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Quark loop contribution to π0 4γ

E. A. Kuraev, V. V. Bytev, Yu. M. Bystritskiy

hep-pharXiv:hep-ph/0311086

Abstract

We find the contribution of constituent quark loop mechanism to the branching ratio B4γ = Γ4γ/Γ4γ 5.45 · 10-16 for the reasonable choice of constituent quark mass m 280 MeV. This result is in agreement with vector-dominance approach result obtained years ago. Thus the main contribution arises from QED mechanism π0 γ(γ*) γ(3γ) including light-light scattering block with electron loop. This contribution was investigated in paper of one of us and gave B4γ 2.6 · 10-11.

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