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

We search for double anti-kaon nuclear bound states in the (p) over bar annihilation reaction in He-3 nuclei at rest. In view of the strongly attractive (K) over barN 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 antikaon production in the nuclei. In order to investigate the K-K- pp production in the (p) over bar +(3) He --> K+ + K-0 + 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 Lambda-tag, and invariant mass analysis of the expected decay particles from the K-K- pp cluster such as Lambda Lambda. We propose to perform the experiment at the existing K1.8BR beam line at J-PARC with the E15 spectrometer.