Measurement of Forward-Backward Asymmetry and Wilson Coefficients in $B \to K^* \ell^+ \ell^-$

Abstract

We report the first measurement of the forward-backward asymmetry and the ratios of Wilson coefficients $A_9/A_7$ and $A_{10}/A_7$ in $B \to K^* \ell^+ \ell^-$, where $\ell$ represents an electron or a muon. We observe a large integrated forward-backward asymmetry with a significance of 3.4$\sigma$. The results are obtained from a data sample containing 386 $\times 10^6$ $B\bar{B}$ pairs that were collected on the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider.