Decay of the loosely bound or resonant Lambda Lambda -bar state and comparison with recent experimental data.

Abstract

The decay of the narrow state \ensuremath{\xi}/X(2.2) observed by the Mark III and GAMS groups is studied, assuming that it is a loosely bound or resonant \ensuremath{\Lambda}\ensuremath{\Lambda}\ifmmode\bar\else\textasciimacron\fi{} state. The branching ratios of the decay into two nonstrange mesons and to \ensuremath{\eta}\ensuremath{\eta}, \ensuremath{\eta}\ensuremath{\eta}', and to \ensuremath{\varphi}\ensuremath{\varphi} are calculated in the $^{3}\mathrm{P}_{0}$ model or the quark-annihilation model with two qq\ifmmode\bar\else\textasciimacron\fi{} pair annihilations and one qq\ifmmode\bar\else\textasciimacron\fi{} pair creation. The \ensuremath{\xi}(2.2) with the quantum number $^{3}\mathrm{P}_{2}$ is not in conflict with the model if the coupling to the intermediate ss\ifmmode\bar\else\textasciimacron\fi{} and to the intermediate (u\ifmmode \bar{u}\else \={u}\fi{}+dd\ifmmode\bar\else\textasciimacron\fi{})/ \ensuremath{\surd}2 are different, which is suggested by the flux-tube model and the ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$\ensuremath{\rightarrow}hadron jets experiment. X(2.2) with the quantum number $^{3}\mathrm{P}_{0}$ can also be a loosely bound \ensuremath{\Lambda}\ensuremath{\Lambda}\ifmmode\bar\else\textasciimacron\fi{} but in the decay the quark rearrangement with one qq\ifmmode\bar\else\textasciimacron\fi{} pair annihilation may also play a role in this state.