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Nuclear Theory·nucl-th

Monday·May 3, 2021

3 papers—2 primary·1 cross-listed

All3Primary2Cross-lists1
  1. 01

    [Submitted on 30 Apr 2021]

    Neutron-Proton Interaction Modeled using Morse Function: Constructing Inverse Potentials Using Variational Monte-Carlo and Phase Function Method

    Anil Khachi🇮🇳 · Lalit Kumar🇮🇳 · O.S.K.S. Sastri🇮🇳

    Understanding neutron-proton(np) interaction has been one of the most studied problems. One way to construct model interaction has been using inversion potentials obtained from experimental scattering phase shifts(SPS). Here, we show that, inverse potentials corresponding to SPS for various l-channels of np interaction can be obtained using variational Monte-Carlo(VMC) technique in tandem with phase function method(PFM) by modeling np-interaction as a Morse function. The S-channel SPS for 3S1 and 1S0 have been obtained, with a mean percentage error with respect to experimental multiple energy analysis data for lab energies up to 1050 MeV, to less than 5%. Similarly, inverse potential for 1S0 pp interaction, with Coulomb term modeled as proportional to erf(), has also been obtained to match experimental values to less than 4%. Non-local and spin-orbit terms are included to obtain inverse potentials for P and D channels and results match with available data to a good extent.

    Comments:
    12 pages, 3 figures, 1 Table
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2104.14788 [pdf]
    1 citation
  2. 02

    [Submitted on 30 Apr 2021]

    Normal-ordering approximations and translational (non) invariance

    T. Djärv🇸🇪 · A. Ekström🇸🇪 · C. Forssén🇸🇪 · G. R. Jansen🇺🇸

    Normal-ordering provides an approach to approximate three-body forces as effective two-body operators and it is therefore an important tool in many-body calculations with realistic nuclear interactions. The corresponding neglect of certain three-body terms in the normal-ordered Hamiltonian is known to influence translational invariance, although the magnitude of this effect has not yet been systematically quantified. In this work we study in particular the normal-ordering two-body approximation applied to a single harmonic-oscillator reference state. We explicate the breaking of translational invariance and demonstrate the magnitude of the approximation error as a function of model space parameters for and by performing full no-core shell-model calculations with and without three-nucleon forces. We combine two different diagnostics to better monitor the breaking of translational invariance. While the center-of-mass effect is shown to become potentially very large for , it is also shown to be much smaller for although full convergence is not reached. These tools can be easily implemented in studies using other many-body frameworks and bases.

    Comments:
    13 pages, 10 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    2104.14820 [pdf]
    PRC(2021)·12 citations
  3. 03

    [Submitted on 30 Apr 2021] (cross-list from nucl-ex)

    Centrality dependence of electroweak boson production in PbPb collisions at the LHC

    Florian Jonas (Münster Uni.+ORNL)🇩🇪 · Constantin Loizides (ORNL)🇺🇸

    Recent data on the nuclear modification of W and Z boson production measured by the ATLAS collaboration in PbPb collisions at TeV show an enhancement in peripheral collisions, seemingly contradicting predictions of the Glauber model. The data were previously explained by arguing that the nucleon-nucleon cross section may be shadowed in nucleus-nucleus collisions, and hence suppressed compared to the proton-proton cross section at the same collision energy. This interpretation has quite significant consequences for the understanding of heavy-ion data, in particular in the context of the Glauber model. Instead, we provide an alternative explanation of the data by assuming that there is a mild bias present in the centrality determination of the measurement; on the size of the related systematic uncertainty. Using this assumption, we show that the data is in agreement with theoretical calculations using nuclear parton distribution functions. Finally, we speculate that the centrality dependence of the W/W ratio may point to the relevance of a larger skin thickness of the Pb nucleus, which, if present, would result in a few percent larger PbPb cross section than currently accounted for in the Glauber model and may hence be the root of the centrality bias.

    Comments:
    8 pages, 5 figures, 1 table, comments welcome
    Subjects:
    Nuclear Experiment (nucl-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    2104.14903 [pdf]
    PRC(2021)·15 citations

Affiliations

first authorsco-authorsvia INSPIRE