Test of lepton flavor universality using 𝐵0→𝐷*−⁢𝜏+⁢𝜈𝜏 decays with hadronic 𝜏 channels

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)⁢¯𝜈
𝜏 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±0.1⁢0+0.11−0.10, 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.