Revisiting B→DℓνB\to D \ell \nu

We re-examine the determination of $|V_{cb}|$ from $B\to D \ell \nu$ in view of recent experimental and theoretical progress, discussing the parameterization of the form factors and studying the role played by the unitarity constraints. Our fit to experimental and lattice results for $B\to D \ell \nu$ gives $|V_{cb}|=40.49(97)\ 10^{-3}$ and to $R(D)= 0.299(3)$.Comment: 19 pages, 2 figures; v2: BCL fits, various clarifications and refs adde

A fresh look at the determination of |V_cb| from B-> D^* l nu

We use recent Belle results on $\bar{B}^0\rightarrow D^{*+}l^-\bar{\nu}_l$ decays to extract the CKM element $|V_{cb}|$ with two different but well-founded parameterizations of the form factors. We show that the CLN and BGL parameterizations lead to quite different results for $|V_{cb}|$ and provide a simple explanation of this unexpected behaviour. A long lasting discrepancy between the inclusive and exclusive determinations of $|V_{cb}|$ may have to be thoroughly reconsidered.Comment: 6 pages. A few clarifications added. Matches published versio

R(D∗)R(D^*), ∣Vcb∣|V_{cb}|, and the Heavy Quark Symmetry relations between form factors

Stringent relations between the $B^{(*)} \to D^{(*)}$ form factors exist in the heavy quark limit and the leading symmetry breaking corrections are known. We reconsider their uncertainty and role in the analysis of recent Belle data for $B\to D^{(*)}\ell\nu$ with model-independent parametrizations and in the related prediction of $R(D^{(*)})$. We find $|V_{cb}|=41.5(1.3) \ 10^{-3}$ and $|V_{cb}|=40.6(^{+1.2}_{-1.3}) \ 10^{-3}$ using input from Light Cone Sum Rules, and $R(D^{*})=0.260(8)$.Comment: 13 pages. Improved discussion of R(D*), P_tau prediction and various explanations adde

QED effects in inclusive semi-leptonic BB decays

We perform a detailed analysis of QED corrections to the total decay width and the electron energy spectrum of the inclusive semi-leptonic $B \to X_c e \nu$ decay. Our calculation includes short-distance electroweak corrections, the complete ${\cal O}(\alpha)$ partonic terms and leading-logarithmic QED effects up to ${\cal O}(\Lambda^3_{\rm QCD}/m_b^3)$. In the case of the branching ratio and the electron energy moments we perform a detailed numerical comparison of our results against those obtained with the Monte Carlo (MC) tool PHOTOS. While the comparison indicates good overall agreement, our computation contains QED effects not included in PHOTOS and should therefore provide a better description of photon radiation to $B \to X_c e \nu$ as measured by the $B$-factories. The calculations performed here represent the first steps in the construction of a fully differential higher-order QED MC generator for inclusive semi-leptonic $B$ decays.Comment: 40 pages, 8 figures and 3 table

Lattice QCD Impact on Determination of the CKM Matrix

We review many lattice QCD calculations that impact the precise determination of the CKM matrix. We focus on decay constants and semileptonic form factors of both light ($\pi$ and K) and heavy-light ($D_{(s)}$ and $B_{(s)}$) mesons. Implication of $\Lambda_b$ form factors will be shown. When combined with experimental results for branching fractions and differential decay rates, the above calculations strongly constrain the first two rows of the CKM matrix. We discuss a long standing difference between $|V_{ub}|$ and $|V_{cb}|$ as determined from exclusive or inclusive decays.Comment: 10 pages, 6 figures, Proceedings of 16th Conference on Flavor Physics and CP Violation (FPCP 2018), July 14-18, 2018, Hyderabad, Indi

QED effects in inclusive semi-leptonic BB decays

We analyse in detail the QED corrections to the total decay width and the moments of the electron energy spectrum of the inclusive semi-leptonic B → X$_{c}$eν decay. Our calculation includes short-distance electroweak corrections, the complete (α) partonic terms and leading-logarithmic QED effects up to $\mathcal{O}\left({\Lambda}_{\textrm{QCD}}^3/{m}_b^3\right)$. A comprehensive numerical comparison of our results against those obtained with the Monte Carlo (MC) tool PHOTOS is presented. While the comparison indicates good overall agreement, our computation contains QED effects not included in PHOTOS and should therefore better describe photon radiation to B → X$_{c}$eν as measured by the B-factories. Our calculations represent the first steps in the construction of a fully differential higher-order QED MC generator for inclusive semi-leptonic B decays.We analyse in detail the QED corrections to the total decay width and the moments of the electron energy spectrum of the inclusive semi-leptonic $B \to X_c e \nu$ decay. Our calculation includes short-distance electroweak corrections, the complete ${\cal O}(\alpha)$ partonic terms and leading-logarithmic QED effects up to ${\cal O}(\Lambda^3_{\rm QCD}/m_b^3)$. A comprehensive numerical comparison of our results against those obtained with the Monte Carlo (MC) tool PHOTOS is presented. While the comparison indicates good overall agreement, our computation contains QED effects not included in PHOTOS and should therefore better describe photon radiation to $B \to X_c e \nu$ as measured by the $B$-factories. Our calculations represent the first steps in the construction of a fully differential higher-order QED MC generator for inclusive semi-leptonic $B$ decays