Interactions on Nuclei

Abstract

I review hard photon initiated processes on nuclei. The space-time development of the DIS reaction as viewed in the target rest frame qualitatively describes the nuclear shadowing of quark and gluon distributions, although it may be difficult to understand the very weak $Q^2$ dependence of the low $x$ data. The current jet hadron energy distribution at large $\nu$ is accurately independent of the target size even at very small energy fractions $z \simeq 0.05$. Color transparency is verified for vector meson $(J/\psi,\ \rho)$ production, but remains enigmatic in quasiexclusive proton knockout processes. I emphasize the importance of understanding short-range correlations in nuclei, as manifested by subthreshold production and cumulative $x>1$ DIS processes.