We investigate the ten independent local form factors relevant to the b-baryon decay Λ b → Λ + − , combining information of lattice QCD and dispersive bounds. We propose a novel parametrization of the form factors in terms of orthonormal polynomials that diagonalizes the form factor contributions to the dispersive bounds. This is a generalization of the unitarity bounds developed for meson-to-meson form factors. In contrast to ad-hoc parametrizations of these form factors, our parametrization provides a degree of control of the form-factor uncertainties at large hadronic recoil. This is of phenomenological interest for theoretical predictions of, e.g., Λ b → Λγ and Λ b → Λ + − decay processes.

is an open-source software for a variety of computational tasks in flavor physics. Its use cases include theory predictions within and beyond the Standard Model of particle physics, Bayesian inference of theory parameters from experimental and theoretical likelihoods, and simulation of pseudo events for a number of signal processes. ensures high-performance computations through a back-end and ease of usability through a front-end. To achieve this flexibility, enables the user to select from a variety of implementations of the relevant decay processes and hadronic matrix elements at run time. In this article, we describe the general structure of the software framework and provide basic examples. Further details and in-depth interactive examples are provided as part of the online documentation.

We present Standard Model predictions for lepton flavour universality ratios of inclusive B → X(c)$$ \ell {\overline{\nu}}_{\ell } $$ ℓ ν ¯ ℓ . For the ℓ = μ, e, these ratios are very close to unity as expected. For the τ mode, we update the SM prediction for the branching ratio including power-corrections in the heavy-quark expansion up to 1/$$ {m}_b^3 $$ m b 3 . These inclusive ratios serve as an important cross-check of the exclusive B → D(*)$$ \ell {\overline{\nu}}_{\ell } $$ ℓ ν ¯ ℓ modes, in which tensions exists between the predictions and measurements in those modes.

The determination of the CKM element Vcb from inclusive semileptonic b → cℓ$$ \overline{\nu} $$ ν ¯ decays has reached a high precision thanks to a combination of theoretical and experimental efforts. Aiming towards even higher precision, we discuss two processes that contaminate the inclusive Vcb determination; the b → u background and the contribution of the tauonic mode: b → c(τ → μν$$ \overline{\nu} $$ ν ¯ )$$ \overline{\nu} $$ ν ¯ . Both of these contributions are dealt with at the experimental side, using Monte-Carlo methods and momentum cuts. However, these contributions can be calculated with high precision within the Heavy-Quark Expansion. In this note, we calculate the theoretical predictions for these two processes. We compare our b → u results qualitatively with generator-level Monte-Carlo data used at Belle and Belle II. Finally, we suggest to change the strategy for the extraction of Vcb by comparing the data on B → Xℓ directly with the theoretical expressions, to which our paper facilitates.

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