Nuclear Theory·nucl-th

Tuesday·October 18, 2016

14 papers—11 primary·3 cross-listed

01
[Submitted on 15 Oct 2016]
Study of Lambda polarization in relativistic nuclear collisions at sqrt{s}_NN = 7.7-200 GeV
Iu. Karpenko (INFN Florence)🇺🇦 · F. Becattini (U. Florence)🇮🇹
We present a calculation of the global polarization of Lambda hyperons in relativistic Au-Au collisions at RHIC Beam Energy Scan range sqrt{s}_NN = 7.7 - 200 GeV with a 3+1 dimensional cascade + viscous hydro + cascade model, UrQMD+vHLLE. Within this model, the mean polarization of Lambda in the out-of-plane direction is predicted to decrease rapidly with collision energy from a top value of about 2% at the lowest energy examined. We explore the connection between the polarization signal and thermal vorticity and estimate the feed-down contribution to Lambda polarization due to the decay of higher mass hyperons.
Comments:
10 pages, 9 figures. Final version published in EPJC
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1610.04717 [pdf]
EPJC(2017)·307 citations
02
[Submitted on 15 Oct 2016]
Microscopic folding model analysis of the radiative $(n, γ)$ reactions near the $Z = 28$ shell-closure and the weak s-process
Saumi Dutta · G. Gangopadhyay · Abhijit Bhattacharyya
The radiative thermal neutron capture cross sections over the range of thermal energies from 1 keV to 1 MeV are studied in statistical Hauser-Feshbach formalism. The optical model potential is constructed by folding the density dependent M3Y nucleon-nucleon interaction with radial matter densities of target nuclei obtained from relativistic-mean-field (RMF) theory. The standard nuclear reaction code TALYS1.8 is used for calculation of cross sections. The nuclei studied in the present work reside near the $Z = 28$ proton shell closure and are of astrophysical interests taking part in p-, s-, and r-process of nucleosynthesis. The Maxwellian-averaged cross-section (MACS) values for energies important for astrophysical applications are presented.
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1610.04726 [pdf]
PRC(2016)·10 citations
03
[Submitted on 15 Oct 2016]
Initial partonic eccentricity fluctuations in a multi-phase transport model
L. Ma🇨🇳 · G.L. Ma🇨🇳 · Y. G. Ma🇨🇳
Initial partonic eccentricities in Au+Au collisions at center-of-mass energy $s_{N N}$ = 200 GeV are investigated using a multi-phase transport model with string melting scenario. The initial eccentricities in different order of harmonics are studied using participant and cumulant definitions. Eccentricity in terms of second-, fourth- and sixth order cumulants as a function of number of participant nucleons are compared systematically with the traditional participant definition. The ratio of the cumulant eccentricities $ε {4} / ε {2}$ and $ε {6} / ε {4}$ are studied in comparison with the ratio of the corresponding flow harmonics. The conversion coefficients ( $v_{n} / ε_{n}$ ) are explored up to fourth order harmonic based on cumulant method. Furthermore, studies on transverse momentum ( $p_{T}$ ) and pseudo-rapidity ( $η$ ) dependencies of eccentricities and their fluctuations are presented. As in ideal hydrodynamics initial eccentricities are expected to be closely related to the final flow harmonics in relativistic heavy-ion collisions, studies of the fluctuating initial condition in the AMPT model will shed light on the tomography properties of the initial source geometry.
Comments:
13 pages, 8 figures; accepted by Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1610.04733 [pdf]
PRC(2016)·30 citations
04
[Submitted on 15 Oct 2016]
Thermal and transport properties in central heavy-ion reactions around a few hundred MeV/nucleon
X. G. Deng🇨🇳 · Y. G. Ma🇨🇳 · M. Veselsky🇸🇰
Thermalization process of nuclear matter in central fireball region of heavy-ion collisions is investigated by employing an extension model of Boltzmann-Uehling-Uhlenbeck, namely the Van der Waals Boltzmann-Uehling-Uhlenbeck (VdWBUU) model. Temperature ( $T$ ) is extracted by the quantum Fermion fluctuation approach and other thermodynamic quantities, such as density ( $ρ$ ), entropy density ( $s$ ), shear viscosity ( $η$ ), isospin diffusivity ( $D_{I}$ ) and heat conductivity ( $κ$ ), are also deduced. The liquid-like and gas-like phase signs are discussed through the behavior of shear viscosity during heavy-ion collisions process with the VdWBUU model.
