Enriching the exploration of the mUED model with event shape variables at the CERN LHC

TL;DR

This paper introduces a novel event shape variable-based search strategy for detecting new physics models with compressed spectra at the LHC, successfully reducing background noise and extending the reach for mUED particles.

Contribution

It presents a new approach using event shape variables to improve detection of models with small mass differences, specifically applied to the mUED model at the LHC.

Findings

Can explore or exclude mUED with R^{-1} up to 850 GeV at 7 TeV with 12 fb^{-1}

Event shape variables significantly reduce Standard Model backgrounds

Method applicable to other models with compressed spectra

Abstract

We propose a new search strategy based on the event shape variables for new physics models where the separations among the masses of the particles in the spectrum are small. Collider signature of these models, characterised by low $p_T$ leptons/jets and low missing $p_T$, are known to be difficult to look for. The conventional search strategies involving hard cuts may not work in such situations. As a case study, we have investigated the hitherto neglected jets + missing $E_T$ signature -known to be a challenging one - arising from the pair productions and decay of $n =1$ KK-excitations of gluons and quarks in the minimal Universal Extra Dimension (mUED) model. Judicious use of the event shape variables, enables us to reduce the Standard Model backgrounds to a negligible level . We have shown that in mUED, $R^{-1}$ upto $850 ~\rm GeV$, can be explored or ruled out with 12 fb$^{-1}$ of integrated luminosity at the 7 TeV run of the LHC. We also discuss the prospects of employing these variables for searching other beyond standard model physics with compressed or partially compressed spectra.