Phys.Rev.Lett. 88 (2002) 012301 New data are presented on the p(e,e'p)\pi^0 reaction at threshold at a
four-momentum transfer of Q^2=0.05 GeV^2/c^2. The data were taken with the
three-spectrometer ...setup of the A1 Collaboration at the Mainz Microtron MAMI.
The complete center of mass solid angle was covered up to a center of mass
energy of 4 MeV above threshold. Combined with measurements at three different
values of the virtual photon polarization \epsilon, the structure functions
\sigma_T, \sigma_L, \sigma_{TT}, and \sigma_{TL} are determined. The results
are compared with calculations in Heavy Baryon Chiral Perturbation Theory and
with a phenomenological model. The measured cross section is significantly
smaller than both predictions.
New data are presented on the p(e,e'p)\pi^0 reaction at threshold at a four-momentum transfer of Q^2=0.05 GeV^2/c^2. The data were taken with the three-spectrometer setup of the A1 Collaboration at ...the Mainz Microtron MAMI. The complete center of mass solid angle was covered up to a center of mass energy of 4 MeV above threshold. Combined with measurements at three different values of the virtual photon polarization \epsilon, the structure functions \sigma_T, \sigma_L, \sigma_{TT}, and \sigma_{TL} are determined. The results are compared with calculations in Heavy Baryon Chiral Perturbation Theory and with a phenomenological model. The measured cross section is significantly smaller than both predictions.
