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 e and H h channels, where e and 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 ) = (0.84 +0.39 -0.37 )%. A constraint on the branching fraction, B(H ) < 1.51% at 95% confidence level is set. This limit is subsequently used to constrain the - Yukawa couplings to be less than 3.6 10 -3 .