaotic components, in close agreement with
independent perturbative estimates based on the spreading widths of excited
states. | nucl-th |
Symplectic No-core Shell-model Approach to Intermediate-mass Nuclei: We present a microscopic description of nuclei in an intermediate-mass
region, including the proximity to the proton drip line, based on a no-core
shell model with a schematic many-nucleon long-range interaction with no
parameter adjustments. The outcome confirms the essential role played by the
symplectic symmetry to inform the interaction and the winnowing of shell-model
spaces. We show that it is imperative that model spaces be expanded well beyond
the current limits up through fifteen major shells to accommodate particle
excitations that appear critical to highly-deformed spatial structures and the
convergence of associated observables. | nucl-th |
J/psi production in relativistic heavy ion collisions from a multi-phase
transport model: Using A Multi-Phase Transport (AMPT) model, we study J/psi production from
interactions between charm and anti-charm quarks in initial parton phase and
between D and Dbar mesons in final hadron phase of relativistic heavy ion
collisions at the Relativistic Heavy Ion Collider (RHIC). Including also the
inverse reactions of J/psi absorption by gluons and light mesons, we find that
the net number of J/psi from the parton and hadron phases is smaller than that
expected from the superposition of initial nucleon-nucleon collisions, contrary
to the J/psi enhancement predicted by the kinetic formation model. The
production of J/psi is further suppressed if one includes the color screening
effect in the parton phase. We have also studied the dependence of J/psi
production on the charm quark mass and the effective charm meson mass. | nucl-th |
Parity-Violating Interaction Effects I: the Longitudinal Asymmetry in pp
Elastic Scattering: The proton-proton parity-violating longitudinal asymmetry is calculated in
the lab-energy range 0--350 MeV, using a number of different, latest-generation
strong-interaction potentials--Argonne V18, Bonn-2000, and Nijmegen-I--in
combination with a weak-interaction potential consisting of rho- and
omega-meson exchanges--the model known as DDH. The complete scattering problem
in the presence of parity-conserving, including Coulomb, and parity-violating
potentials is solved in both configuration- and momentum-space. The predicted
parity-violating asymmetries are found to be only weakly dependent upon the
input strong-interaction potential adopted in the calculation. Values for the
rho- and omega-meson weak coupling constants $h^{pp}_\rho$ and $h^{pp}_\omega$
are determined by reproducing the measured asymmetries at 13.6 MeV, 45 MeV, and
221 MeV. | nucl-th |
Spin-isospin response of deformed neutron-rich nuclei in a
self-consistent Skyrme energy-density-functional approach: We develop a new framework of the self-consistent deformed proton-neutron
quasiparticle-random-phase approximation (pnQRPA), formulated in the
Hartree-Fock-Bogoliubov (HFB) single-quasiparticle basis. The same Skyrme force
is used in both the HFB and pnQRPA calculations except in the proton-neutron
particle-particle channel, where an S=1 contact force is employed. Numerical
application is performed for Gamow-Teller (GT) strength distributions and
$\beta$-decay rates in the deformed neutron-rich Zr isotopes located around the
path of the rapid-neutron-capture process nucleosynthesis. It is found that the
GT strength distributions are fragmented due to deformation. Furthermore we
find that the momentum-dependent terms in the particle-hole residual
interaction leads to a stronger collectivity of the GT giant resonance. The T=0
pairing enhances the low-lying strengths cooperatively with the T=1 pairing
correlation, which shortens the $\beta$-decay half lives by at most an order of
magnitude. The new calculation scheme reproduces well the observed isotopic
dependence of the $\beta$-decay half lives of deformed $^{100-110}$Zr isotopes. | nucl-th |
Role of baryon resonances in the $π^-p \to ne^+e^-$ reaction within an
effective-Lagrangian model: We present a study of the reaction $\pi^-p \to ne^+e^-$ for
$\sqrt{s}=1.49\,\textrm{GeV}$, including non-resonant Born terms and
contributions of the $N(1440)$, $N(1520)$, $N(1535)$ resonances ($R$), using an
effective-Lagrangian model, which we extended by a phenomenological phase
factor at the $RN\rho$ vertex function. We give predictions for both the
differential cross section $d\sigma/dm$ and the spin density matrix elements of
the virtual photon that decays into the lepton pair. In the studied energy
range, the cross section is dominated by the Born and $N(1520)$ contributions. | nucl-th |
A Hartree-Bose Mean-Field Approximation for IBM-3: A Hartree-Bose mean-field approximation for the IBM-3 is presented. A
Hartree- Bose transformation from spherical to deformed bosons with
charge-dependent parameters is proposed which allows bosonic pair correlations
and includes higher angular momentum bosons. The formalism contains previously
proposed IBM-2 and IBM-3 intrinsic states as particular limits. | nucl-th |
Neutrino-induced single-pion production: Kinematics and Cross Section: In the energy range of present and future accelerator-based
neutrino-oscillation experiments, single-pion production (SPP) is one of the
main contributions to the neutrino-nucleus scattering cross section. For these
neutrino energies, ranging from several hundreds of MeV to a few GeV, the SPP
on the nucleus is usually described by the reaction in which the incoming
lepton couples to one bound nucleon in the nucleus, producing a pion and the
knock-out nucleon, along with the residual system and the scattered lepton in
the final state. Here, the kinematics and cross section formula for this
process are discussed, although the formalism can be applied to other
$2\rightarrow4$ processes. | nucl-th |
Isovector properties of quark matter and quark stars in an
isospin-dependent confining model: The confining quark matter (CQM) model, in which the confinement and
asymptotic freedom are modeled via the Richardson potential for quark-quark
vector interaction and the chiral symmetry restoration at high density is
described by the density dependent quark mass, is extended to include isospin
dependence of the quark mass. Within this extended isospin-dependent confining
quark matter (ICQM) model, we study the properties of strange quark matter and
quark stars. We find that including isospin dependence of the quark mass can
significantly influence the quark matter symmetry energy, the stability of
strange quark matter and the mass-radius relation of quark stars. In
particular, we demonstrate although the recently discovered large mass pulsars
PSR J1614.2230 and PSR J0348+0432 with masses around two times solar mass
($2M_{\odot}$) cannot be quark stars within the original CQM model, they can be
well described by quark stars in the ICQM model if the isospin dependence of
quark mass is strong enough so that the quark matter symmetry energy is about
four times that of a free quark gas. We also discuss the effects of the density
dependence of quark mass on the properties of quark stars. Our results indicate
that the heavy quark stars with mass around $2M_{\odot}$ (if exist) can put
strong constraints on isospin and density dependence of the quark mass as well
as the quark matter symmetry energy. | nucl-th |
Rearrangement in folding potentials with density-dependent
nucleon-nucleon interaction: We discuss optical potentials for the nuclear elastic scattering from a
variational viewpoint.
