Multivariate searches for single top quark production with the D0 detector

Abstract

submitted to Phys. Rev. D, Fermilab preprint - D0We 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

Evidence for electroweak top quark production in proton-antiproton collisions at √s = 1.96 TeV

“…DØ has previously published two analyzes using decision trees and neural networks [17,20] and released preliminary results using a likelihood discriminant method [46]. All three of these methods combine differential distributions, that show discrimination between signal and background events, to form a variable which attempts to maximally separated the signal and background.…”

Experimental Studies of Top Quark Production

“…After first searches for single top quark production [299][300][301], evidence has been reported by the D0 [302,303] collaboration in 2007 and later also by the CDF collaboration [304] in 2008.…”

Measurement of single top quark production at D0 using a matrix element method

“…The polarization of the top quark becomes evident in the angular correlations between the observed daughter particles. It had been suggested to use these correlations to improve the discovery potential [71,56], and variables including those correlations have been directly used to set limits on single top production [90], and recently, to find evidence for single top production [91,92]. This analysis uses those variables indirectly since the matrix elements include a full treatment of spins.…”