Search for Single Top Quark Production Using Likelihood Discriminants at D0 in Run II

TL;DR

This paper reports an improved search for single top quark production in proton-antiproton collisions using likelihood discriminants and b-tagging, setting new upper limits on production cross sections based on D0 Run II data.

Contribution

It introduces an enhanced analysis method combining likelihood discriminants and impact-parameter b-tagging to improve sensitivity in single top quark searches.

Findings

Set 95% CL upper limits: 5.0 pb (s-channel), 4.4 pb (t-channel).

Used nearly 370 pb^{-1} of data from D0 Run II.

Applied likelihood discriminants to separate signal from background.

Abstract

We present an improved search for single top quarks in two production modes, s-channel (tb) and t-channel (tqb). The search is performed in the electron+jets and muon+jets decay channels, with one or more b-tagged jets, on nearly 370 pb^{-1} of D0 Run II data collected between August 2002 and October 2004. Impact-parameter based b-quark tagging is used to select signal-like events. We use a likelihood discriminant method to separate signals from backgrounds. The resulting expected/observed 95% confidence level upper limits on the single top quark production cross sections are 3.3/5.0pb (s-channel) and 4.3/4.4pb (t-channel).