A New Probe of Dark Sector Dynamics at the LHC

Abstract: We propose a LHC search for dilepton resonances in association with large missing energy as a generic probe of TeV dark sector models. Such resonances can occur if the dark sector includes a U(1) gauge boson, or Z', which kinetically mixes with the Standard Model U(1). For small mixing, direct 2 to 1 production of the Z' is not visible in standard resonance searches due to the large Drell-Yan background. However, there may be significant production of the Z' boson in processes involving other dark sector particles, resulting in final states with a Z' resonance and missing transverse momentum. Examples of such processes include cascade decays within the dark sector and radiation of the Z' off of final state dark sector particles. Even when the rate to produce a Z' boson in a dark sector process is suppressed, this channel can provide better sensitivity than traditional collider probes of dark sectors such as monojet searches. We find that data from the 8 TeV LHC run can be interpreted to give bounds on such processes; more optimized searches could extend the sensitivity and continue to probe these models in the Run II data.