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Neutron Anomalous Magnetic Moment in Dense Magnetized Systems: In this work, we calculate the neutron anomalous magnetic moment supposing
that this value can depend on the density and magnetic field of system. We
employ the lowest order constraint variation (LOCV) method and $AV_{18}$
nuclear potential to calculate the medium dependency of the neutron anomalous
magnetic moment. It is confirmed that the neutron anomalous magnetic moment
increases by increasing the density, while it decreases as the magnetic field
grows. The energy and equation of state for the system have also been
investigated. | nucl-th |
Rotation and alignment of high-$j$ orbitals in transfermium nuclei: The structure of nuclei with $Z\sim100$ is investigated systematically by the
Cranked Shell Model (CSM) with pairing correlations treated by a
Particle-Number Conserving (PNC) method. In the PNC method, the particle number
is conserved and the Pauli blocking effects are taken into account exactly. By
fitting the experimental single-particle spectra in these nuclei, a new set of
Nilsson parameters ($\kappa$ and $\mu$) is proposed. The experimental kinematic
moments of inertia and the band-head energies are reproduced quite well by the
PNC-CSM calculations. The band crossing, the effects of high-$j$ intruder
orbitals and deformation are discussed in detail. | nucl-th |
Interference Effect Between Neutron Direct and Resonance Capture
Reactions For Neutron-Rich Nuclei: Interference effect of neutron capture cross section between the compound and
direct processes is investigated. The compound process is calculated by
resonance parameters and the direct process by the potential mode. The
interference effect is tested for neutron-rich $^{82}$Ge and $^{134}$Sn nuclei
relevant to $r$-process and light nucleus $^{13}$C which is neutron poison in
the $s$-process and produces long-lived radioactive nucleus $^{14}$C
($T_{1/2}=5700$ y). The interference effects in those nuclei are significant
around resonances, and low energy region if $s$-wave neutron direct capture is
possible. Maxwellian averaged cross sections at $kT=30$ and $300$ keV are also
calculated, and the interference effect changes the Maxwellian averaged capture
cross section largely depending on resonance position. | nucl-th |
Parity Mixed Doublets in A = 36 Nuclei: The $\gamma$-circular polarizations ($P_{\gamma}$) and asymmetries
($A_{\gamma}$) of the parity forbidden M1 + E2 $\gamma$-decays: $^{36}Cl^{\ast}
(J^{\pi} = 2^{-}; T = 1; E_{x} = 1.95 $ MeV) $\rightarrow$ $^{36}Cl (J^{\pi} =
2^{+}; T = 1; g.s.)$ and $^{36}Ar^{\ast} (J^{\pi} = 2^{-}; T = 0; E_{x} = 4.97
$ MeV) $\rightarrow$ $^{36}Ar^{\ast} (J^{\pi} = 2^{+}; T = 0; E_{x} = 1.97 $
MeV) are investigated theoretically. We use the recently proposed
Warburton-Becker-Brown shell-model interaction. For the weak forces we discuss
comparatively different weak interaction models based on different assumptions
for evaluating the weak meson-hadron coupling constants. The results determine
a range of $P_{\gamma}$ values from which we find the most probable values:
$P_{\gamma}$ = $1.1 \cdot 10^{-4}$ for $^{36}Cl$ and $P_{\gamma}$ = $3.5 \cdot
10^{-4}$ for $^{36}Ar$. | nucl-th |
Skyrme interaction to second order in nuclear matter: Based on the phenomenological Skyrme interaction various density-dependent
nuclear matter quantities are calculated up to second order in many-body
perturbation theory. The spin-orbit term as well as two tensor terms contribute
at second order to the energy per particle. The simultaneous calculation of the
isotropic Fermi-liquid parameters provides a rigorous check through the
validity of the Landau relations. It is found that published results for these
second order contributions are incorrect in most cases. In particular,
interference terms between $s$-wave and $p$-wave components of the interaction
can contribute only to (isospin or spin) asymmetry energies. Even with nine
adjustable parameters, one does not obtain a good description of the empirical
nuclear matter saturation curve in the low density region $0<\rho<2\rho_0$. The
reason for this feature is the too strong density-dependence $\rho^{8/3}$ of
several second-order contributions. The inclusion of the density-dependent term
${1\over 6}t_3 \rho^{1/6}$ is therefore indispensable for a realistic
description of nuclear matter in the Skyrme framework. | nucl-th |
Missing Resonances in Kaon Photoproduction on the Nucleon: New kaon photoproduction data on a proton, gamma + p --> K+ + Lambda, are
analyzed using a multipole approach. The background terms are given in terms of
gauge invariant, crossing symmetric, Born diagrams with hadronic form factors,
while the resonances are parameterized using Breit-Wigner forms. Preliminary
results suggest a number of new resonances, as predicted by many quark model
studies. A comparison between the extracted multipoles and those obtained from
KAON-MAID is presented. | nucl-th |
The Nuclear Reactions in Standard BBN: Nowadays, the Cosmic Microwave Background (CMB) anisotropies studies
accurately determine the baryon fraction omega_b, showing an overall and
striking agreement with previous determinations of omega_b obtained from Big
Bang Nucleosynthesis (BBN). However, a deeper comparison of BBN predictions
with the determinations of the primordial light nuclides abundances shows
slight tensions, motivating an effort to further improve the accuracy of
theoretical predictions, as well as to better evaluate systematics in both
observations and nuclear reactions measurements. We present some results of an
important step towards an increasing precision of BBN predictions, namely an
updated and critical review of the nuclear network, and a new protocol to
perform the nuclear data regression. | nucl-th |
Perturbative accelerating solutions of relativistic hydrodynamics: In ultra-relativistic collisions of heavy ions, the strongly interacting
Quark Gluon Plasma (sQGP) is created. The fluid nature of the sQGP was one of
the important discoveries of high energy heavy ion physics in the last decades.
Henceforth the explosion of this matter may be described by hydrodynamical
models. Besides numerical simulations, it is important to study the analytic
solutions of the equations of hydrodynamics, as these enable us to understand
the connection of the final and initial states better. In this paper we present
a perturbative, accelerating solution of relativistic hydrodynamics, on top of
a known class of solutions describing Hubble-expansion. We describe the
properties of this class of perturbative solutions, and investigate a few
selected solutions in detail. | nucl-th |
Studies of quasiclassical approach applicability to true three-body
decays: Within the hyperspherical harmonics approach the three-body problem is
reduced to a motion of one effective particle in a "strongly deformed" field,
which is described in coupled-channel formalism. This method is especially
suited to studies of phenomena characterized by genuine three-body dynamics,
e.g. Borromean haloes and true three-body decays. The reduction of the
hyperspherical equations set to a single-channel Schr\"odinger equation
provides the basis for the use of the standard quasiclassical expression for
calculations of widths for true three-body decays. We demonstrate that the
quasiclassical approach by itself is quite precise in application to typical
profiles of the three-body effective potentials. However, the reduction to
single-channel formalism leads to significant overestimation of the two-proton
width $\Gamma_{2p}$. This is demonstrated by the example of the $^{17}$Ne first
excited $3/2^-$ state decay, questioning, however, the applicability of such an
approximation in general. | nucl-th |
The entropy puzzle and the quark combination model: We use two available methods, the Duhem-Gibbs relation and the entropy
formula in terms of particle phase space distributions, to calculate the
entropy in a quark combination model. The entropy of the system extracted from
the Duhem-Gibbs relation is found to increase in hadronization if the average
temperature of the hadronic phase is lower than that of the quark phase. The
increase of the entropy can also be confirmed from the entropy formula if the
volume of the hadronic phase is larger than 2.5-3.0 times that of the quark
phase. So whether the entropy increases or decreases during combination depends
on the temperature before and after combination and on how much expansion the
system undergoes during combination. The current study provides an example to
shed light on the entropy issue in the quark combination model. | nucl-th |
Chiral effective field theory for nuclear matter: We report on the recent developments of a new effective field theory for
nuclear matter [1,2,3]. We present first the nuclear matter chiral power
counting that takes into account both short-- and long--range inter-nucleon
interactions. It also identifies non-perturbative strings of diagrams, related
to the iteration of nucleon-nucleon interactions, which have to be re-summed.
The methods of unitary chiral perturbation theory has been shown to be a useful
tool in order to perform those resummations. Results up to next-to-leading
order for the ground state energy per particle of nuclear matter, the in-medium
chiral quark condensate and pion self-energy are discussed. | nucl-th |
The sixth order cumulant of net-proton number in Binomial distribution
at $\sqrt{s_{NN}} = $ 200 GeV: It is proposed that ratios of the sixth order to the second order cumulant
($C_6/C_2$) of conserved quantities are sensitive to the chiral crossover
transition. Recently, the negative $C_6/C_2$ was obtained both in theoretical
Lattice QCD and experiments at $\sqrt{s_{NN}} = $ 200 GeV. In this study, we
investigate the behavior of net-proton $C_6/C_2$ in statistical Binomial
distribution (BD) at $\sqrt{s_{NN}} = $ 200 GeV in Au + Au collisions. With the
BD parameters extracted from RHIC/STAR, it is found that $C_6/C_2$ can be
negative. Furthermore, the obtained $C_6/C_2$ becomes smaller when applying the
same magnitude of experimental statistics and calculation method to
simulations. In 0-10\% centrality, there is a significant difference between
the simulated result and theoretical expectation. Based on the extracted
parameters and experimentally collected statistics, the baseline of net-proton
$C_6/C_2$ in BD is presented. | nucl-th |
Probing the multi-scale dynamical interaction between heavy quarks and
the QGP using JETSCAPE: The dynamics of shower development for a jet traveling through the QGP
involves a variety of scales, one of them being the heavy quark mass. Even
though the mass of the heavy quarks plays a subdominant role during the high
virtuality portion of the jet evolution, it does affect longitudinal drag and
diffusion, stimulating additional radiation from heavy quarks. These emissions
partially compensate the reduction in radiation from the dead cone effect. In
the lower virtuality part of the shower, when the mass is comparable to the
transverse momenta of the partons, scattering and radiation processes off heavy
quarks differ from those off light quarks. All these factors result in a
different nuclear modification factor for heavy versus light flavors and thus
for heavy-flavor tagged jets.
