Recently, the ATLAS and CMS collaborations reported their search for a new heavy gauge boson $W^{\prime }$ 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 $\ell \nu$ 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 $\ell +{\mathrm{E̸}}_T$ signal for $1.1{\mathrm{fb}}^{-1}$ integrated luminosity is shown insufficient to limit our model. However, the results show that the present LHC $5.6{\mathrm{fb}}^{-1}$ data can cover most of the reasonable parameter space of the mUED model.

• Received 12 December 2011

DOI:https://doi.org/10.1103/PhysRevD.85.055006