Abstract
We propose a new candidate of GeV scale inelastic dark matter (DM). Our construction has an anomaly-free $U(1)_X^{}$ gauge group with dark photon mediator, and can realize either scalar or fermionic inelastic DM. It is highly predictive and testable. We study the scattering rate of light inelastic DM with electrons in the XENON1T experiment and with nuclei in the XENON1T, CRESST-III, CDEX-1B and DarkSide-50 experiments. We resolve the recent XENON1T anomaly via electron recoil detection. Combining the XENON1T constraints from both electron recoils and nuclear recoils (including Migdal effect), we predict the inelastic DM mass $\lesssim 1.5$GeV. We further analyze the bounds by the DM relic abundance, the lifetime of the heavier DM component, and laboratory constraints, from which we identify the viable parameter space for the future probe. This provides an important benchmark for the theories and experimental tests of GeV scale inelastic DM.
Highlights
Searching for GeV-scale light dark matter (DM) particles is a very challenging task, because the conventional direct detection via DM-nucleon recoil becomes difficult for DM masses ≲5 GeV
We propose a new candidate of GeV-scale inelastic dark matter (DM)
We achieve the desired OðkeVÞ mass splitting of the inelastic DM by a scalar seesaw mechanism without fine-tuning. We show that this minimal model is viable for the inelastic DM of mass ≲1.4 GeV, which can provide the intriguing anomaly in the XENON1T electron recoil spectrum [2] and be consistent with the DMnucleon recoil detections by XENON1T [11], CRESST-III [12], CDEX-1B [13], and DarkSide-50 [14] experiments
Summary
Searching for GeV-scale light dark matter (DM) particles is a very challenging task, because the conventional direct detection via DM-nucleon recoil becomes difficult for DM masses ≲5 GeV. One attractive resolution of the XENON1T anomaly is the exothermic inelastic scattering [7,8] between the DM and electrons In this scenario, the DM consists of two components ðX; X0Þ with a small mass splitting ΔmX ≡ mX0 − mX, which is around the anomalous recoil energy region (2–3) keV of XENON1T. We achieve the desired OðkeVÞ mass splitting of the inelastic DM by a scalar seesaw mechanism without fine-tuning We show that this minimal model is viable for the inelastic DM of mass ≲1.4 GeV, which can provide the intriguing anomaly in the XENON1T electron recoil spectrum [2] and be consistent with the DMnucleon recoil detections (of low threshold) by XENON1T [11], CRESST-III [12], CDEX-1B [13], and DarkSide-50 [14] experiments. Appendix B presents our analysis on the Higgs sector of this model
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