LHC Mono-$W/Z$ Signatures as a Probe for Dark Matter Explanations of Astrophysical Excesses

Abstract

The inert two-Higgs doublet model (IDM) is a compelling framework for weakly interacting massive particles (WIMPs) linked to electroweak symmetry breaking. It can account for both the Galactic Center gamma-ray excess (GCE) and the AMS-02 antiproton anomaly while also satisfying relic density and direct detection constraints for dark matter (DM) masses in the $55-75$ GeV range. Three specific DM annihilation channels can be identified: Higgs resonance, $SA$ co-annihilation, and $SS\to W{W}^{\ast }$ annihilation. Among these, the DM mass range of $70-75$ GeV with dominant $SS\to W{W}^{\ast }$ annihilation has received less attention in collider searches. To validate this parameter space, we combine LHC searches for mono-$W/Z$ signatures. In particular, we develop a channel-separation strategy to disentangle the contributions of charged mass splitting (${\Delta }^{\pm }$) and neutral mass splitting (${\Delta }^0$) in the inert scalar sector at the LHC. Our results indicate that most of the parameter space consistent with these astrophysical anomalies in the $SS\to W{W}^{\ast }$ annihilation regime will be testable at the High-Luminosity LHC. Specifically, from the leptonic channel we obtain a $2\sigma$ exclusion limit of $80\lesssim {\Delta }^0\lesssim 260$ GeV, while the hadronic channel yields $30\lesssim {\Delta }^0\lesssim 150$ GeV and $70\lesssim {\Delta }^{\pm }\lesssim 230$ GeV for $m_S=70$ GeV.

Comments: 11 pages, 11 figures, 3 tables. Comments are welcome