Speaker
Description
As with the standard grand unification, we may have a similar structure in the dark sector. The dark-sector counterpart of baryons plays a role of the dark matter at the low-energy scale when the particle-antiparticle asymmetries are shared in the Standard Model and dark sectors. Through the portal interaction sharing asymmetry, dark matter particles can decay into antineutrinos and dark-sector counterparts of mesons (dark mesons) or dark photon. Subsequent cascade decay of the dark mesons and the dark photon can also provide electromagnetic fluxes at late times of the Universe. We perform comprehensive studies on the DM decay by combining the astrophysical constraints from electron, positron, and gamma-ray. The characteristic DM mass in the range of 1 — 10 GeV requires the precise analysis for the cosmic-ray constraints. We derive constraints on the lifetime of dark matter decay in the composite ADM scenario from the astrophysical observations of the cosmic-ray fluxes. The constraints from cosmic-ray positron measurements by AMS-02 are the most stringent above 2 GeV: a lifetime should be larger than the order of 10^{26} s, corresponding to the cutoff scale of the portal interaction of about 10^8 — 10^9 GeV. We also perform the precise analysis for the neutrino monoenergetic signals at Super-Kamiokande and Hyper-Kamiokande due to the atmospheric neutrino background in the energy range of our interest.
