Nuclear Theory·nucl-th

Friday·April 10, 2020

11 papers—4 primary·7 cross-listed

01
Dispersion relations applied to double-folding potentials from chiral EFT
Victoria Durant · Pierre Capel · Achim Schwenk
We present a determination of optical potentials using the double-folding method based on chiral effective field theory nucleon-nucleon interactions at next-to-next-to-leading order combined with dispersion relations to constrain the imaginary part. This approach is benchmarked on $^{16}$ O-- $^{16}$ O collisions, and extended to the $^{12}$ C-- $^{12}$ C and $^{12}$ C-- $^{16}$ O cases. Predictions derived from these potentials are compared to data for elastic scattering at energies up to 1000 MeV, as well as for fusion at low energy. Without adjusting parameters, excellent agreement with experiment is found. In addition, we study the sensitivity of the corresponding cross sections to the nucleon-nucleon interactions and nuclear densities used.
nucl-thPRC(2020)·13 citations
02
Microscopic description of fission in superheavy nuclei with the parametrization D1M $^{*}$ of the Gogny energy density functional
R. Rodríguez-Guzmán · Y.M. Humadi · L.M. Robledo
The constrained Hartree-Fock-Bogoliubov approximation, based on the recent parametrization D1M $^{*}$ of the Gogny energy density functional, is used to describe fission in 435 superheavy nuclei. The Gogny-D1M $^{*}$ parametrization is benchmarked against available experimental data on inner and second barrier heights, excitation energies of the fission isomers and half-lives in a selected set of Pu, Cm, Cf, Fm, No, Rf, Sg, Hs and Fl nuclei. Results are also compared with those obtained with the Gogny-D1M energy density functional. A detailed study of the minimal energy fission paths is carried out for isotopic chains with atomic numbers 100 $\leq$ Z $\leq$ 126 including very neutron-rich sectors up to around 4 MeV from the two-neutron driplines. Single-particle energies, ground state deformations, pairing correlations, two-nucleon separation energies and barrier heights are also discussed. In addition to fission paths, the constrained Hartree-Fock-Bogoliubov framework provides collective masses and zero-point quantum rotational and vibrational energies. Those quantities are building blocks within the Wentzel-Kramer-Brillouin formalism employed to evaluate the systematic of the spontaneous fission half-lives t $_{SF}$ . The competition between spontaneous fission and $α$ -decay is studied, through the computation of the $α$ -decay half-lives t $_{α}$ using a parametrization of the Viola-Seaborg formula. From the comparison with the available experimental data and the results obtained with other theoretical approaches, it is concluded that D1M $^{*}$ represents a reasonable starting point to describe fission in heavy and superheavy nuclei.
nucl-thEPJA(2020)·41 citations
03
Feeddown contributions from unstable nuclei in relativistic heavy-ion collisions
Volodymyr Vovchenko🇺🇸 · Benjamin Dönigus🇩🇪 · Behruz Kardan🇩🇪 · Manuel Lorenz🇩🇪 · Horst Stoecker🇩🇪
We estimate the feeddown contributions from decays of unstable $A = 4$ and $A = 5$ nuclei to the final yields of protons, deuterons, tritons, $^{3}$ He, and $^{4}$ He produced in relativistic heavy-ion collisions at $s_{NN} > 2.4$ GeV, using the statistical model. The feeddown contribution effects do not exceed 5% at LHC and top RHIC energies due to the large penalty factors involved, but are substantial at intermediate collision energies. We observe large feeddown contributions for tritons, $^{3}$ He, and $^{4}$ He at $s_{NN} ≲ 10$ GeV, where they may account for as much as 70% of the final yield at the lower end of the collision energies considered. Sizable ( $> 10$ %) effects for deuteron yields are observed at $s_{NN} ≲ 4$ GeV. The results suggest that the excited nuclei feeddown cannot be neglected in the ongoing and future analysis of light nuclei production at intermediate collision energies, including HADES and CBM experiments at FAIR, NICA at JINR, RHIC beam energy scan and fixed-target programmes, and NA61/SHINE at CERN. We further show that the freeze-out curve in the $T$ - $μ_{B}$ plane itself is affected significantly by the light nuclei at high baryochemical potential.
nucl-thhep-phnucl-exPLB(2020)·36 citations
04
Chiral Magnetic Effect in Isobar Collisions from Stochastic Hydrodynamics
Gui-Rong Liang🇨🇳 · Jinfeng Liao🇺🇸 · Shu Lin🇨🇳 · Li Yan🇨🇳 · Miao Li🇨🇳
