Nuclear scattering of dark matter coupled to a new light scalar

TL;DR

This paper analyzes the nuclear scattering cross section of eXciting Dark Matter (XDM), showing it is suppressed compared to direct Higgs coupling models but can be enhanced in two-Higgs-doublet models, making detection feasible.

Contribution

It provides the first detailed calculation of XDM nuclear scattering cross sections, including suppression factors and potential enhancements in extended Higgs sectors.

Findings

Suppression factor of about 10^(-5) in XDM nuclear scattering cross section.

Standard Model Higgs coupling yields a cross section around 4 x 10^(-13) pb, below current detection sensitivity.

Two-Higgs-doublet models can increase the cross section by up to four orders of magnitude, making detection possible.

Abstract

We consider the nuclear scattering cross section for the eXciting Dark Matter (XDM) model. In XDM, the Weakly Interacting Massive Particles (WIMPs) couple to the Standard Model only via an intermediate light scalar which mixes with the Higgs: this leads to a suppression in the nuclear scattering cross section relative to models in which the WIMPs couple to the Higgs directly. We estimate this suppression factor to be of order 10^(-5). The elastic nuclear scattering cross section for XDM can also be computed directly: we perform this computation for XDM coupled to the Higgs sector of the Standard Model and find a spin-independent cross section in the order of 4 x 10^(-13) pb in the decoupling limit, which is not within the range of any near-term direct detection experiments. However, if the XDM dark sector is instead coupled to a two-Higgs-doublet model, the spin-independent nuclear scattering cross section can be enhanced by up to four orders of magnitude for large tan(beta), which should be observable in the upcoming SuperCDMS and ton-scale xenon experiments.