In this study, the heavy quark shower evolution and the fluid dynamical
medium are modeled on an event by event basis using the JETSCAPE Framework. We
present a multi-stage calculation that explores the differences between various
heavy quark energy-loss mechanisms within a realistically expanding quark-gluon
plasma (QGP). Inside the QGP, the highly virtual and energetic portion of the
shower is modeled using the MATTER generator, while the LBT generator models
the showers induced by energetic and close-to-on-shell heavy quarks.
Energy-momentum exchange with the medium, essential for the study of jet
modification, proceeds using a weak coupling recoil approach. The JETSCAPE
framework allows for transitions, on the level of individual partons, from one
energy-loss prescription to the other depending on the parton's energy and
virtuality and the local density. This allows us to explore the effect and
interplay between the different regimes of energy loss on the propagation and
radiation from hard heavy quarks in a dense medium. | nucl-th |
Equivalence between first-order causal and stable hydrodynamics and
Israel-Stewart theory for boost-invariant systems with a constant relaxation
time: We show that the recently formulated causal and stable first-order
hydrodynamics has the same dynamics as Israel-Stewart theory for
boost-invariant, Bjorken expanding systems with a conformal equation of state
and a regulating sector determined by a constant relaxation time. In this case,
the general solution of the new first-order formulation can be determined
analytically. | nucl-th |
The baryon number two system in the Chiral Soliton Model: We study the interaction between two B = 1 states in a Chiral Soliton Model
where baryons are described as non-topological solitons. By using the hedgehog
solution for the B = 1 states we construct three possible B = 2 configurations
to analyze the role of the relative orientation of the hedgehog quills in the
dynamics. The strong dependence of the intersoliton interaction on these
relative orientations reveals that studies of dense hadronic matter using this
model should take into account their implications. | nucl-th |
Hadronic resonance production and interaction in p-Pb collisions at LHC
energies in EPOS3: Using the EPOS3 model with UrQMD to describe the hadronic phase, we study the
production of short-lived hadronic resonances and the modification of their
yields and $p_{T}$ spectra in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV.
High-multiplicity p-Pb collisions exhibit similar behavior to mid-peripheral
Pb-Pb collisions at LHC energies, and we find indications of a short-lived
hadronic phase in p-Pb collisions that can modify resonance yields and $p_{T}$
spectra through scattering processes. The evolution of resonance production is
investigated as a function of the system size, which is related to the lifetime
of the hadronic phase, in order to study the onset of collective effects in
p-Pb collisions. We also study hadron production separately in the core and
corona parts of these collisions, and explore how this division affects the
total particle yields as the system size increases. | nucl-th |
Perspectives on few-body cluster structures in exotic nuclei: It is a fascinating phenomenon in nuclear physics that states with a
pronounced few-body structure can emerge from the complex dynamics of many
nucleons. Such halo or cluster states often appear near the boundaries of
nuclear stability. As such, they are an important part of the experimental
program beginning at the Facility for Rare Isotope Beams (FRIB). A concerted
effort of theory and experiment is necessary both to analyze experiments
involving effective few-body states, as well as to constrain and refine
theories of the nuclear force in light of new data from these experiments. As a
contribution to exactly this effort, this paper compiles a collection of
``perspectives'' that emerged out of the Topical Program ``Few-body cluster
structures in exotic nuclei and their role in FRIB experiments'' that was held
at FRIB in August 2022 and brought together theorists and experimentalists
working on this topic. | nucl-th |
Elliptic flow from a parton cascade: The dependence of elliptic flow at RHIC energies on the effective parton
scattering cross section is calculated using the ZPC parton cascade model. We
show that the v_2 measure of elliptic flow saturates early in the evolution
before the hadronization transition to a rather large value ~0.05-0.15 as
\sigma_g varies from 2-10 mb and thus is a sensitive probe of the dynamics in
the plasma phase. | nucl-th |
Mean field approach to flavor susceptibilities with a vector interaction: We show that flavor diagonal and off-diagonal susceptibilities of light
quarks at vanishing chemical potential can be calculated consistently assuming
the baryon density and isospin density dependence of QCD to be expressed by a
vector-isoscalar and a vector-isovector coupling, respectively. At the mean
field level, their expression depends only on the effective medium-dependent
couplings and quark thermodynamic potential. The strength of the couplings can
be then estimated from the model using lattice QCD data as an input. | nucl-th |
Relativistic Approach to Isoscalar Giant Resonances in 208Pb: We calculate the longitudinal response of 208Pb using a relativistic
random-phase approximation to three different parameterizations of the Walecka
model with scalar self-interactions. From a nonspectral calculation of the
response-that automatically includes the mixing between positive- and
negative-energy states-we extract the distribution of strength for the
isoscalar monopole, dipole, and high-energy octupole resonances. We employ a
consistent formalism that uses the same interaction in the calculation of the
ground state as in the calculation of the response. As a result, the
conservation of the vector current is strictly maintained throughout the
calculation. Further, at small momentum transfers the spurious dipole
strength-associated with the uniform translation of the center-of-mass-gets
shifted to zero excitation energy and is cleanly separated from the sole
remaining physical fragment located at an excitation energy of about 24 MeV; no
additional dipole strength is observed. The best description of the collective
modes is obtained using a ``soft'' parameterization having a compression
modulus of K=224 MeV. | nucl-th |
Nuclear medium effects in $ν/\barν$-A DIS: Nuclear medium effects in the weak structure functions $F_2(x,Q^2)$ and
$F_3(x,Q^2)$ have been studied for deep inelastic neutrino/antineutrino
reactions in iron nucleus by taking into account Fermi motion, binding, pion
and rho meson cloud contributions, target mass correction, shadowing and
anti-shadowing corrections. The calculations have been performed in a local
density approximation using relativistic nuclear spectral functions which
include nucleon correlations. Using these structure functions we have obtained
the ratio $R_{F2,F3}^A(x,Q^2)= \frac{2F_{2,3}^A(x,Q^2)}{AF_{2,3}^D(x,Q^2)}$,
the differential scattering cross section $\frac{1}{E}\frac{d^2\sigma}{dxdy}$
and the total scattering cross section $\sigma$. The results of our numerical
calculations in $^{56}Fe$ are compared with the experimental results of NuTeV
and CDHSW collaborations. | nucl-th |
Probing Vector Mesons in Deuteron Break-up Reactions: We study vector meson photoproduction from the deuteron at high momentum
transfer, accompanied by break-up of the deuteron into a proton and neutron.
The large $-t$ involved allows one of the nucleons to be identified as struck,
and the other as a spectator to the $\gamma N\rightarrow VN$ subprocess.
Corrections to the plane wave impulse approximation involve final state
interactions (FSIs) between the struck nucleon or the vector meson, either of
which is energetic, with the slow spectator nucleon. In this regime, the
eikonal approximation is valid, so is employed to calculate the cross-section
for the reaction. Due to the high-energy nature of the FSIs, the maxima of the
rescatterings are located at nearly transverse directions of the fast hadrons.
This results in two peaks in the angular distribution of the spectator nucleon,
each corresponding to either the $V$-$N$ or the $p$-$n$ rescattering. The
$V$-$N$ peak provides a new means of probing the $V$-$N$ interaction. This is
checked for near-threshold $\phi$ and $J/\Psi$ photoproduction reactions which
demonstrate that the $V$-$N$ peak can be used to extract the largely unknown
amplitudes of $\phi$-$N$ and $J/\Psi$-$N$ interactions.
Two additional phenomena are observed when extending the calculation of
$J/\Psi$ photoproduction to the sub-threshold and high-energy domains. In the
first case we observe overall suppression of FSI effects due to a restricted
phase space for sub-threshold production in the rescattering amplitude. In the
second, we observe cancellation of the $V$-$N$ rescattering amplitudes for
vector mesons produced off of different nucleons in the deuteron. | nucl-th |
Resonances in the three-neutron system: A study of 3-body resonances has been performed in the framework of
configuration space Faddeev equations. The importance of keeping a sufficient
number of terms in the asymptotic expansion of the resonance wave function is
pointed out. We investigated three neutrons interacting in selected force
components taken from realistic nn forces. | nucl-th |
Faddeev calculation of 6 He Lambda Lambda using SU_6 quark-model
baryon-baryon interactions: Quark-model hyperon-nucleon and hyperon-hyperon interactions by the
Kyoto-Niigata group are applied to the two-Lambda plus alpha system in a new
three-cluster Faddeev formalism using two-cluster resonating-group method
kernels. The model fss2 gives a reasonable two-Lambda separation energy Delta
B_{Lambda Lambda}=1.41 MeV, which is consistent with the recent empirical
value, Delta B^{exp}_{Lambda Lambda}=1.01 +/- 0.20 MeV, deduced from the Nagara
event. Some important effects that are not taken into account in the present
calculation are discussed. | nucl-th |
Meson elastic and transition form factors: The Dyson-Schwinger equations of QCD, truncated to ladder-rainbow level, are
used to calculate meson form factors in impulse approximation. The infrared
strength of the ladder-rainbow kernel is described by two parameters fitted to
the chiral condensate and f_pi; the ultraviolet behavior is fixed by the QCD
running coupling. This obtained elastic form factors F_pi(Q^2) and F_K(Q^2)
agree well with the available data. We also calculate the rho to pi gamma and
K* to K gamma transition form factors, which are useful for meson-exchange
models. | nucl-th |
Gaussian matrix elements in a cylindrical harmonic oscillator basis: We derive a formalism, the separation method, for the efficient and accurate
calculation of two-body matrix elements for a Gaussian potential in the
cylindrical harmonic-oscillator basis. This formalism is of critical importance
for Hartree-Fock and Hartree-Fock-Bogoliubov calculations in deformed nuclei
using realistic, finite-range effective interactions between nucleons. The
results given here are also relevant for microscopic many-body calculations in
atomic and molecular physics, as the formalism can be applied to other types of
interactions beyond the Gaussian form. The derivation is presented in great
detail to emphasize the methodology, which relies on generating functions. The
resulting analytical expressions for the Gaussian matrix elements are checked
for speed and accuracy as a function of the number of oscillator shells and
against direct numerical integration. | nucl-th |
Event-by-event pT fluctuations and multiparticle clusters in
relativistic heavy-ion collisions: We explore the dependence of the pT correlations in the event-by-event
analysis of relativistic heavy-ion collisions at RHIC made recently by the
PHENIX and STAR Collaborations. We point out that the observed scaling of
strength of dynamical fluctuations with the inverse number of particles can be
naturally explained by the formation of clusters. We argue that the large
magnitude of the measured covariance implies that the clusters contain at least
several particles. We also discuss whether the clusters may originate from
jets. In addition, we provide numerical estimates of correlations coming from
resonance decays and thermal clusters. | nucl-th |
Pasta structures in compact stars: We review our recent works about ``pasta'' structures following the
first-order phase transition in dense matter, which correspond to the
structured mixed phases with geometrical symmetries. Three kinds of phase
transitions at different density ranges are examined as the stages of pasta
structures: liquid-gas phase transition at subnuclear density, kaon
condensation and hadron-quark phase transition at high density. Charge density
as well as particle density is non-uniform there. A consistent treatment of the
Coulomb potential and the particle densities is presented and a peculiar role
of the Coulomb potential is elucidated: the physical picture of the Maxwell
construction will be effectively recovered. It largely influences the density
regime of pasta structures by the charge screening effect. | nucl-th |
Calculation of Doublet Capture Rate for Muon Capture in Deuterium within
Chiral Effective Field Theory: The doublet capture rate of the negative muon capture in deuterium is
calculated employing the nuclear wave functions generated from accurate
nucleon-nucleon potentials constructed at next-to-next-to-next-to-leading order
of heavy-baryon chiral perturbation theory and the weak meson exchange current
operator derived within the same formalism. All but one of the low-energy
constants that enter the calculation were fixed from pion-nucleon and
nucleon-nucleon scattering data. The low-energy constant d^R (c_D), which
cannot be determined from the purely two-nucleon data, was extracted recently
from the triton beta-decay and the binding energies of the three-nucleon
systems. The calculated values of the doublet capture rates show a rather large
spread for the used values of the d^R. Precise measurement of the doublet
capture rate in the future will not only help to constrain the value of d^R,
but also provide a highly nontrivial test of the nuclear chiral EFT framework.
