Search for Light Gluinos via the Spontaneous Appearance of π+π- Pairs with an 800 GeV/c Proton Beam at Fermilab

We searched for the appearance of π⁺π^- pairs with invariant mass ≥648MeV/c² 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 R⁰ hadron, which is the lightest bound state of a gluon and a light gluino (g ̃ \~g), and thereby also the existence of a light gluino. Depending on the photino mass, we exclude the R⁰ in the mass and lifetime ranges of 1.2--4.6GeV/c² and 2×10^-10--7×10^-4s, respectively.