HIGHER-ORDER RADIATIVE-CORRECTIONS TO LOW-ANGLE BHABHA SCATTERING - THE YFS MONTE-CARLO APPROACH

We calculate the QED-corrected integrated cross-section for small-angl e Bhabha scattering with kinematical cuts identical to the red experim ental cuts at the LEP/SLC experiments: no distinction between electron s and photons is made. We present a new second-order Monte Carlo calcu lation with the exponentiation of the Yennie-Frautschi-Suura type. It provides the integrated cross-section for the low-angle Bhabha scatter ing process (theta < 0.060), necessary for the luminosity measurement, with an overall precision of 0.16%. The corresponding computer progra m BHLUMI 4.01 is in the form of a stand-alone Monte Carlo event genera tor. The complete and explicit definition of the multiphoton matrix el ement is given. Examples of numerical results from Monte Carlo phase-s pace integration are demonstrated and discussed. The analytical integr ation of the cross section for simplified cuts, keeping terms up to th ird order, used for cross-checks of the Monte Carlo calculation, is al so presented.