Hadron-Hadron Scattering in the Nonrelativistic Quark Model

In this HADRON2001 contribution we summarize the status of our quark-model calculations of hadron-hadron scattering amplitudes in annihilation-free channels. The predictions are in reasonably good agreement with experimentally known S-wave meson-meson and meson-baryon phase shifts, and there are very recent indications that S-wave πω scattering (extracted from FSIs in b1 decay) may also be similar to our predictions. Finally, novel applications of this formalism to the dissociation cross sections of charmonia on light hadrons (relevant for QGP studies at RHIC) are discussed. HADRON-HADRON SCATTERING Introduction Early models of strong interhadron forces were constructed by analogy with QED Feynman diagrams, and in the important NN problem it was assumed that these forces were dominated by t-channel meson exchange. At large distances, one-pion-exchange can indeed be confirmed in NN high partial waves. However at short distances one must have serious reservations about this type of model, since exchange of a ca. 1 GeV meson in t-channel implies a range of about 0.2 fm. Since this is much smaller than the extent of a typical hadron, the assumption of t-channel meson exchange appears rather dubious (see Maltman and Isgur [1] for a discussion). The success of meson-exchange models may simply be due to the many parameters available for fitting, and less trivially because it may prove difficult to distinguish short-distance QCD processes such as quark interchange from meson exchange, as these involve the same flavor flow. Since QCD is a theory of quarks and gluons, and short-ranged scattering probes hadronic wavefunctions, it may be possible to describe hadron-hadron scattering in terms of explicit quark model wavefunctions and interquark forces taken from QCD and hadron spectroscopy. This approach has a long history in the NN problem, and has been applied to many hadronic reactions with much success and the occasional interesting failure. The technique most often used is the resonating-group method, although other variational or nonperturbative methods have also been applied. In this contribution we discuss our results from much simpler Born-order calculations of scattering amplitudes in the quark model, which are more straightfoward to evaluate and are also in reasonable agreement with experimental S-wave scattering amplitudes.