A test of lepton flavor universality with a measurement of $R(D^{*})$ using hadronic $B$ tagging at the Belle II experiment

Résumé fourni par la source

The ratio of branching fractions R(D*)=B(B¯→D*τ-ν¯τ)/B(B¯→D*ℓ-ν¯ℓ), where ℓ is an electron or muon, is measured using a Belle II data sample with an integrated luminosity of 189 fb-1 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 B¯→D*τ-ν¯τ using leptonic τ decays. The normalization decay, B¯→D*ℓ-ν¯ℓ, 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.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.