Observation of B+→K+ ηγ

We report measurements of radiative B decays with K eta gamma final states, using a data sample of 253 fb(-1) recorded at the gamma(4S) resonance with the Belle detector at the KEKB e(+)e(-) storage ring. We observe B+ -> K(+)eta gamma for the first time with a branching fraction of (8.44 +/- 1.5(stat)(-0.9)(+1.2)(syst)) x 10(-6) for M (K) (eta) < 2.4 GeV/c(2), and find evidence of B-0 -> K(0)eta gamma. We also search for B -> K-3*(1780)gamma. (c) 2005 Elsevier B.V. All rights reserved.