The first observation of the Z boson decaying to four leptons in proton-proton collisions is presented. The analyzed data set corresponds to an integrated luminosity of 5.02 fb(-1) at root s = 7 TeV collected by the CMS detector at the Large Hadron Collider. A pronounced resonance peak, with a statistical significance of 9.7 sigma, is observed in the distribution of the invariant mass of four leptons (electrons and/or muons) with mass and width consistent with expectations for Z boson decays. The branching fraction and cross section reported here are defined by phase space restrictions on the leptons, namely, 80 < m(4l) < 100 GeV, where m(4l) is the invariant mass of the four leptons, and m(ll) > 4 GeV for all pairs of leptons, where m(ll) is the two-lepton invariant mass. The measured branching fraction is B(Z -> 4(l)) = 4.2(-0.8)(+0.9)(stat.) +/- 0.2(syst.)) x 10(-6) and agrees with the standard model prediction of 4.45 x 10(-6). The measured cross section times branching fraction is sigma(pp -> Z) B (Z -> 4l) = 112(-20)(+23)(stat.) +/-(+7)(-5)(syst.)(-2)(+3) (lumi.) fb, also consistent with the standard model prediction of 120 fb. The four-lepton mass peak arising from Z -> 4l decays provides a calibration channel for the Higgs boson search in the H -> ZZ -> 4l decay mode.

Observation of Z decays to four leptons with the CMS detector at the LHC / S., C., V., K., A. M., S., A., T., W., A., E., A., T., B., M., D., J., E., C., F., M., F., R., F., V. M., G., J., H., N., H., J., H., M., J., W., K., V., K., M., K., et al.. - In: JOURNAL OF HIGH ENERGY PHYSICS. - ISSN 1029-8479. - 2012:12(2012). [10.1007/jhep12(2012)034]

Observation of Z decays to four leptons with the CMS detector at the LHC

BARONE, Luciano Maria;DEL RE, Daniele;LONGO, Egidio;MICHELI, FRANCESCO;ORGANTINI, Giovanni;PARAMATTI, Riccardo;RAHATLOU, SHAHRAM;SOFFI, LIVIA;SANTANASTASIO, FRANCESCO;TRACZYK, PIOTR WOJCIECH;
2012

Abstract

The first observation of the Z boson decaying to four leptons in proton-proton collisions is presented. The analyzed data set corresponds to an integrated luminosity of 5.02 fb(-1) at root s = 7 TeV collected by the CMS detector at the Large Hadron Collider. A pronounced resonance peak, with a statistical significance of 9.7 sigma, is observed in the distribution of the invariant mass of four leptons (electrons and/or muons) with mass and width consistent with expectations for Z boson decays. The branching fraction and cross section reported here are defined by phase space restrictions on the leptons, namely, 80 < m(4l) < 100 GeV, where m(4l) is the invariant mass of the four leptons, and m(ll) > 4 GeV for all pairs of leptons, where m(ll) is the two-lepton invariant mass. The measured branching fraction is B(Z -> 4(l)) = 4.2(-0.8)(+0.9)(stat.) +/- 0.2(syst.)) x 10(-6) and agrees with the standard model prediction of 4.45 x 10(-6). The measured cross section times branching fraction is sigma(pp -> Z) B (Z -> 4l) = 112(-20)(+23)(stat.) +/-(+7)(-5)(syst.)(-2)(+3) (lumi.) fb, also consistent with the standard model prediction of 120 fb. The four-lepton mass peak arising from Z -> 4l decays provides a calibration channel for the Higgs boson search in the H -> ZZ -> 4l decay mode.
2012
hadron-hadron scattering
01 Pubblicazione su rivista::01a Articolo in rivista
Observation of Z decays to four leptons with the CMS detector at the LHC / S., C., V., K., A. M., S., A., T., W., A., E., A., T., B., M., D., J., E., C., F., M., F., R., F., V. M., G., J., H., N., H., J., H., M., J., W., K., V., K., M., K., et al.. - In: JOURNAL OF HIGH ENERGY PHYSICS. - ISSN 1029-8479. - 2012:12(2012). [10.1007/jhep12(2012)034]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/530924
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