Neutralinos in an extension of the minimal supersymmetric standard model as the source of the PAMELA positron excess

We consider a scenario within the minimal supersymmetric standard model (MSSM) extended by a singlet chiral superfield, in which neutralino dark matter annihilates to light singletlike 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 singletlike Higgs bosons can induce a large Sommerfeld enhancement and provide an annihilation rate sufficient to accommodate the observed positron excess.