Nonperturbative mX cut effects in B→Xsl+l- observables

Recently, it was shown that in inclusive B→Xsl+l- decay, an angular decomposition provides three independent (q2 dependent) observables. A strategy was formulated to extract all measurable Wilson coefficients in B→Xsl+l- from a few simple integrals of these observables in the low q2 region. The experimental measurements in the low q2 region require a cut on the hadronic invariant mass, which introduces a dependence on nonperturbative b quark distribution functions. The associated hadronic uncertainties could potentially limit the sensitivity of these decays to new physics. We compute the nonperturbative corrections to all three observables at leading and subleading order in the power expansion in ΛQCD/mb. We find that the subleading power corrections give sizeable corrections, of order -5% to -10% depending on the observable and the precise value of the hadronic mass cut. They cause a shift of order -0.05 GeV2 to -0.1 GeV2 in the zero of the forward-backward asymmetry.