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Deduction of the quantum numbers of low-lying states of 4-nucleon
systems based on symmetry: The inherent nodal structures of the wavefunctions of 4-nucleon systems have
been investigated. The quantum numbers of the excited states (resonances) have
been deduced. It was found that all the T=0 even-parity resonances are
dominated by {2,1,1} component with L=1, all the T=0 odd-parity resonances are
dominated by {3,1} component with L=1, and all the T=1 odd-parity resonances
are also dominated by {3,1} component with L=1. The understanding of the
inherent nodal structure is found to be crucial to a systematic understanding
of the spectrum. | nucl-th |
Addendum: Triton and hypertriton binding energies calculated from SU_6
quark-model baryon-baryon interactions: Previously we calculated the binding energies of the triton and hypertriton,
using an SU_6 quark-model interaction derived from a resonating-group method of
two baryon clusters. In contrast to the previous calculations employing the
energy-dependent interaction kernel, we present new results using a
renormalized interaction, which is now energy independent and reserves all the
two-baryon data. The new binding energies are slightly smaller than the
previous values. In particular the triton binding energy turns out to be 8.14
MeV with a charge-dependence correction of the two-nucleon force, 190 keV,
being included. This indicates that about 350 keV is left for the energy which
is to be accounted for by three-body forces. | nucl-th |
A new Perspective on the Scalar meson Puzzle, from Spontaneous Chiral
Symmetry Breaking Beyond BCS: We introduce coupled channels of Bethe-Salpeter mesons both in the boundstate
equation for mesons and in the mass gap equation for chiral symmetry.
Consistency is insured by the Ward Identities for axial currents, which
preserve the Goldstone boson nature of the pion and prevents a systematic shift
of the hadron spectrum. We study the decay of a scalar meson coupled to a pair
of pseudoscalars. We also show that coupled channels reduce the breaking of
chiral symmetry, with the same Feynman diagrams that appear in the coupling of
a scalar meson to a pair of pseudoscalar mesons. Exact calculations are
performed in a particular confining quark model, where we find that the
groundstate $I=0, ^3P_0 q \bar q$ meson is the f_0(980) with a partial decay
width of 40MeV. We also find a 30% reduction of the chiral condensate due to
coupled channels. | nucl-th |
A new Microscopic Model for $J/ψ$ Production in Heavy Ion Collisions: We present a new model for the creation of \J mesons in ultrarelativistic
heavy ion collisions, which allows to follow the individual heavy quarks from
their creation until the detector through the Quark Gluon Plasma (QGP), which
is formed in these collisions and described by the EPOS2 event generator. The
\cc quarks interact via a potential, based on results of lattice gauge
calculations. The annihilation and creation of \J is described by a density
matrix approach whose time evolution is studied in the expanding system. The
comparison with PbPb data at $\sqrt{s}$=5.02 TeV shows that this model can
describe simultaneously the nuclear modification factor $R_{AA}$ and the
elliptic flow $v_2$ of the \J at low transverse momen | nucl-th |
Quark Models of Baryon Masses and Decays: The application of quark models to the spectra and strong and electromagnetic
couplings of baryons is reviewed. This review focuses on calculations which
attempt a global description of the masses and decay properties of baryons,
although recent developments in applying large N_c QCD and lattice QCD to the
baryon spectrum are described. After outlining the conventional
one-gluon-exchange picture, models which consider extensions to this approach
are contrasted with dynamical quark models based on Goldstone-boson exchange
and an algebraic collective-excitation approach. The spectra and
electromagnetic and strong couplings that result from these models are compared
with the quantities extracted from the data and each other, and the impact of
various model assumptions on these properties is emphasized. Prospects for the
resolution of the important issues raised by these comparisons are discussed. | nucl-th |
$ΛΛ$ Interaction in a Nuclear Density Functional Theory and
Hyperon Puzzle of the Neutron Star: A Skyrme-type effective potential is determined to describe the interaction
between $\Lambda$ hyperons in nuclear medium. Experimental data of the binding
energies of the double-$\Lambda$ ($\Lambda\Lambda$) nuclei with mass numbers
$A=10$--$13$ are used to fit the parameters of the $\Lambda\Lambda$
interaction. As a result of the fitting, we obtain eight different sets of the
$\Lambda\Lambda$ interaction parameters, which reproduces the input data within
5\% deviation from the experimental data on average. The eight $\Lambda\Lambda$
interactions are plugged in the calculation of the heavier $\Lambda\Lambda$
nuclei and the neutron star equation of state to explore the issue of hyperon
puzzle. We found that the $\Lambda\Lambda$ interaction, specifically, p-wave
interaction makes the equation of state stiff enough that the maximum mass of
the neutron star can be as large as, or above $2\;M_\odot$. | nucl-th |
Properties of effective interactions and the excitation of 6- states in
28Si: Cross-section and analyzing power data from (p,p') scattering to the 6-
states at 11.58 and 14.35 MeV in 28Si, taken with energies of 80, 100, 134, and
180 MeV protons, have been analyzed using a distorted wave approximation with
microscopically defined wave functions. The results, taken in conjunction with
an analysis of an M6 electron scattering form factor, suggest that the two
states exhaust respectively, ~50% and ~60% of the strengths of isoscalar and
isovector particle-hole excitations from the ground state. The energy variation
of data also suggests that the non-central components of the effective
interactions at 80 and 100 MeV may need to be enhanced. | nucl-th |
Dynamic Microscopic Theory of Fusion Using DC-TDHF: The density-constrained time-dependent Hartree-Fock (DC-TDHF) theory is a
fully microscopic approach for calculating heavy-ion interaction potentials and
fusion cross sections below and above the fusion barrier. We discuss recent
applications of DC-TDHF method to fusion of light and heavy systems. | nucl-th |
Heavy quark diffusion from coherent color fields in relativistic
heavy-ion collisions: The diffusion coefficients of heavy quarks from the coherent color
electromagnetic fields which are generated in the early stage of relativistic
heavy-ion collisions are calculated at midrapidity, and compared with those
obtained from collisions within a thermalized quark-gluon plasma. The coherent
color fields are modeled such that they are initially longitudinal and then
become isotropic. We found that the diffusion coefficients from the coherent
color fields are larger than those from collisions except for very fast heavy
quarks, and the color fields are less effective for heavy-quark energy loss.
The importance of coherent color fields for heavy-quark diffusion decreases as
energy density decreases. | nucl-th |
Dynamic nature at the QCD Critical End Point: This paper has been withdrawn by the authors due to inadequate arguments. | nucl-th |
A short course on Relativistic Heavy Ion Collisions: Some ideas/concepts in relativistic heavy ion collisions are discussed. To a
large extent, the discussions are non-comprehensive and non-rigorous. It is
intended for fresh graduate students of Homi Bhabha National Institute, Kolkata
Centre, who are intending to pursue career in theoretical /experimental high
energy nuclear physics. Comments and criticisms will be appreciated. | nucl-th |
The Possible Origin and Implications of the Shoulder in Reactor Neutrino
Spectra: We analyze within a nuclear database framework the shoulder observed in the
antineutrino spectra in current reactor experiments. We find that the
ENDF/B-VII.1 database predicts that the antineutrino shoulder arises from an
analogous shoulder in the aggregate fission beta spectra. In contrast, the
JEFF-3.1.1 database does not predict a shoulder for two out of three of the
modern reactor neutrino experiments, and the shoulder that is predicted by
JEFF-3.1.1 arises from $^{238}$U. We consider several possible origins of the
shoulder, and find possible explanations. For example, there could be a problem
with the measured aggregate beta spectra, or the harder neutron spectrum at a
light-water power reactor could affect the distribution of beta-decaying
isotopes. In addition to the fissile actinides, we find that $^{238}$U could
also play a significant role in distorting the total antineutrino spectrum.
Distinguishing these and quantifying whether there is an anomaly associated
with measured reactor neutrino signals will require new short-baseline
experiments, both at thermal reactors and at reactors with a sizable epithermal
neutron component. | nucl-th |
One-loop corrections to omega photoproduction near threshold: One-loop corrections to $\omega$ photoproduction near threshold have been
investigated by using the approximation that all relevant transition amplitudes
are calculated from the tree diagrams of effective Lagrangians. With the
parameters constrained by the data of $\gamma N \to \pi N$, $\gamma N \to \rho
N$, and $\pi N \to \omega N$ reactions, it is found that the one-loop effects
due to the intermediate $\pi N$ and $\rho N$ states can significantly change
the differential cross sections and spin observables. The results from this
exploratory investigation suggest strongly that the coupled-channel effects
should be taken into account in extracting reliable resonance parameters from
the data of vector meson photoproduction in the resonance region. | nucl-th |
A possible explanation for AMS doubly charged anomalous event: By means of the quark mass density-dependent model, a possible explanation
for the doubly charged anomalous event with Z/A=0.114 reported by Alpha
Magnetic Spectrometer Collaboration is given. It seems a strangelet. The
composition, radius and mean lifetime of this strangelet are given. | nucl-th |
A microscopic equation of state for neutron-rich matter and its effect
on neutron star properties: Chapter prepared for the book "Astrophysics", ISBN 979-953-307-389-6, INTECH
Publishers (in press). | nucl-th |
A Combined Solution of the Schwinger-Dyson and Bethe-Salpeter Equations
for Mesons as $q\bar q$ Bound States: The mass spectrum of heavy pseudoscalar mesons, described as quark-antiquark
bound systems, is considered within the Bethe-Salpeter formalism with momentum
dependent masses of the constituents. This dependence is found by solving the
Schwinger-Dyson equation for quark propagators in rainbow-ladder approximation.
