Pentaquark Search and Other Multiquark Candidates at BES

Abstract

Results are presented on $\psi(2S)$ and $J/\psi$ hadronic decays to $K^0_SpK^-\bar n$ and $K^0_S\bar p K^+n$ final states from data samples of 14 million $\psi(2S)$ and 58 million $J/\psi$ events accumulated at the BES II detector. No $\Theta(1540)$ signal, the pentaquark candidate, is observed, and the upper limits are set. We also present a narrow enhancement near $2m_p$ in the invariant mass spectrum of $p \bar{p}$ pairs from $J/\psi \to \gamma p \bar{p}$ decays, an enhancement near the $m_p + M_{\Lambda}$ mass threshold and an enhancement near the $m_K + m_{\Lambda}$ mass threshold from $J/\psi \to p K^- \bar{\Lambda} + c.c.$ decays, based on 58 million $J/\psi$ events.