XENON1T excess in local $Z_2$ DM models with light dark sector

Abstract

Recently XENON1T Collaboration announced that they observed some excess in the electron recoil energy around a 2-3 keV. We show that this excess can be interpreted as exothermic scattering of excited dark matter on atomic electron through dark photon exchange. We consider DM models with local dark U (1) gauge symmetry that is spontaneously broken into its Z 2 subgroup by Krauss-Wilczek mechanism. In order to explain the XENON1T excess with the correct DM thermal relic density within freeze-out scenario, all the particles in the dark sector should be light enough, namely ∼ O(100) MeV for scalar DM and ∼ O(1 − 10) MeV for fermion DM cases. And even lighter dark Higgs φ plays an important role in the DM relic density calculation: XX † → Z φ for scalar DM (X) and χ χ → φφ for fermion DM (χ) assuming m Z > m χ . Both of them are in the p-wave annihilation, and one can easily evade stringent bounds from Planck data on CMB on the s-wave annihilations, assuming other dangerous s-wave annihilations are kinematically forbidden.

A multi-component SIMP model with $U(1)_X \rightarrow Z_2 \times Z_3$

“…in Refs. [42,76,77]. Furthermore, we investigated four characteristic show-cases for the multi-component dark matter scenario.…”

“…2 See also Refs. [41][42][43] and Refs. [44][45][46][47] for scalar DM models with U (1) dark gauge symmetry broken into Z2 and Z3, respectively.…”

Missing in axion: Where are XENON1T’s big black holes?

“…Note Added: While this work was in preparation, related works on the axion interpretation of the XENON1T excess [18,27] appeared, as did [28] focusing on other possible explanations.…”

Explaining The XENON1T Excess With Light Goldstini Dark Matter

“…Many alternative ideas had been proposed to explain the XENON1T excess, including the non-standard neutrino-electron interactions with light mediators [2][3][4][5][6][7][8][9][10][11][12][13][14], absorption of axion or dark photon theories , the scattering of dark matter candidates with electron [38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56], and the other mechansims [57][58][59][60][61][62][63][64]. We emphasize that explanations from cosmic dark matter with their new features may shed new light on possible new physics beyond the Standard Model(SM), including the low energy supersymmetry(SUSY).…”