Search for $\hat{I}{ž}^{0}p$, $\hat{I}{\text{c◯}}^{-}p$, and $\hat{I}{\text{c◯}}^{-}n$ dibaryons in $\hat{I}\yen (1S)$ and $\hat{I}\yen (2S)$ decays at Belle

Abstract

We search for $\hat{I}{ž}^{0}p$, $\hat{I}{\text{c◯}}^{-}p$, and $\hat{I}{\text{c◯}}^{-}n$ dibaryon states in $\hat{I}\yen (1S)$ and $\hat{I}\yen (2S)$ decays, probing mass regions near the corresponding baryon-pair thresholds. Multistrange baryon-baryon interactions are relevant to neutron-star matter but remain largely unconstrained. Experimental and theoretical studies supporting attractive $\hat{I}žN$ and $\hat{I}\text{c◯}N$ interactions, where $N$ denotes a nucleon, motivate searches for weakly bound states. We use samples of $102$ million $\hat{I}\yen (1S)$ and $158$ million $\hat{I}\yen (2S)$ decays collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. No significant signals are observed, and the first $90$% confidence-level upper limits are set on the branching fractions of $\hat{I}\yen (1S)$ and $\hat{I}\yen (2S)$ decays to $\hat{I}{ž}^{0}p$, $\hat{I}{\text{c◯}}^{-}p$, and $\hat{I}{\text{c◯}}^{-}n$ dibaryon states, at the level of $O(10^{-7})$-$O(10^{-6})$, depending on the channel and the assumed mass difference from the corresponding baryon-pair threshold.

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