Pion Production by Inelastic Scattering of Electrons in Hydrogen

The ratios of the yield of electron-induced to photon-induced pion processes have been measured at an incident energy of 600 Mev. Measurements have been made at energies of 60 and 170 Mev for positive pions. The result is expressed in terms of "the equivalent radiation length" $X_e$ defined so that the pion yield due to direct electron production is equal to the pion yield due to photons produced by electrons in a radiator of $X_e$ radiation lengths. The results are $X_e=0.0191\mathrm{}\pm 0.0011$ for 60-Mev pions and $X_e=0.0178\mathrm{}\pm 0.0023$ for 170-Mev pions. At the lower pion energy the value is somewhat lower than the theoretical value if equal transverse and longitudinal interactions are assumed. If the contribution from the longitudinal matrix element is taken to be small or if the electron contribution from large angles of electron scattering is suppressed, then the value can be fitted. The value at 170 Mev is in agreement with predominantly magnetic-dipole absorption corresponding to the enhanced $P_{\frac{3}{2},\frac{3}{2}}$ state of the final pion-nucleon system.