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


CMS Collaboration; Khachatryan, V; Sirunyan, A M; Tumasyan, A; Amsler, C; Canelli, F; Chiochia, V; De Cosa, A; Hinzmann, A; Hreus, T; Kilminster, B; Lange, C; Ngadiuba, J; Pinna, D; Robmann, P; Ronga, F J; Taroni, S; Yang, Y; et al (2015). Search for lepton-flavour-violating decays of the Higgs boson. Physics Letters B, 749:337-362.

Abstract

The first direct search for lepton-flavour-violating decays of the recently discovered Higgs boson (H) is described. The search is performed in the $H \to \mu \tau_{e}$ and $H \to \mu \tau_{h}$ 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 $\sqrt{s} = 8 TeV$ with the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 19.7 inverse femtobarns. 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 $B(H \to \mu \tau) = (0.84 +0.39 -0.37)%$. A constraint on the branching fraction, $B(H \to \mu \tau) < 1.51%$ at 95% confidence level is set. This limit is subsequently used to constrain the mu-tau Yukawa couplings to be less than 3.6E-3.

Abstract

The first direct search for lepton-flavour-violating decays of the recently discovered Higgs boson (H) is described. The search is performed in the $H \to \mu \tau_{e}$ and $H \to \mu \tau_{h}$ 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 $\sqrt{s} = 8 TeV$ with the CMS experiment at the CERN LHC and corresponds to an integrated luminosity of 19.7 inverse femtobarns. 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 $B(H \to \mu \tau) = (0.84 +0.39 -0.37)%$. A constraint on the branching fraction, $B(H \to \mu \tau) < 1.51%$ at 95% confidence level is set. This limit is subsequently used to constrain the mu-tau Yukawa couplings to be less than 3.6E-3.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Physics Institute
Dewey Decimal Classification:530 Physics
Language:English
Date:25 February 2015
Deposited On:18 Feb 2016 10:43
Last Modified:14 Feb 2018 11:07
Publisher:Elsevier
ISSN:0370-2693
OA Status:Gold
Free access at:Publisher DOI. An embargo period may apply.
Publisher DOI:https://doi.org/10.1016/j.physletb.2015.07.053
Other Identification Number:arXiv:1502.07400v2

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