Extended MSSM Neutralinos as the Source of the PAMELA Positron Excess

TL;DR

This paper proposes an extended MSSM model where neutralino dark matter annihilates into light singlet-like Higgs bosons, explaining the PAMELA positron excess through enhanced annihilation rates and decay channels.

Contribution

It introduces a singlet-extended MSSM framework that naturally accounts for the positron excess via new annihilation pathways and Sommerfeld enhancement effects.

Findings

The model fits the PAMELA positron data well.

Singlet-like Higgs bosons enable large Sommerfeld enhancement.

Annihilation rates are sufficient to explain the observed excess.

Abstract

We consider a scenario within the Minimal Supersymmetric Standard Model extended by a singlet chiral superfield, in which neutralino dark matter annihilates to light singlet-like Higgs bosons, which proceed to decay to either electron-positron or muon-antimuon pairs. Unlike neutralino annihilations in the MSSM, this model can provide a good fit to the PAMELA cosmic ray positron fraction excess. Furthermore, the singlet-like scalar Higgs can induce a large Sommerfeld enhancement and provide an annihilation rate sufficient to accommodate the observed positron excess.