  Beginning with the general Bjorken-Mtingwa solution, we derive a simplified
model of intrabeam scattering (IBS), one valid for high energy beams in normal
storage rings; our result is similar, though more accurate than a model due to
Raubenheimer. In addition, we show that a modified version of Piwinski's IBS
formulation (where eta squared over beta has been replaced by the dispersion
invariant) at high energies asymptotically approaches the same result.