Such an approximation is known to provide both a fast convergence of numerical
methods and accurate results for lightest mesons. However, as the meson mass
increases, the method becomes less stable and special attention must be devoted
to details of numerical means of solving the corresponding equations. We focus
on the pseudoscalar sector and show that our numerical scheme describes fairly
accurately the $\pi$, $K$, $D$, $D_s$ and $\eta_c$ ground states. Excited
states are considered as well. Our calculations are directly related to the
future physics programme at FAIR. | nucl-th |
Signatures of three-nucleon interactions in few-nucleon systems: Recent experimental results in three-body systems have unambiguously shown
that calculations based only on nucleon-nucleon forces fail to accurately
describe many experimental observables and one needs to include effects which
are beyond the realm of the two-body potentials. This conclusion owes its
significance to the fact that experiments and calculations can both be
performed with a high accuracy. In this review, both theoretical and
experimental achievements of the past decade will be underlined. Selected
results will be presented. The discussion on the effects of the three-nucleon
forces is, however, limited to the hadronic sector. It will be shown that
despite the major successes in describing these seemingly simple systems, there
are still clear discrepancies between data and the state-of-the-art
calculations. | nucl-th |
Variational Monte Carlo calculations of $\mathbf{A\leq 4}$ nuclei with
an artificial neural-network correlator ansatz: The complexity of many-body quantum wave functions is a central aspect of
several fields of physics and chemistry where non-perturbative interactions are
prominent. Artificial neural networks (ANNs) have proven to be a flexible tool
to approximate quantum many-body states in condensed matter and chemistry
problems. In this work we introduce a neural-network quantum state ansatz to
model the ground-state wave function of light nuclei, and approximately solve
the nuclear many-body Schr\"odinger equation. Using efficient stochastic
sampling and optimization schemes, our approach extends pioneering applications
of ANNs in the field, which present exponentially-scaling algorithmic
complexity. We compute the binding energies and point-nucleon densities of
$A\leq 4$ nuclei as emerging from a leading-order pionless effective field
theory Hamiltonian. We successfully benchmark the ANN wave function against
more conventional parametrizations based on two- and three-body Jastrow
functions, and virtually-exact Green's function Monte Carlo results. | nucl-th |
Decay of Hypernuclei: We present a nonrelativistic transition potential for the weak
strangeness-changing reaction $\Lambda N \to NN$. The potential is based on a
one meson exchange model (OME), where, in addition to the long-ranged pion, the
exchange of the pseudoscalar $K, \eta$, as well as the vector $\rho, \omega,
K^*$ mesons is considered. Results obtained for different hypernuclear decay
observables are compared to the available experimental data. | nucl-th |
Theoretical uncertainties of the elastic nucleon-deuteron scattering
observables: Theoretical uncertainties of various types are discussed for the
nucleon-deuteron elastic scattering observables at the incoming nucleon
laboratory energies up to 200 MeV. We are especially interested in the
statistical errors arising from uncertainties of parameters of a
nucleon-nucleon interaction. The obtained uncertainties of the differential
cross section and numerous scattering observables are in general small, grow
with the reaction energy and amount up to a few percent at 200 MeV. We compare
these uncertainties with the other types of theoretical errors like truncation
errors, numerical uncertainties and uncertainties arising from using the
various models of nuclear interaction. We find the latter ones to be dominant
source of uncertainties of modern predictions for the three-nucleon scattering
observables. To perform above mentioned studies we use the One-Pion-Exchange
Gaussian potential derived by the Granada group, for which the covariance
matrix of its parameters is known, and solve the Faddeev equation for the
nucleon-deuteron elastic scattering. Thus beside studying theoretical
uncertainties we also show a description of the nucleon-deuteron elastic
scattering data by the One-Pion-Exchange Gaussian model and compare it with
results obtained with other nucleon-nucleon potentials, including chiral
N$^4$LO forces from the Bochum-Bonn and Moscow(Idaho)-Salamanca groups. In this
way we confirm the usefulness and high quality of the One-Pion-Exchange
Gaussian force. | nucl-th |
The Weak Parity-Violating Pion-Nucleon Coupling (Revised): We use QCD sum rules to obtain the weak parity-violating pion-nucleon
coupling constant $f_{\pi NN}$. We find that $f_{\pi NN}\approx 2\times
10^{-8}$, about an order of magnitude smaller than the ``best estimates'' based
on quark models. This result follows from the cancellation between perturbative
and nonperturbative QCD processes not found in quark models, but explicit in
the QCD sum rule method. Our result is consistent with the experimental upper
limit found from $^{18}$F parity-violating measurements. | nucl-th |
Leading order relativistic hyperon-nucleon interactions in chiral
effective field theory: We apply a recently proposed covariant power counting in nucleon-nucleon
interactions to study strangeness $S=-1$ $\Lambda N-\Sigma N$ interactions in
chiral effective field theory. At leading order, Lorentz invariance introduces
12 low energy constants, in contrast to the heavy baryon approach, where only
five appear. The Kadyshevsky equation is adopted to resum the potential in
order to account for the non-perturbative nature of hyperon-nucleon
interactions. A fit to the $36$ hyperon-nucleon scattering data points yields
$\chi^2\simeq 16$, which is comparable with the sophisticated phenomenological
models and the next-to-leading order heavy baryon approach. However, one cannot
achieve a simultaneous description of the nucleon-nucleon phase shifts and
strangeness $S=-1$ hyperon-nucleon scattering data at leading order. | nucl-th |
Resonance Structure and Polarizability of the nucleon: The main features of the resonance structure of the nucleon are discussed,
particular with regard to the helicity dependence of real and virtual
photoabsorption. The dependence of the partial cross sections on both the
resonance helicity amplitudes and the electromagnetic multipoles is outlined.
The general structure of the Compton tensor is reviewed and applied to the
special cases of real to real, virtual to real, and virtual to virtual Compton
scattering. Recent theoretical developments in dispersion relations are
presented, together with a short overview regarding static, dynamical, and
generalized polarizabilities of the nucleon as well as the status of the
Gerasimov-Drell-Hearn sum rule and related integrals. | nucl-th |
Nuclear Lattice Simulations with Chiral Effective Field Theory: We study nuclear and neutron matter by combining chiral effective field
theory with non-perturbative lattice methods. In our approach nucleons and
pions are treated as point particles on a lattice. This allows us to probe
larger volumes, lower temperatures, and greater nuclear densities than in
lattice QCD. The low energy interactions of these particles are governed by
chiral effective theory and operator coefficients are determined by fitting to
zero temperature few-body scattering data. Any dependence on the lattice
spacing can be understood from the renormalization group and absorbed by
renormalizing operator coefficients. In this way we have a realistic simulation
of many-body nuclear phenomena with no free parameters, a systematic expansion,
and a clear theoretical connection to QCD. We present results for hot neutron
matter at temperatures 20 to 40 MeV and densities below twice nuclear matter
density. | nucl-th |
Structure of eta' mesonic nuclei in a relativistic mean field theory: The structure and the energy spectrum of the $\eta^{\prime}$ mesonic nuclei
are investigated in a relativistic mean field theory. One expects a substantial
attraction for the $\eta^{\prime}$ meson in finite nuclei due to the partial
restoration of chiral symmetry in the nuclear medium. Such a hadronic scale
interaction for the $\eta^{\prime}$ mesonic nuclei may provide modification of
the nuclear structure. The relativistic mean field theory is a self-contained
model for finite nuclei which provides the saturation property within the
model, and is good to investigate the structure change of the nucleus induced
by the $\eta^{\prime}$ meson. Using the local density approximation for the
mean fields, we solve the equations of motion for the nucleons and the
$\eta^{\prime}$ meson self-consistently, and obtain the nuclear density
distribution and the $\eta^{\prime}$ energy spectrum for the $\eta^{\prime}$
mesonic nuclei. We take $^{12}$C, $^{16}$O and $^{40}$Ca for the target nuclei.