Density-dependence in the effective $N$-$N$ interaction leads to density
rearrangement terms, in addition to the conventional folding term.
Effects of the rearrangement on the $N$-$A$ optical potential are illustrated
in the nuclear-matter limit.
Closely relating to consistency with the saturation, the rearrangement
appreciably improves the isoscalar optical potential depth over the previous
folding model calculations.
The rearrangement gives stronger effects as the density grows.
We also present rearrangement terms in the $A$-$A$ double-folding potential.
Since the rearrangement terms are relevant to the nuclear structure but
should be handled within the reaction model,
$N$-$N$ effective interactions applicable both to structure models and to the
folding model will be desired for unambiguous description of the nuclear
elastic scattering. | nucl-th |
No-Core shell model for A = 47 and A = 49: We apply an {\it ab-initio} approach to the nuclear structure of odd-mass
nuclei straddling $^{48}Ca$. Starting with the NN interaction, that fits
two-body scattering and bound state data we evaluate the nuclear properties of
$A = 47$ and $A = 49$ nuclei in a no-core approach. Due to model space
limitations and the absence of 3-body interactions, we incorporate
phenomenological terms determined by fits to $A = 48$ nuclei in a previous
effort. Our modified Hamiltonian produces reasonable spectra for these odd mass
nuclei. In addition to the differences in single-particle basis states, the
absence of a single-particle Hamiltonian in our no-core approach obscures
direct comparisons with valence effective NN interactions. Nevertheless, we
compare the fp-shell matrix elements of our initial and modified Hamiltonians
in the harmonic oscillator basis with a recent model fp-shell interaction, the
GXPF1 interaction of Honma, Otsuka, Brown and Mizusaki. Notable differences
emerge from these comparisons. In particular, our diagonal two-body $T = 0$
matrix elements are, on average, about 800-900keV more attractive. Furthermore,
while our initial and modified NN Hamiltonian fp-shell matrix elements are
strongly correlated, there is much less correlation with the GXPF1 matrix
elements. | nucl-th |
Molecule model for kaonic nuclear cluster anti-KNN: We analyse the properties of the kaonic nuclear cluster (KNC) anti-KNN with
the structure Nx(anti-KN)_(I = 0), having the quantum numbers I(J^P) =
1/2(0^-), and treated as a quasi-bound hadronic molecule state. We describe the
properties of the hadronic molecule, or the KNC Nx(anti-KN)_(I = 0), in terms
of vibrational degrees of freedom with oscillator wave functions and chiral
dynamics. These wave functions, having the meaning of trial wave functions of
variational calculations, are parameterised by the frequency of oscillations of
the (anti-KN)_(I = 0) pair, which is fixed in terms of the binding energy of
the strange baryon resonance Lambda(1405), treated as a quasi-bound
(anti-KN)_(I = 0) state. The binding energies B_X and widths Gamma_X of the
states X = (anti-KN)_(I = 0) and X = anti-KNN, respectively, are calculated in
the heavy-baryon approximation by using chiral Lagrangians with meson-baryon
derivative couplings invariant under chiral SU(3)xSU(3) symmetry at the
tree-level approximation. The results are B_(anti-KNN) = 40.2 MeV and
Gamma_(anti-KNN) = Gamma^(non-pionic)_(anti-KNN) + Gamma^(pionic)_(anti-KNN) ~
(85 - 106) MeV and, where Gamma^(non-pionic)_(anti-KNN) ~ 21 MeV and
Gamma^(pionic)_(anti-KNN) ~ (64 - 86) MeV are the widths of non-pionic anti-KNN
-> N Lambda^0, N Sigma and pionic anti-KNN -> N Sigma pi decay modes,
calculated for B_(anti-KN) = 29 MeV and Gamma_(anti-KN) = (30 - 40) MeV,
respectively. | nucl-th |
Jet-medium interaction and conformal relativistic fluid dynamics: A formalism to study the mode-by-mode response to the energy deposition of
external hard partons propagating in a relativistic fluid is developed, based
on a semi-analytical solution of conformal fluid-dynamics. The soft particle
production resulting from the jet-medium interaction is calculated and the
recoil of the viscous medium is studied for different orientations of the
relativistic jets, and for different values of the specific shear viscosity
$\eta/s$. | nucl-th |
Correlations in ultra-relativistic nuclear collisions with strings: While string models describe initial state radiation in ultra-relativistic
nuclear collisions well, they mainly differ in their end-point positions of the
strings in spatial rapidity. We present a generic model where wounded
constituents are amended with strings whose both end-point positions fluctuate
and analyze semi-analytically various scenarios of string-end-point
fluctuations. In particular we constrain the different cases to experimental
data on rapidity spectra from collisions at $\sqrt{s_{\rm NN}}=200$~GeV, and
explore their respective two-body correlations, which allows to partially
discriminate the possible solutions. | nucl-th |
Confronting a set of Skyrme and $χ_{EFT}$ predictions for the crust
of neutron stars: With the improved accuracy of neutron star observational data, it is
necessary to derive new equation of state where the crust and the core are
consistently calculated within a unified approach. For this purpose we describe
non-uniform matter in the crust of neutron stars employing a compressible
liquid-drop model, where the bulk and the neutron fluid terms are given from
the same model as the one describing uniform matter present in the core. We
then generate a set of fifteen unified equations of state for cold catalyzed
neutron stars built on realistic modelings of the nuclear interaction, which
belongs to two main groups: the first one derives from the phenomenological
Skyrme interaction and the second one from $\chi_{EFT}$ Hamiltonians. The
confrontation of these model predictions allows us to investigate the model
dependence for the crust properties, and in particular the effect of neutron
matter at low density. The new set of unified equations of state is available
at the CompOSE repository. | nucl-th |
Multiplicity Fluctuations in Nucleus-Nucleus Collisions: Dependence on
Energy and Atomic Number: Event-by-event multiplicity fluctuations in central C+C, S+S, In+In, and
Pb+Pb as well as p+p collisions at bombarding energies from 10 to 160 AGeV are
studied within the HSD and UrQMD microscopic transport approaches. Our
investigation is directly related to the future experimental program of the
NA61 Collaboration at the SPS for a search of the QCD critical point. The
dependence on energy and atomic mass number of the scaled variances for
negative, positive, and all charged hadrons is presented and compared to the
results of the model of independent sources. Furthermore, the nucleus-nucleus
results from the transport calculations are compared to inelastic proton-proton
collisions for reference. We find a dominant role of the participant number
fluctuations in nucleus-nucleus reactions at finite impact parameter $b$. In
order to reduce the influence of the participant numbers fluctuations on the
charged particle multiplicity fluctuations only the most central events have to
be selected. Accordingly, the samples of the 1% most central nucleus-nucleus
collisions with the largest numbers of the projectile participants are studied.
