Search for Light Gluinos via the Spontaneous Appearance of ${\mathit{\pi }}^{+}{\mathit{\pi }}^{-}$ Pairs with an $800\mathrm{GeV}/\mathit{c}$ Proton Beam at Fermilab

We searched for the appearance of ${\pi }^{+}{\pi }^{-}$ pairs with invariant mass $\ge 648\mathrm{MeV}{/c}^2$ in a neutral beam. Such an observation could signify the decay of a long-lived light neutral particle. We find no evidence for this decay. Our null result severely constrains the existence of an $R^0$ hadron, which is the lightest bound state of a gluon and a light gluino $\left(g\tilde{g}\right)$, and thereby also the existence of a light gluino. Depending on the photino mass, we exclude the $R^0$ in the mass and lifetime ranges of $1.2–4.6\mathrm{GeV}{/c}^2$ and $2\times {10}^{-10\mathrm{}}–7\times {10}^{-4\mathrm{}}\mathrm{s}$, respectively.