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 s√=7 TeV collected by the CMS detector at the Large Hadron Collider. A pronounced resonance peak, with a statistical significance of 9.7 σ, 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→4ℓ)=(4.2+0.9−0.8(stat.)±0.2(syst.))×10−6 and agrees with the standard model prediction of 4.45 × 10−6. The measured cross section times branching fraction is σ(pp→Z)B(Z→4ℓ)=112+23−20(stat.)+7−5(syst.)+3−2(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.

S. Chatrchyan, V. Khachatryan, A. M. Sirunyan, A. Tumasyan, W. Adam, E. Aguilo, et al. (2012). Observation of Z decays to four leptons with the CMS detector at the LHC. JOURNAL OF HIGH ENERGY PHYSICS, 2012, 034-1-034-28 [10.1007/JHEP12(2012)034].

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

BONACORSI, DANIELE;BRAIBANT, SYLVIE;BRIGLIADORI, LUCA;CAPILUPPI, PAOLO;CASTRO, ANDREA;CUFFIANI, MARCO;FANFANI, ALESSANDRA;FASANELLA, DANIELE;GUIDUCCI, LUIGI;MENEGHELLI, MARCO;NAVARRIA, FRANCESCO LUIGI;PRIMAVERA, FEDERICA;ROSSI, ANTONIO MARIA;ROVELLI, TIZIANO;SIROLI, GIAN PIERO;C. Battilana;
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 s√=7 TeV collected by the CMS detector at the Large Hadron Collider. A pronounced resonance peak, with a statistical significance of 9.7 σ, 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→4ℓ)=(4.2+0.9−0.8(stat.)±0.2(syst.))×10−6 and agrees with the standard model prediction of 4.45 × 10−6. The measured cross section times branching fraction is σ(pp→Z)B(Z→4ℓ)=112+23−20(stat.)+7−5(syst.)+3−2(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
S. Chatrchyan, V. Khachatryan, A. M. Sirunyan, A. Tumasyan, W. Adam, E. Aguilo, et al. (2012). Observation of Z decays to four leptons with the CMS detector at the LHC. JOURNAL OF HIGH ENERGY PHYSICS, 2012, 034-1-034-28 [10.1007/JHEP12(2012)034].
S. Chatrchyan;V. Khachatryan;A. M. Sirunyan;A. Tumasyan;W. Adam;E. Aguilo;T. Bergauer;M. Dragicevic;J. Erö;C. Fabjan;M. Friedl;R. Frühwirth;V. M. Ghet...espandi
File in questo prodotto:
Eventuali allegati, non sono esposti

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/145567
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 45
  • ???jsp.display-item.citation.isi??? 42
social impact