New Thermal-Relic Targets for sub-GeV Dark Matter Direct Detection

TL;DR

This paper establishes new, robust detection targets for sub-GeV dark matter models involving light vector mediators, linking cosmological relic abundance with experimental electron recoil searches.

Contribution

It introduces comprehensive thermal-relic milestones for sub-GeV dark matter coupled to anomaly-free U(1) vector mediators, providing a complete predictive framework.

Findings

Defines new detection targets for sub-GeV dark matter

Connects cosmological relic abundance with experimental signals

Offers a complete list of minimal anomaly-free U(1) models

Abstract

Dark matter direct detection experiments involving electron recoils are beginning to test highly-predictive, thermal-relic milestones for sub-GeV dark matter models. Due to the Lee-Weinberg bound, thermal dark matter candidates in this mass range necessarily require comparably-light mediator particles to achieve a suitably large annihilation cross section. Here we present new thermal-relic milestones for sub-GeV dark matter candidates that couple to vector mediators. In these models, the mediators are massive gauge bosons of anomaly-free abelian extensions to the Standard Model, including the dark photon, gauged $L_i - L_j, B-L$, and $B-3L_i$ models, where $B$ is the baryon number, $L$ is the lepton number, and $i,j$ index the lepton families. Since the same interactions that govern cosmological production also govern electron scattering, the targets we present are firmly predictive and allow for these models to be robustly discovered or falsified. Furthermore, since the mediators we study exhaust the minimal anomaly-free U(1) extensions to the Standard Model, our results offer a complete list of predictive milestones for sub-GeV dark matter coupled to vector mediators.