Sum rules for B→πη(′), Kη(′), η(′)η(′) decays

We provide a set of sum rules, using flavor symmetries, relating CP-averaged ratios and CP asymmetries of different neutral and charged B mesons decaying into an η(′) particle together with a pion, a kaon or a second η(′). These sum rules allow us to give a prediction for the B0→K0η branching ratio. We also predict a clear sign anti-correlation between the two B0→π0(η,η′) CP asymmetries, and find a combined constraint on the branching ratios and CP asymmetries of the three B→η(′)η(′) decay modes.