STATUS OF THE WASA-FRS HypHI EXPERIMENT: STUDY OF LIGHT HYPERNUCLEI AT GSI-FAIR

Even though the hypernuclei, which are sub-atomic nuclei that contain the quark s, have been studied with nuclear emulsions for more than 50 years, their current understanding has been challenged in recent years by experiments using high-energy heavy-ion beams. Firstly, the significantly shorter hypertriton lifetime reported by three independent state-of-the-art experiments, namely ALICE, STAR, and HypHI, compared to the predictions of theoretical models was poorly understood for some time. Notwithstanding, the current status of the hypertriton puzzle is evolving with the latest experimental efforts. Secondly, the observed enhancement in the invariant mass distributions of the t + π− and d + π− final states, as reported by the HypHI Collaboration, cannot be accounted for by existing theoretical calculations, which indicate the absence of a neutral nnΛ bound state. Consequently, the WASA-FRS HypHI Experiment aims at obtaining new accurate results for the invariant mass and lifetime of3ΛH and4ΛH to produce more precise and statistically significant experimental results that can provide clarification on the potential existence of nnΛ. This experiment was successfully conducted in 2022 at GSI-FAIR. Data analysis is still ongoing, while several preliminary results are reported. © 2024 Jagiellonian University. All rights reserved.