Search Results (3 total)

This paper deals with two topics: the generation of incoherent pairs in two beam-beam simulation programs, GUINEA-PIG and CAIN, and the influence of the International Linear Collider (ILC) beam parameter choices on the background in the micro–vertex detector (VD) induced by direct hits. One of the processes involved in incoherent pair creation (IPC) is equivalent to a four fermions interaction and its cross section can be calculated exactly with a dedicated generator, BDK. A comparison of GUINEA-PIG and CAIN results with BDK allows to identify and quantify the uncertainties on IPC background predictions and to benchmark the GUINEA-PIG calculation. Based on this simulation and different VD designs, the five currently suggested ILC beam parameter sets have been compared regarding IPC background induced in the VD by direct IPC hits. We emphasize that the high luminosity set, as it is currently defined, would constrain both the choices of magnetic field and VD inner layer radius.

We have measured the mass of the Z boson to be 91.11±0.23 GeV/c², and its width to be 1.61_-0.43^+0.60 GeV. If we constrain the visible width to its standard-model value, we find the partial width to invisible decay modes to be 0.62±0.23 GeV, corresponding to 3.8±1.4 neutrino species.

We report the first direct observation of the electromagnetic deflection of high-energy electron and positron beams as they pass each other with small impact parameters. Measurements of the deflection amplitude are found in agreement with theoretical expectations. This phenomenon, which is sensitive both to the relative position of the two beams and to their transverse sizes, has been used successfully to optimize and maintain collisions at the interaction point of the SLAC Linear Collider.