Jul 6 – 13, 2022
Bologna, Italy
Europe/Rome timezone

A novel approach to semileptonic heavy-to-light $B$ decays through the Dispersive Matrix method

Jul 8, 2022, 3:04 PM
Room 9 (Indaco)

Room 9 (Indaco)

Parallel Talk Quark and Lepton Flavour Physics Quark and Lepton Flavour Physics


Ludovico Vittorio (Istituto Nazionale di Fisica Nucleare)


Semileptonic heavy-to-light $B$ decays are very intriguing transitions mainly because a long-standing tension affects the inclusive and the exclusive determinations of the CKM matrix element $\vert V_{ub} \vert$. Our goal is to re-examine the $b \to u$ quark transitions through the Dispersive Matrix (DM) approach. The DM method is based on the non-perturbative determination of the dispersive bounds due to unitarity and analyticity and determines in a model-independent way the hadronic Form Factors (FFs) in the full kinematical range, starting from existing Lattice QCD data at large momentum transfer. By comparing the DM bands of the FFs with the experiments, we obtain $\vert V_{ub}\vert = (3.62 \pm 0.47) \cdot 10^{-3}$ from $B \to \pi$ decays and $\vert V_{ub}\vert = (3.77 \pm 0.48) \cdot 10^{-3}$ from $B_s \to K$ processes, which after averaging yield $\vert V_{ub}\vert = (3.69 \pm 0.34) \cdot 10^{-3}$. We also present a new strategy to extract a more precise value of $\vert V_{ub}\vert$ from $B \to \pi$ decays, based on the application of the unitarity bounds directly to experimental data. In this case, we get $\vert V_{ub}\vert = (3.88 \pm 0.32) \cdot 10^{-3}$. After averaging with the result from $B_s \to K$ decays our final esclusive value for $\vert V_{ub} \vert$ is $\vert V_{ub} \vert_{excl} = (3.85 \pm 0.27) \cdot 10^{-3}$. All estimates are compatible with the most recent inclusive value $\vert V_{ub} \vert_{incl} = (4.13 \pm 0.26) \cdot 10^{-3}$ within the $1\sigma$ level. Finally, we address the computation of new fully-theoretical estimates of the LFU observables, the forward-backward asymmetry and the lepton polarization asymmetry for semileptonic $B \to \pi$ and $B_s \to K$ decays.

In-person participation Yes

Primary authors

Guido Martinelli (ROMA1) Silvano Simula (ROMA3) Ludovico Vittorio (Istituto Nazionale di Fisica Nucleare)

Presentation materials