Nuclear Theory·nucl-th

Thursday·July 23, 2020

8 papers—3 primary·5 cross-listed

01
Nucleus giant resonances from an improved isospin-dependent Boltzmann-Uehling-Uhlenbeck transport approach
Jun Xu · Wen-Tao Qin
We have studied the isoscalar giant quadruple resonance (ISGQR) and the isovector giant dipole resonance (IVGDR) in $^{208}$ Pb based on an improved isospin-dependent Boltzmann-Uehling-Uhlenbeck transport approach using an improved isospin- and momentum-dependent interaction. With the isoscalar nucleon effective mass and the nucleon-nucleon cross section which reproduces respectively the excitation energy and the width of the ISGQR strength function, the slope parameter of the symmetry energy and the neutron-proton effective mass splitting are constrained respectively within $36 < L < 62$ MeV and $0.08 δ < (m_{n 0}^{*} - m_{p 0}^{*}) / m < 0.42 δ$ , by comparing the resulting centroid energy of the IVGDR and the electric dipole polarizability with the experimental data. It is found that nucleon-nucleon collisions have considerable effects on the resulting electric dipole polarizability, which needs to be measured more accurately in order to pin down isovector nuclear interactions.
nucl-thnucl-exPRC(2020)·22 citations
02
Comment on "Quasielastic lepton scattering and back-to-back nucleons in the short-time approximation", by S. Pastore et al
Omar Benhar
The article of Pastore et al, while proposing an interesting and potentially useful approach for the generalisation of Quantum Monte Carlo techniques to the treatment of the nuclear electromagnetic response, features an incorrect and misleading discussion of y-scaling. The response to interactions with transversely polarised virtual photons receives sizeable contributions from non-scaling processes, in which the momentum transfer is shared between two nucleons. It follows that, contrary to what is stated by the the authors, y-scaling in the transverse channel is accidental.
nucl-thPRC(2022)·2 citations
03
Perturbative Approach to Effective Shell-Model Hamiltonians and Operators
L. Coraggio🇮🇹 · N. Itaco🇮🇹
The aim of this work is to present an overview of the derivation of the effective shell-model Hamiltonian and decay operators within many-body perturbation theory, and to show the results of selected shell-model studies based on their utilisation. More precisely, we report some technical details that are needed by non-experts to approach the derivation of shell-model Hamiltonians and operators starting from realistic nuclear potentials, in order to provide some guidance to shell-model calculations where the single-particle energies, two-body matrix elements of the residual interaction, effective charges and decay matrix elements, are all obtained without resorting to empirical adjustments. On the above grounds, we will present results of studies of double-beta decay of heavy-mass nuclei where shell-model ingredients are derived from theory, so to assess the reliability of such a way to shell-model investigations. Attention will be also focussed on the relevant aspects that are connected to the behavior of the perturbative expansion, whose knowledge is needed to establish limits and perspectives of this approach to nuclear structure calculations.
nucl-thFront.in Phys.(2020)·37 citations
04
Heavy meson tomography of cold nuclear matter at the electron-ion collider
Hai Tao Li🇺🇸 · Ze Long Liu🇺🇸 · Ivan Vitev🇺🇸
An important part of the physics program at the future electron-ion collider is to understand the nature of hadronization and the transport of energy and matter in large nuclei. Open heavy flavor production in deep inelastic scattering provides a new tool to address these critical questions. We present the first calculation of D-mesons and B-meson cross sections in electron-nucleus collisions at the EIC by including both next-to-leading order QCD corrections and cold nuclear matter effects. Our formalism employs generalized DGLAP evolution to include the contribution of in-medium parton showers, and is based on methods developed in soft-collinear effective theory with Glauber gluons that describe inclusive hadron production in reactions with nucleons and nuclei. The comprehensive study summarized here allows us to identify the optimal observables, center-of-mass energies, and kinematic regions most sensitive to the physics of energy loss and hadronization at the EIC.
↳ hep-phhep-exnucl-thPLB(2021)·40 citations
05
$Ω$ -dibaryon production with hadron interaction potential from the lattice QCD in relativistic heavy-ion collisions
S. Zhang🇨🇳 · Y. G. Ma🇨🇳
