Measurement of $^{3,4}$He($K^-, Ï^0$)$^{3,4}_Î$H reaction cross section and evaluation of hypertriton binding energy
T. Akaishi, H. Asano, X. Chen, A. Clozza, C. Curceanu, R. Del Grande, C. D. Han, T. Hashimoto, M. Iliescu, K. Inoue, S. Ishimoto, K. Itahashi, M. Iwasaki, Y. Ma, R. Murayama, H. Noumi, H. Ohnishi, S. Okada, H. Outa, K. Piscicchia, A. Sakaguchi, F. Sakuma, M. Sato, A. Scordo, K. Shirotori, D. Sirghi, F. Sirghi, S. Suzuki, K. Tanida, T. Toda, T. Yamaga, X. Yuan, P. Zhang, Y. Zhang, H. Zhang
Published: 2025/9/21
Abstract
Light $s$-shell hypernuclei ($^{3,4}_{\Lambda}\text{H}$) and their ground-state properties are crucial benchmarks in hypernuclear physics. In particular, comparing the production cross sections of $^{3}_{\Lambda}\text{H}$ and $^{4}_{\Lambda}\text{H}$ provides insights into the $\Lambda N$ interaction in different isospin configurations, which can help address recent discrepancies in the reported binding energy of hypertriton. We present the first measurement of the production cross sections for $^{3}_{\Lambda}\text{H}$ and $^{4}_{\Lambda}\text{H}$ using the in-flight $(K^-, \pi^0)$ reaction at a beam momentum of 1.0 GeV/$c$ with an identical experimental setup. The production cross sections in the laboratory frame, for the angular range from 0$^{\circ}$ to 20$^{\circ}$, are measured to be: $15.0~\pm~2.6~(\text{stat.})~^{+2.4}_{-2.8}~(\text{syst.})~\mu \text{b} $ and $50.7~\pm~2.1~(\text{stat.})~^{+7.8}_{-8.3}~(\text{syst.})~\mu \text{b}$, respectively. Using the ratio of the cross sections and comparing the ratio with theoretical calculations, we evaluate the hypertriton binding energy to be $0.061\ ^{+0.028}_{-0.022}\ (\text{stat.})\ ^{+0.024}_{-0.021}\ (\text{syst.})\ \text{MeV}$.