MEASUREMENT OF TOP QUARK PAIR PRODUCTION CROSS SECTION IN PROTON ANTIPROTON COLLISIONS AT √s = 1.96 TeV IN THE τ + jets FINAL STATE USING 1 fb<sup>-1</sup> OF DATA
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Abstract
This dissertation presents a new measurement of p_p &rarr; t_t X
production at &radic;s = 1.96 TeV using 974.2 pb<sup>-1</sup> of data collected with the
D&Oslash; detector between 2002 and 2006. We focus on the final state
where the W boson from one of the top quarks decays into a
&tau; lepton and its associated neutrino, while the other W boson decays into
a quark-antiquark pair. We aim to select those events in which the
&tau; lepton subsequently decays hadronically, meaning to one or three charged
hadrons, zero or more neutral hadrons and a tau neutrino (the charge conjugate
processes are implied in all of the above). The observable signature
thus consists of a narrow calorimeter shower with associated track(s)
characteristic of a hadronic tau decay, four or more jets, of which
two are initiated by b quarks accompanying the W\'s in the top quark
decays, and a large net missing momentum in the transverse plane due to
the energetic neutrino-antineutrino pair that leave no trace in the
detector media. The preliminary result for the measured cross section is:</dcvalue>\n <dcvalue element="description" qualifier="abstract"/>\n <dcvalue element="description" qualifier="abstract"/>\n <dcvalue element="description" qualifier="abstract">&sigma;(t_t) = 6.9 <sup>+1.2</sup>-1.2 (stat)<sup>+0.8</sup> -0.7 (syst) &plusmn;
0.4 (lumi) pb
This indicates that our finding is consistent with the Standard Model
prediction.
production at &radic;s = 1.96 TeV using 974.2 pb<sup>-1</sup> of data collected with the
D&Oslash; detector between 2002 and 2006. We focus on the final state
where the W boson from one of the top quarks decays into a
&tau; lepton and its associated neutrino, while the other W boson decays into
a quark-antiquark pair. We aim to select those events in which the
&tau; lepton subsequently decays hadronically, meaning to one or three charged
hadrons, zero or more neutral hadrons and a tau neutrino (the charge conjugate
processes are implied in all of the above). The observable signature
thus consists of a narrow calorimeter shower with associated track(s)
characteristic of a hadronic tau decay, four or more jets, of which
two are initiated by b quarks accompanying the W\'s in the top quark
decays, and a large net missing momentum in the transverse plane due to
the energetic neutrino-antineutrino pair that leave no trace in the
detector media. The preliminary result for the measured cross section is:</dcvalue>\n <dcvalue element="description" qualifier="abstract"/>\n <dcvalue element="description" qualifier="abstract"/>\n <dcvalue element="description" qualifier="abstract">&sigma;(t_t) = 6.9 <sup>+1.2</sup>-1.2 (stat)<sup>+0.8</sup> -0.7 (syst) &plusmn;
0.4 (lumi) pb
This indicates that our finding is consistent with the Standard Model
prediction.