We find several bound states of the $\eta^{\prime}$ meson for these nuclei
thanks to the attraction for $\eta^{\prime}$ in nuclei. We also find a
sufficient change of the nuclear structure especially for the $1s$ bound state
of $\eta^{\prime}$. This implies that the production of the $1s$ bound state in
nuclear reaction may be suppressed. | nucl-th |
Dilepton flow and deconfinement phase transition in heavy ion collisions: The dilepton radial flow in Au+Au collisions at \sqrt{s_{NN}}=200 GeV is
investigated. The space-time evolution of the fireball is described by a 2+1
dimensional ideal hydrodynamics with a variety of equations of state. The slope
parameters of the transverse momentum spectra from the partonic and hadronic
phases show distinct features and are sensitive to equation of state
parameters. The elliptic flow and breaking of M_T scaling are also studied and
have distinct features for the two phases. These features can serve as clean
signals for the formation of a quark-gluon plasma in ultra-relativistic heavy
ion collisions. | nucl-th |
Collective vibrational states with fast iterative QRPA method: An iterative method we previously proposed to compute nuclear strength
functions is developed to allow it to accurately calculate properties of
individual nuclear states. The approach is based on the
quasi-particle-random-phase approximation (QRPA) and uses an iterative
non-hermitian Arnoldi diagonalization method where the QRPA matrix does not
have to be explicitly calculated and stored. The method gives substantial
advantages over conventional QRPA calculations with regards to the
computational cost. The method is used to calculate excitation energies and
decay rates of the lowest lying 2+ and 3- states in Pb, Sn, Ni and Ca isotopes
using three different Skyrme interactions and a separable gaussian pairing
force. | nucl-th |
Incoherent pion photoproduction on the deuteron with polarization
observables I: Formal expressions: Formal expressions are developed for the general five-fold differential cross
section of incoherent $\pi$-photoproduction on the deuteron including beam and
target polarization. The polarization observables of the cross section are
described by various beam, target and beam-target asymmetries for polarized
photons and/or polarized deuterons. They are given as bilinear hermitean forms
in the reaction matrix elements divided by the unpolarized cross section. In
addition, the corresponding observables for the semi-exclusive reaction $\vec
d(\vec \gamma,\pi)NN$ are also given. | nucl-th |
Proof by characters of the orthogonal-orthogonal duality and relations
of Casimir invariants: The theorem of orthogonal-orthogonal duality of Rowe, Repka, and Carvalho is
proven by a method based on characters that is very different from theirs and
akin to Helmers's half a century earlier proof of the analogous
sympletic-symplectic duality. I demonstrate how three duality theorems listed
by Rowe, Repka, and Carvalho allow very brief derivations of linear relations
between the Casimir invariants of the connected representations based on the
geometry of their Young diagrams, and discuss for which physical systems other
than such already considered in the literature an analysis in terms of the
orthogonal-orthogonal duality might be useful. | nucl-th |
The CSM extension for the description of 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 $^{237}$U and $^{239}$Pu. The quadrupole and
octupole boson Hamiltonian associated to the core is identical to the one
previously used for the description of four positive and four negative parity
bands in the neighboring even-even isotopes. The single particle space for the
odd nucleon consists of three spherical shell model states, two of positive and
one of negative parity. 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 parameters involved in the particle-core coupling Hamiltonian were fixed by
fitting four particular energies in the two bands. The calculated 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. | nucl-th |
Fusion and quasi-fission dynamics in nearly-symmetric reactions: Some nearly-symmetric fusion reactions are systematically investigated with
the improved quantum molecular dynamics (ImQMD) model. By introducing two-body
inelastic scattering in the Fermi constraint procedure, the stability of an
individual nucleus and the description of fusion cross sections at energies
near the Coulomb barrier can be further improved. Simultaneously, the
quasi-fission process in $^{154}$Sm+$^{160}$Gd is also investigated with the
microscopic dynamics model for the first time. We find that at energies above
the Bass barrier, the fusion probability is smaller than $10^{-5}$ for this
reaction, and the nuclear contact-time is generally smaller than $1500$ fm/c.
From the central collisions of Sm+Gd, the neutron-rich fragments such as
$^{164,165}$Gd, $^{192}$W can be produced in the ImQMD simulations, which
implies that the quasi-fission reaction could be an alternative way to
synthesize new neutron-rich heavy nuclei. | nucl-th |
Exposing the Noncollectivity in Elliptic Flow: We show that backward-forward elliptic anisotropy correlation provides an
experimentally accessible observable which distinguishes between collective and
non-collective contributions to the observed elliptic anisotropy $v_2$ in
relativistic heavy ion collisions. The measurement of this observable will
reveal the momentum scale at which collective expansion seizes and where the
elliptic anisotropy is dominated by (semi)-hard processes. | nucl-th |
Deuteron spin structure functions in the resonance and DIS regions: We derive relations between spin-dependent nuclear and nucleon g_1 and g_2
structure functions within the nuclear impulse approximation, which are valid
at all Q^2, and in both the resonance and deep inelastic regions. We apply the
formalism to the specific case of the deuteron, which is often used as a source
of neutron structure information, and compare the size of the nuclear
corrections calculated using exact kinematics and using approximations
applicable at large Q^2. | nucl-th |
Multifragmentation vs. Evaporation vs. Binary-Decay in Fragment
Production: This paper presents part of an internal LANL Progress Report on completion of
the "S" and "G" versions of the improved Cascade-Exciton Model (CEM03.01) and
the Los Alamos Quark-Gluon String Model (LAQGSM.03.01) codes. The "S" versions
consider fragmentation of compound nuclei produced after the preequilibrium
stage of reactions for excitation energies above 2A MeV using the Statistical
Multifragmentation Model (SMM) by Botvina et al. ("S" stands for SMM), while
the "G" versions describe evaporation/fission stages of reactions using the
fission-like binary-decay model GEMINI of Charity et al. ("G" stands for
GEMINI) instead of using the the Generalized Evaporation Model GEM2 of Furihata
incorporated into the standard versions of these codes. We present here an
analysis of the recent 660 MeV p + 129I and 3.65 GeV p + 112Sn JINR
measurements, of the new COSY data on 1.2 GeV p + (13 nuclei from Al to Th), of
the 300 MeV and 1 GeV p + 56Fe data measured at GSI in inverse kinematics, and
of the new GSI data on 1 GeV/nucleon 124Xe and 136Xe + Pb. To better understand
the mechanisms of fragment production, we discuss several calculated but
not-yet-measured kinematic characteristics of products of these reactions,
which are predicted to be quite different by SMM, GEMINI, and GEM2. We find
these kinematic quantities to be potentially useful in differentiating these
reaction mechanisms if they can be measured in future experiments. | nucl-th |
alpha decay half-lives of new superheavy nuclei within a generalized
liquid drop model: The alpha decay half-lives of the recently produced isotopes of the 112, 114,
116 and 118 nuclei and decay products have been calculated in the
quasi-molecular shape path using the experimental Qalpha value and a
Generalized Liquid Drop Model including the proximity effects between nucleons
in the neck or the gap between the nascent fragments. Reasonable estimates are
obtained for the observed alpha decay half-lives. The results are compared with
calculations using the Density-Dependent M3Y effective interaction and the
Viola-Seaborg-Sobiczewski formulae. Generalized Liquid Drop Model predictions
are provided for the alpha decay half-lives of other superheavy nuclei using
the Finite Range Droplet Model Qalpha and compared with the values derived from
the VSS formulae. | nucl-th |
Multiparticle correlations and momentum conservation in nucleus-nucleus
collisions: Particle correlations are very actively studied in heavy-ion collisions at
ultra-relativistic energies. Here, an attempt is made at determining a proper
reference for such studies, by taking properly into account the multiparticle
correlations induced by the conservation of total momentum in the collisions. | nucl-th |
Pion and photon induced reactions on the nucleon in a unitary model: We present a relativistic calculation of pion scattering, pion
photoproduction and Compton scattering on the nucleon in the energy region of
the \Del-resonance (upto 450 MeV photon lab energy), in a unified framework
which obeys the unitarity constraint. It is found that the recent data on the
cross section for nucleon Compton scattering determine accurately the
parameters of the electromagnetic nucleon--\Del\ coupling. The calculated
pion-photoproduction partial-wave amplitudes agree well with the recent Arndt
analysis. | nucl-th |
Double giant dipole resonances in time-dependent density-matrix theory: The strength functions of the DGDRs in 16O and 40Ca are calculated using an
extended version of TDHF known as the time-dependent density-matrix theory
(TDDM). The calculations are done in a self-consistent manner, in which the
same Skyrme force as that used for the mean-field potential is used as the
residual interaction to calculate two-body correlations. It is found that the
DGDR in 16O has a large width due to the Landau damping, although the centroid
energy of the DGDR is close to twice the energy of the GDR calculated in RPA.
