[Halld-cal] FCAL non-linear correction

[Colin Gleason]

In testing out Igal's addition to the FCAL_Pi0HFA, I noticed that in my non
linear correction I do not include the inner or outer rings. I apply a
fiducial cuts on both photons of less than 20.785cm and greater than
108.4239cm. This effectively cuts out the first and last three rings. It
probably explains why the non linear correction does not correct as much
for the black and red lines. However, it looks like this lack of no non
linear correction translates into a reduced pi0 mass up to ring 10 or 11.
We're looking at a sub 1-2% effect here (ignoring block 1, which is sub 3%)
for standard GlueX running, so not a big deal with respect to that, but
obviously an issue for PrimeX. Maybe I can quickly recalculate the non
linear correction removing these fiducial cuts and Igal can rerun his
scripts to test the output? My hypothesis is that the inner rings will
shift closer to 1 and that the middle and outer rings will shift above 1,
which will lead to Igal having a similar conclusion
that doing the correction by ring is necessary for PrimeX.

I'm trying to jog my memory on why we did this. If I recall correctly there
were maybe a couple reasons: match the fiducial cuts with data, we do not
understand leakage in the inner rings and didn't want to add in a
correction that would be bias the rest of the detector, and we obviously
can not reconstruct pi0s in the outer rings.

-Colin

On Thu, May 14, 2020 at 10:10 AM Igal Jaegle <ijaegle at jlab.org> wrote:

> All,
>
> I made an entry in the FCAL logbook,
> https://logbooks.jlab.org/entry/3810625.
>
> It remains to be proven that one function and one set of parameters can be
> used for all rings.  In the standard GlueX FCAL energy calibration, after a
> new non-linear correction is applied, in principle the gains should be
> cross-checked and re-match if needed, and so on, until the gains and
> non-linear parameters are converging. I suggest that more robust QA/QC be
> used for the FCAL energy calibration (I will make a pull request with my
> improvements later today to FCAL_Pi0HFA) and that Colin continues the FCAL
> energy calibration until he sees no changes in the gains and the non-linear
> parameters for examples by using the QA that the gain should be updated
> only if the fabs(new gain-old gain)/old gain > 1-1.5% depending on the
> standard GlueX QA.
>
> tks ig.
>
> PS: I think, the classical approach while maybe more complicated, requires
> fewer iterations and is working at least for pi0!
> _______________________________________________
> Halld-cal mailing list
> Halld-cal at jlab.org
> https://mailman.jlab.org/mailman/listinfo/halld-cal



-- 
Colin Gleason
Postdoctoral Fellow
Indiana University
Department of Physics
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/halld-cal/attachments/20200515/03f69c7f/attachment.html>