FCC-ee SPIN-POL

Calibrating the centre-of-mass energy by resonant depolarisation of the stored beams is a cornerstone of the precision measurement programme that makes FCC-ee unique. The project confirms the technical feasibility and the performance of the FCC-ee collider scheme proposed in the CDR through sufficiently detailed simulations, completing the study of the depolarisation method. It also unifies the existing simulation codes for luminosity and polarisation so that the spin tune and the interaction-region centre-of-mass energy are calculated together, and it investigates the relationship between those two quantities and its sensitivity to tuning knobs, to centre-of-mass energy and to various imperfections, mitigating it where possible.