Measurement of single top-quark production in the s-channel in proton$-$proton collisions at $\mathrm{\sqrt{s}=13}$ TeV with the ATLAS detector

TL;DR

This paper reports a measurement of single top-quark production in the s-channel at 13 TeV using the ATLAS detector, achieving a significance of 3.3 standard deviations and a cross-section consistent with the Standard Model.

Contribution

First measurement of s-channel single top-quark production at 13 TeV with advanced matrix element analysis and significance estimation.

Findings

Observed signal significance of 3.3 standard deviations.

Measured cross-section of 8.2 pb with uncertainties.

Results are consistent with Standard Model predictions.

Abstract

A measurement of single top-quark production in the s-channel is performed in proton$-$proton collisions at a centre-of-mass energy of 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. The dataset corresponds to an integrated luminosity of 139 fb$^{-1}$. The analysis is performed on events with an electron or muon, missing transverse momentum and exactly two $b$-tagged jets in the final state. A discriminant based on matrix element calculations is used to separate single-top-quark s-channel events from the main background contributions, which are top-quark pair production and $W$-boson production in association with jets. The observed (expected) signal significance over the background-only hypothesis is 3.3 (3.9) standard deviations, and the measured cross-section is $\sigma=8.2^{+3.5}_{-2.9}$ pb, consistent with the Standard Model prediction of $\sigma^{\mathrm{SM}}=10.32^{+0.40}_{-0.36}$ pb.