Besides, the precise knowledge of the constant d^R will allow for consistent
calculations of other two-nucleon weak processes, such as proton-proton fusion
and solar neutrino scattering on deuterons, which are important for
astrophysics. | nucl-th |
Correlations between neutrons and protons near Fermi surface and
$Q_α$ of super-heavy nuclei: The shell corrections and shell gaps in nuclei are systematically studied
with the latest Weizs\"acker-Skyrme (WS4) mass model. We find that most of
asymmetric nuclei with (sub)-shell closures locate along the shell stability
line (SSL), $N=1.37Z+13.5$, which might be due to a strong correlation between
neutrons and protons near Fermi surface. The double magicity of nuclei
$^{46}$Si and $^{78}$Ni is predicted according to the corresponding shell gaps,
shell corrections and nuclear deformations. The unmeasured super-heavy nuclei
$^{296}$118 and $^{298}$120, with relatively large shell gaps and shell
corrections, also locate along the SSL, whereas the traditional magic nucleus
$^{298}$Fl evidently deviates from the line. The $\alpha$-decay energies of
super-heavy nuclei with $Z=113-126$ are simultaneously investigated by using
the WS4 model together with the radial basis function corrections. For
super-heavy nuclei with large shell corrections, the smallest $\alpha$-decay
energy for elements $Z=116$, 117 and 118 in their isotope chains locates at
$N=178$ rather than $184$. | nucl-th |
Correlations and Clustering in Dilute Matter: Nuclear systems are treated within a quantum statistical approach.
Correlations and cluster formation are relevant for the properties of warm
dense matter, but the description is challenging and different approximations
are discussed. The equation of state, the composition, Bose condensation of
bound fermions, the disappearance of bound states at increasing density because
of Pauli blocking are of relevance for different applications in astrophysics,
heavy ion collisions, and nuclear structure. | nucl-th |
The One-Boson-Exchange Potential Model Approach: A review is given of the present situation in YN scattering. Special
attention is given to the handling of SU(3) in the various meson exchanges. The
importance of the almost always ignored contribution of the Pomeron is
reiterated. | nucl-th |
Limiting Fragmentation in a Thermal Model with Flow: The property of limiting fragmentation of various observables such as
rapidity distributions ($dN/dy$), elliptic flow ($v_{2}$), average transverse
momentum ($\langle p_{T} \rangle$) etc. of charged particles is observed when
they are plotted as a function of rapidity ($y$) shifted by the beam rapidity
($y_{beam}$) for a wide range of energies from AGS to RHIC. Limiting
fragmentation (LF) is a well studied phenomenon as observed in various
collision energies and colliding systems experimentally. It is very interesting
to verify this phenomenon theoretically. We study such a phenomenon for pion
rapidity spectra using our hydrodynamic-like model where the collective flow is
incorporated in a thermal model in the longitudinal direction. Our findings
advocate the observation of extended longitudinal scaling in the rapidity
spectra of pions from AGS to lower RHIC energies, while it is observed to be
violated at top RHIC and LHC energies. Prediction of LF hypothesis for Pb+Pb
collisions at $\sqrt{s_{NN}}$=5.02 TeV is given. | nucl-th |
NN correlations and final-state interactions in (e,e'NN) reactions: After a brief overview of relevant studies on one-nucleon knockout showing
the importance of quantitatively understanding the origin of the quenched
spectroscopic factors extracted from data, attention is focussed on two-nucleon
emission as a suitable tool to investigate nucleon-nucleon correlations inside
complex nuclei. In particular, direct (e,e$'$pp) and (e,e$'$pn) reactions are
discussed, and the role of final-state interactions is studied. The influence
of the mutual interaction between the two outgoing nucleons is shown to depend
on the kinematics and on the type of the considered reaction. | nucl-th |
Nature of particles azimuthal anisotropy at low and high transverse
momenta in ultrarelativistic A+A collisions: LHC data on the correlations of the elliptic flow $v_2$ of particles at low
and high transverse momenta $p_T$ from Pb+Pb collisions at center-of-mass
energy per nucleon pair $\sqrt{s_{NN}} = 5.02$ TeV are analyzed in the
framework of the HYDJET++ model. This model includes soft and hard components
which allows to describe the region of both low and high transverse momenta.
The origin of $v_2$ values in different $p_T$ regions is investigated at
different centralities. It is shown that the experimentally observed
correlations between $v_2$ at low and high $p_T$ in peripheral lead-lead
collisions is due to correlation of particles in jets. | nucl-th |
High-precision nuclear forces from chiral EFT: State-of-the-art,
challenges and outlook: We review a new generation of nuclear forces derived in chiral effective
field theory using the recently proposed semilocal regularization method. We
outline the conceptual foundations of nuclear chiral effective field theory,
discuss all steps needed to compute nuclear observables starting from the
effective chiral Lagrangian and consider selected applications in the two- and
few-nucleon sectors. We highlight key challenges in developing high-precision
tree-body forces, such as the need to maintain consistency between two- and
many-body interactions and constraints placed by the chiral and gauge
symmetries after regularization. | nucl-th |
Conserved Charge Susceptibilities in a Chemically Frozen Hadronic Gas: In a hadronic gas with three conserved charges (electric charge, baryon
number, and strangeness) we employ the hadron resonance gas model to compute
both diagonal and off-diagonal susceptibilities. We model the effect of
chemical freeze-out in two ways: one in which all particle numbers are
conserved below the chemical freeze-out temperature and one which takes into
account resonance decays. We then briefly discuss possible implications these
results may have on two active areas of research, hydrodynamic fluctuations and
the search for the QCD critical point. | nucl-th |
Current Status of Nuclear Physics Research: In this review we discuss the current status of research in nuclear physics
which is being carried out in different centers in the World. For this purpose
we supply a short account of the development in the area which evolved over the
last 9 decades, since the discovery of the neutron. The evolution of the
physics of the atomic nucleus went through many stages as more data become
available. We briefly discuss models introduced to discern the physics behind
the experimental discoveries, such as the shell model, the collective model,
the statistical model, the interacting boson model, etc., some of these models
may be seemingly in conflict with each other, but this was shown to be only
apparent.
