initial rotator adjustment for run-15

Run 16042070 showed a rather large azimuthal modulation for both yellow and blue beams.  The size and phase point, at face value, to a radial polarization component.  It should be noted, however, that there are numerous experimental issues; among them that the ZDC E.W coincidence currently does not fire at expected rates, there are bit issues in the scaler system, and that the local polarimeters have not been calibrated.  Nevertheless, the observation is consistent between ZDC-scaler, ZDC-trigger, and BBC-scaler analysis (at least qualitatively).

Part of a rotator current scan was made on Friday February 13.  This scan gave limited precision and was cut short due to an unexpected beam abort.  The currents were adjusted by 5A; up in inner Yellow and down in inner Blue.  The first higher-statistics run after the adjustment is run 16044139.

The difference is clear; 16042070 cannot be fit with a constant with good fit-probability, whereas 16044139 can.  The work, however, is far from done.  I see no basis for another scan until this work, or at least a large part of it, is done.

As to the online monitor and the fill-averages that are displayed; use caution for now.