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

Khachatryan V., Sirunyan A. M. , Tumasyan A., Adam W., Bergauer T., Dragicevic M., ...More

PHYSICS LETTERS B, vol.749, pp.337-362, 2015 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 749
  • Publication Date: 2015
  • Doi Number: 10.1016/j.physletb.2015.07.053
  • Journal Name: PHYSICS LETTERS B
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.337-362
  • Middle East Technical University Affiliated: Yes


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 -> mu tau(e) and H -> mu tau(h) channels, where tau(e) and tau(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 root 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 beta(H -> mu tau) = (0.84(-0.37)(+0.39))%. A constraint on the branching fraction, beta(H -> mu tau) < 1.51% at 95% confidence level is set. This limit is subsequently used to constrain the mu-tau Yukawa couplings to be less than 3.6 x 10(-3). (C) 2015 CERN for the benefit of the CMS Collaboration. Published by Elsevier B.V.