SUSY explanation of the Fermi Galactic Center Excess and its test at LHC Run-II

TL;DR

This paper investigates whether the Fermi Galactic Center Excess can be explained by supersymmetric dark matter models, and tests this hypothesis against collider and direct detection constraints, finding most scenarios are testable or excluded.

Contribution

It provides a detailed analysis of supersymmetric explanations for the GCE, including collider signatures and direct detection prospects, with specific parameter bounds and testability assessments.

Findings

GCE can be explained by 30-40 GeV dark matter with specific annihilation channels.

LHC Run-II data can exclude most GCE explanations at 95% confidence level.

Future direct detection experiments may test most of the GCE-favored parameter space.

Abstract

We explore the explanation of the Fermi Galactic Center Excess (GCE) in the Next-to-Minimal Supersymmetric Standard Model. We systematically consider various experimental constraints including the Dark Matter (DM) relic density, DM direct detection results and indirect searches from dwarf galaxies. We find that, for DM with mass ranging from $30 {\rm GeV}$ to $40 {\rm GeV}$, the GCE can be explained by the annihilation $\chi \chi \to a^\ast \to b \bar{b}$ only when the CP-odd scalar satisfies $m_a \simeq 2 m_\chi$, and in order to obtain the measured DM relic density, a sizable $Z$-mediated contribution to DM annihilation must intervene in the early universe. As a result, the higgsino mass $\mu$ is upper bounded by about 350 GeV. Detailed Monte Carlo simulations on the $3\ell+ E_T^{miss}$ signal from neutralino/chargino associated production at 14-TeV LHC indicate that the explanation can be mostly (completely) excluded at $95\%$ C.L. with an integrated luminosity of 100(200) fb$^{-1}$. We also discuss the implication of possible large $Z$ coupling to DM for the DM-nucleon spin dependent (SD) scattering cross section, and find that although the current experimental bounds on $\sigma^{\rm SD}_p$ is less stringent than the spin independent (SI) results, the future XENON-1T and LZ data may be capable of testing most parts of the GCE-favored parameter region.