Because of its short lifetime, the range of the tau is mainly set by its decay length, which is too small for bremsstrahlung to be noticeable.

Zichichi came up with the idea of a new sequential heavy lepton, now called tau, and invented a method of search.

[10] Providing the theory for this discovery, the tau was detected in a series of experiments between 1974 and 1977 by Martin Lewis Perl with his and Tsai's colleagues at the Stanford Linear Accelerator Center (SLAC) and Lawrence Berkeley National Laboratory (LBL) group.

[1] Their equipment consisted of SLAC's then-new electron–positron colliding ring, called SPEAR, and the LBL magnetic detector.

The mass and spin of the tau were subsequently established by work done at DESY-Hamburg with the Double Arm Spectrometer (DASP), and at SLAC-Stanford with the SPEAR Direct Electron Counter (DELCO), The symbol τ was derived from the Greek τρίτον (triton, meaning "third" in English), since it was the third charged lepton discovered.

[citation needed] Another one is an onium atom τ+τ− called ditauonium or true tauonium, which is a challenge to detect due to the difficulty to form it from two (opposite-sign) short-lived tau leptons.