The richness of the ideas and abundance of theoretical models attests to the
important fact that the nucleus is a really singular system in the sense that
it evolves from two-body bound states such as the deuteron, to few-body bound
states, such as $^4$He, $^7$Li, $^9$Be etc. and up the ladder to heavier bound
nuclei containing up to more than 200 nucleons. Clearly statistical mechanics
does not work for such finite system, neither does other theories applicable to
condensed matter systems. The richness of nuclear physics stems from these
restrictions. New theories and models are presently being developed. Theories
of the structure and reactions of neutron-rich and proton-rich nuclei, called
exotic nuclei, halo nuclei, or Borromean nuclei deal with the wealth of
experimental data available in the last 35 years. Further, nuclear astrophysics
and stellar and Big Bang nucleosynthesis have become a more mature subject. Due
to limited space, this review only covers a few selected topics, mainly those
with which the authors have worked with. | nucl-th |
Medium polarization and finite size effects on the superfluidity of the
inner crust of neutron stars: The 1S0 pairing gap associated with the inner crust of a neutron star is
calculated, taking into account the coexistence of the nuclear lattice with the
sea of free neutrons (finite size effects), as well as medium polarization
effects associated with the exchange of density and spin fluctuations. Both
effects are found to be important and to lead to an overall quenching of the
pairing gap. This result, whose quantitative value is dependent on the
effective interaction used to generate the single-particle levels, is a
consequence of the balance between the attractive (repulsive) induced
interaction arising from the exchange of density (spin) modes, balance which in
turn is influenced by the presence of the protons and depends on the
single-particle structure of the system. | nucl-th |
Quarkyonic Percolation and deconfinement at finite density and number of
colors: We examine the interplay between the percolation and the deconfinement phase
transitions of Yang-Mills matter at finite temperature, quark chemical
potential $\mu_Q$ and number of colors $N_c$. We find that, whereas the
critical $N_c$ for percolation goes down with density, the critical $N_c$ for
confinement generally goes up. Because of this, Yang-Mills matter falls into
two qualitatively different regimes: the "low-$N_c$ limit", where percolation
does not occur because matter deconfines before it percolates, and the
high-$N_c$ limit, where there are three distinct phases characterizing
Yang-Mills matter at finite temperature and density: confined, deconfined and
confined but percolating matter. The latter can be thought of as the recently
conjectured "quarkyonic phase". We attempt to estimate the critical $N_c$, to
see if the percolating phase can occur in our world. We find that, while
percolation will not occur at normal nuclear density as in the large-$N_c$
limit, a sliver of the phase diagram in $N_c$, energy density and baryonic
density where percolation occurs while confinement persists is possible. We
conclude by speculating on the phenomenological properties of such percolating
"quarkyonic" matter, suggest avenues to study it quantitatively, and look for
it in experiment. | nucl-th |
The position of the quasielastic peak and electron Coulomb distortion in
(e,e') scattering: The position of the quasielastic peak for (e,e') scattering off 208-Pb
extracted from a selected data set measured at Saclay is related to a heuristic
theoretical description. An analysis of the data shows that the peak position
can be described very accurately by a simple equation in the relevant kinematic
region where a pronounced peak is observable. The simple findings result in a
concluding comment related to recent calculations concerning the Coulomb
distortion in (e,e') scattering for heavy nuclei. | nucl-th |
$\mathbf{D_s}$-Meson as Quantitative Probe of Diffusion and
Hadronization in Nuclear Collisions: The modifications of $D_s$-meson spectra in ultrarelativistic heavy-ion
collisions are identified as a quantitative probe of key properties of the hot
nuclear medium. This is enabled by the unique valence-quark content of the
$D_s$=$c\bar{s}$ which couples the well-known strangeness enhancement with the
collective-flow pattern of primordially produced charm quarks. We employ a
consistent strong-coupling treatment with hydrodynamic bulk evolution and
nonperturbative $T$-matrix interactions for both heavy-quark diffusion and
hadronization in the Quark-Gluon Plasma (QGP). A large enhancement of the $D_s$
nuclear modification factor ($R_{AA}$) at RHIC is predicted, with a remarkable
maximum of $\sim$1.5-1.8 at transverse momenta around 2 GeV/$c$. We show this
to be a direct consequence of the strong coupling of the heavy quarks to the
QGP and their hadronization via coalescence with strange quarks. We furthermore
introduce the effects of diffusion in the hadronic phase and suggest that an
increase of the $D$-meson elliptic flow compared to the $D_s$ can disentangle
the transport properties of hadronic and QGP liquids. | nucl-th |
Deformation properties with a finite range simple effective interaction: Deformed and spherical even-even nuclei are studied using a finite range
simple effective interaction within the Hartree-Fock-Bogoliubov mean field
approach. Different parameter sets of the interaction, corresponding to
different incompressibility, are constructed by varying the exponent gamma of
the density in the traditional density-dependent term. Ten of the twelve
parameters of these interactions are determined from properties of asymmetric
nuclear matter and spin polarized pure neutron matter. The two remaining
parameters are fitted to reproduce the experimental binding energies known in
620 even-even nuclei using several variants of the rotational energy
correction. The rms deviations for the binding energy depend on the value of
gamma and the way the rotational energy correction is treated but they can be
as low as 1.56 MeV, a value competitive with other renowned effective
interactions of Skyrme and Gogny type. Charge radii are compared to the
experimental values of 313 even-even nuclei and the rms deviation is again
comparable and even superior to the one of popular Skyrme and Gogny forces.
Emphasis is given to the deformation properties predicted with these
interactions by analyzing the Potential Energy Surfaces for several well
deformed nuclei and the fission barriers of some nuclei. Comparison of the
results with the experimental information, where available, as well as with the
results of the Gogny D1S force shows satisfactory agreement. | nucl-th |
Neutrino emission from Cooper pairs at finite temperatures: A brief review is given of the current state of the problem of neutrino pair
emission through neutral weak currents caused by the Cooper pairs breaking and
formation (PBF) in superfluid baryon matter at thermal equilibrium. The cases
of singlet-state pairing with isotropic superfluid gap and spin-triplet pairing
with anisotropic gap are analyzed with allowance for the anomalous weak
interactions caused by superfluidity. It is shown that taking into account the
anomalous weak interactions in both the vector and axial channels is very
important for a correct description of neutrino energy losses through the PBF
processes. The anomalous contributions lead to an almost complete suppression
of the PBF neutrino emission in spin-singlet superfluids and strong reduction
of the PBF neutrino losses in the spin-triplet superfluid neutron matter, which
considerably slows down the cooling rate of neutron stars with superfluid
cores. | nucl-th |
Effect of color superconductivity on the mass of hybrid neutron stars in
an effective model with pQCD asymptotics: The effective cold quark matter model by Alford, Braby, Paris and Reddy
(ABPR) is used as a tool for discussing the effect of the size of the pairing
gap in three-flavor (CFL) quark matter on the maximum mass of hybrid neutron
stars (NSs). This equation of state (EOS) has three parameters which we suggest
to determine by comparison with a nonlocal NJL model of quark matter in the
nonperturbative domain. We show that due to the momentum dependence of the
pairing which is induced by the nonlocality of the interaction, the effective
gap parameter in the EOS model is well approximated by a constant value
depending on the diquark coupling strength in the NJL model Lagrangian. For the
parameter $a_4=1-2\alpha_s/\pi$ a constant value below about \num{0.4} is
needed to explain hybrid stars with ${\rm M}_{\rm max} \gtrsim 2.0~{\rm
M}_\odot$, which would translate to an effective constant $\alpha_s\sim 1$. The
matching point with a running coupling at the 1-loop $\beta$ function level is
found to lie outside the range of chemical potentials accessible in NS
interiors. A dictionary is provided for translating the free parameters of the
nlNJL model to those of the ABPR model. Both models are shown to be equivalent
in the nonperturbative domain but the latter one allows to quantify the
transition to the asymptotic behaviour in accordance with perturbative QCD. We
provide constraints on parameter sets that fulfill the $2~{\rm M}_\odot$ mass
constraint for hybrid NSs, as well as the low tidal deformability constraint
from GW170817 by a softening of the EOS on the hybrid NS branch with an early
onset of deconfinement at ${\rm M}_{\rm onset}<1.4~{\rm M}_\odot$. We find that
the effective constant pairing gap should be around 100 MeV but not exceed
values of about 130 MeV because a further increase of the gap would entail a
softening of the EOS and contradict the $2~{\rm M}_\odot$ mass constraint. | nucl-th |
Approximate symmetries in nuclei and the $2νββ$-decay rate: A nonstandard method for calculating the nuclear $2\nu\beta\beta$ - decay
amplitude is proposed. The method is based on the explicit use of those
approximate symmetries of a nuclear hamiltonian, which correspond to the
operators of allowed $\beta$ -- transitions. Within the framework of the
proposed method the mentioned amplitude is calculated for a wide range of
nuclei. The model parameters used in calculations are taken from independent
data. Calculated \bb half-lifes are compared with known experimental data. | nucl-th |
Chiral electric separation effect in the quark-gluon plasma: In this paper we introduce and compute a new transport coefficient for the
quark-gluon plasma (QGP) at very high temperature. This new coefficient
$\sigma_{\chi e}$, the CESE (Chiral Electric Separation Effect) conductivity,
quantifies the amount of axial current $\vec J_A$ that is generated in response
to an externally applied electric field $e\vec E$: $\vec J_A = \sigma_{\chi e}
(e\vec E)$. Starting with rather general argument in the kinetic theory
framework, we show how a characteristic structure $\sigma_{\chi e}\propto \mu
\mu_5$ emerges, which also indicates the CESE as an anomalous transport effect
occurring only in a parity-odd environment with nonzero axial charge density
$\mu_5\neq 0$. Using the Hard-Thermal-Loop framework the CESE conductivity for
the QGP is found to be $\sigma_{\chi e} = (\#) T\frac{{\rm Tr}_{\rm
f}Q_eQ_A}{g^4\ln(1/g)} \frac{\mu\mu_5}{T^2}$ to the leading-log accuracy with
the numerical constant (#) depending on favor content, e.g. (#)$=14.5163$ for
$u,d$ light flavors. | nucl-th |
Examination of the calorimetric spectrum to determine the neutrino mass
in low-energy electron capture decay: The standard kinematic method for determining neutrino mass from the beta
decay of tritium or other isotope is to measure the shape of the electron
spectrum near the endpoint. It has been known for 30 years that a similar
distortion of the "visible energy" remaining after electron capture is caused
by neutrino mass. There has been a resurgence of interest in using this method
with 163-Ho. Recent theoretical analyses offer reassurance that there are no
significant theoretical uncertainties. We show that the situation is, however,
more complicated, and that the spectrum shape is presently not well enough
understood to permit a sensitive determination of the neutrino mass in this
way. The theoretical analyses consider only single vacancy states in the
daughter 163-Dy atom. It is necessary to consider configurations with more than
one vacancy that can be populated owing to the change in nuclear charge. The
shakeup and shakeoff theory of Carlson and Nestor is used as a basis for
estimating the population of double-vacancy states. A spectrum of satellites
associated with each primary vacancy created by electron capture is presented.
The theory of the calorimetric spectrum is more complicated than has been
described heretofore. There are numerous shakeup and shakeoff satellites
present across the spectrum, and some may be very near the endpoint. | nucl-th |
Dissipation in finite Fermi systems: We present a systematic theory of dissipation in finite Fermi systems like
nuclei and metallic clusters. This theory is based on the application of
semiclassical methods and random matrix theory to linear response of many-body
systems. The theory is developed in the approximation wherein the many-body
system can be treated as a single particle in an effective, time-dependent
mean-field. We find semiclassical expressions for energy dissipation relevant
in one-body dissipation in heavy nuclei. We also show that this energy
dissipation, related to damping of collective excitations, is irreversible. The
irreversibility is proved by our development of a quantum diffusion equation.
