Supersymmetric Effects on Isospin Symmetry Breaking and Direct CP Violation in $B\to \rho \gamma$

Abstract

We argue that one can search for physics beyond the standard model through measurements of the isospin-violating quantity ${\Delta }^{-0}\equiv \Gamma (B^{-}\to {\rho }^{-}\gamma )/2\Gamma (B^0\to {\rho }^0\gamma )-1$, its charge conjugate ${\Delta }^{+0}$, and direct CP violation in the partial decay rates of $B^{\pm }\to {\rho }^{\pm }\gamma$. We illustrate this by working out theoretical profiles of the charge-conjugate averaged ratio $\Delta \equiv \frac{1}{2}({\Delta }^{+0}+{\Delta }^{-0})$ and the CP asymmetry $A_{CP}(B^{\pm }\to {\rho }^{\pm }\gamma )$ in the standard model and in some variants of the minimal supersymmetric standard model. We find that chargino contributions in the large $\tan \beta$ region may modify the magnitudes and flip the signs of $\Delta$ and $A_{CP}(B^{\pm }\to {\rho }^{\pm }\gamma )$ compared to their standard-model values, providing an unmistakeable signature of supersymmetry.

Comments: 10 pages, 7 figures (requires graphicx)