Hypernuclear spectroscopy and weak decays at KEK

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 5ΛHe (E278) [3]