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Nuclear Theory·nucl-th

Thursday·October 4, 2018

6 papers—3 primary·3 cross-listed

All6Primary3Cross-lists3
  1. 04

    [Submitted on 1 Oct 2018] (cross-list from hep-ph)

    Neutron Lifetime Discrepancy as a Sign of a Dark Sector?

    Bartosz Fornal🇺🇸 · Benjamin Grinstein🇺🇸

    We summarize our recent proposal of explaining the discrepancy between the bottle and beam measurements of the neutron lifetime through the existence of a dark sector, which the neutron can decay to with a branching fraction 1%. We show that viable particle physics models for such neutron dark decays can be constructed and we briefly comment on recent developments in this area.

    Comments:
    Talk presented at CIPANP2018. 8 pages, 2 figures; based on: Phys. Rev. Lett. 120, 191801 (2018) [arXiv:1801.01124]; v2: references added
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
    arXiv:
    1810.00862 [pdf]
    5 citations
  2. 05

    [Submitted on 3 Oct 2018] (cross-list from hep-lat)

    Simulating the weak death of the neutron in a femtoscale universe with near-Exascale computing

    Evan Berkowitz🇩🇪 · M.A. Clark🇺🇸 · Arjun Gambhir🇺🇸 · Ken McElvain🇺🇸 · Amy Nicholson🇺🇸 · Enrico Rinaldi🇺🇸 · Pavlos Vranas🇺🇸 · André Walker-Loud🇺🇸 · Chia Cheng Chang🇺🇸 · Bálint Joó🇺🇸 · Thorsten Kurth🇺🇸 · Kostas Orginos🇺🇸

    The fundamental particle theory called Quantum Chromodynamics (QCD) dictates everything about protons and neutrons, from their intrinsic properties to interactions that bind them into atomic nuclei. Quantities that cannot be fully resolved through experiment, such as the neutron lifetime (whose precise value is important for the existence of light-atomic elements that make the sun shine and life possible), may be understood through numerical solutions to QCD. We directly solve QCD using Lattice Gauge Theory and calculate nuclear observables such as neutron lifetime. We have developed an improved algorithm that exponentially decreases the time-to solution and applied it on the new CORAL supercomputers, Sierra and Summit. We use run-time autotuning to distribute GPU resources, achieving 20% performance at low node count. We also developed optimal application mapping through a job manager, which allows CPU and GPU jobs to be interleaved, yielding 15% of peak performance when deployed across large fractions of CORAL.

    Comments:
    2018 Gordon Bell Finalist: 9 pages, 9 figures; v2: fixed 2 typos and appended acknowledgements
    Subjects:
    High Energy Physics — Lattice (hep-lat); cs.DC (cs.DC); Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
    arXiv:
    1810.01609 [pdf]
    Supercomputing 2018, pp. 697-705·11 citations
  3. 06

    [Submitted on 3 Oct 2018] (cross-list from hep-ph)

    The pole structure of low energy scattering amplitudes

    Yu-Fei Wang🇨🇳

    This report presents an investigation of the pion-nucleon elastic scattering in low energy region using a production representation of the partial wave matrix. The phase shifts are separated into contributions from poles and branch cuts, where the left-hand cut term can be evaluated by tree-level covariant baryon chiral perturbation theory. A comparison between the sum of known contributions and the data in - and - wave channels is made. It is found that the known components in and channels are far from enough to saturate the corresponding experimental data, indicating the existence of low-lying hidden poles. The positions of those hidden poles are figured out and the physics behind them are explored.

    Comments:
    5 pages. Conference proceeding of 15th International Workshop on Meson Physics, Cracow, Poland, 7th-12th June 2018
    Subjects:
    High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
    arXiv:
    1810.01667 [pdf]
    EPJ Web Conf.(2019)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE