Lepton Portal Dark Matter

Abstract

We study a class of simplified dark matter models in which dark matter couples directly with a mediator and a charged lepton. This class of Lepton Portal dark matter models has very rich phenomenology: it has loop generated dark matter electromagnetic moments that generate a direct detection signal; it contributes to indirect detection in the cosmic positron flux via dark matter annihilation; it provides a signature of the same-flavor, opposite-sign dilepton plus missing transverse energy at colliders. We determine the current experimental constraints on the model parameter space for Dirac fermion, Majorana fermion and complex scalar dark matter cases of the Lepton Portal framework. We also perform a collider study for the 14 TeV LHC reach with 100 inverse femtobarns for dark matter parameter space. For the complex scalar dark matter case, the LHC provides a very stringent constraint and its reach can be interpreted as corresponding to a limit as strong as two tenths of a zeptobarn on the dark matter-nucleon scattering cross section for dark matter masses up to 500 GeV. We also demonstrate that one can improve the current collider searches by using a Breit-Wigner like formula to fit the dilepton MT2 tail of the dominant diboson background.