ttau

ttau is a shorthand notation used in high-energy particle physics to denote final states that involve a top quark pair (tt̄) in association with a tau lepton, or more generally the tt̄τ signature in proton-proton collision events. It is not a new particle or interaction, but a labeling convention used in analyses, simulations, and plots to categorize events for precision measurements or new physics searches.

In experiments at the Large Hadron Collider, top quark pairs are produced predominantly through strong interactions. Since tau leptons can arise from W bosons produced in top decays, analyses may select events classified as tt̄τ, where one or both W bosons decay to a tau and a neutrino, and the tau subsequently decays either hadronically or leptonically. The visible final state thus contains tau decay products, missing energy, and jets from the b quarks. Different subchannels exist, such as tt̄τ_h (tau decaying hadronically) or tt̄τ_l (tau decaying leptonically), which are treated separately in event reconstruction and background estimation.

The ttau category is used to study top quark interactions with leptons, test lepton universality, and probe for physics beyond the Standard Model that enhances top–tau production. It complements other tt̄ final states, including dilepton, lepton+jets, and all-hadronic channels.

See also: Tau lepton, Top quark, Top quark pair production, LHC, Standard Model.