We study chiral magnetic effect in collisions of AuAu, RuRu and ZrZr at s = 200GeV. The axial charge evolution is modeled with stochastic hydrodynamics and geometrical quantities are calculated with Monte Carlo Glauber model. By adjusting the relaxation time of magnetic field, we find our results in good agreement with background subtracted data for AuAu collisions at the same energy. We also make prediction for RuRu and ZrZr collisions. We find a weak centrality dependence of initial chiral imbalance, which implies the centrality dependence of chiral magnetic effect signal comes mainly from those of magnetic field and volume factor. Our results also show an unexpected dependence on system size: while the system of AuAu has larger chiral imbalance and magnetic field, it turns out to have smaller signal for chiral magnetic effect due to the larger volume suppression factor.
nucl-thnucl-exCPC(2020)·14 citations
05
Thermodynamically consistent equation of state for an accreted neutron star crust
Mikhail E. Gusakov · Andrey I. Chugunov
We study equation of state (EOS) of an accreting neutron star crust. Usually, such EOS is obtained assuming (implicitly) that the free (unbound) neutrons and nuclei in the inner crust move together. We argue, that this assumption violates the condition $μ_{n}^{\infty} = const$ , required for hydrostatic (and diffusion) equilibrium of unbound neutrons ( $μ_{n}^{\infty}$ is the redshifted neutron chemical potential). We construct a new EOS respecting this condition, working in the compressible liquid-drop approximation. We demonstrate that it is close to the catalyzed EOS in most part of the inner crust, being very different from EOSs of accreted crust discussed in the literature. In particular, the pressure at the outer-inner crust interface does not coincide with the neutron drip pressure, usually calculated in the literature, and is determined by hydrostatic (and diffusion) equilibrium conditions within the star. We also find an instability at the bottom of fully accreted crust that transforms nuclei into homogeneous nuclear matter. It guarantees that the structure of fully accreted crust remains self-similar during accretion.
↳ astro-ph.HEnucl-thPRL(2020)·41 citations
06
Studying the Landau mass parameter of the extended $σ$ - $ω$ model for neutron star matter
David E. Alvarez-Castillo🇵🇱 · Alexander Ayriyan🇷🇺 · Gergely Gábor Barnaföldi🇭🇺 · Péter Pósfay🇭🇺
We present a Bayesian analysis of the Landau mass within the extended $σ$ - $ω$ model for neutron star matter. To this purpose, we consider the mass measurement of the object PSR 0740+6620, the tidal deformability estimation from the GW170817 and the mass-radius estimate of PSR J0030+0451 by NICER. Using Landau mass as free parameter of the theory, we rely on the prediction power of the Bayesian method to find the best value for this nuclear quantity.
↳ astro-ph.HEastro-ph.SRhep-phnucl-thPhys.Part.Nucl.(2020)·12 citations
07
Trace preserving quantum dynamics using a novel reparametrization-neutral summation-by-parts difference operator
Oskar Ålund🇸🇪 · Yukinao Akamatsu🇯🇵 · Fredrik Laurén🇸🇪 · Takahiro Miura🇯🇵 · Jan Nordström🇸🇪 · Alexander Rothkopf🇳🇴
We develop a novel numerical scheme for the simulation of dissipative quantum dynamics following from two-body Lindblad master equations. All defining continuum properties of the Lindblad dynamics, hermiticity, positivity and in particular trace conservation of the evolved density matrix are preserved. The central ingredient is a new spatial difference operator, which not only fulfils the summation by parts (SBP) property but also implements a continuum reparametrization property. Using the time evolution of a heavy-quark anti-quark bound state in a hot thermal medium as an explicit example, we show how the reparametrization neutral summation-by-parts (RN-SBP) operator preserves the continuum properties of the theory.
↳ physics.comp-phhep-phnucl-thJ.Comput.Phys.(2021)·16 citations
08
Relativistic Cooper pairing in the microscopic limit of chiral random matrix theory
Takuya Kanazawa🇯🇵
Random matrix theory (RMT) provides a powerful framework for analyzing universal features of strongly coupled physical systems. In quantum chromodynamics (QCD), cold quark matter at asymptotically high density is expected to exhibit color superconductivity (CSC), the analogue of superconductivity in condensed-matter systems. Although CSC phases have been studied within RMT primarily in the macroscopic large- $N$ limit, where $N$ denotes the matrix size, it has remained unclear whether an RMT exists that realizes CSC in the microscopic large- $N$ limit. Here we answer this question in the affirmative by introducing a novel non-Hermitian chiral random matrix model. For three quark flavors, we show that the model exhibits spontaneous breaking of color $SU (3)$ and flavor $SU (3)$ symmetries down to the diagonal $SU (3)$ subgroup, thereby reproducing color-flavor locking in dense QCD. For two flavors, we find that color $SU (3)$ is spontaneously broken to $SU (2)$ while the chiral symmetry $SU (2)_{L} \times SU (2)_{R}$ remains unbroken, consistent with the two-flavor color-superconducting phase.
