The Pion Formfactor Experiment

Omega production on fpi2 run data. Proton Yiled.vs.Run_number. Done On Aug. 26, 2004

(1) Introduction

The Omega Peak .vs.Run_number is disscussed here using replayfpi2 of Aug.2004.

(2) Omega Peak position run by run

Fig.1a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar.
THis is for runs which have Q2=2.45, Phms=3.336, Ebeam=5.248,
thetahms=10.61, thetasos=29.43 and Psos=1.74.

Fig.2a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar.
THis is for runs which have Q2=2.45, Phms=3.336, Ebeam=4.210,
thetahms=10.54, thetasos=51.48 and Psos=0.771.

Fig.3a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar .
THis is for runs which have Q2=2.45, Phms=3.336, Ebeam=4.210,
thetahms=12.20, thetasos=51.48 and Psos=0.771.

Fig.4a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar.
THis is for runs which have Q2=2.45, Phms=3.336, Ebeam=5.248,
thetahms=13.61, thetasos=29.43 and Psos=1.74.

Fig.5a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar.
THis is for runs which have Q2=2.45, Phms=3.336, Ebeam=5.248,
thetahms=16.61, thetasos=29.43 and Psos=1.74.

Fig.6a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar.
THis is for runs which have Q2=1.6, Phms=3.412, Ebeam=5.248,
thetahms=11.35(or 10.54 or 13.49), thetasos=23.78 and Psos=1.74.

Fig.7a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar.
THis is for runs which have Q2=1.6, Phms=2.931, Ebeam=3.778,
thetahms=10.50, thetasos=43.10 and Psos=0.786.

Fig.8a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar.
THis is for runs which have Q2=1.6, Phms=2.931, Ebeam=3.778,
thetahms=12.54, thetasos=43.10 and Psos=0.786.

Fig.9a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar .
THis is for runs which have Q2=1.6, Phms=2.931, Ebeam=4.709,
thetahms=13.29, thetasos=25.735 and Psos=1.65.

Fig.10a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar .
THis is for runs which have Q2=1.6, Phms=2.931, Ebeam=4.709,
thetahms=16.29, thetasos=25.735 and Psos=1.65.

Fig.11a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar .
THis is for runs which have Q2=1.6, Phms=2.931, Ebeam=4.709,
thetahms=10.55, thetasos=25.73 and Psos=1.65.

Fig.12a Omega peak for different runs.
The errorbar are statistical error bar and fitting error bar .
THis is for runs which have Q2=2.5, Phms=2.845, Ebeam=4.709,
thetahms=15.68(or 20.32 or 25.15 or 30.07), thetasos=32.40 and Psos=1.74.

(3) Answer to Henk and Garth's questions.
All the Omega peak value are got by Gauss fitting just at the top of the peak.
The error bar includes fitting error and statistical value. And usually fitting error dominates the error bar.
In general, the peak position looks OK.
Garth wonder how the peak position is find? The following fig.13 shows you an example.

Fig.13 Omega peak position finding for run 47726 as an example. The red fitting is the fitting Henk wants and also the value used in the above figures.

Some spectrums for a few runs which looks a bit "strange" as follows:

Fig.14.1 Omega Mass spectrum for run 47740. Doulble peak shows there are another meson peak?

Fig.14.2 Omega Mass spectrum for run 47743. Doulble peak shows there are another meson peak too?

Fig.14.3 Omega Mass spectrum for run 47744. Doulble peak shows there are another meson peak too?

Fig.14.4 Omega Mass spectrum for run 47747. Doulble peak shows there are another meson peak too?

Fig.14.5 Omega Mass spectrum for run 47749. Doulble peak shows there are another meson peak too? Or even 3 peaks?

Fig.14.6 Omega Mass spectrum for run 47751. Seems no Omega peak at all. Cross section is too small?

Fig.14.7 Omega Mass spectrum for run 47753. Seems no Omega peak at all. Cross section is too small?

(4)Conclusion

IN general, the peak position is stable. But is usually about 1-2 MeV higher than real Omega peak postion in PDG booklet. (see Fig.15)

Fig.15 Omega peak for different kinematics.
The errorbar are statistical error bar and fitting error bar .
For eack kinematics set of runs, we choose the "Middle" run run_number to stand for it.
The solid line is for standard mass value of OMEGA from PDG booklet.

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