Search of new resonances decaying into top quark pairs in the lepton+jet final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector

TL;DR

This paper reports a search for new resonances decaying into top-quark pairs in proton-proton collisions at 13 TeV, using the ATLAS detector, with no significant deviations from the Standard Model observed.

Contribution

It introduces a model-independent search approach for new resonances in top-quark pairs at the LHC, including specific benchmark models and advanced background estimation techniques.

Findings

Results are consistent with Standard Model predictions.

No evidence of new resonances was observed.

The analysis sets constraints on benchmark models like Z'_{TC2}, Kaluza-Klein gluon, and graviton.

Abstract

A search for resonances produced in 13 TeV proton-proton collisions and decaying into top-quark pairs is presented. In this study events where the top-quark decay produces a single isolated charged lepton, missing transverse momentum and jet activity compatible with a hadronic top-quark decay recorded with the ATLAS detector at the Large Hadron Collider (LHC) are considered. We investigate the observed invariant mass spectrum in a model-independent approach to seek for any significant deviation from the Standard Model (SM) background expectation. The Matrix Method was used to estimate the QCD multi-jet background, which has large statistical and systematic uncertainties when modelled using Monte Carlo techniques. We have performed general searches for new resonances for a specific benchmark models: $Z^{'}_{TC2}$ boson, Kaluza-Klein gluon and Kaluza-Klein graviton that decay into top-quark pairs. Taking into account all uncertainties, results are in line with SM expectations. A synopsis of the results followed by an explanation of key findings will be presented.