The Pion Formfactor Experiment

HEEP and Phi Check Results---Suggestions for More HEEP calibration Runs

The following results are analyzed near Tue May 26 16:11:11 EDT 2003.

Abstract

In this page, we do some heepcheck summarization. All we do here is suppose that the HMS is perfect, the angle of SOS is perfect, so only Psos and Ebeam should have additional offset calibration.

We find that that the Pm-oop distribution is not centered at 0.0, so we also consider HMS and SOS phi offset.

In section(2) we replay several runs (45162, 45165, 45907) with these new offsets from our previous discussion and the phi offsets which we tried today putting into kinematic file and see the improvements.

In section (3) we compare the improvements in different ssdelta region (ssdelta=0.0 and ssdelta=13) at Psos=1.74 GeV.

In our performance, we set the old saturation correction for Psos on, so what we have here is an offset added to the original correction.

If the relative saturation correction for Psos is correct, we should see the same improvement in Psos=1.74 GeV. Now we see that this can be hopefully true if we can tune the offset of Ebeam properly.

In section (4), we will show you what additional runs of calibration are necessary.

For our data, it seems that sphi_offset=0.0018 and hphi_offset=-0.0029
is OK choice. This is added in July 11, 2003 by xucc for noting.

(1) Introduction

We have gained experience in heepcheck fitting on Psos=1.2 GeV/c and 1.74 GeV/c. Now we notice the phi offset for hms and sos is needed. So we make a summarization here with our best offset estimation so far.

The offset used in section 2 for E0, theta(e), Pe, theta(P), Pp are
1.0 0.0 -4.0 0.0 0.0 for 1.2 GeV/c
and 0.0 0.0 -4.0 0.0 0.0 for 1.74 GeV/c

(2) Results for heepcheck for different runs------Tables

Table.1 Heepcheck for Run 45162(Psos=1.2GeV/c,
Ebeam=2238 MeV, and sostheta=50.405

Name Before heepcheck After heepcheck

dW -0.81e-2 GeV/c2 0.18e-2 GeV/c2

Emiss -0.78e-2 GeV -0.99e-3 GeV

Pm_par -0.278e-2 GeV/c -0.465e-3 GeV/c

Pm_per -0.606e-2 GeV/c -0.101e-3 GeV/c

Pm_oop 0.511e-2 GeV/c -0.864e-5 GeV/c

Table.2 Heepcheck for Run 45165(Psos=1.2GeV/c,
Ebeam=2238 MeV, and sostheta=50.405

Name Before heepcheck After heepcheck

dW -0.9e-2 GeV/c2 0.19e-2 GeV/c2

Emiss -0.827e-2 GeV -0.106e-2 GeV

Pm_par -0.27e-2 GeV/c -0.51e-3 GeV/c

Pm_per -0.625e-2 GeV/c -0.22e-4 GeV/c

Pm_oop 0.52e-2 GeV/c -0.2375e-3 GeV/c

Table.3 Heepcheck for Run 45906(Psos=1.74GeV/c,
Ebeam=3044 MeV, and sostheta=39.715

Name Before heepcheck After heepcheck

dW -0.81e-2 GeV/c2 0.34e-2 GeV/c2

Emiss -0.6245e-2 GeV 0.73e-3 GeV

Pm_par -0.1183e-2 GeV/c 0.52e-3 GeV/c

Pm_per -0.5844e-2 GeV/c 0.59e-3 GeV/c

Pm_oop 0.7445e-2 GeV/c 0.13e-2 GeV/c

(3) Results for heepcheck for different runs------Figures

Fig.1 and Fig.2 are the Figures done after our new heepcheck correction for Psos=1.2 GeV.

Fig.1 W, Emissing distribution at Psos=1.2 GeV from run 45162. Done after our new heepcheck correction.

Fig.2 Pm,Pm_par, Pm_per, Pm_oop distribution at Psos=1.2 GeV from run 45162. Done after our new heepcheck correction.

Fig.3 and Fig.4 are the Figures done after our new heepcheck correction for Psos=1.74 GeV.

Fig.3 W, Emissing distribution at Psos=1.74 GeV from run 45906. Done after our new heepcheck correction.

Fig.4 Pm,Pm_par, Pm_per, Pm_oop distribution at Psos=1.74 GeV from run 45906. Done after our new heepcheck correction.

(4)Heepcheck Improvements at other ssdelta value?

In run 45912, we have another run of Psos=1.74 GeV. It corresponds to ssdelta=12, which is in an acceptable delta scope according to delta scan.
Table.4 Heepcheck for Run 45912(Psos=1.74GeV/c,
Ebeam=3044 MeV, and ssdelta=12.0

Name	Before heepcheck	After heepcheck
dW	-0.97e-2 GeV/c2	0.18e-2 GeV/c2
Emiss	-0.74e-2 GeV	0.5e-3 GeV
Pm_par	-0.18e-2 GeV/c	0.36e-3 GeV/c
Pm_per	-0.708e-2 GeV/c	0.29e-3 GeV/c
Pm_oop	0.807e-2 GeV/c	0.11e-2 GeV/c

(4) Conclusion

From what we have done in previous several sections, we can conclude that

(1) The Beam energy offset for different beam energy should be calibrate seperately. It changes from energy to energy. In 2238 MeV, it seems to be 0.1%, while in 3044 MeV, it seems to be 0.0 0r even negative offset.

(2) It seems that the assuption that the offset of theta is value small is OK. That the calibration in ssdelta=0.0 and sosdelta=12 are similar confirms our conclusion.

(3) So it seems that the offset is OK for low momentum, but when the momentum is as large as 1.74 GeV, saturation effect is important. And it seems that the original saturation correction in the code still need to be modified.

But unfortunately we only have two points. How can we fit a formula? Now I understand why Henk said "too bad we do not have heepcheck at Psos=1.4 and 1.6 GeV/c."

(4) The value Pm oop is supposed to be zero. But here we seem to have a 0.5e-2 GeV/c if we set the phi offset to be 0.0.
When I set sphicentral_offset = 0.0026 and hphicentral_offset = 0.0011, the Pm_oop reduced to reasonably small value.
(5) We have already had Psos=1.2 GeV/c point and Psos=1.74 GeV/c points. If we want to make our own curve of saturation correction for Psos, we need more heepcheck runs at 0.9 GeV/c, 1.4 GeV/c , 1.6 GeV/c, or even 1.76 GeV/c points.
And at each energy, we should have at least one run of Psos=1.2 GeV/c, so that it is easy for us to determine the energy offset in a reasonalbe Psos value.

This site is maintained by Xu Chuncheng