  The soft function relevant for the production of an electroweak boson
(photon, W, Z or H) with large transverse momentum at a hadron collider is
computed at next-to-next-to-leading order. This is the first two-loop
computation of a soft function involving three light-cone directions. With the
result, the threshold resummation for these processes can now be performed at
next-to-next-to-next-to-leading logarithmic accuracy.
