Theoretical Study of a Prototype System of Kaonic Nuclei “K− pp”

In strange nuclear physics and hadron physics, kaonic nuclei (nuclear system with anti-kaons (K)) have been a hot topic since the formation of dense state are interestingly expected due to the strong KN attraction. To reveal the nature of kaonic nuclei, which could be an exotic system, lots of efforts have been devoted to the study of a prototype system of kaonic nuclei, “Kpp”. Especially, now is the very exciting time because new experimental results are being reported from two groups of J-PARC (E15 and E27). We are theoretically investigating the Kpp with a coupled-channel Complex Scaling Method (ccCSM) which was proposed in our previous work [1]. This method can treat simultaneously coupled-channel problem and resonance problem which are important ingredients in the study of Kpp. Recently, we have developed a handy method, so-called ccCSM+Feshbach method. The Kpp is actually a coupled-channel system of KNN-πΣ N-πΛ N. However, we can treat it as a single-channel problem of KNN by a tricky use of ccCSM. As a result of careful calculation with the ccCSM+Feshbach method using an energy-dependent potential based on chiral SU(3) theory [1], we find that the Kpp is not so deeply bound with ~30 MeV binding. The decay width depends on a parameter and ansatz for the treatment of energy dependence; 20~60 MeV. Analyzing the ccCSM wave function, we find that the mean distance of two nucleons in the Kpp is found to be ~2.2 fm which is almost equal to the NN distance in normal nuclear matter. (In the figure, a result obtained with non-relativistic kinematics is shown.) In the talk, we will report further results obtained with other versions of KN potential and those in the semi-relativistic kinematics. We hope to discuss on comparison of our result and the J-PARC experimental results.