A measurement of the cross section for the production of top quark-antiquark pairs ( t(t)over-bar ) in association with a vector boson V (W or Z) in proton-proton collisions at sqrt(s) = 8 TeV is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb^{-1} recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and mu) channels: a same-sign dilepton analysis targeting t(t)over-bar W events, and trilepton and four-lepton analyses designed for t(t)over-bar Z events. In the same-sign dilepton channel, the t(t)over-bar W cross section is measured as σ_{t(t)over-bar W} = 170 +90-80(stat) +/- 70(syst) fb, corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the t(t)over-bar Z cross section, σ_{t(t)over-bar Z} = 200 +80−70(stat) +40−30(syst) fb, is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive t(t)over-bar V process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.

Measurement of top quark-antiquark pair production in association with a W or Z boson in pp collisions at sqrt(s) = 8 TeV / V. Khachatryan, A. M. Sirunyan, A. Tumasyan, W. Adam, T. Bergauer, M. Dragicevic, J. Erö, C. Fabjan, M. Friedl, R. Frühwirth, V. M. Ghete, C. Hartl, N. Hörmann, J. Hrubec, M. Jeitler, W. Kiesenhofer, V. Knünz, M. Krammer, I. Krätschmer, D. Liko, et al.. - In: THE EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6044. - STAMPA. - 74:3060:(2014), pp. 1-26. [10.1140/epjc/s10052-014-3060-7]

Measurement of top quark-antiquark pair production in association with a W or Z boson in pp collisions at sqrt(s) = 8 TeV

CIULLI, VITALIANO;D'ALESSANDRO, RAFFAELLO;FOCARDI, ETTORE;GONZI, SANDRO;GORI, VALENTINA;LENZI, PIERGIULIO;TROPIANO, ANTONIO;
2014

Abstract

A measurement of the cross section for the production of top quark-antiquark pairs ( t(t)over-bar ) in association with a vector boson V (W or Z) in proton-proton collisions at sqrt(s) = 8 TeV is presented. The results are based on a dataset corresponding to an integrated luminosity of 19.5 fb^{-1} recorded with the CMS detector at the LHC. The measurement is performed in three leptonic (e and mu) channels: a same-sign dilepton analysis targeting t(t)over-bar W events, and trilepton and four-lepton analyses designed for t(t)over-bar Z events. In the same-sign dilepton channel, the t(t)over-bar W cross section is measured as σ_{t(t)over-bar W} = 170 +90-80(stat) +/- 70(syst) fb, corresponding to a significance of 1.6 standard deviations over the background-only hypothesis. Combining the trilepton and four-lepton channels, a direct measurement of the t(t)over-bar Z cross section, σ_{t(t)over-bar Z} = 200 +80−70(stat) +40−30(syst) fb, is obtained with a significance of 3.1 standard deviations. The measured cross sections are compatible with standard model predictions within their experimental uncertainties. The inclusive t(t)over-bar V process is observed with a significance of 3.7 standard deviations from the combination of all three leptonic channels.
2014
74:3060
1
26
V. Khachatryan; A. M. Sirunyan; A. Tumasyan; W. Adam; T. Bergauer; M. Dragicevic; J. Erö; C. Fabjan; M. Friedl; R. Frühwirth; V. M. Ghete; C. Hartl; N...espandi
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Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/899343
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