Speaker
Description
Kaonic nuclei are exotic few-body systems in which an antikaon is bound as a constituent particle. They provide a unique testing ground for the strongly attractive subthreshold $\bar{K}N$ interaction and the resulting few-body dynamics. In the J-PARC E15 experiment, the simplest candidate, the ''$K^-pp$'' state, was observed as a structure in the $\Lambda p$ invariant-mass spectrum of the in-flight $K^-$ reaction on a helium-3 target, demonstrating the importance of complete kinematic reconstruction with a large-acceptance solenoid spectrometer.
We are now extending this program. With an upgraded solenoid spectrometer, J-PARC E80 will investigate the ''$K^-ppn$'' system using a helium-4 target, while E89 will determine the spin parity of ''$K^-pp$'' and search for its isospin partner, ''$\bar{K}^{0}nn$''. In parallel, we plan ultra-high-precision X-ray spectroscopy of light kaonic atoms, with particular emphasis on isotope differences, to provide precise constraints on the antikaon--nucleus interaction in the low-density nuclear surface region.
In this contribution, we review our achievements over the past decade and discuss future prospects for these complementary studies.
