$|V_{td}/V_{ts}|$ from $B\to V \gamma$

The dominant theoretical uncertainty in extracting |V_td/V_ts| from the ratio of branching ratios R=B(B->(rho,omega)gamma)/B(B-> K* gamma) is given by the ratio of form factors xi = T_1^{B->K*}(0)/T_1^{B-> \rho}(0). We re-examine xi in the framework of QCD sum rules on the light-cone, taking into account hitherto neglected SU(3)-breaking effects. We find xi = 1.17\pm 0.09, which, using QCD factorisation for the branching ratios, and the experimental result for R obtained by the Belle collaboration, currently translates into |V_td/V_ts|= 0.207\pm 0.027(exp) \pm 0.016 (th). This result agrees with that obtained from the Standard Model unitarity triangle based on tree-level-only processes and with |V_td/V_ts| inferred from the two-sided bound on Delta m_s reported recently by the D0 collaboration.