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Incoherent Pair Production

    In addition to the interactions between a particle and a macro-scopic field such as beamstrahlung and laser-Compton, there are particle-particle interactions between etex2html_wrap_inline7180, etex2html_wrap_inline7182 and tex2html_wrap_inline7172 that have to be simulated. The present version of CAIN include the following processes:
These QED processes have relatively large event rates even at high energies.

The treatment of these incoherent processes in CAIN is slightly different from other (coherent) processes since the event rates of the former are usually much smaller than the latter.

In contrast to ABEL, CAIN does not assume the particles are ultra-relativistic. Therefore, unless the beam-beam field created by the pair particles becomes significant, their trajectories are correctly calculated. (Note, however, that only the beam field due to the on-coming beam is taken into account in the present version. The beam field in the same beam may have significant effects on low energy particles.)

Among the four QED processes above, the Breit-Wheeler process is treated as a fundamental process. Others are reduced to the former (or to the Compton process, in the case of Bremsstrahlung) by using the virtual photon approximation. As for the polarization, only the circular polarization of initial photons in the direct (non-virtual) Breit-Wheeler process is taken into account.

Toshiaki Tauchi
Thu Dec 3 17:27:26 JST 1998