Observation of Z decays to four leptons with the CMS detector at the LHC
Contribuinte(s) |
Universidade Estadual Paulista (UNESP) |
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Data(s) |
30/09/2013
20/05/2014
30/09/2013
20/05/2014
01/12/2012
|
Resumo |
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) 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. |
Formato |
28 |
Identificador |
http://dx.doi.org/10.1007/JHEP12(2012)034 Journal of High Energy Physics. New York: Springer, n. 12, p. 28, 2012. 1126-6708 http://hdl.handle.net/11449/24772 10.1007/JHEP12(2012)034 WOS:000313123800034 WOS000313123800034.pdf |
Idioma(s) |
eng |
Publicador |
Springer |
Relação |
Journal of High Energy Physics |
Direitos |
openAccess |
Palavras-Chave | #Hadron-Hadron Scattering |
Tipo |
info:eu-repo/semantics/article |