$B \rightarrow K\ast l^+l^-$ forward-backward asymmetry and new physics
Wei-Shu Hou, Artyom Hovhannisyan, and Namit Mahajan

The forward-backward asymmetry ${\cal A}_{\rm FB}$ in $B\to K^*\ell^+\ell^-$ decay is a sensitive probe of New Physics. Previous studies have focused on the sensitivity in the position of the zero. However, the effective Wilson coefficients (short distance effective couplings) are in principle complex, as illustrated by $B\to \rho\ell^+\ell^-$ decay within the Standard Model. Allowing for this, but keeping the $B\to K^*\gamma$ and $K^*\ell^+\ell^-$ rate constraints, we find the landscape for ${\cal A}_{\rm FB}(B\to K^*\ell^+\ell^-)$ to be far richer than from entertaining just sign flips. The complex nature of effective Wilson coefficients can be explored by future high statistics experiments.

© 2008 The American Physical Society.