HFAG-Tau Summer 2016 Report

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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 3) and of the Cabibbo-Kobayashi-Maskawa (CKM) matrix coefficient |Vus| from τ decays (Section 5). We concentrate our effort in the averages that benefit most from the adoption of the HFAG methodology [1], namely a global fit of the τ branching fractions that best exploits the available experimental information. Since the 2016 edition, the HFAG-Tau group has collaborated to the publication of the PDG τ lepton branching fraction fit and mini-review. The differences between the PDG 2016 fit and the fit presented here are detailed in Section 2.4.

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

Finally, we report in Section 6 the most up-to-date limits on the lepton-flavour-violating τ branching fractions and in Section 8 we determine the combined upper limits for the branching fractions that have multiple experimental results.


HFAG-Tau Summer 2016 Report

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