CP Asymmetries in B->K pi, Kpi, rho K Decays

We show that ratios of tree and penguin amplitudes in B-> K*pi and B->rho K are two to three times larger than in B-> K pi. This allows for considerably larger CP asymmetries in the former processes than the 10% asymmetry measured in B0 -> K+pi-. We study isospin sum rules for rate asymmetries in B-> K pi, K*pi, rho K, estimating small violation from interference of tree and electroweak penguin amplitudes. The breaking of the K pi asymmetry sum rule is estimated to be one to two percent and negative. Violation of K*pi and rho K sum rules can be estimated from B->rho pi amplitudes using flavor SU(3), while breaking of a sum rule combining K*pi and rho K asymmetries can be measured directly in a Dalitz analysis of B0-> K+pi-pi0. The three sum rules can be tested at the LHCb and at a future Super Flavor Factory, providing precision searches for new Delta S =Delta I=1 operators in the low energy effective Hamiltonian.