FCC-ee: Energy calibration

Understand

The FCC-ee aims to improve on electroweak precision measurements, with goals of 100 keV on the Z mass and width, and a fraction of MeV on the W mass.

• Compared to LEP, this implies a much improved knowledge of the centre-of-mass energy when operating at the Z peak and WW threshold.
• This can be achieved by making systematic use of resonant depolarization.
• A number of issues have been identified, due in particular to the long polarization times.