ON MESONIC INTERFERENCE PHENOMENA IN DEEP-INELASTIC SCATTERING

Possible effects of a pi' contribution to lepton deep-inelastic scatte ring (DIS) are analyzed. The exchange of the first radial excitation o f the pion (pi'(0(-))) has been advocated recently to solve the notori ous problem of hard vertex form factors in nucleon-nucleon scattering. The pi'-meson exchange contribution is calculated in addition to the well known pionic (Sullivan) contribution. Interference between pi and pi' contributions and their possible influence on the cut-off mass pa rameter of the pi NN form factor extracted from DIS on the nucleon are examined. It is shown that the orthogonality relation between the pi and pi' wave functions, in conjunction with number and momentum sum ru les, put strong restrictions on the size of the interference effect. T he interference effect between pi and pi' is found to be negligible fo r the nucleon quark distributions and to modify only higher moments of the quark distributions. The interference effects of a pionic contrib ution with other mesons are discussed.