The $V_{cb}$ puzzle: an update

Abstract

We discuss the impact of the recent untagged analysis of ${B}^0\rightarrow D^{*}l\barν_l$ decays by the Belle Collaboration on the extraction of the CKM element $|V_{cb}|$ and provide updated SM predictions for the $b\to cτν$ observables $R(D^*)$, $P_τ$, and $F_L^{D^*}$. The value of $|V_{cb}|$ that we find is about $2σ$ from the one from inclusive semileptonic $B$ decays, and is very sensitive to the slope of the form factor at zero recoil which should soon become available from lattice calculations.

7 pages, 4 figures. Minor changes, 2 additional figures