HFAG-Tau Summer 2014 Report

Next

1  Introduction

We present world averages of a selection of τ lepton quantities with the goal to provide the best up-to-date determinations of the tests of the universality of the charged weak interaction (Section 4) and of the Cabibbo-Kobayashi-Maskawa (CKM) matrix coefficient |Vus| from τ decays (Section 6). We concentrate our effort in the averages that most benefit from the adoption of the HFAG methodology [1], namely a global fit of the τ branching fractions that best exploits the available experimental information. We also average the τ lifetime, in order to use the recent precise Belle result [2], which has not been used by PDG until the 2014 edition.

All published statistical correlations are used, and a selection of measurements, particularly the most precise and the most recent, were studied to take into account the significant systematic dependencies from external parameters and common systematic sources.

Finally, we report in Section 7 the most up-to-date limits on the lepton-flavour-violating τ branching fractions and we determine the combined upper limits 9 for the branching fractions that have multiple experimental results.


HFAG-Tau Summer 2014 Report

Next