GENERALIZED VECTOR DOMINANCE AND INELASTIC ELECTRON NUCLEON SCATTERING III : THE SMALL w ’ REGION

The generalized vector dominance model for inelastic electron nucleon scattering is extended to the small W’ region by taking into account the increase of -tmin with cl2 in exclusive electroproduction. (Submitted to Physics Letters. ) * Work supported in part by the U. S. Atomic Energy Commission and the National Science Foundation. ** Permanent address: Deutsches Elektronen Synchrotron, DESY, Hamburg, Germany. In previous two letters 132 we have shown how models based on generalized vector dominance can successfully account for the cross section for inelastic electron-proton scattering at high values of w’ and the neutron-to-proton ratio at low as well as high values of w’, Our predictions so far cannot, however, accommodate the “threshold behavior” near w1 N 1; specifically the models of Refs. 1 and 2 cannot explain why the transverse cross section aT(W, q2) at fixed q2 increases with W as long as W’ is not too large compared to unity, nor can they explain why the v W2 curve goes down to zero as ~1-1 considerably faster than (~‘-1). In this letter we discuss how generalized vector dominance can accommodate these striking features when the kinematical limitations due to t min in exclusive electroproduction processes are taken into consideration. We begin by recalling our predictions for the transverse part of the virtual photon nucleon cross section cT for the two alternative models presented in Ref. 2; for model A $+w2,q2) = &iii, $P+ 21 (l+q2/ini)2 + (Ac+BC/& f CC/&) ’