Search for s-channel single top-quark production in proton-proton collisions at $\sqrt{s}$=8 TeV with the ATLAS detector

TL;DR

This paper reports a search for s-channel single top-quark production at 8 TeV using ATLAS data, employing multivariate analysis to set an upper limit on the production cross-section consistent with the Standard Model.

Contribution

It introduces a multivariate classifier to improve discrimination of s-channel single top-quark events in proton-proton collisions at the LHC.

Findings

Upper limit on cross-section: 14.6 pb at 95% CL

Measured cross-section: 5.0 ± 4.3 pb, consistent with Standard Model

Analysis technique enhances sensitivity to rare top-quark production processes

Abstract

This Letter presents a search at the LHC for s-channel single top-quark production in proton-proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb$^{-1}$. Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of $\sigma_s$=5.0$\pm$4.3 pb, consistent with the Standard Model expectation.