The results are compared with those for collisions at zero impact parameter. A
strong influence of the centrality selection criteria on the multiplicity
fluctuations is pointed out. Our findings are essential for an optimal choice
of colliding nuclei and bombarding energies for the experimental search of the
QCD critical point. | nucl-th |
The black hole spin influence on accretion disk neutrino detection: Neutrinos are copiously emitted from black hole accretion disks playing a
fundamental role in their evolution, as well as in the production of gamma ray
bursts and r-process nucleosynthesis. The black hole generates a strong
gravitational field able to change the properties of the emerging neutrinos. We
study the influence of the black hole spin on the structure of the neutrino
surfaces, neutrino luminosities, average neutrino energies, and event counts at
SuperK. We consider several disk models and provide estimates that cover
different black hole efficiency scenarios. We discuss the influence of the
detector's inclination with respect to the axis of the torus on neutrino
properties. We find that tori around spinning black holes have larger
luminosities, energies and rates compared to tori around static black holes,
and that the inclination of the observer causes a reduction in the luminosities
and detection rates but an increase in the average energies. | nucl-th |
Nuclear transparency in quasielastic A(e,e'p): intranuclear cascade
versus eikonal approximation: The problem of nuclear propagation through the nuclear medium in quasielastic
A(e,e'p) reactions is discussed in the kinematic range 1<Q^2<7 (GeV/c)^2. The
coefficient of nuclear transparency is calculated for each Q^2 in the framework
of the intranuclear cascade model (INC) and of the eikonal approximation (EA).
The predictions of both models are in good agreement with each other and with
experimental data recently obtained at SLAC, BATES and TJNAF. The EA gives an
explanation of the Q^2 behaviour of the transparency coefficient as a kinematic
effect related to the superposition of contributions from each target shell. | nucl-th |
Analysis of resonance multipoles from polarization observables in eta
photoproduction: A combined analysis of new eta photoproduction data for total and
differential cross sections, target asymmetry and photon asymmetry is
presented. Using a few reasonable assumptions we perform the first
model-independent analysis of the E0+, E2- and M2- eta photoproduction
multipoles. Making use of the well-known A3/2 helicity amplitude of the
D13(1520) state we extract its branching ratio to the eta-N channel,
Gamma(eta,N)/Gamma = (0.08 +- 0.01)%. At higher energies, we show that the
photon asymmetry is extremely sensitive to small multipoles that are excited by
photons in the helicity 3/2 state. The new GRAAL photon asymmetry data at
higher energy show a clear signal of the F15(1680) excitation which permits
extracting an F15(1680)->eta,N branching ratio of (0.15 +0.35 -0.10)%. | nucl-th |
Ab initio many-body calculations of nucleon-nucleus scattering: We develop a new ab initio many-body approach capable of describing
simultaneously both bound and scattering states in light nuclei, by combining
the resonating-group method with the use of realistic interactions, and a
microscopic and consistent description of the nucleon clusters. This approach
preserves translational symmetry and Pauli principle. We outline technical
details and present phase shift results for neutron scattering on 3H, 4He and
10Be and proton scattering on 3He and 4He, using realistic nucleon-nucleon (NN)
potentials. Our A=4 scattering results are compared to earlier ab initio
calculations. We find that the CD-Bonn NN potential in particular provides an
excellent description of nucleon-4He S-wave phase shifts. On the contrary, the
experimental nucleon-4He P-wave phase shifts are not well reproduced by any NN
potential we use. We demonstrate that a proper treatment of the coupling to the
n-10Be continuum is successful in explaining the parity-inverted ground state
in 11Be. | nucl-th |
The neutron distribution in nuclei as measured with parity violating
electron scattering: A short review of the present knowledge of the nucleons distribution in
nuclei is given. A proposal is made about a possible measurements of the
neutron distribution through polarized electron scattering off nuclei. | nucl-th |
Neutrino-Neutron Scattering Opacities in Supernova Matter: We compute the static density and spin structure factors in the long
wavelength limit for pure neutron matter at subsaturation densities relevant to
core-collapse supernovae within the Brueckner-Hartree-Fock (BHF) approach. The
BHF results are reliable at high densities, extending beyond the validity of
the virial expansion. Motivated by the similarities between the dilute neutron
gas and a unitary gas, we propose a phenomenological approach to derive the
static structures with finite momentum transfer as well as the dynamic ones
with simple analytical expressions, based on the computed static structures in
the long wavelength limit. We also compare the in-medium neutrino-neutron
scattering cross sections using different structure factors. Our study
emphasizes the importance of accurately computing the static structure factors
theoretically and utilizing the full dynamic structure factors in core-collapse
supernova simulations. | nucl-th |
Relativistic second order dissipative hydrodynamics from effective
fugacity quasi particle model: In this work a second order relativistic viscous hydrodynamic model has been
