Nucleon to meson transition distribution amplitudes (TDAs), non-diagonal
matrix elements of nonlocal three quark operators between a nucleon and a meson
states, arise within the collinear factorized description of hard exclusive
electroproduction of mesons off nucleons in the backward direction. Below we
address the problem of modelling pion to nucleon TDAs. We suggest a factorized
Ansatz for quadruple distributions with input from the soft pion theorem for pi
N TDAs. In order to satisfy the polynomiality property in its full form the
spectral representation is complemented with a D-term like contribution from
the nucleon exchange in the u-channel of the reaction. We present our estimates
for the backward pion electroproduction unpolarized cross section and its
transverse target single spin asymmetry within our composite model for pi N
TDAs.Comment: 6 pages, 3 figures, proceedings of the XIV Advanced Research Workshop
on High Energy Spin Physics, Dubna, sept.20-24, 2011 (DSPIN-11
