Kunio Takamatsu

Augular Distributions of the Alpha Particles from the ( p , α) Reactions on Na 23 and K 39 at 6.9∼7.3 MeV

The angular distributions of the reactions Na 23 ( p , α)Ne 20 and K 39 ( p , α)A 36 leading to the ground and first excited states of the residual nuclei have been measured at 6.9, 7.1 and 7.3 MeV of the incident proton energy, respectively, by the use of a semiconductor detector. For the reaction Na 23 ( p , α)Ne 20 the angular distributions of these alpha particles are almost 90° symmetrical at 7.1 MeV of the incident proton energy, and they are slightly unsymmetrical about 90° at 7.3 and 6.9 MeV. For the reaction K 39 ( p , α)A 36 , the angular distributions are almost 90° symmetrical at all energies of the incident protons. It is considered that the reactions Na 23 ( p , α)Ne 20 and K 39 ( p , α)A 36 leading to the ground and first excited states of the residual nuclei, at around 7 MeV of incident proton energy, occur through a compound nucleus process and in the former reaction the number of the compound states excited by the about 7 MeV protons are probably not so many as to justify the statistical...

Cerium fluoride, a highly radiation-resistive scintillator

Abstract The excitation-emission spectrum, pulse-height spectra for low energy γ-rays, transmission spectrum, radiation-hardness, etc. of a CeF 3 single crystal are given. No sizable degradation in transmission has been detected against 60 Co γ-ray irradiation up to the accumulated dose of 10 6 rad. The degradation caused by the dose of 10 7 rad is less than 5% per unit radiation length. The radiation damage recovers with an exponential time constant of about 40 days. CeF 3 seems to be one of the most promising materials for electromagnetic calorimeters in high energy and/or high beam intensity environments.

Study of the π0π0 system in pp central collisions at 450 GeV/c

Abstract The effective mass spectrum of π0 pairs produced in pp central collisions (pp → pfπ0π0ps) at 450 GeV/c, s = 29 GeV , below 1 GeV differs from that observed in peripheral charge exchange reactions. In particular, there is a large number of events between ππ-threshold and 1 GeV, that interfere with f0(980) destructively. The possible existence of a broad S-wave state is suggested.

Study of the ηπ− system in the π−p reaction at 6.3 GeV/c

Abstract Data of the ηπ− system were obtained in the reaction π−p → ηπ−p at 6.3 GeV/c beam momentum. About 17 k events of ηπ− were collected in the mass range 0.8 ⩽ Mηπ- ⩽ 1.8 GeV/c2 and in the range of the momentum transfer squared 0.075 ⩽ |t′| ⩽ 0.60 (GeV/c)2. A large forward-backward asymmetry was observed around 1.3 GeV/c2 in the Gottfried-Jackson frame of the ηπ− system. A partial wave analysis of the data was performed. A peak of the D+ wave attributed to a2 (1320) is clearly seen. An enhancement is observed around 1.3 GeV/c2 in the P+ wave.

Beam test of a calorimeter prototype of PWO crystals at energies between 0.5 and 2.5 GeV

The results of a beam test are presented concerning the energy resolution of a calorimeter hodoscope prototype of PWO (PbWO4) crystals, measured by electron beams having energies between 0.5 and 2.5 GeV. The hodoscope consists of a 3 × 3 matrix of modules of PWOs having dimensions of 20 mm × 20 mm in cross section and 200 mm in length. The energy dependence of the energy resolution is obtained to be (σ/EGeV))2=((0.0310±0.0011)/E(Gev))2+(0.0079±0.0025)2, fitted by a quadratic form.

Energy Dependence of Angular Distributions of the Reaction Al27(p, α)Mg24 in the Energy Region between 10.5 and 14.5 Mev

The angular distributions of the reactions Al 27 ( p , α)Mg 24 resulting in the ground and first excited states of Mg 24 were measured at 37 energies between 10.5 and 14.5 Mev, making use of proportional counters. Similar behaviour was obtained for both reactions. The variation of the shape of the angular distributions with the bombarding energy is rather smooth in the higher energy region, but becomes rapid with decreasing the bombarding energy. There appear some resonance-like peaks and valleys in the excitation curves at laboratory angles of 50°, 90° and 130° but their positions are not coincident with one another and in the higher energy region these peaks disappear in the excitation curves for the total cross sections. The variations of the excitation curves for the total cross sections and of the shape of the angular distributions with energy in the lower energy region may be due to the fluctuations in the number or properties of the compound nucleus levels and to the interference between the compou...

A beam test on a fast EM-calorimeter of gadolinium silicate, GSO(Ce)

Abstract A large GSO crystal with 4.9 cm diameter and 19.6 cm length was tested with a π−/μ−/e− beam. The energy resolution ΔE/E was 7.0% in FWHM for 1 GeV electrons in agreement with the EGS simulation. The e−/π− separation was 1/1000 at 1 GeV/c when an energy cut of ±2σ is made at the electron peak. The pulse height uniformity along the axis was excellent within ± 2%.

Vector resonances around 1.6 GeV of the ηπ+π− system in the π−p charge exchange reaction at 8.95 GeVc

Abstract High statistics data of the ηππ system in π − p → ηπ + π − n were obtained. A partial wave analysis was performed in the mass region between 1.37 and 1.85 GeV. Resonant structures were observed in the IJ PC = 11 −− wave around 1.6 GeV and in 13 −− around 1.7 GeV. The structure in 11 −− was fitted with a single Breit-Wigner and also fitted with two Breit-Wigners. The result suggests the possible existence of two vector resonances around 1.6 GeV. The structure in 13 −− is considered to be the π 3 (1690).

(d,/cap alpha/) REACTIONS ON F

The angular distributions of the emitted alpha particles from the ( d , α) reactions on F 19 , Ne 20 , P 31 and S 32 leading to the ground states and several excited states of the residual nuclei have been measured at an incident deuteron energy of 14.7 Mev. The emitted alpha particles were detected with a solid state detector of a silicon p-n junction. The alpha particle groups, α 0 of the ground state transitions for all targets and the alpha particle groups of several excited state transitions for F 19 and S 32 show pronounced peaks at forward angles and oscillatory behaviors in the angular distributions, which were compared, and were in good agreement, with the theory of the two nucleon pickup process. The angular distributions of other alpha particle groups for excited state transitions show nearly symmetrical behaviors about 90° and the cross sections of them are smaller by about a factor of 2∼5 than those of α 0 . These facts suggest that these reactions occur through different process, and are con...

sup 19

The interference effects in the production of bremsstrahlung in a silicon single crystal have been studied by using 720 MeV electrons. The energy spectrum of the bremsstrahlung has exhibited interference maxima of the first five orders. The intensity variation of the 150 MeV photons with the rotation of the crystal has shown also three interference Maxima on each side of the central minimum. The observed interference conditions for the photon energy and angles of incidence of electrons relative to crystal axes are in good agreement with the theory.