WIMPs at the Galactic Center

TL;DR

This paper shows that WIMP dark matter models with masses up to around 310 GeV can explain the gamma-ray excess observed near the Galactic center, fitting the data with various annihilation final states.

Contribution

It demonstrates for the first time that the gamma-ray excess can be well fit by WIMP annihilations into electroweak bosons, Higgses, or tops, considering systematic uncertainties.

Findings

WIMP masses up to 310 GeV fit the gamma-ray excess.

Annihilation channels include WW, ZZ, hh, tt, and bbar.

Models like MSSM neutralino and Higgs portal can explain the excess.

Abstract

Simple models of weakly interacting massive particles (WIMPs) predict dark matter annihilations into pairs of electroweak gauge bosons, Higgses or tops, which through their subsequent cascade decays produce a spectrum of gamma rays. Intriguingly, an excess in gamma rays coming from near the Galactic center has been consistently observed in Fermi data. A recent analysis by the Fermi collaboration confirms these earlier results. Taking into account the systematic uncertainties in the modelling of the gamma ray backgrounds, we show for the first time that this excess can be well fit by these final states. In particular, for annihilations to $(WW, ZZ, hh, tt)$, dark matter with mass between threshold and approximately (165, 190, 280, 310) GeV gives an acceptable fit. The fit range for $b\bar{b}$ is also enlarged to 35 GeV$\lesssim m_\chi \lesssim$ 165 GeV. These are to be compared to previous fits that concluded only much lighter dark matter annihilating into $b$, $\tau$, and light quark final states could describe the excess. We demonstrate that simple, well-motivated models of WIMP dark matter including a thermal-relic neutralino of the MSSM, Higgs portal models, as well as other simplified models can explain the excess.