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.

We report a measurement of the ratios of branching fractions R(D, where denotes an electron or a muon. The results are based on a data sample containing 772 × 10 6 B B events recorded at the Υ(4S) resonance with the Belle detector at the KEKB e + e − collider. The tag-side B meson is reconstructed in a semileptonic decay mode, and the signal-side τ is reconstructed in a purely leptonic decay. The results are R(D) = 0.307 ± 0.037 ± 0.016 and R(D * ) = 0.283 ± 0.018 ± 0.014, where the first uncertainties are statistical and the second are systematic. These results are in agreement with the Standard Model predictions within 0.2 and 1.1 standard deviations, respectively.

Observation of an alternative χ c0 (2P ) candidate in e + e − → J/ψDD We perform a full amplitude analysis of the process e + e − → J/ψDD, where D refers to either D 0 or D + . A new charmoniumlike state X * (3860) that decays to DD is observed with a significance of 6.5σ. Its mass is (3862 +26 −32 +40 −13 ) MeV/c 2 and width is (201 +154 −67 +88 −82 ) MeV. The J P C = 0 ++ hypothesis is favored over the 2 ++ hypothesis at the level of 2.5σ. The analysis is based on the 980 fb −1 data sample collected by the Belle detector at the asymmetric-energy e + e − collider KEKB.