M. Kawabata

A study of nucleon properties in nuclei through (p, 2p) reactions

Abstract The differential cross sections and analyzing powers have been measured for a proton knockout reaction from s 1/2 orbits of several target nuclei aiming at studying nuclear medium effects in the nucleon-nucleon interaction, and in-medium nucleon properties through it. It is confirmed from the cross section data that the reaction mechanism is simple and contribution from the multi-step processes is less than ten percent, only a few percent for a 12 C target case. The analyzing power shows a distinct reduction from the value of the free proton-proton scattering and the target dependence, which is equivalent to the density dependence, of the reduction suggests existence of a medium effect. The study has been extended to the measurement of other spin observables, polarization and spin-transfer coefficients, and a preliminary result is given.

A profile and flux monitor for the few GeV neutron beam at KEK

Abstract We describe a neutron beam monitor in the few GeV region developed for an experiment of the n + p → d + γ differential cross section measurement at the KEK-PS. It was used to monitor the profile and the flux of the neutron beam. The detector is a 3-plane plastic scintillator hodoscope. We present the design and performance of the monitor. The detection efficiencies evaluated with various Monte Carlo simulation codes are compared to the results of the measurements.

Differential cross sections for np → dX at 1.0 and 2.0 GeV

Abstract Inclusive deuteron spectra ( d 2 σ dΩdp ) have been measured for the reaction np → dX at neutron energies of 1.0 and 2.0 GeV. A quasi-monochromatic neutron beam was used, along with a liquid hydrogen target. Recoil deuterons at laboratory angles from 3° to 15° were tracked in wire chambers surrounding a 1.5 T·m dipole magnetic field. Particle identification was achieved using time-of-flight and momentum measurements. The deuteron data are compared with the predictions of a one-nucleon-exchange model with σ meson production. At 2 GeV the missing mass spectra suggest the large role played by both the η and ϱ mesons in deuteron production.

Neutron beam line at the KEK 12-GeV PS

A neutron beam line has been constructed at the KEK-proton synchrotron. Neutrons have been produced by the disintegration reactions of deuterons in a 6 cm thick beryllium target. Deuteron beams of 2–6 GeV have provided neutron beams of 1–3 GeV. The neutron flux increases with the deuteron energy. The typical beam intensities obtained were 1 × 108, 2 × 108, and 3 × 108 neutrons per 1011 deuterons of 2, 4, and 6 GeV, respectively. The neutron-momentum width, Δpp, was measured to be (4 ± 1) % in sigma at 1 GeV.

Exclusive measurement of S1/2 proton knockout reaction

A pair spectrometer system installed newly at RCNP Osaka has been made available for high resolution studies of particle‐particle correlation measurements. By using this system, the analyzing power (Ay) for 1s1/2 proton knockout reaction on a 12C target and 2s1/2 knockout on a 40Ca have been measured with the same geometrical setting. A significant suppression of Ay has been observed in the 12C case. But the suppression in the 40Ca case is found much more moderate and is explained by a DWIA calculation as a distortion effect.