Simulation of Beam-Beam Lifetime for LEP

A program that uses a new technique to simulate the beam halo in circular e+e- colliders is applied to the LEP. This technique makes it possible to investigate tail particle behavior in reasonable CPU times. The program now includes four interaction points and errors at or between the IP's. Analytical analysis shows that the errors break the symmetry and introduce extra low-order resonances that are forbidden by symmetry. Simulation results show the expected phenomenon. Another effect, the quadrupole mode coherent motion of the strong beam, is also studied. I. INT+R~IXJCTI~N A simulation methodI*) was proposed to look into rare particles in the beam tail (halo) while saving a factor of hundreds, or even thousands, on CPU time as compared to brute-force tracking. A program based on this method was written, tested and applied to PEP-II to understand the halo from the beam-beam interactlon(2). The study concluded that the resonance streaming dominates the beam-beam lifetime. This technique was also applied to LEP. The results showed that the resonance streaming by the beam-beam kick is relatively weak in the LEP, but the lattice nonlinearities, in combination with the beam-beam interaction, can dramatically change lifetimes in the LEP131. To model a more realistic LEP, the simulation program has been upgraded to handle four interaction points (IP). The results show the important role of the errors. Hamiltonian analysis has been extended to interpret the simulation results.