Benchmarks for the new-physics search through CP violation in B0→π0KS

Using isospin relations, we predict the standard model correlation between Sπ0KS≡(sin2β)π0KS and Aπ0KS, the mixing-induced and direct CP asymmetries of B0→π0KS. The calculation uses flavor SU(3) only to fix the isospin-3/2 amplitude through the B±→π±π0 branching ratio, and thus has a small irreducible theoretical error. It can reach percent level precision thanks to expected future lattice-QCD progress for the calculation of the relevant SU(3)-breaking form-factor ratio, and serves as a benchmark for new-physics searches. We obtain an interesting picture in the Aπ0KS-Sπ0KS plane, where the current experimental data show a discrepancy with the standard model, and comment on the direct CP asymmetries of B0→π-K+ and B+→π0K+. A modified electroweak penguin with a large new CP-violating phase can explain the discrepancy and allows us to accommodate also the corresponding data for other b→s penguin-dominated decays.