PION ELECTROPRODUCTION IN THE HE-3(E,E'PI(-3 REACTION AT INTERMEDIATEENERGIES())H)

The differential coincident pion electroproduction cross section in th e He-3(e,e'pi(+))H-3 reaction has been measured with high resolution w ith the three-spectrometer set-up at the Mainz Microtron (MAMI) electr on accelerator. Measurements were performed at the four incident energ ies E-0 = 855, 675, 600, and 555 MeV at fixed four-momentum transfer Q (2) = 0.045 GeV2 with the pions detected in parallel kinematics. This enables a separation of the measured cross section into the transverse and longitudinal structure functions by means of the Rosenbluth metho d. The experimental data are compared to model calculations, in which the elementary pion production amplitude includes the standard Born-am plitudes and also delta and higher resonance terms. Three-body Fadeev wave functions are used and the final state interaction of the outgoin g pion is taken into account. The calculation describes the data only after medium modifications of the delta and of the pion are included. (C) 1997 Elsevier Science B.V.