Speaker
Description
It has been argued that the formation of a molecular-like quasi-bound state, $\Lambda(1405)$, arises from the strong attraction between $\overline{K}N$ with isospin I = 0 channel. Furthermore, its strong attraction suggests the existence of kaonic nuclei in a three-body system, $K^{-}pp$, as well as in more complex many-body systems.
Some calculations suggest existence of various types of many-body systems involving Kaon and nucleons. However, apart from the observation of the $K^{-}pp$ three-body system[1][2], there have been few clear confirmations for the existence of Kaonic nuclei. Therefore, it is crucial to systematically investigate Kaonic nuclei across a wide range of mass numbers not only for understanding $\overline{K}N$ interactions but also for obtaining information on the presence or absence of $\overline{K}$ within the inner core region of neutron stars.
The J-PARC E05 experiment studied the interaction between $\overline{K}$ and a residual nucleus by measuring an inclusive $^{12} \text{C} (K^{-}, p)$ spectrum. From the analysis, the depths of both the real and imaginary parts of the $\overline{K}$-nucleus optical potential were obtained to be (-80, 40) [MeV] by fitting the shallow bound region with a theoretically calculated spectrum[3]. In addition, a significant event excess was observed in the spectrum in the deeply bound region around 90 MeV in the $\overline{K}$ binding energy. That excess fits well with a Breit-Wigner function whose binding energy is 90 MeV and width is 100 MeV, suggesting possible contribution from production of $\overline{K}NN$ or a bound state between an excited hyperon $(Y^{＊})$ and a nucleus.
To investigate the reason behind the excess event, we conducted a new experiment called E42[4]. This experiment used the same reaction, $^{12} \text{C} (K^{-}, p)$, as a byproduct of the H-dibaryon search experiment. We used a GEM-based Time Projection Chamber, HypTPC, installed around the target to measure the decay-charged particles during this experiment. This measurement technique helped improve the signal-to-noise ratio and allowed us to detect the $Y^{＊}$ nuclear state as a clear bump if it exists.
In this talk, we will summarize the E05 results and report preliminary results of the inclusive $^{12}\text{C}(K^{-}, p)$ spectrum and the exclusive analysis using the information on particle identification with HypTPC.
Reference
[1] S. Ajimura et al. Phys. Let. B 789 (2019) 620-625
[2] T. Yamaga et al. Phys. Rev. C 102, 044002 (2020)
[3] Y. Ichikawa et al., PTEP 2020, 123D01 (2020)
[4] J.K. Ahn et al., the proposal of J-PARC E42 experiment, Search for H-Dibaryon with a Large Acceptance Hyperon Spectrometer
| session | J. Strange Nuclear Systems |
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