nucl-th digest · Nov 9, 2018

Dark Side of the Neutron?

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

[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 $λ$ , $μ$ , $ν$ and the degree of violation of the Lam-Tung relation, $1 - λ - 2 ν$ , for the NA10, E615 and E866 experiments. Predictions for the ongoing COMPASS and SeaQuest experiments are also presented. The transverse momentum ( $q_{T}$ ) distributions of $λ$ and $ν$ show a clear dependence on the dimuon mass ( $Q$ ) while those of $μ$ have a strong rapidity ( $x_{F}$ ) dependence. Furthermore, $λ$ and $ν$ are found to scale with $q_{T} / Q$ . 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

Friday·November 9, 2018

Dark Side of the Neutron?

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

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