T. Miyachi

New lead glasses for Cherenkov counters

Abstract Attempts have been made to improve the characteristics of glasses suitable for Cherenkov counters of the total-absorption type. Many kinds of new lead glasses were prepared and examined in the transmittance, radiation lengths, and methods of manufacturing. Several kinds of glass blocks having the dimension of 65 × 65 × 235 mm 3 were manufactured successfully. The transmittance of one of the new glasses is higher than the usual lead glass of F-2 ∗ . It was also found that the discoloration of the new glasses is smaller than the usual lead glasses upon irradiation of 60 Co γ rays of 10 4 to 10 7 Roentgens. The Cherenkov counters of the total-absorption type with the new glasses, together with the ones with usual lead glasses of F-2, SF-2, SF-5, and SF-6, were tested by using electron beams with energies from 300–1000 MeV. It was found that the energy resolution of the first ones is better by a few percents than that of the latter in the whole energy region.

Differential cross sections of proton compton scattering in the resonance region

Abstract Differential cross sections of proton Compton scattering have been measured in the energy range between 375 MeV and 1150 MeV in steps of 25 MeV at c.m. angles of 130°, 100° and 70°. The recoil proton was detected with a magnetic spectrometer. In coincidence with the proton, the scattered photon was detected with a lead-glass Cerenkov counter of the total absorption type. Theoretical calculations based on an isobar model with two components, that is, the resonance plus the background, were practiced. The photon couplings of the second resonance region were determined from the proton Compton data for the firs time. The results were that the helicity 1 2 photon couplings of P11(1470) and S11(1535), and the helicity 3 2 photon coupling of D13(1520) were consistent with those determined from the single-pion photoproduction data; however, the helicity 1 2 photon coupling of D13(1520) required a somewhat larger value than that from the single-pion photoproduction data.

Recoil proton polarization of neutral pion photoproduction from protons in the energy range between 400 MeV and 1142 MeV

The recoil proton polarization of the reaction γp → π0p was measured at a c.m. angle of 100° for incident photon energies between 451 and 1106 MeV, and at an angle of 130° for energies from 400 to 1142 MeV. One photon, decayed from a π0 meson, and a recoil proton were detected in coincidence. Two kinds of polarization analyzer were employed. In the range of proton kinetic energy less than 420 MeV and higher than 346 MeV, carbon plates and liquid hydrogen were used for determining the polarization, respectively. The data given by the two polarimeter systems are in good agreement. Results are compared with recent phenomenological analyses. From the comparison between the present data and the polarized target data, the invariant amplitude A3 can be estimated to be small.

Photoproduction of πΔ(1236) from protons below 1.1 GeV

Abstract The π + and π − momentum spectrum of the reaction γ p → ππ N have been measured at lab angles 20°, 40°, 60° and 90° and photon energies 0.744, 0.844, 0.944 and 1.044 GeV with a magnetic spectrometer using the photon subtraction method. Both spectra show a peak corresponding to the production of the πΔ(1236) state. The analysis has been carried out with amplitudes for the quasi two-body process γ p → πΔ (1236) and a phase-space background so as to reproduce both π + and π − spectra. The ratio of cross sections σ ( γ p → π + Δ 0 )/ ( γ p → π − Δ ++ ) is found to vary 0.0 to 1.8, depending on kinematical conditions.

Polarization of recoil neutrons from single-pion photoproduction off protons in the resonance region

Abstract The polarization of the recoil neutrons from the reaction γ p→ π + n was measured at a c.m. angle of 105° for incident photon energies between 675 and 1125 MeV. A scattered π + meson and a recoil neutron were detected in coincidence with a magnetic spectrometer and a neutron polarimeter system using liquid hydrogen. Results are compared with recent phenomenological analyses and the other existing data measured by the double polarization measurement technique.

Flexible Adiabatic Light Guide of Silicon Rubber

A certain type of silicon rubber (KE103RTV) is found to be a useful material as an adiabatic light guide for scintillation counters because of its mechanical flexibility. The refractive index of KE103RTV is measured to be 1.410±0.006. The transmission and the resolution of scintillation light pulses through it are comarable with those through acrylic resin light guides. This RTV has the resistivity against high dose of radiation.

Electron-Induced Cascade Shower in Lead Glass

In order to provide useful data for designing a lead glass Cherenkov counter, observations were made on the longitudinal distributions of cascade showers developed in the SF-2 lead glass at the energies of 450, 650 and 800 MeV. The results agreed well with the calculated values based on the approximation B.

Measurement of linear polarization of coherent bremsstrahlung by detecting the angular correlation in pair production

Abstract The linear polarization of the coherent bremsstrahlung from a single crystal of silicon was measured by observing the one-dimensionally projected angles of electron and positron pairs. The coherent bremsstrahlung was produced by injecting the 1153 MeV electrons to the silicon crystal nearly along the [110] axis. The emission angles, η + and η − , of pair particles were determined event by observing their tracks with a set of four wire spark chambers. From the ( η + , η − ) distribution of events, the polarization of photons was evaluated. The obtained polarization was consistent with the calculated values, and the technique gives a new approach to the measurement of the linear polarization of photons.

Differential cross sections for photoemission of deuterons from the nitrogen nucleus

Abstract Momentum distributions for inclusive photoemission of deuterons from nitrogen have been measured at laboratory angles of 43° and 50°, and for maximum energies of the bremsstrahlung photon beam of 725, 775 and 825 MeV. The double differential cross sections of deuterons emitted from nitrogen are obtained for photon energies of 750 and 800 MeV and for laboratory angles of 43° and 50°. The photon energy is determined by the photon subtraction method. Results are examined by a π 0 photoproduction process off a quasi-deuteron in nitrogen ( γ ″d″→ π 0 d) and by a two-step process. The two-step process means the following: first, a nucleon is produced by a photo-pion production process from a quasi-free nucleon in the nitrogen nucleus ( γ ″N″→ π N); second, the nucleon produced at the first step picks up another nucleon in the nucleus and then a deuteron is emitted (N+A→d+anything).