Inelastic dark matter, small scale problems, and the XENON1T excess

초록

We study a generic model in which the dark sector is composed of a Majorana dark matter chi(1), its excited state chi(2), both at the electroweak scale, and a light dark photon Z ' with m(z ') similar to 10(-4) eV. The light Z ' enhances the self-scattering elastic cross section chi(1)chi(1) -> chi(1)chi(1) enough to solve the small scale problems in the N-body simulations with the cold dark matter. The dark matter communicates with the SM via kinetic mixing parameterized by epsilon. The inelastic scattering process chi(1)chi(1) -> chi(2)chi(2) followed by the prompt decay chi(2) -> chi(1)Z ' generates energetic Z '. By setting delta equivalent to m(chi 2)- m(chi 1) similar or equal to 2.8 keV and epsilon similar to 10(-10) the excess in the electron-recoil data at the XENON1T experiment can be explained by the dark-photoelectric effect. The relic abundance of the dark matter can also be accommodated by the thermal freeze-out mechanism via the annihilation chi(1)chi(1)(chi(2)chi(2)) -> Z ' Z ' with the dark gauge coupling constant alpha(X) similar to 10(-3).

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