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We complete the next-to-next-to-leading-order QCD calculation of the branching ratio for B -> Xₛ l^+ l^- including recent results for the three-loop anomalous dimension matrix and two-loop matrix elements. These new contributions modify the branching ratio in the low-q² region, BRₗl, by about +2% and -2%, respectively. We furthermore discuss the appropriate normalization of the electromagnetic coupling alpha, and calculate the dominant higher order electroweak effects, showing that they affect BRₗl and the zero of the forward-backward asymmetry, q²₀, by -5% to +3%, depending on the normalization scale adopted for alpha (muₑm). After introducing a few additional improvements in order to reduce the theoretical error, we perform a comprehensive study of the uncertainty. We obtain BRₗl (1 GeV² <= q² <= 6 GeV²) = (1. 702 +- 0. 170) x 10^-6 and q²₀ = (3. 23 +- 0. 12) GeV².
Bobeth et al. (Fri,) studied this question.