Measurement of Separated Structure Functions in thep(e,e′p)π0Reaction at Threshold and Chiral Perturbation Theory

Abstract

The reaction $p({e,e}^{\ensuremath{'}}p){\ensuremath{\pi}}^{0}$ has been studied very close to threshold $\ensuremath{\Delta}W\ensuremath{\le}4\mathrm{MeV}$ and at 4-momentum transfer ${Q}^{2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.1(\mathrm{GeV}/c{)}^{2}$. 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 ${E}_{0+}$ and ${L}_{0+}$ have been extracted. The experimental results are compared to recent calculations in chiral perturbation theory.