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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 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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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>
<br class="Apple-interchange-newline">
<div class="">
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http-equiv="Content-Type" class="">
<div bgcolor="#FFFFFF" text="#000000" class=""> 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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charset=utf-8" 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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