presented based on the effective fugacity quasi-particle model (EQPM). The
hydro model has been derived from the effective relativistic second-order
transport equation under EQPM for a multi-particle (two component) system and
solving it in Grad's 14 moment method. The EQPM model describes the strongly
interacting thermal system of QCD interactions through its fugacity parameters
extracted from an updated lattice equations of state. The proper time evolution
of temperature and pressure anisotropy is observed to be affected significantly
due to the inclusion of EQPM model compared to an ideal system. | nucl-th |
Flavor content of nucleon form factors in the space- and time-like
region: I discuss a two-component model of nucleon form factors in which the external
photon couples both to an intrinsic three-quark structure and to a meson cloud
via vector-meson dominance, and present a simultaneous analysis of the
electromagnetic form factors of the nucleon in the space- and time-like regions
as well as their strangeness content. | nucl-th |
Near-threshold pion production with radioactive beams at the Rare
Isotope Accelerator: Using an isospin- and momentum-dependent transport model we study
near-threshold pion production in heavy-ion collisions induced by radioactive
beams at the planned Rare Isotope Accelerator (RIA). We revisit the question of
probing the high density behavior of nuclear symmetry energy $E_{sym}(\rho)$
using the $\pi^-/\pi^+$ ratio. It is found that both the total and differential
$\pi^-/\pi^+$ ratios remain sensitive to the $E_{sym}(\rho)$ when the
momentum-dependence of both the isoscalar and isovector potentials are
consistently taken into account. Moreover, the multiplicity and spectrum of
$\pi^-$ mesons are found more sensitive to the $E_{sym}(\rho)$ than those of
$\pi^+$ mesons. Finally, effects of the Coulomb potential on the pion spectra
and $\pi^-/\pi^+$ ratio are also discussed. | nucl-th |
Shell-model description of monopole shift in neutron-rich Cu: Variations in the nuclear mean-field, in neutron-rich nuclei, are
investigated within the framework of the nuclear shell model. The change is
identified to originate mainly from the monopole part of the effective two-body
proton-neutron interaction. Applications for the low-lying states in odd-$A$ Cu
nuclei are presented. We compare the results using both schematic and realistic
forces. We also compare the monopole shifts with the results obtained from
large-scale shell-model calculations, using the same realistic interaction, in
order to study two-body correlations beyond the proton mean-field variations. | nucl-th |
Parity Violation in Low-Energy np->d gamma and the Deuteron Anapole
Moment: Parity violation in low-energy nuclear observables is included in the
pionless effective field theory. The model-independent relation between the
parity-violating asymmetry in polarized np -> d gamma and the non-nucleon part
of the deuteron anapole moment is discussed. The asymmetry in np -> d gamma
computed with KSW power-counting, and recently criticized by Desplanques, is
discussed. | nucl-th |
K$^+$-nucleus quasielastic scattering: K$^+$--nucleus quasielastic cross sections measured for a laboratory kaon
beam momentum of 705 MeV/$c$ are presented for 3--momentum transfers of 300 and
500 MeV/$c$. The measured differential cross sections for C, Ca and Pb at 500
MeV/$c$ are used to deduce the effective number of nucleons participating in
the scattering, which are compared with estimates based on the eikonal
approximation. The long mean free path expected for K$^+$ mesons in nuclei is
found. Double differential cross sections for C and Ca are compared to
relativistic nuclear structure calculations. | nucl-th |
Deformed shell model results for neutrinoless double beta decay of
nuclei in A=60-90 region: Nuclear transition matrix elements (NTME) for the neutrinoless double beta
decay of $^{70}$Zn, $^{80}$Se and $^{82}$Se nuclei are calculated within the
framework of the deformed shell model based on Hartree-Fock states. For
$^{70}$Zn, jj44b interaction in $^{2}p_{3/2}$, $^{1}f_{5/2}$, $^{2}p_{1/2}$ and
$^{1}g_{9/2}$ space with $^{56}$Ni as the core is employed. However, for
$^{80}$Se and $^{82}$Se nuclei, a modified Kuo interaction with the above core
and model space are employed. Most of our calculations in this region were
performed with this effective interaction. However, jj44b interaction has been
found to be better for $^{70}$Zn. The above model space was used in many recent
shell model and interacting boson model calculations for nuclei in this region.
After ensuring that DSM gives good description of the spectroscopic properties
of low-lying levels in these three nuclei considered, the NTME are calculated.
The deduced half-lives with these NTME, assuming neutrino mass is 1 eV, are
$1.1 \times 10^{26}$ yr, $2.3 \times 10^{27}$ yr and $2.2 \times 10^{24}$ yr
for $^{70}$Zn, $^{80}$Se and $^{82}$Se, respectively. | nucl-th |
The Onset of Color Transparency in $(e,e'p)$ Reactions on Nuclei: Quantum filtering of the ejectile wave packet from hard $ep$ scattering on
bound nucleons puts stringent constraints on the onset of color transparency in
$(e,e'p)$ reactions in nuclei at moderate energies. Based on
multiple-scattering theory, we derive a novel formula for nuclear transparency
and discuss its energy dependence in terms of a color transparency sum rule. | nucl-th |
Weak sensitivity of three-body ($d,p$) reactions to $np$ force models: Adiabatic distorted-wave approximation (ADWA) study of three-body $(d,p)$
transfer reactions [G.W. Bailey, N.K. Timofeyuk, and J.A. Tostevin, Phys. Rev.
