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Nuclear Theory·nucl-th

Friday·April 19, 2024

7 papers—4 primary·3 cross-listed

All7Primary4Cross-lists3
  1. 05

    [Submitted on 18 Apr 2024] (cross-list from hep-lat)

    Constraints on the finite volume two-nucleon spectrum at MeV

    William Detmold🇺🇸 · Marc Illa🇺🇸 · William I. Jay🇺🇸 · Assumpta Parreño🇪🇸 · Robert J. Perry🇪🇸 · Phiala E. Shanahan🇺🇸 · Michael L. Wagman🇺🇸

    The low-energy finite-volume spectrum of the two-nucleon system at a quark mass corresponding to a pion mass of MeV is studied with lattice quantum chromodynamics (LQCD) using variational methods. The interpolating-operator sets used in [Phys.Rev.D 107 (2023) 9, 094508] are extended by including a complete basis of local hexaquark operators, as well as plane-wave dibaryon operators built from products of both positive- and negative-parity nucleon operators. Results are presented for the isosinglet and isotriplet two-nucleon channels. In both channels, noticably weaker variational bounds on the lowest few energy eigenvalues are obtained from operator sets which contain only hexaquark operators or operators constructed from the product of two negative-parity nucleons, while other operator sets produce low-energy variational bounds which are consistent within statistical uncertainties. The consequences of these studies for the LQCD understanding of the two-nucleon spectrum are investigated.

    Comments:
    Corrected a relative normalization error in correlation matrix. Updated results, discussion, and conclusions. 46 pages, 19 Figures
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2404.12039 [pdf]
    PRD(2025)·21 citations
  2. 06

    [Submitted on 18 Apr 2024] (cross-list from hep-ph)

    Abnormal solutions of Bethe--Salpeter equation with massless and massive exchanges

    Jaume Carbonell1🇫🇷 · Vladimir Karmanov🇷🇺 · Ekaterina Kupriyanova🇷🇺 · Hagop Sazdjian🇫🇷

    We summarize the main properties of the so called ''abnormal solutions'' of the Wick--Cutkosky model, i.e. two massive scalar particles interacting via massless scalar exchange ("photons"), within the Bethe--Salpeter equation. These solutions do not exist in the non-relativistic limit, in spite of having very small binding energies. They present a genuine many-body character dominated by photons, with a norm of the valence constituent wave function (two-body norm) that vanishes in the limit of zero binding energy. We present new results concerning the massive-exchange case, in particular determine under which conditions is it possible to obtain such peculiar solutions without spoiling the model by tachyonic states ().

    Comments:
    19 pages, 8 figures. Talk given at Workshop Critical Stability, ECT* oct 2023. To appear in Few-Body Systems
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Strongly Correlated Electrons (cond-mat.str-el); Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
    arXiv:
    2404.12182 [pdf]
    Few Body Syst.(2024)·0 citations
  3. 07

    [Submitted on 18 Apr 2024] (cross-list from hep-lat)

    Dirac Spectral Density in N=2+1 QCD at T=230 MeV

    Andrei Alexandru🇺🇸 · Claudio Bonanno🇪🇸 · Massimo D'Elia🇮🇹 · Ivan Horváth🇺🇸

    We compute the renormalized Dirac spectral density in QCD at physical quark masses, temperature MeV and system size fm. To that end, we perform a point-wise continuum limit of the staggered density in lattice QCD with staggered quarks. We find, for the first time, that a clear infrared structure (IR peak) emerges in the density of Dirac operator describing dynamical quarks. We also provide numerical evidence that a component of this peak, which becomes dominant in the thermodynamic limit, is due to a non-trivial accumulation of near-zero modes. Features of this structure are consistent with those previously attributed to the recently-proposed IR phase of thermal QCD. Our results (i) provide the only complete first-principles evidence that these IR features exist and are physical; (ii) improve the upper bound for IR-phase transition temperature so that the new window is MeV; (iii) are consistent with non-restoration of anomalous U(1) symmetry (chiral limit) below MeV.

    Comments:
    7 pages, 6 figures; v2: 8 pages, 7 figures, added results on the topological nature of the peak, other results and conclusions unchanged, version to appear in PRD
    Subjects:
    High Energy Physics — Lattice (hep-lat); High Energy Physics — Theory (hep-th); Nuclear Theory (nucl-th)
    arXiv:
    2404.12298 [pdf]
    PRD(2024)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE