Implications on the minimal universal extra dimension model from the early LHC data onℓ+E̸Tsignal

Abstract

Recently, the ATLAS and CMS collaborations reported their search for a new heavy gauge boson ${W}^{\ensuremath{'}}$ with one lepton plus missing transverse momentum. We find that ${W}^{(2)}$, the second Kaluza-Klein (KK) state of the $W$ boson in the minimal universal extra dimension (mUED) model, can be a good candidate for this signal, as its branching ratio into $\ensuremath{\ell}\ensuremath{\nu}$ is sizable. Moreover, nearly degenerate KK mass spectra in the mUED model yield generically very soft standard model particles accompanying ${W}^{(2)}$ from the subsequent decays of the second KK quarks and gluons. In a hadron collider, this indirect ${W}^{(2)}$ production is difficult to distinguish from the ${W}^{(2)}$ single production. The involved strong interactions make it more important than the single production. The early LHC data on $\ensuremath{\ell}+{\mathrm{E\ensuremath{\llap{\not\;}}}}_{T}$ signal for $1.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ integrated luminosity is shown insufficient to limit our model. However, the results show that the present LHC $5.6\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ data can cover most of the reasonable parameter space of the mUED model.