Current Results on Light Hypernuclei in the WASA-FRS HypHI Experiment

Abstract

The current understanding of light hypernuclei, subatomic nuclei exhibiting strangeness, is being actively investigated by several collaborations. Recent studies employing high-energy heavy-ion beams have revealed unexpected results for the three-body bound state ${}_{\Lambda }^3$H, known as the hypertriton. Experimental measurements of its lifetime and binding energy across multiple experiments have produced a puzzling situation referred to as the ``hypertriton puzzle''. This puzzle is the central focus of the data analysis from the WASA-FRS HypHI experiment at GSI-FAIR within the SuperFRS Experiment collaboration. Light hypernuclei are being investigated using 1.96 GeV/u ${}^6$Li beams impinging on a fixed carbon target, in conjunction with the WASA detector system and the Fragment Separator (FRS) at GSI-FAIR. The WASA-FRS experimental campaign was carried out during the first quarter of 2022. The primary objective of the experiment is to measure the lifetimes of ${}_{\Lambda }^3$H and ${}_{\Lambda }^4$H. The possible observation of the nn$\Lambda$ state constitutes the second component of the WASA-FRS research program. This contribution provides an overview of our investigation of hypernuclei. Focusing on the WASA-FRS HypHI experiment, details of the current analysis status are presented.

arXiv commentProceedings of the 15th International Conference on Hypernuclear and Strange Particle Physics (HYP2025), Tokyo (Japan), 29 September 2025 - 3 October 2025. To be published in JPS Conf. Proc