Constraining the Spin-Independent WIMP-Nucleon Coupling from Direct Dark Matter Detection Data

TL;DR

This paper introduces a model-independent method to estimate the spin-independent WIMP-nucleon coupling from direct detection data, providing a way to constrain dark matter properties despite uncertainties in WIMP velocity distribution and local density.

Contribution

The authors develop a novel, model-independent approach to estimate the SI WIMP-nucleon coupling directly from recoil energy measurements in multiple experiments.

Findings

Upper limits on SI WIMP-nucleon coupling can be set with positive signals from multiple experiments.

For a 100 GeV WIMP, the coupling can be estimated with about 15% error using 50 events per experiment.

The method is robust against uncertainties in WIMP velocity distribution and local density.

Abstract

Weakly Interacting Massive Particles (WIMPs) are one of the leading candidates for Dark Matter. For understanding the properties of WIMPs and identifying them among new particles produced at colliders (hopefully in the near future), determinations of their mass and their couplings on nucleons from direct Dark Matter detection experiments are essential. Based on our method for determining the WIMP mass model-independently from experimental data, we present a way to also estimate the spin-independent (SI) WIMP-nucleon coupling by using measured recoil energies directly. This method isindependent of the as yet unknown velocity distribution of halo WIMPs. In spite of the uncertainty of the local WIMP density (of a factor of ~ 2), at least an upper limit on the SI WIMP-nucleon coupling could be given, once two (or more) experiments with different target nuclei obtain positive signals. In a background-free environment, for a WIMP mass of 100 GeV its SI coupling on nucleons could in principle be estimated with a statistical error of only ~ 15% with just 50 events from each experiment.