Sterile neutrino dark matter within the $\nu$SMEFT

TL;DR

This paper explores how the $ u$SMEFT framework allows sterile neutrino dark matter to evade X-ray constraints through higher dimensional operators, expanding viable parameter space and offering new experimental test avenues.

Contribution

It demonstrates that $ u$SMEFT operators can produce sterile neutrino dark matter and suppress X-ray signals, broadening the viable parameter space beyond minimal models.

Findings

Higher dimensional operators can suppress X-ray emission from sterile neutrino decay.

Sterile neutrino DM density can be explained even with zero mixing due to $ u$SMEFT.

Potential experimental signatures include electric dipole moments and neutrinoless double beta decay.

Abstract

Sterile neutrinos with masses at the $\mathrm{keV}$ scale and mixing to the active neutrinos offer an elegant explanation of the observed dark matter (DM) density. However, the very same mixing inevitably leads to radiative photon emission and the non-observation of such peaked $X$-ray lines rules out this minimal sterile neutrino DM hypothesis. We show that in the context of the Standard Model effective field theory with sterile neutrinos ($\nu$SMEFT), higher dimensional operators can produce sterile neutrino DM in a broad range of parameter space. In particular, $\nu$SMEFT interactions can open the large mixing parameter space due to their destructive interference, through operator mixing or matching, in the $X$-ray emission. We also find that, even in the zero mixing limit, the DM density can always be explained by $\nu$SMEFT operators. The testability of the studied $\nu$SMEFT operators in searches for electric dipole moments, neutrinoless double beta decay, and pion decay measurements is discussed.