Direct CP asymmetry of B→Xd,sγ in a model with vector quarks

We investigate the effect of vector quarks on the inclusive decays B→Xd,sγ. We show that the branching ratio of B→Xdγ can differ sizably from the SM and MSSM predictions, being enhanced to present experimental observability or suppressed such that present runs of the B factories would not observe it. Current measurements of the direct CP asymmetry (ACP) for B→Xsγ are sensitive to the contribution from B→Xdγ. For a sufficiently enhanced BR(B→Xdγ) we show that the dominant contribution to the combined asymmetry may be from B→Xdγ. Thus any large value for ACP should not immediately be attributed to B→Xsγ, which stresses the importance of good K/π separation.