Hypernuclear production by the (π+,K+) reaction

Abstract

The (${\pi }^{+}$,$K^{+}$) strength functions (cross sections) are systematically calculated in the distorted-wave impulse approximation for the production of light-to-heavy hypernuclei: ${}_{\mathrm{\Lambda }}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{\mathrm{\Lambda }}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{\mathrm{\Lambda }}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{\mathrm{\Lambda }}{}^{40}{}_{}{}^{}\mathrm{Ca}$, ${}_{\mathrm{\Lambda }}{}^{56}{}_{}{}^{}\mathrm{Fe}$, ${}_{\mathrm{\Lambda }}{}^{90}{}_{}{}^{}\mathrm{Zr}$ (and ${}_{\mathrm{\Lambda }}{}^{208}{}_{}{}^{}\mathrm{Pb}$). The quasifree continuum effects are taken into account in the frameworks of the Kapur-Peierls method and also of the continuum shell model. The characteristic feature of the (${\pi }^{+}$,$K^{+}$) reaction is to provide well-separated series of peaks with high spin corresponding to the bound and resonant Λ states, yielding information on deep-lying hyperon states in heavy nuclei as well. Reasons for this effectiveness are clarified and discussed. The calculated results are in good agreement with the recent experiments which further demonstrates that the average Λ nucleus well can be simulated by an appropriate Woods-Saxon type potential ($V_0$≊-30 MeV) over a wide mass range of hypernuclei to a good approximation.