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Nuclear Theory·nucl-th

Monday·August 28, 2023

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 01

    [Submitted on 25 Aug 2023]

    Composite octet baryons in a relativistic mean field description of nuclear and neutron star matter

    Kaito Noro🇯🇵 · Wolfgang Bentz🇯🇵 · Ian C. Cloët🇺🇸 · Teruyuki Kitabayashi🇯🇵

    We examine the properties of composite octet baryons in the nuclear medium and neutron star matter. The internal quark-diquark structure of the octet baryons and the equations of state of nuclear matter and neutron star matter in the mean field approximation are described by using the three-flavor Nambu--Jona-Lasinio (NJL) model as an effective quark theory of QCD. After introducing our model, we first discuss the properties of single baryons and their effective meson exchange interactions in symmetric nuclear matter by using concepts of Fermi liquid theory. Several model independent implications of this description are derived, and illustrated by numerical results obtained in our model. Second, we extend the model description to high baryon densities, and investigate the equation of state of neutron star matter and the resulting star masses. We find that the so called hyperon puzzle persists also for the case of composite hadrons. To get more information on this point, we also investigate the role of 6-fermi and 8-fermi interactions, in addition to the standard 4-fermi interactions. The strengths of those higher order fermi interactions is determined so as not to spoil the saturation properties of nuclear matter. Among them, an interaction characterized by a product of four quark current operators plays a special role to stabilize the stars over a large region of central baryon densities, although it has little effect on the maximum star masses.

    Comments:
    22 pages, 11 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2308.13179 [pdf]
    PRC(2024)·6 citations
  2. 02

    [Submitted on 25 Aug 2023]

    An extension of the generator coordinate method with basis optimization

    Moemi Matsumoto · Yusuke Tanimura · Kouichi Hagino

    The generator coordinate method (GCM) has been a well-known method to describe nuclear collective motions. In this method, one specifies {\it a priori} the relevant collective degrees of freedom as input of the method, based on empirical and/or phenomenological assumptions. We here propose a new extension of the GCM, in which both the basis Slater determinants and weight factors are optimized according to the variational principle. Applying this method to O and Si nuclei with the Skyrme functional, we demonstrate that the optimized bases correspond to excited states along a collective path, unlike the conventional GCM which superposes only the local ground states. This implies that a collective coordinate for large amplitude collective motions is determined in a much more complex way than what has been assumed so far.

    Comments:
    5 pages, 3 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2308.13233 [pdf]
    PRC(2023)·11 citations
  3. 03

    [Submitted on 25 Aug 2023]

    Relativistic constraints on 3N contact interactions

    Alessia Nasoni🇮🇹 · Elena Filandri🇮🇹 · Luca Girlanda🇮🇹

    In this paper we analyze the relativistic corrections to the leading order three-nucleon (3N) contact interactions. These boost corrections are derived first from the nonrelativistic reduction of covariant Lagrangians and later from the Poincaré algebra constraints on nonrelativistic theories. We show that in order to describe the 3N potential in reference frames other than the center-of-mass frame, the inclusion of five additional terms with fixed coefficients is required. These terms will be relevant in systems with mass number A>3. How they will affect EFT calculations of binding energies and scattering observables in these systems should be investigated.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2308.13341 [pdf]
    EPJA(2023)·7 citations
  4. 04

    [Submitted on 25 Aug 2023]

    Coupling between collective modes in the deformed Zr nucleus: Insights from consistent HFB+QRPA calculations with the Gogny interaction

    E. V. Chimanski · E. J. In · S. Péru · A. Thapa · W. Younes · J. E. Escher

    The Zirconium isotopes exhibit structural properties that present multiple challenges to nuclear theory. Investigations of the coupling present within isoscalar modes and within isovector modes are scarce but important for advancing our understanding of the microscopic picture of nuclei. To explore some of these underlying coupling features, and to test the predictive power of a state-of-the-art nuclear structure approach, we provide a detailed analysis of the properties of Zr. This region includes a benchmarking case and offers insights into nuclear deformation phenomena. To investigate the coupling between collective modes in deformed nuclei, we focused our analysis on the ground and excited-state properties of these isotopes, employing a consistent approach with the axially-symmetric deformed Hartree-Fock-Bogoliubov (HFB) and the Quasiparticle Random Phase Approximation (QRPA) framework, both using the Gogny D1M force. This approach effectively describes both low-lying and giant-resonance states. We devoted special attention to the deformed Zr nucleus, where we confirm the existence of coupling between monopole and quadrupole excitations through the QRPA components and demonstrate an analogous dipole-octupole coupling through the and components. Intrinsic transition densities and associated radial projections illustrate the coupling. Our work complements and extends earlier studies carried out using density-functional-based methods and notably, we included the complete Coulomb interaction also in the pairing fields, i.e. we treat terms exactly that are approximated in typical calculations that use the Gogny D1 and D2 interaction families.

