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Nuclear Theory·nucl-th

Thursday·November 11, 2021

7 papers—3 primary·4 cross-listed

All7Primary3Cross-lists4
  1. 01

    [Submitted on 9 Nov 2021]

    How perturbative QCD constrains the Equation of State at Neutron-Star densities

    Oleg Komoltsev🇳🇴 · Aleksi Kurkela🇳🇴

    We demonstrate in a general and analytic way how high-density information about the equation of state (EoS) of strongly interacting matter obtained using perturbative Quantum Chromodynamics (pQCD) constrains the same EoS at densities reachable in physical neutron stars. Our approach is based on utilizing the full information of the thermodynamic potentials at the high-density limit together with thermodynamic stability and causality. This requires considering the pressure as a function of chemical potential instead of the commonly used pressure as a function of energy density . The results can be used to propagate the pQCD calculations reliable around 40 to lower densities in the most conservative way possible. We constrain the EoS starting from only few times the nuclear saturation density and at we exclude at least 65% of otherwise allowed area in the -plane. This provides information complementary to astrophysical observations that should be taken into account in any complete statistical inference study of the EoS. These purely theoretical results are independent of astrophysical neutron-star input, and hence, they can also be used to test theories of modified gravity and BSM physics in neutron stars.

    Comments:
    v2: the version published in PRL. A comparison of publicly available EoSs with new constraints added to the appendix C
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2111.05350 [pdf]
    PRL(2022)·234 citations
  2. 02

    [Submitted on 10 Nov 2021]

    Calculations of the alpha decay half-lives of some Polonium isotopes using the double folding model

    W. A. Yahya · K. J. Oyewumi

    The calculations of the alpha decay half-lives of some Polonium isotopes in the mass range 186 - 218 have been carried out using the Wentzel-Kramers-Brillouin (WKB) semiclassical approximation. The alpha-nucleus effective potential used contains the Coulomb potential, centrifugal potential, and the nuclear potential. The nuclear potential is obtained via the double folding model, with the microscopic NN effective interactions derived from relativistic mean field theory Lagrangian (termed R3Y). Different parametrizations of the R3Y interactions have been employed in the computation of the nuclear potentials. The results obtained using the R3Y NN interactions are compared with the ones obtained using the famous Michigan-3-Yukawa (M3Y) interactions. The use of density-dependent NN interaction is also considered. When compared to available experimental data, there are improvements in the results when density-dependent interaction potentials are used compared to when density-independent interactions are employed.

    Comments:
    17 pages
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2111.05604 [pdf]
    Acta Phys.Polon.B(2021)·7 citations
  3. 03

    [Submitted on 10 Nov 2021]

    Density dependence of symmetry energy and neutron skin thickness revisited using relativistic mean field models with nonlinear couplings

    Chiranjib Mondal🇫🇷

    The correlation between neutron skin-thickness of a neutron-rich nucleus and slope parameter of symmetry energy is assessed as a function of density using relativistic mean field models containing non-linear couplings among different mesons. Models with larger skin were found to probe the slope parameter even at suprasaturation densities, whereas models with smaller skin were observed to be sensitive only at specific subsaturation density, connected to the average density of nuclei. Possible reasons behind this density dependence are explored systematically. These results might be model specific, which need to be reassessed in other type of interactions existing in the literature. Nevertheless, extrapolating the predictions at high densities from models, which are optimized by data at saturation or subsaturation densities, needs to be handled with care.

    Comments:
    6 figures, 7 pages
    Subjects:
    Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Experiment (nucl-ex)
    arXiv:
    2111.05743 [pdf]
    PRC(2022)·6 citations
  4. 04

    [Submitted on 9 Nov 2021] (cross-list from hep-ph)

    Testing Lepton Flavor Universality with Pion, Kaon, Tau, and Beta Decays

    Douglas Bryman🇨🇦 · Vincenzo Cirigliano🇺🇸 · Andreas Crivellin🇨🇭 · Gianluca Inguglia🇦🇹

    We present an overview of searches fo violation of lepton flavor universality with focus on low energy precision probes using pions, kaons, tau leptons, and nuclear beta decays. The current experimental results are reviewed, the theoretical status within the context of the Standard Model is summarized, and future prospects (both experimental and theoretical) are discussed. We review the implications of these measurements for physics beyond the Standard Model by performing a global model-independent fit to modified couplings to leptons and four-fermion operators. We also discuss new physics in the context of simplified models and review Standard Model extensions with focus on those which can explain a possible deviation from unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

    Comments:
    33 pages, 2 figures, invited contribution to "Annual Review of Nuclear and Particle Science"
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2111.05338 [pdf]
    Ann.Rev.Nucl.Part.Sci.(2022)·71 citations
  5. 05

    [Submitted on 9 Nov 2021] (cross-list from hep-lat)

    Infinite volume, three-body scattering formalisms in the presence of bound states

    Sebastian M. Dawid🇺🇸

    Strong interactions produce a rich spectrum of resonances that decay into three or more hadrons. Understanding their phenomenology requires a theoretical framework to extract parameters fromexperimental data and Lattice QCD simulations of hadron scattering. Two classes of relativistic three-body approaches are currently being pursued: the EFT-based and unitarity-based one. We consider a model of relativistic three-body scattering with an S-wave bound state in the two-body sub-channel using both formalisms. We present and discuss numerical solutions for the multi-hadron scattering amplitudes in different kinematical regions, obtained from integral equationsof the EFT-based approach. The connection of our work to the ongoing program of computingthe three-body spectrum from the lattice is highlighted. Finally, we show how to generalizethe unitarity-based framework to include all relevant open channels, discuss the nonphysicalsingularities near the physical region, and show how to eliminate them in a simple case.

