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Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment

Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment. Polarimeter Development Team: (participating at COSY). KVI-Groningen : C.J.G. “Gerco” Onderwater*, Marl ène da Silva e Silva, N.P.M. “Klaas” Brantjes, Duurt J. van der Hoek , Wilburt Kruithof ,

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Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment

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  1. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment Polarimeter Development Team: (participating at COSY) KVI-Groningen: C.J.G. “Gerco” Onderwater*, Marlène da Silva e Silva, N.P.M. “Klaas” Brantjes, DuurtJ. van derHoek, WilburtKruithof, Oscar O. Versolato Indiana: Edward J. Stephenson*, Astrid Imig (BNL) COSY Jülich: Ralf Gebel, Andreas Lehrach, Bernd Lorentz, Dieter Prasuhn, Hans Stockhorst BNL: Vasily Dzordzhadze, Donald Lazarus, William M. Morse, Yannis K. Semertzidis Regis U.: Fred E. Gray Frascati: Paolo Levi Sandri, Graziano Venanzoni U. of Rome: Francesco Gonnella, Roberto Messi, Dario Moricciani Thanks to: Olaf Felden (COSY), Frank Hinterberger (Bonn), Rudolf Maier (COSY), Hans Ströher (COSY), Univ. Münster * Spokespersons for polarimeter development

  2. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment General Goal: Confine charged, polarized particles with a large electric field Watch for change of polarization direction perpendicular to E as signature for Electric Dipole Moment (EDM) Candidates: proton, deuteron, (3He)…can polarize, analyze Sensitivity: For ~ 10−29e∙cm expect 10−6rad in ~ 1000 s Polarimeter Requirements: High efficiency (useful events / particles lost from beam) Large analyzing power ~ 250 MeV Control of systematic errors as beam conditions change

  3. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment General Goal: Confine charged, polarized particles with a large electric field Watch for change of polarization direction perpendicular to E as signature for Electric Dipole Moment (EDM) Candidates: proton, deuteron, (3He)…can polarize, analyze Sensitivity: For ~ 10−29e∙cm expect 10−6rad in ~ 1000 s Polarimeter Requirements: High efficiency (useful events / particles lost from beam) Large analyzing power ~ 250 MeV Control of systematic errors as beam conditions change Must observe a small change (Δpy) during time of store. Goal:1% Extract beam slowly onto thick target at edge of beam. Scattered flux goes into downstream detectors (forward angle).

  4. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment General Goal: Confine charged, polarized particles with a large electric field Watch for change of polarization direction perpendicular to E as signature for Electric Dipole Moment (EDM) Candidates: proton, deuteron, (3He)…can polarize, analyze Sensitivity: For ~ 10−29e∙cm expect 10−6rad in ~ 1000 s Polarimeter Requirements: High efficiency (useful events / particles lost from beam) Large analyzing power ~ 250 MeV Control of systematic errors as beam conditions change Must observe a small change (Δpy) during time of store. Goal:1% Extract beam slowly onto thick target at edge of beam. Scattered flux goes into downstream detectors (forward angle). Forward angle elastic scattering (large spin-orbit distortions) Carbon target Include low Q-value reactions (similar analyzing power) Effective goal: 0.5

  5. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment How to manage systematic errors: (measuring left-right asymmetry) Usual tricks: Locate detectors on both sides of the beam (L and R). Repeat experiment with up and down polarization. Cancel effects in formula for asymmetry (cross-ratio). But this fails at second order in the errors.

  6. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment How to manage systematic errors: (measuring left-right asymmetry) Usual tricks: Locate detectors on both sides of the beam (L and R). Repeat experiment with up and down polarization. Cancel effects in formula for asymmetry (cross-ratio). From experiments with large induced errors and a model of those errors: But this fails at second order in the errors. Using the data itself, devise parameters: and rate W = L + R Calibrate polarimeter derivatives and correct (real time): Will this work? for both X and θ?

  7. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment R&D run at the Cooler Synchrotron (COSY) COSY ring: p = 0.97 GeV/c T = 235 MeV EDDA detector: Rings and bars to determine angles. Use EDDA detector Tube target, extracts along inside edge.

  8. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment d+C elastic, 270 MeV EDDA detector: Rings and bars to determine angles. available at COSY desired range Tube target, extracts along inside edge. Y. Satou, PL B 549, 307 (2002) FOM = σA2

  9. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment Target solution found at COSY: expanded vertical phase space beam core Electric field plates, apply white noise end view maximum allowed at COSY 15 mm Do enough particles penetrate far enough into the front face to travel most of the way through the target? This requires a comparison of the efficiency with model values.