Lett. 117, 162502 (2016)] reported strong sensitivity of cross sections to the
neutron-proton $(np)$ interaction model when the nucleon-nucleus optical
potential is nonlocal. The verification of this unusual finding using more
reliable methods is aimed for in the present work. A rigorous Faddeev-type
three-body scattering theory is applied to the study of $(d,p)$ transfer
reactions. The equations for transition operators are solved in the
momentum-space partial-wave framework. Differential cross sections for
$^{26}$Al$(d,p)^{27}$Al reactions are calculated using nonlocal nuclear optical
potentials and a number of realistic $np$ potentials. Only a weak dependence on
the $np$ force model is observed, typically one order of magnitude lower than
in the previous ADWA study. The shape of the angular distribution of the
experimental data is well reproduced. Cross sections of $(d,p)$ transfer
reactions calculated using a rigorous three-body method show little sensitivity
to the $np$ interaction model. This indicates a failure of the ADWA in the
context of nonlocal potentials. Some evident shortcomings of the ADWA are
pointed out. | nucl-th |
Joint $R_{AA}$ and $v_2$ predictions for $Pb+Pb$ collisions at the LHC
within DREENA-C framework: In this paper, we presented our recently developed DREENA-C framework, which
is a fully optimized computational suppression procedure based on our
state-of-the-art dynamical energy loss formalism in constant temperature finite
size QCD medium. With this framework, we for the first time, generated joint
$R_{AA}$ and $v_2$ predictions within our dynamical energy loss formalism. The
predictions are generated for both light and heavy flavor probes, and different
centrality regions in $Pb+Pb$ collisions at the LHC, and compared with the
available experimental data. Despite the fact that DREENA-C does not contain
medium evolution (to which $v_2$ is largely sensitive) and the fact that other
approaches faced difficulties in explaining $v_2$ data, we find that DREENA-C
leads to qualitatively good agreement with this data, though quantitatively,
the predictions are visibly above the experimental data. Intuitive explanation
behind such results is presented, supporting the validity of our model, and it
is expected that introduction of evolution in the ongoing improvement of DREENA
framework, will lead to better joint agreement with $R_{AA}$ and $v_2$ data,
and allow better understanding of the underlying QCD medium. | nucl-th |
Updating the nuclear reaction rate library REACLIB. (I. Experimental
reaction rates of the proton-proton chain): REACLIB is one of the most comprehensive and popular astrophysical reaction
rate libraries. However, its experimentally obtained rates for light isotopes
still rely mainly on the Caughlan & Fowler (1988) compilation and have never
been updated despite the progress in many relevant nuclear astrophysics
experiments. Moreover, due to fitting errors REACLIB is not reliable at
temperatures lower than 10^{7}K. In this work we establish the formalism for
updating the obsolete Caughlan-Fowler experimental rates of REACLIB. Then we
use the NACRE compilation and results from the LUNA experiments to update some
important charged-particle induced rates of REACLIB focusing on the
proton-proton chain. The updated rates (available also in digital form) can now
be used in the low temperature regime (below 10^{7}K) which was forbidden to
the old version of REACLIB. | nucl-th |
Viscous Hydrodynamic Predictions for Nuclear Collisions at the LHC: Hydrodynamic simulations are used to make predictions for the integrated
elliptic flow coefficient v_2 in sqrt(s)=5.5 TeV lead-lead and sqrt(s)=14 TeV
proton-proton collisions at the LHC. We predict a 10% increase in v_2 from RHIC
to Pb+Pb at LHC, and v_2 ~ 0 in p+p collisions unless eta/s < 0.08. | nucl-th |
Hadronisation in event generators from small to large systems: The results of the dynamical core-corona initialisation framework in p+p and
Pb+Pb collisions at the LHC energies are presented. We extract the fractions of
final hadron yields originating from equilibrated and non-equilibrated matter
as functions of multiplicity. We show that the contribution from
non-equilibrated matter is non-negligible even in intermediate and central
Pb+Pb collisions. The particle production from non-equilibrated matter behaves
as a correction on $c_2\{4\}$ that is purely obtained from the equilibrated
matter. The result poses a warning on Bayesian parameter estimation with
conventional hydrodynamic models. The observed flow coefficients might need a
reinterpretation with new dynamical models which incorporate the particle
production from non-equilibrated matter. | nucl-th |
Cumulants of conserved charges in hydrodynamic simulations: We introduce a fast and simple method of computing cumulants of net-proton or
net-charge fluctuations in event-by-event hydrodynamic simulations of heavy-ion
collisions. One evaluates the mean numbers of particles in every hydrodynamic
event. Cumulants are then expressed as a function of these mean numbers. We
implement the corrections due to global conservation laws. The method is tested
using ideal hydrodynamic simulations of Au+Au collisions at $\sqrt{s_{NN}}=200$
AGeV with the NeXSPheRIO code. Results are in good agreement with experimental
data on net-proton and net-charge fluctuations by the STAR collaboration. | nucl-th |
Three-Body Forces Produced by a Similarity Renormalization Group
Transformation in a Simple Model: A simple class of unitary renormalization group transformations that force
hamiltonians towards a band-diagonal form produce few-body interactions in
which low- and high-energy states are decoupled, which can greatly simplify
many-body calculations. One such transformation has been applied to
phenomenological and effective field theory nucleon-nucleon interactions with
success, but further progress requires consistent treatment of at least the
three-nucleon interaction. In this paper we demonstrate in an extremely simple
model how these renormalization group transformations consistently evolve two-
and three-body interactions towards band-diagonal form, and introduce a
diagrammatic approach that generalizes to the realistic nuclear problem. | nucl-th |
Solution to the Proton Radius Problem: The relationship between the electric form factors for the proton in the rest
frame and in the Breit momentum frame is used to provide a value for the
difference in the mean squared charge radius of the proton evaluated in the two
frames. Associating the muonic-hydrogen data analysis for the proton charge
radius of 0.84087 fm with the rest frame and associating the electron
scattering with the Breit frame yields a prediction 0f 0.87944 fm for the
proton radius in the relativistic frame. The most recent value deduced via
electron scattering from the proton is 0.877(6)fm so that the frame dependence
used here yields a plausible solution to the proton radius puzzle. | nucl-th |
A Nonlinear Realized Approach of SU(2) Chiral Symmetry Spontaneous
Breaking and Properties of Nuclear Matter: A nonlinear realization of SU(2) chiral symmetry spontaneous breaking
approach is developed in the composite operator formalism. A Lagrangian
including quark, gluon and Goldstone boson degrees of freedom of the chiral
quark model is obtained from the QCD Lagrangian. A way to link the chiral
symmetry spontaneous breaking formalism at hadron level and that at quark level
is predicted. too. The application to nuclear matter shows that the approach is
quite successful in describing the properties of nuclear matter and the quark
condensate in it. | nucl-th |
SPQR -- Spectroscopy: Prospects, Questions & Results: Tremendous progress has been made in mapping out the spectrum of hadrons over
the past decade with plans to make further advances in the decade ahead.
