The pion transition form factor and the pion distribution amplitude
Abstract
Recent BaBaR data on the pion transition form factor, whose Q^2 dependence is much steeper then predicted by asymptotic Quantum Chromodynamics (QCD), have caused a renewed interest in its theoretical description. We present here a formalism based on a model independent low energy description and a high energy description based on QCD, which match at a scale Q_0. The high energy description incorporates a flat pion distribution amplitude, phi(x)=1, at the matching scale Q_0 and QCD evolution from Q_0 to Q>Q_0. The flat pion distribution is connected, through soft pion theorems and chiral symmetry, to the pion valance parton distribution at the same low scale Q_0. The procedure leads to a good description of the data, and incorporating additional twist three effects, to an excellent description of the data.
Keywords
Cite
@article{arxiv.1001.3075,
title = {The pion transition form factor and the pion distribution amplitude},
author = {S. Noguera and V. Vento},
journal= {arXiv preprint arXiv:1001.3075},
year = {2010}
}
Comments
11 pages, 5 postscript figures, uses epsfig.sty and 1 appendix