Form Factor of the Photopion Matrix Element at Resonance
Abstract
The inelastic scattering of electrons in hydrogen leading to pion formation has been examined. Measurements were carried out in which a hydrogen target was bombarded by electrons of energy E1 W h secondary electrons of energy E2 being detected by a magnetic analyzer at a fixed angle of 75°. The ene ies E1 and E2 were programed together such that the pions were produced at a constant energy near the peak of the pion-nucleon resonance in the (32, 32) state; at the same time the momentum transfer to the pion-nucleon system was varied. Special procedures were developed to eliminate contributions from competing processes. Approximately three fourths of the observed cross section corresponds to magnetic-dipole absorption of the incident virtual photon; the momentum transfer dependence can be interpreted in terms of a form factor of the difference between the magnetic moments of the neutron and proton. If the electron-scattering radii are assumed for the proton, then the data appear to require an rms radius of the magnetic moment of the neutron of about 1.1×10-13 cm, based on an exponential model; nucleon recoil corrections are still somewhat uncertain.
- Publication:
-
Physical Review
- Pub Date:
- June 1958
- DOI:
- 10.1103/PhysRev.110.1155
- Bibcode:
- 1958PhRv..110.1155P