Semi-inclusive production of pions in DIS and $\bar d - \bar u$ asymmetry

Abstract

We discuss the role of some nonpartonic effects which lead to $N_p^{\pi^+} \ne N_n^{\pi^+}$ and $N_p^{\pi^-} \ne N_n^{\pi^-}$ and may therefore modify the conclusionon the $\bar d - \bar u$ asymmetry extracted from semi-inclusive production of pions in DIS. Quantitative estimations for resolved photon and exclusive $\rho^0$ are given as examples. The results are discussed in the context of recent HERMES data.