REGGEON AND PION CONTRIBUTIONS IN SEMIEXCLUSIVE DIFFRACTIVE PROCESSESAT DESY HERA

A detailed analysis of semiexclusive diffractive processes in ep deep- inelastic scattering at DESY HERA, with the diffractive final states i n the forward direction, is presented. The contributions of the sublea ding f(2), omega, a(2), rho Reggeons and the pion exchanges to the dif fractive structure function with the forward proton or neutron are est imated. It is found that the (a(2), rho) Reggeons are entirely respons ible for the forward neutron production at x(P)<10(-3). The pi N produ ction in the forward region is estimated using the Deck mechanism. The significance of this reaction For the processes measured at HERA, esp ecially with the leading neutron, is discussed.