Isospin-violating contributions to ∈/∈

Research output: Contribution to journalArticle


The known isospin-breaking contributions to the K → ππ amplitudes are reanalyzed, taking into account our current understanding of the quark masses and the relevant non-perturbative inputs. We present a complete numerical reappraisal of the direct CP-violating ratio ∈/∈, where these corrections play a quite significant role. We obtain the Standard Model prediction Re (∈/∈) = (14 ± 5) · 10−4, which is in very good agreement with the measured ratio. The uncertainty, which has been estimated conservatively, is dominated by our current ignorance about 1/NC-suppressed contributions to some relevant chiral-perturbation-theory low-energy constants.


External organisations
  • Technical University of Dortmund
  • University of Valencia
  • Los Alamos National Laboratory
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Subatomic Physics


  • Chiral Lagrangians, CP violation, Effective Field Theories, Kaon Physics
Original languageEnglish
Article number32
JournalJournal of High Energy Physics
Issue number2
Publication statusPublished - 2020 Feb 1
Publication categoryResearch