1. Weak-strong simulations with non-Gaussian “strong” beam
D.Shatilov
Usually the weak-strong beam-beam codes assume that the “strong” bunch is Gaussian, and use the Bassetti-Erskine formulae for the kick calculations. But in the Crab Waist scheme the beams are essentially non-Gaussian! The problem is that there are no analytical formulae for the “crabbed” density distribution. The only way to solve this is to use the “grids” for the kick calculations.
In the previous LIFETRAC simulations there were no any “grid” implementations, so we simply assumed the “strong” bunch is Gaussian, and only the “weak” one was crabbed. Of course, it was a simplification, but we hoped it’s not very significant…
During the last upgrade of the code the grids were implemented, and the first tests with the crabbed strong bunch were performed. As we expected, the difference with the “Gaussian” case was not significant. Namely the luminosity, beam sizes blow-up and the tails expansion were rather similar. The only difference is that the optimum waist rotation (i.e. crab sextupole strength) slightly increased. So, for the current SIDDHARTA parameters the optimum CW value increased from 0.6 (old simulations) to about , that is in good agreement with the strong-strong simulations (Ohmi-san).
However, more precise tests of the grids are necessary to perform before making massive simulations with this new feature. Now this work is under way.

2. FMA of the beam-beam effects
D.Shatilov, E.Simonov
Very preliminary! Test of the frequency map analysis for the BB. Red is the diffusive trajectories (resonances), blue is the regular trajectories.
We plan to apply this method to the CW BB simulation to see the resonances suppression.
Axis – beam sizes