5,109 research outputs found
Perspectives on EPIC Physics
An electron-proton/ion polarized beam collider (EPIC) with high luminosity
and center-of-mass energy 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 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
and large . 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 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 reactions, will be
accessible at low energy, high luminosity colliders, including
measurements of channels important in the light-by-light contribution to the
muon --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 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
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