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Greetings,<br>
<br>
Can you overlay the MxP^2 with pion mass setting on this plot? Using
the same kinematic cuts except with pion pid?<br>
<br>
<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 7/9/15 1:11 AM, Amaryan, Moskov
wrote:<br>
</div>
<blockquote cite="mid:A80FBF5B-F5A5-4D58-8F5F-C7391E8F5A6D@odu.edu"
type="cite">
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<div style="word-wrap:break-word">Dear all,
<div><br>
</div>
<div>I attach a plot with Mx(p)^2 and M(e+e-\gamma)^2
distributions overlaid. Statistics of both histograms are the
same,</div>
<div>however, as one can see there is no peak of eta in the
invariant mass squared, data are from g11.</div>
<div>Invariant mass has no eta in it similar to what Michael
showed for g12.</div>
<div>One can think of two possibilities, either these are true
eta’s decaying to e+e-\gamma, or these are remnants of
eta->pi+pi-gamma events.</div>
<div>The latter hypothesis was ruled out by plotting invariant
mass of pi+pi-\gamma or missing mass of proton for pion mass
assignment</div>
<div>for the same events that make Mx(p)^2 under lepton
assignment.</div>
<div><br>
</div>
<div>Best regards,</div>
<div>Moskov.</div>
<div><br>
<div>
<div>On Jul 8, 2015, at 11:02 PM, Amaryan, Moskov <<a
moz-do-not-send="true" href="mailto:MAmaryan@odu.edu">MAmaryan@odu.edu</a>>
wrote:</div>
<br class="x_Apple-interchange-newline">
<blockquote type="cite">
<div style="word-wrap:break-word">Hi Michael,
<div><br>
</div>
<div>Thanks for your message, looks interesting. </div>
<div><br>
</div>
<div>However we have shown in the CAA and also Georgie
has shown it in our meetings that invariant mass of
pi+pi-\gamma</div>
<div>resolution is much worse than missing mass of
proton. The reason is energy resolution of the final
state photon and</div>
<div>vertex resolution as momentum of the photon is
defined through both of these, energy and vertex.</div>
<div>Therefore we use missing mass of proton with other
cuts, which use pion mass assignment to \pi^+ and
\pi^-.</div>
<div><br>
</div>
<div>Now what I have shown on Tuesday, was missing mass
of proton with electron (positron) mass assignments.</div>
<div>There we clearly see a peak of eta. The mass
assignment is arbitrary, of course, but requirement of
missing mass squared </div>
<div> of pe+e- to be around zero (<0.01 GeV) and
missing energy of pe+e- to be E_x>0.2 GeV makes
this selection definite, not arbitrary.</div>
<div>And the fact that we see peak of eta is a proof
that some of pi+pi- tracks are actually e+e- pairs</div>
<div><br>
</div>
<div>The plot you sent around doesn’t show a peak of eta
very clearly in the best topology with EC/CC, but one
can imagine that with more statistics </div>
<div>the eta peak will be visible. However without
EC/CC there is no signature of eta whatsoever. Would
it be visible in the missing mass of proton in g12?</div>
<div><br>
</div>
<div>It wouldn’t make sense for me to argue that PID on
leptons improves invariant mass e+e-\gamma, of course
it does. </div>
<div><br>
</div>
<div>The question was which fraction of events that make
eta in the missing mass of proton with e+e-\gamma
assignment is due to events that were </div>
<div>from pi+pi-\gamma final state.</div>
<div> I think we have shown that this fraction is
negligible. </div>
<div><br>
</div>
<div>It will be interesting to compare missing mass of
the proton squared from g11 and g12 (for pe+e-gamma
final state) to see if because of different </div>
<div>acceptances these two data sets have similar or
very different numbers of eta’s.</div>
<div><br>
</div>
<div>It appeared that ntuples we are using from g11 have
been eloss applied. In this case eloss for pions and
leptons will be the same, I am not sure how different
they should be, but the fact that we see peaks of pi0
and eta in the missing mass of proton is indicative
that in the first approximation we can neglect eloss
uncertainties.</div>
<div><br>
</div>
<div>Best regards,</div>
<div>Moskov.</div>
<div><br>
</div>
<div>
<div>
<div>On Jul 8, 2015, at 1:33 PM, Michael C. Kunkel
<<a moz-do-not-send="true"
href="mailto:mkunkel@jlab.org">mkunkel@jlab.org</a>>
wrote:</div>
<br class="x_Apple-interchange-newline">
<blockquote type="cite">Greetings,<br>
<br>
So I was curious to reproduce my study on pion
contamination without the use of CC or EC
quantities.<br>
I am attaching a plot that shows G12 data that
shows 3 lines.<br>
Red: G12 data with eloss on pions, pion mass
setting, invariant mass PipPimGam; conditions
Ngamma > 0 &&
abs(mm2_PPipPimGam)<0.01 && mE_PPipPim
> 0.2<br>
<br>
Blue: G12 data with eloss on leptons,lepton mass
setting , invariant mass EpEmGam; conditions
Ngamma > 0 && abs(mm2_PEpEmGam)<0.01
&& mE_PEpEm > 0.2<br>
<br>
Cyan: G12 data with eloss on leptons,lepton mass
setting , invariant mass EpEmGam; conditions
Ngamma > 0 && abs(mm2_PEpEmGam)<0.01
&& mE_PEpEm > 0.2 && lepton PID
through CC and EC. Histogram is scale by x10<br>
<br>
<br>
As I concluded years ago, and is seen in the
histogram, without CC or EC, the eta peak cannot
be reproduced in the proper place.<br>
<br>
Total data used:1/463 of g12 data set.<br>
<br>
Hope this helps.<br>
<br>
<br>
BR<br>
MK<br>
----------------------------------------<br>
Michael C. Kunkel, PhD<br>
Forschungszentrum Jülich<br>
Nuclear Physics Institute and Juelich Center for
Hadron Physics<br>
Experimental Hadron Structure (IKP-1)<br>
<a moz-do-not-send="true"
href="http://www.fz-juelich.de/ikp">www.fz-juelich.de/ikp</a><br>
<br>
<br>
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<div style="word-wrap:break-word">Prof. Moskov
Amaryan<br>
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<div style="word-wrap:break-word">Department of
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<div style="word-wrap:break-word">Old Dominion
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