T. Nagae

Evidence for heavy hyperhydrogen (Lambda)H-6

Evidence for the neutron-rich hypernucleus H-6(Lambda) is presented from the FINUDA experiment at DA Phi NE, Frascati, studying (pi(+), pi(-)) pairs in coincidence from the (K) over bar (-)(stop) + Li-6 -> H-6(Lambda) + pi(+) production reaction followed by H-6(Lambda) -> He-6 + pi(-) weak decay. The production rate of H-6(Lambda) undergoing this two-body pi(-) decay is determined to be (2.9 +/- 2.0) x 10(-6)/K-stop(-). Its binding energy, evaluated jointly from production and decay, is B-Lambda(H-6(Lambda)) = (4.0 +/- 1.1) MeV with respect to 5H + Lambda. A systematic difference of (0.98 +/- 0.74) MeV between B-Lambda values derived separately from decay and from production is tentatively assigned to the H-6(Lambda) 0(g.s)(+) excitationEvidence for the neutron-rich hypernucleus 6{\Lambda}H is presented from the FINUDA experiment at DA{\Phi}NE, Frascati, studying ({\pi}+, {\pi}-) pairs in coincidence from the K- +6Li \rightarrow 6 H+{\pi}+ production reaction followed by 6{\Lambda}H \rightarrow 6He + {\pi}- weak decay. The production rate of 6{\Lambda}H undergoing this two-body {\pi}- decay is determined to be (2.9\pm2.0)\cdot10-6/K-. Its binding energy, evaluated jointly from production and decay, is B{\Lambda}(6{\Lambda}H) = (4.0\pm1.1) MeV with respect to 5H+{\Lambda}. A systematic difference of (0.98 \pm 0.74) MeV between B{\Lambda} values derived separately from decay and from production is tentatively assigned to the 6{\Lambda}H 0+g.s. \rightarrow 1+ excitation.

Evidence for 6{\Lambda}H

Evidence for the neutron-rich hypernucleus H-6(Lambda) is presented from the FINUDA experiment at DA Phi NE, Frascati, studying (pi(+), pi(-)) pairs in coincidence from the (K) over bar (-)(stop) + Li-6 -> H-6(Lambda) + pi(+) production reaction followed by H-6(Lambda) -> He-6 + pi(-) weak decay. The production rate of H-6(Lambda) undergoing this two-body pi(-) decay is determined to be (2.9 +/- 2.0) x 10(-6)/K-stop(-). Its binding energy, evaluated jointly from production and decay, is B-Lambda(H-6(Lambda)) = (4.0 +/- 1.1) MeV with respect to 5H + Lambda. A systematic difference of (0.98 +/- 0.74) MeV between B-Lambda values derived separately from decay and from production is tentatively assigned to the H-6(Lambda) 0(g.s)(+) excitationEvidence for the neutron-rich hypernucleus 6{\Lambda}H is presented from the FINUDA experiment at DA{\Phi}NE, Frascati, studying ({\pi}+, {\pi}-) pairs in coincidence from the K- +6Li \rightarrow 6 H+{\pi}+ production reaction followed by 6{\Lambda}H \rightarrow 6He + {\pi}- weak decay. The production rate of 6{\Lambda}H undergoing this two-body {\pi}- decay is determined to be (2.9\pm2.0)\cdot10-6/K-. Its binding energy, evaluated jointly from production and decay, is B{\Lambda}(6{\Lambda}H) = (4.0\pm1.1) MeV with respect to 5H+{\Lambda}. A systematic difference of (0.98 \pm 0.74) MeV between B{\Lambda} values derived separately from decay and from production is tentatively assigned to the 6{\Lambda}H 0+g.s. \rightarrow 1+ excitation.

The superconducting kaon spectrometer — SKS

A superconducting kaon spectrometer has been installed in the north experimental hall of the KEK 12-GeV proton synchrotron. The spectrometer was designed to serve for nuclear physics experiments with meson beams in the 1 GeV/c region, particular emphasis being laid on study of Λ-hypernuclei via (π+, K+) reactions. In order to obtain Λ-hypernuclear data with better statistics and energy resolution, it was designed to have a good momentum resolution of 0.1% FWHM and a large acceptance of 100 msr. It consists of a large superconducting dipole magnet, tracking chambers, and trigger counters that can efficiently select kaons from large background of pions and protons. The overall energy resolution for scattering is realized together with a beam-line spectrometer in the K6 beam line, the momentum resolution of which was also designed to be better than 0.1% FWHM. A good energy resolution of better than 2 MeV FWHM has been confirmed in π−-12C elastic scattering and in the (π+,K+) reaction on 12C.

