Theoretical error of luminosity cross section at LEP

Abstract

The aim of this note is to characterize briefly main components of theoretical error of the small angle Bhabha measurement at LEP and to discuss critically how solid these estimates really are, from todays perspective. We conclude that the existing theoretical error of the LEP luminometer process (small angle Bhabha) is rather solid, and we add some new discussion concerning the remaining uncertainties and prospects of the future improvements toward the $\le 0.025%$ precision.