The origins of quark-hadron duality: How does the square of the sum become the sum of the squares?

Bloom-Gilman duality demonstrates empirically that the electroproduction of $N^*$'s at low momentum transfers averages smoothly around the scaling curve measured at large momentum transfers. The latter is proportional to the sum of the squares of the constituent charges whereas the former involves the coherent excitation of resonances and is driven by the square of summed constituent charges. We determine the minimal necessary conditions for this equality to be realised so that duality can occur and consider the implications for a range of processes that may be studied soon at CEBAF.Comment: 9 page

Resonance production in central pp collisions at the CERN Omega Spectrometer

A study of resonance production in central pp collisions is presented as a function of several kinematical variables. In particular the difference in the transverse momentum (dPT) of the exchanged particles shows that undisputed qqbar mesons are suppressed at small dPT whereas glueball candidates are enhanced and in addition, the azimuthal angle phi gives information on the nature of the Pomeron.Comment: 14 pages, Latex, 5 Figure

On baryon-antibaryon coupling to two photons

We discuss recent claims that $p\bar{p} \to \gamma \gamma$ may be described by a generalized parton picture. We propose that quark-hadron duality provides a justification for the effective dominance of the "handbag" diagram assumed in recent literature, and that handbag diagrams may dominate phenomena in kinematic regions far more extensive than that might be expected from pQCD alone.Comment: 11 pages, 2 eps figures, minor modifications made, version to appear on Phys. Lett.

Evidence that the Pomeron transforms as a non-conserved vector current

The detailed dependences of central meson production on the azimuthal angle phi, t and the meson J^P are shown to be consistent with the hypothesis that the soft Pomeron transforms as a non-conserved vector current. Further tests are proposed. This opens the way for a quantitative description of q-qbar and glueball production in p p -> p M p.Comment: 12 pages, latex, 4 figure

Gluonic charmonium resonances at BaBar and Belle?

We confront predictions for hybrid charmonium and other gluonic excitations in the charm region with recently observed structures in the mass range above 3 GeV. The Y(4260), if resonant, is found to agree with expectations for hybrid charmonium. The possibility that other gluonic excitations may be influencing the data in this region is discussed.Comment: 13 pages, LaTe

New effects observed in central production by experiment WA102 at the CERN Omega Spectrometer

A partial wave analysis of the centrally produced KK and pipi systems shows that the fJ(1710) has J = 0. In addition, a study of central meson production as a function of the difference in transverse momentum (dPT) of the exchanged particles shows that undisputed qqbar mesons are suppressed at small dPT whereas the glueball candidates are enhanced and that the production cross section for different resonances depends strongly on the azimuthal angle between the two outgoing protons.Comment: 5 pages, Latex, 3 Figures to appear in the proceeding of PANIC 99, Uppsala, Sweden, June 199

The End of the Constituent Quark Model?

In this conference summary talk at Hadron03, questions and challenges for Hadron physics of light flavours are outlined. Precision data and recent discoveries are at last exposing the limitations of the naive constituent quark model and also giving hints as to its extension into a more mature description of hadrons. These notes also pay special attention to the positive strangeness baryon $\Theta^+(1540)$ and include a pedagogic discussion of wavefunctions in the pentaquark picture, their relation with the Skyrme model and related issues of phenomenology.Comment: Conference Summary Talk Hadron 0

Puzzles in Cabibbo-Suppressed Charm Decays

We identify two Cabibbo suppressed $D^+$ decay modes with anomalously high branching ratios which are not simply explained by any model. All standard model diagrams that can contribute to these decays are related by symmetries to diagrams for other decays that do not show any such enhancement. If these high branching ratios are confirmed by more precise experiments, they may require new physics to explain them. Anomalies in $D_s$ decays and tests for possible violation of G-parity are discussed.Comment: 12 pages, additional clarification at eq. (13), correction of error in eq. (18) and subsequent discussio

Exact Description of Rotational Waves in an Elastic Solid

Conventional descriptions of transverse waves in an elastic solid are limited by an assumption of infinitesimally small gradients of rotation. By assuming a linear response to variations in orientation, we derive an exact description of a restricted class of rotational waves in an ideal isotropic elastic solid. The result is a nonlinear equation expressed in terms of Dirac bispinors. This result provides a simple classical interpretation of relativistic quantum mechanical dynamics. We construct a Lagrangian of the form L=-E+U+K=0, where E is the total energy, U is the potential energy, and K is the kinetic energy.Comment: 9 pages; Added references in revisio