[en] We have studied the (π^-, K⁺) reaction on medium to heavy nuclear targets to investigate the sigma(Σ)-nucleus potential. The measured spectra were compared with theoretical calculations within the framework of the distorted-wave impulse approximation (DWIA), which demonstrates that a strongly repulsive Σ-nucleus potential with a nonzero size of the imaginary part reproduces the observed spectra

[en] Λ hypernuclei provide unique opportunities to explore interior of nucleus since a Λ is free from the Pauli exclusion principle of the nucleon. Therefore, a Λ can be a good probe to investigate dynamics of baryonic many body system proceeded deeply inside nucleus. In addition, there is an important role of studying Λ hypernuclei. Since the strangeness-involved two-baryon scattering experiments in free space are difficult, Λ hypernuclei provide invaluable information on the ΛN strong and weak interactions through their structure and weak decay mechanism. There are a several experimental activities on hypernuclear physics at the K6 beam line of KEK-PS. They are proceeded with good pion beam at 1.06 GeV/c provided from K6 and high-resolution/wide-aperture kaon spectrometer, SKS [1]. Among them, in this article, two experimental programs are introduced. One is spectroscopic investigation of light Λ hypernuclei (E336) [2], and the other is asymmetry of nonmesonic weak decay of polarized ⁵_ΛHe (E278) [3]. copyright 1997 American Institute of Physics

[en] Λ hypernuclei provide unique opportunities to explore interior of nucleus since a Λ is free from the Pauli exclusion principle of the nucleon. Therefore, a Λ can be a good probe to investigate dynamics of baryonic many body system proceeded deeply inside nucleus. In addition, there is an important role of studying Λ hypernuclei. Since the strangeness-involved two-baryon scattering experiments in free space are difficult, Λ hypernuclei provide invaluable information on the ΛN strong and weak interactions through their structure and weak decay mechanism. There are a several experimental activities on hypernuclear physics at the K6 beam line of KEK-PS. They are proceeded with good pion beam at 1.06 GeV/c provided from K6 and high-resolution/wide-aperture kaon spectrometer, SKS [1]. Among them, in this article, two experimental programs are introduced. One is spectroscopic investigation of light Λ hypernuclei (E336) [2], and the other is asymmetry of nonmesonic weak decay of polarized ⁵_ΛHe (E278) [3]

No abstract available

[en] As a hypernuclear spectrometer system, the K6 beam line and SKS have been providing opportunities to proceed spectroscopic investigations of Λ hypernuclei via the (π⁺, K⁺) reaction with better quality. Particularly, new spectroscopic information on the hypernuclear structure has been being brought by the facility, as introduced in section 2, where unique features of the (π⁺, K⁺) reaction are demonstrated. The facility at K6 of KEK-PS will be playing a leading role on hypernuclear spectroscopic studies via the (π, K+) reactions for a while until JHF comes true. At JHF, hypernuclear spectroscopy with high precision will be proceeded owing to high-intensity and high-quality secondary beams generated by high-power primary proton beam served by the 50-GeV PS. (author)

[en] It has been shown in previous work that (π⁺, K⁺) reactions at around P_π ∼ 1 GeV/c can produce Λ hypernuclear states with large spin polarization and spin alignment. These hypernuclear states produced preferentially by the (π⁺, K⁺) reaction, however, are mostly in the unbound region with high excitation energy because of large (angular) momentum transfer involved in the reaction. Thus these states are excited as resonant states by the direct strangeness-transfer (π⁺, K⁺) reaction. If the Λ is bound or effectively bound, the escape width of the Λ is small. Then the resonant states, acting as initial doorway states, form compound hypernuclei through spreading process. The compound Λ-hypernuclei decay by emitting nucleons and γ rays, leading to the low-lying Λ-hypernuclear states in the bound region. The purpose of this paper is to describe very briefly that spin polarization and spin alignment of resonant (particle-unbound) Λ hypernuclear states produced by the (π⁺, K⁺) reactions are well preserved through particle and γ decays, and that the spin (s_λ) of Λ as well as the total spins (J_f) of the final Λ hypernuclear states are well polarized

[en] A hypernuclear states with spin polarization are shown to be populated through nucleon and γ decays of compound Λ hypernuclei produced by resonant (π⁺,K⁺xnypγ) reactions. The low-lying Λ-hypernuclear states have the Λ hyperon in the lowest 1s_1/2 orbit. The intrinsic spin of Λ(s_Λ) is also shown to be well-polarized. These spin-oriented hypernuclear states are useful for spectroscopic studies of hypernuclei such as electromagnetic moments and weak decays. (orig.)

[en] A high-intensity, high-resolution pion beam line has been proposed for the Japan Hadron Facility. An intensity of 10⁹ and a momentum resolution of 10^-4 will be available. High-resolution, high-statistics, and high-sensitivity spectroscopic studies of hypernuclei will be possible. (orig.)

[en] Recently it has been shown that (π⁺, K⁺) reactions at around P_π ∼ 1GeV/c can be produced Λ hypernuclear states with large spin-polarization and spin-alignment. It is very interesting to produce spin polarized hypernuclei and to study asymmetry of weak decay of the polarized hypernuclei. We have a plan to produce polarized-Λ hypernuclei and to study asymmetry of the non-mesonic weak decay of the polarized-Λ hypernuclei. Asymmetry of non mesonic decay from the 1^- ground states of ¹²C and 5/2⁺ one of ¹¹B will be studied in the experiment. Here the ground state of ¹¹B is populated through proton decays (strong baryon decay) of 2⁺ states in ¹²C. Protons from non-mesonic decays are studied in coincidence with ¹²C(π, K⁺) reaction feeding the 1^- and 2⁺ states of ¹²C. Protons from non-mesonic decays of the ¹²C(1^-) and ¹¹B(5⁺/2) states are measured by two sets of ΔE·E counter telescopes which consist of 5mm plastic scintillator and segmented NaI scintillators. The PIK spectrometer, which has been constructed at the KEK K2 beam line, is used for the (π⁺, K⁺) reaction to produce hypernuclei. It's resolution is good enough to resolve the 1^- and 2⁺ states in ¹²C. The present plan is the first and important step for further study of weak and electromagnetic (magnetic moment γ decay etc.) process in hypernuclei

[en] We have investigated the response of KEK secondary emission chamber for protons at 4, 5 and 12 GeV, and for deuterons at 7, 8 and 10 GeV. The response was measured both by the 'foil activation' technique and by secondary pions produced from a carbon target. (author)