# Exclusive semileptonic b -> c decays at Belle

## TL;DR

This paper reports precise measurements of semileptonic B decays at Belle, including CKM matrix elements, form factors, and branching fractions for tau modes, advancing understanding of heavy flavor physics.

## Contribution

It provides the first detailed measurements of |V_{cb}|, form factor parameters, and semi-tauonic decay branching fractions using Belle data, with tests of form factor models.

## Key findings

- Precise |V_{cb}| and form factor parameters measured.
- Branching fractions for B -> D^{(*)} τ ν decays determined.
- Validation of form factor parametrization performed.

## Abstract

We present analyses of exclusive semileptonic b -> c decays based on data samples collected by the Belle detector at the KEK-B e+ e- asymmetric collider. The first topic are precision measurements of the Cabibbo-Kobayashi-Maskawa matrix element |V_{cb}| and the HQET form factor parameters \rho^2, R_1 and R_2 extracted from B^+ -> \bar{D}^{*0} \ell^+ \nu decays using untagged Upsilon(4S) events. Additionally, a test of the form factor parametrization is performed. Secondly, measurements of B -> D^* \tau \nu and B -> D \tau \nu decays are presented, where the accompanying second B meson is tagged and reconstructed. Branching fractions of the semi-tauonic decays are measured.