Recently the HAL QCD Collaboration reported the $Ω - Ω$ and $N - Ω$ interaction potentials by the lattice QCD simulations. Based on these results, $N Ω$ ( $^{5} S_{2}$ ) and $ΩΩ$ ( $^{1} S_{0}$ ) bound states were predicted with the binding energy about a few MeV. In addition, $N - Ω$ HBT correlation function was also measured by the STAR Collaboration as well as the ALICE Collaboration. These results provide dynamical information whether or not $Ω$ -dibaryons exist in the interaction aspects. Another necessary point for the detection of $Ω$ -dibaryons is the experimental environment where the bound state could be produced and survived in the system. In this context, there are at least two necessary conditions to constrain the production probability of $Ω$ -dibaryons, i.e. the one is the necessary short-range attractive interaction to form the bound state and the another is the experimental environment such as heavy-ion collision provides abundant enough strangeness and multiplicity of nucleons. In this Letter the $Ω - Ω$ and $Ω -$ nucleon interaction potentials by the lattice QCD simulations were employed to obtain $ΩΩ$ ( $^{1} S_{0}$ ) and $N Ω$ ( $^{5} S_{2}$ ) wave functions, and then the productions of $Ω$ -dibaryons were estimated by using of a dynamical coalescence mechanism for the relativistic heavy-ion collisions at $s_{N N} =$ 200 GeV and 2.76 TeV.
↳ hep-phnucl-exnucl-thPLB(2020)·19 citations
06
Extracting dynamics in the fusion of neutron-rich light nuclei
R.T. deSouza · Varinderjit Singh · S. Hudan · Z. Lin · C.J. Horowitz
The dependence of fusion dynamics on neutron excess for light nuclei is extracted. This is accomplished by comparing the average fusion cross-section at energies just above the fusion barrier for $^{12 - 15}$ C + $^{12}$ C with measurements of the interaction cross-section from high evergy collisions. The experimental results indicate that the fusion cross-section associated with dynamics increases with increasing neutron excess. Calculations with a time-dependent Hartree-Fock model fail to describe the observed trend.
↳ nucl-exnucl-th0 citations
07
Nuclear pasta in hot and dense matter and its influence on the equation of state for astrophysical simulations
Fan Ji🇨🇳 · Jinniu Hu🇨🇳 · Shishao Bao🇨🇳 · Hong Shen🇨🇳
We explore the properties of nuclear pasta appearing in supernova matter, i.e., matter at finite temperature with a fixed proton fraction. The pasta phases with a series of geometric shapes are studied using the compressible liquid-drop (CLD) model, where nuclear matter separates into a dense liquid phase of nucleons and a dilute gas phase of nucleons and $α$ particles. The equilibrium conditions for two coexisting phases are derived by minimization of the total free energy including the surface and Coulomb contributions, which are clearly different from the Gibbs conditions for phase equilibrium due to the finite-size effects. Compared to the results considering only spherical nuclei, the inclusion of pasta phases can delay the transition to uniform matter and enlarge the region of nonuniform matter in the phase diagram. The thermodynamic quantities obtained in the present calculation with the CLD model are consistent with those in the realistic equation of state table for astrophysical simulations using the Thomas--Fermi approximation. It is found that the density ranges of various pasta shapes depend on both the temperature $T$ and the proton fraction $Y_{p}$ . Furthermore, the nuclear symmetry energy and its density dependence may play crucial roles in determining the properties of pasta phases. Our results suggest that the pasta phase diagram is most sensitively dependent on the symmetry energy slope $L$ especially in the low- $Y_{p}$ and high- $T$ region.
↳ astro-ph.HEastro-ph.SRnucl-thPRC(2020)·12 citations
08
Crystals of superconducting Baryonic tubes in the low energy limit of QCD at finite density
Fabrizio Canfora🇨🇱 · Marcela Lagos🇨🇱 · Aldo Vera🇨🇱
The low energy limit of QCD admits (crystals of) superconducting Baryonic tubes at finite density. We begin with the Maxwell-gauged Skyrme model in (3+1)-dimensions (which is the low energy limit of QCD in the leading order of the large N expansion). We construct an ansatz able to reduce the seven coupled field equations in a sector of high Baryonic charge to just one linear Schrodinger-like equation with an effective potential (which can be computed explicitly) periodic in the two spatial directions orthogonal to the axis of the tubes. The solutions represent ordered arrays of Baryonic superconducting tubes as (most of) the Baryonic charge and total energy is concentrated in the tube-shaped regions. They carry a persistent current (which vanishes outside the tubes) even in the limit of vanishing U(1) gauge field: such a current cannot be deformed continuously to zero as it is tied to the topological charge. Then, we discuss the subleading corrections in the 't Hooft expansion to the Skyrme model (called usually \mathcal{L}_{6} $,$ \mathcal{L}_{8}$ and so on). Remarkably, the very same ansatz allows to construct analytically these crystals of superconducting Baryonic tubes at any order in the 't Hooft expansion. Thus, no matter how many subleading terms are included, these ordered arrays of gauged solitons are described by the same ansatz and keep their main properties manifesting a universal character. On the other hand, the subleading terms can affect the stability properties of the configurations setting lower bounds on the allowed Baryon density.
↳ hep-thastro-ph.HEgr-qchep-ph+1EPJC(2020)·41 citations

Affiliations

first authorsco-authorsvia INSPIRE