Study of B→Xγ decays and determination of |V_{td}/V_{ts}|

Using a sample of 471×106 BB̅ events collected with the BABAR detector, we study the sum of seven exclusive final states B→Xs(d)γ, where Xs(d) is a strange (nonstrange) hadronic system with a mass of up to 2.0  GeV/c2. After correcting for unobserved decay modes, we obtain a branching fraction for b→dγ of (9.2±2.0(stat)±2.3(syst))×10-6 in this mass range, and a branching fraction for b→sγ of (23.0±0.8(stat)±3.0(syst))×10-5 in the same mass range. We find B(b→dγ)/B(b→sγ)=0.040±0.009(stat)±0.010(syst), from which we determine |Vtd/Vts|=0.199±0.022(stat)±0.024(syst)±0.002(th).