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Title: Measurement of the tt¯ production cross-section using eμ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector

Abstract

The inclusive top quark pair (tt) production cross-section σ tt has been measured in proton–proton collisions at √s = 7 TeV and√s = 8 TeV with the ATLAS experiment at the LHC, using tt events with an opposite-charge eμ pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb -1 and the 2012 8 TeV dataset of 20.3 fb -1 . The numbers of events with exactly one and exactly two b-tagged jets were counted and used to simultaneously determine σ tt and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section was measured to be: σ tt = 182.9 ± 3.1 ± 4.2 ± 3.6 ± 3.3 pb (√s = 7 TeV) and σ tt = 242.4 ± 1.7 ± 5.5 ± 7.5 ± 4.2 pb (√s = 8 TeV), where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance ofmore » the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically predicted cross-section on m pole t giving a result of m pole t = 172.9 +2.5 -2.6 GeV. By looking for an excess of tt production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks t 1 with masses close to the top quark mass, decaying via t 1 → t χ 0 1 to predominantly right-handed top quarks and a light neutralino χ 0 1 , the lightest supersymmet-ric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95 % confidence level.« less

Authors:
 [1]
  1. Aix-Marseille Univ. and CNRS/IN2P3, Marseille (France). et al.
Publication Date:
Research Org.:
Argonne National Laboratory (ANL), Argonne, IL (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
Contributing Org.:
ATLAS Collaboration
OSTI Identifier:
1225721
Alternate Identifier(s):
OSTI ID: 1225376; OSTI ID: 1407254
Grant/Contract Number:  
AC02-06CH11357; AC02-05CH11231; SC00112704; AC03-76SF00515
Resource Type:
Accepted Manuscript
Journal Name:
European Physical Journal. C, Particles and Fields
Additional Journal Information:
Journal Volume: 74; Journal Issue: 10; Journal ID: ISSN 1434-6044
Publisher:
Springer
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats

Aad, G. Measurement of the tt¯ production cross-section using eμ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector. United States: N. p., 2014. Web. doi:10.1140/epjc/s10052-014-3109-7.
Aad, G. Measurement of the tt¯ production cross-section using eμ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector. United States. https://doi.org/10.1140/epjc/s10052-014-3109-7
Aad, G. Wed . "Measurement of the tt¯ production cross-section using eμ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector". United States. https://doi.org/10.1140/epjc/s10052-014-3109-7. https://www.osti.gov/servlets/purl/1225721.
@article{osti_1225721,
title = {Measurement of the tt¯ production cross-section using eμ events with b-tagged jets in pp collisions at √s = 7 and 8 TeV with the ATLAS detector},
author = {Aad, G.},
abstractNote = {The inclusive top quark pair (tt) production cross-section σ tt has been measured in proton–proton collisions at √s = 7 TeV and√s = 8 TeV with the ATLAS experiment at the LHC, using tt events with an opposite-charge eμ pair in the final state. The measurement was performed with the 2011 7 TeV dataset corresponding to an integrated luminosity of 4.6 fb -1 and the 2012 8 TeV dataset of 20.3 fb -1 . The numbers of events with exactly one and exactly two b-tagged jets were counted and used to simultaneously determine σ tt and the efficiency to reconstruct and b-tag a jet from a top quark decay, thereby minimising the associated systematic uncertainties. The cross-section was measured to be: σ tt = 182.9 ± 3.1 ± 4.2 ± 3.6 ± 3.3 pb (√s = 7 TeV) and σ tt = 242.4 ± 1.7 ± 5.5 ± 7.5 ± 4.2 pb (√s = 8 TeV), where the four uncertainties arise from data statistics, experimental and theoretical systematic effects, knowledge of the integrated luminosity and of the LHC beam energy. The results are consistent with recent theoretical QCD calculations at next-to-next-to-leading order. Fiducial measurements corresponding to the experimental acceptance of the leptons are also reported, together with the ratio of cross-sections measured at the two centre-of-mass energies. The inclusive cross-section results were used to determine the top quark pole mass via the dependence of the theoretically predicted cross-section on m pole t giving a result of m pole t = 172.9 +2.5 -2.6 GeV. By looking for an excess of tt production with respect to the QCD prediction, the results were also used to place limits on the pair-production of supersymmetric top squarks t 1 with masses close to the top quark mass, decaying via t 1 → t χ 0 1 to predominantly right-handed top quarks and a light neutralino χ 0 1 , the lightest supersymmet-ric particle. Top squarks with masses between the top quark mass and 177 GeV are excluded at the 95 % confidence level.},
doi = {10.1140/epjc/s10052-014-3109-7},
journal = {European Physical Journal. C, Particles and Fields},
number = 10,
volume = 74,
place = {United States},
year = {Wed Oct 29 00:00:00 EDT 2014},
month = {Wed Oct 29 00:00:00 EDT 2014}
}

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