Double antikaonic nuclear clusters in antiproton-³He annihilation at J-PARC

We search for double anti-kaon nuclear bound states in the p̄ annihilation reaction in ³He nuclei at rest. In view of the strongly attractive K̄ interaction, the existence of nuclear clusters with more than one K^- has been predicted theoretically. The double anti-kaon production in elementary antiproton annihilation at rest is forbidden because of the negative Q-value; however, a double anti-kaon nuclear bound state, such as K^- K^- pp, with deep binding energy would enable double anti-kaon production in the nuclei. In order to investigate the K^- K^- pp production in the p̄+³ He → K⁺+K⁰+X (X = K^-K^-pp) channel, the produced K^- K^- pp cluster is identified both using missing mass spectroscopy via the K⁺K⁰ channel with a Λ-tag, and invariant mass analysis of the expected decay particles from the K^- K^- pp cluster such as ΛΛ. We propose to perform the experiment at the existing K1. 8BR beam line at J-PARC with the E15 spectrometer.