Observation and Measurement of the Higgs-like Boson at 125 GEV in the Two-Photon Decay Channel with the CMS Experiment

We present results for the search for the Standard Model Higgs boson in the twophoton channel using the full 2011+2012 dataset recorded by the CMS experiment at the LHC. The MVA analysis, most sensitive for discovery, observes an excess of events at 125 GeV with a local significance of 3.2σ. The mass of the observed boson is measured to be 125.4±0.5(stat.)±0.6(syst.) GeV. For a Higgs boson mass hypothesis of 125 GeV, the best fit signal strength is $0.78^{+0.28}_{−0.26}$ times the SM Higgs boson cross-section. An upper limit on its natural width is found to be $6.9 GeV/c^2$ at 95% confidence level. We also present results from searches for an additional Higgs boson decaying into two photons, treating the observed resonance as a background process. Cases in which the additional state is SM-like, fermiophobic or gauge-phobic have been considered. In addition, we present a search targeted at discriminating between a single Higgs boson at 125 GeV and two very close-by ones.