Non-perturbative effects in (B)over-bar→Xsl+l- for large dilepton invariant mass

We reconsider the calculation of O(Lambda(QCD)(2)/m(b)(2)) non-perturbative corrections to (B) over bar --> X(s)l(+)l(-) decay. Our analysis confirms the results of Ali et al. for the dilepton invariant mass spectrum, which were in disagreement with an earlier publication, and for the lepton forward-backward asymmetry. We also give expressions for the O(Lambda(QCD)(2/)m(b)(2)) corrections to the left-right asymmetry. In addition we discuss the breakdown of the heavy quark expansion near the point of maximal dilepton invariant mass q(2) and consider a model-independent approach to this region using heavy hadron chiral perturbation theory. The modes (B) over bar --> (K) over bar l(+)l(-) and (B) over bar --> (K) over bar pi l(+)l(-), which determine the endpoint region of the inclusive decay, are analyzed within this framework. An interpolation is suggested between the region of moderately high q2 where the heavy quark expansion is still valid, and the vicinity of the endpoint described by chiral perturbation theory. We also comment on further non-perturbative effects in (B) over bar --> X(s)l(+)l(-). (C) 1998 Elsevier Science B.V.