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Nuclear Theory·nucl-th

Friday·November 9, 2018

3 papers—1 primary·2 cross-listed

All3Primary1Cross-lists2
  1. 01

    [Submitted on 7 Nov 2018]

    Recent developments for the optical model of nuclei

    Willem H. Dickhoff · Robert J. Charity

    A brief overview of various approaches to the optical-model description of nuclei is presented. A survey of some of the formal aspects is given which links the Feshbach formulation for either the hole or particle Green's function to the time-ordered quantity of many-body theory. The link between the reducible self-energy and the elastic nucleon-nucleus scattering amplitude is also presented using the development of Villars. A brief summary of the essential elements of the multiple-scattering approach is also included. Several ingredients contained in the time-ordered Green's function are summarized for the formal framework of the dispersive optical model (DOM). Empirical approaches to the optical potential are reviewed with emphasis on the latest global parametrizations for nucleons and composites. Various calculations that start from an underlying realistic nucleon-nucleon interaction are discussed with emphasis on more recent work. The efficacy of the DOM is illustrated in relating nuclear structure and nuclear reaction information. Its use as an intermediate between experimental data and theoretical calculations is advocated. Applications of the use of optical models are pointed out in the context of the description of nuclear reactions other than elastic nucleon-nucleus scattering.

    Comments:
    74 pages, 28 figures, review article accepted for publication in Prog. Part. Nucl. Phys
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1811.03111 [pdf]
    PPNP(2019)·81 citations
  2. 02

    [Submitted on 7 Nov 2018] (cross-list from hep-ph)

    Dark Side of the Neutron?

    Bartosz Fornal🇺🇸 · Benjamin Grinstein🇺🇸

    We discuss our recently proposed interpretation of the discrepancy between the bottle and beam neutron lifetime experiments as a sign of a dark sector. The difference between the outcomes of the two types of measurements is explained by the existence of a neutron dark decay channel with a branching fraction 1%. Phenomenologically consistent particle physics models for the neutron dark decay can be constructed and they involve a strongly self-interacting dark sector. We elaborate on the theoretical developments around this idea and describe the efforts undertaken to verify it experimentally.

    Comments:
    6 pages, 2 figures; Plenary talk presented at the International Workshop on Particle Physics at Neutron Sources 2018, Grenoble, France, May 24-26, 2018; based on: Phys. Rev. Lett. 120, 191801 (2018) [arXiv:1801.01124]; see also arXiv:1810.00862; to be published in EPJ Web of Conferences
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1811.03086 [pdf]
    EPJ Web Conf.(2019)·7 citations
  3. 03

    [Submitted on 8 Nov 2018] (cross-list from hep-ph)

    Lepton angular distributions of fixed-target Drell-Yan experiments in perturbative QCD and a geometric approach

    Wen-Chen Chang🇹🇼 · Randall Evan McClellan🇺🇸 · Jen-Chieh Peng🇺🇸 · Oleg Teryaev🇷🇺

    The lepton angular distributions of the Drell-Yan process in fixed-target experiments are investigated by NLO and NNLO perturbative QCD. We present the calculated angular parameters , , and the degree of violation of the Lam-Tung relation, , for the NA10, E615 and E866 experiments. Predictions for the ongoing COMPASS and SeaQuest experiments are also presented. The transverse momentum () distributions of and show a clear dependence on the dimuon mass () while those of have a strong rapidity () dependence. Furthermore, and are found to scale with . These salient features could be qualitatively understood by a geometric approach where the lepton angular distribution parameters are expressed in terms of the polar and azimuthal angles of the "natural axis" in the dilepton rest frame.

    Comments:
    published version, two-column format, 10 pages, 14 figures
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1811.03256 [pdf]
    PRD(2019)·19 citations

Affiliations

first authorsco-authorsvia INSPIRE