New Positron Spectral Features from Supersymmetric Dark Matter - a Way to Explain the PAMELA Data?

TL;DR

This paper explores how electromagnetic radiative corrections in supersymmetric dark matter models can produce distinctive positron spectral features, potentially explaining the PAMELA positron excess, but requiring large boost factors and specific model parameters.

Contribution

It demonstrates that radiative corrections can significantly enhance positron yields in supersymmetric dark matter models, offering a possible explanation for PAMELA's positron excess.

Findings

Radiative corrections can boost positron yields in certain supersymmetric models.

A sharp cutoff in the positron spectrum may fit PAMELA data.

Large boost factors are needed to match observed positron excess.

Abstract

The space-borne antimatter experiment PAMELA has recently reported a surprising rise in the positron to electron ratio at high energies. It has also recently been found that electromagnetic radiative corrections in some cases may boost the gamma-ray yield from supersymmetric dark matter annihilations in the galactic halo by up to three or four orders of magnitude, providing distinct spectral signatures for indirect dark matter searches to look for. Here, we investigate whether the same type of corrections can also lead to sizeable enhancements in the positron yield. We find that this is indeed the case, albeit for a smaller region of parameter space than for gamma rays; selecting models with a small mass difference between the neutralino and sleptons, like in the stau coannihilation region in mSUGRA, the effect becomes more pronounced. The resulting, rather hard positron spectrum with a relatively sharp cutoff may potentially fit the rising positron ratio measured by the PAMELA satellite. To do so, however, very large "boost factors" have to be invoked that are not expected in current models of halo structure. If the predicted cutoff would also be confirmed by later PAMELA data or upcoming experiments, one could either assume non-thermal production in the early universe or non-standard halo formation to explain such a spectral feature as an effect of dark matter annihilation. At the end of the paper, we briefly comment on the impact of radiative corrections on other annihilation channels, in particular antiprotons and neutrinos.