Letter a claim was made by the authors for the discovery of something new, but they held back from stating that it was a new lepton. It was a long path involving many additional studies by Perl's group and by many others until other explanations of the results could be eliminated and a clear case made for the discovery of what was named the tau lepton and its associated neutrino. This "third generation" of leptons was followed also by a third generation of quarks, a parallel development for hadrons. The 1995 Nobel Prize in Physics was awarded "for pioneering experimental contributions to lepton physics" to Martin Perl ("for the discovery of the tau lepton") and to Frederick Reines ("for the detection of the Neutrino"). The latter's research was first published in Physical Review in 1953 [ Phys. Rev. 92, 830 (1953) ], prior to the establishment of Physical Review Letters. See the Focus story Phys. Rev. Focus 19, story 13 for a description of this work. For further information see the Nobel press release and a recent essay by Martin Perl in Physical Review Letters. See the articles or the additional information for a complete list of the authors. The research reported in these Letters described the observation of a new long-lived particle that engendered considerable excitement among particle physicists. The observation was accomplished by two different routes. The J particle was observed in an experiment using high energy protons which produced e + e - pairs as a product