Search for the Weak Decay of an $H$ Dibaryon

We have searched for a neutral $H$ dibaryon decaying via $H\to \Lambda n$ and $H\to {\Sigma }^{0}n$. Our search has yielded two candidate events from which we set an upper limit on the $H$ production cross section. Normalizing to the inclusive $\Lambda$ production cross section, we find $\frac{\left(\frac{d{\sigma }_H}{d\Omega }\right)}{\left(\frac{d{\sigma }_{\Lambda }}{d\Omega }\right)}<6.3\mathrm{}\times {10}^{-6\mathrm{}}$ at 90% C.L., for an $H$ of mass ≈2.15 GeV/${\mathit{c}}^2$.