Cosmic Rays from Leptophilic Dark Matter Decay via Kinetic Mixing

TL;DR

This paper explores a dark matter decay model involving hidden-sector gauginos interacting via kinetic mixing, explaining cosmic ray positron excesses while suppressing antiproton production and discussing potential gamma-ray signatures.

Contribution

It introduces a novel decay mechanism for mixed dark matter involving hidden-sector gauginos and analyzes its implications for cosmic ray observations.

Findings

Decay of hidden gauginos can explain positron excesses

Antiproton production is naturally suppressed in this model

Potential gamma-ray signatures at Fermi are discussed

Abstract

If interpreted in terms of decaying dark matter, the steep rise in the positron fraction of cosmic rays above 10 GeV, as observed by the PAMELA experiment, suggests an underlying production mechanism that favors leptonic channels. We consider a scenario where a portion of the dark matter is made of the gauginos of an unbroken hidden-sector U(1), which interact with the visible sector only through a tiny kinetic mixing. The second component of the dark matter is made of neutralinos, and depending on the mass spectrum, the lightest neutralino or the hidden gaugino becomes unstable and subject to decay. We analyze the cosmic rays, namely the contributions to the positron, the extragalactic gamma-ray and the antiproton flux, which potentially result from these decays and demonstrate that the production of antiprotons can be naturally suppressed. Furthermore, we briefly discuss the apparent double-peak structure of the ATIC data in light of cascade-decaying hidden gauginos, as well as possible signatures at Fermi.