LEPTO and Polarized SIDIS: the Question of Independent Fragmentation

Hadron production in the LEPTO event generator is modeled as a product of distribution functions and LUND hadronization functions (LHFs) weighted by the hard scattering cross sections. The description of polarized SIDIS within this formalism includes a new nonperturbative input – polarized LHFs. It is shown that this approach does not correspond to the commonly adopted one with the independent fragmentation functions. The purity method used by the HERMES collaboration mixes up the two approaches and ignores the contributions from polarized LHFs. This method cannot be considered a precise tool for the extraction of polarized quark distributions from measured SIDIS asymmetries.