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Nuclear Theory·nucl-th

Monday·January 2, 2023

12 papers—6 primary·6 cross-listed

All12Primary6Cross-lists6
  1. 01

    Properties of Pb predicted from the relativistic equation of state in the full Dirac space

    Hui Tong · Jing Gao · Chencan Wang · Sibo Wang

    Relativistic Brueckner-Hartree-Fock (RBHF) theory in the full Dirac space allows one to determine uniquely the momentum dependence of scalar and vector components of the single-particle potentials. In order to extend this new method from nuclear matter to finite nuclei, as a first step, properties of Pb are explored by using the microscopic equation of state for asymmetric nuclear matter and a liquid droplet model. The neutron and proton density distributions, the binding energies, the neutron and proton radii, and the neutron skin thickness in Pb are calculated. In order to further compare the charge densities predicted from the RBHF theory in the full Dirac space with the experimental charge densities, the differential cross sections and the electric charge form factors in the elastic electron-nucleus scattering are obtained by using the phase-shift analysis method. The results from the RBHF theory are in good agreement with the experimental data. In addition, the uncertainty arising from variations of the surface term parameter in the liquid droplet model is also discussed.

    nucl-thPRC(2023)·8 citations
  2. 02

    Ridge regression for minimizing the couplings of hyperon resonances in the photoproduction

    Dimitrios Petrellis🇨🇿 · Dalibor Skoupil🇨🇿

    We employed the isobar model for investigating the photoproduction process. We paid special attention to the recent CLAS polarization data and enhanced the minimization by adding a penalty term. Without changing the set of included resonances used by the model, this technique known as Ridge regression leads to reduced couplings that in previous studies acquired unreasonably large values. As a result, we have arrived at a much more robust model with hyperon couplings which are reduced to more physical values. This model serves us to extract valuable information on the background to the photoproduction and particularly on the role of various hyperon resonances. The set of the nucleon resonances is the same with respect to previous fits but their role may have changed due to different couplings which they acquire in the present fit.

    nucl-thPRC(2023)·9 citations
  3. 03

    Charged-particle bound states in periodic boxes

    Hang Yu · Sebastian König · Dean Lee

    We consider the binding energy of a two-body system with a repulsive Coulomb interaction in a finite periodic volume. We define the finite-volume Coulomb potential as the usual Coulomb potential, except that the distance is defined as the shortest separation between the two bodies in the periodic volume. We investigate this problem in one and three-dimensional periodic boxes and derive the asymptotic behavior of the volume dependence for bound states with zero angular momentum in terms of Whittaker functions. We benchmark our results against numerical calculations and show how the method can be used to extract asymptotic normalization coefficients for charged-particle bound states. The results we derive here have immediate applications for calculations of atomic nuclei in finite periodic volumes for the case where the leading finite-volume correction is associated with two charged clusters.

    nucl-thPRL(2023)·10 citations
  4. 04

    Global angular momentum generation in heavy-ion reactions within a hadronic transport approach

    Nils Sass🇩🇪 · Marco Müller🇩🇪 · Oscar Garcia-Montero🇩🇪 · Hannah Elfner🇩🇪

    In 2017, the STAR collaboration at the Relativistic Heavy Ion Collider (RHIC) has measured finite global angular momentum in heavy-ion collisions through a spin polarization measurement of hyperons. This measurement revealed a high angular momentum of the heavy ions and provided experimental evidence for vorticity in the quark-gluon plasma (QGP) for the first time. In order to investigate the underlying mechanisms, a dynamic description of the transfer of angular momentum is required. In this work, the microscopic non-equilibrium transport approach SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) is applied to study the generation of global angular momentum by the interaction of two nuclei. As SMASH provides access to the whole phase-space evolution of every particle at any given time, it allows to assess the fraction of angular momentum generated in the fireball by all participants. We confirm the previous modeling by Becattini \textit{et al} within a geometric Glauber model approach, which found that the angular momentum transfer reaches a unique maximum in mid-central collisions during time evolution. The corresponding impact parameter is around fm for all beam energies from GeV. Even though angular momentum is not conserved locally in the transport approach a priori, we identify the contributions to the conservation violation and propose optimal setups for different energy regimes that recover conservation, based upon the test particle method and the treatment of Fermi motion. Furthermore, the system size and centrality dependence are investigated.

    nucl-thhep-phPRC(2023)·15 citations
  5. 05

    Relativistic approach to the nuclear breathing mode

    Elena Litvinova

    Microscopic theory of the nuclear response based on the relativistic meson-nucleon Lagrangian is applied to the description of the isoscalar giant monopole resonance (ISGMR) in a variety of nuclear systems. It is shown that the parameter-free inclusion of beyond-mean-field correlations of the quasiparticle-vibration coupling (qPVC) type in the leading approximation allows for a simultaneous realistic description of the ISGMR in nuclei of lead, tin, zirconium, and nickel mass regions, which is difficult on the mean-field level. The calculations employ the finite-range effective meson-nucleon interaction, which, in combination with the qPVC, has consistently demonstrated the ability to reliably describe many other nuclear structure phenomena. Systematic calculations of the isoscalar monopole response for nickel isotopes help reveal the central role of the coupling between the ISGMR and the low-energy quadrupole states in the placement of the ISGMR centroids.

    nucl-thastro-ph.SRnucl-exPRC(2023)·27 citations
  6. 06

    Effect of color superconductivity on the mass of hybrid neutron stars in an effective model with pQCD asymptotics

    David Blaschke🇵🇱 · Udita Shukla🇵🇱 · Oleksii Ivanytskyi🇵🇱 · Simon Liebing🇩🇪

    The effective cold quark matter model by Alford, Braby, Paris and Reddy (ABPR) is used as a tool for discussing the effect of the size of the pairing gap in three-flavor (CFL) quark matter on the maximum mass of hybrid neutron stars (NSs). This equation of state (EOS) has three parameters which we suggest to determine by comparison with a nonlocal NJL model of quark matter in the nonperturbative domain. We show that due to the momentum dependence of the pairing which is induced by the nonlocality of the interaction, the effective gap parameter in the EOS model is well approximated by a constant value depending on the diquark coupling strength in the NJL model Lagrangian. For the parameter a constant value below about \num{0.4} is needed to explain hybrid stars with , which would translate to an effective constant . The matching point with a running coupling at the 1-loop function level is found to lie outside the range of chemical potentials accessible in NS interiors. A dictionary is provided for translating the free parameters of the nlNJL model to those of the ABPR model. Both models are shown to be equivalent in the nonperturbative domain but the latter one allows to quantify the transition to the asymptotic behaviour in accordance with perturbative QCD. We provide constraints on parameter sets that fulfill the mass constraint for hybrid NSs, as well as the low tidal deformability constraint from GW170817 by a softening of the EOS on the hybrid NS branch with an early onset of deconfinement at . We find that the effective constant pairing gap should be around 100 MeV but not exceed values of about 130 MeV because a further increase of the gap would entail a softening of the EOS and contradict the mass constraint.

    nucl-thastro-ph.HEhep-phPRD(2023)·27 citations

Affiliations

first authorsco-authorsvia INSPIRE