Search for Heavy Stops with Merged Top-Jets

TL;DR

This paper proposes a jet-substructure technique to identify merged top-jets from heavy stop decays at the LHC, enhancing signal detection efficiency in challenging phase space regions.

Contribution

It introduces a novel strategy combining jet substructure and MT2 variable to improve heavy stop search sensitivity at the LHC.

Findings

50% increase in signal-to-background ratio

Mild increase in discovery significance

Effective for stops around 1.2 TeV with 100 fb$^{-1}$ data

Abstract

We study an interesting region of phase space at the LHC for pair-produced stops decaying into hadronic top quarks and light neutralinos. After imposing a sizeable cut on the missing transverse energy, which is the key variable for reducing backgrounds, we have found that the two hadronic tops are likely to merge into a single fat jet. We develop a jet-substructure-based strategy to tag the two merged top-jets and utilize the MT2 variable to further reduce the backgrounds. We obtain about a 50% increase to the ratio of the signal over background and a mild increase on the signal discovery significance, based on a signal with a 1.2 TeV stop and a 100 GeV neutralino, for the 13 TeV LHC with 100 fb$^{-1}$. The general event kinematics could also occur and be explored for other new physics signatures with large missing transverse energy.