Studies of three-and four-body hypernuclei with heavy-ion beams, nuclear emulsions and machine learning

Interests on few-body hypernuclei have been increased by recent results of experiments employing relativistic heavy ion beams. Some of the experiments have revealed that the lifetime of the lightest hypernucleus, hypertriton, is significantly shorter than 263 ps which is expected by considering the hypertriton to be a weakly-bound system. The STAR collaboration has also measured the hypertriton binding energy, and the deduced value is contradicting to its formerly known small binding energy. These measurements have indicated that the fundamental physics quantities of the hypertriton such as its lifetime and binding energy have not been understood, therefore, they have to be measured very precisely. Furthermore, an unprecedented Lambda nn bound state observed by the HypHI collaboration has to be studied in order to draw a conclusion whether or not such a bound state exists. These three-body hypernuclear states are studied by the heavy-ion beam data in the WASA-FRS experiment and by analysing J-PARC E07 nuclear emulsion data with machine learning.