Study of beam–beam effects in eRHIC with self-consistent beam–beam simulation

Beam–beam effects in eRHIC was studied with a self-consistent (strong–strong) beam–beam simulation by using the particle-in-cell method. Beam–beam limits were examined as thresholds of the onset of coherent beam–beam instability. For the proposed luminosity, the bunch intensities optimized in consideration of the beam–beam effect were discussed. It was also found that the modulation in the beam–beam interaction on PACMAN bunches in eRHIC can induce a high-order coherent beam–beam instability with a spontaneous oscillation of transverse beam size and a chaotic oscillation of beam centroid. As the beam–beam interaction in eRHIC is traditionally considered as strong-weak or very unsymmetrical, the beam–beam problem in eRHIC represents an example of the coherent beam–beam effect in the strong-weak case of beam–beam interactions.