It may be noted that the quantum diffusion equation is derived from the von
Neumann equation and makes no assumption about the initial form of the density
operator. It is shown that, in the semiclassical limit, the quantum diffusion
equation reduces to the classical Smoluchowski equation. Further, we show that
the dissipation is a purely quantal phenomenon as it is related to the
geometric phase acquired by a single-particle wavefunction as the system
evolves in a slow-varying mean-field. It is explicitly shown that the
dissipation rate is related to the nature of dynamics and the spectrum of the
classical Liouvillian operator. Finally, we present an expression for the
viscosity tensor encountered in nuclear fission in terms of periodic orbits of
the single particle in an adiabatically deforming nucleus. | nucl-th |
Bulk Viscosity of Hot Quark Plasma from Non-Equilibrium Statistical
Operator: We provide a discussion of the bulk viscosity of two-flavor quark plasma,
described by the Nambu--Jona-Lasinio model, within the framework of
Kubo-Zubarev formalism. This discussion, which is complementary to our earlier
study, contains a new, detailed derivation of the bulk viscosity in the case of
multiple conserved charges. We also provide some numerical details of the
computation of the bulk viscosity close to the Mott transition line, where the
dissipation is dominated by decays of mesons into quarks and their inverse
processes. We close with a summary of our current understanding of this
quantity, which stresses the importance of loop resummation for obtaining the
qualitatively correct result near the Mott line. | nucl-th |
${}^{7}$Li($d$,$p$)${}^{8}$Li transfer reaction in the NCSM/RGM approach: Recently, we applied an $ab$ $initio$ method, the no-core shell model
combined with the resonating group method, to the transfer reactions with light
p-shell nuclei as targets and deuteron as the projectile. In particular, we
studied the elastic scattering of deuterium on $^7$Li and the
${}^{7}$Li($d$,$p$)${}^{8}$Li transfer reaction starting from a realistic
two-nucleon interaction. In this contribution, we review of our main results on
the ${}^{7}$Li($d$,$p$)${}^{8}$Li transfer reaction, and we extend the study of
the relevant reaction channels, by showing the dominant resonant phase shifts
of the scattering matrix. We assess also the impact of the polarization effects
of the deuteron below the breakup on the positive-parity resonant states in the
reaction. For this purpose, we perform an analysis of the convergence trend of
the phase and eigenphase shifts, with respect to the number of deuteron
pseudostates included in the model space. | nucl-th |
Correlation between the nuclear structure and reaction dynamics of
Ar-isotopes as projectile using the relativistic mean-field approach: This theoretical study is devoted to bridging the gap between the nuclear
structure and reaction dynamics and unravelling their impact on each other,
considering the neutron-rich light mass 30-60Ar isotopes. Using the
relativistic mean-field with the NL3* parameter set, several bulk properties
such as binding energies, charge radii, quadrupole deformation parameter, two
neutron separation energy, and differential two neutron separation energy with
the shell closure parameter are probed for the mentioned isotopic chain. For
validation, the RMF (NL3*) results are compared with those obtained from the
finite range droplet model (FRDM), Weizsacker-Skyrme model with WS3, WS*
parameters and the available experimental data. Most of the participating
isotopes are found to be prolate in structure and neutron shell closures are
conspicuously revealed at N=14, 20, 40 but weakly shown at N=24, 28, 34. From
our analysis, a central depletion in the nucleonic density is identified in
32Ar and 42-58Ar, indicating them as possible candidates for a semi-bubble-like
structure. Interestingly, these results are consistent with recent theoretical
and experimentally measured data. Besides, using the Glauber model, the
reaction cross-sections are determined by taking 26-48Ar as projectiles and
stable targets such as 12C, 16O, 40Ca, 90Zr, 124,132Sn, 208Pb and 304120.
Although there is no experimental evidence for the stability of 304120, it has
been predicted in Ref. [Mod. Phys. Lett. A {\bf 27}, 1250173 (2012)] as a
stable nucleus. A relatively higher cross-section value is noticed between 30Ar
and 32Ar which infers that 32Ar is the most stable isotope among the considered
chain. Moreover, we noticed that the profile of the differential cross-sections
and scattering angle are highly influenced by the mass of the target nuclei and
the magnitude of the incident energy of the projectile nucleus. | nucl-th |
Spatial orientation of the fission fragment intrinsic spins and their
correlations: New experimental and theoretical results obtained in 2021 made it acutely
clear that more than 80 years after the discovery of nuclear fission we do not
understand the generation and dynamics of fission fragment (FF) intrinsic spins
well, in particular their magnitudes, their spatial orientation, and their
correlations. The magnitude and orientation of the primary FFs have a crucial
role in defining the angular distribution and correlation between the emitted
prompt neutrons, and subsequent emission of statistical (predominantly E1) and
stretched E2 {\gamma}-rays, and their correlations with the final fission
fragments. Here we present detailed microscopic evaluations of the FF intrinsic
spins, for both even- and odd-mass FFs, and of their spatial correlations.
These point to a well-defined 3D FF intrinsic spin dynamics, characteristics
absent in semi-phenomenological studies, due to the presence of the twisting
spin modes, which artificially were suppressed in semi-phenomenological
studies. | nucl-th |
Phi meson propagation in a hot hadronic gas: The Hidden Local Symmetry Lagrangian is used to study the interactions of phi
mesons with other pseudoscalar and vector mesons in a hadronic gas at finite
temperature. We have found a significantly small phi mean free path (less than
2.4 fm at T > 170 MeV) due to large collision rates with rho mesons, kaons and
predominantly K* in spite of their heavy mass. This implies that phi mesons
produced after hadronization in relativistic heavy ion collisions will not
leave the hadronic system without scattering. The effect of these interactions
on the time evolution of the phi density in the expanding hadronic fireball is
investigated. | nucl-th |
Multiple pion production from an oriented chiral condensate: We consider an ``oriented'' chiral condensate produced in the squeezed states
of the effective field theory with time- and space-dependent pion mass
parameter. We discuss the general properties of the solution, identifying
condensate modes and determining the resulting pion distributions. The
implementation of the dynamics in the form of sudden perturbation allows us to
look for exact solutions. In the region of condensation, the dramatic increase
in pion production and charge fluctuations are demonstrated. | nucl-th |
Isospin Lattice Gas Model and Nuclear-Matter Phase Diagram and
Pressure-Volume Isotherms: We study a cubic lattice gas model for nuclear matter where each lattice site
can be either occupied, by one proton or one neutron, or unoccupied. A
nearest-neighbor interaction of the form $ - \sum_{<ij>} J_{ij}\tau_{zi}
\tau_{zj}$ is assumed. Our model is an isospin-1 Ising model, with ${\tau_z}$ =
(1,0,-1) representing respectively (proton, vacancy, neutron).
A kinetic-energy term has been included in our model. Under the
Bragg-Williams mean field approximation our model exhibits the existence of a
dense phase (liquid-like) and a rare phase (gas-like). The nuclear-matter p-v
isotherms given by our model are discussed. | nucl-th |
Properties of strange quark stars with isovector interactions: We study the properties of strange quark stars by employing a 3-flavor
Nambu-Jona-Lasinio model with both scalar-isovector and vector-isovector
interactions. Using the constraint on the vector-isoscalar interaction strength
obtained from the elliptic flow splitting between particles and their
antiparticles in relativistic heavy-ion collisions, we investigate the
dependence of the properties of strange quark stars on the vector-isovector and
the scalar-isovector interactions, and compare the results with the
state-of-art astrophysical constraints on the compact star radius and mass as
well as its tidal deformability from the GW170817 event. Results from our study
reinforce the prospect of using both heavy-ion collisions and astrophysical
observations to provide constraints on the isovector coupling strength in quark
matter and thus the quark matter equation of state as well as the QCD phase
structure at finite isospin chemical potentials. | nucl-th |
Photoprocesses for the 3H4He and 3He4He channels in the cluster
potential model: Radiative capture in the 4He3H and 4He3He channels are considered for the 7Li
and 7Be nuclei. The analysis is based on the corresponding two-cluster models.
The potentials of cluster interaction include forbidden states and are made to
be consistent with the phase shifts of elastic scattering at energies up to 20
MeV. Such an approach is shown to describe the total cross sections for
photoprocesses over the entire energy region under consideration. | nucl-th |
A shell model mass formula for exotic light nuclei: An analytic phenomenological shell model mass formula for light nuclei is
constructed., The formula takes into account the non locality of the self
consistent single particle potential and the special features of light nuclei,
namely: a) charge and mass distributions are closer to a Gaussian shape than to
the shape characteristic in medium and heavy nuclei; b) the central charge and
mass densities are larger than, and decrease towards, the "asymptotic" values
that are the reference parameters for nuclear matter; and c) after a shell
closure, the next level has a larger orbital angular momentum and a noticeably
larger mean square radius. Only then a good numerical fit is obtained with
parameters consistent with optical model analysis and empirical spin-orbit
couplings. A correlation between the "skin effect" and the symmetry dependence
of the optical potential is established. Towards the neutron drip line the
potential well depth, the spin-orbit splitting of the single particle levels
and the gap between major shells decrease, as has been observed. The ensuing
shift and contraction of the single particle level scheme may lead to: a) to
strong configuration mixing and new magic numbers, and b) the onset of the halo
effect, to avoid the expulsion of single particle levels to the continuum. | nucl-th |
Prospects of Event Shape Sorting: Event Shape Sorting is a novel method which is devised to organise a sample
of collision events in such a way, that events with similar final state
distribution of hadrons end up sorted close to each other. Such events are
likely to have evolved similarly. Thus the method allows to focus at finer
features of the collision evolution because it would allow for averages over
similar events that do not wash away these features. The algorithm is shortly
explained. We also point out the distinction of Event Shape Sorting from the
well established technique of Event Shape Engineering. | nucl-th |
The in-medium few-body problem: We are concerned with few-particle correlations in a fermionic system at
finite temperature and density. Within the many-body Green functions formalism
the description of correlations is provided by the Dyson equation approach that
leads to effective few-body equations. They contain the dominant medium
effects, which are self energy corrections and the Pauli blocking. Hence the
effective two-body interactions between quasiparticles are
momentum/energy-dependent and therefore they can be usesed in the medium
modified, momentum space, integral AGS equations for three- and four-body
systems. To investigate correlations and clusters beyond four-body, we employ,
instead, the configuration space two-variable integro-differential equations
(IDEA) for $A$-body bound systems which are based on Hyperspherical Harmonics
and the Faddeev decomposition of the wave function in two-body amplitudes. This
requires the transformation of the energy dependent two-body interactions to
equivalent local, energy independent, ones. To achieve this we use inverse
scattering techniques the resulting interactions being, on-- and (to all
practical purposes) off--shell equivalent to the energy dependent potentials.
