πNtransition distribution amplitudes: Their symmetries and constraints from chiral dynamics
B. Pire, K. Semenov-Tian-Shansky, L. Szymanowski
2011
Physical Review D
Baryon to meson transition distribution amplitudes (TDAs) extend the concept of generalized parton distributions. Baryon to meson TDAs appear as building blocks in the collinear factorized description of amplitudes for a class of hard exclusive reactions, prominent examples of which being hard exclusive meson electroproduction off a nucleon in the backward region and baryon-antibaryon annihilation into a meson and a lepton pair. We study the general properties of these objects following from
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... underlying symmetries of QCD. In particular, the Lorentz symmetry results in the polynomiality property of the Mellin moments in longitudinal momentum fractions. We present a detailed account of the isotopic and permutation symmetry properties of nucleon to pion (\pi N) TDAs. This restricts the number of independent leading twist \pi N TDAs to eight functions, providing description of all isotopic channels. Using chiral symmetry and the crossing relation between \pi N TDAs and \pi N generalized distribution amplitudes we establish soft pion theorems for \pi N TDAs, which determine the magnitude of \pi N TDAs. Finally, we build a simple resonance exchange model for \pi N TDAs considering N and \Delta(1232) exchange contributions into the isospin-1/2 and isospin-3/2 \pi N TDAs.
doi:10.1103/physrevd.84.074014
fatcat:2slj6iak6zgndhxuineh6xrjvu