'Fat-brane' Universal Extra Dimension model confronted with the ATLAS multi-jet and photonic searches at 13 TeV LHC

TL;DR

This paper evaluates the 'fat-brane' minimal Universal Extra Dimensions model against recent ATLAS 13 TeV LHC searches, constraining model parameters due to no observed excess events in multi-jet and photon+jets channels.

Contribution

It provides the first detailed confrontation of the fat-mUED model with recent LHC data, setting bounds on its parameters based on experimental results.

Findings

No significant excess observed in ATLAS searches.

Constraints placed on the higher-dimensional Planck mass.

Limits established on the compactification scale.

Abstract

The current status of `fat-brane' minimal Universal Extra Dimensions (fat-mUED) is studied in the light of ATLAS experiment's recent reports. At the Large Hadron Collider (LHC) color charged first level Kaluza-Klein (KK) particles (first level excited quarks and gluons) can be abundantly pair-produced due to conserved quantity, viz., KK-parity, and strong interaction. The cascade decay of these particles to one or more Standard Model (SM) particle(s) and lighter first level KK particle(s) stops after producing the lightest excited massive state, named as the lightest KK particle (LKP). With the presence of gravity induced decays, stability of the LKP is lost and it may decay to photon or Z-boson by radiating KK-excited gravitons, hence leading to final state with photon(s) at the LHC. A variant signal topology is established when pair-produced first level colored KK particles undergo direct decay to an associated SM partner along with KK-excitations of graviton; thus leading to a signal with two hard jets and substantial missing energy. The ATLAS experiment lately reported two searches at 13 TeV LHC with 139 inverse-femtobarn of data; (i) multi-jet and (ii) photon and jets with missing energy. In both searches, the results showed no substantial deviation from the number of background events of the SM. Provided the absence of any number of excess events in both searches we constrained the parameters of the fat-mUED model, viz., the higher-dimensional Planck mass and the compactification scale.