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Hello everybody,
I have a few things to ask you related to the calibration with FEE. It's
a lot of stuff, I don't expect an answer right away, maybe we could
discuss some of these topics during today's meeting.
I'd like to give an update next Wednesday, so there's time to answer.

1)At which point of the simulation can I found "uncalibrated" data? I
mean, for example, after the readout simulation I can plot the histogram
of the seedhit energy, can I have the same histogram but with the 4096
dst channels values? I need those because..

2)When we'll have real data, I will have to fit those histograms and
associate the fitted values to the calibration points I'll have set. At
which point of the reconstruction will this be done?

3)Up to now, I've been getting the information from the simulated data
out (in a very inelegant way, I must confess) and analyzed and fitted it
with root. When we will have to calibrate the real data, will it have to
be all within hps-java? I've got no idea of how to perform fits within
the java framework....

now about the calibration points

4)I've been simulating the data using these drivers:

clusters are needed just to select the FEE, the information I use is the
SeedHit energy. Is this procedure ok to set the calibration points? i.e.
is the energy simulated in this way the closest possible to the real signal?

5)which data should I use to set the points?
I've been doing my studies on this set here:
/mss/hallb/hps/production/slic/beam-tri/2pt2/egsv3-triv2-g4v1_s2d6-readout20140522_[1-2500].slcio
(i.e. the slic output available on tape at JLAb), but if I get it right,
this has been done using v6 geometry. To confront v6, v7 and v8, I've
reconstructed 50 stdhep files ( about 0.1 second of beam) using the
three geometries to confront them. Unfortunately the statistics is very
low, so I can confront only some crystals, but in those with enough
population the differences between the three geometries is low. For
example, having around 5000 entries in the histrograms, the differece
between v7 and v3 is around 1% and between V7 and V8 is around 0.5%. 1%
difference meand a difference of about 15 MeV in energy, which is pretty
low, and I think we can live with that. What do you think?

6)Once I have the point, where should I put them?

and now on positrons

7)I've discussed with John the possibility to calibrate the shadowed
crystals using positrons in a FEE-fashioned way: taking the seed hit
spectrum of the positrons and dividing it by their momenta given by the
SVT, will give a distribution very similar to the one of FEE. In the
picture you can see it for crystal nr 4 (ix=-20, iy=5).

To generate these histograms I've used the reconstrucetd events
available on tape, specifically the "trigger tridents with pileup".

I think a calibration with positrons is possible, but is way more
complicated since we need information from both the Ecal and the SVT, so
it has to be performed after the reconstruction.
do we want to do it? is it really doable? How precise can it be (I'm
asking the SVT guys, since it depends mostly on the momentum
resolution)? Which MCdata should we use to set the points?

This is pretty much it.
thanks to everybody, any intel will be highly appreciated!

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