The case for 100 GeV bino dark matter: A dedicated LHC tri-lepton search

TL;DR

This paper proposes a specialized LHC tri-lepton search strategy to detect 100 GeV bino-like dark matter in compressed supersymmetric spectra, which are not accessible by traditional searches, potentially enabling discovery with current data.

Contribution

It introduces a new search approach focusing on chargino and neutralino production with low missing energy, improving sensitivity to compressed pMSSM scenarios at the LHC.

Findings

Enhanced sensitivity for low mass gaps (down to 9 GeV) with 300 fb$^{-1}$ of data.

Potential to discover 100 GeV bino dark matter in compressed spectra.

Counterintuitive increase in sensitivity by requiring low missing transverse energy.

Abstract

Global fit studies performed in the pMSSM and the photon excess signal originating from the Galactic Center seem to suggest compressed electroweak supersymmetric spectra with a $\sim$100 GeV bino-like dark matter particle. We find that these scenarios are not probed by traditional electroweak supersymmetry searches at the LHC. We propose to extend the ATLAS and CMS electroweak supersymmetry searches with an improved strategy for bino-like dark matter, focusing on chargino plus next-to-lightest neutralino production, with a subsequent decay into a tri-lepton final state. We explore the sensitivity for pMSSM scenarios with $\Delta m = m_{\rm NLSP} - m_{\rm LSP} \sim (5 - 50)$ GeV in the $\sqrt{s} = 14$ TeV run of the LHC. Counterintuitively, we find that the requirement of low missing transverse energy increases the sensitivity compared to the current ATLAS and CMS searches. With 300 fb$^{-1}$ of data we expect the LHC experiments to be able to discover these supersymmetric spectra with mass gaps down to $\Delta m \sim 9$ GeV for DM masses between 40 and 140 GeV. We stress the importance of a dedicated search strategy that targets precisely these favored pMSSM spectra.