SEARCH FOR THE STANDARD MODEL HIGGS BOSON AT CMS IN THE 4-LEPTON CHANNEL

One of the main targets of the CMS experiment is to search for the Standard Model Higgs boson. The 4-lepton channel (from the Higgs decay h- gt ZZ*- gt 4l, l = e,mu) is one of the most promising. The analysis is based on the identification of two opposite-sign, same-flavor lepton pairs leptons are required to be isolated and to come from the same primary vertex. The Higgs would be statistically revealed by the presence of a resonance peak in the 4-lepton invariant mass distribution.The Higgs mass is a free parameter of the Standard Model, and the 4-lepton channel search is sensitive almost in all mass range. With data collected in up to July 2012 the Higgs has been excluded in a wide region of mass at 95pct of confidence level, while a 3-sigma excess has been observed around 126 GeV.The 4-lepton analysis will be presented, spanning on its most important aspects lepton identification, variables of isolation, impact parameter, kinematics, event selection, background control and statistical analysis of results