Search for the top quark at D0 using multivariate methods Page: 3 of 14
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Search for the Top Quark at DO using
Pushpalatha C. Bhat
for the DO Collaboration
Fermi National Accelerator Laboratory,
Batavia, IL 60510, U.S.A.
We report on the search for the top quark in pp collisions at the
Fermilab Tevatron (Vh = 1.8 TeV) in the di-lepton and lepton+jets
channels using multivariate methods. An H-matrix analysis of the
e data corresponding to an integrated luminosity of 13.5 1.6 pb-i
yields one event whose likelihood to be a top quark event, assuming
mtop = 180 GeV/c2, is ten times more than that of WW and eighteen
times more than that of Z -+ rr. A neural network analysis of the
e+jets channel using a data sample corresponding to an integrated
luminosity of 47.9 5.7 pb-i shows an excess of events in the signal
region and yields a cross-section for ti production of 6.7 2.3 (stat.)
pb, assuming a top mass of 200 GeV/c2. An analysis of the e+jets data
using the probability density estimation method yields a cross-section
that is consistent with the above result.
The top quark that remained elusive for over a decade and a half has finally
been observed by both the CDF and DO collaborations (1,2). The top quark
events have been observed in the di-lepton and lepton+jets decay modes of tt
pairs produced in pp collisions at /s = 1.8 TeV at the Fermilab Tevatron. The
collaborations have used conventional analysis methods to optimize cuts on
kinematic variables together with the tagging of the b quarks, to discriminate
top quark events from background. The conventional analysis methods do
not exploit correlations amongst the variables on which the cuts are applied
and thus may suffer a loss in signal efficiency. The DO collaboration has
been applying multivariate methods such as the H-matrix, probability density
estimation (PDE) and neural networks for identifying top quark events (3,4),
to improve the signal efficiency. In this paper, we describe the multivariate
methods used, we present an analysis of the channel tt -> e and report on
the measurement of tt production cross-section from a study of the channel
tt -> e+jets.
1993 American Institute of Physics
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Bhat, P.C. Search for the top quark at D0 using multivariate methods, article, July 1, 1995; Batavia, Illinois. (https://digital.library.unt.edu/ark:/67531/metadc621656/m1/3/: accessed April 22, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.