(d)over-bar-(u)over-bar asymmetry and semi-inclusive production of pions in deep inelastic scattering - art. no. 114005

We investigate ambiguities in the extraction of the (d) over bar-(u) over b ar asymmetry from semi-inclusive production of pions in deep inelastic scat tering. The role of several effects beyond the quark-parton model that lead to N-p(pi+) not equalN(n)(pi+) and N-p(pi-) not equalN(n)(pi-) and may the refore cloud such an extraction is studied. The results are discussed in th e context of the recent HERMES data. We find that the interaction of the re solved photon with the nucleon significantly modifies the observed (d) over bar-(u) over bar asymmetry. The exclusive elastic production of rho mesons plays a similar role for the large-z data sample. Our estimate shows a rat her small effect of the spectator mechanism. Nuclear effects in the deutero n also look potentially important but are difficult to estimate quantitativ ely. Throughout the paper we make in addition several general remarks conce rning semi-inclusive and exclusive production of mesons.