2022/05/19 by G. Martinelli, Guido Martinelli, Manuel Naviglio +6
Engineering · Physics and Astronomy · #FOS: Physical sciences #High Energy Physics - Experiment (hep-ex) #High Energy Physics - Lattice (hep-lat) #High Energy Physics - Phenomenology (hep-ph) #Particle Accelerators and Free-Electron Lasers #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ex #hep-lat #hep-ph
paper · pdf · doi:10.48550/arxiv.2205.09742
Contribution to the 2022 QCD session of the 56th Rencontres de Moriond
arxiv created 2022/05/19 · openalex publication_date 2022/05/19 · arxiv updated 2022/05/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present some applications of the unitarity-based Dispersion Matrix (DM) approach to the extraction of the CKM matrix element |Vcb| from the experimental data on the exclusive B(s) → D(s)(*) ℓ ν_ℓ decays. The DM method allows to achieve a non-perturbative, model-independent determination of the momentum dependence of the semileptonic form factors. Starting from lattice results available at large values of the 4-momentum transfer and implementing non-perturbative unitarity bounds, the behaviour of the form factors in their whole kinematical range is obtained without introducing any explicit parameterization of their momentum dependence. We firstly illustrate the effectiveness of the method by considering the case of the semileptonic B → π decay, which is a good benchmark since the kinematic range is large. Then, we focus on the four exclusive semileptonic B(s) → D(s)(*) ℓ ν_ℓ decays and we extract |Vcb| from the experimental data for each transition. The average over the four channels is |Vcb| = (41.2 ± 0.8) ⋅ 10-3 . We find, for the first time, an exclusive value which is compatible with the latest inclusive determination at 1σ level. We address also the issue of Lepton Flavour Universality by computing pure theoretical estimates of the τ/ℓ ratios of the branching fractions for each channel. In the case of a light spectator quark we obtain R(D^*) = 0.275(8) and R(D) = 0.296(8), which are compatible with the corresponding experimental values within 1.3σ. In the case of a strange spectator quark we obtain R(Ds^*) =0.2497(60) and R(Ds) = 0.298(5).