The DGDR in 40Ca is found more harmonic than that in 16O. | nucl-th |
Potential for measurement of the tensor polarizabilities of nuclei in
storage rings by the frozen spin method: The frozen spin method can be effectively used for a high-precision
measurement of the tensor electric and magnetic polarizabilities of the
deuteron and other nuclei in storage rings. For the deuteron, this method would
provide the determination of the deuteron's polarizabilities with absolute
precision of order of $10^{-43}$ cm$^3$. | nucl-th |
On the PBF neutrino losses in superfluid cores of neutron stars: Axial anomalous contributions into neutrino PBF losses due to triplet pairing
of neutrons are still ignored in modeling the evolution of neutron stars. In
this paper, the influence of the anomalous axial contributions onto the rate of
neutron stars cooling is estimated. | nucl-th |
Kinetic-theory approach to low-energy collective modes in nuclei: Two different solutions of the linearized Vlasov equation for finite systems,
characterized by fixed and moving-surface boundary conditions, are discussed in
a unified perspective. A condition determining the eigenfrequencies of
collective nuclear oscillations, that can be obtained from the moving-surface
solution, is studied for isoscalar vibrations of lowest multipolarity. Analytic
expressions for the friction and mass parameters related to the low-enegy
surface excitations are derived and their value is compared to values given by
other models. Both similarities and differences are found with respect to the
other approaches, however the close agreement obtained in many cases with one
of the other models suggests that, in spite of some important differences, the
two approaches are substantially equivalent. The formalism based on the Vlasov
equation is more transparent since it leads to analytical expressions that can
be a basis for further improvement of the model. | nucl-th |
Strange-quark contribution to the ratio of neutral- to charged-current
cross sections in neutrino-nucleus scattering: A formalism based on a relativistic plane wave impulse approximation is
developed to investigate the strange-quark content ($g_{A}^{s}$) of the
axial-vector form factor of the nucleon via neutrino-nucleus scattering.
Nuclear structure effects are incorporated via an accurately calibrated
relativistic mean-field model. The ratio of neutral- to charged-current cross
sections is used to examine the sensitivity of this observable to $g_{A}^{s}$.
For values of the incident neutrino energy in the range proposed by the FINeSSE
collaboration and by adopting a value of $g_{A}^{s}=-0.19$, a 30% enhancement
in the ratio is observed relative to the $g_{A}^{s}=0$ result. | nucl-th |
Meson production in high-energy electron-nucleus scattering: Pseudoscalar mesons can be produced and studied in high-energy
electron-nucleus scattering. We review and extend our previous analysis of
meson production in the nuclear Coulomb field. The $P\rightarrow \gamma \gamma$
decay rates are most directly determined for mesons produced in the
double-Coulomb region where both photons are nearly real, and provided the
background-hadronic contribution remains small. The larger the mass of the
meson the higher the electron energy needed to assure such a condition. | nucl-th |
$S$-factor and scattering parameters from ${}^3$He + ${}^4$He
$\rightarrow {}^7$Be + $γ$ data: We use the next-to-leading-order (NLO) amplitude in an effective field theory
(EFT) for ${}^3$He + ${}^4$He $\rightarrow {}^7$Be + $\gamma$ to perform the
extrapolation of higher-energy data to solar energies. At this order the EFT
describes the capture process using an s-wave scattering length and effective
range, the asymptotic behavior of $^7$Be and its excited state, and
short-distance contributions to the E1 capture amplitude. We use a Bayesian
analysis to infer the multi-dimensional posterior of these parameters from
capture data below 2 MeV. The total $S$-factor $S(0)= 0.578^{+0.015}_{-0.016}$
keV b at 68% degree of belief. We also find significant constraints on
$^3$He-$^4$He scattering parameters. | nucl-th |
Baryon-to-pion ratios within generic (non)extensive statistics: The successive stages of a high-energy collision are conjectured to end up
with chemical and thermal freezeout of the produced particles. We utilize
generic (non)extensive statistics which is believed to determine the degree of
(non)extensivity through two critical exponents due to possible phase-space
modifications. This statistical approach likely manifests various types of
correlations and fluctuations and also possible interactions among the
final-state produced particles. We study the baryon-to-pion ratios at top RHIC
and LHC energies including the so-called proton anomaly. | nucl-th |
Vacuum Structures in Hamiltonian Light-Front Dynamics: Hamiltonian light-front dynamics of quantum fields may provide a useful
approach to systematic non-perturbative approximations to quantum field
theories. We investigate inequivalent Hilbert-space representations of the
light-front field algebra in which the stability group of the light-front is
implemented by unitary transformations. The Hilbert space representation of
states is generated by the operator algebra from the vacuum state. There is a
large class of vacuum states besides the Fock vacuum which meet all the
invariance requirements. The light-front Hamiltonian must annihilate the vacuum
and have a positive spectrum. We exhibit relations of the Hamiltonian to the
nontrivial vacuum structure. | nucl-th |
Discussing the possibility of observation of parity violation in heavy
ion collisions: It was recently argued that in heavy ion collision the parity could be
broken. This Note addresses the question of possibility of the experimental
detection of the effect. We discuss how parity violating effects would modify
the final particle distributions and how one could construct variables
sensitive to the effect, and which measurement would be the (most) conclusive.
Discussing different observables we also discuss the question if the
``signals'' can be faked by ``conventional'' effects (such as anisotropic flow,
etc.) and make estimates of the signals. | nucl-th |
Investigation of Level Statistics by Generalized Brody Distribution and
Maximum Likelihood Estimation Method: With generalizing the Brody distribution to include the Poisson, GOE and GUE
limits and with employing the maximum likelihood estimation technique, the
spectral statistics of different sequences were considered in the nearest
neighbor spacing statistics framework. The ML-based estimated values for the
parameters of generalized distribution propose more precisions in compare to
the predictions of other distributions. The transition in the level spacing
statistics of different systems were described by the distances of ML-based
predictions for generalized distribution to three limits which determined by
KLD measures. | nucl-th |
Temperature and angular momentum dependence of the quadrupole
deformation in sd-shell: Temperature and angular momentum dependence of the quadrupole deformation is
studied in the middle of the sd-shell for 28Si and 27Si isotopes using the
spherical shell model approach. The shell model calculations have been
performed using the standard USD interaction and the canonical partition
function constructed from the calculated eigen-solutions. It is shown that the
extracted average quadrupole moments show a transitional behavior as a function
of temperature and the inferred transitional temperature is shown to vary with
angular-momentum. The quadrupole deformation of the individual eigen-states is
also analyzed. | nucl-th |
Relativistic Heavy Ion Excitation of Giant Resonances: Giant resonances and giant resonances built on other giant resonances in
nuclei are observed with very large cross sections in relativistic heavy ion
collisions. A theoretical effort is underway to understand the reaction
mechanism which leads to this process, as well as a better understanding of the
microscopic properties of multiphonon states, e.g., their strength, energy
centroids, widths and anharmonicities. | nucl-th |
Individual low-energy toroidal dipole state in $^{24}$Mg: The low-energy dipole excitations in $^{24}$Mg are investigated within the
Skyrme quasiparticle random-phase-approximation (QRPA) for axial nuclei. The
calculations with the force SLy6 reveal a remarkable feature: the lowest
$I^{\pi}K=1^-1$ excitation (E = 7.92 MeV) in $^{24}$Mg is a vortical toroidal
state (TS) representing a specific vortex-antivortex realization of well-known
spherical Hill's vortex in a strongly deformed axial confinement. This is a
striking example of an {\it individual} TS which can be much easier
discriminated in experiment than the toroidal dipole resonance embracing many
states. The TS acquires the lowest energy due to the huge prolate axial
deformation in $^{24}$Mg. The result persists for different Skyrme
parameterizations (SLy6, SVbas, SkM*). We analyze spectroscopic properties of
the TS and its relation with the cluster structure of $^{24}$Mg. Similar TS
could exist in other highly prolate light nuclei. They could serve as promising
tests for various reactions to probe a vortical (toroidal) nuclear flow. | nucl-th |
Thermodynamic Geometry of Strongly Interacting Matter: The thermodynamic geometry formalism is applied to strongly interacting
matter to estimate the deconfinement temperature. The curved thermodynamic
metric for Quantum Chromodynamics (QCD) is evaluated on the basis of lattice
data, whereas the hadron resonance gas model is used for the hadronic sector.
