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Free keywords:
Particle decays, Particle interactions, Leptons, Quarks, Flavor symmetries, Hadron colliders
MPINP:
LHCb - Abteilung Hinton
Abstract:
The branching fraction B(B0 →D*−τ+ντ) is measured relative to that of the normalization mode B0 → D*−π+π−π+ using hadronic τ+ → π+π−π+(π0)ντ decays in proton-proton collision data at a center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 2 fb−1. The measured ratio is B(B0 → D*−τ+ντ)/B(B0 → D*−π+π−π+) = 1.70±0.10−0.10+0.11, where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the B0 → D*−π+π−π+ and B0 → D*−μ+νμ modes, the lepton universality test R(D*−) ≡ B(B0 → D*−τ+ντ)/B(B0 → D*−μ+νμ) is calculated, R(D*−)=0.247±0.015±0.015±0.012, where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements.