Hybrid fast multipole method applied to beam-beam collisions in the strong-strong regime - art. no. 054402

The strong-strong interactions of two colliding beams are simulated by trac king the motion of a set of macroparticles. The field generated by each dis tribution is evaluated using the fast multipole method together with some e lements of particle-mesh methods. This technique allows us to check the exa ct frequencies of the coherent modes and the frequencies of oscillations of individual particles in the beam. The agreement between the simulations an d analytical calculations is largely improved. Furthermore, it is an effici ent method to study the coherent modes in the case of separated beams.