Since the deconfinement transition is a crossover, the geometric criterion used
to define the \mbox{(pseudo-)critical} temperature, as a function of the
baryonchemical potential $\mu_B$, is $R(T,\mu_B)=0$, where $R$ is the scalar
curvature. The (pseudo-)critical temperature, $T_c$, resulting from QCD
thermodynamic geometry is in good agreement with lattice and phenomenological
freeze-out temperature estimates. The crossing temperature, $T_h$, evaluated by
the hadron resonance gas, which suffers of some model dependence, is larger
than $T_c$ (about $20\%$) signaling remnants of confinement above the
transition. | nucl-th |
Theoretical highlights of neutrino-nucleus interactions: The recent theoretical developments in the field of neutrino-nucleus
interactions in the few-GeV region are reviewed based on the presentations made
at the NuInt09 Workshop. The topics of electron scattering and its connections
with neutrino interactions, neutrino induced quasielastic scattering and pion
production (coherent and incoherent) are covered, with special emphasis on the
challenges that arise in the comparison with new experimental data. | nucl-th |
Heavy Quarkonia in the Instantaneous Bethe-Salpeter Model: The heavy quarkonia (Charmonium \(c\bar{c}\) and Bottomonium \(b\bar{b}\))
are investigated in the framework of the instantaneous BS-equation (Salpeter
equation). We parametrize confinement alternatively by a linearly rising scalar
or a vector interaction kernel and take into account the one-gluon-exchange
(OGE) interaction in the instantaneous approximation. Mass spectra as well as
leptonic, two-photon, E1 and M1 decay widths are calculated. Our results show
that a reasonable description of the experimental data can be obtained with
both spin structures for the confining kernel. The relativistic treatment leads
to an improved description compared to nonrelativistic results for the
two-photon width of the \(\eta_c\) and to some extent for the E1-transition
widths. However, characteristic deviations indicate that within a relativistic
framework confinement is not described adequately by a potential. | nucl-th |
Exchange currents in octet hyperon charge radii: Octet hyperon charge radii are calculated in a chiral constituent quark model
including electromagnetic exchange currents between quarks. In impulse
approximation one observes a decrease of the hyperon charge radii with
increasing strangeness. This effect is reduced by exchange currents. Due to
exchange currents, the charge radius of the negatively charged hyperons are
close to the proton charge radius. | nucl-th |
Towards modeling cluster structure of $^8$Be with chiral interaction: How the nuclear force behaves in cluster states, in particular those
consisting of the $\alpha$ clusters, has been investigated so far, but not yet
elucidated. Today the chiral effective field theory is established and it would
shed new light on the microscopic understanding of the cluster states. We aim
to address a possible source of the attraction in the cluster states of
$^8\mathrm{Be}$ in view of the pion exchange. Namely, we investigate whether
the two-pion-exchange interaction acts as a dominant attraction in the
$\alpha+\alpha$ system as predicted by a previous work. We describe
theoretically the cluster structure of $^8\mathrm{Be}$ by the Brink model, for
which the effective interaction is designed from the realistic nuclear force
derived through the chiral effective field theory. The two-body matrix elements
of the chiral interaction with the local-Gaussian bases are formulated within
the approximation of the spin-isospin saturation forming an $\alpha$ particle.
Introducing a global prefactor to the chiral interaction phenomenologically,
the ground and low-lying excited states of $^8\mathrm{Be}$, the scattering
phase shift of the $\alpha$-$\alpha$ system as well, are satisfactorily
depicted. The attraction in the cluster states is found to be stemming from the
two-pion-exchange contributions dominantly, along with nonnegligible
short-range terms. The present work can be the foundation towards constructing
realistic cluster models, by which the cluster states will be revealed
microscopically in the next step. | nucl-th |
RPA Correlations and Nuclear Densities in Relativistic Mean Field
Approach: The relativistic mean field approach (RMF) is well known for describing
accurately binding energies and nucleon distributions in atomic nuclei
throughout the nuclear chart. The random phase approximation (RPA) built on top
of the RMF is also a good framework for the study of nuclear excitations. Here,
we examine the consequences of long range correlations brought about by the RPA
on the neutron and proton densities as given by the RMF approach. | nucl-th |
Can the Neutron Polarizabilities Be Determined from a Deuteron Compton
Scattering Experiment?: A calculation of deuteron Compton scattering using non-relativistic
diagrammatic perturbation theory is presented, with the primary motivation of
investigating the feasibility of determining the neutron polarizabilities from
this type of experiment. This calculation is expected to be valid for energies
below 100 MeV. Previous theoretical and experimental estimates for the
polarizabilities are given. All diagrams are calculated by expanding the photon
wavefunctions into partial waves and using realistic deuteron wavefunctions.
The Green's function for the intermediate state in the dispersive states is
determined numerically. Pion-exchange, relativistic, and recoil corrections are
also included. The low-energy theorem is shown to be satisfied. The relative
effects of the different terms as well as their effects on the determinations
of the polarizabilities are discussed at energies of 49, 69, and 95 MeV. The
cross-section is dominated by the seagull, polarizability, and electromagnetic
multipole interactions. Relativistic and pion-exchange terms are also
important, while recoil corrections and multipoles of L=2 and greater are
negligible. The calculation provides a reasonable description of the
experimental data points at 49 and 69 MeV, except for the point at the greatest
angle. The polarizabilities are difficult to determine at these energies due to
the size of the experimental error bars. No data has been published at 95 MeV
but a more accurate determination of the polarizabilities is likely at this
higher energy. Detailed calculations for all terms can be found in the
appendices. | nucl-th |
On the convergence of multi-channel effective interactions: A detailed analysis of convergence properties of the Andreozzi-Lee-Suzuki
iteration method, which is used for the calculation of low-momentum effective
potentials Vlowk is presented. After summarizing different modifications of the
iteration method for one-flavor channel we introduce a simple model in order to
study the generalization of the iteration method to multi-flavor channels. The
failure of a straightforward generalization is discussed. The introduction of a
channel-dependent cutoff cures the conceptual and technical problems. This
novel method has already been applied successfully for realistic
hyperon-nucleon interactions. | nucl-th |
Recent issues in hadron spectroscopy: A brief survey is presented of recently discovered hadrons, some of them
presumably demonstrating a new kind of internal structure. This includes :
spin-singlet quarkonium, mesons with unexpected mass or width, baryons with two
heavy quarks, and pentaquark candidates. Flavour configurations with a
combination of light and heavy quarks appear as particularly promising. | nucl-th |
Effects of $ω$ meson self-coupling on the properties of finite
nuclei and neutron stars: The effects of $\omega$ meson self-coupling (OMSC) on the properties of
finite nuclei and neutron stars are investigated within the framework of
effective field theory based relativistic mean-field (ERMF) model which
includes the contributions from all possible mixed interactions between the
scalar-isoscalar ($\sigma$), vector-isoscalar ($\omega$) and vector-isovector
($\rho$) mesons upto the quartic order. For a realistic investigation, several
parameter sets corresponding to different values of OMSC are generated by
adjusting the remaining parameters of the ERMF model to fit the properties of
the finite nuclei. Though, all these parameter sets give equally good fit to
the properties of the finite nuclei, only moderate values of OMSC are favored
from the "naturalness" point of view. The equation of state for the symmetric
nuclear and pure neutron matters resulting from the parameter sets with the
moderate values of OMSC are in close agreement with the ones obtained within
the Dirac-Brueckner-Hartree-Fock approximation. For such parameter sets the
limiting mass for the neutron stars composed of $\beta$-stable matter is $\sim
1.9M_\odot$. It is found that the direct Urca process can occur in the neutron
stars with "canonical" mass of $1.4M_\odot$ only for the moderate and higher
values of OMSC. Some other interesting properties for the neutron stars are
also discussed. | nucl-th |
Effective theory for the non-rigid rotor in an electromagnetic field:
Toward accurate and precise calculations of E2 transitions in deformed nuclei: We present a model-independent approach to electric quadrupole transitions of
deformed nuclei. Based on an effective theory for axially symmetric systems,
the leading interactions with electromagnetic fields enter as minimal couplings
to gauge potentials, while subleading corrections employ gauge-invariant
non-minimal couplings. This approach yields transition operators that are
consistent with the Hamiltonian, and the power counting of the effective theory
provides us with theoretical uncertainty estimates. We successfully test the
effective theory in homonuclear molecules that exhibit a large separation of
scales. For ground-state band transitions of rotational nuclei, the effective
theory describes data well within theoretical uncertainties at leading order.
