CP asymmetries in B→Kπ, K^*π, ρk decays

We show that ratios of tree and penguin amplitudes in B→K ^*π and B→ρK are 2 to 3 times larger than in B→Kπ. This allows for considerably larger CP asymmetries in the former processes than the 10% asymmetry measured in B0→K⁺π ^-. We study isospin sum rules for rate asymmetries in B→Kπ, K^*π, ρK, estimating small violation from interference of tree and electroweak penguin amplitudes. The breaking of the Kπ asymmetry sum rule is estimated to be 1 to 2% and negative. Violation of K ^*π and ρK sum rules can be estimated from B→ρπ amplitudes using flavor SU(3), while breaking of a sum rule combining K^*π and ρK asymmetries can be measured directly in a Dalitz analysis of B0→K⁺π^-π0. The three sum rules can be tested using complete sets of data taken at e ⁺e^- B factories and in experiments at the LHCb and at a future Super Flavor Factory, providing precision searches for new ΔS=ΔI=1 operators in the low-energy effective Hamiltonian.