E166 Collaboration MeetingPrinceton, 22-24 May 2006
e+ Analyzing Power K. Peter Schüler
e+ Analyzing Power:what we know from old GEANT3 simulations
(an archeological excercise with some useful insights)
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expected and measured e+ asymmetries
E166 Collaboration MeetingPrinceton, 22-24 May 2006
e+ Analyzing PowerK. Peter Schüler
proposal – the ominous table 13 measurements
actual conditions were different in several ways: beam energy: 50 46.6 GeV
beam current: 1 x 1010 0.5 x 1010
lens/spectrometer CsI-detector geometry
background!!!
to what extent will these differencesaffect the analyzing power and theexpected asymmetries?
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Conditions assumed for GEANT3 simulations
E166 Collaboration MeetingPrinceton, 22-24 May 2006
e+ Analyzing PowerK. Peter Schüler
Positron Beam at Reconversion Target:• quasi-monochromatic with Gaussian E/E = 20% • zero spatial width and angular divergence• centered on reconversion target
Reconversion Target:• 0.5 r.l. W• 12.5 mm upsteam of active region of iron
Analyzer Iron:• 50 mm dia. x 75 mm long • PE = 0.07
CsI-Detector:• angular photon acceptance: ±8 ° (layout 4b = proposal)• angular photon acceptance: ±14 ° (layout 5a)
GEANT3 processes:• bremsstrahlung (*)• annihilation (*) (*) spin-dependent treatment,• Compton (*) but only through 1st generation• pair production• photo effect• Bhabha, Moller• multiple Coulomb scattering
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Detector Acceptance
E166 Collaboration MeetingPrinceton, 22-24 May 2006
e+ Analyzing PowerK. Peter Schüler
layout 4b (proposal) vs. layout 5a
4b covers approximately the central crystal,5a covers approximately the full 3x3 crystal array
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synopsis of geometries
E166 Collaboration MeetingPrinceton, 22-24 May 2006
e+ Analyzing PowerK. Peter Schüler
layout 4b layout 5a
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e+ Analyzing Power (energy-weighted)
E166 Collaboration MeetingPrinceton, 22-24 May 2006
e+ Analyzing PowerK. Peter Schüler
0
2
4
6
8
10
12
14
16
18
20
0 2 4 6 8 10 12
e+ Energy (MeV)
An
aly
zin
g P
ow
er
(%)Layout 4b Layout 5a
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and by numbers …
E166 Collaboration MeetingPrinceton, 22-24 May 2006
e+ Analyzing PowerK. Peter Schüler
Layout 4b Layout 5a
e+ energy(MeV)
A(%)
ΔA(%)
ΔA/AA
(%)ΔA(%)
ΔA/A
10 13. 93 ±0. 42 0. 030 12. 97 ±0. 25 0. 019
9 13. 98 ±0. 46 0. 033 13. 35 ±0. 28 0. 021
8 15. 16 ±0. 56 0. 037 14. 30 ±0 .33 0. 023
7 15. 75 ±0. 63 0. 040 14. 73 ±0. 38 0. 026
6 15. 84 ±0. 74 0. 047 15. 48 ±0. 45 0. 029
5 17. 07 ±0. 96 0. 056 16. 28 ±0. 54 0. 033
4 19. 63 ±1. 24 0. 063 17. 21 ±0. 72 0. 042
3 18. 57 ±1. 85 0. 100 17. 02 ±0. 92 0. 054
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Positron Beam Polarizations
E166 Collaboration MeetingPrinceton, 22-24 May 2006
e+ Analyzing PowerK. Peter Schüler
spectrometer positron asymmetry (**) no. of analyzing pos. pol. current energy (*) Δ CsI-crystals power Pe Pe+
(A) (MeV) (%) (%) (%) (%) (%) (%)
100 3.7 0.57 0.17 5 19.0 ± 1 7.0 43 ± 13 120 4.5 0.88 0.10 5 18.0 ± 1 7.0 70 ± 9 140 5.2 1.03 0.08 5 16.8 ± 1 7.0 88 ± 9 150 5.6 0.78 (*) 0.10 (*) 5 16.0 ± 1 7.0 70 ± 10 160 6.0 0.83 0.12 5 15.8 ± 1 7.0 75 ± 12 180 6.7 0.89 0.21 5 15.8 ± 1 7.0 80 ± 20 180, ferrofl. 6.7 0.98 0.21 5 15.8 ± 1 7.0 89 ± 20
140 5.2 1.08 0.10 2,4,6,8 ? 7.0 ? 140 5.2 1.06 0.07 2,4,5,6,8 16.0 ± 1 7.0 96 ± 9 140 5.2 0.91 0.07 1-9 16.0 ± 1 7.0 81 ± 10
(*) based on preliminary values shown by Ralph in Vienna (Nov. 2005) (**) based on Zeuthen analysis from 27. Feb. 2006
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Summary
E166 Collaboration MeetingPrinceton, 22-24 May 2006
e+ Analyzing PowerK. Peter Schüler
• original GEANT3 analyzing power generated in 2003 is essentially still valid for the actual experimental conditions in E166• analyzing power decreases only modestly between single central crystal and full 3x3 crystal array• positron beam polarization is indeed large