CMS-PAS-HIG-14-040

CMS-PAS-HIG-14-040
Search for lepton-flavour-violating decays of the Higgs boson to $\mathrm{ e \tau }$ and $\mathrm{ e \mu }$ at $\sqrt{s} =$ 8 TeV
CMS Collaboration
August 2015

Abstract: A direct search for lepton-flavour-violating decays of a Higgs boson ( $m_{\mathrm{H}} =$ 125 GeV) is described. The search is performed for the $\mathrm{H} \rightarrow \mathrm{e} \tau_{\mu}$ , $\textrm{H} \rightarrow \mathrm{e} \tau_{h}$ , and $\mathrm{H} \rightarrow \mathrm{e} \mu$ decays, where $\tau_{h}$ and $\tau_{\mu}$ are taus reconstructed in the hadronic and muonic decay channels, respectively. The data sample used in the search corresponds to an integrated luminosity of 19.7 fb $^{-1}$ collected in pp collisions at $\sqrt{s}=$ 8 TeV with the CMS experiment at the CERN LHC. No evidence is found for lepton-flavour-violating decays in either final state. For the $\mathrm{H} \rightarrow \mathrm{e} \tau_{\mu}$ and $\mathrm{H} \rightarrow \mathrm{e} \tau_{h}$ channels, the sensitivity of the search is an order of magnitude better than the existing indirect limits. A constraint of $\mathcal{B}(\mathrm{H} \rightarrow \mathrm{e} \tau )<$ 0.70% at 95% confidence level is set. We also set a limit on the branching ratio of $\mathcal{B}(\mathrm{H} \rightarrow \mathrm{e} \mu) <$ 0.036% at 95% confidence level. The limits on $\mathcal{B}(\mathrm{H} \rightarrow \mathrm{e} \tau )$ and $\mathcal{B}(\mathrm{H} \rightarrow \mathrm{e} \mu)$ are subsequently used to constrain the $\|Y_{\mathrm{e}\tau}\|$ and $\|Y_{\mathrm{e}\mu}\|$ Yukawa couplings.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, PLB 763C (2016) 472. The superseded preliminary plots can be found here.

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