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Particles and Fields
Eur. Phys. J. C 26, 195-200 (2002)
DOI: 10.1140/epjc/s2002-01053-x

Implications of $B \to \rho \gamma$ measurements in the standard model and supersymmetric theories

A. Ali and E. Lunghi

Deutsches Elektronen Synchrotron, DESY, Notkestrasse 85, 22607 Hamburg, Germany

(Received: 19 August 2002 / Published online: 18 October 2002 )

We study the implications of the recently improved upper limits on the branching ratios for the decays $B \to \rho \gamma$, expressed as $R(\rho \gamma/K^* \gamma)\equiv {\cal B}(B \to \rho \gamma)/{\cal
B}(B \to K^* \gamma) <0.047$ . We work out the constraints that the current bound on $R(\rho \gamma/K^* \gamma)$ implies on the parameters of the quark mixing matrix in the standard model (SM). Using the present profile of the unitarity triangle, we predict this ratio to lie in the range $0.010 \leq R(\rho\gamma/K^*\gamma)
\leq 0.046$ (at 95% C.L.), with the central value $R(\rho\gamma/K^*\gamma)=0.023$. We also work out the correlations involving $R(\rho \gamma/K^* \gamma)$, the isospin-violating ratio $\Delta (\rho \gamma)$, and the direct CP-violating asymmetry $A_{CP}(\rho \gamma)$ in $B \to \rho \gamma$ decays in the SM, in the minimal supersymmetric extension of the SM (MSSM), and in an extension of the MSSM involving an additional flavor-changing structure in $b
\to d$ transitions.

© Società Italiana di Fisica, Springer-Verlag 2002