Measurement of the Ratio of Branching Fractions B(B¯0 →D∗+τ-ν¯τ)/B(B¯0 →D∗+μ-ν¯μ)

The LHCb Collaboration

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The branching fraction ratio R(D∗)≡B(B¯0→D∗+τ-ν¯τ)/B(B¯0→D∗+μ-ν¯μ) is measured using a sample of proton-proton collision data corresponding to 3.0fb-1 of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ-→μ-ν¯μντ. The semitauonic decay is sensitive to contributions from non-standard-model particles that preferentially couple to the third generation of fermions, in particular, Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate B¯0 decays gives R(D∗)=0.336±0.027(stat)±0.030(syst). This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the standard model.
Original languageEnglish
Article number111803
Number of pages10
JournalPhysical Review Letters
Issue number11
Publication statusPublished - 2015
Externally publishedYes

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