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Justin,<br>
<br>
In light of Simon's data results today, this is an updated version
of some suggestions I sent out last week to you and a few others.
<br>
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<br>
<div class="moz-cite-prefix"> 1. The slides need to be numbered
for easy reference.<br>
<br>
2. We need an intro slide from Justin overviewing the simulation
ingredients <br>
<br>
3. Cuts:<br>
<br>
i. Add a new fiducial cut P_proton > 300 GeV/c. <br>
(Anything below that is dubious based on Simon's Figure 37 in
the JEF proposal. This should remove some funny non-gaussian
outliers in the Phi and MM2 distributions for True events.)<br>
<br>
ii. Change the too-tight energy cut to +-0.36 GeV. <br>
(Let's aim for +-2sigma cuts - naively pretending they are
independent - until the kin fit is working.)<br>
<br>
iii. Tighten the MM2 cut from [-0.05,+0.025] to something
more consistent with a 2sigma cut (though possibly still
asymmetric). <br>
(Plot the MM2 on a scale that lets us judge how to set this
cut. Simon's data plots naively suggest the cut could be
tightened to a MUCH more restrictive +-0.005. But the average
beam energy in his data is lower than in the simulation, and
some of what I think is background might be Lorentzian tails on
the signal. So simulation should guide us here.)<br>
<br>
iv. Cuts for discussion: Do we need a fiducial cut on target
vertex to remove window backgrounds? Is M_2gamma reconstructed
using the inferred Z location of the event in the target, or
simply the target center? <br>
<br>
4. Plots <br>
<br>
i. Change the M_2gamma range to say 1.5 GeV. <br>
(We don't want to miss anything in the higher mass regions. And
we need this to get the whole story on the eta'/phi region.) <br>
<br>
ii. We can't easily see an extra pion on the MM2 plots. We
might consider zooming the range of MM2 [-0.3,+0.3]. <br>
(In units of the pion mass squared, that's already +-15 so
plenty.)<br>
<br>
iii. Since the fiducial cut on beam energy, plus the cut on
unused energy, had such a big effect, we can't see how the
remaining cuts reduce backgrounds in the "Yield plot after
various cuts". Can you make two versions, one on a linear scale,
and one on a log scale? <br>
(This would also be a good time to fix the spelling of
hyeildfalse and hyeildtrue.) <br>
<br>
<br>
Next steps:<br>
<br>
1. Get more quantitative: <br>
<br>
i. to fulfill Justin's initiative on an early physics
measurement: we need to estimate the reconstruction efficiency,
estimate counts per day per GeV wide beam energy bin, make sure
computer and electronic deadtime are reliably monitored, verify
tracking efficiency for recoil proton, what happens to this
analysis if a lower calorimeter threshold is used, etc? <br>
<br>
ii. to make sure we can prioritize our backgrounds: make a table
of the 5 largest backgrounds in the pi0, eta, and eta' regions,
listing the percentage for each. <br>
<br>
2. What do we have to fix to do kinematic fits? GlueX has
mediocre resolution and a high energy beam. This makes the
isolation of exclusive processes a somewhat ill-posed problem
without help. Bishnu's plots already suggest the omega
background in the eta mass region is resistant to cuts. With a
kinematic fit, we might be able to dramatically reduce that
background. <br>
<br>
Dave <br>
<br>
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