A review is presented of experimental data that provide evidence for the existence of a heavy charged lepton $\tau^\pm$. The properties of the $\tau$ particle extracted from experimental data are compared with theoretical expectations. A summary of necessary further measurements is provided. The possible theoretical significance of the new particle is briefly discussed.

@article{Azimov:1978,
	author = {Ya. I. Azimov and L. L. Frankfurt and V. A. Khoze},
	title = {New particle in e+e– annihilation: the heavy lepton τ±},
	publisher = {Physics-Uspekhi},
	year = {1978},
	journal = {Phys. Usp.},
	volume = {21},
	number = {3},
	pages = {225-239},
	url = {https://ufn.ru/en/articles/1978/3/d/},
	doi = {10.1070/PU1978v021n03ABEH005530}
}