Comments:
9 pages, 12 figures; accepted by Phys. Rev. C
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
1610.04736 [pdf]
PRC(2016)·20 citations
05
[Submitted on 16 Oct 2016]
Bohr Hamiltonian with an energy dependent $γ$ -unstable Coulomb-like potential
R. Budaca
An exact analytical solution for the Bohr Hamiltonian with an energy dependent Coulomb-like $γ$ -unstable potential is presented. Due to the linear energy dependence of the potential's coupling constant, the corresponding spectrum in the asymptotic limit of the slope parameter resembles the spectral structure of the spherical vibrator, however with a different state degeneracy. The parameter free energy spectrum as well as the transition rates for this case are given in closed form and duly compared with those of the harmonic $U (5)$ dynamical symmetry. The model wave functions are found to exhibit properties that can be associated to shape coexistence. A possible experimental realization of the model is found in few medium nuclei with a very low second $0^{+}$ state known to exhibit competing prolate, oblate and spherical shapes.
Comments:
11 pages, 4 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1610.04899 [pdf]
EPJA(2016)·14 citations
06
[Submitted on 17 Oct 2016]
Pigmy resonances, transfer, and separable potentials
C.A. Bertulani🇺🇸 · A. S. Kadyrov · A. Kruppa · T. V. Nhan Hao · A. M. Mukhamedzhanov · Shubhchintak
In this contribution we make a short review of recent progress on topics of current interest in nuclear physics and nuclear astrophysics. In particular, we discuss a re-analysis of the extraction of the dipole response of the pigmy resonance in $^{68}$ Ni based on a continuum discretized coupled-channels calculation in relativistic Coulomb excitation experiments. We also discuss the forthcoming progresses made by our group on the Alt-Sandhas-Grassberber approach to (d,p) reactions and future expectations. The role of separable potentials in solving such equations with a test case based on applications of such potentials to phase-shift analysis is also presented.
Comments:
Carpathian Summer School of Physics 2016,Exotic Nuclei and Nuclear/Particle Physics VI, "Physics with small accelerators", eds. L. Trache et al. 9 pages, 6 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1610.04942 [pdf]
AIP Conf.Proc.(2017)·0 citations
07
[Submitted on 17 Oct 2016]
Diffractive charmonium spectrum in high energy collisions in the basis light-front quantization approach
Guangyao Chen🇺🇸 · Yang Li🇺🇸 · Pieter Maris🇺🇸 · Kirill Tuchin🇺🇸 · James P. Vary🇺🇸
Using the charmonium light-front wavefunctions obtained by diagonalizing an effective Hamiltonian with the one-gluon exchange interaction and a confining potential inspired by light-front holography in the basis light-front quantization formalism, we compute production of charmonium states in diffractive deep inelastic scattering and ultra-peripheral heavy ion collisions within the dipole picture. Our method allows us to predict yields of all vector charmonium states below the open flavor thresholds in high-energy deep inelastic scattering, proton-nucleus and ultra-peripheral heavy ion collisions, without introducing any new parameters in the light-front wavefunctions. The obtained charmonium cross section is in reasonable agreement with experimental data at HERA, RHIC and LHC. We observe that the cross-section ratio $σ_{Ψ (2 s)} / σ_{J /Ψ}$ reveals significant independence of model parameters.
Comments:
12 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1610.04945 [pdf]
PLB(2017)·34 citations
08
[Submitted on 17 Oct 2016]
Dynamics of the tri-nuclear system at spontaneous fission of $^{252}$ Cf
R.B. Tashkhodjaev (1) · (2) · A.K. Nasirov (3) · E.Kh. Alpomeshev (1) ((1) National University of Uzbekistan, Tashkent, Uzbekistan, (2) Inha University in Tashkent, Uzbekistan, (3) BLTP, Joint Institute for Nuclear Research, Dubna, Russia)
To describe of dynamics of ternary fission of $^{252}$ Cf an equation of motion of the tri-nuclear system is calculated. The fission of the $^{70}$ Ni+ $^{50}$ Ca+ $^{132}$ Sn channel was chosen as one of the more probable channels of true ternary fission of $^{252}$ Cf. The collinearity of ternary fission has been checked by analyzing results of the equation of motion. The results show that if initially all nuclei are placed collinearly (potential energy of this position is the smallest) and the component of the middle fragment's initial velocity which is perpendicular to this line, is zero then ternary fission is collinear, otherwise the non collinear ternary fission takes place.
