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Greetings,<br>
<br>
I am not attending today's meeting. Please fill me in on this
discussion.<br>
<pre class="moz-signature" cols="72">BR
MK
----------------------------------------
Michael C. Kunkel, PhD
Forschungszentrum Jülich
Nuclear Physics Institute and Juelich Center for Hadron Physics
Experimental Hadron Structure (IKP-1)
<a class="moz-txt-link-abbreviated" href="http://www.fz-juelich.de/ikp">www.fz-juelich.de/ikp</a></pre>
<div class="moz-cite-prefix">On 7/27/15 4:09 PM, Volker Crede wrote:<br>
</div>
<blockquote cite="mid:649F8CB7-BC1C-493D-AC2D-3F3AE4BE78CB@fsu.edu"
type="cite">
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Michael,
<div><br>
</div>
<div>I agree that the idea sounds correct, we have already
discussed this here. For this reason, Zulkaida applied your
"map" but unfortunately, it does not reproduce the holes in the
mass distributions.</div>
<div><br>
</div>
<div>- Volker</div>
<div><br>
</div>
<div><br>
<div>
<div>On Jul 27, 2015, at 3:40 AM, Michael C. Kunkel <<a
moz-do-not-send="true" href="mailto:mkunkel@jlab.org"><a class="moz-txt-link-abbreviated" href="mailto:mkunkel@jlab.org">mkunkel@jlab.org</a></a>>
wrote:</div>
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<div bgcolor="#FFFFFF" text="#000000"> Greetings,<br>
<br>
If you are correct, and something is not simulated
correctly, then wouldn't mapping the efficiencies of each
particle in z, p, theta and phi for both MC and data
suffice to correct for it?<br>
<pre class="moz-signature" cols="72">BR
MK
----------------------------------------
Michael C. Kunkel, PhD
Forschungszentrum Jülich
Nuclear Physics Institute and Juelich Center for Hadron Physics
Experimental Hadron Structure (IKP-1)
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="http://www.fz-juelich.de/ikp">www.fz-juelich.de/ikp</a></pre>
<div class="moz-cite-prefix">On 7/27/15 12:28 AM, Volker
Crede wrote:<br>
</div>
<blockquote
cite="mid:E063EFD1-9A4E-4203-9512-AC8E76249890@fsu.edu"
type="cite">
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charset=utf-8">
Michael,
<div class=""><br class="">
</div>
<div class="">As much as I was hoping for g11a to be
wrong, everything we have observed so far is very
consistent with g11a (normalization and angular
shape). At the moment, the g12 <span
style="font-family: 'Helvetica Neue';" class="">ω </span>cross
section in the forward direction is lower than g11a …
This cannot be correct. The g12 acceptance is better
than in g11a (the target was moved backwards) and
reaching 0.9 is reasonable. Mike Williams was also
close to that.</div>
<div class=""><br class="">
</div>
<div class="">The CBELSA/TAPS cross sections are
generally higher than the CLAS cross sections (across
the entire angular range). This is likely an issue
with the absolute normalization and not with the
angular shape. Applying your trigger map unfortunately
appears to pull up the forward direction relative to
the backward direction. If I remember correctly, the
CBELSA/TAPS γp → pπ<sup class="">0 </sup>cross section
was actually consistent with g1c.</div>
<div class=""><br class="">
</div>
<div class="">The reason for our lower <span
style="font-family: 'Helvetica Neue';" class="">ω </span>cross
section is that our acceptance is too good in the
forward direction and our suspicion is that dead
detector modules (drift chamber wires and perhaps also
TOF paddles) are not simulated correctly. I am afraid
something is not right with g12.</div>
<div class=""><br class="">
</div>
<div class="">- Volker</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
<div>
<blockquote type="cite" class="">
<div class="">On Jul 26, 2015, at 3:02 PM, Michael
C. Kunkel <<a moz-do-not-send="true"
href="mailto:mkunkel@jlab.org" class="">mkunkel@jlab.org</a>>
wrote:</div>
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Greetings,<br class="">
<br class="">
From what I see there are 2 things,<br
class="">
<br class="">
1) cos\theta 0.9 is very forward, I do not
even think we have good events past cos\theta
0.8. Especially with a 3 prong trigger.<br
class="">
<br class="">
2) The mapping I created does pull most
distributions high in the cos\theta > 0.67,
but as I said to Zulkaida and g12 members,
this is a known effect. I do not think g11 nor
g1c was actually all that accurate in the
forward direction. You, Volker, are the person
who put me onto the fact that CLAS might have
a forward acceptance issue, since your
analysis of the gp->ppi0 with TAPS showed a
higher XSection in the forward direction,
which also matched that of GRAAL and LEPS. <br
class="">
When I compare gp->ppi0 with g1c, yes g12
is higher in the forward direction, but so is
the rest of the world. Therefore unless there
are other measurements to coincide with g11's
or g12's measurement, I would not say that g11
is the "set in stone" measurement.<br class="">
<br class="">
<span style="font-family: 'Helvetica Neue';"
class=""></span>
<pre class="moz-signature" cols="72">BR
MK
----------------------------------------
Michael C. Kunkel, PhD
Forschungszentrum Jülich
Nuclear Physics Institute and Juelich Center for Hadron Physics
Experimental Hadron Structure (IKP-1)
<a moz-do-not-send="true" class="moz-txt-link-abbreviated" href="http://www.fz-juelich.de/ikp">www.fz-juelich.de/ikp</a></pre>
<div class="moz-cite-prefix">On 7/26/15 8:00
PM, Volker Crede wrote:<br class="">
</div>
<blockquote
cite="mid:FF91ED4F-7CC4-490C-BAF6-579364FA1DBF@fsu.edu"
type="cite" class="">
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class="">
<div class="">Hi Everybody,</div>
<div class=""><br class="">
</div>
<div class="">I know that we are all working
on finalizing various g12 analyses.
