Evidence for the 125 GeV Higgs Boson Decaying into Taus at the CMS Experiment

A search for a standard model (SM) Higgs boson decaying into a pair of $\tau$ leptons is performed using events recorded by the CMS experiment at the LHC in 2011 and 2012. The dataset corresponds to an integrated luminosity of $4.9\,\mathrm{fb}^{-1}$ at a centre-of-mass energy of $7\,\mathrm{TeV}$ and $19.7\,\mathrm{fb}^{-1}$ at $8\,\mathrm{TeV}$. Each $\tau$ lepton decays hadronically or leptonically to an electron or a muon, leading to six different final states for the $\tau$-lepton pair, all considered in this analysis. An excess of events is observed over the expected background contributions, with a local significance larger than 3 standard deviations for $m_H$ values between $115$ and $130\,\mathrm{TeV}$. The best fit of the observed $H \to \tau \tau$ signal cross section times branching fraction for $m_H = 125 \, \mathrm{GeV}$ is $0.78 \pm 0.27$ times the standard model expectation. These observations constitute evidence for the $125\,\mathrm{GeV}$ Higgs boson decaying into a pair of $\tau$ leptons.