Closing in on mass-degenerate dark matter scenarios with antiprotons and direct detection

TL;DR

This study combines cosmic-ray antiproton and direct detection data to constrain mass-degenerate dark matter models, finding that direct detection currently provides the strongest limits and that future collider searches could further explore these scenarios.

Contribution

It provides the first comprehensive analysis of antiproton and direct detection constraints on degenerate dark matter models with a Majorana fermion and scalar mediator, considering astrophysical and nuclear uncertainties.

Findings

Direct detection limits surpass antiproton constraints in degenerate scenarios.

Lower limits on mass splitting reach 19% at 300 GeV dark matter mass.

Constraints are complementary to collider searches, enabling future exploration.

Abstract

Over the last years both cosmic-ray antiproton measurements and direct dark matter searches have proved particularly effective in constraining the nature of dark matter candidates. The present work focusses on these two types of constraints in a minimal framework which features a Majorana fermion as the dark matter particle and a scalar that mediates the coupling to quarks. Considering a wide range of coupling schemes, we derive antiproton and direct detection constraints using the latest data and paying close attention to astrophysical and nuclear uncertainties. Both signals are strongly enhanced in the presence of degenerate dark matter and scalar masses, but we show that the effect is especially dramatic in direct detection. Accordingly, the latest direct detection limits take the lead over antiprotons. We find that antiproton and direct detection data set stringent lower limits on the mass splitting, reaching 19% at a 300 GeV dark matter mass for a unity coupling. Interestingly, these limits are orthogonal to ongoing collider searches at the Large Hadron Collider, making it feasible to close in on degenerate dark matter scenarios within the next years.