Hypernuclear physics program with high-resolution π+-beam

In the past several years, hypernuclear research was performed almost exclusively by using recoil-less (K-, π-) reactions. Since the recoil momentum of hyperon produced by the recoil-less method is very small, only the substitutional states can be produced. For the advanced study of the hypernuclear structure, it is essential to produce various states of hypernuclei, especially the ground state. For this purpose, a new trial of producing hypernuclei via stopped-K- absorption was measured. It has been further suggested to consider other production method such as (π+, K+) reaction through which a neutron in a nucleus can be converted to Λ with the recoil momentum of approximately 350 MeV/c. Three methods of hyper nuclei production were compared and it was found that the yield of the ground-state hypernuclei we can obtain in one hour will be 25, 3 and 3 for (π+, K+), (K-, π-), and stopped-K- methods, respectively. Thus a program of the hypernuclear study by using (π+, K+) reactions at KEK-PS is proposed. The estimation of cost and man-power for this program was made and the results are summarized in this paper. (Aoki, K.)