# EPS HEP 2015

22-29 July 2015
Europe/Vienna timezone

## Exclusive semileptonic B decays to a D or D* meson and one or two pions

Jul 24, 2015, 10:50 AM
15m
HS21

### HS21

talk Flavour Physics and Fundamental Symmetries

### Speaker

Thomas Lueck (SLAC)

### Description

The experimental knowledge of semileptonic B decays to a D or D* meson with one or more pions is limited. These limitations are relevant to two experimental puzzles: the tension between the values of |Vcb| determined from inclusive and exclusive semileptonic decays, and the gap between the sum of the exclusive semileptonic B decays to charm and the inclusive b -> c l nu rate. The full BABAR data set is used to improve the precision on decays involving D(D*) pi l nu and to observe, for the first time, decays of the type D(D*) pi pi l nu. Fully-reconstructed hadronic B decays are used to tag events and provide good resolution on the discriminant variable U = Emiss - Pmiss. A simultaneous fit to charged and neutral B decays to D(npi) and D*(npi) is used to extract relative branching fractions. In addition to studying these high mass charm final states, the data are used to obtain a precise measurement of the ratio of branching fractions BF(B -> D l nu)/BF(B -> D* l nu).