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.

↳ hep-phnucl-exnucl-thEPJ Web Conf.(2019)·7 citations

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.

↳ hep-phhep-exnucl-exnucl-thPRD(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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