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Title: Measurement of the $$\mathrm{ t \bar{t} }$$ production cross section in the $$\mathrm{ e \mu }$$ channel in proton-proton collisions at $$\sqrt{s} =$$ 7 and 8 TeV

Abstract

The inclusive cross section for top quark pair production is measured in proton-proton collisions at √s = 7 and 8 TeV, corresponding to 5.0 and 19.7 fb –1, respectively, with the CMS experiment at the LHC. The cross sections are measured in the electron-muon channel using a binned likelihood fit to multi-differential final state distributions related to identified b quark jets and other jets in the event. The measured cross section values are 173.6 ± 2.1 (stat) +4.5 -4.0 (syst) ± 3.8 (lumi) pb at √s = 7 TeV, and 244.9 ± 1.4 (stat) +6.3 -5.5 (syst) ± 6.4 (lumi) pb at √s = 8 TeV, in good agreement with QCD calculations at next-to-next-to-leading-order accuracy. The ratio of the cross sections measured at 7 and 8 TeV is determined, as well as cross sections in the fiducial regions defined by the acceptance requirements on the two charged leptons in the final state. The cross section results are used to determine the top quark pole mass via the dependence of the theoretically predicted cross section on the mass, giving a best result of 173.8 +1.7 -1.8 GeV. Furthermore, the data at √s = 8 TeV are also used to set limits,more » for two neutralino mass values, on the pair production of supersymmetric top squarks with masses close to the top quark mass.« less

Authors:
 [1]
  1. Yerevan Physics Inst. (YerPhI), Yerevan (Armenia). et al.
Publication Date:
Research Org.:
Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1287381
Report Number(s):
FERMILAB-PUB-16-104-CMS; CMS-TOP-13-004; CERN-EP-2016-044; arXiv:1603.02303
Journal ID: ISSN 1029-8479; 1426692
Grant/Contract Number:
AC02-07CH11359
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of High Energy Physics (Online)
Additional Journal Information:
Journal Name: Journal of High Energy Physics (Online); Journal Volume: 2016; Journal Issue: 8; Journal ID: ISSN 1029-8479
Publisher:
Springer Berlin
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; Hadron-Hadron scattering (experiments); top physics

Citation Formats

Khachatryan, Vardan. Measurement of the $\mathrm{ t \bar{t} }$ production cross section in the $\mathrm{ e \mu }$ channel in proton-proton collisions at $\sqrt{s} =$ 7 and 8 TeV. United States: N. p., 2016. Web. doi:10.1007/JHEP08(2016)029.
Khachatryan, Vardan. Measurement of the $\mathrm{ t \bar{t} }$ production cross section in the $\mathrm{ e \mu }$ channel in proton-proton collisions at $\sqrt{s} =$ 7 and 8 TeV. United States. doi:10.1007/JHEP08(2016)029.
Khachatryan, Vardan. 2016. "Measurement of the $\mathrm{ t \bar{t} }$ production cross section in the $\mathrm{ e \mu }$ channel in proton-proton collisions at $\sqrt{s} =$ 7 and 8 TeV". United States. doi:10.1007/JHEP08(2016)029. https://www.osti.gov/servlets/purl/1287381.
@article{osti_1287381,
title = {Measurement of the $\mathrm{ t \bar{t} }$ production cross section in the $\mathrm{ e \mu }$ channel in proton-proton collisions at $\sqrt{s} =$ 7 and 8 TeV},
author = {Khachatryan, Vardan},
abstractNote = {The inclusive cross section for top quark pair production is measured in proton-proton collisions at √s = 7 and 8 TeV, corresponding to 5.0 and 19.7 fb–1, respectively, with the CMS experiment at the LHC. The cross sections are measured in the electron-muon channel using a binned likelihood fit to multi-differential final state distributions related to identified b quark jets and other jets in the event. The measured cross section values are 173.6 ± 2.1 (stat)+4.5-4.0 (syst) ± 3.8 (lumi) pb at √s = 7 TeV, and 244.9 ± 1.4 (stat)+6.3-5.5 (syst) ± 6.4 (lumi) pb at √s = 8 TeV, in good agreement with QCD calculations at next-to-next-to-leading-order accuracy. The ratio of the cross sections measured at 7 and 8 TeV is determined, as well as cross sections in the fiducial regions defined by the acceptance requirements on the two charged leptons in the final state. The cross section results are used to determine the top quark pole mass via the dependence of the theoretically predicted cross section on the mass, giving a best result of 173.8+1.7-1.8 GeV. Furthermore, the data at √s = 8 TeV are also used to set limits, for two neutralino mass values, on the pair production of supersymmetric top squarks with masses close to the top quark mass.},
doi = {10.1007/JHEP08(2016)029},
journal = {Journal of High Energy Physics (Online)},
number = 8,
volume = 2016,
place = {United States},
year = 2016,
month = 8
}

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  • The top-quark pair production cross section in 7 TeV center-of-mass energy proton–proton collisions is measured using data collected by the CMS detector at the LHC. The measurement uses events with one jet identified as a hadronically decaying τ lepton and at least four additional energetic jets, at least one of which is identified as coming from a b quark. The analyzed data sample corresponds to an integrated luminosity of 3.9 fb -1 recorded by a dedicated multijet plus hadronically decaying τ trigger. A neural network has been developed to separate the top-quark pairs from the W+jets and multijet backgrounds. The measured value ofmore » is consistent with the standard model predictions.« less
  • The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standardmore » model.« less
  • The cross section of top quark-antiquark pair production in proton-proton collisions atmore » $$\sqrt{s} = 13$$ TeV is measured by the CMS experiment at the LHC, using data corresponding to an integrated luminosity of 2.2 inverse femtobarns. The measurement is performed by analyzing events in which the final state includes one electron, one muon, and two or more jets, at least one of which is identified as originating from hadronization of a b quark. Furthermore, the measured cross section is 792 $$\pm$$ 8 (stat) $$\pm$$ 37 (syst) $$\pm$$ 21 (lumi) pb, in agreement with the expectation from the standard model.« less
  • A measurement of the tt¯ production cross section at √s = 13 TeV is presented using proton-proton collisions, corresponding to an integrated luminosity of 2.2 fb –1, collected with the CMS detector at the LHC. Final states with one isolated charged lepton (electron or muon) and at least one jet are selected and categorized according to the accompanying jet multiplicity. From a likelihood fit to the invariant mass distribution of the isolated lepton and a jet identified as coming from the hadronization of a bottom quark, the cross section is measured to be σ tt¯ = 888 ± 2,(stat) +26more » –28(syst)±20(lumi) pb, in agreement with the standard model prediction. In conclusion, using the expected dependence of the cross section on the pole mass of the top quark (m t), the value of m t is found to be 170.6 ± 2.7 GeV.« less
  • A measurement of the cross section for top quark-antiquark (tt¯) pairs produced in association with a photon in proton-proton collisions at √s = 8 TeV is presented. The analysis uses data collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.7 fb 1. The signal is defined as the production of a tt¯ pair in association with a photon having a transverse energy larger than 25 GeV and an absolute pseudorapidity smaller than 1.44. The measurement is performed in the fiducial phase space corresponding to the semileptonic decay chain of the tt¯ pair, and themore » cross section is measured relative to the inclusive tt¯ pair production cross section. The fiducial cross section for associated tt¯ pair and photon production is found to be 127 ±27 (stat+syst) fb per semileptonic final state. In conclusion, the measured value is in agreement with the theoretical prediction.« less