Nuclear Theory·nucl-th

Thursday·March 10, 2016

12 papers—9 primary·3 cross-listed

01
Insight from elliptic flow of open charm mesons using quark coalescence model at RHIC and LHC energies
Roli Esha🇺🇸 · Md. Nasim🇺🇸 · Huan Zhong Huang🇺🇸
A study of elliptic flow of open charm mesons, $D^{0}$ and $D_{S}^{\pm}$ using quark coalescence as a mechanism of hadronization of heavy quarks implemented in conjunction with A Multi Phase Transport (AMPT) model has been presented. We have studied the transverse momentum dependence of the elliptic flow parameter at mid-rapidity ( $∣ y ∣$ $<$ 1.0) for Au+Au collisions at $s_{N N} = 200$ GeV (RHIC) and Pb+Pb collisions at $s_{N N} = 2.76$ TeV (LHC) for different values of partonic interaction cross-section and QCD coupling constant. We have compared our calculations with the experimentally measured data at the LHC energy. We have also studied the effect of shear viscosity on elliptic flow of open charm mesons within the transport model approach. Our study indicates that the elliptic flow of open charmed mesons is more sensitive to viscous properties of QGP medium as compared to light charged hadrons.
nucl-thhep-phnucl-exJ.Phys.G(2017)·15 citations
02
Baryons and the Borromeo
Craig D. Roberts🇺🇸 · Jorge Segovia🇩🇪
The kernels in the tangible matter of our everyday experience are composed of light quarks. At least, they are light classically; but they don't remain light. Dynamical effects within the Standard Model of Particle Physics change them in remarkable ways, so that in some configurations they appear nearly massless, but in others possess masses on the scale of light nuclei. Modern experiment and theory are exposing the mechanisms responsible for these remarkable transformations. The rewards are great if we can combine the emerging sketches into an accurate picture of confinement, which is such a singular feature of the Standard Model; and looming larger amongst the emerging ideas is a perspective that leads to a Borromean picture of the proton and its excited states.
nucl-thhep-lathep-phnucl-exFew Body Syst.(2016)·21 citations
03
Baryon Octet Electromagnetic Form Factors in a confining NJL model
Manuel E. Carrillo-Serrano🇦🇺 · Wolfgang Bentz🇯🇵 · Ian C. Cloët🇺🇸 · Anthony W. Thomas🇦🇺
Electromagnetic form factors of the baryon octet are studied using a Nambu--Jona-Lasinio model which utilizes the proper-time regularization scheme to simulate aspects of colour confinement. In addition, the model also incorporates corrections to the dressed quarks from vector meson correlations in the t-channel and the pion cloud. Comparison with recent chiral extrapolations of lattice QCD results shows a remarkable level of consistency. For the charge radii we find the surprising result $r_{E}^{p} < r_{E}^{Σ^{+}}$ and $∣ r_{E}^{n} ∣ < ∣ r_{E}^{Ξ^{0}} ∣$ , whereas the magnetic radii have a pattern largely consistent with a naive expectation based on the dressed quark masses.
nucl-thPLB(2016)·26 citations
04
Neutrino emission, Equation of State and the role of strong gravity
O. L. Caballero🇨🇦
Neutron-star mergers are interesting for several reasons: they are proposed as the progenitors of short gamma-ray bursts, they have been speculated to be a site for the synthesis of heavy elements, and they emit gravitational waves possibly detectable at terrestrial facilities. The understanding of the merger process, from the pre-merger stage to the final compact object-accreting system involves detailed knowledge of numerical relativity and nuclear physics. In particular, key ingredients for the evolution of the merger are neutrino physics and the matter equation of state. We present some aspects of neutrino emission from binary neutron star mergers showing the impact that the equation of state has on neutrinos and discuss some spectral quantities relevant to their detection such as energies and luminosities far from the source.
nucl-thastro-ph.HEAIP Conf.Proc.(2016)·4 citations
05
Improvement on Fermionic properties and new isotope production in molecular dynamics simulations
Ning Wang🇨🇳 · Tong Wu🇨🇳 · Jie Zeng🇨🇳 · Yongxu Yang🇨🇳 · Li Ou🇨🇳
By considering momentum transfer in the Fermi constraint procedure, the stability of the initial nuclei and fragments produced in heavy-ion collisions can be further improved in the quantum molecular dynamics simulations. The case of the phase space occupation probability larger than one is effectively reduced with the proposed procedure. Simultaneously, the energy conservation can be better described for both individual nuclei and heavy-ion reactions. With the revised version of the improved quantum molecular dynamics (ImQMD) model, the fusion excitation functions of $^{16}$ O+ $^{186}$ W and the central collisions of Au+Au at 35 AMeV are re-examined. The fusion cross sections at sub-barrier energies and the charge distribution of fragments are relatively better reproduced due to the reduction of spurious nucleon emission. The charge and isotope distribution of fragments in Xe+Sn, U+U and Zr+Sn at intermediate energies are also predicted. More unmeasured extremely neutron-rich fragments with $Z = 16 - 28$ are observed in the central collisions of $^{238}$ U+ $^{238}$ U than that of $^{96}$ Zr+ $^{124}$ Sn, which indicates that multi-fragmentation of U+U may offer a fruitful pathway to new neutron-rich isotopes.
nucl-thJ.Phys.G(2016)·9 citations
06
Mean-field study of hot beta-stable protoneutron star matter: Impact of the symmetry energy and nucleon effective mass
