Observation of a new boson with a mass near 125 GeV

Combined results are presented from searches for the standard model (SM) Higgs boson in proton-proton collisions at $\sqrt{s}=7$~and~8~TeV in five decay modes: $\gamma\gamma$, $\mathrm{bb}$, $\tau\tau$, $\mathrm{WW}$, and $\mathrm{ZZ}$. The analysed data correspond to integrated luminosities of up to 5.1~fb$^{-1}$ at 7~TeV and 5.3~fb$^{-1}$ at 8~TeV. The data exclude the existence of a SM Higgs boson in the ranges 110--122.5 and 127--600~GeV at 95\%~confidence level. An excess of events above the expected SM background is observed with a local significance of $4.9 \sigma$ around 125~GeV, which we attribute to the production of a previously unobserved particle. The evidence is strongest in the two final states with the best mass resolution: the two-photon final state and the final state with two pairs of charged leptons (electrons or muons). The combined excess in these channels alone gives a local significance of $5.0 \sigma$. An unconstrained fit to the excesses in these two final states yields a mass of $125.3~\pm 0.4~(\mathrm{stat})~\pm 0.5~(\mathrm{syst})$ GeV. Within the statistical uncertainties, the results obtained in all search channels are consistent with the expectations for a SM Higgs boson. More data are needed to test whether the properties of this new state are indeed those of the SM Higgs boson or whether some differ, implying new physics beyond the standard model.