Virtual Compton scattering and neutral pion electroproduction in the resonance region up to the deep inelastic region at backward angles

Abstract

We have made the first measurements of the virtual Compton scattering (VCS) process via the H(e, e p)γ exclusive reaction in the nucleon resonance region, at backward angles. Results are presented for the W -dependence at fixed Q 2 = 1 GeV 2 and for the Q 2 dependence at fixed W near 1.5 GeV. The VCS data show resonant structures in the first and second resonance regions. The observed Q 2 dependence is smooth. The measured ratio of H(e, e p)γ to H(e, e p)π 0 cross sections emphasizes the different sensitivity of these two reactions to the various nucleon resonances. Finally, when compared to real Compton scattering (RCS) at high energy and large angles, our VCS data at the highest W (1.8-1.9 GeV) show a striking Q 2 independence, which may suggest a transition to a perturbative scattering mechanism at the quark level.

Hard exclusive pion electroproduction at backward angles with CLAS

“…The approach to scaling in backward electroproduction was also studied in the ep → epγ and ep → epπ 0 reactions at Q 2 = 1 GeV 2 and W 2 < 4 GeV 2 in Ref. [31].…”

Are narrow unflavoured mesons a signature of new physics?

“…The virtual Compton scattering cross-sections were measured by the Hall A Collaboration at JLAB [41]. Fig.…”