Coherent p0 electroproduction from the Deuteron
Harald Merkel
Institut für Kernphysik,
Johannes Gutenberg-Universität Mainz
In this talk our recent measurements[1] on coherent threshold pion production
from the Deuteron will be presented. The complete CMS solid angle was
covered from threshold up to 4 MeV above threshold. By measuring at
three different values of the virtual photon polarization, a
transverse-longitudinal separation could be performed.
While the results of photoproduction experiments[2] are in
reasonable agreement with predictions of Chiral Perturbation Theopy[3]
(ChPT), our measurment shows a surprising deviation of one order of
magnitude from calculations in the framework of ChPT[4].
Selected References:
- I. Ewald et al., Phys. Lett. B 499/3-4 (2001) 238-244
- J.C. Bergstrom et al., Phys. Rev. C 57 6 (1998) 3203
- S.R. Beane et al., Nucl. Phys. A618, 381 (1997);
- V. Bernard et al., Phys. Rev. C61, 058201 (2000)