How isospin violation mocks "new" physics: pi(0)-eta,eta ' mixing in B ->pi pi decays - art. no. 077502

An isospin analysis of B --> pi pi decays yields sin 2 alpha, where alpha=a rg[-VtdVtb*/(VudVub*)] and V-ij is a CKM matrix element, without hadronic u ncertainty if isospin is a perfect symmetry. Isospin, however, is broken no t only by electroweak effects but also by the u and d quark mass difference . The latter drives pi(0)-eta,eta' mixing and converts the isospin-perfect triangle relation between the B --> pi pi amplitudes to a quadrilateral. Th e combined isospin-violating effects impact the extracted value of sin 2 al pha in a significant manner, particularly if the latter is small. [S0556-28 21(99)05505-8].