Baryons and mesons, both expected and unexpected, have been found, the results
of precision experiments often with polarized beams, polarized targets and
sometimes polarization of the final states. All these hadrons generate poles in
the complex energy plane that are consequences of strong coupling QCD. They
reveal how this works. | nucl-th |
Magnetic dipole excitation and its sum rule in nuclei with two valence
nucleons: Background: Magnetic dipole (M1) excitation is the leading mode of nuclear
excitation by the magnetic field, which couples unnatural-parity states. Since
the M1 excitation occurs mainly for open-shell nuclei, the nuclear pairing
effect is expected to play a role. As expected from the form of operator, this
mode may provide the information on the spin-related properties, including the
spin component of dineutron and diproton correlations. In general, the sum rule
for M1 transition strength has not been derived yet. Purpose: To investigate
the M1 excitation of the systems with two valence nucleons above the
closed-shell core, with pairing correlation included, and to establish the M1
sum rule that could be used to validate theoretical and experimental
approaches. Possibility to utilize the M1 excitation as a tool to investigate
the pairing correlation in medium is also discussed. Method: Three-body model,
which consists of a rigid spherical core and two valence nucleons, is employed.
Interactions for its two-body subsystems are phenomenologically determined in
order to reproduce the two-body and three-body energies. We also derive the M1
sum rule within this three-body picture. Conclusion: The introduced M1 sum rule
can be utilized as a benchmark for model calculations of M1 transitions in the
systems with two valence nucleons. The total sum of the M1 transition strength
is related with the coupled spin of valence nucleons in the open shell, where
the pairing correlation is unnegligible. The three-body-model calculations for
18 O, 18 Ne, and 42 Ca nuclei demonstrate a significant effect of the pairing
correlations on the low-lying M1 transitions. Therefore, further experimental
studies of M1 transitions in those systems are on demand, in order to validate
proposed sum rule, provide a suitable probe for the nuclear pairing in medium,
as well as to optimize the pairing models. | nucl-th |
DREENA-A framework as a QGP tomography tool: We present a fully optimised framework DREENA-A based on a state-of-the-art
energy loss model. The framework can include any, in principle arbitrary,
temperature profile within the dynamical energy loss formalism. Thus, 'DREENA'
stands for Dynamical Radiative and Elastic ENergy loss Approach, while 'A'
stands for Adaptive. DREENA-A does not use fitting parameters within the energy
loss model, allowing it to fully exploit differences in temperature profiles
which are the only input in the framework. The framework applies to light and
heavy flavor observables, different collision energies, and large and smaller
systems. This, together with the ability to systematically compare data and
predictions within the same formalism and parameter set, makes DREENA-A a
unique multipurpose QGP tomography tool. | nucl-th |
Nuclear vorticity in isoscalar E1 modes: Skyrme-RPA analysis: Two basic concepts of nuclear vorticity, hydrodynamical (HD) and
Rawenthall-Wambach (RW), are critically inspected. As a test case, we consider
the interplay of irrotational and vortical motion in isoscalar electric dipole
E1(T=0) modes in $^{208}$Pb, namely the toroidal and compression modes. The
modes are described in a self-consistent random-phase-approximation (RPA) with
the Skyrme force SLy6. They are examined in terms of strength functions,
transition densities, current fields, and formfactors. It is shown that the RW
conception (suggesting the upper component of the nuclear current as the
vorticity indicator) is not robust. The HD vorticity is not easily applicable
either because the definition of a velocity field is too involved in nuclear
systems. Instead, the vorticity is better characterized by the toroidal
strength which closely corresponds to HD treatment and is approximately
decoupled from the continuity equation. | nucl-th |
Relativistic third-order dissipative fluid dynamics from kinetic theory: We present the derivation of a novel third-order hydrodynamic evolution
equation for shear stress tensor from kinetic theory. Boltzmann equation with
relaxation time approximation for the collision term is solved iteratively
using Chapman-Enskog like expansion to obtain the nonequilibrium phase-space
distribution function. Subsequently, the evolution equation for shear stress
tensor is derived from its kinetic definition up-to third-order in gradients.
