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Source CERN Document Server
Content type Text
File Format PDF
Date Created 2012-07-09
Language English
Subject Domain (in DDC) Natural sciences & mathematics ♦ Physics ♦ Modern physics ♦ Technology ♦ Engineering & allied operations ♦ Applied physics
Subject Keyword Particle Physics - Experiment
Abstract A search for the Higgs boson in the H $\rightarrow$ ZZ four-lepton decay channel, with each Z boson decaying to an electron, a muon, or a tau pair, is reported. The search covers Higgs boson mass hypotheses in the range $110 < m_H < 600$ GeV. The analysis uses pp collision data recorded by the CMS detector at the LHC, corresponding to integrated luminosities of 5.05 ${\rm fb}^{-1}$ at $\sqrt{s}$ = 7 TeV and 5.26 ${\rm fb}^{-1}$ at $\sqrt{s}$ = 8\TeV. The four-lepton invariant-mass distributions for $m_{4\ell}$ and $m_{2\ell 2\tau}$ are found to be consistent with the standard model expectations for background ZZ production for invariant masses above 180 GeV. Upper limits at 95\% confidence level exclude the standard model Higgs boson in the range 131--162 and 172--525 GeV, while the expected exclusion range is 121--570 GeV. An excess of events is observed in the low $m_{4\ell}$ mass range, making the observed limits weaker than expected in the absence of a signal. These events cluster around a mass $m_{4\ell} \simeq 125.5$ GeV, giving rise to a local excess with respect to the background expectation, with a significance of $3.2\sigma$. This result constitutes evidence for a new massive state.
Description Collaboration with: CMS
Learning Resource Type Article
Organization CMS Collaboration