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

Physical Review Letters. 2019. Vol. 123. No. 182501. P. 1–6.

Semenov-Tian-Shansky K., Li W. B., Huber G. M., Blok H. P., Gaskell D., Horn T., Pire B., Szymanowski L., Jefferson Lab Fπ C.

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 → e0pω, at central Q2 values of
1.60, 2.45 GeV2, at W = 2.21 GeV. The results of our pioneering −u≈−umin 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 Q2= 2.45 GeV^2, the observed dominance
of σT over σL, is qualitatively consistent with the collinear QCD description in the near-backward

Keywords: vector mesons, transition distribution amplitudes, векторные мезоны, амплитуды распределения перехода, жесткие эксклюзивные реакции