Light mass window of lepton portal dark matter

We explore a novel possibility that dark matter has a light mass below 1 GeV in a lepton portal dark matter model. There are Yukawa couplings involving dark matter, left-handed leptons and an extra scalar doublet in the model. In the light mass region, dark matter is thermally produced via its annihilation into neutrinos. In order to obtain the correct relic abundance and avoid collider bounds, a neutral scalar is required to be light while charged scalars need to be heavier than the electroweak scale. Such a mass spectrum is realized by adjusting quartic couplings in the scalar potential or introducing an extra singlet scalar. It turns out that the mass region of 10 MeV-10 GeV is almost free from experimental and observational constraints. We also point out that searches for extra neutrino flux from galactic dark matter annihilations with neutrino telescopes are the best way to test our model.

Automated summary

The model explores the possibility of dark matter having a mass below 1 GeV, involving Yukawa couplings between dark matter, left-handed leptons, and an extra scalar doublet. In order to avoid collider constraints, adjustments in quartic couplings in the scalar potential or the introduction of an extra singlet scalar are necessary.