G.R. Brookes

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.

The quasi-deuteron photodisintegration process in lithium, carbon and calcium

Abstract An experiment is described in which the quasi-deuteron photodisintegration process was studied in the nuclei 7 Li, 12 C and 40 Ca, for photons of energy between about 150 and 250 MeV. Angular distributions of protons of energy between about 60 and 130 MeV, produced in coincidence with neutrons of energy 74.9 ± 17.0 MeV (FWHM) emitted at 90° in the laboratory, were measured with a spark chamber, scintillation counter telescope. The neutrons were detected by a scintillation counter and their energies determined by a time-of-flight method. The form-factor, F ( P ), defined as the probability of finding a neutron-proton pair of momentum P and zero separation in the ground state of the nucleus, is derived and used to determine the theoretical angular distributions. The cross section for the process is written as L ( NZ / A ) σ d , where σ d is the cross section for the photodisintegration of a deuteron and L is a constant. Comparison between theory and experiment leads to values of L for the three target nuclei in good agreement with that previously determined by this group for oxygen [1], and also with that obtained by Bishop et al. [2].

A 480-channel lead glass Cherenkov detector

Abstract The essential features, constructional details and performance of a 480-channel detector of lead glass total absorption Cherenkov counters are described. Results are presented on the linearity, energy and spatial resolution for electrons and photons in the energy range up to 4.8 GeV. The behaviour of charged hadrons in the detector is also described.

Observation of a baryon exchange dip and parton effects in backward photoproduction of ω

Abstract A measurement of backward photoproduction of omega mesons on protons is reported. Data are presented which show a dip in the differential cross section at u = −0.15 (GeV/ c ) 2 and an s dependence which varies strongly with u . The s dependence suggests an incoherent sum of a Regge and a parton term and differential cross sections for the two components are presented.

A high resolution photon tagging system in the GeV region

Abstract A photon tagging system which measures the energy of photons in a bremsstrahlung spectrum is described. The apparatus covers a photon energy range of 2 GeV starting 160 MeV below the energy of the incident electron beam. 192 counters provide a nominal resolution between 6 MeV for a photon energy 160 MeV below the incident electron energy and 11 MeV for a photon energy 2160 MeV below the incident electron energy.

Backward photoproduction of ϱ° and f between 2.8 GeV and 4.8 GeV

Abstract A measurement of backward photoproduction of charged pion pairs on protons is reported. The pion pair mass spectrum shows strong ϱ ° and f production. Data are presented on the u and s dependence for ϱ O and f, together with the decay polarisation for the ϱ O .

Forward and wide angle elastic φ-meson photoproduction on hydrogen between 2.8 and 4.8 GeV

Abstract The s and t dependence of φ (1019) photoproduction has been investigated in the incident photon energy range 2.8 to to 4.8 GeV. Differential cross-sections and density matrix elements are presented for a t range extending from t min out to −1.3 (GeV/ c ) 2 . The results are discussed in terms discussed in terms of an effective Regge trajectory in the t -channel.

A large aperture spectrometer for the study of multibody photoproduction in the incident energy range 1–5 GeV

Abstract A large aperture magnet spectrometer (LAMP 2) is described which was used in a tagged photon beam to collect 1.5 x 10 7 triggers from photoproduction processes in hydrogen. The techniques employed for the data acquisition and subsequent event reconstruction and kinematic identification are described and evaluated.

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.

Charged ρ photoproduction in the energy range 2.8–4.8 GeV

Measurements of the photoproduction processes γρ→ρ+n and γρ→ρ-Δ++ (1236) are reported in the energy range 2.8 to 4.8 GeV. The data show shrinkage of the differential cross section in this energy region for the process γρ→ρ-Δ++ (1236); no shrinkage is observed for the ρ+n process. The energy dependences of the ρ+n and ρ-Δ++ (1236) total cross sections are much steeper than current model prediction. The ρ spin density matrices for each process are also presented.