H. Yokota

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.

Measurement of e+e-†bb forward-backward charge asymmetry between ss =52 and 57 GeV

Using 123 multihadronic inclusive muon-production {ital e}{sup +}{ital e}{sup {minus}} annihilation events at an average c.m. energy of 55.2 GeV, we extracted the forward-backward charge asymmetry of the {ital e}{sup +}{ital e}{sup {minus}}{r arrow}b{bar b} process and the {ital R} ratio for {ital b{bar b}} production. We used an analysis method in which the behavior of the {ital c} quark and lighter quarks is assumed, with only that of the {ital b} quark left indeterminate. The results, {ital A}{sub {ital b}}={minus}0.72{plus minus}0.28(stat){plus minus}0.13(syst) and {ital R}{sub {ital b}}=0.57{plus minus}0.16{plus minus}0.10, are consistent with the standard model.

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.

An X-ray detector as a detector for electron identification

Abstract An X-ray detector (XRD) which identifies electrons using their synchrotron radiation will be installed in the AMY detector to improve its e/π separation ability by a factor of ∼ 30. The construction of the XRD has been completed, and various tests are proceeding using radioactive sources and cosmic rays. We are planning to install the XRD in the AMY detector during an upcoming shutdown in April. In this report, several unique features in the design and the results of the tests are presented.

A measurement of

Using 123 multihadronic inclusive muon-production {ital e}{sup +}{ital e}{sup {minus}} annihilation events at an average c.m. energy of 55.2 GeV, we extracted the forward-backward charge asymmetry of the {ital e}{sup +}{ital e}{sup {minus}}{r arrow}b{bar b} process and the {ital R} ratio for {ital b{bar b}} production. We used an analysis method in which the behavior of the {ital c} quark and lighter quarks is assumed, with only that of the {ital b} quark left indeterminate. The results, {ital A}{sub {ital b}}={minus}0.72{plus minus}0.28(stat){plus minus}0.13(syst) and {ital R}{sub {ital b}}=0.57{plus minus}0.16{plus minus}0.10, are consistent with the standard model.

e^+e^- \to b\bar{b}

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.