Abstract
We study, using a Monte Carlo approach, the rare decay B→X s l + l - including the effects of the arbitrariness of the phase between the ψ amplitudes and the perturbative amplitude, b-quaik Fermi motion inside the B meson, and experimental smearing of lepton momenta. We find that such effects reduce the sensitivities of the spectra of invariant mass and forward-backward asymmetry of the lepton pair to new physics, especially in the neighborhood of the ψ resonances. We also estimate the sensitivity range of the Wilson coefficients with respect to the uncertainties. ©1999 The American Physical Society.