Observation of $\Omega (2012{)}^{-}\to \Xi (1530)\bar{K}$ and measurement of the effective couplings of $\Omega (2012{)}^{-}$ to $\Xi (1530)\bar{K}$ and $\Xi \bar{K}$

Abstract

Using ${\rm Y}(1S)$, ${\rm Y}(2S)$, and ${\rm Y}(3S)$ data collected by the Belle detector, we discover a new three-body decay, $\Omega (2012{)}^{-}\to \Xi (1530)\bar{K}\to \Xi \pi \bar{K}$, with a significance of 5.2~$\sigma$. The mass of the $\Omega (2012{)}^{-}$ is $(2012.5\pm 0.7\pm 0.5)$ MeV and its effective couplings to $\Xi (1530)\bar{K}$ and $\Xi \bar{K}$ are $(39_{-39}^{+31}\pm 9)\times 10^{-2}$ and $(1.7\pm 0.3\pm 0.3)\times 10^{-2}$, where the first uncertainties are statistical and the second are systematic. The ratio of the branching fraction for the three-body decay to that for the two-body decay to $\Xi \bar{K}$ is $0.99\pm 0.26\pm 0.06$, assuming isospin symmetry.

Comments: 6 pages, 4 figures, add more Omega(2012) three-body decay modes, updated version