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Nuclear Theory·nucl-th

Monday·August 5, 2024

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 01

    New insight into the N/Z and mass equilibration in heavy-ion collisions

    Yu Yang · Zehong Liao · Zepeng Gao · Long Zhu · Jun Su · Cheng Li

    The dynamics of N/Z and mass equilibration are investigated in the reactions 112,124Sn + 239Pu by employing the isospin-dependent quantum molecular dynamics model. It is found that N/Z and mass equilibration take place at different collision stages. The N/Z relaxation is observed in the approaching phase (from first contact to deepest contact) with a very short time, whereas interestingly we find for the first time that mass equilibration only takes place in the separation phase (from the deepest contact to re-separation), which are explained by investigating the dynamical asymmetry between the approaching and separation phases. The mass equilibration also could be clarified with a dynamical potential energy surface. Our results provide a new insight into the equilibration dynamics of the quantum systems.

    nucl-thPRC(2025)·3 citations
  2. 02

    Thermodynamics of the parity-doublet model: Asymmetric and neutron matter

    Jürgen Eser🇩🇪 · Jean-Paul Blaizot🇫🇷

    We consider isospin-asymmetric matter in the parity-doublet model within an extended mean-field calculation, increasing continuously the neutron excess all the way to pure neutron matter. We compute the liquid-gas and the chiral phase transitions occurring at zero to moderate temperatures, but put special emphasis on the phase structure of matter at zero temperature and large baryon densities. The calculation of the free energy involves the solution of gap equations. This is achieved by transforming these gap equations into ordinary differential equations that control the flow with increasing baryon density of various physical quantities: the isoscalar condensate, the densities of protons and neutrons, as well as those of their respective chiral partners. In this formulation, the initial conditions for the differential equations determine the entire phase structure. It is further demonstrated that the threshold for the onset of the population of the chiral partners is exclusively determined by the fermionic parameters, most notably by the chiral-invariant mass of the nucleon. We underline the role of a parity symmetry energy in driving the equilibration of the nucleons and their parity partners across the chiral transition. We provide a detailed analysis of the changes in the matter properties as one varies the neutron excess, including a special discussion of the chiral limit, and we compare systematically the parity-doublet model to its corresponding singlet model, where the chiral partner of the nucleon is neglected. Finally, we focus on neutron matter and compute the equation of state and the speed of sound. The results are confronted to those of other calculations as well as to recent Bayesian analyses of neutron-star observations.

    nucl-thhep-phPRC(2024)·9 citations
  3. 03

    Cluster production and the chemical freeze-out in expanding hot dense matter

    D. Blaschke🇵🇱 · S. Liebing🇩🇪 · G. Röpke🇵🇱 · B. Dönigus🇩🇪

    We discuss medium effects on light cluster production in the QCD phase diagram by relating Mott transition lines to those for chemical freeze-out. In heavy-ion collisions at highest energies provided by the LHC, light cluster abundances should follow the statistical model because of low baryon densities. Chemical freeze-out in this domain is correlated with the QCD crossover transition. At low energies, in the nuclear fragmentation region, where the freeze-out interferes with the liquid-gas phase transition, self-energy and Pauli blocking effects are important. We demonstrate that at intermediate energies the chemical freeze-out line correlates with the maximum mass fraction of nuclear bound states, in particular particles. In this domain, the HADES, FAIR and NICA experiments can give new insights.

    nucl-thhep-phPLB(2025)·13 citations
  4. 04

    Impact of dark energy on the structure of neutron stars: The vacuum case

    L. F. Araujo🇧🇷 · J. A. S. Lima🇧🇷 · G. Lugones🇧🇷

    The potential role of a cosmic vacuum dark component in the properties of neutron stars is investigated. It is assumed that the static, spherically symmetric distribution of matter within neutron stars is supported by two distinct components: ordinary matter and a vacuum fluid. For normal matter we use a set of state-of-the-art nuclear matter equations of state, each grounded in nuclear physics experiments. The vacuum energy component is inhomogeneously distributed within the star and obeys the standard equation of state (). This is characterized by an energy density fraction , which we model as either a constant or radius-dependent. Our findings reveal that the inclusion of vacuum energy significantly affects the mass-radius relationships in neutron stars, influencing both the maximum achievable masses and the qualitative form of these relationships. Some constraints from current multimessenger observational data limiting the amount of vacuum energy within neutron stars are also discussed.

    ↳ hep-phastro-ph.HEastro-ph.SRgr-qc+1PRD(2024)·6 citations
  5. 05

    Pole analysis for the - coupled-channel system

    Pan-Pan Shi🇪🇸 · F. Gil-Domínguez🇪🇸 · R. Molina🇪🇸 · Meng-Lin Du🇨🇳

    By solving the Lippmann-Schwinger equation, possible hadronic molecules in the - coupled-channel system are investigated with the one-meson exchange potentials, where both vector and pseudoscalar mesons are considered as exchange particles. We find an S-wave virtual state with mass MeV, and a resonance with and width MeV. In the invariant mass distribution, the virtual state appears as a cusp at the threshold, while the resonance potentially manifests as a dip. In particular, we take into account the three-body dynamics due to the on-shell pion exchange and the finite decay width for .

    ↳ hep-phhep-exnucl-thPLB(2025)·5 citations
  6. 06

    Hyperons during proto-neutron star deleptonization and the emission of dark flavoured particles

    Tobias Fischer🇵🇱 · Jorge Martin Camalich🇪🇸 · Hristijan Kochankovski🇪🇸 · Laura Tolos🇪🇸

    Complementary to high-energy experimental efforts, indirect astrophysical searches of particles beyond the standard model have long been pursued. The present article follows the latter approach and considers, for the first time, the self-consistent treatment of the energy losses from dark flavoured particles produced in the decay of hyperons during a core-collapse supernova (CCSN). To this end, general relativistic supernova simulations in spherical symmetry are performed, featuring six-species Boltzmann neutrino transport, and covering the long-term evolution of the nascent remnant proto-neutron star (PNS) deleptonization for several tens of seconds. A well-calibrated hyperon equation of state (EOS) is therefore implemented into the supernova simulations and tested against the corresponding nucleonic model. It is found that supernova observables, such as the neutrino signal, are robustly insensitive to the appearance of hyperons for the simulation times considered in the present study. The presence of hyperons enables an additional channel for the appearance of dark sector particles, which is considered at the level of the hyperon decay. Assuming massless particles that escape the PNS after being produced, these channels expedite the deleptonizing PNS and the cooling behaviour. This, in turn, shortens the neutrino emission timescale. The present study confirms the previously estimated upper limits on the corresponding branching ratios for low and high mass PNS, by effectively reducing the neutrino emission timescale by a factor of two. This is consistent with the classical argument deduced from the neutrino detection associated with SN1987A.

    ↳ astro-ph.HEhep-phnucl-thJCAP(2025)·13 citations

Affiliations

first authorsco-authorsvia INSPIRE