Prof. Soeren Andre Prell (Iowa State University (US))
We present a set of new results in tau-lepton physics using the full BABAR data set. This includes a new limit on the branching fraction of the isospin-forbidden, second-class-current decay tau --> pi eta'(958) nu_tau; a first study of high-multiplicity tau decays with charged kaons; and measurements of the branching fractions of 3- and 5-prong tau decays. Using the full BABAR dataset, we measure the branching fractions of the decays tau --> h (npi0) and h Ks Ks(pi0), where h indicates a charged kaon or pion and n may be up to 3. We also report the invariant-mass distributions of the decays tau -> pi pi pi nu, tau -> K pi pi nu, tau -> K K pi nu, and tau -> K K K nu, where events with Ks → pi+ pi- decays are excluded. We use these measurements to update the value of the magnitude of the CKM matrix element Vus. Within the standard model, tau-lepton decays conserve CP, so searches for CP violation in this system are sensitive to new physics. We report the results of a search for CP violation in the decay tau- --> pi - Ks nu using the full BABAR data set. In this mode a decay-rate asymmetry of (0.36 +/- 0.01)%. is expected within the standard model due to CP violation in the neutral kaon system. After accounting for effects due to the different interaction cross sections of K0 and anti-K0 mesons with the detector material, we find a decay-rate asymmetry of (-0.36 +/- 0.23 +/- 0.11)%, approximately 2.8 standard deviations from the standard model expectation.