τ Decays to kaons from ALEPH and physics implications

Abstract In this talk, preliminary updated results for one-prong τ decays with kaons in ALEPH are presented. Then all ALEPH measurements of branching ratios of τ decays involving kaons are summarized. Mass spectra for different isospin states are studied to address the relevant decay dynamics and also used to separate the vector and axial-vector current contributions. Agreement with isospin symmetry is observed among the different final states. Through the CVC hypothesis, the spectral function for the K K − π mode is compared with the corresponding cross section from low energy e + e − annihilation, yielding an axial-vector fraction of (94 −8 +6 )% in this mode. Finally, the branching ratio for all strange τ decays is determined to be B ( τ − → X − ( S = −1) ν τ ) = (28.6±1.2) × 10 −3 , and the corresponding S = −1 spectral function is derived from the measured mass spectra as well.