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Nuclear Theory·nucl-th

Wednesday·April 21, 2021

4 papers—2 primary·2 cross-listed

All4Primary2Cross-lists2
  1. 01

    Chiral extrapolation of the charged-pion magnetic polarizability with Padé approximant

    Fangcheng He🇨🇳 · D. B. Leinweber🇦🇺 · A. W. Thomas🇦🇺 · P. Wang🇨🇳

    The background magnetic-field formalism of Lattice QCD has been used recently to calculate the magnetic polarizability of the charged pion. These numerical simulations are electro-quenched, such that the virtual sea-quarks of the QCD vacuum do not interact with the background field. To understand the impact of this, we draw on partially quenched chiral perturbation theory. In this case, the leading term proportional to arises at tree level from . To describe the results from lattice QCD, while maintaining the exact leading terms of chiral perturbation theory, we introduce a Padé approximant designed to reproduce the slow variation observed in the lattice QCD results. Two-loop contributions are introduced to assess the systematic uncertainty associated with higher-order terms of the expansion. Upon extrapolation, the magnetic polarizability of the charged pion at the physical pion mass is found to be fm, in good agreement with the recent experimental measurement.

    nucl-thhep-latPRD(2021)·9 citations
  3. 03

    Ab Initio Coupling of Jets to Collective Flow in the Opacity Expansion Approach

    Andrey V. Sadofyev🇪🇸 · Matthew D. Sievert🇺🇸 · Ivan Vitev🇺🇸

    We calculate the leading corrections to jet momentum broadening and medium-induced branching that arise from the velocity of the moving medium at first order in opacity. These results advance our knowledge of jet quenching and demonstrate how it couples to collective flow of the quark-gluon plasma in heavy-ion collisions and to the orbital motion of partons in cold nuclear matter in deep inelastic scattering at the electron-ion collider. We also compute the leading corrections to jet momentum broadening due to transverse gradients of temperature and density. We find that these effects lead to both anisotropic transverse momentum diffusion proportional to the medium velocity and anisotropic medium-induced radiation emitted preferentially in the direction of the flow. We isolate the relevant sub-eikonal corrections by working with jets composed of scalar particles with arbitrary color factors interacting with the medium by scalar QCD. Appropriate substitution of the color factors and light-front wave functions allow us to immediately apply the results to a range of processes including branching in real QCD. The resulting general expressions can be directly coupled to hydrodynamic simulations on an event-by-event basis to study the correlations between jet quenching and the dynamics of various forms of nuclear matter.

    ↳ hep-phnucl-thPRD(2021)·90 citations
  4. 04

    Electrostatic energy of Coulomb crystals with polarized electron background

    A. A. Kozhberov🇷🇺 · A. Y. Potekhin🇷🇺

    Outer crusts of neutron stars and interiors of cool white dwarfs consist of bare atomic nuclei, arranged in a crystal lattice and immersed in a Fermi gas of degenerate electrons. We study electrostatic properties of such Coulomb crystals, taking into account the polarizability of the electron gas and considering different lattice structures, which can form the ground state. To take the electron background polarization into account, we use the linear response theory with the electron dielectric function given either by the Thomas-Fermi approximation or by the random-phase approximation (RPA). We compare the widely used nonrelativistic (Lindhard) version of the RPA approximation with the more general, relativistic (Jancovici) version. The results of the different approximations are compared to assess the importance of going beyond the Thomas-Fermi or Lindhard approximations. We also include contribution of zero-point vibrations of ions into the ground-state energy. We show that the bcc lattice forms the ground state for any charge number of the atomic nuclei at the densities where the electrons are relativistic ( g cm), while at lower densities the fcc and hcp lattices can form the ground state. The MgB-like lattice never forms the ground state at realistic densities in the crystallized regions of degenerate stars. The RPA corrections strongly affect the boundaries between the phases. As a result, transitions between different ground-state structures depend on in a nontrivial way. The relativistic and quantum corrections produce less dramatic effects, moderately shifting the phase boundaries.

    ↳ physics.plasm-phastro-ph.SRnucl-thPRE(2021)·9 citations

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first authorsco-authorsvia INSPIRE