K. Ichimaru

Particle production in the target-rapidity region from hadron-nucleus reactions at several GeV

Abstract Highly inelastic processes in hadron-nucleus reactions at several GeV have been studied by measuring multi-particle emission in the target-rapidity region. Events with no leading particle(s) but with high multiplicities were observed up to 4 GeV. Proton spectra from such events were well reproduced with a single-moving-source model, which implied possible formation of a local source. The number of nucleons involved in the source was estimated to be (3–5)A 1 3 from the source velocity and the multiplicity of emitted protons. In those processes the incident energy flux seemed to be deposited totally or mostly (>62;75%) in the target nucleus to form the local source. The cross sections for the process were about 30% of the geometrical cross sections, with little dependence on incident energies up to 4 GeV and no dependence on projectiles (pions or protons). The E0 parameter in the invariant-cross-section formula E d3σ/dp3 = A exp (−E/E0) for protons from the source increases with incident energy from 1 to 4 GeV/c, but seems to saturate above 10 GeV at a value E0 = 60–70 MeV. Three components in the emitted nucleon spectra were observed which would correspond to three stages of the reaction process: primary, pre-equilibrium and equilibrium.

Stopping and energy deposition of GeV particles in target nuclei

Abstract In a study of hadron-nucleus reactions we were able to identify events in which leading particles were completely (or mostly) stopped and deposited their energies up to 4 GeV in target nuclei to form moving sources. Cross sections for such “stopped” events were nearly constant over the energy range from 2 to 4 GeV and amounted up to 30% of geometrical cross sections.

Analyses of particle production in hadron-nucleus reactions at several GeV with a two-moving-source model

Abstract Spectra of protons and pions emitted in the target-rapidity region in hadron-nucleus reactions at 3 and 4 GeV c were observed in wide momentum- and angular-acceptance measurements. Fitting to the data with the two-moving-source model well reproduced experimental proton spectra with the slope parameters of 50–60 MeV for one component and 110–125 MeV for another. The slope parameters for pions were 120–165 MeV, larger than those for protons. Energy depositions of GeV particles were estimated by integrating energies carried away through the particle production

Readout system for a cylindrical drift chamber “Michie”

Abstract A readout electronic system for a jet-chamber-type cylindrical drift chamber has been constructed for nuclear experiments at the KEK proton synchrotron. The system handles amplitude and timing information of signals from 384 resistive sense wires, and is able to record multiple hits up to 4 per wire. For detecting composite particles together with minimum ionizing particles, the system was designed to cover a wide dynamic range. A multiprocesser system with use of VERSAbus and MC68000 microprocessors has been developed for fast data handling and for communication with a host computer.

The T = 1, isospin triplet states in A = 30 nuclei

Abstract The level structure of 30 S was studied using the 28 Si (τ, n p ) reaction at E τ = 9.5 MeV , and J π values were determined for some proton-emitting states by the neutron-proton angular correlation measurements. The Coulomb displacement energy of the isospin triplet state of A = 30 nuclei was analyzed using first-order perturbation theory. Large deviations from perturbation theory were found for the ground state, the 2 + 1 state, the 3 − 1 state and the second excited 0 + state. These results might be explained by the effect of the pairing correlation of the two valence protons in 30 S under the assumption of charge symmetry for the nucleon-nucleon interaction.

Deuteron emission from pion absorption at Tπ = 65 MeV

Abstract The angular distributions of high-energy deuterons and proton-deuteron coincident events were measured at T π = 65 MeV for C, Al and Cu. The angular distribution of the inclusive ( π + , d) cross section was similar to that of the inclusive ( π + , p?) reaction, but the ratios of the inclusive ( π + , pd?) cross section to the inclusive ( π + , pp) cross section had a strong angular dependence. These results support the idea that contributions from the three-nucleon absorption as well as those from the two-step process are important for the emission of high energy deuterons at T π = 65 MeV.

Analysis of deuteron spectra from hadron-nucleus reactions at several GeV/c with the coalescence model

Abstract Spectra of protons and deuterons emitted in hadron-nucleus reactions at 4 GeV/ c were studied with the coalescence model to deduce information on the spatial extent of the emission source. The source sizes correlated strongly to nucleon multiplicities, and indirectly to the target mass and the associated pion multiplicity. Theanalysis indicated the formation of a slow moving source previously assumed in the two-moving-source parametrization.

Broad component of the ( pi +,pp) angular correlation.

The angular correlation of the ({pi}{sup +},{ital pp}) and ({pi}{sup {minus}},{ital pp}) cross sections for {sup 6}Li, {sup 7}Li, and C was measured in a wide angular range. We analyzed the structure of the ({pi}{sup +},{ital pp}) angular correlation comparing cross sections between the two reactions. It was found that the broad component of the ({pi}{sup +},{ital pp}) angular correlation is mainly due to the two-step processes associated with the two-nucleon absorption.