Probing inelastic sub-GeV dark matter at the DUNE near detector

TL;DR

This paper investigates the potential of DUNE's near detector to detect inelastic sub-GeV dark matter within a UV-complete model featuring a dark Higgs mechanism, highlighting its sensitivity to new annihilation channels.

Contribution

It introduces a minimal UV-complete inelastic dark matter model with a dark Higgs and assesses DUNE ND-LAr's sensitivity to this scenario, emphasizing its ability to probe relic abundance regions.

Findings

DUNE ND-LAr can detect inelastic dark matter consistent with relic abundance.

Sensitivity is enhanced for large dark photon-to-DM mass ratios.

Results show complementarity between cosmological constraints and fixed-target experiments.

Abstract

We study inelastic dark matter (iDM) in a minimal and ultraviolet-complete framework in which the dark photon mass arises from a dark Higgs mechanism. The spontaneous breaking of a $U(1)_D$ symmetry splits the Dirac fermion into two Majorana states, thus opening new annihilation channels mediated by the dark Higgs. Focusing on sub-GeV dark matter, we assess the sensitivity of DUNE's liquid argon cube at the near detector (ND-LAr) to this scenario. We find that the ND-LAr can probe regions of parameter space consistent with the observed relic abundance due to these new annihilation channels, particularly for large dark photon-to-DM mass ratios where decay-based searches lose sensitivity. Our results highlight the complementarity between cosmological constraints and fixed-target experiments and demonstrate the potential of DUNE's ND-LAr to explore iDM scenarios with extended dark sectors.