  10. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment Target solution found at COSY: expanded vertical phase space beam core Yes, front back model 5.7 4.7 data 6.8 5.9 × 10−4 Values well below ~ 1% because of thin target and loss of small angles. Electric field plates, apply white noise end view maximum allowed at COSY 15 mm Do enough particles penetrate far enough into the front face to travel most of the way through the target? This requires a comparison of the efficiency with model values.

  11. Tests made at the KVI (2007) 18° 130 MeV polarized deuterons carbon ribbon target Phoswich scintillation detectors Best method: “cross ratio”, “square root” method where Calculation based on deuteron elastic scattering data at 130 MeV and measured beam polarizations. This method fails at second order in errors. “true” asymmetry u = p(+) – p(−), p(−) < 0 observed asymmetry

  12. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment Experimental approach at COSY: Work in one plane: Change beam position (Δx) or angle (Δθ). Watch vertical as well as horizontal effects, also tensor. Change rate during measurement. Cycle through all “error” points: Δx = −2, −1, 0, 1, and 2 mm Δθ = −5.0, −2.5, 0, 2.5, 5.0 mrad Cycle through 5 polarization states: Unp, V+, V−, T+, T− Record data as a function of time during the store.

  13. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment Determine properties of these “correction” derivatives for each observable. Is this description adequate? Do we need external measurements? Use a model of all systematic effects to: identify significant mechanisms for generating systematic error investigate the adequacy of the correction scheme

  14. Build a model framework of parametrized effects to investigate issues Include only what you need… First, separate rate and geometry effects. Make a linear fit to the data from the stores. Assume the zero rate point is independent of rate and can be used for the analysis of geometry effects. Use the slope for the study of rate effects. Each point is a specific observable that depends on polarization and ΔX or Δθ.

  15. Geometry model Parameters we know we need to include: EDDA Analyzing power: and Polarizations: pV and pT for the states V+, V−, T+, T− There is some information available from the COSY Low Energy Polarimeter. Logarithmic derivatives: Solid angle ratios: L/R D/U (D+U)/(L+R) Total so far: 19 parameters

  16. Parameters we found we needed: Rotation of Down/Up detector (sensitive to vertical polarization): θrot X – Y and θX – θY coupling (makes D/U sensitive to horizontal errors): CX, Cθ Ratio of position and angle effects (effective distance to the detector): X/θ = R Tail fraction: multiple-scattered, spin-independent, lower-momentum flux that is recorded only by the “right” detector (to inside of ring) F = fraction FX, Fθ sensitivities to position and angle shifts Total parameters: 26 Fitting revealed continuous ambiguity involving L/R and (D+U)/(L+R) solid angle ratios, the tail fraction, effective detector distance, and all polarizations. Choice was to freeze L/R solid angle ratio for front rings at one.

  17. Vector Analyzing Power Ay = 0.349(6) Vector Polarization py Quality of the fit [V−] 0.5370(4) [V+] −0.3954(4) [T+] −0.3399(4) [T−] 0.7311(4) 10% shifts measure vector asymmetry zero level set by L/R solid angle ratio and tail fraction tail fraction = 0.2985(2) with L/R solid angle ratio = 1 slopes given by slope difference measures “effective” distance to detector X/θ = 52.4(8) cm

  18. 1% Offset gives D/U solid angle ratio 1.0390(1) Beam X – Y and θX − θY coupling connects to horizontal beam motion Broken symmetry of ring detectors creates false rotation in vertical asymmetry and sensitivity to polarization. X coupling = −0.031(5) θ coupling = 0.036(2) rot = 0.0278(5) rad

  19. Tensor Analyzing Power AT = 0.0721(2) Tensor Polarization pT [V−] 0.1580(3) [V+] −0.0841(3) [T+] 0.4448(3) [T−] −0.7641(3) 1% Offset gives DU/LR solid angle ratio slope gives 1.3048(2) curvature gives difference from one compensates for tail fraction 0.00029(1) 1/rad2

  20. removes first order effects 0.1% slope gives slopes depend on earlier first-order terms curvature gives A’’/A = 0.00007(6) 1/rad2

  21. Rate Model: L Rate effects require a non-linear response to input rate. Detector rate L = C (1 + ε), C = unpolarized rate Rate effects can be L = L + hL2… For a simple asymmetry: εexp = ε [1 + hC(1 – ε2)…] L rate dependence For h > 0, there are excess events (pileup, more events crossing threshold…) This represents our case. For h < 0, there are lost events (PMT gain sag…) Higher order effects introduce polarization dependence. There is some evidence for quadratic X and θ dependence. Polarization dependence not needed for cross ratio rate dependence.

  22. Rate dependence results 1% Average rate means h > 0. Note polarization dependence.

  23. Conclusions 1 Angle points X points 10% Corrections for A and θ match. One index can be used for both.

  24. Conclusions 1 Angle points X points 10% 0.1% Corrections for A and θ match. One index can be used for both.

  25. Conclusions Chi square distribution for geometry fit 1 2 Angle points X points 10% 0.1% Reduced chi square is 1.7 Corrections for A and θ match. One index can be used for both. Reproduction of data by model is good; there are no unexplained features.