In order to probe the theory at subleading order, data with higher precision
would be valuable. For transitional nuclei, next-to-leading order calculations
and the high-precision data are consistent within the theoretical uncertainty
estimates. We also study the faint inter-band transitions within the effective
theory and focus on the $E2$ transitions from the $0^+_2$ band (the "$\beta$
band") to the ground-state band. Here, the predictions from the effective
theory are consistent with data for several nuclei, thereby proposing a
solution to a long-standing challenge. | nucl-th |
Neutrino scattering from hydrodynamic modes in hot and dense neutron
matter: We calculate the scattering rate of low energy neutrinos in hot and dense
neutron matter encountered in neutrons stars and supernova in the hydrodynamic
regime. We find that the Brillouin peak, associated with the sound mode, and
the Rayleigh peak, associated with the thermal diffusion mode, dominate the
dynamic structure factor. Although the total scattering cross section is
constrained by the compressibility sum rule, the differential cross-section
calculated using the hydrodynamic response function differs from results
obtained in approximate treatments often used in astrophysics such as random
phase approximations (RPA). We identified these differences and discuss its
implications for neutrino transport in supernova. | nucl-th |
Studying the process $γd \to π^0ηd$: In these proceedings we present our recent results on the study of the
process $\gamma d \to \pi^0 \eta d$, where the existence of a dibaryon in the
$\eta d$ invariant mass distribution has been recently claimed. As we will
show, many of the relevant aspects observed in the experiment, as the shift of
the $\eta d$ and $\pi d$ invariant mass distributions with respect to phase
space can be described with our model, where no dibaryon is formed. Instead, we
consider the interaction of the $\gamma$ with the nucleons forming the deuteron
to proceed through $\gamma N \to \Delta(1700)\to \eta \Delta(1232) \to \eta
\pi^0 N$, followed by the rescattering of the $\pi$ and $\eta$ with the other
nucleon of the deuteron. Theoretical uncertainties related to different
parameterizations of the deuteron wave function are investigated | nucl-th |
The hadron-quark phase transition in dense matter and neutron stars: We study the hadron-quark phase transition in the interior of neutron stars
(NS's). We calculate the equation of state (EOS) of hadronic matter using the
Brueckner-Bethe-Goldstone formalism with realistic two-body and three-body
forces, as well as a relativistic mean field model. For quark matter we employ
the MIT bag model constraining the bag constant by using the indications coming
from the recent experimental results obtained at the CERN SPS on the formation
of a quark-gluon plasma. We find necessary to introduce a density dependent bag
parameter, and the corresponding consistent thermodynamical formalism. We
calculate the structure of NS interiors with the EOS comprising both phases,
and we find that the NS maximum masses fall in a relatively narrow interval,
$1.4 M_\odot \leq M_{\rm max} \leq 1.7 M_\odot$. The precise value of the
maximum mass turns out to be only weakly correlated with the value of the
energy density at the assumed transition point in nearly symmetric nuclear
matter. | nucl-th |
On three topical aspects of the N=28 isotonic chain: The evolution of single-particle orbits along the N=28 isotonic chain is
studied within the framework of a relativistic mean-field approximation. We
focus on three topical aspects of the N=28 chain: (a) the emergence of a new
magic number at Z=14; (b) the possible erosion of the N=28 shell; and (c) the
weakening of the spin-orbit splitting among low-j neutron orbits. The present
model supports the emergence of a robust Z=14 subshell gap in 48Ca, that
persists as one reaches the neutron-rich isotone 42Si. Yet the proton removal
from 48Ca results in a significant erosion of the N=28 shell in 42Si. Finally,
the removal of s1/2 protons from 48Ca causes a ~50% reduction of the spin-orbit
splitting among neutron p-orbitals in 42Si. | nucl-th |
Charge-exchange dipole excitations in neutron-rich nuclei: $-1 \hbar
ω_0$, anti-analog pygmy, and anti-analog giant resonances: The occurrence of the low-lying charge-exchange non spin-flip dipole modes
below the giant resonance in neutron-rich nuclei is predicted on the basis of
nuclear density functional theory. The ground and excited states are described
in the framework of the self-consistent Hartree-Fock-Bogoliubov and the
proton-neutron quasiparticle-random-phase approximation employing a Skyrme-type
energy density functional. The model calculations are performed for the
spherical neutron-rich Ca, Ni, and Sn isotopes. It is found that the low-lying
states appear sensitively to the shell structure associated with the $-1 \hbar
\omega_0$ excitation below the Gamow-Teller states. Furthermore, the pygmy
resonance emerges below the giant resonance when the neutrons occupy the
low-$\ell (\ell \leq 2 -3)$ orbitals analogous to the pygmy resonance seen in
the electric dipole response. | nucl-th |
Gradient Symplectic Algorithms for Solving the Schroedinger Equation
with Time-Dependent Potentials: We show that the method of factorizing the evolution operator to fourth order
with purely positive coefficients, in conjunction with Suzuki's method of
implementing time-ordering of operators, produces a new class of powerful
algorithms for solving the Schroedinger equation with time-dependent
potentials. When applied to the Walker-Preston model of a diatomic molecule in
a strong laser field, these algorithms can have fourth order error coefficients
that are three orders of magnitude smaller than the Forest-Ruth algorithm using
the same number of Fast Fourier Transforms. When compared to the second order
split-operator method, some of these algorithms can achieve comparable
convergent accuracy at step sizes 50 times as large. Morever, we show that
these algorithms belong to a one-parameter family of algorithms, and that the
parameter can be further optimized for specific applications. | nucl-th |
Study of deuteron-proton charge exchange reaction at small transfer
momentum: The charge-exchange reaction pd->npp at 1 GeV projectile proton energy is
studied in the multiple-scattering expansion technique. This reaction is
considered in a special kinematics, when the transfer momentum from the beam
proton to fast neutron is close to zero. The differential cross section and a
set of polarization observables are calculated. It was shown that contribution
of the final state interaction between two protons is very significant. | nucl-th |
Including off-diagonal anisotropies in anisotropic hydrodynamics: In this paper we present a method for efficiently including the effects of
off-diagonal local rest frame momentum anisotropies in leading-order
anisotropic hydrodynamics. The method relies on diagonalization of the
space-like block of the anisotropy tensor and allows one to reduce the
necessary moments of the distribution function in the off-diagonal case to a
linear combination of diagonal-anisotropy integrals. Once reduced to
diagonal-anisotropy integrals, the results can be computed efficiently using
techniques described previously in the literature. We present a general
framework for how to accomplish this and provide examples for off-diagonal
anisotropy moments entering into the energy-momentum tensor and viscous update
equations which emerge when performing anisotropic pressure matching. | nucl-th |
Validity of the linear coupling approximation in heavy-ion fusion
reactions at sub barrier energies: The role of higher order coupling of surface vibrations to the relative
motion in heavy-ion fusion reactions at near-barrier energies is investigated.
The coupled channels equations are solved to all orders, and also in the linear
and the quadratic coupling approximations. Taking $^{64}$Ni + $^{92,96}$Zr
reactions as examples, it is shown that all order couplings lead to
considerably improved agreement with the experimentally measured fusion cross
sections and average angular momenta of the compound nucleus for such heavy
nearly symmetric systems. The importance of higher order coupling is also
examined for asymmetric systems like $^{16}$O + $^{112}$Cd, $^{144}$Sm, for
which previous calculations of the fusion cross section seemed to indicate that
the linear coupling approximation was adequate. It is shown that the shape of
the barrier distributions and the energy dependence of the average angular
momentum can change significantly when the higher order couplings are included,
even for systems where measured fusion cross sections may seem to be well
reproduced by the linear coupling approximation. | nucl-th |
Hybrid stars from a constrained equation of state: We determine, within a meta-model, the properties of the nuclear matter
equation of state (EoS) that allow for a phase transition to deconfinement
matter. It is shown that the properties that define the isoscalar channel are
the ones that are affected, in particular, a phase transition implies much
larger values of the skewness and kurtosis. The effect of multi-quark
interaction channels in the description of the quark phase in hybrid stars is
also studied. NS properties, such as the mass and radius of the quark core,
show an interplay dependence between the 8-quark vector and the 4-quark
isovector-vector interactions. We show that low mass NS, $M\sim 1.4 M_\odot$,
may already contain a quark core, and satisfy all existing NS observational
constraints. We discuss the strangeness content of the quark core and its
influence on the speed of sound. | nucl-th |
Isospin-violating nucleon-nucleon forces using the method of unitary
transformation: Recently, we have derived the leading and subleading isospin-breaking
three-nucleon forces using the method of unitary transformation. In the present
work we extend this analysis and consider the corresponding two-nucleon forces
using the same approach. Certain contributions to the isospin-violating one-
and two-pion-exchange potential have already been discussed by various groups
within the effective field theory framework. Our findings agree with the
previously obtained results. In addition, we present the expressions for the
subleading charge-symmetry-breaking two-pion exchange potential which were not
considered before. These corrections turn out to be numerically important.
Together with the three-nucleon force results presented in our previous work,
the results of the present study specify completely isospin-violating nuclear
forces up to the order $q^5/\Lambda^5$, where $q$ ($\Lambda$) denotes the soft
(hard) scale. | nucl-th |
Rho-Omega Mixing via QCD Sum Rules with Finite Mesonic Widths: Based on the analysis of both Borel and Finite-Energy QCD sum rules, the
inclusion of finite mesonic widths leads to a dramatic effect on the
predictions for the momentum dependence of the rho-omega mixing matrix element.
It is shown that the rho-omega mixing matrix element traditionally discussed in
the literature, has the same sign and similar magnitude in the space-like
region as its on-shell value. This contrasts the zero-width result where the
mixing matrix element is typically of opposite sign in the space-like region. | nucl-th |
Continuum Coupling and Pair Correlation in Weakly Bound Deformed Nuclei: We formulate a new Hartree-Fock-Bogoliubov method applicable to weakly bound
deformed nuclei using the coordinate-space Green's function technique. An
emphasis is put on treatment of quasiparticle states in the continuum, on which
we impose the correct boundary condition of the asymptotic out-going wave. We
illustrate this method with numerical examples. | nucl-th |
Heavy-ion physics: freedom to do hot, dense, exciting QCD: In these two lectures I review the basics of heavy-ion collisions at
relativistic energies and the physics we can do with them. I aim to cover the
basics on the kinematics and observables in heavy-ion collider experiments, the
basics on the phenomenology of the nuclear matter phase diagram, some of the
model building and simulations currently used in the heavy-ion physics
community and a selected list of amazing phenomenological discoveries and
predictions. | nucl-th |
Statistical and Dynamic Models of Charge Balance Functions: Charge balance functions, which identify balancing particle-antiparticle
pairs on a statistical basis, have been shown to be sensitive to whether
hadronization is delayed by several fm/c in relativistic heavy ion collisions.
