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Nuclear Theory·nucl-th

Tuesday·February 21, 2023

10 papers—6 primary·4 cross-listed

All10Primary6Cross-lists4
  1. 07

    [Submitted on 17 Feb 2023] (cross-list from hep-ph)

    Light front synchronization and rest frame densities of the proton: Electromagnetic densities

    Adam Freese🇺🇸 · Gerald A. Miller🇺🇸

    We clarify the physical origin and meaning of the two-dimensional relativistic densities of the light front formalism. The densities are shown to originate entirely from the use of light front time instead of instant form time, which physically corresponds to using an alternative synchronization convention. This is shown by using tilted light front coordinates, which consist of light front time and ordinary spatial coordinates, and which are also used to show that the obtained densities describe a system at rest rather than at infinite momentum. These coordinates allow all four components of the electromagnetic current density to be given clear physical meanings. We explicate the formalism for spin-half targets, obtaining charge and current densities of the proton and neutron using empirical form factor parametrizations, as well as up and down quark densities and currents. Angular modulations in the densities of transversely-polarized states are explained as originating from redshifts and blueshifts due to quarks moving in different longitudinal directions.

    Comments:
    26 pages, 7 figures, version accepted for publication
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2302.09171 [pdf]
    PRD(2023)·13 citations
  2. 08

    [Submitted on 17 Feb 2023] (cross-list from hep-lat)

    QCD Thermodynamics and Neutral Pion in a Uniform Magnetic Field: Finite Volume Effects

    Prabal Adhikari🇺🇸 · Brian C. Tiburzi🇺🇸

    We address finite volume effects of lattice QCD calculations in background magnetic fields. Using chiral perturbation theory at next-to-leading order, volume effects are calculated for thermodynamic quantities: the chiral condensate, pressure anisotropy, and magnetization. The neutral pion effective action in a finite volume is additionally derived. For these charge neutral observables, volume and source averaging are shown to capitalize on magnetic periodicity, which is the remnant translational invariance of the finite-volume theory. For a fixed magnetic field strength, certain volume and source averaged quantities are independent of the size of the lattice transverse to the magnetic field. Despite this simplifying feature, finite volume corrections to the magnetic field dependence of the chiral condensate and neutral pion magnetic polarizability can be non-negligible. The pressure anisotropy at fixed magnetic flux, moreover, appears acutely sensitive to the lattice volume.

    Comments:
    17 pages, 5 figures
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2302.09179 [pdf]
    PRD(2023)·16 citations
  3. 09

    [Submitted on 20 Feb 2023] (cross-list from nucl-ex)

    Study of the threshold anomaly in the elastic scattering of d+Au

    T. Giudice · D. Abriola · A. Arazi · E. de Barbará · M.A. Cardona · J. Gómez · D. Hojman · R.M. Id Betan · M.S. Kohen · N. Llaneza · G.V. Martí · B. Paes and 3 other authors

    Measurements of the elastic scattering angular distribution for the d+Au system were carried out covering deuteron incident energies in the range from 5 to 16 MeV, i.e. approximately 50% below and above the Coulomb barrier. A critical interaction distance of = 2.49 fm was determined from these distributions, which is comparable to that of the radioactive halo nucleus He. The experimental angular distributions were systematically analyzed using two alternative models: the semi-microscopic Sao Paulo and the effective Woods-Saxon optical potentials, for which the best-fitting parameters were determined. These potentials, integrated in the vicinity of the sensitivity radius, were calculated for each energy. For both models, the energy dependence of these integrals presented the breakup threshold anomaly around the coulomb barrier, a typical signature of weakly bound nuclei.

    Comments:
    20 pages. 7 figures. 60 References
    Subjects:
    Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2302.09980 [pdf]
    J.Phys.G(2023)·3 citations
  4. 10

    [Submitted on 20 Feb 2023] (cross-list from hep-ph)

    Implementation of Cluster expansion for hot QCD matter

    Niels-Uwe Friedrich Bastian🇵🇱 · Pasi Huovinen🇵🇱 · Elizaveta Nazarova🇷🇺

    We present a cluster expansion EoS model for strongly-interacting matter based on the generalized Beth-Uhlenbeck formalism to describe hadrons as bound clusters of quarks. This formalism can describe both confined and deconfined phases. Our emphasis is on the region of vanishing baryon densities, where numerical solutions available from Lattice QCD predict a smooth crossover transition from hadron to quark matter. Medium effects are taken into account as self energies, which are motivated from both perturbative QCD calculations and phenomenological models. Parameters are tuned to Lattice QCD data and result in a good agreement of the thermodynamics.

    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2302.10117 [pdf]
    NPA(2023)·2 citations

Affiliations

first authorsco-authorsvia INSPIRE