Introduction

• Several runs were taken for ZDC polarimetry.  See this elog: http://online.star.bnl.gov/apps/shiftLog/logForDay.jsp?day=3/1/2009
• Runs *35 and 36 were taken with the same thresholds while *37 had a different threshold. 
• The reported polarizations from CAD are 18.5% from the yellow beam and 25% for the blue beam.

 ADC Spectra for the Run 1060035

Note: Plots for other runs are given as attachments!

 Figure 1: East ZDC calorimeter ADC for sum and each individually.

Figure 2: West ZDC calorimeter ADC counts.

Figure 3: East ZDC SMD vertical strip ADC spectra.

Figure 4: East ZDC SMD horizontal strip ADC spectra.

Figure 5: West ZDC SMD vertical strip ADC spectra.

Figure 6: West ZDC SMD horizontal strip ADC spectra.

An east ZDC SMD strip is empty because it was unplugged for a timing scan. 

Pedestal and Gain Corrections

Next we correct the SMD strip spectra for pedestals and gains.  As can be seen in the figures above, the pedestal is 0 for all the strips (this seems strange).  The gain correction is obtained by fitting the slope of each strip and applying a correction back to the average gain for all the strips.  The fits are given in the attachment fits_mar0209.

Spin Bit Pattern

We get the raw spin bit pattern from cdev and correct it by shifting the blue beam to account for the abort gap.  The corrected patterns are used as arrays, as shown below:

 static const int yellowPat[120] ={1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 0, -1, 0, -
1, 0, 1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 0, -1, 0, -1,
 0, 1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 0, -1, 0, -1, 0
, 1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 0, -1, 0, -1, 0,
1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 0, -1, 0, -1, 0, 1, 0, 1, 0, -1, 0, -1, 0, 0,
 0, 0, 0, 0, 0, 0, 0};

static const int bluePat[120] ={1, 0, -1, 0, 1, 0, -1, 0, -1, 0, 1, 0, -1, 0, 1,
 0, 1, 0, -1, 0, 1, 0, -1, 0, -1, 0, 1, 0, -1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0,
1, 0, -1, 0, 1, 0, -1, 0, -1, 0, 1, 0, -1, 0, 1, 0, 1, 0, -1, 0, 1, 0, -1, 0, -1
, 0, 1, 0, -1, 0, 1, 0, 1, 0, -1, 0, 1, 0, -1, 0, -1, 0, 1, 0, -1, 0, 1, 0, 1, 0
, -1, 0, 1, 0, -1, 0, -1, 0, 1, 0, -1, 0, 1, 0, 1, 0, -1, 0, 1, 0, -1, 0, -1, 0,
 1, 0, -1, 0, 1, 0};
 

Results

These results are only for the first 2 runs, which had the same thresholds.  We analyze the square root asymmetries, as in STAR note 480.  Unlike in the analysis presented in that note, we now have 4 spin states.  The asymmetries are extended for the 4 spin states to two different types.  One type is an average over the blue beam which proportional to the yellow beam analyzing power.  The other type is an average over the yellow beam which is proportional to the blue beam analyzing power.  The empty strip in the East ZDC vertical shows up in east asymmetry plots as a point at 0 with no error bar.

Figure 1: Phi asymmetries, averaging over the blue beam.  We see that the west asymmetry seems consistent with zero.  The fit is to a sine function with an amplitude (p0) and a phase (p1).  With a polarization of about 20%, this implies a yellow beam analyzing power of 0.003/0.20 = 0.02.

Figure 2: Phi asymmetries, averaging over the yellow beam.  The east asymmetry seems consistent with zero.  The west asymmetry implies an analyzing power of 0.005/0.20 = 0.03.