Bounds on Universal Extra Dimension from LHC Run I and II data

TL;DR

This paper analyzes collider data from LHC Run I and II to establish bounds on the minimal Universal Extra Dimension model, focusing on parameters like the compactification scale and cutoff scale, and explores how different search channels constrain the model.

Contribution

It provides updated collider bounds on mUED parameters using LHC data, highlighting the dependence on the cutoff scale and exploring various search channels.

Findings

Strongest bound on $R^{-1}$ is ~950 GeV from dimuon searches.

Bounds weaken for small cutoff scale $\\Lambda$ due to near-degenerate KK spectrum.

Monojet and multijet searches further constrain the low $\\Lambda$ region.

Abstract

We discuss the collider bounds on minimal Universal Extra Dimension (mUED) model from LHC Run-I and II data. The phenomenology of mUED is determined by only two parameters namely, the compactification scale ($R^{-1}$) of the extra dimension and cutoff scale ($\Lambda$) of the theory. The characteristic feature of mUED is the occurrence of nearly degenerate mass spectrum for the Kaluza-Klein (KK) particles and hence, soft leptons, soft jets at the collider experiments. The degree of degeneracy of KK-mass spectrum crucially depends on $\Lambda$. The strongest direct bound on $R^{-1}$ ($\sim $950 GeV for large $\Lambda$) arises from a search for a pair of soft dimuons at the Large Hadron Collider (LHC) experiment with 8 TeV center-of-mass energy and $20~{\rm fb}^{-1}$ integrated luminosity. However, for small $\Lambda$ and hence, small splitting within the first KK-level, the bounds from the dimuon channel is rather weak. On the other hand, the discovery of 126 GeV Higgs boson demands small $\Lambda$ to prevent the scalar potential form being unbounded from below. We discuss LHC monojet searches as a probe of low $\Lambda$ region of mUED parameter space. We also compute bounds on the mUED parameter space from 13 TeV multijets results.