Experimental observation of lepton pairs of invariant mass around 95 GeV/c2 at the Cern SPS collider

Abstract We report the observation of four electron-positron pairs and one muon pair which have the signature of a two-body decay of a particle of mass ∼ 95 GeV/ c 2 . These events fit well the hypothesis that they are produced by the process p + p → Z 0 + X ( with Z 0 → l + + l − ) , where Z 0 is the Intermediate Vector Boson postulated by the electroweak theories as the mediator of weak neutral currents.