Constraining Sommerfeld Enhanced Annihilation Cross-sections of Dark Matter via Direct Searches

TL;DR

This paper demonstrates that models with Sommerfeld-enhanced dark matter annihilation are constrained by direct detection experiments due to the mixing of a light scalar with the Higgs, limiting the boost factors compatible with observations.

Contribution

It shows that Sommerfeld enhancement models predict observable signals in direct detection experiments, providing new constraints on dark matter annihilation cross-sections.

Findings

Large Sommerfeld boost factors are excluded by current direct detection limits.

The light scalar mediating enhancement mixes with the Higgs, leading to detectable signals.

Constraints rule out boost factors of a few hundred for reasonable model parameters.

Abstract

In a large class of models we show that the light scalar field responsible for the Sommerfeld enhancement in the annihilation of dark matter leads to observable direct detection rates, due to its mixing with the standard model Higgs. As a result the large annihilation cross-section of dark matter at present epoch, required to explain the observed cosmic ray anomalies, can be strongly constrained by direct searches. In particular Sommerfeld boost factors of order of a few hundred are already out of the CDMS-II upper bound at 90% confidence level for reasonable values of the model parameters.