Recent computer simulation studies and beam-dynamics experiments showed that collective (coherent) beam-beam effects could be important in both situations of "strong-strong" (symmetrical or nearly symmetrical) and "strong-weak" (very unsymmetrical) beam-beam interactions in hadron colliders. In the case of unsymmetrical beam-beam interactions, the coherent beam-beam tune shift could be significantly different from the result of the linearized Vlasov equation with the single-mode approximation or the result of the rigid-beam model. When the beam-beam parameter exceeds a threshold, beam-beam interactions in both situations could induce the collective beam-beam instability and result in a significant emittance growth on both beams. In this talk, I will discuss some recent understandings of collective beam-beam effects and methods of beam-beam simulation for hadron colliders.


Talk Slides: (slides)