Theoretical progress on cusp effect and Kl4 decays

Abstract

The cusp effect in K \to 3πand data on K_e4 decays allow one to extract experimental information on the elastic ππscattering amplitude near threshold, and to confront the outcome of the analyses with predictions made in the framework of QCD. In my talk I pointed out that these predictions concern an isospin symmetric world, while experiments are carried out in the real world, where isospin breaking effects -- generated by electromagnetic interactions and by the mass difference of the up and down quarks -- are always present. I discussed the corrections required to account for these, so that a meaningful comparison with the predictions becomes possible. In particular, I pointed out that there is a spectacular isospin breaking effect in K_e4 decays, overlooked so far. Once it is taken into account, the previous discrepancy between NA48/2 data on K_e4 decays and the prediction of ππscattering lengths disappears.

Plenary talk given at the International Conference KAON'07, Laboratori Nazionali di Frascati, Italy, May 21-25, 2007. To appear in the proceedings. 10 pages, 3 figures

References in corpus (13)

• I=2 pi-pi Scattering from Fully-Dynamical Mixed-Action Lattice QCD
• High statistics measurement of Ke4 decay properties
• Determination of the a0-a2 pion scattering length from K->pi+ pi0 pi0 decay
• Precise Determination of the I=2 pipi Scattering Length from Mixed-Action Lattice QCD
• Pion-pion scattering and the K->3pi decay amplitudes
• Pi-K Scattering in Full QCD with Domain-Wall Valence Quarks
• K -> 3 pi Final State Interactions at NLO in CHPT and Cabibbo's Proposal to Measure a_0-a_2
• pi pi scattering
• Insights and puzzles in light quark physics
• Theoretical progress on pi pi scattering lengths and phases
• Size of Isospin Breaking in Charged K(L4) Decay
• The isospin symmetry breaking effects in $K_{e4}$ decays
• Electromagnetic effects and scattering lengths extraction from experimental data on $K\to 3\pi$ decays

Cited by in corpus (9)

• The pion-pion scattering amplitude. III: Improving the analysis with forward dispersion relations and Roy equations
• Dispersive representation and shape of the Kl3 form factors: robustness
• Isospin breaking in Kl4 decays
• Cusps in K --> 3pi decays: a theoretical framework
• Finding the sigma pole by analytic extrapolation of $\pi \pi$ scattering data
• Model independent determination of the sigma pole
• Theoretical progress on pi pi scattering lengths and phases
• The electromagnetic effects in $K_{e4}$ decay
• New results on kaon decays from NA48/2