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The 17 MeV anomaly in beryllium decays and U (1) portal to dark matter

2017; World Scientific; Volume: 32; Issue: 31 Linguagem: Inglês

10.1142/s0217751x17501780

1793-656X

Chian-Shu Chen, Guey-Lin Lin, Yen-Hsun Lin, Fanrong Xu,

Cosmology and Gravitation Theories

The experiment of Krasznahorkay et al. observed the transition of a 8 Be excited state to its ground state and accompanied by an emission of an [Formula: see text] pair with 17 MeV invariant mass. This 6.8[Formula: see text] anomaly can be fitted by a new light gauge boson. We consider the new particle as a U(1) gauge boson, [Formula: see text], which plays as a portal linking dark sector and visible sector. In particular, we study the new U(1) gauge symmetry as a hidden or nonhidden group separately. The generic hidden U(1) model, referred to as dark [Formula: see text] model, is excluded by imposing various experimental constraints. On the other hand, a nonhidden [Formula: see text] is allowed due to the additional interactions between [Formula: see text] and Standard Model fermions. We also study the implication of the dark matter direct search on such a scenario. We found that the search for the DM-nucleon scattering cannot probe the parameter space that is allowed by 8 Be-anomaly for the range of DM mass above 500 MeV. However, the DM-electron scattering for DM between 20 MeV and 50 MeV can test the underlying U(1) portal model using the future Si and Ge detectors with the [Formula: see text] threshold charges.