The dipole representation of vector meson electroproduction beyond leading twist

TL;DR

This paper connects the computation of vector meson electroproduction impact factors beyond leading twist with the dipole picture, enabling a phenomenological approach to helicity amplitudes in leptoproduction.

Contribution

It extends the dipole model framework to include twist 3 contributions beyond the Wandzura-Wilczek approximation, linking impact factors to dipole scattering amplitudes.

Findings

Impact factor factorizes into wave functions and dipole amplitudes

Beyond Wandzura-Wilczek, the dipole interaction signature persists

Facilitates phenomenological modeling of vector meson leptoproduction

Abstract

We link the recent computation beyond leading twist of the impact factor of the transition gamma*T -> rhoT performed in the light-cone collinear approach, to the dipole picture by expressing the hard part of the process through its Fourier transform in coordinate space. We show that in the Wandzura-Wilczek approximation the impact factor up to twist 3 factorises in the wave function of the photon combined with the distribution amplitudes of the rho-meson and the colour dipole scattering amplitude with the t-channel gluons. We show also that beyond the Wandzura-Wilczek approximation, the hard contribution of the amplitude still exhibits the signature of the interaction of a single colour dipole with the t-channel gluons. This result allows a phenomenological approach of the helicity amplitudes of the leptoproduction of vector meson, by combining our results to a dipole/target scattering amplitude model.