Neutralino dark matter and the Fermi gamma-ray lines

TL;DR

This paper explores how singlet extensions of the MSSM, especially the NMSSM, can enhance neutralino annihilation into gamma-ray lines, potentially explaining Fermi observations while remaining consistent with other constraints.

Contribution

It demonstrates that a singlet-like pseudoscalar in the NMSSM can boost gamma-ray line signals and discusses the resulting phenomenology at the LHC and in direct detection experiments.

Findings

Enhanced gamma-ray line signals with a singlet pseudoscalar are possible.

Characteristic light neutralino and chargino spectrum at the LHC.

Promising prospects for future direct detection experiments.

Abstract

Motivated by recent claims of lines in the Fermi gamma-ray spectrum, we critically examine means of enhancing neutralino annihilation into neutral gauge bosons. The signal can be boosted while remaining consistent with continuum photon constraints if a new singlet-like pseudoscalar is present. We consider singlet extensions of the MSSM, focusing on the NMSSM, where a `well-tempered' neutralino can explain the lines while remaining consistent with current constraints. We adopt a complementary numerical and analytic approach throughout in order to gain intuition for the underlying physics. The scenario requires a rich spectrum of light neutralinos and charginos leading to characteristic phenomenological signatures at the LHC whose properties we explore. Future direct detection prospects are excellent, with sizeable spin-dependent and spin-independent cross-sections.