Sommerfeld enhancement from Goldstone pseudo-scalar exchange

TL;DR

This paper explores how Goldstone pseudo-scalar exchange can significantly enhance dark matter annihilation rates, potentially explaining cosmic ray excesses, though it requires fine tuning and involves singular short-distance forces.

Contribution

It introduces a novel mechanism for dark matter annihilation enhancement via Goldstone pseudo-scalar exchange involving tensor forces and discusses similar effects with other singular potentials.

Findings

Goldstone pseudo-scalar exchange can cause significant annihilation enhancement.

Large enhancements require fine tuning of parameters.

Singular short-distance potentials can also produce similar effects.

Abstract

We point out that the exchange of a Goldstone pseudo-scalar can provide an enhancement in the dark matter annihilation rate capable of explaining the excess flux seen in high energy cosmic ray data. The mechanism of enhancement involves the coupling of s and d waves through the tensor force that is very strong and, in fact, singular at short distances. The results indicate that large enhancements require some amount of fine tuning. We also discuss the enhancement due to other singular attractive potentials, such as WIMP models with a permanent electric dipole.