[Halld-cal] updated FCAL mc response study

[Shepherd, Matthew]

Hi Richard,

My understand is that you have reproduced the effect that I originally documented:  the energy response of the FCAL in the MC somehow changed and is now not correctly calibrated.  This is the original observation that motivated the issue.  From what I can tell, you seem to have verified that there is a problem.

This problem was first documented in this log entry:

https://logbooks.jlab.org/entry/3621347

What I really wanted to know is:  why did the response of the FCAL in the MC change?  For this, we have seem to have no answer.

So, we can retune the MC calibration of FCAL and mark the issue as "resolved."  But without understanding the reason the issue emerged, then it may sneak up again.

Matt


On Mar 23, 2019, at 4:39 PM, Richard Jones <richard.t.jones at uconn.edu<mailto:richard.t.jones at uconn.edu>> wrote:

Hello Matt and all,

I have updated my FCAL mc response study to single-photon events (0-8 GeV) in the forward direction. This shows the final adjustment in the energy scaling factors in hdgeant and hdgeant4. Unless I hear something to the contrary, I consider the energy scale issue reported on github Jeffersonlab/hdgeant4 to be resolved, if someone could agree and make it as resolved.

Also shown in the updated report is a new timing comparison study, where I used the position recorded for the fcal shower together with the mc generated vertex information to produce a time-of-flight corrected shower time, which should be zero if the reconstruction and simulation are consistent. Notice that there is still a residual time-walk that we might want to understand and correct.

https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=3852

-Richard Jones

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