Implications on the mUED model from the early LHC data on $\ell+\met$ signal

TL;DR

This paper examines how early LHC data constrains the minimal Universal Extra Dimension (mUED) model, focusing on the second KK mode of the W boson as a potential source of the observed lepton plus missing energy signals.

Contribution

It demonstrates that the second KK W boson in the mUED model can explain certain LHC signals and analyzes the model's parameter space constraints using early LHC data.

Findings

Early LHC data at 1.1 fb$^{-1}$ is insufficient to constrain the mUED model.

LHC data at 5.6 fb$^{-1}$ can exclude most of the mUED parameter space.

Second KK W boson can be a good candidate for the observed $ ext{l}+ ot{E}_T$ signals.

Abstract

Recently the ATLAS and CMS collaborations reported their search for a new heavy gauge boson $W'$ with one lepton plus missing transverse momentum. We find that $W^{(2)}$, the second Kaluza-Kelin (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 SM particle 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 $\ell+\met$ signal for 1.1 fb$^{-1}$ integrated luminosity is shown insufficient to limit our model even with significant indirect production of $W^{(2)}$. However, the results show that the present LHC 5.6 fb$^{-1}$ data can cover most of the reasonable parameter space of the mUED model.