Multivariate searches for single top quark production with the D0 detector

TL;DR

This paper reports a search for single top quark production modes at the Fermilab Tevatron using neural networks and cut-based methods, setting upper limits on production cross sections due to no observed signal.

Contribution

It introduces a combined analysis of s- and t-channel single top production using neural networks and traditional cuts, providing the first limits with this dataset.

Findings

No evidence for single top production was observed.

Upper limits on cross sections were set at 95% confidence level.

Neural network analysis yielded more stringent limits than cut-based analysis.

Abstract

We present a search for electroweak production of single top quarks in the s-channel (p-pbar -> t bbar + X) and t-channel (p-pbar -> tq bbar + X) modes. We have analyzed 230 pb^(-1) of data collected with the D0 detector at the Fermilab Tevatron collider at a center-of-mass energy of sqrt(s) = 1.96 TeV. Two separate analysis methods are used: neural networks and a cut-based analysis. No evidence for a single top quark signal is found. We set 95% confidence level upper limits on the production cross sections using Bayesian statistics, based on event counts and binned likelihoods formed from the neural network output. The limits from the neural network (cut-based) analysis are 6.4 pb (10.6 pb) in the s-channel and 5.0 pb (11.3 pb) in the t-channel.