Same-Sign Dilepton Excesses and Light Top Squarks

TL;DR

This paper suggests that the excess of same-sign dilepton events with b-jets and MET observed at LHC Run 1 could be explained by the production of 550 GeV right-handed top squarks decaying into top quarks, W bosons, and MET, and proposes search strategies for Run 2.

Contribution

It introduces a supersymmetric explanation for the LHC excess using light top squarks and proposes specific kinematic cuts to improve detection at 13 TeV.

Findings

A 550 GeV right-handed stop can explain the excess without conflicting with previous limits.

Kinematic cuts at 13 TeV can enhance the stop signal.

Stops could be discovered with 40 fb⁻¹ of data at Run 2.

Abstract

Run 1 data of the Large Hadron Collider (LHC) contain excessive events in the same-sign dilepton channel with b-jets and missing transverse energy (MET), which were observed by five separate analyses from ATLAS and CMS collaborations. We show that these events could be explained by direct production of top squarks (stops) in supersymmetry. In particular, a right-handed stop with a mass of 550 GeV decaying into 2 t quarks, 2 W bosons, and MET could fit the observed excess without being constrained by other direct search limits from Run 1. We propose kinematic cuts at 13 TeV to enhance the stop signal, and estimate that stops could be discovered with 40 inverse fb of integrated luminosity at Run 2 of the LHC, when considering only the statistical uncertainty.