  The origin of the e^+e^- 511 keV line observed by INTEGRAL remains unclear.
The rate and morphology of the signal have prompted questions as to whether
dark matter could play a role. We explore the case of dark matter upscattering
in the framework of eXciting Dark Matter (XDM), where WIMPs \chi, interacting
through a new dark force, scatter into excited states \chi*, which subsequently
emit e^+e^- pairs when they de-excite. We numerically compute the cross
sections for two Yukawa-coupled DM particles upscattering into excited states,
specifically considering variations motivated by recent N-body simulations with
additional baryonic physics. We find that that l>0 components of the
partial-wave decomposition are often significant contributions to the total
cross section and that for reasonable ranges of parameters dark matter can
produce the ~10^43 e^+/s observed by INTEGRAL.
