LHC constraints on a mediator coupled to heavy quarks

Abstract We apply LHC data to constrain a simplified extension of the Standard Model containing a new spin−1 mediator R, which does not couple to first generation quarks, and a spinor dark matter particle χ. We recast ATLAS and CMS searches for final states containing one or more jet(s) + E T , with or without b tags, as well as searches for di–jet resonances with b or t tagging. We find that LHC constraints on the axial vector couplings of the mediator are always stronger than the unitarity bound, which scales like m R / m t . If R has a sizable invisible branching ratio, the strongest LHC bound on both vector couplings and axial vector coupling comes from a di–jet + E T search with or without double b tag. These bounds are quite strong for m R 1 TeV, even though we have switched off all couplings to valence quarks. Searches for a di–jet resonance with double b tag lead to comparable bounds with the previous results even if R → χ χ ¯ decays are allowed; these are the only sensitive LHC searches if the invisible branching ratio of R is very small or zero.