Description: In this lecture we review the current understanding of the beam-beam interaction in e/sup +/e/sup -/ linear colliders. Strictly speaking, the two effects, disruption and beamstrahlung, during beam-beam interaction are coupled. This is self-evident because without deflection there would be no radiation, and with radiation during bending the remaining trajectory of particles would not be the same. Fortunately, in a large range of beam parameters the average disruption angles are rather small, and the emission of hard photons are relatively rare. For these reasons the two effects can be isolated from each other to the first degree of accuracy, and our study of the issue can be greatly simplified. This happens also to be the development historically. We discuss the effects associated with disruption with negligible beamstrahlung. Here, an important parameter, the disruption parameter D, is introduced. We then discuss the maximum and rms disruption angles. The analytic scaling laws for D >> 1 and D << 1 are then compared with simulation results. Next we investigate the enhancement of luminosity due to disruption. Together with the aspect ratio R identical to sigma/sub x//sigma/sub y/, the two parameters define a scaling law for luminosity enhancement, H/sub D1/, due to the mutual pinching of the e/sup +/e/sup -/ bunches where the effective beam size sigma/sub x/sigma/sub y/ is reduced. Next we discuss beamstrahlung with negligible disruption. First we review the nature of beamstrahlung by describing the novel features of the problem. These specific features are then compared with the known radiation phenomena with emphasis on their similarities and differences. 36 refs.
Date: August 1, 1987
Creator: Chen, P.
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