A Study of J/$\psi$ Production in 260 GeV $\pi^-$ Nucleus Collisions

Abstract

Results are presented on the measurement of J/$\psi$ production in the interactions of 260 Ge V/ c negative pions with a tungsten target. The data sample consists of nearly 80 thousand di-muons from J$\psi$ decays. From the good acceptance properties of the detector, a fairly complete determination of the forward production cross section was achieved. The J/$\psi$ and $\psi$ cross sections are reported as are the differential J/$\psi$ cross sections in $X_F$, $P^{2}_{\tau}$ and the angular variables describing the di-muon decays. The differential cross section in $X_F$ is examined within the framework of the fusion model to extract the gluon structure function of the pion and nucleon. The results agree well with expectations and other measurements. The large $P^2_{\tau}$ cross section is compared with a model which assumes that the fundamental production mechanism is gg - gJ/$\psi$. However, the predicted cross sections are an order of magnitude smaller than the data and fail to match the observed angular distributions.