1. COMPTON POLARIMETRY Compton Int. Point  detector e - detector Hall A Laser Polarization (1.5% prelim syst error at previous meeting) Error budget  analysis

2. Optical Setup Laser /4 plates CIP Exit Line Transfer Function

3. Exit Line x x y y Wollaston Prism Integrating Sphere S1 Integrating Sphere S2  Incoming Polarization Ellipse TE pol. state TM pol. state /4 plate Slow 9.8 6 8.8 6 Stokes Parameters: P 0,P 1,P 2,P 3

4. /4 Scans Lisa, Deepa and Sirish S 1 +KS 2 =P 0 Raw measurement Intercalibrated after fitting K S 1 -KS 2 =f(P 1,P 2,P 3 )  

5. /4 Scans LEFT RIGHT (sign corrected )    = 36.0 K 1.0 DOCP = 98.0 K 0.3  = -32.4 K 1.0 DOCP = - 97.8 K 0.3 Scan # 

6. Transfer Function Phase shift  sp=  s-  p + rotation  sp Mirror M e Mirror M s Mirror M 3 Measurement in exit line MODEL: Polarization at CIP Studied during installation in 1999…

7. Polarization at CIP Validation of transfer function 0.25% Cavity Installation Transmission through M e 0.1% Transmission through M s 0.1% Coupling 0.1% Birefringence 0.05% DOCP at exit line 0.2%  at exit line 0.05% Variation in time 0.05% Total ~0.4% Assumed from 1999 study This work DOCP Left = 99.1K0.4% DOCP Right =-99.1K0.4% DOCP Left = 99.9K0.6% DOCP Right =-99.3K0.6% 2005 data 1999 data

8. Polarization History Very stable over the whole run.  DOCP (in time) < 0.05% But 0.5% variation between 1999 and 2005 not understood. Real effect or bad transfer function?

9. /4 Scans No sensitivity to M3 orientation 0.5% in DOCP  /4 is 1.4 deg off Not likely… Angle of the 1 st /4 DOCP (%) Angle of mirror M 3 No obvious explanation:  Add an extra 0.5% syst. error.  Total error = ~0.7% DOCP Left = - DOCP Right = 99.1K0.7%

10. Polarization for 4 He run Error Budget: P  1.50% Resp. Func.1.25% Dead Time1.00% Pile up 1.00% Rad. Corr.0.25% TOTAL2.50% 0.70% ~2% Regular /4 scans Check real polar at CIP after the run by removing the cavity. One more analysis cross-check with the integrating method. 2005 Run:

11. Updated Results P e = 86.90 K 0.25 (stat) K 1.7 (syst) % P e GUN2 = 76.30 K 0.12 (stat) K 1.5 (syst) % P e GUN3 = 89.22 K 0.13 (stat) K 1.8 (syst) % Hydrogen Helium