Dark matter decay through gravity portals

TL;DR

This paper explores how dark matter particles can decay via gravity portals, analyzing various models and constraints, and finds that certain candidates are viable within specific mass ranges, highlighting the importance of additional stabilizing symmetries.

Contribution

It provides a detailed study of dark matter decay through gravity portals across different models, identifying constraints and natural protections against rapid decay.

Findings

Scalar singlet dark matter is strongly constrained, requiring additional stabilization.

Scalar doublet and fermionic singlet are naturally protected against fast decay.

Viable dark matter masses are up to ~10^5 GeV for scalar doublet and ~10^6 GeV for fermionic singlet.

Abstract

Motivated by the fact that, so far, the whole body of evidence for dark matter is of gravitational origin, we study the decays of dark matter into Standard Model particles mediated by gravity portals, i.e., through nonminimal gravitational interactions of dark matter. We investigate the decays in several widely studied frameworks of scalar and fermionic dark matter where the dark matter is stabilized in flat spacetime via global symmetries. We find that the constraints on the scalar singlet dark matter candidate are remarkably strong and exclude large regions of the parameter space, suggesting that an additional stabilizing symmetry should be in place. In contrast, the scalar doublet and the fermionic singlet candidates are naturally protected against too fast decays by gauge and Lorentz symmetry, respectively. For a nonminimal coupling parameter $\xi\sim {\cal{O}}(1)$, decays through the gravity portal are consistent with observations if the dark matter mass is smaller than $\sim 10^5$ GeV, for the scalar doublet, and $\sim 10^6$ GeV, for the fermionic singlet.