Is the PAMELA Positron Excess Winos?

TL;DR

The paper explores whether the PAMELA positron excess can be explained by a 200 GeV wino-like dark matter particle, considering astrophysical uncertainties and future tests to confirm this hypothesis.

Contribution

It proposes a wino-like LSP as a potential explanation for the positron excess and discusses the implications for dark matter cosmology and future observational tests.

Findings

Wino-like LSP can fit PAMELA positron data under certain conditions.

Current astrophysical uncertainties affect the interpretation of anti-proton and gamma-ray data.

Future data from PAMELA and FGST will be crucial for testing this hypothesis.

Abstract

Recently the PAMELA satellite-based experiment reported an excess of galactic positrons that could be a signal of annihilating dark matter. The PAMELA data may admit an interpretation as a signal from a wino-like LSP of mass about 200 GeV, normalized to the local relic density, and annihilating mainly into W-bosons. This possibility requires the current conventional estimate for the energy loss rate of positrons be too large by roughly a factor of five. Data from anti-protons and gamma rays also provide tension with this interpretation, but there are significant astrophysical uncertainties associated with their propagation. It is not unreasonable to take this well-motivated candidate seriously, at present, in part because it can be tested in several ways soon. The forthcoming PAMELA data on higher energy positrons and the FGST (formerly GLAST) data, should provide important clues as to whether this scenario is correct. If correct, the wino interpretation implies a cosmological history in which the dark matter does not originate in thermal equilibrium.