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Measurement of the Ratio of the B0→D*−τ+ντ and B0→D*−μ+νμ Branching Fractions Using Three-Prong τ-Lepton Decays
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The ratio of branching fractions R ( D * − ) ≡ B ( B 0 → D * − τ + ν τ ) / B ( B 0 → D * − μ + ν μ ) is measured using a data sample of proton-proton collisions collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb − 1 . For the first time, R ( D * − ) is determined using the τ -lepton decays with three charged pions in the final state. The B 0 → D * − τ + ν τ yield is normalized to that of the B 0 → D * − π + π − π + mode, providing a measurement of B ( B 0 → D * − τ + ν τ ) / B ( B 0 → D * − π + π − π + ) = 1.97 ± 0.13 ± 0.18 , where the first uncertainty is statistical and the second systematic. The value of B ( B 0 → D * − τ + ν τ ) = ( 1.42 ± 0.094 ± 0.129 ± 0.054 ) % is obtained, where the third uncertainty is due to the limited knowledge of the branching fraction of the normalization mode. Using the well-measured branching fraction of the B 0 → D * − μ + ν μ decay, a value of R ( D * − ) = 0.291 ± 0.019 ± 0.026 ± 0.013 is established, where the third uncertainty is due to the limited knowledge of the branching fractions of the normalization and B 0 → D * − μ + ν μ modes. This measurement is in agreement with the standard model prediction and with previous results.
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ALFONSO ALBERO, Alejandro, et al. Measurement of the Ratio of the B0→D*−τ+ντ and B0→D*−μ+νμ Branching Fractions Using Three-Prong τ-Lepton Decays. Physical Review Letters. 2018. Vol. 120, num. 17, pags. 171802. ISSN 0031-9007. [consulted: 16 of August of 2026]. Available at: https://hdl.handle.net/2445/132497