<div dir="ltr">Hi Matt,<div><br></div><div>I think it's reasonable to have the calibrated hit objects (DFCALHit in this case) objects be calibrated to be in GeV, no matter whether they come from data or simulation.</div><div><br></div><div>The multiplicative factors you are looking for are applied in the DFCALHit_factory class, both for the overall multiplicative factor and per-block gain corrections. The current scale factor that is applied is 1.6E-5 GeV / ADC count. This factor is currently being loaded from the CCDB - I can send you some instructions on how to change that when you're ready. </div><div><br></div><div>Cheers,</div><div>Sean</div>
</div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, Sep 18, 2014 at 5:45 AM, Matthew Shepherd <span dir="ltr"><<a href="mailto:mashephe@indiana.edu" target="_blank">mashephe@indiana.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
Hi Richard, David, and Sean,<br>
<br>
I'm looking for advice as to where/how to compartmentalize<br>
the FCAL calibration. (In writing this down,<br>
it helps me think through the problem -- perhaps there<br>
are other similar problems.)<br>
<br>
HDGEANT reports energy deposited in a block, however<br>
this still needs "calibration" (now done at post-reconstruction<br>
shower level) due to systematic shifts resulting from<br>
energy loss. This is now done in DFCALShower_factory<br>
which is a level above the clusterizer: DFCALCluster_factory.<br>
<br>
The FADCs will report a pulse integral for each block.<br>
This needs to be converted to an energy. Arguably this<br>
should be done with an overall (probably fixed) multiplicative constant<br>
that sets the rough scale for pulse integral -> energy and<br>
then a second, per block, "gain factor" that is a<br>
run-dependent constant near unity. We can estimate<br>
the overall scale constant from beam tests to try<br>
to get the right scale for the initial run. We'll try to<br>
gain balance all channels based on PMT test data so<br>
the individual block gains can start out at 1.<br>
<br>
The question is, do we calibrate the detector such<br>
that the result of calibration is actual energy in GeV or<br>
the output of HDGEANT? (Maybe the difference between<br>
these is imperceptible, but I don't think it will be.)<br>
<br>
I think what we want to do is calibrate such that it is<br>
actual energy in GeV. Then we want to adjust the<br>
shower-level calibration appropriately. What we do<br>
NOT want to do is have a branch that applies different<br>
shower level correction for MC and data. This means<br>
that, post run, we need to devise an algorithm to<br>
produce the same calibrated block-level energy from<br>
the energy deposited per bock as recorded by HDGEANT.<br>
I don't think there is a way to know in advance if<br>
this is a single common algorithm for all blocks or<br>
will need tuning on a block by block basis. (We<br>
may need additional constants.)<br>
<br>
To prepare for actual data, we will generate EVIO<br>
output of HDGEANT and then try to calibrate the block<br>
level constants using the output of DFCALCluster_factory.<br>
<br>
We can then look at invariant mass of clusters (no<br>
shower level energy correction applied) and that should<br>
peak at the pi0 mass. Applying shower-level nonlinearly<br>
corrections, which will have to be derived later, should<br>
improve resolution, but not necessary from the outset<br>
(and may want to be turned off if it is not working<br>
properly).<br>
<br>
Where can I find the code that applies this overall<br>
multiplicative constant to convert pulse integral to<br>
energy (and what is assumed value in the current EVIO<br>
output plugin)? Where do the block level constants<br>
get applied? Sean has given me some preliminary<br>
info on how to rewrite these.<br>
<br>
Thanks,<br>
<br>
Matt<br>
<br>
---------------------------------------------------------------------<br>
Matthew Shepherd, Associate Professor<br>
Department of Physics, Indiana University, Swain West 265<br>
727 East Third Street, Bloomington, IN 47405<br>
<br>
Office Phone: <a href="tel:%2B1%20812%20856%205808" value="+18128565808">+1 812 856 5808</a><br>
<br>
</blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr">Sean Dobbs<br>Department of Physics & Astronomy <br>Northwestern University<br>phone: 847-467-2826</div>
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