2014/09/30 by I. Sentitemsu Imsong, Alexander Khodjamirian, Thomas Mannel +1 · 1 citation
Mathematics · Physics and Astronomy · #Extrapolation #Form factor (electronics) #High-Energy Particle Collisions Research #Lattice QCD #Light cone #Mathematical analysis #Mathematics #Momentum (technical analysis) #Momentum transfer #Normalization (sociology) #Parametrization (atmospheric modeling) #Particle physics #Particle physics theoretical and experimental studies #Perturbative QCD #Physics #Quantum Chromodynamics and Particle Interactions #Quantum chromodynamics #Quantum mechanics #Quark #Radiative transfer #Scattering #Sum rule in quantum mechanics #Unitarity #hep-ex #hep-ph
paper · pdf · doi:10.1007/jhep02(2015)126
published as JHEP02(2015)126 · 26 pages, 4 figures; v2: as published (reference and zoomed plot added, conclusions and numerics unchanged)
openalex publication_date 2015/02/01 · arxiv created 2015/03/05 · arxiv updated 2015/03/06 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/06
We address the problem of extrapolating the vector form factor f + , which is relevant to B → πℓν ℓ decays, from the region of small to the region of large momentum transfer. As input, we use the QCD light-cone sum rule at small momentum transfer. We carry out a comprehensive Bayesian uncertainty analysis and obtain correlated uncertainties for the normalization and shape parameters of the form factor. The z-series parametrization for f + is employed to extrapolate our results to large momentum transfer, and to compare with the lattice QCD results. To test the validity of our extrapolation we use the upper and lower bounds from the unitarity and positivity of the two-point correlator of heavy-light quark currents. This correlator is updated by including the NNLO perturbative term and the NLO correction to the quark condensate contribution. We demonstrate that an additional input including the form factor, its first and second derivative calculated at one value of momentum transfer from the light-cone sum rules, considerably improves the bounds. This only holds when the correlations between the form factor parameters are taken into account. We further combine our results with the latest experimental measurements of B → πℓν ℓ by the BaBar and Belle collaborations, and obtain |V ub | = (3. 32 − 0.22 + 0.26 ) ⋅ 10− 3 from a Bayesian analysis.