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Search for lepton-flavour-violating decays of Higgs-like bosons

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Abstract

A search is presented for a Higgs-like boson with mass in the range 45 to 195 GeV/$c^2$ decaying into a muon and a tau lepton. The dataset consists of proton-proton interactions at a centre-of-mass energy of 8 TeV, collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb$^{-1}$. The tau leptons are reconstructed in both leptonic and hadronic decay channels. An upper limit on the production cross-section multiplied by the branching fraction at 95% confidence level is set and ranges from 22 pb for a boson mass of 45 GeV/$c^2$ to 4 pb for a mass of 195 GeV/$c^2$.

Figures and captions

Invariant-mass distributions for the $\mu ^\pm\tau^\mp$ candidates for the four decay channels (from top to bottom: $\mu \tau_e$ , $\mu \tau_{h{\mu \tau_\mu }}$ {mumu }) and the three selections (from left to right: L-selection, C-selection, H-selection). The distribution of candidates observed (black points) is compared with backgrounds (filled colour, stacked), and with signal hypothesis (cyan). The signal is normalised to $\sqrt{N}$, with $N$ the total number of candidates in the corresponding data histogram.

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Cross-section times branching fraction 95% CL limits for the $ H\!\rightarrow \mu ^\pm \tau ^\mp $ decay as a function of $ m_H$ , from the simultaneous fit.

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Animated gif made out of all figures.

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Tables and captions

Requirements for each decay channel and selection set.

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Expected number of background candidates from each component, total background with uncertainty, and number of observed candidates with statistical uncertainty, from each decay channel and selection set.

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Relative systematic uncertainties (in %) on the normalisation factors in the cross-section calculation. When the uncertainty depends on $ m_H$ a range is indicated.

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Created on 09 December 2018.Citation count from INSPIRE on 09 December 2018.