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Hello all,<br>
<br>
I have generated a sample of minimum bias events using bggen. The
photon beam spectrum in this sample is the total photoproduction
cross section weighted by the coherent bremsstrahlung spectrum
evaluated with the standard GlueX collimator, between incident
photon energies 3GeV and 12GeV. This roughly corresponds to the
level-1 trigger.<br>
<br>
Here are the average event sizes at various stages in the production
pipeline for this sample. Note that this is the current state of
the simulation tools, not what you might remember from 6 months
ago. These event sizes are larger than you might remember hearing a
while back!<br>
<ol>
<li>bggen output:</li>
<ul>
<li>with MC information: 800 bytes</li>
<li>after stripping MC information: N/A<br>
</li>
</ul>
<li>hdgeant output:</li>
<ul>
<li>with MC information: 70KB</li>
<li>after stripping MC information: 22KB<br>
</li>
</ul>
<li>mcsmear output:</li>
<ul>
<li>with MC information: 102KB</li>
<li>after stripping MC information: 49KB</li>
</ul>
</ol>
<p>During the stripping process, I removed anything that was not
absolutely needed to store the hit information for the event. I
also removed the new tags added by David associated with saving
the full spectrum in the bcal, and incident particle information
there, even though the string "Truth" was not encoded in the tag
name. My goal was to strip things down to the absolute minimum
required to store the hits information.<br>
</p>
<p>Unfortunately, things are not as simple as the above table might
suggest. While I was not paying attention, scads of "truth"
information have crept in to taint the hits information that is
included in the stripped files above. For example, people working
on tracking in the CDC have mixed truth information into the hits
tags, as in the following example:<br>
</p>
<p> <cdcStrawHit maxOccurs="unbounded" d="float" dE="float"
itrack="int" ptype="int" t="float" /><br>
</p>
<p>What is track number doing inside this hits tag, you might
ask???? The equivalent and correct way to encode this same
information in hddm would be the following.<br>
</p>
<p><cdcStrawHit maxOccurs="unbounded" d="float" dE="float"
t="float><br>
<cdcStrawHitTruthInfo minOccurs="0" itrack="int"
ptype="int"/><br>
</cdcStrawHit><br>
</p>
<p>Encoded in the new way, it is easily stripped, but the
association is still there in the unstripped event. Encoded in
the original way, the entire tag is tainted with truth
information. If the substring "Truth" occurs in the tag, it
should be stripped in the final analysis. If not, it should be
completely clear of truth information and should be kept for the
final analysis.<br>
</p>
<p>Once we fix these problems, I will rerun the above stripping
exercise and we will get a better estimate for what the average
event size will be.<br>
</p>
<p>-Richard Jones<br>
</p>
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