Probing top quark decay into light stop in the supersymmetric standard model at the upgraded Tevatron

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We investigate the possibility of observing the exotic decay mode of the top quark into the lightest stop (t₁) and neutralino (χ⁰₁) in the minimal supersymmetric standard model with R-parity at the upgraded Tevatron. First we determine the allowed range for the branching fraction B(t→ t₁ χ⁰₁) in the region of parameter space allowed by the Rb data and the CDF eeγγ+ Eₜ event, and then consider all possible backgrounds and investigate the possibility of observing this final state at the Tevatron. We find that this final state is unobservable at Run 1. However, Run 2 can provide significant information on this new decay mode of the top quark: either discover it, or establish a strong constraint on the masses of t₁ and χ⁰₁ given approximately by M χ⁰₁ > M t₁ - 6 GeV.