Dirac gaugino as leptophilic dark matter

TL;DR

This paper explores Dirac gauginos in an R-symmetric supersymmetric model, highlighting their leptophilic annihilation properties that could explain positron excesses and their detectability in direct detection experiments.

Contribution

It introduces a model where Dirac gauginos have enhanced leptophilic annihilation and detectable scattering cross sections, differing from Majorana gauginos.

Findings

Dirac gauginos can explain PAMELA positron excess without large boost factors.

They have sizable spin-independent scattering cross sections detectable in current experiments.

Their annihilation to hadrons is controlled by Higgsino fraction and specific final states.

Abstract

We investigate the leptophilic properties of Dirac gauginos in an R--symmetric N=2 supersymmetric model with extended gauge and Higgs sectors. The annihilation of Dirac gauginos to leptons requires no chirality flip in the final states so that it is not suppressed as in the Majorana case. This implies that it can be sizable enough to explain the positron excess observed by the PAMELA experiment with moderate or no boost factors. When squark masses are heavy, the annihilation of Dirac gauginos to hadrons is controlled by their Higgsino fraction and is driven by the $hZ$ and $W^+W^-$ final states. Moreover, at variance with the Majorana case, Dirac gauginos with a non-vanishing higgsino fraction can also have a vector coupling with the $Z$ gauge boson leading to a sizable spin--independent scattering cross section off nuclei. Saturating the current antiproton limit, we show that Dirac gauginos can leave a signal in direct detection experiments at the level of the sensitivity of dark matter searches at present and in the near future.