PAMELA data and leptonically decaying dark matter

TL;DR

This paper analyzes PAMELA cosmic ray data, finding that leptonic dark matter decay models best explain the positron excess, with neutralino decay scenarios fitting the data well.

Contribution

It demonstrates that leptonic final states in dark matter decay models can explain PAMELA positron excess, favoring decaying over annihilating dark matter, and proposes a neutralino decay model consistent with observations.

Findings

Leptonic decay channels fit PAMELA positron data well.

Quark and gauge boson final states are disfavored by the data.

Decaying neutralino dark matter with specific parameters explains the results.

Abstract

Recently PAMELA released their first results on the positron and antiproton ratios. Stimulated by the new data, we studied the cosmic ray propagation models and calculated the secondary positron and antiproton spectra. The low energy positron ratio can be consistent with data in the convection propagation model. Above $\sim 10$ GeV PAMELA data shows a clear excess on the positron ratio. However, the secondary antiproton is roughly consistent with data. The positron excess may be a direct evidence of dark matter annihilation or decay. We compare the positron and anti-proton spectra with data by assuming dark matter annihilates or decays into different final states. The PAMELA data actually excludes quark pairs being the main final states, disfavors gauge boson final states. Only in the case of leptonic final states the positron and anti-proton spectra can be explained simultaneously. We also compare the decaying and annihilating dark matter scenarios to account for the PAMELA results and prefer to the decaying dark matter. Finally we consider a decaying neutralino dark matter model in the frame of supersymmetry with R-parity violation. The PAMELA data is well fitted with neutralino mass $600\sim 2000$ GeV and life time $\sim 10^{26}$ seconds. We also demonstrate that neutralino with mass around 2TeV can fit PAMELA and ATIC data simultaneously.