A brief account of the study of rare B decay $B \to K^\ast \ell^+ \ell^-$ using soft-collinear effective theory (SCET) is presented. Theoretical underpinning of this work is a factorization formula, derived to leading power in $1/m_b$ and valid to all orders in $\alpha_s$. Partially integrated branching ratio in the dilepton squared mass range $1 { GeV}^2 \le q^2 \le 7 { GeV}^2$ and the forward-backward (FB) asymmetry of the leptons are calculated. For the zero-point of the FB asymmetry, we get $q_0^2=(4.07^{ +0.16}_{ -0.13}) { GeV}^2$. The scale-related uncertainty of $q_0^2$ is improved compared to the earlier estimate of the same.
Categories: hep-ph