Direct CP asymmetry of b → sγ and b → dγ in models beyond the standard model

We study the direct CP asymmetry of the decays b → sγ and b → dγ in the context of two models: i) a supersymmetric (SUSY) model with unconstrained SUSY phases, and ii) a model with a single generation of vector quarks. In both the above models we show that b → dγ can sizeably influence the combined asymmetry (i.e. that of a sample containing both b → sγ and b → dγ), and in case (ii) may in fact be the dominant contribution.