The $V_{cb}$ puzzle: an update


الملخص بالإنكليزية

We discuss the impact of the recent untagged analysis of ${B}^0rightarrow D^{*}lbar{ u}_l$ decays by the Belle Collaboration on the extraction of the CKM element $|V_{cb}|$ and provide updated SM predictions for the $bto ctau u$ observables $R(D^*)$, $P_tau$, and $F_L^{D^*}$. The value of $|V_{cb}|$ that we find is about $2sigma$ 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.

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