Perspectives on EPIC Physics

An electron-proton/ion polarized beam collider (EPIC) with high luminosity and center-of-mass energy $\sqrt s = 25$ GeV would be a valuable facility for fundamental studies of proton and nuclear structure and tests of quantum chromodynamics, I review a sample of prospective EPIC topics, particularly semi-exclusive reactions, studies of the proton fragmentation region, heavy quark electroproduction, and a new probe of odderon/pomeron interference.Comment: Talk presented at EPIC'99 Workshop, Indiana University, April 199

Novel QCD Effects in the Production and Decay of Quarkonium

There are many outstanding discrepancies comparing the predictions of perturbative QCD and measurements of the rate of production and decay of heavy quark systems. The problems include the $J/\psi \to \rho \pi$ puzzle, leading charmed particle effects, the anomalous behavior of the heavy quark sea components of structure functions, anomalous nuclear target effects, and the large rates observed for single and double quarkonium production at large $x_F$ and large $p_T$. I argue that these anomalies may be associated with nonperturbative effects in the higher Fock structure of hadron wavefunctions.Comment: Latex, 12 page

Novel Aspects of QCD in Leptoproduction

I review several topics in electroproduction which test fundamental aspects of QCD. These include the role of final-state interactions in producing diffractive leptoproduction processes, the shadowing of nuclear structure functions, and target-spin asymmetries. The antishadowing of nuclear structure functions is shown to be quark-flavor specific, suggesting that some part of the anomalous NuTeV result for $\sin^2\theta_W$ could be due to the non-universality of nuclear antishadowing for charged and neutral currents. I also discuss the physics of the heavy-quark sea, hidden color in nuclear wavefunctions, and evidence for color transparency for nuclear processes. The AdS/CFT correspondence connecting superstring theory to superconformal gauge theory has important implications for hadron phenomenology in the conformal limit, including an all-orders demonstration of counting rules for hard exclusive processes, as well as determining essential aspects of hadronic light-front wavefunctions.Comment: Presented at the conference, Electron-Nucleus Scattering VIII, Marciana Marina, Isola d'Elba, June 21-25, 200

Two-Photon Processes at Intermediate Energies

Exclusive hadron production processes in photon-photon collisions provide important tests of QCD at the amplitude level, particularly as measures of hadron distribution amplitudes and skewed parton distributions. The determination of the shape and normalization of the distribution amplitudes has become particularly important in view of their importance in the analysis of exclusive semi-leptonic and two-body hadronic B-decays. Interesting two-photon physics, including doubly-tagged $\gamma^* \gamma^*$ reactions, will be accessible at low energy, high luminosity $e^+ e^-$ colliders, including measurements of channels important in the light-by-light contribution to the muon $g$--2 and the study of the transition between threshold production controlled by low-energy effective chiral theories and the domain where leading-twist perturbative QCD becomes applicable. The threshold regime of hadron production in photon-photon and $e^+ e^-$ annihilation, where hadrons are formed at small relative velocity, is particularly interesting as a test of low energy theorems, soliton models, and new types of resonance production. Such studies will be particularly valuable in double-tagged reactions where polarization correlations, as well as the photon virtuality dependence, can be studied.Comment: Paper PEP-N W01 presented at the e+ e- Physics at Intermdiate Energies Workshop, SLAC, April 30-May 2, 2001. References adde