The ratio of branching fractions R(D*) = B(B̄ → D* τ− ν̄τ)/ B(B̄ → D* l− ν̄l), 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) → BB̄ decay is fully reconstructed in hadronic decay modes. The accompanying signal B meson is reconstructed as B̄ → D* τ− ν̄τ using leptonic τ decays. The normalization decay, B̄ → D* l− ν̄l , 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 +0.041−0.039 (stat_ +0.035−0.032 (syst). This result is consistent with the current world average and with Standard Model predictions.
Adachi, I., Adamczyk, K., Aggarwal, L., Ahmed, H., Aihara, H., Akopov, N., et al. (2024). Test of lepton flavor universality with a measurement of R(D*) using hadronic B tagging at the Belle II experiment. PHYSICAL REVIEW D, 110(7), 072020-1-072020-17 [10.1103/physrevd.110.072020].
Test of lepton flavor universality with a measurement of R(D*) using hadronic B tagging at the Belle II experiment
Branchini, P.Membro del Collaboration Group
;Budano, A.Membro del Collaboration Group
;Bussino, S.Membro del Collaboration Group
;Laurenza, M.Membro del Collaboration Group
;Martellini, C.Membro del Collaboration Group
;Martini, A.Membro del Collaboration Group
;
2024-01-01
Abstract
The ratio of branching fractions R(D*) = B(B̄ → D* τ− ν̄τ)/ B(B̄ → D* l− ν̄l), 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) → BB̄ decay is fully reconstructed in hadronic decay modes. The accompanying signal B meson is reconstructed as B̄ → D* τ− ν̄τ using leptonic τ decays. The normalization decay, B̄ → D* l− ν̄l , 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 +0.041−0.039 (stat_ +0.035−0.032 (syst). This result is consistent with the current world average and with Standard Model predictions.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
