SUSY Implications from WIMP Annihilation into Scalars at the Galactic Centre

TL;DR

This paper explores supersymmetric models, especially the next-to-minimal one, to explain the gamma-ray excess from the galactic centre via WIMP annihilation into scalars, offering new channels and potential signals.

Contribution

It demonstrates that the next-to-minimal supersymmetric model can naturally account for the gamma-ray excess through novel annihilation channels and addresses naturalness and Higgs mass issues.

Findings

Good fit to gamma-ray excess with Higgs-pseudoscalar annihilation

Next-to-minimal model solves the mu-problem and explains Higgs mass

Potential detection of Higgs or pseudoscalar decay into photons

Abstract

An excess in gamma-rays emanating from the galactic centre has recently been observed in the Fermi-LAT data. This signal can be interpreted as resulting from WIMP annihilation, with the spectrum well-fit by dark matter annihilating dominantly into either bottom-quark or Higgs pairs. Supersymmetric models provide a well-motivated framework to study the implications of this signal in these channels. With a neutralino dark matter candidate, the gamma-ray excess cannot be easily accommodated in the minimal supersymmetric model, which in any case requires tuning below the percent level to explain the observed Higgs mass. Instead we are naturally led to consider the next-to-minimal model with a singlet superfield. This not only allows for the annihilation channel into bottom-quark pairs to be implemented, but also provides new possibilities for annihilation into Higgs-pseudoscalar pairs. We show that the fit to the gamma-ray excess for the Higgs-pseudoscalar channel can be just as good as for annihilation into bottom-quark pairs. Moreover, in the parameter range of interest, the next-to-minimal supersymmetric model solves the mu-problem and can explain the 125 GeV Higgs mass with improved naturalness. We also consider an extension by adding a right-handed neutrino superfield with the right-handed sneutrino acting as a dark matter candidate. Interestingly, this allows for the annihilation into pseudoscalar pairs which also provide a good fit to the gamma-ray excess. Furthermore, in the case of a neutralino LSP, the late decay of a sneutrino NLSP can non-thermally produce the observed relic abundance. Finally, the WIMP annihilation into scalar pairs allows for the possibility of detecting the Higgs or pseudoscalar decay into two photons, providing a smoking-gun signal of the model.