E852 experiment

Analysis of Eta Pi0 system with the decay Eta -> Pi+ Pi- Pi0

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Draft 4

Date: Thu, 16 Mar 2006, From: Neal

Hi all: I have two "physics" questions regarding the paper.

1.) I don't know if using the "average error matrix" is the right thing to do in the mass dependent fit. This I believe leads to a (perhaps) significant underestimate of the errors. This is due to the fact that the ambiguous solutions have a larger spread than the typical error bar on one of the solutions. In the eta pi- paper, we increased the error bars for the MDF to be large enough to encompass all of the ambiguous solutions. Shouldn't we do that here as well?

Response

We have no the final conclusion on this item. But my opinion is to use "average error matrix" in MDF. Such approach = average solutions + average error matrix is more consistent and logical. Beside that we calculate the systematic errors, which include the soluton larger spread .

2.) Now that we know the angular distribution of the background, shouldn't we constrain the background in the fit to this distribution instead of making it be isotropic? It would be useful to see the scatterplot of costheta vs. phi for the background region.

Response

See please our response on comments on draft3

http://lav01.sinp.msu.ru/~vlk/E852etapiz/Adams_trc_response.html

Here we show scatterplot of costheta vs. phi for the background region. We pay attention that our statistic in background region is very small. We can't to calculate robust angular distributions in 40 MeV mass bin. So we use 1.14-1.42 MeV of EtaPi0 mass for side bands near Eta sygnal. Our estimation of anisotropy in background region is 15% -25%.

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Date: Fri, 24 Mar 2006 From: Neal

Hi all: Here's some more questions I have after another reading: Are the phase variations in Fig. 3c and Fig 4c consistent with each other? One of these must be mislabelled since both are labeled P+-D+ but one shows increasing relative phase and one shows decreasing relative phase. Can we see these overlaid?

Response

Fig.3c and Fig.4c are doen as phase (P+ - D+).

Is the phase variation consistent with the eta pi- data? (Should it be? I think so...). Can we see the eta pizero and the eta pi minus phase variations with mass overlaid?

Response

We have no a table of EtaPi- results. So you can see only figures. Here are Fig.EtaPi- and Fig.EtaPi0 . The difference betwen minimum and maximum of relative phase is Delta=|1.4-0.2|=1.2 for EtaPi- and Delta=|-0.8-(-2.0)|=1.2 for EtaPi0.

I believe the points with error bars in fig. 4 should be identical to the points with error bars in Fig. 3. Are they? (It's not obvious that they are.) Neal

Response

Corrected

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