Measurements of top quark pair relative differential cross-sections with ATLAS in pp collisions at $\sqrt{s} = 7\ \mbox{TeV}$

G Aad,J J Veillet,M Kataoka,J-Y Hostachy,N Tannoury,P Barrillon,D Tsionou,S Aoun,C Guicheney,F Etienne,J Odier,F Niedercorn,N Ghodbane,C Biscarat,E B F G Knoops,R Febbraro,S Albrand,E Cogneras,G Rahal,B Dechenaux,C Weydert,S Abdel Khalek,F Podlyski,P Perrodo,P A Delsart,T Todorov,M Schwoerer,L Aperio Bella,F Wicek,H Przysiezniak,E Laisne,F Vannucci,M Teinturier,G Sauvage,N Massol,N Bousson,E Le Guirriec,P Matricon,A Renaud,L Di Ciaccio,C Arnault,R Zitoun,J Hřivnáč ,Y Coadou,N Berger,E Busato,M Kado,J.-F Grivaz,L Iconomidou-Fayard,A Lounis,P Pralavorio,I Wingerter-Seez,L Poggioli,L Vacavant,V Lombardo ,F Ledroit-Guillon,M Delmastro,N Andari,D Zerwas,J C Clémens ,S Elles,M Talby,E Petit,J Idárraga ,M Escalier,C Bertella,C Bourdarios,J Levêque,B Clément ,T Délemontex ,R Lafaye,M Martínez ,A Llères ,J Schaarschmidt,S Tisserant,D Fournier,E Sauvan,J B Sauvan,J Wang,T Hryn’Ova,H Liao,G Rybkin,A C Schaffer,I Vukotić ,E Monnier,B Aubert,J Collot,F Touchard,C Santoni,M Benoit,X Sun,F Malek,F Djama,Zhiqing Philippe Zhang ,L Fayard,J Stark,J Labbé ,Reina Coromoto Camacho Toro ,D Hoffmann,M H Genest,A Rozanov,N Makovec,S Calvet,C P Bee,D Rousseau,D Boumediene,D Cinca,Q Buat,E Augé ,J Tóth ,L Duflot,L Serin,B Trocmé,A Lucotte,H Abreu,J Donini,S Simion,D Calvet,T K O Doan,B Li,S Henrot-Versillé ,R Tanaka,E Richter-Wąs ,D Pallin,D Paredes Hernandez,L Feligioni,J Maurer,P Puzo,S Cŕéṕe-Renaudin ,J Colás ,S Binet,C De La Taille ,F Hubaut,F Vazeille,J De Vivie De B Regie ,C Goy,S Jézéquel

doi:10.1140/epjc/s10052-012-2261-1

Abstract

Measurements are presented of differential cross-sections for top quark pair production in pp collisions at sqrt(s) = 7 TeV relative to the total inclusive top quark pair production cross-section. A data sample of 2.05/fb recorded by the ATLAS detector at the Large Hadron Collider is used. Relative differential cross-sections are derived as a function of the invariant mass, the transverse momentum and the rapidity of the top quark pair system. Events are selected in the lepton (electron or muon) + jets channel. The background-subtracted differential distributions are corrected for detector effects, normalized to the total inclusive top quark pair production cross-section and compared to theoretical predictions. The measurement uncertainties range typically between 10% and 20% and are generally dominated by systematic effects. No significant deviations from the Standard Model expectations are observed.

Highlights

The top quark [1, 2] is the most massive known fundamental constituent of matter
This paper focuses on three observables of the ttsystem: the invariant mass, the transverse momentum and the rapidity
The multijet background with misidentified and non-prompt leptons in both the e + jets and μ + jets channels is evaluated with a matrix method, which relies on defining loose and tight lepton samples [3, 45] and measuring the fractions of real and fake loose leptons that are selected as tight leptons

Summary

Introduction

The top quark [1, 2] is the most massive known fundamental constituent of matter. Its unexplained large mass suggests an important connection to the electroweak symmetry breaking mechanism. The main expected backgrounds in the lepton + jets channel are W + jets which can give rise to the same final state as the ttsignal, and fake leptons. They are both estimated using auxiliary measurements. The multijet background with misidentified and non-prompt leptons (referred to collectively as fake leptons) in both the e + jets and μ + jets channels is evaluated with a matrix method, which relies on defining loose and tight lepton samples [3, 45] and measuring the fractions of real (εreal) and fake (εfake) loose leptons that are selected as tight leptons. Contributions from W + jets and Z + jets backgrounds are subtracted in the control regions using Monte Carlo simulation

Methods

Results

Conclusion