    Comments:
    13 pages, 5 figures, Talk at the 38th International Symposium on Lattice Field Theory, LATTICE2021, 26th-30th July, 2021, Zoom/Gather@Massachusetts Institute of Technology
    Subjects:
    High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
    arXiv:
    2111.05418 [pdf]
    PoS(2022)·5 citations
  6. 06

    [Submitted on 10 Nov 2021] (cross-list from astro-ph.HE)

    Modeling general-relativistic plasmas with collisionless moments and dissipative two-fluid magnetohydrodynamics

    Elias R. Most · Jorge Noronha · Alexander A. Philippov

    Relativistic plasmas are central to the study of black hole accretion, jet physics, neutron star mergers, and compact object magnetospheres. Despite the need to accurately capture the dynamics of these plasmas and the implications for relativistic transients, their fluid modeling is typically done using a number of (overly) simplifying assumptions, which do not hold in general. This is especially true when the mean free path in the plasma is large compared to the system size, and kinetic effects start to become important. Going beyond common approaches used in the literature, we describe a fully relativistic covariant 14-moment based two-fluid system appropriate for the study of electron-ion or electron-positron plasmas. This generalized Israel-Stewart-like system of equations of motion is obtained directly from the relativistic Boltzmann-Vlasov equation. Crucially, this new formulation can account for non-ideal effects, such as anisotropic pressures and heat fluxes. We show that a relativistic two-fluid plasma can be recast as a single fluid coupled to electromagnetic fields with (potentially large) out-of-equilibrium corrections. In particular, we keep all electron degrees of freedom, which provide self-consistent evolution equations for electron temperature and momentum. The equations outlined in this paper are able to capture the full two-fluid character of collisionless plasmas found in black hole accretion and flaring processes around compact objects, as well Braginskii-like two-fluid magnetohydrodynamics applicable to weakly collisional plasmas inside accretion disks. This new formulation will be instrumental in the construction of a large class of next-generation simulations of relativistic transient phenomena produced around black holes and neutron stars.

    Comments:
    15 pages, version accepted by MNRAS
    Subjects:
    High Energy Astrophysical Phenomena (astro-ph.HE); General Relativity and Quantum Cosmology (gr-qc); Nuclear Theory (nucl-th)
    arXiv:
    2111.05752 [pdf]
    MNRAS(2022)·42 citations
  7. 07

    [Submitted on 10 Nov 2021] (cross-list from hep-ph)

    Light scalars in neutron star mergers

    P. S. Bhupal Dev🇺🇸 · Jean-François Fortin🇨🇦 · Steven P. Harris🇺🇸 · Kuver Sinha🇺🇸 · Yongchao Zhang🇨🇳

    Due to their unique set of multimessenger signals, neutron star mergers have emerged as a novel environment for studies of new physics beyond the Standard Model (SM). As a case study, we consider the simplest extension of the SM scalar sector involving a light CP-even scalar singlet mixing with the SM Higgs boson. These particles can be produced abundantly in neutron star mergers via the nucleon bremsstrahlung process. We show that the particles may either be trapped in or stream freely out of the merger remnant, depending on the mass, its mixing with the SM Higgs boson, and the temperature and baryon density in the merger. In the free-streaming region, the scalar will provide an extra channel to cool down the merger remnant, with cooling timescales as small as (ms). On the other hand, in the trapped region, the Bose gas of particles could contribute a larger thermal conductivity than the trapped neutrinos in some parts of the parameter space, thus leading to faster thermal equilibration than expected. Therefore, future observations of the early postmerger phase of a neutron star merger could effectively probe a unique range of the parameter space, largely complementary to the existing and future laboratory and supernova limits. In view of these results, we hope the merger simulation community will be motivated to implement the effects of light CP-even scalars into their simulations in both the free-streaming and trapped regimes.

    Comments:
    44 pages, 10 figures v2: Matches version to be published in JCAP. Added a discussion of the Boltzmann suppression of the emissivity (fig 5) that occurs for scalar particles with m_S >> T. Added some material on the role of pions
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Astrophysical Phenomena (astro-ph.HE); Nuclear Theory (nucl-th)
    arXiv:
    2111.05852 [pdf]
    JCAP(2022)·18 citations

Affiliations

first authorsco-authorsvia INSPIRE