Absolute beam energy measurements in e{sup +}e{sup {minus}} storage rings

Journal Article · Wed Jan 01 04:00:00 EST 1997 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.52310· OSTI ID:526794

Placidi, M ^[1]

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1. CERN, Geneva (Switzerland)

The CERN Large Electron Positron collider (LEP) was dedicated to the measurement of the mass M{sub z} and the width {Gamma}{sub z} of the Z{sup 0} resonance during the LEP1 phase which terminated in September 1995. The Storage Ring operated in Energy Scan mode during the 1993 and 1995 physics runs by choosing the beam energy E{sub beam} to correspond to a center-of-mass (CM) energy at the interaction points (IPs) E{sub CM}{sup peak}{plus_minus}1762MeV. After a short review of the techniques usually adopted to set and control the beam energy, this paper describes in more detail two methods adopted at LEP for precise beam energy determination that are essential to reduce the contribution to the systematic error on M{sub z} and {Gamma}{sub z}. The positron beam momentum was initially determined at the 20-GeV injection energy by measuring the speed of a less relativistic proton beam circulating on the same orbit, taking advantage of the unique opportunity to inject two beams into the LEP at short time intervals. The positron energy at the Z{sup 0} peak was in this case derived by extrapolation. Once transverse polarization became reproducible, the Resonant Depolarization ({ital RD}) technique was implemented at the Z{sup 0} operating energies, providing a {le}2{times}10{sup {minus}5} instantaneous accuracy. {ital RD} Beam Energy Calibration has been adopted during the LEP Energy Scan campaigns as well as in Accelerator Physics runs for accurate measurement of machine parameters. {copyright} {ital 1997 American Institute of Physics.}

• OSTI ID: 526794
• Report Number(s): CONF-9605173--
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 390; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
BEAM MONITORING
ENERGY
ENERGY RESOLUTION
LEP STORAGE RINGS
MAGNETIC ANALYZERS
POLARIMETRY
SYNCHROTRON RADIATION