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Nuclear Theory·nucl-th

Thursday·November 7, 2024

12 papers—7 primary·5 cross-listed

All12Primary7Cross-lists5
  1. 01

    [Submitted on 5 Nov 2024]

    Assessing the impact of uniform rotation on the structure of neutron stars

    Marc Salinas · Jorge Piekarewicz

    Driven by recent laboratory experiments and astronomical observations, significant advances have deepened our understanding of neutron-star physics. NICER's Pulse Profile Modeling has refined our knowledge of neutron star masses and radii, while gravitational-wave detections have revealed key insights into the structure of neutron stars. Particularly relevant is the extraction of the tidal deformability by the LIGO-Virgo collaboration and the most recent determination of stellar radii by NICER, both suggesting a relatively soft equation of state (EOS) at intermediate densities. Additionally, measurements from the PREX collaboration and from pulsar timing suggest instead that the EOS is stiff in the vicinity of saturation density and at the highest densities accessible to date. But how stiff can the EOS be at these very high densities? Recent events featuring compact objects near the "lower mass gap" have raised questions about the existence of very massive neutron stars. Motivated by this finding and in light of new refinements to theoretical models, we explore the possibility that these massive objects may indeed be rapidly rotating neutron stars. We explore how rotation affects both the maximum neutron star mass and their associated radii, and discuss the implications they may have on the equation of state.

    Comments:
    8 pages and 3 figures. Submitted to Physical Review C
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Experiment (nucl-ex)
    arXiv:
    2411.03490 [pdf]
    PRC(2025)·3 citations
  2. 02

    [Submitted on 5 Nov 2024]

    A pathway to unveiling neutrinoless decay nuclear matrix elements via decay

    Beatriz Romeo🇺🇸 · Damiano Stramaccioni🇮🇹 · Javier Menéndez🇪🇸 · Jose Javier Valiente-Dobón🇮🇹

    We investigate the experimental feasibility of detecting second-order double-magnetic dipole (-) decays from double isobaric analog states (DIAS), which have recently been found to be strongly correlated with the nuclear matrix elements of neutrinoless decay. Using the nuclear shell model, we compute theoretical branching ratios for - decays and compare them with other competing processes, such as single- decay and proton emission, which represent the dominant decay channels. We also estimate the potential competition from internal conversion and internal pair creation, which can influence the decay dynamics. Additionally, we propose an experimental strategy based on using LaBr scintillators to identify - transitions from the DIAS amidst the background of the competing processes. Our approach emphasizes the challenges of isolating the rare - decay and suggests ways to enhance the experimental detection sensitivity. Our simulations suggest that it may be possible to access experimentally - decays from DIAS, shedding light on the neutrinoless decay nuclear matrix elements.

    Comments:
    8 pages, 4 figures, 5 tables
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
    arXiv:
    2411.03539 [pdf]
    PLB(2025)·4 citations
  3. 03

    [Submitted on 5 Nov 2024]

    Non-Equilibrium Aspects of Fission Dynamics within the Time Dependent Density Functional Theory

    A. Bulgac · M. Kafker · I. Abdurrahman · I. Stetcu

    We will cover briefly the time-dependent density functional theory approach, extended to include pairing correlations, to induced fission of U(n,f), Pu, and Np, and also results on scission neutrons and a number of very nontrivial aspects of induced fission.

