Suppressedψphotoproduction: A test for the charm hypothesis

The prediction of our previous paper about the suppression of the photoproduction of a $c\overline{c}$ vector meson ($c=\mathrm{charmed} \mathrm{quark}$) is compared with recent information on the $\psi$ particle. The theoretical foundations of the argument are closely analyzed. The predicted value $\frac{\sigma (\gamma p\to \psi p)}{\sigma (\gamma p\to \rho p)}\simeq 4.4\times {10}^{-4\mathrm{}}$ [i.e., $\sigma (\gamma p\to \psi p)\simeq 7$ nb] is shown to be very different from what one would expect with the color interpretation of $\psi$. Preliminary experimental data seem to confirm this strong suppression of $\psi$ photoproduction and with it the charm hypothesis (though we cannot rule out the idea that the $\psi$ is, say, an intermediate weak boson).