PAMELA Satellite Data as a Signal of Non-Thermal Wino LSP Dark Matter

TL;DR

This paper explores the hypothesis that the PAMELA satellite data can be explained by non-thermal wino dark matter annihilation, providing predictions for future satellite observations and clarifying previous misunderstandings about antiproton signals.

Contribution

It presents a well-motivated theoretical framework linking PAMELA data to non-thermal wino dark matter, with detailed analysis of annihilation products and astrophysical backgrounds.

Findings

Wino annihilation can account for observed antimatter signals below 200 GeV.

PAMELA data does not exclude antiproton signals; previous analyses were misunderstood.

Predicted spectral features include a downturn above 100 GeV in positron and antiproton spectra.

Abstract

Satellite data is accumulating that suggests and constrains dark matter physics. We argue there is a very well motivated theoretical preexisting framework consistent with dark matter annihilation being observed by the PAMELA satellite detector. The dark matter is (mainly) the neutral W boson superpartner, the wino with mass below 200 GeV. Using the program GALPROP we study the annihilation products and backgrounds together. Antimatter and gammas from annihilating winos contribute below this energy. We explain why PAMELA data does not imply no antiproton signal was observed by PAMELA or earlier experiments, and explain why the antiproton analysis was misunderstood by earlier papers. Wino annihilation does not describe the Fermi e+ + e- data (except partially below ~ 100 GeV). At higher energies we expect astrophysical mechanisms, and we simply parameterize them so the combination can describe all the data. We emphasize several predictions for satellite data to test the wino interpretation, particularly the turndown of the positron and antiproton spectra above 100 GeV. Most other interpretations require a large rise in the positron rates above 100 GeV. We focus on studying this well-motivated and long predicted wino interpretation, rather than comparisons with other interpretations. We emphasize that interpretations also depend very strongly on assumptions about the cosmological history of the universe, and on propagation of antiprotons and positrons in the galaxy. The winos PAMELA is observing arose from some non-thermal sources such as moduli decay rather than a universe that cooled in thermal equilibrium after the big bang. Then it is appropriate to normalize the wino density to the local relic density, and no "boost factors" are needed to obtain the reported PAMELA rates.