L. Arnaudon et al., ACCURATE DETERMINATION OF THE LEP BEAM ENERGY BY RESONANT DEPOLARIZATION, Zeitschrift fur Physik. C, Particles and fields, 66(1-2), 1995, pp. 45-62
To improve the measurements of the Z boson mass and resonance width, t
he 1993 Large Electron Positron Collider (LEP) run was devoted to a th
ree point beam energy scan, with one point close to the peak of the Z
resonance and two points roughly 880 MeV below and above the peak. Ope
rational energy calibration by resonant depolarization was successfull
y commissioned for all three beam energies. 24 energy calibrations wer
e performed at the end of physics fills. The accuracy of each calibrat
ion is better than 1 MeV. About one third of the total integrated lumi
nosity was recorded in calibrated fills below and above the resonance
and a regular tracking of the beam energies throughout the scan was po
ssible. The evolution of the beam energies in the course of the year s
howed a large variation of up to 20 MeV. Results from the energy calib
rations will be presented and possible explanations for the changes of
the beam energy during the year will be described.