    Comments:
    5 pages, 1 figure (3 subfigures), invited talk given at The 7th International Workshop on Compound Nuclear Reactions and Related Topics (CNR2024), Vienna, Austria, 8-12 July, 2024
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2411.03546 [pdf]
    EPJ Web Conf.(2025)·1 citation
  4. 04

    [Submitted on 6 Nov 2024]

    Triple- reaction rates below by a non-adiabatic three-body model

    M. Katsuma

    The triple- reaction from the ternary continuum states at off-resonant energies, C, remains an open question. This direct process is scrutinized using a non-adiabatic Faddeev hyperspherical harmonics -matrix expansion method, and the derived reaction rates are discussed. After reviewing the model, the resultant photo-disintegration of C() is shown to be much smaller than the values predicted by the adiabatic models for MeV. Despite the large difference, the derived reaction rates are illustrated to be concordant with the current evaluated rates for . The difference below MeV can be seen in the rates for . In comparison with the calculations, the rates are found to be reduced by a factor of 10 at , because of an accurate description for Be break-up. Uncertainties of the rates are also estimated by examining the sensitivity to the 3 potentials. By introducing three-body -factors and a resonant term, the present rates are expressed in an analytic form, and they are provided in a tabular form for astrophysical applications. To update the evaluated rates, non-resonant sequential process between Be could be removed. The astrophysical impact is not expected to be large, although the rates are reduced around .

    Comments:
    37 pages, 13 figures and 6 tables
    Subjects:
    Nuclear Theory (nucl-th); Solar and Stellar Astrophysics (astro-ph.SR)
    arXiv:
    2411.03600 [pdf]
    J.Phys.G(2025)·0 citations
  5. 05

    [Submitted on 6 Nov 2024]

    RHIC GeV hadron yields and the isospin dependent equation of state

    Feyisola Nana · Jordi Salinas San Martín · Jacquelyn Noronha-Hostler

    The statistical hadronization model has been successful in extracting information at chemical freeze-out in heavy-ion collisions. At RHIC, with a collision energy of GeV, many different ion species have been used for + collisions. This allows for a scan across the charge fraction , where is the proton number and is the baryon number. We first make predictions for + collisions that do not yet have published experimental data on hadron yield ratios (O+O, Ru+Ru, Zr+Zr). We then use both the experimental and predicted yield ratios to perform thermal fits across , enabling us to extract and other thermodynamic information at chemical freeze-out. Using the relation between and , we can calculate a new constraint on the finite temperature equation of state at finite densities. We discuss implications of this constraint and propose future runs that can help connect to the equation of state relevant for neutron star mergers.

    Comments:
    9 pages, 6 figures, 4 tables
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2411.03705 [pdf]
    3 citations
  7. 07

    [Submitted on 6 Nov 2024]

    Hyperon Production in Bi+Bi Collisions at NICA and Angular Dependence of Hyperon Spin Polarization

    Nikita S. Tsegelnik · Vadym Voronyuk · Evgeni E. Kolomeitsev

    The strange baryon production in Bi+Bi collisions at \,GeV is studied using the PHSD transport model. Hyperon and anti-hyperon yields, transverse momentum spectra, and rapidity spectra are calculated, their centrality dependence and the effect of rapidity and transverse momentum cuts are studied. The rapidity distributions for , , baryons are found to be systematically narrower than for s. The slope parameters for anti-hyperons vary more with centrality than those for hyperons. Restricting the accepted rapidity range to increases the slope parameters by 13--30\,MeV depending on the centrality class and the hyperon mass. Hydrodynamic velocity and vorticity fields are calculated and the formation of two oppositely rotating vortex rings moving in opposite directions along the collision axis is found. The hyperon spin polarization induced by the medium vorticity within the thermodynamic approach is calculated and the dependence of the polarization on the transverse momentum and rapidity cuts and on the centrality selection is analyzed. The cuts have stronger effect on the polarization of and hyperons than on the corresponding anti-hyperons. The polarization signal is maximal for the centrality class 60-70\%. We show that for the considered hyperon polarization mechanism the structure of the vorticity field makes an imprint on the polarization signal as a function of the azimuthal angle in the transverse momentum plane, , . For particles with positive longitudinal momentum, , the polarization increases with , while for particles with it decreases.

    Comments:
    19 pages, 14 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2411.03901 [pdf]
    Particles(2024)·5 citations

Affiliations

first authorsco-authorsvia INSPIRE