Moller Measurements for E94-010, Sep-Dec 1998

Last updated: Fri, 16 July 1999 moller@jlab.org

Here a summary is given of the Moller measurements done for E94-010 running in 1998.

The longitudinal beam polarization is calculated as:
P=A/P_targ/cos(a)/Azz,
where

A is the asymmetry observed
P_targ is the target polarization. We used a constant value of P_targ=7.6% for all the data
a is the target angle with respect to the beam. This value was observed on a dial attached to the target mechanism and also was calculated using the measured counting rates at the given target position and at 90^o. In order to reduce the systematic error we always took an average of two measurements: one at about 20^o and another at about 160^o.
Azz is the analyzing power

It turned out that the polarization measured may depend on the slit-attenuator configuration in the injector (see the details here), namely on the phase of the laser. At the E94-010 period no note of the injector settings were done and it is not possible to reconstruct the phase-attenuator-slit configuration. However, since the current for the experiment was about 15uA only, one may expect that the phase was tuned to the middle of the distribution.

For the first period of 1.7 GeV 7 Moller measurements have been done. The beam tune was not very good during this period (once the Moller detector was damaged by radiation). This lead to difficulties in measuring the target angle using the event rates. Therefore the statistical error for these 7 points is increased by adding to it 0.5% (absolute) in quadratures.

 day, since Sep 1   Polarization  sign
      28.7         69.5 +/- 0.6    -1.
      29.5         68.1 +/- 0.6    -1.
      31.7         68.0 +/- 2.1    -1.
      33.8         68.0 +/- 0.6     1.
      35.7         67.5 +/- 0.5     1.
      41.9         67.8 +/- 0.6     1.
      44.7         68.1 +/- 0.6     1.
      46.5         69.7 +/- 0.4     1.
      48.1         71.7 +/- 0.2     1.
      53.8         71.7 +/- 0.2     1.
      57.8         72.6 +/- 0.2     1.
      61.5         73.1 +/- 0.2     1.
      67.7         73.1 +/- 0.2    -1.
      70.3         72.9 +/- 0.2    -1.
      74.3         72.1 +/- 0.2    -1.
      84.3         73.2 +/- 0.3     1.
      93.4         70.2 +/- 0.2    -1.
      95.5         70.8 +/- 0.2    -1.
     100.5         70.6 +/- 0.2    -1.
     100.9         71.0 +/- 0.2     1.
     104.6         72.3 +/- 0.2     1.
     106.9         73.0 +/- 0.2    -1.
     110.7         71.4 +/- 0.2    -1.
     111.9         73.2 +/- 0.2    -1.
     113.7         71.3 +/- 0.2    -1.
     115.2         72.4 +/- 0.2    -1.

The Moller results, along with the Mott polarimeter results are presented on a plot. The PAW macro which creates this plot is available here.