Leon Lederman, a Columbia physicist and future director of Fermilab, leads from the early 1970s onward an ambitious experimental program at the Batavia, Illinois laboratory, dedicated to studying muon pairs produced in high-energy proton collisions against fixed nuclear targets. The goal is to search for new resonances — peaks in the muon-pair mass distribution that would reveal the existence of hitherto unknown particles — following the discovery of the charm quark in 1974. After several earlier attempts with ambiguous results, experiment E288, now with a far more sophisticated detector, begins taking data in May 1977. Within weeks, the team — led in the publication by Stephen W. Herb — observes a clear bump in the dimuon mass distribution around 9.5 GeV, published in August 1977 in "Observation of a Dimuon Resonance at 9.5 GeV in 400-GeV Proton-Nucleus Collisions". Lederman announces the finding, named "upsilon" (Υ), at the 1977 summer conferences in Budapest and Hamburg. With more statistics, by September the bump actually resolves into three separate peaks, confirmed shortly after in independent experiments at DESY in Hamburg and at CERN. The correct interpretation, which would be consolidated in the following months, is that the upsilon is a bound state of a bottom (b) quark and its antiquark — the first third-generation quark to be detected, and the heavy counterpart, within the "down-type" quark family, of the strange quark and the down quark. The finding occurs the same year, independently, that Martin Perl confirms at SLAC the discovery of the tau lepton (see separate entry perl-tau-lepton-discovery-1975): together, both results are the first solid experimental evidence that a complete third generation of elementary particles exists, beyond the two known until then (electron/muon and their respective quarks and neutrinos), confirming what Kobayashi-Maskawa theory had predicted a few years earlier to explain CP violation.