Results from two classes of models are presented here, microscopic hadronic
models and thermal models. The microscopic models give results which are
contrary to recently published pi+pi- balance functions from the STAR
collaboration, whereas the thermal model roughly reproduce the experimental
results. This suggests that charge conservation is local at breakup, which is
in line with expectations for a delayed hadronization. Predictions are also
presented for balance functions binned as a function of Q_inv. | nucl-th |
Universal scaling of meson and baryon spectra in p-Pb collisions at 5.02
TeV: We systematically investigate the scaling property of mesons (pions and
kaons) and baryons (protons, ${\rm \Lambda}$, ${\rm \Xi}$ and ${\rm \Omega}$)
transverse momentum ($p_{\rm T}$) spectra at different centrality classes
(0-5$\%$, 5-10$\%$, 10-20$\%$, 20-40$\%$, 40-60$\%$, 60-80$\%$ and 80-100$\%$)
in proton-lead collisions with center of mass energy per nucleon pair 5.02 TeV.
In the low $p_{\rm T}$ region with $p_{\rm{T}}\leq $ 3.9 (3.1, 2.5, 2.7, 2.4
and 2.8) GeV/c, a universal scaling independent of the centrality is observed
in the pion (kaon, proton, ${\rm \Lambda}$, ${\rm \Xi}$ and ${\rm \Omega}$)
spectra when a dilatation, $p_{\rm T}\rightarrow p_{\rm T}/K$, is applied. Here
$K$ is a scaling parameter depending on the centrality class. We find that the
rates at which ln$K$ changes with the logarithmic value of the average value of
the number of participating nucleons, ln$\langle N_{\rm{part}}\rangle$, are
stronger for baryons than those for mesons. In the high $p_{\rm T}$ region,
there is a deviation from the scaling. The more peripheral the collisions are,
the more obvious the violation of the scaling is. In the framework of the
colour string percolation (CSP) model, we show that mesons and baryons are
generated from the decay of clusters formed by strings overlapping in the
transverse plane with the same size dispersion but with different mean size.
The mean size of clusters for baryons is smaller than that of mesons. For the
same hadrons at different centrality classes, the mean size of clusters
decreases with the increase of centrality. The fragmentation functions for
cluster decay are different for different hadrons, while they are universal for
the same hadrons at different centrality classes. The universal scaling of the
meson and baryon spectra in the low $p_{\rm T}$ region can be quantitatively
understood with the CSP model at the same time. | nucl-th |
A Monte-Carlo Approach to Zero Energy Quantum Scattering: Monte-Carlo methods for zero energy quantum scattering are developed.
Starting from path integral representations for scattering observables, we
present results of numerical calculations for potential scattering and
scattering off a schematic $^4 \rm He $ nucleus. The convergence properties of
Monte-Carlo algorithms for scattering systems are analyzed using stochastic
differential equation as a path sampling method. | nucl-th |
A functional approach to nuclear electromagnetic response functions: The separated electromagnetic responses $R_L(q,\omega)$ and $R_T(q,\omega)$
for inclusive electron scattering off nuclei are studied within a functional
scheme. | nucl-th |
Identifying structures in the continuum: Application to $^{16}$Be: The population and decay of two-nucleon resonances offer exciting new
opportunities to explore dripline phenomena. The understanding of these systems
requires a solid description of the three-body (core+N+N) continuum. The
identification of a state with resonant character from the background of
non-resonant continuum states in the same energy range poses a theoretical
challenge. It is the purpose of this work to establish a robust theoretical
framework to identify and characterize three-body resonances in a discrete
basis. A resonance operator is proposed, which describes the sensitivity to
changes in the potential. Resonances are then identified from the lowest
eigenstates of the resonance operator. The operator is diagonalized in a basis
of Hamiltonian pseudostates, built within the hyperspherical harmonics
formalism using the analytical THO basis. The energy and width of the resonance
are determined from its time dependence. The method is applied to 16Be in a
14Be+n+n model. An effective core+n potential, fitted to the available
information on the subsystem 15Be, is employed. The 0+ ground state resonance
of 16Be presents a strong dineutron configuration, which favors the picture of
a correlated two-neutron emission. Fitting the three body interaction to the
experimental two-neutron separation energy |S2n|=1.35(10) MeV, the computed
width is Gamma(0+)=0.16 MeV. From the same Hamiltonian, a 2+ resonance is also
predicted with E_r(2+)=2.42 MeV and Gamma(2+)=0.40 MeV. The dineutron
configuration and the computed 0+ width are consistent with previous R-matrix
calculations for the true three-body continuum. The extracted values of the
resonance energy and width converge with the size of the pseudostate basis and
are robust under changes in the basis parameters. This supports the reliability
of the method in describing the properties of unbound core+N+N systems in a
discrete basis. | nucl-th |
Particle spectra and hydro-inspired models: Several popular parameterizations of the freeze-out conditions in
ultra-relativistic heavy-ion collisions are shortly reviewed. The common
features of the models, responsible for the successful description of hadronic
observables, are outlined. | nucl-th |
Shell-model interactions from chiral effective field theory: We construct valence-space Hamiltonians for use in shell-model calculations,
where the residual two-body interaction is based on symmetry principles and the
low-momentum expansion from chiral effective field theory. In addition to the
usual free-space contact interactions, we also include novel
center-of-mass--dependent operators that arise due to the Galilean invariance
breaking by in-medium effects. We fitted the low-energy constants to 441
ground- and excited-state energies in the sd shell and obtained a
root-mean-square derivation of 1.8 MeV at leading order and of 0.5 MeV at
next-to-leading order, with natural low-energy constants in all cases. The
developed chiral shell-model interactions enable order-by-order uncertainty
estimates and show promising predictions for neutron-rich isotopes beyond the
fitted data set. | nucl-th |
Hyperon mixing and universal many-body repulsion in neutron stars: A multi-pomeron exchange potential (MPP) is proposed as a model for the
universal many-body repulsion in baryonic systems on the basis of the Extended
Soft Core (ESC) bryon-baryon interaction. The strength of MPP is determined by
analyzing the nucleus-nucleus scattering with the G-matrix folding model. The
interaction in $\Lambda N$ channels is shown to reproduce well the experimental
$\Lambda$ binding energies. The equation of state (EoS) in neutron matter with
hyperon mixing is obtained including the MPP contribution, and mass-radius
relations of neutron stars are derived. It is shown that the maximum mass can
be larger than the observed one $2M_{\odot}$ even in the case of including
hyperon mixing on the basis of model-parameters determined by terrestrial
experiments. | nucl-th |
Nuclear Effects in Generators: the Path Forward: The extraction of neutrino oscillation parameters requires the determination
of the neutrino energy from observations of the hadronic final state. The use
of nuclear targets then requires the use of event generators to isolate the
interesting elementary processes and to take experimental acceptances into
account. In this talk I briefly summarize the history of event generators and
their use in nuclear physics, talk briefly about the generators used in the
neutrino community and then discuss future necessary developments. | nucl-th |
VISHNU hybrid model for viscous QCD matter at RHIC and LHC energies: In this proceeding, we briefly describe the viscous hydrodynamics + hadron
cascade hybrid model VISHNU for relativistic heavy ion collisions and report
the current status on extracting the QGP viscosity from elliptic flow data. | nucl-th |
Unitary limit and linear scaling of neutrons in harmonic trap with tuned
CD-Bonn and square-well interactions: We study systems of finite-number neutrons in a harmonic trap at the unitary
limit. Two very different types of neutron-neutron interactions are applied,
namely, the meson-theoretic CD-Bonn potential and hard-core square-well
interactions, all tuned to possess infinite scattering lengths, and with
effective ranges comparable to or larger than the trap size. The potentials are
renormalized to equivalent, scattering-length preserving low-momentum
potentials, $V_{{\rm low}-k}$, with which the particle-particle hole-hole ring
diagrams are summed to all orders to yield the ground-state energy $E_0$ of the
finite neutron system. We find the ratio $E_0/E_0^{\rm free}$ (where $E_0^{\rm
free}$ denotes the ground-state energy of the corresponding non-interacting
system) to be remarkably independent from variations of the harmonic trap
parameter, the number of neutrons, the decimation momentum of $V_{{\rm
low}-k}$, and the type and effective range of the unitarity potential. Our
results support a special virial linear scaling relation of $E_0$. Certain
properties of Landau's quasi-particles for trapped neutrons at the unitary
limit are also discussed. | nucl-th |
Magnetic dipole moments as a strong signature for $α$-clustering in
even-even self-conjugate nuclei: We investigate the magnetic dipole moments in even-even self-conjugate nuclei
from ${}^{12}\mathrm{C}$ to ${}^{44}\mathrm{Ti}$. For the latter, the measured
gyromagnetic factors of excited states turn out to assume the same value of $g
\approx + 0.5$ within statistical errors. This peculiar feature can be
interpreted on the basis of collective excitations of $\alpha$-clusters.
