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We present the Monte Carlo program BHAGEN95, for calculating the crosssection of the Bhabha scattering process at LEP1/SLC and LEP2 energies, usable with continuity from small to large-angle configurations. We discuss some improvements in the event generator BHAGEN94, which is now part of the new code. In particular the weak and QCD corrections are implemented up to two loops for the relevant contributions, and the emission of one hard photon is treated exactly. We have included all the radiative corrections which are necessary to obtain, for a typical experimental event selection, a precision of 0.1-0.2% at small-angle. At large-angle we estimate a precision of 0.5%, with the exception of the region where the beam energy is a few GeV above the Z boson resonance, where it is up to 1%. A detailed comparison with other codes for both small-angle and large-angle Bhabha scattering is performed. PACS 12.15.-y Electroweak interactions PACS 12.15.Lk Electroweak radiative corrections PACS 12.20.-m Quantum electrodynamics PACS 12.20.Ds Specific calculations ⋆

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The values at pseudothreshold of two loop sunrise master amplitudes with arbitrary masses are obtained by solving a system of differential equations. The expansion at pseudothreshold of the amplitudes is constructed and some lowest terms are explicitly presented.

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The system of 4 differential equations in the external invariant satisfied by the 4 master integrals of the general massive 2-loop sunrise self-mass diagram is solved by the Runge-Kutta method in the complex plane. The method, whose features are discussed in details, offers a reliable and robust approach to the direct and precise numerical evaluation of Feynman graph integrals.

7 pagesThe results concerning the theoretical evaluation of the small-angle Bhabha Scattering cross section obtained during the Workshop on Physics at LEP2 (CERN, Geneva, Switzerland, 1995) by the Working Group ``Event Generators for Bhabha Scattering'' are summarized. The estimate of the theoretical error on the cross section in the luminometry region is updated

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