History: AsymmetryCorrections

To extract GEn/GMn, the true "physics" asymmetry must be determined. Since the "raw" asymmetry immediately measured from the data must be corrected for false asymmetry contributions, dilution, and finite acceptance effects.

I recommend that you work through the algebra to understand the correction factors for the asymmetry. Here, I will start with the number of events N in the positive (+) and negative (-) helicity state and state the final expression.


while

and

likewise for N-.

What one finds, to first order in the false and true asymmetries, is:

where eta is the overall efficiency, and Q is the accumulated charge for each helicity state.

The sources for false asymmetries for GEn are:

1. Beam charge asymmetry (more accumulated charge in one helicity state than the other)
2. DAQ Livetime asymmetry
3. Electronic Livetime asymmetry
4. Tracking efficiecy asymmetry

The last three are due generally to the asymmetry in the background pion-production cross-section, which is ~1% for the Kine4 dataset.