W. Galbraith

The total photon deuteron hadronic cross-section in the energy range 0.265-4.215 gev

Abstract The total cross section for photoproduction of hadrons on the deutron, σTd, has been measured for photon energies in the range 0.265–40215 GeV. From this, using results for the photon total cross section, obtained previously with the same apparatus, the neutron total cross section has been determined in the resonance region. The resonant structure is found to be quite different from that for the proton. Thereafter the neutron cross section falls off steadily with energy, and the values obtained are consistently lower than those for the proton. Forward scattering amplitudes have been evaluated for the deuteron.

Polarisation parameters in positive pion photoproduction

Abstract Measurements have been made of the polarisation parameters Σ , T and P for the process γ p → π + n in the photon energy range 520–2250 MeV at c.m. angles between 30° and 120°. These data were obtained in a double polarisation experiment, using the polarised photon beam from the Daresbury electron synchrotron incident on a polarised proton target. The data are compared with predictions from current theoretical analyses.

Polarisation parameters in neutral pion photoproduction

Abstract The polarisation parameters Σ, P and T have been measured for the process γ p→ π 0 p in the photon energy range 1300–2100 MeV and c.m. angles between 30° and 110°, in an experiment with a polarised beam and polarised target. The results are compared with a recent theoretical analysis which fits data from threshold to 16 GeV. The new data are in general agreement with the analysis, but with some significant discrepancies in detail.

Measurements of the double polarisation parameters G and H in neutral pion photoproduction

Abstract Measurements have been made of the double polarisation parameters G and H in the photoproduction of neutral pions from protons, for incident photon energies between 1300 MeV and 2300 MeV and for pion c.m. angles between 50δ and 80δ. The results are compared with predictions from a recent comprehensive analysis of earlier photoproduction data.

Measurements of the polarisation of the recoil proton in elastic electron proton scattering at q2 = 1.3, 1.5 and 1.9 (GeV/c)2

Abstract An experiment has been carried out to determine the imaginary part of the two-photon exchange amplitude by measuring the polarisation of the recoil proton in elastic electron-proton scattering. The polirisation was found to be −0.006 ± 0.030 at q2 = 1.3 (GeV/c)2, +0.052 ± 0.55 at 1.5 (GeV/c)2 and +0.065 ± 0.087 at 1.9 (GeV/c)2.

The polarised beam asymmetry in photoproduction of eta mesons from protons at 2.5 GeV and 3.0 GeV

Abstract Measurements of the polarised beam asymmetry parameter Σ for eta photoproduction from protons, have been carried out at incident energies of 2.5 GeV and 3.0 GeV, and for various t -values between −0.2 (GeV/c) 2 and −1.2 (GeV/c) 2 . The values of Σ are close to +1 for values of | t | less than 0.7 (GeV/c) 2 , showing that there can be little contribution from unnatural parity exchange in any Regge exchange model of the process, in disagreement with present theories. Differential cross sections for the process werre also measured, and are consistent with those from other experiments.

The total photon-proton cross-section for hadron production

Abstract The total hadronic cross section, σ T has been measured for tagged γ -rays, using electron beams in the GeV range, and narrow energy bins. Preliminary data are given covering the γ -energy region 275 MeV-1850 MeV, where interesting structure characteristics are observed.

Measurements of the polarisation parameters G and H in positive pion photoproduction

Measurements have been made of the polarisation parameters G and H for the process γp→π+ n in the photon energy range 600–1875 MeV and pion c.m. angles between 30° and 100°. These data were obtained in a double polarisation experiment, in which the polarised photon beam from the Daresbury electron synchrotron was incident upon a polarised proton target. Theoretical predictions from a current analysis are compared with the data.

A measurement of the beam asymmetry parameter Σ for neutral pion photoproduction in the energy range 1.2–2.8 GeV

An experiment has been completed at the Daresbury synchrotron to measure the asymmetry in the photoproduction cross section of neutral pions on hydrogen, for photons polarised normal to and in the production plane. The source of polarised photons was coherent bremsstrahlung of electrons traversing the lattice structure of diamond and the polarisation P of the γ beam was calculated from the measured intensity of the coherent spike. The asymmetry parameter Σ, defined as Σ = (σ⊥ − σ|)/(σ⊥ + σ|) where σ⊥(σ|) are the cross sections for photons polarised perpendicular (parallel) to the production plane, has been measured over a range of photon energies from 1.2 to 2.8 GeV and over a range of −t (the square of the four-momentum transfer) from 0.13 (GeV/c)2 to 1.4 (GeV/c)2. A marked energy variation in the value of Σ is found over the energy region 1.6–1.8 GeV.

The polarised target asymmetry in photoproduction of eta mesons from protons at 4 GeV

Abstract Measurements have been made of the polarised target asymmetry parameter T for eta photoproduction from protons at a photon energy of 4 GeV and t -values of −0.4, −0.6 and −0.8 (GeV/ c ) 2 . The results are compared with predictions for this quantity.