No abstract

No abstract

No abstract

We present a new measurement of the Cabibbo-Kobayashi-Maskawa matrix element jV cb j from B 0 → D Ã− l þ ν l decays, reconstructed with the full Belle data set of 711 fb −1 integrated luminosity. Two form factor parametrizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product F ð1Þη EW jV cb j and the decay form factors, where F ð1Þ is the normalization factor and η EW is a small electroweak correction. In the CLN parametrization we find F ð1Þη EW jV cb j ¼ ð35.06 AE 0.15 AE 0.56Þ × 10 −3 , ρ 2 ¼ 1.106 AE 0.031 AE 0.007, R 1 ð1Þ ¼ 1.229 AE 0.028 AE 0.009, R 2 ð1Þ ¼ 0.852 AE 0.021 AE 0.006. For the BGL parametrization we obtain F ð1Þη EW jV cb j ¼ ð34.93 AE 0.23 AE 0.59Þ × 10 −3 , which is consistent with the world average when correcting for F ð1Þη EW . The branching fraction of B 0 → D Ã− l þ ν l is measured to be BðB 0 → D Ã− l þ ν l Þ ¼ ð4.90 AE 0.02 AE 0.16Þ%. We also present a new test of lepton flavor universality violation in semileptonic B decays, BðB 0 →D Ã− e þ νÞ BðB 0 →D Ã− μ þ νÞ ¼ 1.01 AE 0.01 AE 0.03. The errors quoted correspond to the statistical and systematic uncertainties, respectively. This is the most precise measurement of F ð1Þη EW jV cb j and form factors to date and the first experimental study of the BGL form factor parametrization in an experimental measurement.

We present a measurement of angular observables and a test of lepton flavor universality in the B → K * + − decay, where is either e or µ. The analysis is performed on a data sample corresponding to an integrated luminosity of 711 fb −1 containing 772 × 10 6 B B pairs, collected at the Υ(4S) resonance with the Belle detector at the asymmetric-energy e + e − collider KEKB. The result is consistent with Standard Model (SM) expectations, where the largest discrepancy from a SM prediction is observed in the muon modes with a local significance of 2.6σ.