Measurements of the properties of the Higgs-like boson in the four lepton decay channel with the ATLAS detector using 25 fb−1 of proton-proton collision data

This note presents an update of the search results and property measurements of the observed Higgs-like boson in the decay channel H → ZZ(∗) → l+l−l′+l′−, where l, l′ = e or μ, using proton-proton collision data corresponding to integrated luminosities of 4.6 fb−1 and 20.7 fb−1at √s = 7 TeV and √s = 8 TeV, respectively, recorded with the ATLAS detector at the LHC. A clear excess of events over the background is observed at mH = 124.3 GeV in the combined analysis of the two datasets with a significance of 6.6 standard deviations, corresponding to a background fluctuation probability of 2.7 × 10−11. The mass of the Higgs-like boson is measured to be mH = 124.3+0.6-0.5 (stat)+0.5-0.3 (syst) GeV, and the signal strength (the ratio of the observed cross section to the expected SM cross section) at this mass is found to be μ = 1.7+0.5-0.4. A study of Higgs boson production mechanisms allows a first measurement of couplings with this channel. A spin-parity analysis is performed on the events with reconstructed four-lepton invariant mass m4l satisfying 115 GeV < m4l < 130 GeV. The Higgs-like boson is found to be compatible with the SM expectation of 0+ when compared pair-wise with 0− , 1+ , 1− , 2+ , and 2− . The 0− and 1+ states are excluded at the 97.8% confidence level or higher using CLS in favour of 0+.