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Nuclear Theory·nucl-th

Monday·November 1, 2021

8 papers—5 primary·3 cross-listed

All8Primary5Cross-lists3
  1. 01

    [Submitted on 29 Oct 2021]

    Removing center of mass effects in response function and sum rule calculations based on the harmonic oscillator basis

    K. Akdogan · D. Layh · I. Weinberger · J. Simonis · N. Barnea · S. Bacca

    Response functions are at the heart of any comparison of theory with experiment in studies of the nuclear dynamics with electroweak probes. Calculations performed in the laboratory frame often suffer from center of mass contaminations that need to be removed. By confining the system in a harmonic oscillator, we derive a set of analytical formulas to subtract the center of mass effects from calculations of response functions and associated sum rules. After a general analytical derivation, we first deal specifically with the longitudinal response function appearing in electron scattering and provide expressions for the center of mass correcting functions. Next, we present a proof of principle study for the case of the electric dipole sum rules in a two-body problem with a numerical implementation of our formalism. These steps pave the way to applying the proposed method to heavier nuclei in the future.

    Comments:
    14 pages, 4 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2110.15594 [pdf]
    PRC(2022)·0 citations
  2. 02

    [Submitted on 29 Oct 2021]

    Anomalous spin polarization from turbulent color fields

    Berndt Müller🇺🇸 · Di-Lun Yang🇹🇼

    We study the important, yet widely overlooked, role of gluons for spin transport with a connection to local parity violation in quark gluon plasmas. We employ the formalism of quantum kinetic theory to quarks in weakly coupled quantum chromodynamics to derive the source terms for quark spin polarization. These source terms involve parity-odd correlators of dynamically generated color fields in near-equilibrium quark gluon plasmas and give rise to locally fluctuating axial charge currents. Our results provide a possible explanation for the spin alignment of vector mesons measured in high-energy nuclear collisions.

    Comments:
    7 pages, 1 figure, corrected version post Erratum
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Theory (hep-th)
    arXiv:
    2110.15630 [pdf]
    PRD(2022)·74 citations
  3. 03

    [Submitted on 29 Oct 2021]

    Multi-reference many-body perturbation theory for nuclei I -- Novel PGCM-PT formalism

    Mikael Frosini🇫🇷 · Thomas Duguet🇫🇷 · Jean-Paul Ebran🇫🇷 · Vittorio Somà🇫🇷

    Perturbative and non-perturbative expansion methods already constitute a tool of choice to perform ab initio calculations over a significant part of the nuclear chart. In this context, the categories of accessible nuclei directly reflect the class of unperturbed state employed in the formulation of the expansion. The present work generalizes to the nuclear many-body context the versatile method of Ref. \cite{burton20a} by formulating a perturbative expansion on top of a multi-reference unperturbed state mixing deformed non-orthogonal Bogoliubov vacua, i.e. a state obtained from the projected generator coordinate method (PGCM). Particular attention is paid to the part of the mixing taking care of the symmetry restoration, showing that it can be exactly contracted throughout the expansion, thus reducing significantly the dimensionality of the linear problem to be solved to extract perturbative corrections. While the novel expansion method, coined as PGCM-PT, reduces to the PGCM at lowest order, it reduces to single-reference perturbation theories in appropriate limits. Based on a PGCM unperturbed state capturing (strong) static correlations in a versatile and efficient fashion, PGCM-PT is indistinctly applicable to doubly closed-shell, singly open-shell and doubly open-shell nuclei. The remaining (weak) dynamical correlations are brought consistently through perturbative corrections. This symmetry-conserving multi-reference perturbation theory is state-specific and applies to both ground and excited PGCM unperturbed states, thus correcting each state belonging to the low-lying spectrum of the system under study.

    Comments:
    The present paper is the first in a series of three and discusses the PGCM-PT formalism in detail. The second paper displays numerical zeroth-order results, i.e. the outcome of PGCM calculations. Second-order, i.e. PGCM-PT(2), calculations performed in both closed- and open-shell nuclei are the object of the third paper
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2110.15737 [pdf]
    EPJA(2022)·73 citations
  4. 04

    [Submitted on 29 Oct 2021]

    Bayesian reconstruction of nuclear matter parameters from the equation of state of neutron star matter

    Sk Md Adil Imam🇮🇳 · N. K. Patra🇮🇳 · C. Mondal🇫🇷 · Tuhin Malik🇵🇹 · B. K. Agrawal🇮🇳

    The nuclear matter parameters (NMPs), those underlie in the construction of the equation of state (EoS) of neutron star matter, are not directly accessible. The Bayesian approach is applied to reconstruct the posterior distributions of NMPs from the EoS of neutron star matter. The constraints on lower-order parameters as imposed by the finite nuclei observables are incorporated through appropriately chosen prior distributions. The calculations are performed with two sets of pseudo data on the EoS whose true models are known. The median values of second or higher order NMPs show sizeable deviations from their true values and associated uncertainties are also larger. The sources of these uncertainties are intrinsic in nature, identified as (i) the correlations among various NMPs and (ii) the variations in the EoS of symmetric nuclear matter, symmetry energy, and the neutron-proton asymmetry in such a way that the neutron star matter EoS remain almost unaffected.

    Comments:
    11 pages, 7 figures, Published in PRC
    Subjects:
    Nuclear Theory (nucl-th); Instrumentation and Methods for Astrophysics (astro-ph.IM); Computational Physics (physics.comp-ph)
    arXiv:
    2110.15776 [pdf]
    PRC(2022)·39 citations
  5. 05

    [Submitted on 29 Oct 2021]

    Large- constraints for elastic dark matter-light nucleus scattering in pionless effective field theory

    Thomas R. Richardson🇺🇸 · Xincheng Lin🇺🇸 · Son T. Nguyen🇺🇸

    Recent proposals for the use of light nuclei as dark matter direct detection targets necessitate a strong theoretical understanding of the nuclear physics involved. We perform relevant calculations for dark matter-light nucleus scattering in a combined pionless effective field theory and large- expansion, where is the number of quark colors. We include a general set of one-nucleon currents that have been used in other effective theories, as well as novel two-nucleon contact currents. First, we obtain constraints for the relative sizes of the dark matter couplings to the one- and two-nucleon currents through the large- expansion. Then, we use these constraints to make predictions for the relative sizes of spin-dependent and spin-independent cross sections for dark matter scattering off of a nucleon, a deuteron, a triton, and helium-3.

    Comments:
    27 pages, 9 figures, version accepted for publication in Physical Review C, substantial revisions and additions compared to version 1
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    2110.15959 [pdf]
    PRC(2022)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE