Search for the minimal universal extra dimension model at the LHC with $\sqrt{s}$=7 TeV

Abstract

Universal Extra Dimension (UED) model is one of the popular extension of the Standard Model (SM) which offers interesting phenomenology. In the minimal UED (mUED) model, Kaluza-Klein (KK) parity conservation ensures that $n=1$ KK states can only be pair produced at colliders and the lightest KK particle is stable. In most of the parameter space, first KK excitation of SM hypercharge gauge boson is the lightest one and it can be a viable dark matter candidate. Thus, the decay of $n=1$ KK particles will always involve missing transverse energy as well as leptons and jets. The production cross sections of $n=1$ KK particles are large and such particles may be observed at the Large Hadron Collider (LHC). We explore the mUED discovery potential of the LHC with $\sqrt{s}$ = 7 TeV in the multileptonic final states. Since in the early LHC run, precise determination of missing transverse energy may not be possible, we examine the LHC reach with and without using missing transverse energy information. We observe that missing transverse energy cut will not improve mUED discovery reach significantly. We have found that opposite sign di-lepton channel is the most promising discovery mode and with first $fb^{-1}$ of collected luminosity, LHC will be able to discover the strongly interacting $n=1$ KK particles with masses upto 800 to 900 GeV.