QED MULTIPHOTON CORRECTIONS TO BHABHA SCATTERING AT LOW ANGLES - MONTE-CARLO SOLUTION

We calculate the QED-corrected integrated cross-section for small-angle Bhabha scattering with kinematical cuts very close to the real experimental cuts at the LEP/SLC experiments - no distinction between electrons and photons is made. We effectively compare up to four independent Monte Carlo calculations and one semi-analytical calculation. The aim of the exercise is to establish precision of the O (alpha) Monte Carlo calculation with the exclusive exponentiation of the Yennie-Frautschi-Suura type. It provides the integrated cross-section for the low-angle Bhabha scattering process (curly theta < 10-degrees), necessary for luminosity measurement, with an overall precision of 0.25%. The corresponding computer program BHLUMI 2.00 is in the form of a stand-alone Monte Carlo event generator. The complete and explicit definition of the multiphoton matrix element is given. Examples of numerical results from Monte Carlo phase space integration are demonstrated and discussed.