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What is this thing called pion distribution amplitude? From theory to data

Alexander P. Bakulev·S. V. Mikhailov·N. G. Stefanis
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Abstract

We discuss the status of the pion distribution amplitude (DA) from analyzing the CLEO experimental data in the context of QCD sum-rule techniques and QCD perturbation theory at the NLO accuracy. The constraints extracted this way for the Gegenbauer coefficients a_2 and a_4 exclude Φ_{CZ} at the 4σlevel, while Φ_{asy} is outside the 3σerror ellipse. These data provide strong support for the type of endpoint-suppressed, double-humped pion DA we derived via QCD sum rules with nonlocal condensates and favor a value of the vacuum quark virtuality λ_q^2 \simeq 0.4 GeV^2. This pion DA is in agreement with the E791 data, though these experimental results should be viewed carefully and further confirmation is necessary for a more accurate judging of pion DAs from them.

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Alexander P. Bakulev, S. V. Mikhailov, N. G. Stefanis. 2003-10-22. What is this thing called pion distribution amplitude? From theory to data. https://arxiv.org/abs/hep-ph/0310267

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