↳ hep-thhep-latmath-phmath.MP+1Mod.Phys.Lett.A(2026)·2 citations
09
Magneto-Seebeck coefficient and Nernst coefficient of hot and dense hadron gas
Arpan Das🇵🇱 · Hiranmaya Mishra🇮🇳 · Ranjita K. Mohapatra🇮🇳
We discuss the thermoelectric effect of hot and dense hadron gas within the framework of the hadron resonance gas model. Using the relativistic Boltzmann equation within the relaxation time approximation we estimate the Seebeck coefficient of the hot and dense hadronic medium with a gradient in temperature and baryon chemical potential. The hadronic medium in this calculation is modeled by the hadron resonance gas (HRG) model with hadrons and their resonances up to a mass cutoff $Λ \sim 2.6$ GeV. We also extend the formalism of the thermoelectric effect for a nonvanishing magnetic field. The presence of magnetic field also leads to a Hall type thermoelectric coefficient (Nernst coefficient) for the hot and dense hadronic matter apart from a magneto-Seebeck coefficient. We find that generically in the presence of a magnetic field Seebeck coefficient decreases while the Nernst coefficient increases with the magnetic field. At higher temperature and/or baryon chemical potential these coefficients approach to their values at vanishing magnetic field.
↳ hep-phnucl-thPRD(2020)·31 citations
10
Freeze-out and thermalization in relativistic heavy ion collisions
Sourendu Gupta🇮🇳 · Debasish Mallick🇮🇳 · Dipak Kumar Mishra🇮🇳 · Bedangadas Mohanty🇮🇳 · Nu Xu🇨🇳
High energy heavy-ion collisions in laboratory produce a form of matter that can test Quantum Chromodynamics (QCD), the theory of strong interactions, at high temperatures. One of the exciting possibilities is the existence of thermodynamically distinct states of QCD, particularly a phase of de-confined quarks and gluons. An important step in establishing this new state of QCD is to demonstrate that the system has attained thermal equilibrium. We present a test of thermal equilibrium by checking that the mean hadron yields produced in the small impact parameter collisions as well as grand canonical fluctuations of conserved quantities give consistent temperature and baryon chemical potential for the last scattering surface. This consistency for moments up to third order of the net-baryon number, charge, and strangeness is a key step in the proof that the QCD matter produced in heavy-ion collision attains thermal equilibrium. It is a clear indication for the first time, using fluctuation observables, that a femto-scale system attains thermalization. The study also indicates that the relaxation time scales for the system are comparable to or smaller than the life time of the fireball.
↳ hep-phnucl-exnucl-th15 citations
11
Hierarchy of kinetic freeze-out parameters in low energy heavy-ion collisions
Sudhir Pandurang Rode🇮🇳 · Partha Pratim Bhaduri🇮🇳 · Amaresh Jaiswal🇮🇳 · Ankhi Roy🇮🇳
We study the mass dependent hierarchy of kinetic freeze-out parameters of hadrons in low energy heavy-ion collisions. For this purpose, the transverse momentum and rapidity spectra of the identified hadrons produced in central Pb+Pb collisions, available at SPS energies ranging from $E_{Lab} = 20A - 158A$ GeV, are analyzed within a generalized non boost-invariant blast wave model. We consider separate simultaneous fits for light hadrons ( $π^{-}$ , $K^{\pm}$ ) and heavy strange hadrons ( $Λ$ , $Λ ˉ$ , $ϕ$ , $Ξ^{\pm}$ , $Ω^{\pm}$ ), for which the transverse momentum spectra as well as rapidity spectra are available. We also perform a separate fit to transverse momentum spectra of charmonia ( $J /Ψ$ , $Ψ^{'}$ ) at $158 A$ GeV collisions. We find a clear mass dependent hierarchy in the fitted kinetic freeze-out parameters. Further, we study the rapidity spectra using analytical Landau flow solution for non-conformal systems. We find that the fitted value of sound velocity in the medium also shows a similar hierarchy.
↳ hep-phnucl-thPRC(2020)·8 citations

Affiliations

first authorsco-authorsvia INSPIRE