Search for lepton-flavour-violating decays of the Higgs boson

The first direct search for lepton-flavour-violating decays of the recently discovered Higgs boson (H) is described. The search is performed in the H → μ τ e and H → μ τ h channels, where τ e and τ h are tau leptons reconstructed in the electronic and hadronic decay channels, respectively. The data sample used in this search was collected in pp collisions at a centre-of-mass energy of s = 8 TeV with the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 19.7 fb − 1 . The sensitivity of the search is an order of magnitude better than the existing indirect limits. A slight excess of signal events with a significance of 2.4 standard deviations is observed. The p -value of this excess at M H = 125 GeV is 0.010. The best fit branching fraction is B ( H → μ τ ) = ( 0.84 − 0.37 + 0.39 ) % . A constraint on the branching fraction, B ( H → μ τ ) < 1.51 % at 95% confidence level is set. This limit is subsequently used to constrain the μ – τ Yukawa couplings to be less than 3.6 × 10 − 3 .

Search for lepton-flavour-violating decays of the Higgs boson | Litlas