Virtual Compton Scattering in the Resonance Region Up to the Deep Inelastic Region at Backward Angles and Momentum Transfer Squared of Q**2=1.0 GeV**2

TL;DR

This study reports the first measurements of virtual Compton scattering at Q²=1 GeV² in the resonance region, revealing resonant structures and Q² independence at high energies, with implications for nucleon structure models.

Contribution

First experimental measurement of virtual Compton scattering in the resonance region at Q²=1 GeV², extending understanding of nucleon structure at higher energies.

Findings

Resonant structures observed in the first and second resonance regions.

Data at high W show Q² independence, consistent with existing real photon data.

Measured ratio of H(e,e'p)gamma to H(e,e'p)pi0 cross sections and compared with models.

Abstract

We have made the first measurements of the virtual Compton scattering process via the e p -> e p gamma exclusive reaction at Q**2 = 1 GeV**2 in the nucleon resonance region. The cross section is obtained at center of mass (CM) backward angle, theta_gamma_gamma*, in a range of total (gamma* p) CM energy W from the proton mass up to W = 1.91 GeV. The data show resonant structures in the first and second resonance regions, and are well reproduced at higher W by the Bethe-Heitler+Born cross section, including t-channel pi0-exchange. At high W, our data, together with existing real photon data, show a striking Q**2 independence. Our measurement of the ratio of H(e,e'p)gamma to H(e,e'p)pi0 cross sections is presented and compared to model predictions.