1. Measurement of the mesonic decay branch of the $\bar{K}\!N\!N$ quasi-bound state
- Author
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Yamaga, T., Ajimura, S., Asano, H., Beer, G., Bhang, H., Bragadireanu, M., Buehler, P., Busso, L., Cargnelli, M., Choi, S., Curceanu, C., Enomoto, S., Fujioka, H., Fujiwara, Y., Fukuda, T., Guaraldo, C., Hashimoto, T., Hayano, R. S., Hiraiwa, T., Iio, M., Iliescu, M., Inoue, K., Ishiguro, Y., Ishikawa, T., Ishimoto, S., Itahashi, K., Iwai, M., Iwasaki, M., Kanno, K., Kato, K., Kato, Y., Kawasaki, S., Kienle, P., Kou, H., Ma, Y., Marton, J., Matsuda, Y., Mizoi, Y., Morra, O., Murayama, R., Nagae, T., Noumi, H., Ohnishi, H., Okada, S., Outa, H., Piscicchia, K., Sada, Y., Sakaguchi, A., Sakuma, F., Sato, M., Scordo, A., Sekimoto, M., Shi, H., Shirotori, K., Sirghi, D., Sirghi, F., Suzuki, S., Suzuki, T., Tanida, K., Tatsuno, H., Tokuda, M., Tomono, D., Toyoda, A., Tsukada, K., Doce, O. Vazquez, Widmann, E., Yamazaki, T., Yim, H., Zhang, Q., and Zmeskal, J.
- Subjects
Nuclear Experiment ,Nuclear Theory - Abstract
We conducted measurements of $K^- + {^3{\rm He}} \to \pi \!Y \!N + N'$ reactions using a $1~{\rm GeV}/c$ $K^-$-beam, with the objective of understanding the broad decay width of $\bar{K} \!N \!N$ (approximately twice as broad as that of $\Lambda(1405)$ considered to be the $\bar{K} \!N$ quasi-bound state). We successfully reproduced distributions of the $\pi \! Y \! N$ invariant mass and momentum transfer for $\pi \! Y \! N$ using model fitting functions for $\bar{K} \!N \!N$ formation and quasi-free $\bar{K}$ absorption (${\rm QF}_{\bar{K}-{\rm abs}}$) processes. The model can describe the experimental data quite well, and four $\bar{K} \! N \! N \to \pi \! Y \! N $ cross-sections were obtained. The results indicate that mesonic decay is the dominant decay branch of $\bar{K} \! N \! N$. The results also suggest that $\Gamma_{\pi \Lambda N} \sim \Gamma_{\pi \Sigma N}$, which indicates that the $I_{\bar{K} \! N}=1$ absorption channel, in addition to the $I_{\bar{K} \! N}=0$ absorption channel, substantially contribute to the $\bar{K} \! N \! N$ decay, making the $\bar{K} \! N \! N$ state approximately twice as unstable as $\Lambda$(1405).
- Published
- 2024