Affine Hecke algebras associated to Kac-Moody groups

In this paper we give a geometric construction of Cherednik's double affine Hecke algebra. We construct the algebra as the equivariant $K$-theory of the Lagrangian subvariety of the cotangent variety of the square of the flag variety of $G$, the variety being given by the union of the conormal bundles to the $G$-orbits on $\flag\times\flag$. This is a generalisation of work of Kazhdan and Lusztig to the Kac-Moody case, and is suitable for describing a certain class of modules for this algebra. In a paper in preparation we will do this, in the case $G$ is affine (Cherednik's case).