Measurement of separated structure functions in the p(e,e′p)π0 reaction at threshold and chiral perturbation theory

The reaction p(e,e'p)pi(0) has been studied very close to threshold Delta W less than or equal to 4 MeV and at 4-momentum transfer Q(2) = 0.1 (GeV/c)(2). The scattered electron and the kinematically focused recoil proton were detected in coincidence using the 3-magnetic spectrometer setup at the Mainz Microtron MAMI. The transverse and longitudinal as well as the longitudinal-transverse and the transverse-transverse interference structure functions have been determined. From the data the s-wave multipoles E0+ and L0+ have been extracted. The experimental results are compared to recent calculations in chiral perturbation theory.