E852 experiment
Analysis of Eta Pi0
system with the decay Eta -> Pi+ Pi- Pi0
********************************************
Draft 5_3
Date:
11 Jul 2006
From: Gary Adams for TRC
Subject: TRC comments and response
Vladimir and Ludmila:
The trc discussed your analysis on Monday (draft 5.3s). We tried to
identify what we thought could be published with little additional work.
The recommendations below constitute our best estimate for reaching that
goal. Of course you should feel free to present alternative plans if you
disagree. We appreciate all of the work you have done so far.
1) We feel that it is not yet possible to determine what the conclusions of
the paper will be, but in the interest of reaching a conclusion soon, some
reduction in the scope of the paper is advised. Neal has agreed to help
with the writing job when you and the trc agree on the outline.
2) Further work on the t' dependence of the pwa is not recommended.
Suh-Urk's tests are not likely to affect the outcome for the large
unnatural parity waves.
3) We do not feel that the MDPWA method should be included in the paper. We
still have many questions about the method and answering those would
require more analysis. We are also concerned that this method is unstable
with respect to the pi1 width. Fixing the a2 parameters changes the pi1
width and we don't understand why.
4) We are confident that the PWA+MDF method can be published. Some more MDF
analysis needs to be done, but not much. Fixing the parameters of the a2 in
the MDF is the best way to finish the analysis and it is easy to motivate
in a publication. You have already done much of the required work. In her
last email Ludmila reported pi1 parameters of M=1273+-17 +47 -13 and
W=373+-55 +10 -150 using RMS values for the systematic errors. These need a
little more study, as outlined below.
5) The best values for the a2 parameters have not been used in the MDF.
Using the PDG mass is OK but the width needs to be broadened to account for
resolution. We don't have a good simulation to determine this but if we
start with the eta pi- result (118 MeV) then we can make a pretty good
estimate. We suggest fixing the a2 width at 120 MeV. To add this into the
study of sys errors you should include 110 MeV and 130 MeV. Your sys study
already uses 118 MeV so some of this has already been done.
Response: See Note 8
6) We still have some questions about the MDF analysis method. For example,
on page 4 of Note2 you report chisq/dof around 1.2 using the average of the
ambiguous solutions, but the fits to individual random selections of PWA
results (fig 5 page 9) give much larger chisq, with none as low as 1.2. Why
are these so different?
Response: See Note 8
7) As Ludmila has pointed out, the distribution of chisq values (page 9)
has a long tail on it and this affects how we report the sys errors. We
would like to see scatter plots of pi1 mass and pi1 width vs. chisq. Also,
we would like to know what these look like, and what fig 5 looks like, if
you reject fits that have large chisq (>2 sigma). These would correspond to
fits that match the resonance hypothesis well. We note that the mass and
width in Table 1 of the paper do not match the peak positions or averages
in fig 5 page9 of note 2. This means that the resonance parameters are
correlated with chisq so we need to document that. Lastly, we would also
like to see scatter plots of pi1 mass vs. pi1 width, with and without the
chisq cut.
Response: See Note 8
8) The scatter plots and histograms requested in item 7) suggest an
alternative way to determine the pi1 resonance parameters. The average
values, or the most probable values, could be taken from the frequency
histograms after a chisq cut. The random errors could be taken from the
widths of the distributions. This would avoid averaging the amps before the
MDF. The answers should be similar to your previous method but this method
would be easier to explain. We would like to see these results for comparison.
Response: See Note 8
9) It looks like the label on fig 2c in the draft is wrong. It should be
D-P, not P-D.
Response
Doen
Response