# A fresh look at the determination of |V_cb| from B-> D^* l nu

## TL;DR

This paper re-examines the extraction of the CKM matrix element |V_cb| from B->D* l nu decays using recent Belle data, highlighting discrepancies between different form factor parameterizations and their implications for the inclusive-exclusive |V_cb| tension.

## Contribution

It compares the CLN and BGL parameterizations for form factors in |V_cb| extraction, revealing significant differences and prompting a reassessment of the longstanding discrepancy.

## Key findings

- CLN and BGL parameterizations yield different |V_cb| values.
- The discrepancy may impact the inclusive vs. exclusive |V_cb| determination.
- Provides insight into form factor modeling in semileptonic B decays.

## Abstract

We use recent Belle results on $\bar{B}^0\rightarrow D^{*+}l^-\bar{\nu}_l$ decays to extract the CKM element $|V_{cb}|$ with two different but well-founded parameterizations of the form factors. We show that the CLN and BGL parameterizations lead to quite different results for $|V_{cb}|$ and provide a simple explanation of this unexpected behaviour. A long lasting discrepancy between the inclusive and exclusive determinations of $|V_{cb}|$ may have to be thoroughly reconsidered.