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Pion electronic decay and lepton universality

by D. Počanić

This Submission thread is now published as

Submission summary

Authors (as registered SciPost users): Dinko Pocanic
Submission information
Preprint Link: scipost_202105_00017v1  (pdf)
Date accepted: 2021-06-16
Date submitted: 2021-05-12 04:57
Submitted by: Pocanic, Dinko
Submitted to: SciPost Physics Proceedings
Proceedings issue: Review of Particle Physics at PSI (PSI2020)
Ontological classification
Academic field: Physics
  • Nuclear Physics - Experiment
Approach: Experimental


In common with a number of simple processes involving elementary particles, charged pion decays are profoundly shaped by applicable Standard Model (SM) symmetries and properties. Given the highly precise SM theoretical description, pion decays are used as selective probes of SM parameters, and of possible SM extensions. The PEN experiment at PSI is studying the π + → e + ν e (γ), or π_ e2(γ) decay. The primary goal is to reach the relative precision of 5 × 10 ^{−4} in Re/μ^π, the branching ratio for π_ e2(γ) decay. We review the PEN research program, its present status, and prospects.

Published as SciPost Phys. Proc. 5, 025 (2021)

Submission & Refereeing History

Reports on this Submission

Report 2 by Adrian Signer on 2021-6-9 (Invited Report)

  • Cite as: Adrian Signer, Report on arXiv:scipost_202105_00017v1, delivered 2021-06-09, doi: 10.21468/SciPost.Report.3044


We (the editors Cy Hoffman, Klaus Kirch, Adrian Signer) had the
opportunity to review an earlier draft of the article and were in
communication with the authors before the submission. All our comments
and suggestions have been taken into account. Hence, we think the
paper can now be published in the current form.

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

Anonymous Report 1 on 2021-6-1 (Invited Report)

  • Cite as: Anonymous, Report on arXiv:scipost_202105_00017v1, delivered 2021-06-01, doi: 10.21468/SciPost.Report.3010


The paper discusses the important measurement of the branching ratio of pi-> e nu decay which was performed at PSI a decade ago but has not yet produced a result. It gives a good description of the experiment and provides estimates of the uncertainties, explaining the principal contributions.


The paper is similar to other publications by the author and the PEN group, providing minimal new information.
The estimate of the main uncertainty is stated to have reached the goal for the experiment but no details are provided to support the assertion that the Monte Carlo calculation is sufficient to do so.


The paper briefly describes an important experiment and is suitable for publication in the journal.

Requested changes

1. Typo in line 43.

  • validity: good
  • significance: high
  • originality: ok
  • clarity: good
  • formatting: good
  • grammar: excellent

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