Nucleon-to-pion transition distribution amplitudes and backward electroproduction of pions

TL;DR

This paper develops a theoretical framework for modeling nucleon-to-pion transition distribution amplitudes (TDAs) and estimates the unpolarized cross section and asymmetries in backward pion electroproduction, relevant for upcoming experiments.

Contribution

It introduces a spectral representation-based model for pi N TDAs using quadruple distributions and provides predictions for experimental observables in backward pion electroproduction.

Findings

Cross section estimates are sizable for high-luminosity experiments.

The model incorporates soft-pion theorem constraints and nucleon exchange contributions.

Predictions include unpolarized cross sections and single spin asymmetries.

Abstract

Baryon to meson transition distribution amplitudes (TDAs), non-diagonal matrix elements of the nonlocal three quark operator between a nucleon and a meson state, extend the concept of generalized parton distributions. These non-perturbative objects which encode the information on three quark correlations inside the nucleon may be accessed experimentally in backward meson electroproduction reactions. We suggest a general framework for modelling nucleon to pion (pi N) TDAs employing the spectral representation for pi N TDAs in terms of quadruple distributions. The factorized Ansatz for quadruple distributions with input from the soft-pion theorem for pi N TDAs is proposed. It is to be complemented with a D-term like contribution from the nucleon exchange in the cross channel. We present our estimates of the unpolarized cross section and of the transverse target single spin asymmetry for backward pion electroproduction within the QCD collinear factorization approach in which the non-perturbative part of the amplitude involves pi N TDAs. The cross section is sizable enough to be studied in high luminosity experiments such as J-lab@12GeV and EIC.