    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2308.13374 [pdf]
    PRC(2025)·12 citations
  5. 05

    [Submitted on 24 Aug 2023] (cross-list from hep-ph)

    MeV Sterile Neutrino in light of the Cabibbo-Angle Anomaly

    Teppei Kitahara🇨🇳 · Kohsaku Tobioka🇺🇸

    A modified neutrino sector could imprint a signature on precision measurements of the quark sector because many such measurements rely on the semi-leptonic decays of the charged currents. Currently, global fits of the determinations of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements point to a -level deficit in the first-row CKM unitarity test, commonly referred to as the Cabibbo-angle anomaly. We find that a MeV sterile neutrino that mixes with the electron-type neutrino increases the extracted , accommodating the Cabibbo-angle anomaly. This MeV sterile neutrino affects the superallowed nuclear decays and neutron decay, but it barely modifies the other measurements of the CKM elements. While various constraints may apply to such a sterile neutrino, we present viable scenarios within an extension of the inverse seesaw model.

    Comments:
    11 pages, 3 figures; v2: references added; v3: matches version published in PRD
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Theory (nucl-th)
    arXiv:
    2308.13003 [pdf]
    PRD(2023)·4 citations
  6. 06

    [Submitted on 24 Aug 2023] (cross-list from hep-ph)

    Exclusive QCD Factorization and Single Transverse Polarization Phenomena at High-Energy Colliders

    Zhite Yu🇺🇸

    This Ph.D.~thesis is divided into two distinct parts. The first part focuses on hard exclusive scattering processes in Quantum Chromodynamics (QCD) at high energies, while the second part delves into spin phenomena at the Large Hadron Collider (LHC). Hard exclusive scattering processes play a crucial role in QCD at high energies, providing unique insights into the confined partonic dynamics within hadrons, complementing inclusive processes. Studying these processes within the QCD factorization approach yields the generalized parton distribution (GPD), a nonperturbative parton correlation function that offers a three-dimensional tomographic parton image within a hadron. However, the experimental measurement of these processes poses significant challenges. This thesis will review the factorization formalism for related processes, examine the limitations of some widely used processes, and introduce two novel processes that enhance the sensitivity to GPD, particularly its dependence on the parton momentum fraction . The second part of the thesis centers on spin phenomena, specifically single spin production, at the LHC. Noting that a single transverse polarization can be generated even in an unpolarized collision, this research proposes two new jet substructure observables: one for boosted top quark jets and another for high-energy gluon jets. The observation of these phenomena paves the way for innovative tools in LHC phenomenology, enabling both precision measurements and the search for new physics.

    Comments:
    Ph.D. thesis. 417 pages
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Lattice (hep-lat); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    2308.13080 [pdf]
    5 citations
  7. 07

    [Submitted on 25 Aug 2023] (cross-list from hep-ph)

    Robust features of QCD phase diagram through a Contact Interaction model for quarks: A view from the effective potential

    Aftab Ahmad🇵🇰 · Muhammad Azher🇵🇰 · Alfredo Raya🇲🇽

    Our research delves into the QCD phase diagram in the temperature and quark chemical potential plane. We use a unique confining contact interaction effective model of quark dynamics that maintains the QCD symmetry intact. By embedding the model into a Schwinger-Dyson equations framework, within a Landau gauge rainbow-ladder-like truncation, we derive the gap equation. In order to accurately regulate the said equation, we utilize the Schwinger optimal time regularization scheme. We further derive the effective potential of the model by integrating the gap equation over the dynamical mass, which along with the confining length scale serve as parameters for the chiral and confinement deconfinement phase transitions, respectively. A cross-over transition is observed at low and above a critical value of the temperature , whilst a first order phase transition is found for low at high density. The critical end point is estimated to be located at , which falls within the range of other QCD effective models predictions. MeV is the critical temperature at vanishing . Screening effects of the medium which dilute the strength of the effective coupling are considered by including the vacuum polarization contribution due to quarks at high temperatures into the framework. It locates the critical end point at , which hints for a deeper analysis of screening effects on models of this kind.

    Comments:
    17,13
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2308.13210 [pdf]
    EPJA(2023)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE