Impact of |ΔI|=5/2 transitions in K→ππ decays

S. Gardner, G. Valencia

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


We consider the impact of isospin violation on the analysis of K→ππ decays. We scrutinize, in particular, the phenomenological role played by the additional weak amplitude, of |ΔI|=5/2 in character, incurred by the presence of isospin violation. We show that Watson's theorem is appropriate in Script O sign(md-mu), so that the inferred ππ phase shift at √s=mK determines the strong phase difference between the I=0 and I=2 amplitudes in K→ππ decay. We find the magnitude of the |ΔI|=5/2 amplitude thus implied by the empirical branching ratios to be larger than expected from estimates of isospin-violating strong and electromagnetic effects. We effect a new determination of the octet and 27-plet coupling constants with strong-interaction isospin violation and with electromagnetic effects, as computed by Cirigliano, Donoghue, and Golowich, and find that we are unable to resolve the difficulty. Exploring the role of |ΔI|=5/2 transitions in the CP-violating observable ∈′/∈, we determine that the presence of a |ΔI|=5/2 amplitude impacts the empirical determination of ω, the ratio of the real parts of the |ΔI|=3/2 to |ΔI|=1/2 amplitudes, and that it generates a decrease in the estimation of ∈′/∈.

Original languageEnglish
Article number094024
Pages (from-to)1-15
Number of pages15
JournalPhysical review D
Issue number9
StatePublished - Nov 1 2000

ASJC Scopus subject areas

  • Physics and Astronomy (miscellaneous)


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