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 ω electroproduction off the proton, ep → e 0 pω, at central Q 2 values of 1.60, 2.45 GeV 2 , at W ¼ 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 ¼ 2.45 GeV 2 , the observed dominance of σ T over σ L , is qualitatively consistent with the collinear QCD description in the near-backward
Background: Measurements of exclusive meson production are a useful tool in the study of hadronic structure. In particular, one can discern the relevant degrees of freedom at different distance scales through these studies.Purpose: To study the transition between non-perturbative and perturbative Quantum Chromodyanmics as the square of four momentum transfer to the struck proton, −t, is increased.Method: Cross sections for the 1 H(e, e ′ π + )n reaction were measured over the −t range of 0.272 to 2.127 GeV 2 with limited azimuthal coverage at fixed beam energy of 4.709 GeV, Q 2 of 2.4 GeV 2 and W of 2.0 GeV at the Thomas Jefferson National Accelerator Facility (JLab) Hall C. Results:The −t dependence of the measured π + electroproduction cross section generally agrees with prior data from JLab Halls B and C. The data are consistent with a Regge amplitude based theoretical model, but show poor agreement with a Generalized Parton Distribution (GPD) based model. Conclusion:The agreement of cross sections with prior data implies small contribution from the interference terms, and the confirmation of the change in t-slopes between the low and high −t regions previously observed in photoproduction indicates the changing nature of the electroproduction reaction in our kinematic regime.
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