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The pion transition form factor and the pion distribution amplitude

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	Noguera Puchol, Santiago Perfil; Vento Torres, Vicente
	Aquest document és un/a article, creat/da en: 2010
	Este documento está disponible también en : http://dx.doi.org/10.1140/epja/i2010-11029-6
	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.
	Noguera Puchol, Santiago Vento Torres, Vicente 2010 The pion transition form factor and the pion distribution amplitude European Physical Journal A 46 197 205
	http://dx.doi.org/10.1140/epja/i2010-11029-6