Ngo Hai Tan🇻🇳 · Doan Thi Loan🇻🇳 · Dao T. Khoa🇻🇳 · Jerome Margueron
A consistent Hartree-Fock study of the equation of state (EOS) of asymmetric nuclear matter at finite temperature has been performed using realistic choices of the effective, density dependent nucleon-nucleon (NN) interaction, which were successfully used in different nuclear structure and reaction studies. Given the importance of the nuclear symmetry energy in the neutron star formation, EOS's associated with different behaviors of the symmetry energy were used to study hot asymmetric nuclear matter. The slope of the symmetry energy and nucleon effective mass with increasing baryon density was found to affect the thermal properties of nuclear matter significantly. Different density dependent NN interactions were further used to study the EOS of hot protoneutron star (PNS) matter of the $n p e μν$ composition in $β$ -equilibrium. The hydrostatic configurations of PNS in terms of the maximal gravitational mass $M_{max}$ and radius, central density, pressure and temperature at the total entropy per baryon $S / A = 1, 2$ and 4 have been determined in both the neutrino-free and neutrino-trapped scenarios. The obtained results show consistently a strong impact of the symmetry energy and nucleon effective mass on thermal properties and composition of hot PNS matter. $M_{max}$ values obtained for the (neutrino-free) $β$ -stable PNS at $S / A = 4$ were used to assess time $t_{BH}$ of the collapse of 40 $M_{⊙}$ protoneutron progenitor to black hole, based on a correlation between $t_{BH}$ and $M_{max}$ found from the hydrodynamic simulation by Hempel {\it et al.}.
nucl-thastro-ph.SRnucl-exPRC(2016)·24 citations
07
Hadron production within PHSD
Pierre Moreau🇩🇪 · Wolfgang Cassing🇩🇪 · Alessia Palmese🇩🇪 · Elena Bratkovskaya🇩🇪
We study the production of hadrons in nucleus-nucleus collisions within the Parton-Hadron-String Dynamics (PHSD) transport approach that is extended to incorporate essentials aspects of chiral symmetry restoration (CSR) in the hadronic sector (via the Schwinger mechanism) on top of the deconfinement phase transition as implemented in PHSD. The essential impact of CSR is found in the Schwinger mechanism (for string decay) which fixes the ratio of strange to light quark production in the hadronic medium. Our studies provide a microscopic explanation for the maximum in the $K^{+} / π^{+}$ ratio at about 30 A GeV which only shows up if in addition to CSR a deconfinement transition to partonic degrees-of-freedom is incorporated in the reaction dynamics.
nucl-thhep-phActa Phys.Polon.Supp.(2016)·0 citations
08
Divergence of the isospin-asymmetry expansion of the nuclear equation of state in many-body perturbation theory
Corbinian Wellenhofer🇩🇪 · Jeremy W. Holt🇺🇸 · Norbert Kaiser🇩🇪
The isospin-asymmetry dependence of the nuclear matter equation of state obtained from microscopic chiral two- and three-body interactions in second-order many-body perturbation theory is examined in detail. The quadratic, quartic and sextic coefficients in the Maclaurin expansion of the free energy per particle of infinite homogeneous nuclear matter with respect to the isospin asymmetry are extracted numerically using finite differences, and the resulting polynomial isospin-asymmetry parametrizations are compared to the full isospin-asymmetry dependence of the free energy. It is found that in the low-temperature and high-density regime where the radius of convergence of the expansion is generically zero, the inclusion of higher-order terms beyond the leading quadratic approximation leads overall to a significantly poorer description of the isospin-asymmetry dependence. In contrast, at high temperatures and densities well below nuclear saturation density, the interaction contributions to the higher-order coefficients are negligible and the deviations from the quadratic approximation are predominantly from the noninteracting term in the many-body perturbation series. Furthermore, we extract the leading logarithmic term in the isospin-asymmetry expansion of the equation of state at zero temperature from the analysis of linear combinations of finite differences. It is shown that the logarithmic term leads to a considerably improved description of the isospin-asymmetry dependence at zero temperature.
nucl-thPRC(2016)·82 citations
09
Quantum canonical ensemble and correlation femtoscopy at fixed multiplicities
S.V. Akkelin🇺🇦 · Yu.M. Sinyukov🇺🇦
Identical particle correlations at fixed multiplicity are considered by means of quantum canonical ensemble of finite systems. We calculate one-particle momentum spectra and two-particle Bose-Einstein correlation functions in the ideal gas by using a recurrence relation for the partition function. Within such a model we investigate the validity of the thermal Wick's theorem and its applicability for decomposition of the two-particle distribution function. The dependence of the Bose-Einstein correlation parameters on the average momentum of the particle pair is also investigated. Specifically, we present the analytical formulas that allow one to estimate the effect of suppressing the correlation functions in a finite canonical system. The results can be used for the femtoscopy analysis of the A+A and p+p collisions with selected (fixed) multiplicity.
nucl-thhep-exhep-phnucl-exPRC(2016)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE