Illuminating Scalar Dark Matter Co-Scattering in EFT with Monophoton Signatures

TL;DR

This paper explores how co-scattering processes involving scalar dark matter candidates can be constrained and probed at colliders, specifically through mono-photon signatures, within an effective field theory framework.

Contribution

It introduces a novel EFT model with Z2-odd singlets, analyzing co-scattering mechanisms for dark matter relic density and collider constraints, including LHC and HL-LHC prospects.

Findings

Identifies parameter regions where co-scattering dominates relic density.

Shows current LHC mono-$\\gamma$ constraints limit the model.

Proposes HL-LHC can further probe the model.

Abstract

We investigate the co-scattering mechanism for dark matter production in an EFT framework which contains new $Z_2$-odd singlets, namely two fermions $N_{1,2}$ and a real scalar $\chi$. The singlet scalar $\chi$ is the dark matter candidate. The dimension-5 operators play a vital role to set the observed DM relic density. We focus on a nearly degenerate mass spectrum for the $Z_2$ odd particles to allow for a significant contribution from the co-scattering or co-annihilation mechanisms. We present two benchmark points where either of the two mechanisms primarily set the DM relic abundance. The main constraint on the model at the LHC arise from the ATLAS mono-$\gamma$ search. We obtain the parameter space allowed by the observed relic density and the mono-$\gamma$ search after performing a scan over the key parameters, the masses $M_{N_{1,2}}, M_\chi$ and couplings $c_3^\prime, y^\prime_{11,22}$. We find the region of parameter space where the relic abundance is set primarily by the co-scattering mechanism while being allowed by the LHC search. We also determine how the model can be further probed at the HL-LHC via the mono-$\gamma$ signature.