Discriminating WIMP-nucleus response functions in present and future XENON-like direct detection experiments

TL;DR

This paper investigates how different WIMP-nucleus response functions can be distinguished in current and future direct detection experiments by analyzing their momentum transfer dependence, aiding in understanding dark matter interactions.

Contribution

It demonstrates that future large-scale experiments like DARWIN can effectively differentiate various WIMP-nucleus response functions based on their form factors.

Findings

DARWIN can discriminate multiple response functions based on q-dependence.

Current experiments have limited ability to distinguish response functions.

Understanding response functions helps elucidate dark matter interaction mechanisms.

Abstract

The standard interpretation of direct-detection limits on dark matter involves particular assumptions of the underlying WIMP-nucleus interaction, such as, in the simplest case, the choice of a Helm form factor that phenomenologically describes an isoscalar spin-independent interaction. In general, the interaction of dark matter with the target nuclei may well proceed via different mechanisms, which would lead to a different shape of the corresponding nuclear structure factors as a function of the momentum transfer $q$. We study to what extent different WIMP-nucleus responses can be differentiated based on the $q$-dependence of their structure factors (or "form factors"). We assume an overall strength of the interaction consistent with present spin-independent limits and consider an exposure corresponding to XENON1T-like, XENONnT-like, and DARWIN-like direct detection experiments. We find that, as long as the interaction strength does not lie too much below current limits, the DARWIN settings allow a conclusive discrimination of many different response functions based on their $q$-dependence, with immediate consequences for elucidating the nature of dark matter.