Arnaudon, L

Assmann, R W

Blondel, A

Bouchet, B

Camas, J

Dehning, Bernd

Ferri, G

Grosse-Wiesmann, P

Grote, H

Jacobsen, R

Koutchouk, Jean-Pierre

Mann, J

Miles, J

Olsen, R

Placidi, Massimo

Schmidt, R

Wenninger, J

CERN Document Server

SI./ Div Reps5 August, 1994 OCR OutputGeneva, SwitzerlandEcole Polytechnique, Paris, FranceMax-Planck Institute fiir Physik, Werner-Heisenberg Institut, Munchen, GermanyLondon, nited Kingdom, 27.6-1.7.94Presented at the Fourth Eurogeun Particle Accelerator Conference (EPAC 94),is at least possible up to 35 GeV.excellent agreement with theoretical calculations, showing that radiative polarization at LEPthe whole year. Higher-order depolarization due to beam energy spread was measured indepolarization at the end of physics coasts was done and the beam energy was monitored overestablished at three operational LEP energies. Regular energy calibration with resonantsolenoids were successfully spin matched and polarization in close to physics conditions wasThe polarization degree was improved from below 16% to almost 60%. All four experimentalIn 1993 several important achievements on transverse spin polarization at LEP were obtained.AbstractPlacidi, R. Schmidt, ]. WenningerP.Grosse-Wiesmann, H. grote, R. Jacobsen, I.-P. Koutchouk, I. Mann,]. Miles, R. Olsen, M.L. Arnaudon, R. Assmann*, A. Blondel**, B. Bouchet, ].Camas, B. Dehning, G.P. Perri,Recent Achievements in Transverse Spin-Polarization at LEPCERN-SL-94-60Q °" PM °’ IllllllllfllllllllllllllllHlllllllllfllIllillllllllllll iCERN SL/94-60 (AP)CERN LIBRARIES, GENEVACERN - SL DIVISIONEUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHlEco1e Polyteclmique, Paris, France. and k,k,,ky,k, are any integers. For the LEP standard OCR OutputMiinchen, Germany. where Q,, Qy and Q, are the tunes of the orbital motion'Max-Planck-Institut fiir Physik, Werner-Heisenberg-Institut,v : k t k,Q, 5; kyQ, ;l: k,Q,condition is written asspin precession and the orbital motion. The resonancespin resonances arise as coupling resonances between thein fig. 1.maximum degree of polarization is expected. Depolarizingand the compensation of ALEPH and DELPHI are showntune is close to the half-integer, e.g. u : 101.47. Then abumps The depolarizing effect ofthe ALEPH solenoiday. The LEP energies are always set such that the spinbe compensated by a configuration of vertical closed orbitThe spin precession is described by the spin tune u :However, the spin rotations caused by the solenoids canwith all four solenoids successfully spin matched.an insignificant polarization degree is left with solenoids.vertical closed orbit. Polarization up to 57% was measurednon—vertical magnetic fields cause depolarization and onlyment is explained by side effects from the solenoids on theLEP and 2) from the settings of the betatron tunes. AllThe drop in polarization towards the end of the experinal magnetic fields at the large experimental solenoids inclose to physics conditions arise 1) from the longitudiThe dominant problems in order to find polarization in during that experiment.can be observed. The spin tune (beam energy) was 105.5CONDITIONSis shown. After spin matching some loss in polarization2 POLARIZATION IN PHYSICSsolenoid and the spin matching of ALEPH and DELPHI(HSM). The depolarizing effect of the unmatched ALEPHin 1993. The main results are presented in the following.to above 30% by deterministic Harmonic Spin Matchingtal and theoretical program on polarization was followedshown. The polarization could be increased from 8%In order to improve this situation a thourough experimenFigure 1: The first polarization measurement in 1993 iswere needed to find a polarization degree of typically 10%.ditions. In 1992 often as much as 12 hours of optimizationhigh transverse beam polarization in close to physics conDaytimeRegular energy calibrations on an operational basis need3:® 5:00 7:® 9:00 11:® 13:00{erred to as energy calibration by resonant depolarization.the mass and the width ofthe Z boson. The method is resure accurately the absolute energy scale of LEP and hence DELPHITransverse spin polarization opens the possibility to mea1 INTRODUCTIONALEPH· Spin matchingtion at LEP is at least possible up to 55 GeV. L —— Solenoid field 10theoretical calculations, showing that radiative polarizaenergy spread was measured in excellent agreement withthe whole year. Higher-order depolarization due to beamcoasts was done and the beam energy was monitored overbration with resonant depolarization at the end of physics“" asm l ` 10 ..... _ i .»