Testing Gluino Spin with Three-Body Decays

TL;DR

This paper investigates how to differentiate a supersymmetric gluino from a Kaluza-Klein gluon at the LHC by analyzing the shapes of dijet invariant mass distributions resulting from three-body decays.

Contribution

It introduces a method to distinguish gluinos from Kaluza-Klein gluons based on decay kinematics and provides estimates for the number of events needed for identification.

Findings

Dijet invariant mass distributions differ significantly between models.

Several thousand events are needed to distinguish models at the LHC.

Monte Carlo simulations confirm the feasibility of the method.

Abstract

We examine the possibility of distinguishing a supersymmetric gluino from a Kaluza-Klein gluon of universal extra dimensions (UED) at the Large Hadron Collider (LHC). We focus on the case when all kinematically allowed tree-level decays of this particle are 3-body decays into two jets and a massive daughter (typically weak gaugino or Kaluza-Klein weak gauge boson). We show that the shapes of the dijet invariant mass distributions differ significantly in the two models, as long as the mass of the decaying particle mA is substantially larger than the mass of the massive daughter mB. We present a simple analysis estimating the number of events needed to distinguish between the two models under idealized conditions. For example, for mA/mB=10, we find the required number of events to be of order several thousand, which should be available at the LHC within a few years. This conclusion is confirmed by a parton level Monte Carlo study which includes the effects of experimental cuts and the combinatoric background.