Top Squark Searches Using Dilepton Invariant Mass Distributions and Bino-Higgsino Dark Matter at the LHC

TL;DR

This paper explores top squark pair production at the 8-TeV LHC within the MSSM, focusing on Bino-Higgsino neutralino mixing, and proposes a method to detect this scenario through dilepton invariant mass distributions.

Contribution

It introduces a novel analysis of top squark decays involving Bino-Higgsino neutralinos and dilepton mass edges to probe dark matter and supersymmetry at the LHC.

Findings

Clear dilepton mass edge observed in light sleptons case.

Optimized cuts improve discovery significance.

Method distinguishes Bino-Higgsino dark matter scenarios.

Abstract

Pair production of light top squarks at the 8-TeV LHC can be used to probe the gaugino-Higgsino sector of the Minimal Supersymmetric Standard Model. The case where the lightest neutralino is a mixture of Bino and Higgsino, satisfying the thermal dark matter relic density, is investigated. In such a scenario, the lightest top squark decays mostly into $(i)$ a top quark plus the second or third lightest neutralino, and $(ii)$ a bottom quark plus the lightest chargino, instead of a decay scenario of the lightest top squark into a top quark and the lightest neutralino. Final states with $\geq 2$ jets, dileptons, and missing energy are expected in a subsequent decay of the second or third lightest neutralinos into the lightest neutralino via an intermediate slepton ("light sleptons" case) or $Z$ boson ("heavy sleptons" case). The opposite-sign same flavor dilepton mass distribution after subtracting the opposite-sign different flavor distribution shows a clear edge in the case of light sleptons. The significance for discovering such a scenario is calculated with optimized cuts in both light and heavy sleptons cases.