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HFLAV $τ$ branching fractions fit and measurements of Vus with $τ$ lepton data

by Alberto Lusiani

This is not the latest submitted version.

This Submission thread is now published as SciPost Phys. Proc. 1, 001 (2019)

Submission summary

As Contributors: Alberto Lusiani
Arxiv Link: (pdf)
Date submitted: 2018-11-16 01:00
Submitted by: Lusiani, Alberto
Submitted to: SciPost Physics Proceedings
Proceedings issue: The 15th International Workshop on Tau Lepton Physics (Amsterdam, 2018-09)
Academic field: Physics
  • High-Energy Physics - Experiment
Approach: Experimental


We report the status of the Heavy Flavour Averaging Group (HFLAV) averages of the $\tau$ lepton measurements We then update the latest published HFLAV global fit of the $\tau$ lepton branching fractions (Spring 2017) with recent results by BABAR. We use the fit results to update the Cabibbo-Kobayashi-Maskawa (CKM) matrix element Vus measurements with the $\tau$ branching fractions. We combine the direct $\tau$ branching fraction measurements with indirect predictions using kaon branching fractions measurements to improve the determination of Vus using $\tau$ branching fractions. The Vus determinations based on the inclusive branching fraction of $\tau$ to strange final states are about $3\sigma$ lower than the Vus determination from the CKM matrix unitarity.

Current status:
Has been resubmitted

Submission & Refereeing History

Published as SciPost Phys. Proc. 1, 001 (2019)

Resubmission 1811.06470v2 on 17 December 2018

Reports on this Submission

Anonymous Report 1 on 2018-12-8 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:1811.06470v1, delivered 2018-12-08, doi: 10.21468/SciPost.Report.720


The paper describes the latest average result of $|V_{us}|$ determined with the $\tau$ lepton decay branching fractions from the Heavy Flavor Averaging Group. The new result has been compared with the value obtained from CKM matrix unitarity, with the new measurements from $\tau$ decays, the discrepancy has been reduced slightly.

The quality of the paper is high, minor corrections to the content would further improve it.
This paper is an important contribution to the field of tau physics and I recommend it for publication.

Requested changes

1. Introduction: "two BABAR measurement"->"two BABAR measurements"; "fit input measurements three tau"->"fit input measurements of three tau"
2. Chapter2: better to keep three decimal places for the uncertainties of the branching fractions of $\tau\to K/\pi (n)\pi^0\nu_{\tau}$
3. Chapter3: "is superseded"->"has been superseded"
4. References: blank space is missing between the journal and the volume; [15] is published in Phys. Lett. B 781, 202-212 (2018)

  • validity: -
  • significance: -
  • originality: -
  • clarity: -
  • formatting: -
  • grammar: -

Author:  Alberto Lusiani  on 2018-12-14  [id 387]

(in reply to Report 1 on 2018-12-08)

Regarding point 4, I checked the bibliography references and found that there are spaces between the journal and volume numbers. I am using the SciPost bibliography style, which uses the common convention that for journals like Phys.Rev.D the "D" is attached to the volume number. I think that that should stay so for SciPost proceedings.

I attach the PDF of the revision I posted to



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