I have spent some time trying to calibrate the FMS during the recent Au-Au running (see previous drupal posts)
While the calibrations done with Au-Au data looked pretty good, it was unclear if there were unknown biases in the calibration method applied  within the Au-Au environment.

 A decision was made to not make voltage changes based on this calibration, at least until we could look at the data in the more friendly dAu environment. 
 
 Last niight first dAu beam arrived and 2 million FMS triggers were collected for early analysis (runs 17132053 and 17132054). 
Using my calibration from AuAu, I have taken a quick look at the mass distributions from dAu data, as a check on the quality of that calibration.

The calibration goal is to get the masses right for pions of near 40 GeV for small cells and near 28 GeV in large cells. 
Below are the mass plots for the small cell region on the left and the large cell region on the right.

 My conclusion is that this Au-Au calibration does look pretty good in the dAu environment. Nominal masses are within about 3-5 % of the goal and the peaks are quite narrow.

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Calibration with day 132 dAu data:

While the peaks, on average, look ok to about 5%, what can happen is if the glass darkens, cells that were weak get weaker and contribute less to the trigger and thus less to the pi0 peak. Only by calibrating again with the pp data can we learn what changes are really occuring.

Calibration iteration is ongoing but after several hours of iteration, the following shows the ratio of gains implied by additional calibration to gains before (based on Au-Au calibration).

Iteration continues!