arXiv subjects

Dante Bigi

Publications and source records attributed to Dante Bigi.

5 recordsLinked to original sources

arXiv2025

QED effects in 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 $B \to X_c e ν$ decay. Our calculation includes short-distance electroweak corrections, the complete ${\cal O}(α)$ partonic terms and leading-logarithmic QED effects up to ${\cal O}(Λ^3_{\rm QCD}/m_b^3)$. 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 $B \to X_c e ν$ 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.

hep-ph↗

arXiv2023

Finite $W$ mass corrections to inclusive $B$ decays

We compute the effects of a finite $W$ boson mass on the inclusive $b\rightarrow c \ell ν$ decay rate and the semileptonic moments. To this end we keep terms of $\mathcal{O}\left(q^2/m_W^2 \right)$ when integrating out the $W$ boson in the Weak Effective Theory. In the third hadronic invariant mass moment such corrections reach the $0.5\%$ level but they are smaller than the present-day experimental uncertainties in all observables.

hep-ph↗

arXiv2017

$R(D^*)$, $|V_{cb}|$, 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 $B\to D^{(*)}\ellν$ 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 $R(D^{*})=0.260(8)$.

hep-ph↗

arXiv2017

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

We use recent Belle results on $\bar{B}^0\rightarrow D^{*+}l^-\barν_l$ 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.

hep-ph↗

arXiv2016

Revisiting $B\to D \ell ν$

We re-examine the determination of $|V_{cb}|$ from $B\to D \ell ν$ 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 $B\to D \ell ν$ gives $|V_{cb}|=40.49(97)\ 10^{-3}$ and to $R(D)= 0.299(3)$.

hep-ph↗