However, we found a serious issue with
our <span style="font-family: 'Helvetica
Neue';" class="">γp </span><span
style="font-family: 'Lucida Grande';"
class="">→</span><font class=""
face="Helvetica Neue"> pω cross section
that currently prevents us from moving
on. We are somewhat stuck and it may
affect the whole run group. </font></div>
<div class=""><font class="" face="Helvetica
Neue"><br class="">
</font></div>
<div class=""><font class="" face="Helvetica
Neue">The attached pictures show</font> the
3π invariant mass for the energy range
1650 - 1700 MeV and for forward angles of
the <span style="font-family: 'Helvetica
Neue';" class="">3</span>π system. A
nice <font class="" face="Helvetica Neue">ω
peak is visible and a massive hole on
the right side of the peak. This hole is
not supposed to be there (unless
somebody has a good physics argument).
The energy range is probably very low
for most of the g12 analyses. However,
the hole will slowly move to higher
masses with increasing photon energy but
it will not disappear. The other two
pictures show the same distribution if
one (1) uses events where only sectors
1, 3, 5 triggered or alternatively, (2)
only sectors 2, 4, 6 triggered. </font></div>
<div class=""><font class="" face="Helvetica
Neue"><br class="">
</font></div>
<div class=""><font class="" face="Helvetica
Neue">We assume the effect is based on
track inefficiencies, perhaps dead
regions in the drift chamber. In
principle, Michael Kunkel’s "trigger
map" should account for this since his
approach is based on comparing two- and
three-track events, i.e. it combines
trigger and track inefficiencies; the
idea is good. </font><font class=""
face="Helvetica Neue">In our analysis
however, this trigger map leads to an
overall disagreement with the g11 </font><span
style="font-family: 'Helvetica Neue';"
class="">ω cross section, whereas
Zulkaida's current cross section is in
fair agreement with g11 but exhibits
certain problematic regions, e.g. the
forward direction. These holes in the
mass distributions are not accounted for
by the Monte Carlo simulations and we
assume the effect is not in the MC.</span></div>
<div class=""><br class="">
</div>
<div class=""><font class="" face="Helvetica
Neue">We have a few questions we would
like some help with (and need to find an
answer for).</font></div>
<div class=""><font class="" face="Helvetica
Neue"><br class="">
</font></div>
<div class=""><font class="" face="Helvetica
Neue">1) Since it is still possible that
the problem is at our end, would anybody
be able to reproduce this problem for
us? The effect is so big that even a
quick and dirty look at it, will
probably work.</font></div>
<div class=""><font class="" face="Helvetica
Neue"><br class="">
</font></div>
<div class=""><font class="" face="Helvetica
Neue">2) We tried to knock out dead TOF
paddles as suggested in the analysis
note. The paddle numbers are available
in the data. However in the Monte Carlo,
the numbers appear to be available only
for the proton and not for the pions.
Has anybody else noticed this issue? How
do others knock out the paddles in the
MC? Or is this done automatically? </font><span
style="font-family: 'Helvetica Neue';"
class="">It is difficult to do this
based on measured angles since two
particles with the same polar and
azimuthal angles, one produced at the
beginning of the target and one at the
end, may hit different TOF paddles. The
g12 target was very long.</span></div>
<div class=""><font class="" face="Helvetica
Neue"><br class="">
</font></div>
<div class=""><font class="" face="Helvetica
Neue">3) The Monte Carlo “gpp"
options given in the analysis note do
not reproduce the holes in the mass
distributions. For this reason, we do
not know if dead wires are actually
simulated and to what extent. Can
anybody comment on this?</font></div>
<div class=""><font class="" face="Helvetica
Neue"><br class="">
</font></div>
<div class=""><font class="" face="Helvetica
Neue">This problem shows up in the </font><span
style="font-family: 'Helvetica Neue';"
class="">γp </span><span
style="font-family: 'Lucida Grande';"
class="">→</span><font class=""
face="Helvetica Neue"> pω channel but we
are concerned that it may also affect
the two-pion channel we are analyzing,
perhaps not as holes in mass
distributions but as general track
inefficiencies in certain regions of the
drift chamber. In the latter case, it
would extremely difficult to notice. </font><font
class="" face="Helvetica Neue">If so, it
can potentially affect any reaction that
uses Monte Carlo for the acceptance
correction. My understanding is that we
partially use the p</font><span
style="font-family: 'Helvetica Neue';"
class="">ω and the K</span>Λ cross
sections to make sure that the g12 MC,
trigger, etc. is working correctly.</div>
<div class=""><font class="" face="Helvetica
Neue"><br class="">
</font></div>
<div class=""><font class="" face="Helvetica
Neue">Best wishes,</font></div>
<div class=""><font class="" face="Helvetica
Neue"><br class="">
</font></div>
<div class=""><font class="" face="Helvetica
Neue"><span class="Apple-tab-span" style="white-space:pre"> </span>Volker</font></div>
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