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

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^{'}pω, at central Q^{2} values of 1.60, 2.

First Measurement of Near-Threshold J/ψ Exclusive Photoproduction off the Proton.

We report on the measurement of the γp→J/ψp cross section from E_{γ}=11.8  GeV down to the threshold at 8.2 GeV using a tagged photon beam with the GlueX experiment.

Separated response function ratios in exclusive, forward π(±) electroproduction.

The study of exclusive π(±) electroproduction on the nucleon, including separation of the various structure functions, is of interest for a number of reasons. The ratio RL=σL(π-)/σL(π+) is sensitive to isoscalar contamination to the dominant isovector pion exchange amplitude, which is the basis for the determination of the charged pion form factor from electroproduction data. A change in the value of RT=σT(π-)/σT(π+) from unity at small -t, to 1/4 at large -t, would suggest a transition from coupling to a (virtual) pion to coupling to individual quarks.

3He spin-dependent cross sections and sum rules.

We present a measurement of the spin-dependent cross sections for the 3He over -->(e over -->,e')X reaction in the quasielastic and resonance regions at a four-momentum transfer 0.1< or =Q2< or =0.9 GeV2.

Determination of the pion charge form factor at Q2=1.60 and 2.45 (GeV/c)2.

The 1H(e,e'pi+)n cross section was measured at four-momentum transfers of Q2=1.60 and 2.45 GeV2 at an invariant mass of the photon nucleon system of W=2.