Correlations in the hadronization process

Pions cannot be fully described as simple $qbar q$ systems. They have a very small mass and may appear as a kind of Goldstone particles. It is demonstrated how this is expected to give correlations in flavour andp _⊥ in the string model hadronization process. Improved agreement with experimental data is obtained, in particular for η′, η production and π⁺π^? mass correlations.