Search for pentaquarks at Belle

TL;DR

This study searches for strange pentaquarks in Belle detector data, finding no evidence for $ heta^+$ but setting upper limits on its production relative to known particles, and also exploring pentaquarks in B decays.

Contribution

First search for $ heta^+$ pentaquark in kaon interactions at Belle, establishing upper limits and exploring pentaquark production in B meson decays.

Findings

No $ heta^+$ signal observed in $p K_S$ final state.

Approximately 16,000 $ ext{Λ}(1520) o p K^-$ decays detected.

Upper limit set: $ heta^+$ to $ ext{Λ}(1520)$ yield ratio < 2% at 90% CL.

Abstract

We search for the strange pentaquark $\Theta^+$ using kaon interactions in the material of the Belle detector. No signal is observed in the $p K_S$ final state, while in the $p K^-$ final state we observe $\sim 1.6 \cdot 10^4$ $\Lambda(1520) \to p K^-$ decays. We set an upper limit on the ratio of $\Theta^+$ to $\Lambda(1520)$ yields $\sigma(\Theta^+) / \sigma(\Lambda(1520)) < 2%$ at 90% CL assuming that the $\Theta^+$ is narrow. We also report on searches for strange and charmed pentaquarks in B meson decays. These results are obtained from a 155$fb^{-1}$ data sample collected with the Belle detector near the $\Upsilon(4S)$ resonance, at the KEKB asymmetric energy $e^+ e^-$ collider.