MONTE-CARLO PROGRAM BHLUMI 2.01 FOR BHABHA SCATTERING AT LOW ANGLES WITH YENNIE-FRAUTSCHI-SUURA EXPONENTIATION

A Monte Carlo program for small-angle Bhabha scattering with an overall precision of 0.25% is presented. The QED calculation at this precision level is of vital importance for luminosity measurements at LEP/SLC experiments. BHLUMI is a stand-alone Monte Carlo event generator with three sub-generators: BHLUM2, LUMLOG and OLDBIS. The first of them is based on Yennie-Frautschi-Suura O(alpha) exponentiation and the two other ones serve, essentially, to cross-check results from the first one. LUMLOG represents pure leading-logarithmic calculation up to O(L3-alpha-3) and OLDBIS represents ordinary (non-exponentiated) O(alpha) calculation. The important advantage of LUMLOG and OLDBIS is that they feature a very high technical precision of 0.02%. All three sub-generators form a very powerful tool box of programs for precise calculations of QED corrections to the luminosity measurements in present e +/- annihilation experiments.