In this way we obtain binding energy results for the 2--, 3--, 4--, and
16--particle in a medium at a finite temperature and various densities. Several
aspects of the problem are discussed and the behavior of the potential surfaces
obtained in the extreme adiabatic approximation, below and above the Mott
transition, is investigated. | nucl-th |
Neutral Pion Photoproduction on Nuclei in Baryon Chiral Perturbation
Theory: Threshold neutral pion photoproduction on light nuclei is studied in the
framework of baryon chiral perturbation theory. We obtain a general formula for
the electric dipole amplitude in the special case of neutral pion
photoproduction on a nucleus. To third order in small momenta, the amplitude is
a sum of 2- and 3-body interactions with no undetermined parameters. With
reasonable input from the single nucleon sector, our result for neutral pion
photoproduction on the deuteron is in agreement with experiment. | nucl-th |
Leading order relativistic chiral nucleon-nucleon interaction: Motivated by the successes of relativistic theories in studies of
atomic/molecular and nuclear systems and the need for a relativistic chiral
force in relativistic nuclear structure studies, we explore a new relativistic
scheme to construct the nucleon-nucleon interaction in the framework of
covariant chiral effective field theory. The chiral interaction is formulated
up to leading order with covariant power counting and a Lorentz invariant
chiral Lagrangian. We find that the relativistic scheme induces all six spin
operators needed to describe the nuclear force. A detailed investigation of the
partial wave potentials shows a better description of the $^1S_0$ and $^3P_0$
phase shifts than the leading order Weinberg approach, and similar to that of
the next-to-leading order Weinberg approach. For the other partial waves with
angular momenta $J\geq 1$, the relativistic results are almost the same as
their leading order non-relativistic counterparts. | nucl-th |
The CSM extension for description of the positive and negative parity
bands in even-odd nuclei: A particle-core Hamiltonian is used to describe the lowest parity partner
bands $K^{\pi}=1/2^{\pm}$ in
$^{219}$Ra, $^{237}$U and $^{239}$Pu, and three parity partner bands,
$K^{\pi}=1/2^{\pm}, 3/2^{\pm}, 5/2^{\pm}$, in $^{227}$Ra. The core is described
by a quadrupole and octupole boson Hamiltonian which was previously used for
the description of four positive and four negative parity bands in the
neighboring even-even isotopes. The particle-core Hamiltonian consists of four
terms: a quadrupole-quadrupole, an octupole-octupole, a spin-spin and a
rotational $\hat{I}^2$ interaction, with $\hat {I}$ denoting the total angular
momentum. The single particle space for the odd nucleon consists of three
spherical shell model states, two of positive and one of negative parity. The
product of these states with a collective deformed ground state and the
intrinsic gamma band state generate, through angular momentum projection, the
bands with $K^{\pi}=1/2^{\pm},3/2^{\pm},5/2^{\pm}$, respectively. In the space
of projected states one calculates the energies of the considered bands. The
resulting excitation energies are compared with the corresponding experimental
data as well as with those obtained with other approaches. Also, we searched
for some signatures for a static octupole deformation in the considered odd
isotopes. The calculated branching ratios in $^{219}$Ra agree quite well with
the corresponding experimental data. | nucl-th |
Electroweak Hard Photon Bremsstrahlung in Electron-Nucleon Scattering: One way to treat the infrared divergences of the electroweak
Next-to-Leading-Order (NLO) differential cross sections to parity-violating
(PV) electron-proton scattering is by adding soft-photon emission contribution.
Although more physical, the results are left with a logarithmic dependence on
the photon detector acceptance, which can only be eliminated by considering
Hard Photon Bremsstrahlung (HPB) contribution. Here we present a treatment of
HPB for PV electron-proton scattering. HPB differential cross sections for
electron-proton scattering have been computed using the experimental values of
nucleon form factors. The final results are expressed through kinematic
parameters, making it possible to apply the computed PV HPB differential cross
sections for the analysis of data of a range of current and proposed
experiments. | nucl-th |
Equation of state in the inner crust of neutron stars: discusion of the
unbound neutron states: In this paper, we calculate the stable Wigner-Seitz (W-S) cells in the inner
crust of neutron stars and we discuss the nuclear shell effects. A distinction
is done between the shell effects due to the bound states and those induced by
the unbound states, which are shown to be spurious. We then estimate the
effects of the spurious shells on the total energy and decompose it into a
smooth and a residual part. We propose a correction to the Hartree-Fock binding
energy in Wigner-Seitz cell (HF-WS). | nucl-th |
Phase diagram of dilute cosmic matter: Enhancement of nuclear pasta formation due to multi-nucleus simultaneous
collision is presented based on time-dependent density functional calculations
with periodic boundary condition. This calculation corresponds to the situation
with density lower than the known low-density existence limit of the nuclear
pasta phase. In order to evaluate the contribution from three-nucleus
simultaneous collisions inside the cosmic matter, the possibility of
multi-nucleus simultaneous collisions is examined by a systematic Monte-Carlo
calculation, and the mean free path of a nucleus is obtained. Consequently the
low-density existence limit of the nuclear pasta phase is formed to be lower
than believed up to now. | nucl-th |
Extracting the QGP viscosity from RHIC data -- a status report from
viscous hydrodynamics: We report recent progress on causal viscous hydrodynamics for relativistic
heavy ion collisions. For fixed specific shear viscosity eta/s, uncertainties
in the elliptic flow arising from initial conditions, equation of state, bulk
viscosity and numerical viscosity, and the treatment of the highly viscous
hadronic stage and freeze-out procedure are analysed. A comparison of current
viscous hydrodynamic results with experimental data yields a robust upper limit
eta/s < 5/(4pi). | nucl-th |
Dilepton production in elementary and in heavy ion reactions: We present a unified description of the vector meson and dilepton production
in elementary and in heavy ion reactions. The production of vector mesons
($\rho,\omega,\phi$) is described via the excitation of nucleon resonances
($R$). The theoretical framework is an extended vector meson dominance model
(eVMD) for resonance decays $R\longmapsto NV$ with arbitrary spin which is
covariant and kinematically complete. The eVMD includes thereby excited vector
meson states in the transition form factors. The model has successfully been
applied to $\omega$ and $\phi$ production in $p+p$ reactions. The same model is
used to describe the dilepton production in elementary reactions where
corresponding data are well reproduced. However, when the model is applied to
heavy ion reactions in the BEVALAC/SIS energy range the experimental dilepton
spectra measured by the DLS Collaboration are significantly underestimated at
small invariant masses. In view of this fact we discuss further medium effects:
One is a substantial collisional broadening of the $\rho$ and in particular of
the $\omega$ meson in the vicinity of the $\rho/\omega$-peak. The second medium
effect is the destruction of quantum interference in a dense medium. A
decoherent dilepton emission through vector mesons decays enhances the
corresponding low mass dilepton yield in heavy ion reactions and improves the
agreement with existing data. | nucl-th |
Numerical Simulation of the Hydrodynamical Combustion to Strange Quark
Matter: We present results from a numerical solution to the burning of neutron matter
inside a cold neutron star into stable (u,d,s) quark matter. Our method solves
hydrodynamical flow equations in 1D with neutrino emission from weak
equilibrating reactions, and strange quark diffusion across the burning front.
We also include entropy change due to heat released in forming the stable quark
phase. Our numerical results suggest burning front laminar speeds of 0.002-0.04
times the speed of light, much faster than previous estimates derived using
only a reactive-diffusive description. Analytic solutions to hydrodynamical
jump conditions with a temperature dependent equation of state agree very well
with our numerical findings for fluid velocities. The most important effect of
neutrino cooling is that the conversion front stalls at lower density (below
approximately 2 times saturation density). In a 2-dimensional setting, such
rapid speeds and neutrino cooling may allow for a flame wrinkle instability to
develop, possibly leading to detonation. | nucl-th |
Parity-Violating Interaction Effects in the np System: We investigate parity-violating observables in the np system, including the
longitudinal asymmetry and neutron-spin rotation in np elastic scattering, the
photon asymmetry in np radiative capture, and the asymmetries in deuteron
photo-disintegration d(gamma,n)p in the threshold region and
electro-disintegration d(e,e`)np in quasi-elastic kinematics. To have an
estimate of the model dependence for the various predictions, a number of
different, latest-generation strong-interaction potentials--Argonne v18, Bonn
2000, and Nijmegen I--are used in combination with a weak-interaction potential
consisting of pi-, rho-, and omega-meson exchanges--the model known as DDH. The
complete bound and scattering problems in the presence of parity-conserving,
including electromagnetic, and parity-violating potentials is solved in both
configuration and momentum space. The issue of electromagnetic current
conservation is examined carefully. We find large cancellations between the
asymmetries induced by the parity-violating interactions and those arising from
the associated pion-exchange currents. In the np capture, the model dependence
is nevertheless quite small, because of constraints arising through the Siegert
evaluation of the relevant E1 matrix elements. In quasi-elastic electron
scattering these processes are found to be insignificant compared to the
asymmetry produced by gamma-Z interference on individual nucleons. | nucl-th |
Relativistic predictions of polarization phenomena in exclusive
proton-induced proton-knockout reactions: Whereas a nonrelativistic distorted wave model fails to quantitatively
describe analyzing power data for exclusive proton-induced proton-knockout from
the 3s_{1/2} state in Pb-208 at 202 MeV, the corresponding relativistic
prediction provides a perfect description, thus suggesting that the Dirac
equation is the more appropriate underlying dynamical equation. We check the
consistency of this rsult by comparing predictions for both dynamical models to
new high resolution data for 3s_{1/2} knockout in Pb-208 at a higher incident
energy of 392 MeV. | nucl-th |
Initial State Energy Loss Dependence of J/Psi and Drell-Yan in
Relativistic Heavy Ion Collisions: We present a Glauber-based study of J/Psi and Drell-Yan yields in
nucleus-nucleus collisions. Using this approach, we have investigated the
impact of energy loss by the colliding nuclei on observed yields and transverse
momentum spectra of J/Psi and Drell-Yan. These studies permit an assessment of
the importance of initial state energy loss in relation to "anomalous" J/Psi
suppression. | nucl-th |
Photon bremsstrahlung and diffusive broadening of a hard jet: The photon bremsstrahlung rate from a quark jet produced in deep-inelastic
scattering (DIS) off a large nucleus is studied in the collinear limit. The
leading medium-enhanced higher twist corrections which describe the multiple
scattering of the jet in the nucleus are re-summed to all orders of twist. The
propagation of the jet in the absence of further radiative energy loss is shown
to be governed by a transverse momentum diffusion equation. We compute the
final photon spectrum in the limit of soft photons, taking into account the
leading and next-to-leading terms in the photon momentum fraction y. In this
limit, the photon spectrum in a physical gauge is shown to arise from two
interfering sources: one where the initial hard scattering produces an
off-shell quark which immediately radiates the photon and then undergoes
subsequent soft re-scattering; alternatively the quark is produced on-shell and
propagates through the medium until it is driven off-shell by re-scattering and
radiates the photon. Our result has a simple formal structure as a product of
the photon splitting function, the quark transverse momentum distribution
coming from a diffusion equation and a dimensionless factor which encodes the
effect of the interferences encountered by the propagating quark over the
length of the medium. The destructive nature of such interferences in the small
y limit are responsible for the origin of the Landau-Pomeranchuck-Migdal (LPM)
effect. Along the way we also discuss possible implications for quark jets in
hot nuclear matter. | nucl-th |
Equilibrium and non-equilibrium effects in relativistic heavy ion
collisions: The hypothesis of local equilibrium (LE) in relativistic heavy ion collisions
at energies from AGS to RHIC is checked in the microscopic transport model. We
find that kinetic, thermal, and chemical equilibration of the expanding
hadronic matter is nearly reached in central collisions at AGS energy for $t
\geq 10$ fm/$c$ in a central cell. At these times the equation of state may be
approximated by a simple dependence $P \cong (0.12-0.15) \epsilon$. Increasing
deviations of the yields and the energy spectra of hadrons from statistical
model values are observed for increasing bombarding energies. The origin of
these deviations is traced to the irreversible multiparticle decays of strings
and many-body $(N \geq 3)$ decays of resonances. The violations of LE indicate
that the matter in the cell reaches a steady state instead of idealized
equilibrium. The entropy density in the cell is only about 6% smaller than that
of the equilibrium state. | nucl-th |
Nucleon-Nucleon Effective Field Theory Without Pions: Nuclear processes involving momenta much below the mass of the pion may be
described by an effective field theory in which the pions do not appear as
explicit degrees of freedom. The effects of the pion and all other virtual
hadrons are reproduced by the coefficients of gauge-invariant local operators
involving the nucleon field. Nucleon-nucleon scattering phase shift data
constrains many of the coefficients that appear in the effective Lagrangean but
at some order in the expansion coefficients enter that must be constrained by
other observables. We compute several observables in the two-nucleon sector up
to next-to-next-to leading order in the effective field theory without pions,
or to the order at which a counterterm involving four-nucleon field operators
is encountered. Effective range theory is recovered from the effective field
theory up to the order where relativistic corrections enter or where
four-nucleon-external current local operators arise. For the deuteron magnetic
moment, quadrupole moment and the $np\to d\gamma$ radiative capture cross
section a four-nucleon-one-photon counterterm exists at next-to-leading order.
