# Etiquetage des quarks beaux et mesure de la section efficace de production de paires de quarks top à $\sqrt(s)$ = 1,96 TeV dans l'expérience D0

Abstract : The work presented in this thesis concerns the measurement of th e top-antitop production
cross-section in th e lepton + jets ch annel (electron and muon). The analysed data have been
collected with th e DØ detector between 2001 and 2004 at a center-of-mass energy of 1.96
TeV, at the Tevatron proton-antiproton collider located at FERM ILAB.Th ese data correpond
to an integrated luminosity of 160 pb-1 in each ch annel.
Each top quark decays into a W boson and a b quark . Th e first part of th is work h as been
focused on th e elaboration of an algorithm, +-*1, aimed at identifying jets arising from b
quark s decay products. Th is algorithm uses th e impact parameter of th e track s to assign a jet a
probability th at it originates from th e primary interaction point. Its efficiency for top-antitop
events is about 45% with a rejected background of 99.7%.
Th e second part of th is work deals with th e preselection step th at allows isolating events
wh ich are lik ely to be compatible with a W+jets toplogy. M ultijets and W+jets backgrounds
are estimated from real data and simulation. The top pair production cross-section is extracted
from candidate events th at h ave at least three jets, one among them being tagged by th e +-*1
algorithm. Sources of systematics uncertainties have been studied in detail. Results have been
compared with the theoritical expectations and with other measurements performed in the DØ
and CDF experiments.
Keywords :
Document type :
Theses

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Submitted on : Friday, April 22, 2005 - 12:13:08 PM
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### Identifiers

• HAL Id : tel-00009071, version 1

### Citation

Sébastien Greder. Etiquetage des quarks beaux et mesure de la section efficace de production de paires de quarks top à $\sqrt(s)$ = 1,96 TeV dans l'expérience D0. Physique des Hautes Energies - Expérience [hep-ex]. Université Louis Pasteur - Strasbourg I, 2004. Français. ⟨tel-00009071⟩

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