J/psi production mechanisms from the WA11 experiment

Psi production mechanisms in π-Be interactions at 190 GeV/c are studied in the WA11 open spectrometer (Goliath). The study of associated hadrons gives information on production of charmonium states (qantiq or gg → cantic) and on correlations in multiplicity, electric charge and strangeness. This is particularly interesting for high transverse momentum psis where additional mechanisms are expected (qantiq, qg → psig ; psiq). The shape of the xsub(F) distribution of all psis permits an estimation of the gluon structure function of the pion; for high Psub(T) psis, a comparison is made with models