The electric polarizability and electric charge form factor of the deuteron are
determined up to next-to-next-to-leading order, which includes the first
appearance of relativistic corrections. | nucl-th |
Phase Transition Study meets Machine Learning: In recent years, machine learning (ML) techniques have emerged as powerful
tools for studying many-body complex systems, and encompassing phase
transitions in various domains of physics. This mini review provides a concise
yet comprehensive examination of the advancements achieved in applying ML to
investigate phase transitions, with a primary focus on those involved in
nuclear matter studies. | nucl-th |
Coulomb screening correction to the $Q$ value of the triple alpha
process in thermal plasmas: The triple alpha reaction is a key to $^{12}$C production and is expected to
occur in weakly-coupled, thermal plasmas as encountered in normal stars. We
investigate how Coulomb screening affects the structure of a system of three
alpha particles in such a plasma environment by precise three-body calculations
within the Debye-H\"uckel approximation. A three-alpha model that has the
Coulomb interaction modified in the Yukawa form is employed. Precise three-body
wave functions are obtained by a superposition of correlated Gaussian bases
with the aid of the stochastic variational method. The energy shifts of the
Hoyle state due to the Coulomb screening are obtained as a function of the
Debye screening length. The results, which automatically incorporate the finite
size effect of the Hoyle state, are consistent with the conventional result
based on the Coulomb correction to the chemical potentials of ions that are
regarded as point charges in a weakly-coupled, thermal plasma. We have given a
theoretical basis to the conventional point-charge approach to the Coulomb
screening problem relevant for nuclear reactions in normal stars by providing
the first evaluation of the Coulomb corrections to the $Q$ value of the triple
alpha process that produces a finite size Hoyle state. | nucl-th |
Measuring charge fluctuations in high-energy nuclear collisions: Various measures of charge fluctuations in heavy-ion collisions are
discussed. Advantages of the Phi-measure are demonstrated and its relation to
other fluctuation measures is established. To get the relation, Phi is
expressed through the moments of multiplicity distribution. We study how the
measures act in the case of a `background' model which represents the classical
hadron gas in equilibrium. The model assumes statistical particle production
constrained by charge conservation. It also takes into account both the effect
of incomplete experimental apparatus acceptance and that of tracking
inefficiency. The model is shown to approximately agree with the PHENIX and
preliminary STAR data on the electric charge fluctuations. Finally,
`background-free' measures are discussed. | nucl-th |
Hyperons, deconfinement and the speed of sound in neutron stars: The effects of the presence of hyperons and a phase transition to deconfined
quark matter on the speed of sound in neutron stars is investigated. For this
purpose a composite description consisting of a model of the covariant field
theory of hadrons and one for unbound quarks are used. A phase transition with
continuous and monotonous variation of the equation of state is assumed. The
predictions are contrasted with recent observational data on isolated neutron
stars as well as on binary systems. Only one candidate is finally obtained from
six different descriptions. According to the present calculations the onset of
the hyperons causes the equilibrium speed of sound to exceed the conformal
limit. Qualitative agreement with recent work about the influence of the speed
of sound on the g-modes of oscillation in neutron stars is obtained. | nucl-th |
Supernarrow Dibaryons and Exotic Baryons with Small Masses: A searche for supernarrow dibaryons (SND) and exotic baryons with small
masses is reviewed. As a result of the study of the reaction pd->p+pX_1, three
narrow peaks at M_{pX_1}=1904, 1926, and 1942 MeV have been observed. The
analysis of the angular distributions of the protons from the decay of the pX_1
states showed that the peaks found can be explained as a manifestation of the
isovector SNDs, the decay of which into two nucleons is forbidden by the Pauli
exclusion principle. The observation of the peaks in the missing mass M_{X_1}
spectra at 966, 986, and 1003 MeV is an additional indication that the
dibaryons found are the SNDs. The possible interpretation of these peaks in the
M_{X_1} mass spectra and peaks observed in the reaction pp->pi^+pX at M_X=1004,
1044, and 1094 MeV as new exotic baryon states with small masses is discussed.
The mass equation has been constructed which is used to calculate the masses
and determine parities of the exotic baryons. The obtained values of the masses
are in a good agreement with the experimental data. Two new exotic baryon
states bellow the \pi production threshold have been predicted. | nucl-th |
Faddeev approach to confined three-quark problems: We propose a method that allows for the efficient solution of the three-body
Faddeev equations in the presence of infinitely rising confinement
interactions. Such a method is useful in calculations of nonrelativistic and
especially semirelativistic constituent quark models. The convergence of the
partial wave series is accelerated and possible spurious contributions in the
Faddeev components are avoided. We demonstrate how the method works with the
example of the Goldstone-boson-exchange chiral quark model for baryons. | nucl-th |
Direct Reactions with Exotic Nuclei: We discuss recent work on Coulomb dissociation and an effective-range theory
of low-lying electromagnetic strength of halo nuclei. We propose to study
Coulomb dissociation of a halo nucleus bound by a zero-range potential as a
homework problem. We study the transition from stripping to bound and unbound
states and point out in this context that the Trojan-Horse method is a suitable
tool to investigate subthreshold resonances. | nucl-th |
Study of nuclear dynamics of neutron-rich colliding pair at energy of
vanishing flow: We study nuclear dynamics at the energy of vanishing flow of neutron-rich
systems having N/Z ratio 1.0, 1.6 and 2.0 throughout the mass range at semi
central colliding geometry. In particular we study the behavior of average and
maximum density with N/Z dependence of the system. | nucl-th |
Flow harmonics from self-consistent particlization of a viscous fluid: The quantitative extraction of quark-gluon plasma (QGP) properties from
heavy-ion data, such as its specific shear viscosity $\eta /s$, typically
requires comparison to viscous hydrodynamic or "hybrid" hydrodynamics+transport
simulations. In either case, one has to convert the fluid to hadrons, yet
without additional theory input the conversion is ambiguous for dissipative
fluids. Here, shear viscous phase-space corrections calculated using linearized
transport theory are applied in Cooper-Frye freezeout to quantify the effects
on anisotropic flow coefficients $v_n(p_T)$ at both RHIC and LHC energies.
Expanding upon our previous flow harmonics studies [1,2], we calculate pion and
proton $v_2(p_T)$, $v_4(p_T)$, and $v_6(p_T)$. Unlike in Ref. [1], we
incorporate a hadron gas that is chemically frozen below a temperature of 175
MeV, and use hypersurfaces from realistic viscous hydrodynamic simulations.
