Abstract
We show that using renormalization-group summation to generate the QCD radiative corrections to the transition form factor, calculated with light-cone sum rules (LCSR), renders the strong coupling free of Landau singularities while preserving the QCD form-factor asymptotics. This enables a reliable applicability of the LCSR method to momenta well below . This way, one can use the new preliminary BESIII data with unprecedented accuracy below to fine tune the prefactor of the twist-six contribution. Using a combined fit to all available data below , we are able to determine all nonperturbative scale parameters and a few Gegenbauer coefficients entering the calculation of the form factor. Employing these ingredients, we determine a pion distribution amplitude with conformal coefficients that agree at the level with the data for and fulfill at the same time the lattice constraints on at together with the constraints from QCD sum rules with nonlocal condensates. The form-factor prediction calculated herewith reproduces the data below significantly better than analogous predictions based on a fixed-order power-series expansion in the strong coupling constant.
- Received 18 February 2021
- Accepted 12 April 2021
DOI:https://doi.org/10.1103/PhysRevD.103.096003
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.
Published by the American Physical Society