Adependence ofJψproduction inπ−-nucleus collisions at 530 GeV/c

The $A$ dependence of the cross section for $\frac{J}{\ensuremath{\psi}}$ production was measured in the Feynman-$x$ region $0.1\ensuremath{\le}{x}_{F}\ensuremath{\le}0.8$ with a 530-GeV/c ${\ensuremath{\pi}}^{\ensuremath{-}}$ beam. Thick targets of C, Al, Cu, and Pb were employed. Using the cross-section parametrization $\ensuremath{\sigma}={\ensuremath{\sigma}}_{0}{A}^{\ensuremath{\alpha}}$, we find $\ensuremath{\alpha}=0.85\ifmmode\pm\else\textpm\fi{}0.06$. No statistically significant dependence of $\ensuremath{\alpha}$ on either ${x}_{F}$ or transverse momentum ${p}_{t}$ is observed.