Search for heavy particles decaying into top-quark pairs using lepton-plus-jets events in proton-proton collisions at $\sqrt{s} = 13$ TeV with the ATLAS detector

TL;DR

This paper reports a search for new heavy particles decaying into top-quark pairs in proton-proton collisions at 13 TeV, using ATLAS data, finding no significant deviations and setting exclusion limits on various models.

Contribution

First search using 13 TeV ATLAS data to look for heavy particles decaying into top-quark pairs with lepton-plus-jets events, establishing new exclusion limits.

Findings

No significant excess observed in top-quark pair spectrum.

Set exclusion limits on Z', Kaluza-Kein gluons, and gravitons.

Analyzed 36.1 fb$^{-1}$ of data at 13 TeV.

Abstract

A search for new heavy particles that decay into top-quark pairs is performed using data collected from proton-proton collisions at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. The integrated luminosity of the data sample is 36.1 fb$^{-1}$. Events consistent with top-quark pair production are selected by requiring a single isolated charged lepton, missing transverse momentum and jet activity compatible with a hadronic top-quark decay. Jets identified as likely to contain $b$-hadrons are required to reduce the background from other Standard Model processes. The invariant mass spectrum of the candidate top-quark pairs is examined for excesses above the background expectation. No significant deviations from the Standard Model predictions are found. Exclusion limits are set on the production cross-section times branching ratio for hypothetical $Z'$ bosons, Kaluza-Kein gluons and Kaluza-Klein gravitons that decay into top-quark pairs.