In order to calculate the spin-observables defined in section it is necessary to measure the polarization of the incident proton flux as well as that of the resulting neutrons. The data from the high-energy beamline polarimeters described in section 4.1.3 was recorded as part of the same data stream as the information from the neutron polarimeter and was analyzed separately for each run at the same time that the neutron data was being analyzed. The weighted average beam polarization for each part of the run is shown in table .
Table: Proton beam polarizations for the individual parts of experiments E385 and E387. The uncertainties include both statistical uncertainties and uncertainties in the analyzing power of the analyzing reaction, .
The uncertainty indicated for the values of proton polarization are dominated by the uncertainty in the analyzing power of the analyzing reaction, , used in the beamline polarimeters. Portions of the polarization replay and analysis were conducted at Ohio University.