A study of pion electroproduction on 12C nucleus

A low-energy pion detection system has been designed and tested for pion energies in the 4.5-17.9 MeV range. The detection system consists of four telescopes, each consisting of three Silicon Surface Barrier Detectors in triple coincidence requirement. Two of the detectors are totally depleted in a transmission mount while the third serves as a stopping detector and is of the partially-depleted type. Aluminum moderators thick enough to reduce the pion energy in the 8 to 12 MeV range down to approximately 7 MeV were placed in front of each telescope. The pion detection system was mounted on top of a 1270 double-focusing spectrometer magnet at the University of Saskatchewan Linear Accelerator Laboratory. With this detector system the double differential cross sections on pion electroproduction via the reaction 12C(e,e'π+)12B were measured as a function of energy and pion emission angle. Negative pions via the reaction 12C(e,e'π+)12N were also observed and the π-/π+ ratio determined for 15 MeV pions as a function of angle for a beam energy E sub(e) = 200 MeV. Isochromats were also obtained for pion energies of 8, 10, 12, and 15 MeV and for beam energies from 168 to 200 MeV. The data are in good agreement with other published experimental results and seem to indicate a predominantly M2 transition from the 4.52 MeV 12B excited state. (auth)