B-Meson Decays into Final States with a tau Lepton

Understand

Decays of B mesons into final states containing a tau lepton are sensitive to new charged-current interactions that break lepton-flavor universality.

• These decays have been studied only at e+e- colliders, where the low-background environment and well-known initial state make it possible to observe small signals with undetectable neutrinos.
• In particular, the large data samples of the B factories and recent advances in techniques for full-event reconstruction have led to evidence for the decay B --> tau nu and unambiguous observation of the decays B --> D(*)tau nu.
• These results have led to exclusion of large regions of the parameter space for a variety of new-physics models.