The tau lepton (τ) is a third-generation lepton, similar to the electron and muon, but significantly heavier—about 3,500 times more massive than the electron. Like the electron, it carries a negative electric charge and has a corresponding neutrino, the tau neutrino (νₜ).
Key characteristics of tau leptons:
- They are fundamental particles, not made of smaller constituents.
- Due to their large mass, taus are unstable and decay quickly—within about 10⁻¹³ seconds.
- They decay into lighter particles, often producing combinations of electrons, muons, neutrinos, and hadrons (such as pions or kaons).
The tau’s mass makes it capable of interacting with both leptons and hadrons during decay, providing a rich variety of decay modes. This diversity makes the tau lepton important in:
- Testing lepton universality in particle physics,
- Searching for new physics, such as lepton flavor violation or supersymmetry,
- And probing Higgs boson decays, since the Higgs can decay into a tau pair.
Despite being short-lived, tau leptons play a key role in experiments at particle colliders, where their complex decays can reveal deeper insights into the fundamental forces and potential extensions of the Standard Model.