A Simplified Model of Intrabeam Scattering
  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 In addition, we show that a modified version of Piwinski's IBS formulation (where eta squared over beta has been replaced by the dispersion invariant) at high energies asymptotically approaches the same result. 
Karl L.F. Bane