Measurements of the properties of the new boson recently observed at a mass near 125 GeV in the CMS experiment are reported. The results are obtained from a comprehensive search for the standard model Higgs boson in the H $\rightarrow$ ZZ decay channel, where both Z's decay to electron, muon, or tau lepton pairs. The search covers Higgs boson mass hypotheses in the range $110 < m_H < 1000$ GeV. The analysis uses pp collision data recorded by the CMS detector at the LHC, corresponding to integrated luminosities of 5.1 ${\rm fb}^{-1}$ at $\sqrt{s} = 7$ TeV and 12.2 ${\rm fb}^{-1}$ at $\sqrt{s}= 8$ TeV. The new boson is observed with a local significance above the expected background of 4.5 standard deviations. The signal strength $\mu$, relative to the expectation for the standard model Higgs boson, is measured to be $\mu = 0.80^{+ 0.35}_{-0.28}$ at 126 GeV. A measurement of its mass gives $126.2 \pm 0.6$ (stat) $\pm 0.2$ (syst)~GeV. The hypothesis $0^+$ of the standard model for the spin $J=0$ and parity $P=+1$ quantum numbers is found to be consistent with the observation. Under the assumption that the observed boson has spin zero the data disfavor the pseudoscalar hypothesis $0^-$ with a $\mathrm{CL_s}$ value of 2.4\%. No other significant excess is found, and upper limits at 95\% confidence level exclude the ranges 113--116 GeV and 129--720 GeV while the expected exclusion range for the standard model Higgs boson is 118--670 GeV.

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