Graduation date: 2007This study examines the interactions between the scientific communities of the Lawrence Berkeley Laboratory (LBL) and the Stanford Linear Accelerator Center (SLAC) in the discovery of the tau lepton by physicist Martin Perl between 1973- 1977. Perl became interested in searching for heavy leptons through positron-electron collision experiments using the newly constructed Mark I detector at SLAC, and his search resulted in the discovery of the tau lepton. Although the experiments responsible for the discovery of this new particle were part of a collaborative effort between SLAC and LBL, Perl became known for his individual role in interpreting the data and was awarded the Nobel Prize in physics for his work in 1995. Drawing upon personal and professional papers from the SLAC Archives and History Office, the LBL Archives and Records Office, and personal communications from the physicists involved in the discovery, I argue that the discovery of the tau lepton challenges many of the common generalizations regarding the practice of “Big Science.” Big Science has often been associated with a transformation in the life of the experimenter as individual autonomy was subsumed by a ‘factory’ work style typified by teamwork on a massive scale. However, an examination of the discovery of the tau lepton reveals that physicists at SLAC worked in small research groups, enjoyed great scientific freedom, and maintained a direct and interactive role in shaping research. This study also illustrates how scientific ambition motivates decisions underlying priority and discovery, which is highlighted by Perl’s rush to publicize his findings in order to establish priority.