R.G. Moorhouse

What can asymptotic freedom say about e+e− → hadrons?

Abstract We discuss the continuation of asymptotically free quark model predictions for e+e− → hadrons in the complex q2 plane from spacelike to near timelike regions. At currently available energies we find we must compute gluon corrections to both the real and imaginary parts of the hadronic vacuum polarization tensor. Using quark masses defined by the position of the pole in the quark propagator we find good fits to the smeared data for a variety of models. However, use of an “off pole” definition of quark masses leads to a breakdown of the perturbation expansion even in regions far away from the real axis. Fits to the data outside these regions give highly correlated results dependent on the value of the strong coupling constant and the masses of the heavy quarks or leptons present. For a choice of the strong coupling constant consistent with observed scale violations in electroproduction, we find the data favors five quark flavors with a fifth quark of “mass” 2.3 GeV and a heavy lepton of mass ⋍ 2 GeV.

An analysis of single pion photoproduction in the second resonance region

We have analysed single pion photoproduction data off protons in the second resonance region, using an isobar model, in an attempt to determine how well the electromagnetic couplings of the S11(1520), D13(1520) and P11(1470) resonances are determined by the existing data. We find that both D13 couplings can be classed as well determined and the S11 coupling as fairly well determined. Within significant limits the photonic coupling of the Roper or P11(1470) resonance is undetermined by the existing data and possible experiments to resolve the ambiguities are discussed.

Multichannel analysis of KN data 0.4–1.2 GeV/c

Abstract An energy-dependent multichannel analysis of K N data in the momentum range 0.44–1.19 GeV/c has been made using parameterizations based on the K-matrix. Amplitudes and resonance parameters for the S, P, D, and F 5 2 waves are presented and compared with those of other analyses.

Multichannel analysis of anti KN data 0.4 to 1.2 GeV/c

Abstract An energy-dependent multichannel analysis of K N data in the momentum range 0.44–1.19 GeV/c has been made using parameterizations based on the K-matrix. Amplitudes and resonance parameters for the S, P, D, and F 5 2 waves are presented and compared with those of other analyses.

High energy pion photoproduction amplitudes from fixed-t dispersion relations and duality

Abstract Contributions to the high energy imaginary parts of the charged and neutral pion photoproduction amplitudes from degenerate ϱ and A 2 exchanges and ω and B exchanges are parametrized similarly to the dual absorptive model. These contributions together with the imaginary parts of the amplitudes found at low energies from partial-wave analyses are then used to evaluate the high energy real parts of the photoproduction amplitudes from fixed- t dispersion relations. A fit is made to data on pion photoproduction at 3.4 and 16 GeV incident photon energies, for momentum transfers up to −1(GeV/ c ) 2 . It is shown that much of the data is reproduced both qualitatively and quantitatively by our model. The high energy imaginary parts of the photoproduction amplitudes given by the fit are shown to be in accord with their average low energy behaviour.

CHARGED PION PHOTOPRODUCTION IN THE QUARK MODEL.

Abstract In terms of a quark model an explanation is given of charged pion photoproduction ratios, at small momentum transfer, in the processes γ N → π ± N, γ N → π ± Δ . The model is also shown to be consistent with π 0 photoproduction data.

Inflationary cosmology and 4-index tensor fields

Abstract We show how an arbitrarily large expansion of the ordinary dimensions in the very early universe can be achieved in the d = 11 supergravity theory where the 4-index anti-symmetric tensor field supplies the energy-momentum tensor. However, the decrease of the extra dimensions is too fast to give a satisfactory inflationary cosmology. If a 4-index tensor field is similarly used to provide the energy-momentum tensor in dimensions significantly greater than 11 the inflationary outlook is more hopeful.

On the elastic scattering of pions by deuterons

Abstract The elastic scattering of pions by deuterons is calculated for incident pion energies from 83 to 378 MeV. A variational method is employed which includes the effects of multiple scattering. Satisfactory agreement is obtained with experiment. For the pion-deuteron system the multiple scattering corrections turn out to be small but it is suggested that the method presented may be particularly suitable for future applications when multiple scattering effects are not small.

The relative signs of resonance formation amplitudes in a quark model

Abstract All the matrix elements for scattering processes meson + baryon → resonance → meson + baryon when the meson belongs to the pseudoscalar or vector nonet and the baryon to the lowest octet or decuplet, are calculated and tabulated on a quark model. The predictions for SU(3) inelastic processes of this type are non-trivial and critical for naive quark models. Some present and future comparisons with experiments are discussed.

Early Cosmology and the Dilaton and

Abstract Mechanisms for the preferential expansion of three of the spatial dimensions of a ten-dimensional universe are considered, in the context of the ten-dimensional supertring derived field theory with the gravitational field, the dilaton field and the three-index tensor field H . Two models in which the H field defines spatial three-spaces are investigated. One is quasi-chaotic at early times and leads to uniform expansion of all dimensions at later times; the other gives preferential expansion of one three-space. One possibility for the transition to the observed universe, through particle production by the dilaton field, is studied.