Measurement of charmless B decays to ηK* and ηρ

We report measurements of branching fractions and CP asymmetries for B ->eta K-* and B ->eta rho decays. These results are obtained from a 414 fb(-1) data sample collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We measure the following branching fractions: B(B-0 ->eta K-*0)=(15.2 +/- 1.2 +/- 1.0)x10(-6) and B(B+->eta K*+)=(19.3(-1.9)(+2.0)+/- 1.5)x10(-6), where the first error is statistical and the second systematic. We also find a 2.7 sigma excess in the B+->eta rho(+) mode and measure B(B+->eta rho(+))=(4.1(-1.3)(+1.4)+/- 0.4)x10(-6)< 6.5x10(-6) at 90% confidence level. For B-0 ->eta rho(0) decays, we determine the upper limit B(B-0 ->eta rho(0))< 1.9x10(-6) at 90% confidence level. The partial rate asymmetries are A(CP)(eta K-*0)=0.17 +/- 0.08 +/- 0.01, A(CP)(eta K*+)=0.03 +/- 0.10 +/- 0.01, and A(CP)(eta rho(+))=-0.04(-0.32)(+0.34)+/- 0.01.