1. E166 Collaboration Meeting Princeton, 22-24 May 2006 e+ Analyzing Power K. Peter Schüler e+ Analyzing Power: what we know from old G EANT 3 simulations (an archeological excercise with some useful insights)

2. 2 expected and measured e+ asymmetries E166 Collaboration Meeting Princeton, 22-24 May 2006 e+ Analyzing Power K. Peter Schüler proposal – the ominous table 13measurements actual conditions were different in several ways: beam energy: 50 46.6 GeV beam current: 1 x 10 10 0.5 x 10 10 lens/spectrometer CsI-detector geometry background!!! to what extent will these differences affect the analyzing power and the expected asymmetries?

3. 3 Conditions assumed for G EANT 3 simulations E166 Collaboration Meeting Princeton, 22-24 May 2006 e+ Analyzing Power K. 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 P E = 0.07 CsI-Detector: angular photon acceptance: ±8 ° (layout 4b = proposal) angular photon acceptance: ±14 ° (layout 5a) G EANT 3 processes: bremsstrahlung (*) annihilation (*) (*) spin-dependent treatment, Compton (*) but only through 1st generation pair production photo effect Bhabha, Moller multiple Coulomb scattering

4. 4 Detector Acceptance E166 Collaboration Meeting Princeton, 22-24 May 2006 e+ Analyzing Power K. Peter Schüler layout 4b (proposal) vs. layout 5a 4b covers approximately the central crystal, 5a covers approximately the full 3x3 crystal array

5. 5 synopsis of geometries E166 Collaboration Meeting Princeton, 22-24 May 2006 e+ Analyzing Power K. Peter Schüler layout 4blayout 5a

6. 6 e+ Analyzing Power (energy-weighted) E166 Collaboration Meeting Princeton, 22-24 May 2006 e+ Analyzing Power K. Peter Schüler

7. 7 and by numbers … E166 Collaboration Meeting Princeton, 22-24 May 2006 e+ Analyzing Power K. Peter Schüler Layout 4bLayout 5a e+ energy (MeV) A (%) ΔA (%) ΔA/A A (%) ΔA (%) ΔA/A 1013. 93±0. 420. 03012. 97±0. 250. 019 913. 98±0. 460. 03313. 35±0. 280. 021 815. 16±0. 560. 03714. 30±0.330. 023 715. 75±0. 630. 04014. 73±0. 380. 026 615. 84±0. 740. 04715. 48±0. 450. 029 517. 07±0. 960. 05616. 28±0. 540. 033 419. 63±1. 240. 06317. 21±0. 720. 042 318. 57±1. 850. 10017. 02±0. 920. 054

8. 8 Positron Beam Polarizations E166 Collaboration Meeting Princeton, 22-24 May 2006 e+ Analyzing Power K. Peter Schüler spectrometer positron asymmetry (**) no. of analyzing pos. pol. current energy (*) Δ CsI-crystals power P e P e+ (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

9. 9 Summary E166 Collaboration Meeting Princeton, 22-24 May 2006 e+ Analyzing Power K. Peter Schüler original G EANT 3 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