-·‘“"7" '```at three operational LEP energies. Regular energy calipolarization in close to physics conditions was establishedexperimental solenoids were successfully spin matched and"it ei . .%VE 2 • . 2 » t Ogree was improved from below 16% to almost 60%. All fourpolarization at LEP were obtained. The polarization deIn 1993 scvcra.1 important achievements on transverse spinAbstractR. SCHMIDT, J. WENNINGER, CERN, SwitzerlandJ.P. KOUTCHOUK, J. MANN, J. MILES, R. OLSEN, M. PLACIDI,B. DEHNING, G.P. FERRI, P. GROSSE-WIESMANN, H. GROTE, R. JACOBSEN,L. ARNAUDON, R. ASSMANN §‘A. BLONDEL I B. BOUCHET, J. CAMAS,Recent Achievements in Transverse Spin-Polarisation at LEPequal imperfections for all storage rings the polarization imental and theoretical studies showed that the average OCR Outputoff-peak luminosity was taken in calibrated fills. Experout HSM) and from HERA data (with HSM). AssumingThe constant a was adjusted from SPEAR data (with nance was done in LEP. About one third of the integratedof physics coasts. In 1993 a 3-point scan of the Z reso1 + (aE) the beam energy could be routinely measured at the end(1)P : 92.4%Due to the achievements in transverse beam polarizationcan be written as [3]: 4 ENERGY CALIBRATIONthe dependence of polarization P on the beam energy Ehighest beam energy so far. In the linear approdmationHarmonic Spin Matching are given inRadiative beam polarization [2] is observed for LEP at themaximum of 57% :f: 3%. More details on deterministicPOLARIZATION tion was always established beyond 35% with a measuredshown in fig. 1. With Harmonic Spin Matching polariza3 OPTIMIZATION OFdeterministic way. Its effect on polarization was alreadyHarmonic Spin Matching can therefore be applied in anization is shown in fig. 2.of spin resonances can be measured directly in LEPphysics fills. The effect from the betatron tunes on polarquadrupoles and the precise orbit monitors the strengthsfill this did not prevent energy calibrations at the end ofuse of Harmonic Spin Matching Due to the well alignedstandard value. Since the tunes can be changed inside abeam polarization in LEP can only be established by thethe horizontal betatron tune differs significantly from itsFrom fig. 3 it can be concluded that high transversetion experiments (Q, = 90.10 and Q, : 76.20). EspeciallySpecial betatron tunes were therefore chosen for polariza ization by higher—order effects was indeed feared.close to the half-integer depolarization cannot be avoided. avoided. Before LEP went into operation, strong depolarthe standard spin tune v = 101.47. Since this resonance is these resonances were not present, but that they could beQ, -1- Qy resonance shows up at k + .47, i.e. just on top of with an exponent larger than 2. This does not mean thatization, the dependence on the energy would be steeperbetatron tunes in 1993 (Q, = 90.27 and Qy : 76.18), thespin resonances would have contributed to the depolartion is a valid model up to the LEP energy. If higher-orderback with a somewhat smaller asymptotic value. the beam energy E. This shows that the linear approximaother calculated optimum point high polarization came from [4, 5, 6]. The polarization decreases as expected withof polarization was measured. When changing Q, to some with and without HSM. The polarization degrees are takento about 8%. The beam was depolarized and the bui1d—up larization degrees are compared for different storage ringsclose to its value in physics coasts polarization degraded lated in beam energy. In fig. 3 the maximum observed powas achieved with polarization tunes. After setting Q, degrees measured at SPEAR and HERA can be extrapoQy and Q,. In the beginning polarization above 20%Figure 2: Polarization is shown for different tunes Q,,beam energy spread are assumed.perfections for all machines and no depolarization from theDaytimeare extrapolated in beam energy using eq. 1. Equal im17:00 18:® l9:® 20w 2l:® H:® 23:® ing (squares). The measurements from SPEAR and HERA0.05 Matching (triangles) and without Harmonic Spin Matchcompared for different storage rings with Harmonic SpinO.1Figure 3: Maximum measured polarization degrees are0,15O.2E [GeV]O.25O10203040506070809O0.3;vzrr·zM,Aco25 L Espanaarm:£M : ». wi .2* 2*.;+3 [LEP1MI;;;OEZ20E i ” I:1<:¤£;¤sb·¤mp• E-: 100 [- ,vrm>•,r>omsn.casn

Recent achievements in transverse spin-polarization at LEP

Recent achievements in transverse spin-polarization at LEP

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