  26. 3 Tests were made with the beam shifting by 4 mm during the store. V+ polarization case uncorrected corrected for rate and geometry slope: −1.4 ± 28 × 10−6 /s Corrections work.

  27. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment T− polarization, 2 mm displaced Tests were made with high rate and displaced beam. corrected for rate and geometry uncorrected corrected for rate

  28. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment T− polarization, 2 mm displaced Tests were made with high rate and displaced beam. Corrections work. corrected for rate and geometry Scaling down: For deuteron EDM ring: position changes < 10 μm initial vertical ε < 0.01 gives control of systematics to < 30 ppb, well under requirement. uncorrected corrected for rate cross ratio: A’/A = 0.0055 ε = 0.01 Δp = 0.05 use (A’/A)ε2Δp Since asymmetry depends only on count rates and calibration coefficients, we get results in real time.

  29. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment Summary: It is possible to design a (deuteron) polarimeter with the efficiency and analyzing powers needed for the EDM ring. Thick target extraction keeps the efficiency high. Systematic errors may be corrected (in real time) using information contained within the left-right data set (assuming up and down polarization). A prior calibration of the sensitivity of the polarimeter to error terms involving geometry and rate changes is required. For the EDM search, a measurement of a small rotation should be possible with a systematic error after correction of less than one part per million.

  30. Pages for Further Discussion

  31. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment Development of the Storage Ring EDM Experiment (BNL) 1990’s: Complete muong−2 experiment. until Set upper bound on muon EDM (10−19e∙cm). 2003 Consider ways to enhance sensitivity. 2004: Deuteron EDM proposal submitted, denied. 2007: Letter of Intent submitted. Science and concept supported. 2008: Proposal submitted. 2009: Conceptual technical review completed successfully. 2010: Proposal accepted at BNL. Next: Seek DOE funding (project CD-0).

  32. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment What is the method? Place particles in storage ring with spin aligned along the velocity. EDM Signal: observe precession of spin in large radial electric field. E v Experiment: watch for spin that starts out along v to acquire a vertical component.

  33. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment What is the method? Place particles in storage ring with spin aligned along the velocity. EDM Signal: observe precession of spin in large radial electric field. E v Experiment: watch for spin that starts out along v to acquire a vertical component. Technical Challenge: Particles will not remain with spin along velocity but rotate in ring plane. The solution is different for the deuteron and proton. It determines the architecture of the ring.

  34. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment The Deuteron Solution: Deuteron anomalous moment = – 0.14. In one revolution, spin lags momentum. B Idea: Use electric field to enlarge orbit and revolution time while keeping B constant.

  35. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment The Deuteron Solution: Deuteron anomalous moment = – 0.14. In one revolution, spin lags momentum. Idea: Use electric field to enlarge orbit and revolution time while keeping B constant. For some ratio of E and B, the lengthened path will be just right for the spin to track the velocity. E field (21% diameter increase) (Small precessions will be used for systematic checks.)

  36. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment The Deuteron Solution: Deuteron anomalous moment = – 0.14. In one revolution, spin lags momentum. Idea: Use electric field to enlarge orbit and revolution time while keeping B constant. For some ratio of E and B, the lengthened path will be just right for the spin to track the velocity. E ~ 17 MV/m B ~ 6.8 kG R0 ~ 7 m Circumference ~ 80 m

  37. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment The Deuteron Solution: Deuteron anomalous moment = – 0.14. In one revolution, spin lags momentum. Ring includes: 2 injection kickers RF cavity solenoid 2 polarimeters Idea: Use electric field to enlarge orbit and revolution time while keeping B constant. For some ratio of E and B, the lengthened path will be just right for the spin to track the velocity. E ~ 17 MV/m B ~ 6.8 kG R0 ~ 7 m Circumference ~ 80 m

  38. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment The Proton Solution: E This ring is all electric (no magnetic bending).

  39. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment The Proton Solution: This ring is all electric (no magnetic bending). At low energy, the spin is stationary.

  40. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment The Proton Solution: This ring is all electric (no magnetic bending). At low energy, the spin is stationary. At p = 0.701 GeV/c, proton sees B = −γv×E, and spin tracks velocity.

  41. Managing Systematic Errors in a Polarimeter for the Storage Ring EDM Experiment The Proton Solution: This ring is all electric (no magnetic bending). At low energy, the spin is stationary. At p = 0.701 GeV/c, proton sees B = −γv×E, and spin tracks velocity. E ~ 17 MV/m radius ~ 25 m Circumference ~ 240 m

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