Direct Detection of Exothermic Dark Matter with Light Mediator

TL;DR

This paper evaluates various dark matter direct detection models involving isospin violation, exothermic scatterings, and light mediators, finding most are now ruled out by recent experimental data, leaving only limited viable scenarios.

Contribution

It provides a comprehensive analysis of the viability of exothermic dark matter models with light mediators in light of recent experimental constraints.

Findings

Many previous models are now excluded by LUX and CDMSlite data.

Xe-phobic exothermic models with light mediators remain partially viable.

Most parameter spaces for these models are constrained by recent experiments.

Abstract

We study the dark matter (DM) direct detection for the models with the effects of the isospin-violating couplings, exothermic scatterings, and/or the lightness of the mediator, proposed to relax the tension between the CDMS-Si signals and null experiments. In the light of the new updates of the LUX and CDMSlite data, we find that many of the previous proposals are now ruled out, including the Ge-phobic exothermic DM model and the Xe-phobic DM one with a light mediator. We also examine the exothermic DM models with a light mediator but without the isospin violation, and we are unable to identify any available parameter space that could simultaneously satisfy all the experiments. The only models that can partially relax the inconsistencies are the Xe-phobic exothermic DM models with or without a light mediator. But even in this case, a large portion of the CDMS-Si regions of interest has been constrained by the LUX and SuperCDMS data.