Speaker
Description
We report preliminary results from $\Lambda\Lambda$ invariant-mass spectroscopy in the $^{12}\mathrm{C}(K^-,K^+)$ reaction to search for the H-Dibaryon near the $\Lambda\Lambda$ and $\Xi^-p$ thresholds at J-PARC. The experiment employs a $1.8~\mathrm{GeV}/c$ $K^-$ beam incident on a diamond target and a large-acceptance hyperon spectrometer centered on a time-projection chamber (HypTPC). This setup provides sensitivity over a broad mass region, ranging from weakly bound states below the $\Lambda\Lambda$ threshold to possible structures above the $\Xi^-p$ threshold.
A total of approximately $3.0\times10^{5}$ $^{12}\mathrm{C}(K^-,K^+)X$ reaction events were collected, yielding several thousand $\Lambda\Lambda$ events-about two orders of magnitude more than in previous experiments. In the $(K^-,K^+)$ reaction on a nuclear target, $\Lambda\Lambda$ production proceeds through interactions on di-protons inside the nucleus. The production mechanisms include intermediate $\Xi^-$ formation as well as meson-induced two-step processes, such as
$K^-p \rightarrow \Xi^-K^+$ followed by $\Xi^-p \rightarrow \Lambda\Lambda$, and $K^-p \rightarrow \pi^0\Lambda$ followed by
$\pi^0p \rightarrow \Lambda K^+$.
In our earlier work, we measured the differential cross section for the $^{12}\mathrm{C}(K^-,K^+\Lambda\Lambda)$ reaction and separated the contributions from the $\Xi^-p \rightarrow \Lambda\Lambda$ conversion and meson-induced two-step processes~\cite{ref1}. Based on these results, we have carried out invariant-mass spectroscopy of the $\Lambda\Lambda$ system to investigate the possible existence of the H-Dibaryon near threshold and to gain further insight into the $\Lambda\Lambda$-$\Xi N$ interaction. In this presentation, we will show preliminary results of the H-Dibaryon search and discuss its nature.
