Introduction

I've analyzed most of the BBC and ZDC data taken from Friday the 1st until today, Monday the 4th.  I compare the results for the residual transverse component from the 2 polarimeters

Method

All BBC physics asymmetry data comes from Ernst's webpage for scaler monitoring.  I get the angle of the beam from tan(theta) = TB/LR.  I use  BBC analyzing power of 1% to get the magnitude of the transverse component.

All ZDC physics asymmetry data comes from Oleksandr's webpage for zdc monitoring.  In this case I have to be a bit careful with the angles because Oleksandr always defines negative angles as south and positive angles are north.  This means for the yellow beam that a positive angle in the phi distribution fit means the beam is pointing to the left and a negative angle means the beam is pointing to the right.  For the blue it is reversed - a positive angle in the fit means the beam is pointing to the right and a negative angle means the beam is pointing to the left.  I use the analyzing powers at 200 GeV reported by Oleksandr to get magnitude of the transverse component.  These are 2.9+/-0.5% for yellow and 4.6+/-0.4% for blue. 

Taking the above into account, I report the angles as the angle of the transverse component relative to the vertical direction moving clockwise so that BBC and ZDC angles can be easily compared.

I combine the results for each run taken in the past 4 days by weighting according the uncertainties on the measured quantities.

Results

Note: Transverse component is the absolute transverse component, not the fractional transverse component (relative to the beam polarization) as is sometimes reported.

(1)Yellow Beam

(a)Magnitude of transverse component:

      BBC     0.0463+/- 0.0019

      ZDC    0.2977+/- 0.0712

(b) Angle relative to vertical:   

    BBC      0.7620+/-0.0413

    ZDC      0.3667 +/-0.1552

(2)Blue Beam

(a)Magnitude of transverse component

    BBC   0.0866+/-0.0019

    ZDC   0.1466+/-0.0266

(b)Angle relative to vertical:

    BBC   0.7380+/-0.0225

    ZDC   -0.9977+/-0.1322

Comments

The uncertainties on the ZDC are relatively large.   Also, the difference and the yellow and blue beam analyzing powers for the ZDC were not so large at 500 GeV.  Also it seems there is a real disagreement between to two for the direction the beams are pointing, even with the large uncertainties.  The BBC says both beams point to the right and the ZDC says the yellow points to the right and the blue to the left.