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The Pion Formfactor Experiment

Phi Check Results---fpi2 heepcheck runs

The following results are analyzed near Thus Sep 5 16:11:11 EDT 2003.

Abstract

In this page, the hphi_central_offset of 1.55 mrad is suggested by considering all the heepcheck runs of fpi2 experiments. We also check this with data from previous experiments.

(1) Introduction

We do some heepcheck run summarization concerning hms phi_central offset because we find that that the Pm-oop distribution is not centered at 0.0 .

All we do here is suppose that the SOS phi_central offset is perfect, only HMS phi_central offset is to be determined.

When we say "SOS phi_central offset is perfect", what we really mean here is that in the past, we did measure with instruments the SOS phi_central offsetto be 2.6 mrad, and this is set as default value in sosflag.param file. I get this information from the talking with Henk Blok. For hms, people did not do the same thing probably because they believe that it should be perfect (So the offset was believed to be ZERO). But what we show here is that it still has 1.5 mrad offset. In section(2) we replay run 47048 with and without such hms phi_central offset and compare the two pmoop distributions.

In section(3), we list all the pmoop mean value after applying new hms phi_central offset for fpi2 data. In section(4) ,we list all the pmoop mean value after applying new hms phi_central offset for previuos experimental data. Section (5) is the discussion

(2) Pmoop Distribution Before and After hms phi_central offset

In online03 version of replay, it is supposed that

sphicentral_offset=0.0026 and
hphicentral_offset=0.00
With this offset, you can see the Pmoop distribution as follows.


Fig.1 Pmoop distribution from run 47048. Done before our hms phicentral_offset.

Seeing that the Pmoop has a central value of 4.3 MeV, we suppose

sphicentral_offset=0.0026 and
hphicentral_offset=0.00155
Now see ythe following figure again. Now we have -0.9 MeV of Pmoop for run 47048.


Fig.2 Pmoop distribution from run 47048. Done after our hms phicentral_offset.

(3) Results of Pmoop for different heepcheck runs of fpi2------Tables

Table.1 Pmoop with hphicentral_offset=1.55 mrad
for Run 47048-47051(Psos=1.5808GeV/c,
Ebeam=4210 MeV, and sostheta=51.00
Run number Pmoop
47048 -0.90+-0.3 MeV/c2
47049 -1.40+-0.23 MeV/c2
47050 -0.53+-0.24 MeV/c2
47051 -0.70+-0.31 MeV GeV/c
average of above -0.90

Table.2 Pmoop with hphicentral_offset=1.55 mrad
for Run 47354-47356(Psos=1.74GeV/c,
Ebeam=5247 MeV, and sostheta=50.01
Run number Pmoop
47354 -1.10+-0.63 MeV/c2
47355 +0.36+-0.66 MeV/c2
47356 -1.50+-0.75 MeV/c2
average of above -0.8 MeV/c2

Table.3 Pmoop with hphicentral_offset=1.55 mrad
for Run 47576-47581(Psos=1.4196GeV/c,
Ebeam=3779 MeV, and sostheta=54.00
Run number Pmoop
47576 -1.50+-0.31 MeV/c2
47577 +0.84+-0.32 MeV/c2
47578 -0.33+-0.29 MeV/c2
47579 +0.43+-0.28 MeV GeV/c
47580 +0.89+-0.31 MeV/c2
average of above +0.08 MeV/c2
47581 +2.40+-0.35 MeV GeV/c

Table.4 Pmoop with hphicentral_offset=1.55 mrad
for Run 47679-47685(Psos=1.74GeV/c,
Ebeam=4709 MeV, and sostheta=48.005
Run number Pmoop
47679 +0.71+-0.42 MeV/c2
47680 +0.60+-0.41 MeV/c2
47681 +0.62+-0.39 MeV/c2
47682 +0.327+-0.33 MeV GeV/c
47683 -0.07+-0.38 MeV/c2
47684 +0.74+-0.43 MeV GeV/c
47685 +0.14+-0.40 MeV GeV/c
average of above +0.50 MeV GeV/c

(4) Results of Pmoop for different heepcheck runs of previous experiments------Tables

Table.5 Pmoop with hphicentral_offset=1.55 mrad
for Run 45906 45907 45162 45165
Run number Pmoop
45906 +3.4+-0.07 MeV/c2
45907 +3.9+-0.24 MeV/c2
45162 +1.8+-0.08 MeV/c2
45165 +1.7+-0.04 MeV GeV/c
45014 -0.13+-0.05 MeV GeV/c

(5) Results and disscussions

It seems that

sphicentral_offset=0.0026 and
hphicentral_offset=0.00155
explains well all the data of fpi2 heepcheck runs.

But it is not as good for previous runs.

For run 45906 and 45907, it reduced Pmoop from 8 MeV to 3.5 MeV, and for run 45912 and 45915, it reduced Pmoop from 5 MeV to 1.7 MeV.

Run 45014 behaves rahter well.

For determining hms phi_central_offset purpose, I would like to believe in our fpi2 data. So I suppose hphicentral_offset=0.00155
in the future.

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