J.W. Alcock

The two-pion exchange contribution to meson-nucleon scattering in the low and intermediate energy region

Abstract The pion-nucleon and kaon-nucleon partial wave amplitudes with large angular momenta are estimated using the Mandelstam representation.

A unitary calculation of particle exchange in KN scattering and ‘composite’ resonances

The Blankenbecler-Sugar equation is solved for kaon-nucleon elastic scattering; the driving term is taken as a sum of Regge exchange amplitudes. The coupling constants of the exchanges, as previously determined from high partial-wave analyses, give an essentially zero-parameter investigation. Of the ten predicted partial-wave amplitudes nine are in agreement with experiment, in sign and magnitude, over the whole elastic region. From our calculation it is not clear whether or not the P01 wave is resonant; such a resonance (Z0∗) is a distinct possibility. However, its size and sharpness are sensitive to small charges in our parameters. With exact SU(3) symmetry the Z0∗ must belong to a 10 multiplet. It is tentatively suggested that the N(1470) may be a partner to the Z0∗, having large components of this multiplet.

A String-Breaking Model of Heavy Meson Decays

AbstractWithin QCD, heavy quarkonia are viewed as a quark antiquark pair bound by a narrow chromoelectric flux tube. This flux can create light quark antiquark pairs accounting for the decay into mesons with heavy quantum numbers. This model is shown to be as consistent with current data on charmonium decays intoD-meson pairs and upsilon decay to

A quark-antiquark potential from a superconducting model of confinement

B\bar B

Particle exchange in KN scattering

, as is the physically less appealing3P0 model.

Electroproduction in the quark model

Abstract The ππ exchange contribution at large impact parameter in high-energy elastic proton-proton scattering is evaluated from t -channel unitarity requirements. The ISR data support the presence of such a contribution.

Tensor Mesons: A Neglected Source of Photons and Leptons?

Abstract The Landau-Ginzburg phenomenological theory of superconductivity is used as a model of flux confinement. A monopole pair of sources is included to simulate a quark-antiquark system. The interaction energy is found in the static approximation appropriate for heavy quark systems, and equated with the interquark potential. This potential is compared with other suggested phenomenological potentials and succeeds in reproducing heavy quark spectra.

High partial waves in the phase-shift analysis of π+p scattering

Abstract A review of the application of quark models to photo- and electroproduction of the [70, 1-] nucleon resonances is presented. Also since there is no dynamically complete theory of the quarks in hadrons, we decompose a wide class of algebra-preserving quark models for electroproduction into three elements: the electromagnetic current, the quark wavefunctions, and the hadronic boost prescription. All quark models have made choices, often implicit, for these three ingredients although they are not independent in a complete theory. In focussing attention on these ingredients, we highlight the wide range of choices which may be made in empirical quark model applications. Several resulting models are examined and compared with both the proton magnetic form factor and the electroproduction data; some of these models compare more favourably with the data than others. In particular we find that popular models using free quark spinors cannot simultaneously fit the photoproduction data and the behaviour of the reduced matrix elements in the electroproduction region. However, with spinors derived from a Dirac equation with a potential all the elements present in the data may be reproduced.