Analogously, the behaviour of the same observable is studied for all isotopes
obtained by adding one or two neutrons to the considered self-conjugate nuclei.
It is found that for the $N = Z + 1$ isotopes the $\alpha$-cluster structure
hardly contributes to the observed negative g- factor value, corroborating
molecular $\alpha$-cluster models. The addition of a further neutron, however,
restores the original $\alpha$-cluster g-factors, except for the semi-magic
isotopes, in which the deviations from $g \approx + 0.5$ can be associated with
the relevant shell closures. Secondly, we analyze the same observable in the
framework of a macroscopic $\alpha$-cluster model on a finite lattice of side
length $L$. We focus on the discretization effects induced in the magnetic
dipole moments of the $2_1^+$ and the $3_1^-$ states of ${}^{12}\mathrm{C}$ at
different values of the lattice spacing $a$. | nucl-th |
Compton scattering in a unitary approach with causality constraints: Pion-loop corrections for Compton scattering are calculated in a novel
approach based on the use of dispersion relations in a formalism obeying
unitarity. The basic framework is presented, including an application to
Compton scattering. In the approach the effects of the non-pole contribution
arising from pion dressing are expressed in terms of (half-off-shell) form
factors and the nucleon self-energy. These quantities are constructed through
the application of dispersion integrals to the pole contribution of loop
diagrams, the same as those included in the calculation of the amplitudes
through a K-matrix formalism. The prescription of minimal substitution is used
to restore gauge invariance. The resulting relativistic-covariant model
combines constraints from unitarity, causality, and crossing symmetry. | nucl-th |
Bremsstrahlung Spectrum in alpha Decay: Using our previous approach to electromagnetic emission during tunneling, an
explicit, essentially classical, formula describing the bremsstrahlung spectrum
in alpha decay is derived. The role of tunneling motion in photon emission is
discussed. The shape of the spectrum is a universal function of the ratio Eg/Eo
, where Eg is the photon energy and Eo is a characteristic energy depending
only on the nuclear charge and the energy of the alpha particle. | nucl-th |
N-Nucleon Effective Generators of the Poincare Group Derived from a
Field Theory: It is shown that the ten generators of the Poincare group acting in the Fock
space of nucleons and mesons and based on standard Lagrangians can be
blockdiagonalized by one and the same unitary transformation such that the
space of a fixed number of nucleons is separated from the rest of the Fock
space. The existence proof is carried through in a formal power series
expansion in the coupling constant to all orders. In this manner one arrives at
effective generators of the Poincare group which act in the two subspaces
separately. | nucl-th |
Coexistence of order and chaos at critical points of first-order quantum
phase transitions in nuclei: We study the interplay between ordered and chaotic dynamics at the critical
point of a generic first-order quantum phase transition in the interacting
boson model of nuclei. Classical and quantum analyses reveal a distinct
behavior of the coexisting phases. While the dynamics in the deformed phase is
robustly regular, the spherical phase shows strongly chaotic behavior in the
same energy intervals. The effect of collective rotations on the dynamics is
investigated. | nucl-th |
Approximations in Fusion and Breakup reactions induced by Radioactive
Beams: Some commonly used approximations for complete fusion and breakup
transmission coefficients in collisions of weakly bound projectiles at near
barrier energies are assessed. We show that they strongly depend on the adopted
classical trajectory and can be significantly improved with proper treatment of
the incident and emergent currents in the WKB approximation. | nucl-th |
Dynamic description of ternary and quaternary splits of heavy nuclear
systems in the deep-inelastic regime: Colliding heavy nuclear systems in the deep-inelastic regime may undergo
partitioning into multiple fragments when fusion can not be achieved. While
multiple breakups are common at Fermi energy, they are rather exotic in the
deep-inelastic regime, where density, excitation and, in general, transport
conditions, are expected to be different. Abundant ternary and quaternary
splits have been observed in recent experiments, for instance in symmetric
semi-central and semi-peripheral collisions with heavy systems, like
$^{197}\mathrm{Au}$ + $^{197}\mathrm{Au}$ at 15 MeV per nucleon. In these
conditions, we undertook a microscopic description of the reaction dynamics.
Relying on the full solution of the Boltzmann-Langevin equation implemented in
the BLOB approach, we could follow in time the development of instabilities
along deformation. | nucl-th |
Nucleon-Nucleon Short-Range Correlations and Gribov Inelastic Shadowing
in High Energy Hadron-Nucleus Collisions: Different types of high-energy hadron-nucleus cross sections are discussed
emphasizing the role played by Nucleon-Nucleon (NN) Short-Range Correlations
(SRC) and Gribov Inelastic Shadowing (IS) | nucl-th |
Identifying Inconsistencies in Fission Product Yield Evaluations with
Prompt Neutron Emission: We present a self-consistency analysis of fission product yield evaluations.
Anomalous yields are determined using a series of simple conservation checks
and comparing charge distributions with common parameterizations. The total
prompt neutron multiplicity as a function of product mass $\bar{\nu}_T(A)$ is
derived directly from the independent fission product yields using average
charge conservation. This method is checked against Monte Carlo simulations of
the de-excitation of the fission fragments in a Hauser-Feshbach statistical
decay framework. The derived $\bar{\nu}_T(A)$ is compared with experimental
data, when available, and used to compare the prompt neutron multiplicity
$\bar{\nu}$ for the various evaluations. Differences in $\bar{\nu}$ for each
evaluation are investigated and possible sources are identified. We also
identify fission reactions that are inconsistent with prompt neutron data and
propose possible solutions to remedy the observed inconsistencies. | nucl-th |
Nucleon mass and pion loops: Poincare' covariant Faddeev equations for the nucleon and Delta are solved to
illustrate that an internally consistent description in terms of confined-quark
and nonpointlike confined-diquark-correlations can be obtained. pi N-loop
induced self-energy corrections to the nucleon's mass are analysed and shown to
be independent of whether a pseudoscalar or pseudovector coupling is used.
Phenomenological constraints suggest that this self-energy correction reduces
the nucleon's mass by up to several hundred MeV. That effect does not
qualitatively alter the picture, suggested by the Faddeev equation, that
baryons are quark-diquark composites. However, neglecting the pi-loops leads to
a quantitative overestimate of the nucleon's axial-vector diquark component. | nucl-th |
Magnetic moment of the deuteron as probe of relativistic corrections: The calculation of the magnetic moment of the deuteron in the framework of
the Bethe--Salpeter approach is performed. The relativistic corrections are
calculated analytically and estimated numerically. It is shown that the main
contributions are due to partial waves with positive energies and $P$--waves. A
comparison with the non-relativistic schemes of calculations including mesonic
exchange currents is made. | nucl-th |
Exotic modes of excitation in atomic nuclei far from stability: We review recent studies of the evolution of collective excitations in atomic
nuclei far from the valley of $\beta$-stability. Collective degrees of freedom
govern essential aspects of nuclear structure, and for several decades the
study of collective modes such as rotations and vibrations has played a vital
role in our understanding of complex properties of nuclei. The multipole
response of unstable nuclei and the possible occurrence of new exotic modes of
excitation in weakly-bound nuclear systems, present a rapidly growing field of
research, but only few experimental studies of these phenomena have been
reported so far. Valuable data on the evolution of the low-energy dipole
response in unstable neutron-rich nuclei have been gathered in recent
experiments, but the available information is not sufficient to determine the
nature of observed excitations. Even in stable nuclei various modes of giant
collective oscillations had been predicted by theory years before they were
observed, and for that reason it is very important to perform detailed
theoretical studies of the evolution of collective modes of excitation in
nuclei far from stability. We therefore discuss the modern theoretical tools
that have been developed in recent years for the description of collective
excitations in weakly-bound nuclei. The review focuses on the applications of
these models to studies of the evolution of low-energy dipole modes from stable
nuclei to systems near the particle emission threshold, to analyses of various
isoscalar modes, those for which data are already available, as well as those
that could be observed in future experiments, to a description of
charge-exchange modes and their evolution in neutron-rich nuclei, and to
studies of the role of exotic low-energy modes in astrophysical processes. | nucl-th |
Pygmy Resonances and Neutron Skins: Motivated by a recent experiment, the distribution of electric dipole
strength in the neutron-rich 68Ni isotope was computed using a relativistic
random phase approximation with a set of effective interactions that - although
well calibrated - predict significantly different values for the neutron-skin
thickness in 208Pb. The emergence of low-energy "Pygmy" strength that exhausts
about 5-8% of the energy weighted sum rule (EWSR) is clearly identified. In
addition to the EWSR, special emphasis is placed on the dipole polarizability.
In particular, our results suggest a strong correlation between the dipole
polarizability of 68Ni and the neutron-skin thickness of 208Pb. Yet we find a
correlation just as strong and an even larger sensitivity between the
neutron-skin thickness of 208Pb and the fraction of the dipole polarizability
exhausted by the Pygmy resonance. These findings suggest that the dipole
polarizability may be used as a proxy for the neutron skin. | nucl-th |
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