Physics of the tau lepton

TL;DR

The tau lepton, as the heaviest lepton decaying into hadrons, offers a unique environment to study QCD phenomenology, flavor dynamics, and potential new physics, serving as a crucial benchmark in particle physics research.

Contribution

This paper reviews the rich phenomenology of the tau lepton, emphasizing its role in studying QCD, flavor symmetry, and probing for new physics beyond the Standard Model.

Findings

Tau decays provide insights into hadronization of QCD currents.

Tau lepton's properties serve as a benchmark for low-energy QCD studies.

The tau's behavior constrains flavor dynamics and searches for new physics.

Abstract

Within our present knowledge, the tau is the heaviest lepton and the only one decaying into hadrons, a fact that makes it the source of a very rich phenomenology. It represents the third family of leptons in the Standard Model, a feature that helps its classification but whose real meaning is not asserted yet. The tau lepton provides: i) a clean and unique environment to study both the hadronization of QCD currents, in an energy region populated by resonances, and the phenomenological determination of relevant parameters of the Model; ii) together with the muon, they have a very constrained flavour dynamics (in the absence of neutrino masses) due to an accidental global symmetry of the Standard Model. In consequence, the tau lepton brings an excellent benchmark for the study of QCD at low energies and, at the same time, for the search of new physics.