With additive quark model cross sections and relative phase-space corrections
with $p^{3/2}$ momentum dependence, rather than the quadratic Grad form, we
find at moderately high transverse momentum noticeably higher $v_4(p_T)$ and
$v_6(p_T)$ for protons than for pions. In addition, the value of $\eta /s$
deduced from elliptic flow data differs by nearly 50\% from the value extracted
using the naive "democratic Grad" form of freeze-out distributions. To
facilitate the use of the self-consistent viscous corrections calculated here
in hydrodynamic and hybrid calculations, we also present convenient
parameterizations of the corrections for the various hadron species (cf. Table
I). | nucl-th |
Analysis of previous microscopic calculations for second $0^+$ state in
$^{12}$C in terms of 3-alpha particle Bose-condensed state: The wave function of the second $0^+$ state of $^{12}$C which was obtained
long time ago by solving the microscopic 3$\alpha$ problem is shown to be
almost completely equivalent to the wave function of the 3$\alpha$ condensed
state which has been proposed recently by the present authors. This equivalence
of the wave functions is shown to hold in two cases where different effective
two-nucleon forces are adopted. This finding gives strong support for
interpreting the second $0^+$ state of $^{12}$C which is the key state for the
synthesis of $^{12}$C in stars ('Hoyle' state), and which is one of the typical
mysterious $0^+$ states in light nuclei, as a gas-like structure of three
$\alpha$ particles, Bose-condensed into an identical s-wave function. | nucl-th |
Density functional approaches to collective phenomena in nuclei:
Time-dependent density-functional theory for perturbative and
non-perturbative nuclear dynamics: We present the basic concepts and our recent developments in the density
functional approaches with the Skyrme functionals for describing nuclear
dynamics at low energy. The time-dependent density-functional theory (TDDFT) is
utilized for the exact linear response with an external perturbation. For
description of collective dynamics beyond the perturbative regime, we present a
theory of a decoupled collective submanifold to describe for a slow motion
based on the TDDFT. Selected applications are shown to demonstrate the quality
of their performance and feasibility. Advantages and disadvantages in the
numerical aspects are also discussed. | nucl-th |
Non-empirical shape dynamics of heavy nuclei with multi-task deep
learning: A microscopic description of nuclear fission represents one of the most
challenging problems in nuclear theory. While phenomenological coordinates,
such as multipole moments, have often been employed to describe fission, it is
not obvious whether these parameters fully reflect the shape dynamics of
interest. We here propose a novel method to extract collective coordinates,
which are free from phenomenology, based on multi-task deep learning in
conjunction with a density functional theory (DFT). To this end, we first
introduce randomly generated external fields to a Skyrme-EDF and construct a
set of nuclear number densities and binding energies for deformed states of
${}^{236}$U around the ground state. By training a neural network on such
dataset with a combination of an autoencoder and supervised learning, we
successfully identify a two-dimensional latent variables that accurately
reproduce both the energies and the densities of the original Skyrme-EDF
calculations, within a mean absolute error of 113 keV for the energies. In
contrast, when multipole moments are used as latent variables for training in
constructing the decoders, we find that the training data for the binding
energies are reproduced only within 2 MeV. This implies that conventional
multipole moments do not provide fully adequate variables for a shape dynamics
of heavy nuclei. | nucl-th |
A study of the phase transition in the usual statistical model for
nuclear multifragmentation: We use a simplified model which is based on the same physics as inherent in
most statistical models for nuclear multifragmentation. The simplified model
allows exact calculations for thermodynamic properties of systems of large
number of particles. This enables us to study a phase transition in the model.
A first order phase transition can be tracked down. There are significant
differences between this phase transition and some other well-known cases. | nucl-th |
Particle Interferometry for Relativistic Heavy-Ion Collisions: In this report we give a detailed account on Hanbury Brown/Twiss (HBT)
particle interferometric methods for relativistic heavy-ion collisions. These
exploit identical two-particle correlations to gain access to the space-time
geometry and dynamics of the final freeze-out stage. The connection between the
measured correlations in momentum space and the phase-space structure of the
particle emitter is established, both with and without final state
interactions. Suitable Gaussian parametrizations for the two-particle
correlation function are derived and the physical interpretation of their
parameters is explained. After reviewing various model studies, we show how a
combined analysis of single- and two-particle spectra allows to reconstruct the
final state of relativistic heavy-ion collisions. | nucl-th |
Does Σ-Σ-αForm a Quasi-Bound State?: We have investigated the possible existence of a quasi-bound state for the
\Sigma -\Sigma -\alpha system in the framework of Faddeev calculations. We are
particularly interested in the state of total iso-spin T=2, since for an inert
\alpha particle there is no strong conversion to \Xi -N-\alpha or \Lambda
-\Lambda -\alpha possible. A \Sigma -\alpha optical potential based on Nijmegen
model D and original \Sigma -\Sigma interactions of the series of Nijmegen
potentials NSC97 as well a simulated Gaussian type versions thereof are used.
Our investigation of the \Sigma -\Sigma -\alpha system leads to a quasi bound
state where, depending on the potential parameters, the energy ranges between
-1.4 and -2.4 MeV and the level width is about 0.2MeV. | nucl-th |
Repulsive force by vector mesons and quark-hadron phase transition: Using a phenomenological model with vector-type interactions, we discuss a
role of repulsive force in the quark-hadron phase transition at high density.
For realization of the quark phase at high density, strong vector coupling is
needed in the hadron phase, while it is forbidden in the quark phase. For the
quark-phase, a NJL-type model with a multi-quark interaction is investigated.
We show that, in this model, the restoration of chiral symmetry decreases
effective vector coupling and the quark phase is realized at high density, even
if we have strong vector coupling at low density. In this model, the strong
coupling in the hadron phase is induced by the chiral symmetry breaking. | nucl-th |
Realistic medium-averaging in radiative energy loss: We present results from a jet energy loss calculation using the
Gyulassy-Levai-Vitev (GLV) formalism and bulk medium evolution from the
covariant transport model MPC. At both RHIC and LHC energies we find that
realistic transverse expansion strongly reduces elliptic flow at high pT
compared to calculations with transversely 'frozen' profiles. We argue that
this is a generic feature of GLV energy loss. Transverse expansion also leads
to stronger high-pT suppression, while fluctuations in energy loss with the
location of scattering centers weaken the suppression. But, unlike the
reduction of v2, these effects nearly disappear once alpha_s is adjusted to
reproduce R_AA in central collisions. | nucl-th |
Tensor correlations in $^4$He and $^8$Be with antisymmetrized quasi
cluster model: In this paper, we extend the framework of improved version of simplified
method to take into account the tensor contribution ($i$SMT) and propose
AQCM-T, tensor version of antisymmetrized quasi cluster model (AQCM). Although
AQCM-T is phenomenological, we can treat the $^3S$-$^3D$ coupling in the
deuteron-like $T=0$ $NN$-pair induced by the tensor interaction in a very
simplified way, which allows us to proceed to heavier nuclei. Also we propose a
new effective interaction, V2m, where the triplet-even channel of the Volkov
No.2 interaction is weakened to 60% so as to reproduce the binding energy of
$^4$He after including the tensor term of a realistic interaction. Using AQCM-T
and the new interaction, the significant tensor contribution in $^4$He is
shown, which is almost comparable the central interaction, where $D$-state
mixes by 8% to the major $S$-state. The AQCM-T model with the new interaction
is also applied to $^8$Be. It is found that the tensor suppression gives
significant contribution to the short-range repulsion between two {\alpha}
clusters. | nucl-th |
Fluctuations of rare particles as a measure of chemical equilibration: We calculate the time evolution of fluctuations for rare particles such as
e.g. kaons in 1 AGeV or charmonium in 200 AGeV heavy ion collisions. We find
that these fluctuations are a very sensitive probe of the degree of chemical
equilibration reached in these collisions. Furthermore, measuring the second
factorial moment the size of the initial population can be determined. | nucl-th |
Excited Baryons and Chiral Symmetry Breaking of QCD: N* masses in the spin-1/2 and spin-3/2 sectors are computed using two
non-perturbative methods: lattice QCD and QCD sum rules. States with both
positive and negative parity are isolated via parity projection methods. The
basic pattern of the mass splittings is consistent with experiments. The mass
splitting within the same parity pair is directly linked to the chiral symmetry
breaking QCD. | nucl-th |
Two-body dissipation effects on synthesis of superheavy elements: To investigate the two-body dissipation effects on the synthesis of
superheavy elements, we calculate low-energy collisions of the $N=50$ isotones
($^{82}$Ge, $^{84}$Se, $^{86}$Kr and $^{88}$Sr) on $^{208}$Pb using the
time-dependent density-matrix theory (TDDM). TDDM is an extension of the
time-dependent Hartree-Fock (TDHF) theory and can determine the time evolution
of one-body and two-body density matrices. Thus TDDM describes both one-body
and two-body dissipation of collective energies. It is shown that the two-body
dissipation may increase fusion cross sections and enhance the synthesis of
superheavy elements. | nucl-th |
Radiative 3He(2H,g)5Li capture at low deuterium energy: The results are presented on the total cross sections, astrophysical
S-factor, reaction rate of the deuteron radiative capture on 3He at the
temperatures from 0.03 up to 3 T9 calculated in the framework of the potential
cluster model with the forbidden states coming from the classification of the
orbital states by the Young diagrams. Within the used model and exploited Young
diagram classification made it possible to reproduce the general features of
the available experimental data on the cross section and reconstructed
astrophysical S-factor in the energy range from 200 keV up to 1.4 MeV. The
parametrization of the obtained reaction rate has been found and been compared
with some other actual reactions with light clusters. | nucl-th |
Ab Initio Description of p-Shell Hypernuclei: We present the first ab initio calculations for p-shell single-Lambda
hypernuclei. For the solution of the many-baryon problem, we develop two
variants of the no-core shell model with explicit $\Lambda$ and $\Sigma^+$,
$\Sigma^0$, $\Sigma^-$ hyperons including $\Lambda$-$\Sigma$ conversion,
optionally supplemented by a similarity renormalization group transformation to
accelerate model-space convergence. In addition to state-of-the-art chiral two-
and three-nucleon interactions, we use leading-order chiral hyperon-nucleon
interactions and a recent meson-exchange hyperon-nucleon interaction. We
validate the approach for s-shell hypernuclei and apply it to p-shell
hypernuclei, in particular to $^7_\Lambda$Li, $^9_\Lambda$Be and
$^{13}_\Lambda$C. We show that the chiral hyperon-nucleon interactions provide
ground-state and excitation energies that agree with experiment within the
cutoff dependence. At the same time we demonstrate that hypernuclear
spectroscopy provides tight constraints on the hyperon-nucleon interactions and
we discuss the impact of induced hyperon-nucleon-nucleon interactions. | nucl-th |
Propagation of uncertainties in the nuclear DFT models: Parameters of the nuclear density functional theory (DFT) models are usually
adjusted to experimental data. As a result they carry certain theoretical
error, which, as a consequence, carries out to the predicted quantities. In
this work we address the propagation of theoretical error, within the nuclear
DFT models, from the model parameters to the predicted observables. In
particularly, the focus is set on the Skyrme energy density functional models. | nucl-th |
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