Isospin breaking contributions to ϵ′/ϵ

A. J. Buras, J. M. Gerard

Research output: Contribution to journalArticlepeer-review

137 Scopus citations

Abstract

We reanalyze the π0-η-η′ mixing and the QED Penguin operator contributions to ε{lunate}′ ε{lunate}, using the 1 N expansion to estimate the relevant hadronic matrix elements. We find that the existing analyses of the QED Penguin operators contain errors both in the Wilson coefficient functions and in the corresponding hadronic matrix elements. The true QED Penguin operator contributions to ε{lunate}′/ε{lunate} turn out to be substantially smaller than previously estimated, and consequently the dominant isospin breaking effect on ε{lunate}′ ε{lunate} comes from the π0-η-η′ mixing. Taking all these effects into account we find that they reduce the standard model estimate of ε{lunate}′ ε{lunate} based on the pure QCD Penguin contribution by roughly 25%, which should be contrasted with a factor of two or three reduction found by Donoghue et al. We also emphasize that in addition to the value of the top quark mass, a better determination of the strange quark mass is required before a firm value for ε{lunate}′/ε{lunate} within the standard model can be obtained.

Original languageEnglish
Pages (from-to)156-162
Number of pages7
JournalPhysics Letters B
Volume192
Issue number1-2
DOIs
StatePublished - 25 Jun 1987
Externally publishedYes

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