<div dir="ltr">Hi Matt,<span class="gmail-im" style="color:rgb(80,0,80)"><div><br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">For reference, Ilya, can you provide the gain constants relative to the nominal constants that you obtained for the inner two layers? These are masked in the trigger, so HV modifications here would be minimally invasive to the GlueX run, but may give us a chance to calibrate the blocks after the change.<br></blockquote><div><br></div></span><div> We talked after you left about implementing this. I should be able to get the HV modification done with relative ease with new constants.</div><div><br></div><div>-Colin</div></div><br><div class="gmail_quote"><div dir="ltr">On Fri, Nov 16, 2018 at 6:46 PM Shepherd, Matthew <<a href="mailto:mashephe@indiana.edu">mashephe@indiana.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div style="word-wrap:break-word;line-break:after-white-space">
<div><br>
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<div>Sasha and Ilya,</div>
<div><br>
</div>
<div>I apologize for having to leave abruptly this afternoon (our preschool has strict pickup times).</div>
<div><br>
</div>
<div>The progress that Ilya showed in reconstructing pi0's with the inner blocks is very nice!</div>
<div><br>
</div>
<div>It seems the clear issue here is the behavior of the two clusterizing algorithms. If the standard algorithm reconstructed clusters around the beam hole the blocks then we would have easily calibrated these and not be discussing it. Further,
it seems also the failure of the standard algorithm is a result of noise as there is a correlation between occupancy and blocks with no clusters.</div>
<div><br>
</div>
<div>Ilya: can you outline or share the various settings of your clustering algorithm? I suspect it is semi-standard where you look for a high energy "seed" and then add blocks to the seed. For example, what is your seed threshold? How are you
using timing of hits? Could you please share the specifics of the algorithm or point us to the code you use? </div>
<div><br>
</div>
<div>This is all very relevant as we discuss the reconstruction launch of the Spring 2018 data. If we are able to make small modifications to recover some tiny bit of acceptance in the inner region, then it would be worth doing. It could be as simple
as adjusting the seed threshold in the standard algorithm. </div>
<div><br>
</div>
<div>I am in favor of trying to adjust HV to balance gains of inner blocks. We may consider this prior to the end of the current GlueX run so that we may acquire some new data (subject to discussion with everyone else). For reference, Ilya, can you
provide the gain constants relative to the nominal constants that you obtained for the inner two layers? These are masked in the trigger, so HV modifications here would be minimally invasive to the GlueX run, but may give us a chance to calibrate the blocks
after the change.</div>
<div><br>
</div>
<div>I suspect that measuring Compton at the precision you desire will require all of these be balanced. I think the sooner we can get to that point, the better.</div>
<div><br>
</div>
<div>Regarding the outer layers:</div>
<div><br>
</div>
<div>I'm much less convinced that the gain constants there are meaningful. My suspicion is that your systematic high shift of gains is just shifting the standard noise peak at gamma gamma mass threshold to the pi0 location. It seems very hard to
believe all of the channels on the outside somehow have systematically underestimated gains by a factor of 5-10.</div>
<div><br>
</div>
<div>To clearly answer Sean's question regarding geometry, I attach a view (generated in 2006) of the *design* gap between the FCAL and BCAL. This view is drawn from the downstream end of the target (minimal case for BCAL "shadowing" of FCAL). The
innermost circle represents how the inner radius of the BCAL at the downstream end projects onto the FCAL. Beyond the end of the BCAL there are of course light guides, SiPMs, cables, etc. that will all further shadow the FCAL. The true overlap for photons
coming from the center of the target is more significant. I suspect calibrating the outer layer with photons originating from the target that have the majority of their energy deposited in a block in the outer layer is impossible.</div>
<div><br>
</div>
<div>Finally, I would like to be able to participate in your meetings. Please keep me up to date regarding schedules.</div>
<div><br>
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<div>Matt</div>
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<div><img id="m_-82112581412097049388442BBE6-D214-4B0B-8E74-85987E19C8B0" src="cid:AF88C6D5-7E31-47DF-9C0B-B93DD269D83A@hsd1.in.comcast.net"></div>
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<div><br>
<blockquote type="cite">
<div>On Nov 15, 2018, at 11:03 PM, Alexander Somov <<a href="mailto:somov@jlab.org" target="_blank">somov@jlab.org</a>> wrote:</div>
<br class="m_-8211258141209704938Apple-interchange-newline">
<div>
<div>Dear Colleagues,<br>
<br>
We are going to start discussing aspects critical for the PrimEx D <br>
experiments, such as<br>
<br>
- performance of the FCAL, luminosity determination, etc. <br>
<br>
during some of our weekly PrimEx D meeting. So far, we have mostly been <br>
focused on construction details of the Compton Calorimeter. The next meeting <br>
will take place tomorrow (November 16) in Hall D counting room at 4 pm. <br>
<br>
BlueJeans connection: <a href="https://urldefense.proofpoint.com/v2/url?u=https-3A__www.bluejeans.com_7572695553&d=DwMGaQ&c=lz9TcOasaINaaC3U7FbMev2lsutwpI4--09aP8Lu18s&r=VNruI5B3_Ie9AiOp0_GgpPscd-lfGLx1DNIPlMbQfwQ&m=tEnmUAGm3JkGTILHapYfLvRyW1MIaj79ELC-ro1TPAY&s=Gaqpj1imnGeSbXmDAFM8sO5OnLp2CJyFr_5qDQtWzqU&e=" target="_blank">https://www.bluejeans.com/7572695553</a><br>
Meeting ID: 7572695553<br>
<br>
The main topic for discussions:<br>
<br>
- calibration of the FCAL <br>
<br>
(some significant progress has been done in this direction, you will be <br>
surprised to see … )<br>
<br>
The meeting page will be available shortly.<br>
<br>
<br>
-------- <br>
<br>
We have created a mailing list <a href="mailto:primexd@jlab.org" target="_blank">primexd@jlab.org</a> for future communications.
<br>
In order to subscribe, send an email to: <br>
<br>
<a href="mailto:primexd-request@jlab.org" target="_blank">primexd-request@jlab.org</a><br>
<br>
Subject: subscribe<br>
<br>
<br>
<br>
Cheers,<br>
Sasha<br>
<br>
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</blockquote>
</div>
<br>
</div>
_______________________________________________<br>
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<a href="https://mailman.jlab.org/mailman/listinfo/halld-cal" rel="noreferrer" target="_blank">https://mailman.jlab.org/mailman/listinfo/halld-cal</a></blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div>Colin Gleason</div><div>Postdoctoral Fellow<br>Indiana University <br>Department of Physics</div></div></div>