We quantify the significance of the new derivation within one-dimensional
scaling expansion and demonstrate that the results obtained using third-order
viscous equations derived here provides a very good approximation to the exact
solution of Boltzmann equation in relaxation time approximation. We also show
that the time evolution of pressure anisotropy obtained using our equations is
in better agreement with transport results when compared with an existing
third-order calculation based on the second-law of thermodynamics. | nucl-th |
Photoproduction $γp \to K^{*+} Λ$ in a Reggeized model: The high-precision differential cross-section data for the reaction $\gamma p
\to K^{*+}\Lambda$ are reanalyzed within a Regge-inspired effective Lagrangian
approach. The model adopts Regge phenomenology to constrain the $t$-channel
contributions from the $\kappa$, $K$, and $K^*$ exchanges. A minimal number of
resonances in the $s$ channel are introduced in constructing the reaction
amplitudes in order to describe the data. It is shown that the differential
cross-section data for $\gamma p \to K^{*+}\Lambda$ can be satisfactorily
described by introducing the only $N(2060){5/2}^-$ resonance in the $s$
channel, which is quite different from our earlier work performed in an
effective Lagrangian approach [A. C. Wang {\it et al.}, Phys. Rev. C 96, 035206
(2017)], where the amplitudes are computed by evaluating Feynman diagrams and
it is found that introducing at least one additional resonance apart from the
$N(2060){5/2}^-$ is indispensable for reproducing the data. The roles of
individual contributions from meson and baryon exchanges on the angular
distributions are found to be highly model dependent. The extracted mass of
$N(2060){5/2}^-$ turns out to be well determined, independent of how the
$t$-channel amplitudes are constructed, whereas the width does not. | nucl-th |
`` $Λ- Σ$ conversion in $^4_Λ$He and $^4_Λ$H
based on four-body calculation: Precise four-body calculations for $^4_{\Lambda}$He and $^4_{\Lambda}$H have
been performed in the framework of the variational method with
Jacobian-coordinate Gaussian-basis functions. All the rearrangement channels of
both $NNN \Lambda$ and $NNN \Sigma$ are explicitly taken into account for the
first time with the use of realistic $NN$ and $YN$ interactions. The role of
$\Lambda$-$\Sigma$ conversion and the amount of the virtual $\Sigma$-component
in $^4_{\Lambda}$He and $^4_{\Lambda}$H are discussed. | nucl-th |
Induced magnetic moment in the magnetic catalysis of chiral symmetry
breaking: The chiral symmetry breaking in a Nambu-Jona-Lasinio effective model of
quarks in the presence of a magnetic field is investigated. We show that new
interaction tensor channels open up via Fierz identities due to the explicit
breaking of the rotational symmetry by the magnetic field. We demonstrate that
the magnetic catalysis of chiral symmetry breaking leads to the generation of
two independent condensates, the conventional chiral condensate and a spin-one
condensate. While the chiral condensate generates, as usual, a dynamical
fermion mass, the new condensate enters as a dynamical anomalous magnetic
moment in the dispersion of the quasiparticles. Since the pair, formed by a
quark and an antiquark with opposite spins, possesses a resultant magnetic
moment, an external magnetic field can align it giving rise to a net magnetic
moment for the ground state. The two condensates contribute to the effective
mass of the LLL quasiparticles in such a way that the critical temperature for
chiral symmetry restoration becomes enhanced. | nucl-th |
Generalized time-dependent generator coordinate method for small and
large amplitude collective motion: An implementation of the generalized time-dependent generator coordinated
method (TD-GCM) is developed, that can be applied to the dynamics of small- and
large-amplitude collective motion of atomic nuclei. Both the generator states
and weight functions of the GCM correlated wave function depend on time. The
initial generator states are obtained as solutions of deformation-constrained
self-consistent mean-field equations, and are evolved in time by the standard
mean-field equations of nuclear density functional theory (TD-DFT). The TD-DFT
trajectories are used as a generally non-orthogonal and overcomplete basis in
which the TD-GCM wave function is expanded. The weights, expressed in terms of
a collective wave function, obey a TD-GCM (integral) equation. In this
explorative paper, the generalized TD-GCM is applied to the excitation energies
and spreading width of giant resonances, and to the dynamics of induced
fission. The necessity of including pairing correlations in the basis of TD-DFT
trajectories is demonstrated in the latter example. | nucl-th |
$ππ$ scattering in the $ρ$-meson channel at finite temperature: We study $\pi\pi$ scattering in the I=1, $J^P=1^-$ channel at finite
temperature in the framework of the extended Nambu-Jona-Lasinio model that
explicitly includes vector and axial-vector degrees of freedom in addition to
the usual scalar and pseudoscalar sector. The S-matrix in the coupled channels
$q\bar q$ and $\pi \pi$ is constructed via $\rho$-exchange in the $s$-channel.
The self-energy of the $\rho$-meson contains both quark and pion loop
contributions. The analytic structure of the S-matrix for $T\geq 0$ is
investigated and the motion of the $\rho$-pole as a function of coupling
constant and temperature is followed in the complex $\sqrt{s}$-plane. For
numerical calculations, parameters are chosen in order that $m_\pi$, $f_\pi$
and the experimental $\pi\pi$ phase shifts $\delta_1^1$ at zero temperature are
reproduced, and then the behavior of the $\rho$-pole as well as the $\pi\pi$
cross section is investigated as a function of the temperature. We find that
the position of the $\rho$ mass stays practically constant for $0\leq T\leq
130$ MeV, and then moves down in energy by about 200 MeV for 130 MeV$\leq T\leq
230$ MeV. | nucl-th |
Partial dynamical symmetry in quantum Hamiltonians with higher-order
terms: A generic procedure is proposed to construct many-body quantum Hamiltonians
with partial dynamical symmetry. It is based on a tensor decomposition of the
Hamiltonian and allows the construction of a hierarchy of interactions that
have selected classes of solvable states. The method is illustrated in the
SO(6) limit of the interacting boson model of atomic nuclei and applied to the
nucleus $^{196}$Pt. | nucl-th |
Wormhole Model for Neon-20: A quantum mechanical model for the Neon-20 nucleus is developed that allows
for the splitting of a bipyramidal structure of five alpha-partices into an
alpha-particle and an Oxygen-16 nucleus. The geometry of the configuration
space is assumed to be a 3-dimensional spatial wormhole, and on the wormhole
background there is an attractive short-range potential. This leads to a radial
Schr\"odinger equation of the Heun form, which simplifies for threshold bound
states to an associated Legendre equation that has explicit solutions. The
energies of the true bound states for all spin/parities are numerically
calculated, and match those of the well-established $K^\pi=0^+$, $K^\pi=0^-$,
and certain higher rotational bands of Neon-20. | nucl-th |
