Hi Tim,

The assumption that the energy maps uniquely to an x-position on the Ecal face is actually found from simulation. We simulated particles at fixed energy from small energies (which would cover e+e- events of interest) through FEE energies at all theta, phi combinations to map onto the Ecal. The lack of correction needed to the cluster y-position on pg 11 from here https://misportal.jlab.org/mis/physics/hps_notes/viewFile.cfm/2014-001.pdf?documentId=1 further supports that the conclusion seems OK. The actual energy calibrations are documented here: https://misportal.jlab.org/mis/physics/hps_notes/viewFile.cfm/2016-002.pdf?documentId=18 which also include simulations performed in the same manner. No large y-variations were seen other than what happens at the edge so it seems ok to first order to bin in x, and then apply the correction in y. I believe that the lack of variation seen in y on the Ecal (such as in Figs 4-10) would indicate that there is not a huge dependence. It looks like I used the HPS-EngRun-2015-Nominal-v3 geometry which we should check includes 3D field mapping?

I am more inclined to say that the energy corrections were never studied for the 2016 data, specifically. While they were parameterized in terms of energy measured, there is some difference with the field/beam energy ratio between 2015 and 2016 which I would think would have a stronger effect on the relevance of the corrections. They have never been fully vetted to the same level that the 2015 corrections were, but they seemed to put the FEE peak in the generally correct place. 

Also, I should mention that the simulations used for the gain corrections to the crystals, used FEE particles (for all theta/phi combinations from the target), but they did not have a significant distribution in y (more variation in x).


On Feb 25, 2019, at 3:38 PM, Nelson, Timothy Knight <[log in to unmask]> wrote:


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