Search for the Standard Model Higgs boson in the decay channel H->ZZ(*)->4l with 4.8 fb-1 of pp collision data at sqrt(s) = 7 TeV with ATLAS

TL;DR

This paper reports a search for the Standard Model Higgs boson in the four-lepton decay channel using 7 TeV proton-proton collision data from ATLAS, setting exclusion limits across a broad mass range and observing no significant excess.

Contribution

First search to analyze the Higgs boson in the H->ZZ(*)->4l channel with 4.8 fb^-1 of ATLAS data at 7 TeV, providing new exclusion limits and candidate signals.

Findings

Excluded Higgs mass ranges at 95% CL: 134-156, 182-233, 256-265, 268-415 GeV

Observed local excesses at 125, 244, 500 GeV with ~2 sigma significance

No statistically significant Higgs signal after considering look-elsewhere effect

Abstract

This Letter presents a search for the Standard Model Higgs boson in the decay channel H->ZZ(*)->l+l-l'+l'-, where l,l'=e or mu, using proton-proton collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb^-1. The four-lepton mass distribution is compared with Standard Model background expectations to derive upper limits on the cross section of a Standard Model Higgs boson with a mass between 110 GeV and 600 GeV. The mass ranges 134-156 GeV, 182-233 GeV, 256-265 GeV and 268-415 GeV are excluded at the 95% confidence level. The largest upward deviations from the background-only hypothesis are observed for Higgs boson masses of 125, 244 and 500 GeV with local significances of 2.1, 2.2 and 2.1 standard deviations, respectively. Once the look-elsewhere effect is considered, none of these excesses are significant.