The new Higgs particle in the H->ZZ*->4l searches with the ATLAS detector

This document presents results and measurements of the properties of the newly observed Higgs particle in the decay channel H → ZZ(∗) → l+l−l'+l'−, where l,l' = e or $\mu$. The analysis is based on 4.6fb−1 and 20.7fb−1 of proton-proton collisions at 7TeV and 8TeV, respectively, recorded with the ATLAS detector at the LHC. An excess of events over background is observed at mH = 124.3 GeV with a significance of 6.6 standard deviations. The mass is measured to be $m_H = 124.3^{+0.6}_{-0.5} \mbox{(stat)} ^{+0.5}_{-0.3} \mbox{(syst)}$ GeV and the signal strength at this mass is found to be $\mu =1.7^{+0.5}_{−0.4}$. A spin-parity analysis is also performed: the Higgs-like boson is found to be compatible with the Standard Model (SM) expectation of JP = 0+, when compared pair-wise with 0−, 1+, 1−, 2+ and 2−.