A Brief Review on Dark Matter Annihilation Explanation for $e^\pm$ Excesses in Cosmic Ray

TL;DR

This paper reviews how dark matter annihilation could explain the observed excesses of electrons and positrons in cosmic rays, discussing mechanisms like Sommerfeld and Breit-Wigner enhancements and their implications for particle physics models.

Contribution

It provides a comprehensive overview of dark matter annihilation explanations for cosmic ray excesses, focusing on enhancement mechanisms and their theoretical implications.

Findings

Large boost factors are needed to match observed excesses.

Sommerfeld and Breit-Wigner mechanisms can provide these boost factors.

Implications for particle physics models are discussed.

Abstract

Recently data from PAMELA, ATIC, FERMI-LAT and HESS show that there are $e^{\pm}$ excesses in the cosmic ray energy spectrum. PAMELA observed excesses only in $e^+$, but not in anti-proton spectrum. ATIC, FERMI-LAT and HESS observed excesses in $e^++e^-$ spectrum, but the detailed shapes are different which requires future experimental observations to pin down the correct data set. Nevertheless a lot of efforts have been made to explain the observed $e^\pm$ excesses, and also why PAMELA only observed excesses in $e^+$ but not in anti-proton. In this brief review we discuss one of the most popular mechanisms to explain the data, the dark matter annihilation. It has long been known that about 23% of our universe is made of relic dark matter. If the relic dark matter was thermally produced, the annihilation rate is constrained resulting in the need of a large boost factor to explain the data. We will discuss in detail how a large boost factor can be obtained by the Sommerfeld and Briet-Wigner enhancement mechanisms. Some implications for particle physics model buildings will also be discussed.