Hadron Substructure Probed with Hadron Beams

In this talk, I focus on the quark-gluon structure of hadrons probed using high-energy hadron beams. I start with a brief review on recent major achievements in measuring parton distributions of the nucleon, pion, and kaon, with hadron facilities at CERN and FNAL. Then I discuss a number of outstanding questions and interesting physics issues in the field, and point out their intellectual impact on nuclear physics as a whole. While advocating a continuing exploitation of hadron beams at CERN and FNAL, I strongly emphasize the role of a polarized RHIC, where a major nuclear physics program on the structure of hadrons can thrive. Typeset using REVTEX This work is supported in part by funds provided by the U.S. Department of Energy (D.O.E.) under cooperative agreement #DF-FC02-94ER40818. Talk presented at the NSAC/DNP town meeting on “Nuclear Physics with Intermediate and High-Energy Hadron Probes,” Argonne, January 29–30, 1995.