Unique Access to u-Channel Physics: Exclusive Backward-Angle Omega Meson Electroproduction

TL;DR

This study presents the first complete separation of electromagnetic structure functions in backward-angle omega meson electroproduction, revealing a backward-angle cross section peak and supporting the TDA framework in QCD.

Contribution

It provides the first detailed analysis of backward-angle omega electroproduction, demonstrating the feasibility of structure function separation and supporting TDA-based QCD descriptions.

Findings

Discovery of a backward-angle cross section peak

Successful separation of L/T/LT/TT structure functions

Qualitative agreement with TDA-based QCD models

Abstract

Backward-angle meson electroproduction above the resonance region, which was previously ignored, is anticipated to offer unique access to the three quark plus sea component of the nucleon wave function. In this letter, we present the first complete separation of the four electromagnetic structure functions above the resonance region in exclusive omega electroproduction off the proton, e + p -> e' + p + omega, at central Q^2 values of 1.60, 2.45 GeV^2 , at W = 2.21 GeV. The results of our pioneering -u ~ -u min study demonstrate the existence of a unanticipated backward-angle cross section peak and the feasibility of full L/T/LT/TT separations in this never explored kinematic territory. At Q^2 =2.45 GeV^2 , the observed dominance of sigma_T over sigma_L, is qualitatively consistent with the collinear QCD description in the near-backward regime, in which the scattering amplitude factorizes into a hard subprocess amplitude and baryon to meson transition distribution amplitudes (TDAs): universal non-perturbative objects only accessible through backward angle kinematics.