A test of lepton flavor universality with a measurement of R(D) using hadronic B tagging at the Belle~II experiment

Sumitted to PubDB: 2024-01-11

Category: Physics / performance paper, Visibility: Public

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Authors
Non-Belle II authors The Belle II Collaboration
Date Jan. 5, 2024
Belle II Number BELLE2-PUB-PH-2024-001
Abstract The ratio of branching fractions R(D)=B(BDτντ)/B(BDν), where is an electron or muon, is measured using a Belle~II data sample with an integrated luminosity of 189 fb1 at the SuperKEKB asymmetric-energy e+e collider. Data is collected at the Υ(4S) resonance, and one B meson in the Υ(4S)BB decay is fully reconstructed in hadronic decay modes. The accompanying signal B meson is reconstructed as BDτντ using leptonic τ decays. The normalization decay, BDν produces the same observable final state particles. The ratio of branching fractions is extracted in a simultaneous fit to two signal-discriminating variables in both channels and yields R(D)=0.262 0.039+0.041(stat) 0.032+0.035(syst). This result is consistent with the current world average and with standard model predictions.

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