Measurement of the Stau Minus Neutralino Mass Difference and Mgluino in the Co-Annihilation Region at the LHC

TL;DR

This paper explores how to measure the small mass difference between the stau and neutralino, and the gluino mass, at the LHC using tau lepton signatures, focusing on the co-annihilation region relevant for dark matter.

Contribution

It introduces a method to simultaneously determine the stau-neutralino mass difference and gluino mass using tau lepton observables in the co-annihilation region at the LHC.

Findings

Able to measure dM to 15% accuracy with 30 fb^-1 of data.

Can determine gluino mass Mg to 6% precision.

Method effective for dM > 5 GeV.

Abstract

We study the prospects for the measurement of the stau - lightest neutralino mass difference (dM) and the gluino mass (Mg) in the supersymmetric co-annihilation region at the LHC using tau leptons. Recent WMAP measurements of the amount of cold dark matter and previous accelerator experiments indicate that the coannihilation region of mSUGRA is characterized by a small dM (5-15 GeV). Focusing on taus from N2 -> tau stau -> tau tau N1 decays in gluino and squark production, we consider inclusive 3 tau+jet+missing Et production, with two taus above a high Et threshold and a third tau above a lower threshold. Two observables, the number of opposite-signed tau pairs minus the number of like-signed tau pairs and the peak of the ditau invariant mass distribution, allow for the simultaneous determination of dM and Mg for dM >5 GeV. For example, for dM = 9 GeV and Mg =850 GeV and with 30 fb^-1 of data, we can measure dM to 15% and Mg to 6%.