Isospin breaking andω→π+π−decay

Isospin Symmetry Breaking

Isospin symmetry breaking

We discuss the separation of isospin-symmetric and isospin-breaking contributions in the hadronic observables within the framework of QCD plus QED. Further, we briefly review some recent work on the low-energy hadron phenomenology, in which the isospin-breaking effect plays a prominent role.

Isospin breaking in Kl4 decays

Data on Ke4 decays allow one to extract experimental information on the elastic ππ scattering amplitude near threshold, and to confront the outcome of the analysis with predictions made in the framework of QCD. 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 ...

Isospin Breaking in K → 3 π Decays I : Strong Isospin Breaking

The CP conserving amplitudes for the decays K → 3π are calculated in Chiral Perturbation Theory. The calculation is made at the next-to-leading order including strong and local electromagnetic isospin breaking. A comparison is made between the squared amplitudes with and without isospin violation to estimate the size of the effect. We find corrections of order five percent in the amplitudes.

Additional Isospin-Breaking Effects in ǫ′/ǫ

Isospin-breaking effects, in particular those associated with electroweakpenguin contributions and π-η, η mixing, have long been known to affect the Standard Model prediction of ǫ/ǫ in a significant manner. We have found an heretofore unconsidered isospin-violating effect of importance; namely, the u-d quark mass difference can spawn |∆I| = 3/2 components in the matrix elements of the gluonic p...