A simple functional form for proton-${}^{208}$Pb total reaction cross
sections: A simple functional form has been found that gives a good representation of
the total reaction cross sections for the scattering from ${}^{208}$Pb of
protons with energies in the range 30 to 300 MeV. | nucl-th |
Determination of the $\boldsymbol{η^3{\rm He}}$ threshold structure
from the low energy $\boldsymbol{pd \to η^3{\rm He}}$ reaction: We analyze the data on cross sections and asymmetries for the $pd (dp) \to
\eta ^3{\rm He}$ reaction close to threshold and look for bound states of the
$\eta ^3 {\rm He}$ system. Rather than parameterizing the scattering matrix, as
is usually done, we develop a framework in which the $\eta ^3 {\rm He}$ optical
potential is the key ingredient, and its strength, together with some
production parameters, are fitted to the available experimental data. The
relationship of the scattering matrix to the optical potential is established
using the Bethe-Salpeter equation and the $\eta ^3 {\rm He}$ loop function
incorporates the range of the interaction given by the empirical $^3 {\rm He}$
density. We find a local Breit Wigner form of the $\eta^3$He amplitude $T$
below threshold with a clear peak in $|T|^2$, which corresponds to an $\eta^3
{\rm He}$ binding of about 0.3 MeV and a width of about 3 MeV. By fitting the
potential we can also evaluate the $\eta ^3 {\rm He}$ scattering length,
including its sign, thus resolving the ambiguity in the former analyses. | nucl-th |
Threshold 3He and 3H Transverse Electron Scattering Response Functions: The threshold transverse response functions R_T(q,omega) for 3He and 3H are
calculated using the AV18 nucleon-nucleon potential, the UrbanaIX three-body
force, and the Coulomb potential. Final states are completely taken into
account via the Lorentz integral transform technique. Consistent two-body pi-
and rho-meson exchange currents as deduced using the Arenh\"ovel-Schwamb
technique are included. The convergence of the method is shown and a comparison
of the corresponding MEC contribution is made to that of a consistent MEC for
the meson theoretical r-space BonnA potential. The response R_T is calculated
in the threshold region at q=174, 324, and 487 MeV/c and compared with
available data. The strong MEC contributions in the threshold region are nicely
confirmed by the data at q=324 and 487 MeV/c although some differences between
theoretical and experimental results remain. A comparison is also made with
other calculations, where the same theoretical input is used. The agreement is
generally rather good, but leaves also some space for further improvement. | nucl-th |
Measuring the speed of sound using cumulants of baryon number: We show that the values of the first three cumulants of the baryon number
distribution can be used to calculate the isothermal speed of sound and its
logarithmic derivative with respect to the baryon number density. We discuss
applications of this result to heavy-ion collision experiments and address
possible challenges, including effects due to baryon number conservation,
differences between proton and baryon cumulants, and the influence of finite
number statistics on fluctuation observables in both experiment and hadronic
transport simulations. In particular, we investigate the relation between
quantities calculated in infinite, continuous matter and observables obtained
in simulations using a finite number of particles. | nucl-th |
Decorrelation of anisotropic flows along the longitudinal direction: The initial energy density distribution and fluctuation in the transverse
direction lead to anisotropic flows of final hadrons through collective
expansion in high-energy heavy-ion collisions. Fluctuations along the
longitudinal direction, on the other hand, can result in decorrelation of
anisotropic flows in different regions of pseudo rapidity ($\eta$).
Decorrelation of the $2$nd and $3$rd order anisotropic flows with different
$\eta$ gaps for final charged hadrons in high-energy heavy-ion collisions is
studied in an event-by-event (3+1)D ideal hydrodynamic model with fully
fluctuating initial conditions from A Multi-Phase Transport (AMPT) model. The
decorrelation of anisotropic flows of final hadrons with large $\eta$ gaps are
found to originate from the spatial decorrelation along the longitudinal
direction in the AMPT initial conditions through hydrodynamic evolution. The
decorrelation is found to consist of both a linear twist and random fluctuation
of the event-plane angles. The agreement between our results and recent CMS
data in most centralities suggests that the string-like mechanism of initial
parton production in AMPT model captures the initial longitudinal fluctuation
that is responsible for the measured decorrelation of anisotropic flows in
Pb+Pb collisions at LHC. Our predictions for Au+Au collisions at the highest
RHIC energy show stronger longitudinal decorrelation, indicating larger
longitudinal fluctuations at lower beam energies. Our study also calls into
question some of the current experimental methods for measuring anisotropic
flows and extraction of transport coefficients through comparisons to
hydrodynamic simulations that do not include longitudinal fluctuations. | nucl-th |
Probing nuclear quadrupole deformation from correlation of elliptic flow
and transverse momentum in heavy ion collisions: In heavy ion collisions, elliptic flow $v_2$ and radial flow, characterized
by event-wise average transverse momentum $[p_{\mathrm{T}}]$, are related to
the shape and size of the overlap region, which are sensitive to the shape of
colliding atomic nuclei. The Pearson correlation coefficient between $v_2$ and
$[p_{\mathrm{T}}]$, $\rho_2$, was found to be particularly sensitive to the
quadrupole deformation parameter $\beta$ that is traditionally measured in low
energy experiments. Built on earlier insight that the prolate deformation
$\beta>0$ reduces the $\rho_2$ in ultra-central collisions (UCC), we show that
the prolate deformation $\beta<0$ enhances the value of $\rho_2$. As $\beta>0$
and $\beta<0$ are the two extremes of triaxiality, the strength and sign of
$v_2^2-[p_{\mathrm{T}}]$ correlation can be used to provide valuable
information on the triaxiality of the nucleus. Our study provide further
arguments for using the hydrodynamic flow as a precision tool to directly image
the deformation of the atomic nuclei at extremely short time scale
($<10^{-24}$s). | nucl-th |
Recent developments in weak-coupling color superconductivity: Recent developments in weak-coupling color superconductivity are reviewed.
These developments are as follows. The mean field gap equation is solved for
most common superconducting phases up to subleading order; BCS relation is
found to be violated in color-flavor-locking and color-spin-locking phases due
to the two-gaps structure of the order parameter; The Debye and Meissner masses
of gluons and photon with their rotated partners are calculated for these
phases; We found that there is no electromagnetic Meissner effect in spin-one
color superconductor; A proof of gauge parameter independence at subleading
order is given in covariant gauge. | nucl-th |
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