Searching for Top Squarks at the LHC in Fully Hadronic Final State

TL;DR

This paper explores detecting light top squarks at the LHC in fully hadronic final states, using the $M3$ variable to reconstruct top quarks and reduce background, achieving potential discovery for stop masses 350-500 GeV.

Contribution

It introduces a kinematic variable $M3$ for reconstructing top quarks in fully hadronic stop decays at 8 TeV LHC, enhancing signal-background discrimination.

Findings

Possible to observe signals for stop masses 350-500 GeV.

Effective background reduction using identified kinematic variables.

Signal and background cross-sections can be comparable in the targeted mass range.

Abstract

We pursue a scenario where the lighter top squark (stop) mass is accessible for the Large Hadron Collider (LHC) in the near future, while gluinos and first two generation squarks are heavier. At $\sqrt{s} = 8$ TeV, we investigate the identification of stops which decay predominantly into a top quark and the stable lightest supersymmetric particle. We use a simple kinematical variable, $M3$, to reconstruct two top quarks which are pair-produced from the stops, in the fully hadronic channel. The dominant Standard Model (SM) background for this signal stems from $t\bar t$ plus jets, with one top quark decaying into $ bl\nu$, where the lepton is undetected and the $\nu$ produces missing transverse momentum. The lepton identification efficiency is thus crucial in order to estimate the background correctly. We identify kinematical variables to reduce the SM background. We find that it is possible to achieve signal and background cross-section at similar levels for stop masses around $350 - 500$ GeV for a neutralino mass of 100 GeV.