Abstract
We scrutinize the XENON1T electron recoil excess in the scalar-singlet-extended dark matter effective field theory. We confront it with various astrophysical and laboratory constraints both in a general setup and in the more specific, recently proposed, variant with leptophilic $Z_2$-odd mediators. The latter also provide mass to the light leptons via suppressed $Z_2$ breaking, a structure that is well fitting with the nature of the observed excess and the discrete symmetry leads to non-standard dark-matter interactions. We find that the excess can be explained by neutrino--electron interactions, linked with the neutrino and electron masses, while dark-matter--electron scattering does not lead to statistically significant improvement. We analyze the parameter space preferred by the anomaly and find severe constraints that can only be avoided in certain corners of parameter space. Potentially problematic bounds on electron couplings from Big-Bang Nucleosynthesis can be circumvented via a late phase transition in the new scalar sector.
Highlights
AND SETUPRecently, the XENON1T collaboration reported new results from an analysis of low-energy electronic recoil data [1]
We consider the leptophilic variant of the extended DM EFT (eDMEFT) recently put forward in [38], which corresponds to the Standard Model (SM) field content augmented with a fermionic dark matter (DM) singlet χ and a real, CP even scalar mediator S, with the assumption that S and the right-handed first lepton generation are odd under a Z2 parity
We have investigated the excess in low energy electron recoil events reported by the XENON1T collaboration
Summary
The XENON1T collaboration reported new results from an analysis of low-energy electronic recoil data [1]. We characterize the XENON1T excess in an effective field theory (EFT) description of a dark sector, recently proposed in [38], which naturally includes the appropriate ingredients for its explanation, namely modified neutrino interactions with electrons via a potentially light new scalar sector, coupling most prominently to the light fermion generations. In the variant employed here, a spontaneously broken Z2 symmetry is included, that on the one hand leads to interesting DM signatures [38], and on the other allows to address the smallness of first-generation fermion masses via small symmetry-breaking effects, as detailed below. Induces nontrivial couplings of the new scalar with these fermions and thereby allows to relate the XENON1T excess with the observed electron and neutrino masses.
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