Volume 518 - The 42nd International Symposium on Lattice Field Theory (LATTICE2025) - Parallel Session Quark and lepton flavor physics
Untangling the heavy-flavor mess: status of the Fermilab-MILC calculation of the $B_{(s)}\to D^{(\ast)}_{(s)}\ell\nu$ form factors
A.M. Vaquero Avilés-Casco*, C. DeTar, A.X. El-Khadra, E. Gámiz, S. Gottlieb, W. Jay, H. Jeong, A. Kronfeld and A. Lytle
*: corresponding author
Full text: Not available
Abstract
We present the status of calculations of the form factors of the most relevant heavy-to-heavy and heavy-to-light decay channels.
Using seven $N_f=2+1+1$ HISQ ensembles, with lattice spacings ranging from 0.15 fm down to 0.06 fm, we calculate the form factors of the decays, including correlations among them.
More than half of our ensembles feature physical pion masses, and the heavy quarks are simulated at their physical masses using the
Wilson-clover action with the Fermilab interpretation.

Even though we have recently seen huge qualitative and quantitative leaps in the characterization of heavy-to-heavy decays, these advances have failed to translate into improvements for the inclusive vs exclusive question, or the matter of the Lepton Flavor Universality ratios.
In particular, in the $B\to D^\ast\ell\nu$ channel, the current situation of the lattice-QCD form factors is far from clear.
Further, the latest lattice-QCD results on the heavy-to-light form factors display unexplained tensions that must urgently be resolved.
The work presented here is an attempt to address these issues.
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