Comments:
7 pages, 10 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1610.04981 [pdf]
PRC(2016)·13 citations
09
[Submitted on 17 Oct 2016]
Radiative corrections to the magnetic moments of the proton and the neutron
N. Kaiser🇩🇪
We estimate the radiative corrections of order $α / π$ to the magnetic moments of the proton and the neutron. The photon-loop diagram of the vertex-correction type is evaluated with phenomenological nucleon vector form factors. Infrared-finiteness and gauge-invariance require the inclusion of the wave-function renormalization factor from the self-energy diagram. Using recent empirical form factor parametrizations the corrections amount to $δ κ_{p} = - 3.42 \cdot 1 0^{- 3}$ and $δ κ_{n} = 1.34 \cdot 1 0^{- 3}$ . We study also the effects from photon-loops with internal $Δ (1232)$ -isobars. For two customary versions of the $Δ N γ$ -vertex and spin-3/2 propagator, these radiative corrections have values of $δ κ_{p}^{(Δ)} = (- 0.9, 0.0) \cdot 1 0^{- 3}$ and $δ κ_{n}^{(Δ)} = (1.2, - 0.8) \cdot 1 0^{- 3}$ , respectively.
Comments:
15 pages, 8 figures, 3 tables
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1610.05132 [pdf]
J.Phys.G(2017)·2 citations
10
[Submitted on 17 Oct 2016]
Pairing in neutron matter: New uncertainty estimates and three-body forces
C. Drischler · T. Krüger · K. Hebeler · A. Schwenk
We present solutions of the BCS gap equation in the channels $^{1} S_{0}$ and $^{3} P_{2} -^{3} F_{2}$ in neutron matter based on nuclear interactions derived within chiral effective field theory (EFT). Our studies are based on a representative set of nonlocal nucleon-nucleon (NN) plus three-nucleon (3N) interactions up to next-to-next-to-next-to-leading order (N $^{3}$ LO) as well as local and semilocal chiral NN interactions up to N $^{2}$ LO and N $^{4}$ LO, respectively. In particular, we investigate for the first time the impact of subleading 3N forces at N $^{3}$ LO on pairing gaps and also derive uncertainty estimates by taking into account results for pairing gaps at different orders in the chiral expansion. Finally, we discuss different methods for obtaining self-consistent solutions of the gap equation. Besides the widely-used quasi-linear method by Khodel et al. we demonstrate that the modified Broyden method is well applicable and exhibits a robust convergence behavior. In contrast to Khodel's method it is based on a direct iteration of the gap equation without imposing an auxiliary potential and is straightforward to implement.
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE)
arXiv:
1610.05213 [pdf]
PRC(2017)·52 citations
11
[Submitted on 17 Oct 2016]
Ab Initio Description of Open-Shell Nuclei: Merging No-Core Shell Model and In-Medium Similarity Renormalization Group
Eskendr Gebrerufael · Klaus Vobig · Heiko Hergert · Robert Roth
We merge two successful ab initio nuclear-structure methods, the no-core shell model (NCSM) and the multi-reference in-medium similarity renormalization group (IM-SRG) to define a new many-body approach for the comprehensive description of ground and excited states of closed and open-shell nuclei. Building on the key advantages of the two methods---the decoupling of excitations at the many-body level in the IM-SRG and the access to arbitrary nuclei, eigenstates, and observables in the NCSM---their combination enables fully converged no-core calculations for an unprecedented range of nuclei and observables at moderate computational cost. We present applications in the carbon and oxygen isotopic chains, where conventional NCSM calculations are still feasible and provide an important benchmark. The efficiency and rapid convergence of the new approach make it ideally suited for ab initio studies of the complete spectroscopy of nuclei up into the medium-mass regime.
Comments:
5 pages, 4 figures, v2: update to published version
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1610.05254 [pdf]
PRL(2017)·91 citations

Affiliations

first authorsco-authorsvia INSPIRE