PoS - Proceedings of Science
Volume 396 - The 38th International Symposium on Lattice Field Theory (LATTICE2021) - Oral presentation
Non-perturbative bounds for $B \to D^{(*)} \ell \nu_\ell$ decays and phenomenological applications
G. Martinelli, S. Simula and L. Vittorio*
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Pre-published on: May 16, 2022
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We show how to extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element $\vert V_{cb} \vert$ from exclusive semileptonic $B \to D^{(*)}$ decays by using the Dispersive Matrix (DM) method. It is a new approach which allows to determine in a full non-perturbative way the hadronic form factors (FFs) in the whole kinematical range, without making any assumption on their dependence on the momentum transfer. We investigate also the issue of Lepton Flavor Universality (LFU) by computing a pure theoretical estimate of the ratio $R(D^{(*)})$. Our approach is applied to the preliminary blinded LQCD computations of the FFs by the FNAL/MILC [1] Collaborations and to the preliminary unblinded ones by the JLQCD [2] Collaboration for the $B \to D^*$ decays to the final ones, computed by FNAL/MILC [3], for the $B \to D$ transitions . Since the FNAL/MILC Collaborations have recently published the final results of their LQCD computations of the FFs [4] for the $B \to D^*$ case, we present also the results of our procedure after its application on these data. We find $ \vert V_{cb} \vert = (41.0 \pm 1.2) \cdot 10^{-3}$ and $\vert V_{cb} \vert = (41.3 \pm 1.7) \cdot 10^{-3}$ from $B \to D$ and $B \to D^*$ decays, respectively. These estimates are consistent within $1\sigma$ with the most recent inclusive determination $\vert V_{cb}\vert_{incl} = (42.16 \pm 0.50) \cdot 10^{-3}$ [5]. Furthermore, we obtain $R(D) = 0.289(8)$ and $R(D^*) = 0.269(8)$, which are both compatible with the latest experimental averages [6] at the $\sim$1.6$\sigma$ level.
DOI: https://doi.org/10.22323/1.396.0365
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