A method to reconstruct Σ+→p+π0 decays

A method has been conceived to identify and reconstruct Σ+ baryons decaying into p and π0 particles, in hadronic Z0 decays at LEP. It is designed for the case where the charged track of the Σ+ is not observed. The unobserved decay vertex of the Σ+ is reconstructed using the spatial trajectory of the proton and the energy and angle of the two photons from the π0 decay. A significant improvement in the resolution of the decay vertex is obtained when the curvature of the Σ+ track is taken into account.