Development of mustrip gas chambers with multi-chip technology

Abstract We have developed the mustrip gas chamber (MSGC) by using multi-chip technology which supports high-density assembly of bare LSI chips on a silicon wafer. Our MSGC was operated steadily with ∼ 10 3 gain more than one week. An energy resolution of 15% for 5.9 keV X-ray of a 55 Fe source was obtained. With a very thin polyimide substrate of 16 μm thickness, two interesting phenomena were observed; one was a strong dependence of gains on backplane potential, and the other was little time variation of gains. We also found that a guard mask of a thin polyimide layer on the cathode edge reduced incidental electrical discharges between anode and cathode strips.

Development of an imaging microstrip gas chamber with a 5 cm × 5 cm area based on multi-chip module technology

Abstract We have developed a two-dimensional MicroStrip Gas Chamber (MSGC) with a 5 cm × 5 cm detection area based on Multi-Chip Module (MCM) technology. It has a 17 μm thin substrate, 254 anodes, and 255 back strips both with a 200 μm pitch. The MSGC was mounted on a large Pin Grid Array (PGA) package having more than 500 pins, which allowed us to readily connect a large number of signals of an imaging MSGC with readout electronics. In this article, we report on the capability of the MSGC as an X-ray imaging detector operated near an intense X-ray source. In order to get stable operation at high X-ray intensity, we found one solution using a ∼ 20 μm substrate and a surface resistivity of ∼ 10 15 Ω/square. The control of the surface resistivity was carried out by coating the polyimide substrate with organic titanium. This improvement enabled the MSGC to be stably operated for ∼ 10 3 s under a very high counting rate of 10 7 Hz/mm 2 . The MSGC is also being operated for several months under medium intensity X-rays from an X-ray generator. In this measurement, high quality digital X-ray images with ∼ 60 μm RMS (Root Mean Square) position resolution were obtained with a simple-readout method of recording only the positions of hit electrodes.

A superconducting spectrometer for the study of hypernuclei via (π, K+) reactions

SummaryA superconducting kaon spectrometer (INS-SKS) is under construction at Institute for Nuclear Study, University of Tokyo. The spectrometer, with 1/1000 momentum resolution and 100 msr acceptance, has been designed for intensive study of hypernuclei via (π, K+) reactions. It is to be installed in a new experimental hall of the KEK 12 GeV proton synchrotron and is scheduled to be ready for experiments by the end of 1990.RiassuntoUno spettrometro superconduttore a kaoni (INS-SKS) è in fase di costruzione all’Institute for Nuclear Physics dell’Università di Tokyo. Lo spettrometro, con una risoluzione di impulso di 1/1000 e accettanza 100 msr, è stato progettato per uno studio intensivo degli ipernuclei attraverso reazioni (π, K+). Dovrà essere installato in una nuova sala sperimentale del sincrotrone a protoni a 12 GeV del KEK e l’inizio degli esperimenti è previsto per la fine del 1990.РеэюмеВ институте ядерной фиэики при Токийском университете конструируется сверхпроводяший каонный спектрометр (INS-SKS). Спроектирован спектрометр с импульсным раэрещением 1/1000 и акцептансом 100 mcp для исследования гиперядер посредством (π, K+) реакций. Спектрометр смонтирован в новом зкспериментальном эале протонного синхротрона 12 ГзB в KEK. Начало зкспериментов планируется на конец 1990 г.

Quasifree production of Δ0 isobars in proton-nucleus reactions at 3.88 GeV/c☆

Abstract The quasifree production of the Δ 0 isobar by protons at 3.88 GeV/ c on d, C, Al and Cu nuclei has been studied through exclusive measurements of all final-state particles. Clear Δ-resonance peaks were observed in momentum spectra of forward proton, whose shapes were well reproduced by a calculation including the effects of binding energy and the Fermi motion. However, we found problems to reproduce the Δ-production cross sections by a cascade calculation based on such a quasifree picture.

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.

A broad range spectrometer PIK for medium-energy meson spectroscopy

Abstract A broad range spectrometer, PIK, has been constructed for the study of Λ hypernuclei via the ( π + , K + ) reaction. The spectrometer can also be used for nuclear spectroscopy with medium-energy meson beams. It consists of two independent spectrometers: one analyzes the incident beam momentum, and the other determines the momentum of the scattered particle. The latter spectrometer is characterized by a large solid angle of 15–22 msr, a broad range momentum acceptance of 0.55–1.1 GeV/ c , a wide angular acceptance of 11°, and a short flight path length of 4.5 m. The scattered particle is identified by the use of silica aerogel Cherenkov counters and Lucite Cherenkov counters and by measuring its time-of-flight. The performance of the spectrometer is examined by the ( π + , K + ) reaction on a 12 C target at P π = 1.05 GeV/ c and by the ( π + , p) reaction on a CH 2 target.