Following up the APS milestone about the 1974 papers that heralded the discovery of the J/Ψ, the paper chosen to represent 1975 was for work also done on the SPEAR storage ring at Stanford Linear Accelerator Center and also led to a Nobel Prize in physics, this time for SLAC's Martin Perl.
You can read past-editor-in-chief of Physical Review Marty Blume's commentary and then click through to read the original paper. The paper itself doesn't claim discovery of the tau lepton but was the first key step in the process. For the very first symmetry magazine logbook, we published a reproduction of Perl's hand-drawn graph of the data that led to this paper.
