PT Journal
AU Noguera, S
   Vento, V
TI The pion transition form factor and the pion distribution amplitude
SO European Physical Journal A
JI Eur. Phys. J. A
PY 2010
BP 197
EP 205
VL 46
IS 2
DI 10.1140/epja/i2010-11029-6
LA English
AB 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 description for low photon virtuality and a high photon virtuality description based on QCD, which match at a scale Q(0). The high photon virtuality 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 valence parton distribution at the same low scale Q(0). The procedure leads to a good description of the data, and by incorporating additional twist-three effects, to an excellent description of the data.
ER