procedure

Procedure for Hee'p checking 02/10/06 (rev. 02/13/06)

The procedure outlined below was performed for the Heep runs at Ebeam = 4.021 GeV and electron angle of 50.0 deg.

The Beam energy including energy loss in the target was determined by printing out gpbeam in the Analyzer. The value was 4.02022 GeV.

The contributions from radiative corrections needed to be determined first. SIMC was run at the same setting with the SOS out-of-plane offset included. SIMC was run with and without radiative corrections, and the results are shown below.

With Radiative corrections

Without radiative corrections

The difference (with rad - without rad) for each plot are:
       W= 2.85883
       Em= 0.47538
       Pmpar= 0.79623
       Pmper= -0.88237
       Pmoop= 0.0963397
       eCorsi= -1.13889
       pCorsi= -0.42788
       phi= -0.00416332

I will skip over the part where the offsets were determined by the standard HallC code "heepcheck.f", and come back to this after the next set of plots. So, for now, just assume we have determined some offsets from the heep analysis. The offsets from the radiative corrections were put into the kumac that calculated W, Em, Pmpar, etc, and here are the results before the heep offsets were included and after they were included. This shows that the heep offsets appear reasonable and move the plots in the correct direction.

Before Hee'p offsets

After Hee'p offsets

The process of choosing the Hee'p offsets was rather subjective.

At first Eric Christy's automated program "autoheep.f" was used, and the offsets used as input for this program were corrected for the beam energy loss and radiative corrections (ie -7.33 MeV, -0.938 MeV, -6.91 MeV and 1.56 MeV from the LHS plot above). Of the possible results, the ones with zero change in beam energy were considered. Of the results left over, the solution with the smallest chisq and with small changes in the spectrometer angles was selected. Here is the complete output from the program. The set of offsets selected was
      dE=0.0
      dth_ss=1.0
      dp_ss=0.6
      dth_hs=1.0
      dp_hs=2.7
The plots using these optimized offsets are included below

I decided to try an alternative method for determining the optimized offsets. Assuming the beam energy and spectrometer angles were more accurate than the mometum, the momentum offsets for the electron and proton were changed until the corrected singles plots (Corsi) showed no offset. At this point, the offsets in the other plots were less than 2MeV, so, after this, only minor tweaking of the offsets was performed.

Using the matrix in the heepcheck.f program as a guide, I adjusted the beam energy, spectrometer angles and spectrometer momentum until all the plots were close to being centered on zero. Here are the offsets determined with this method:
      dE=0.0
      dth_ss=0.1
      dp_ss=2.0
      dth_hs=0.4
      dp_hs=2.15
The plots using these optimized offsets are shown below. The observed deviations from zero are smaller than those determined using autoheep. Therefore, this method will be used for the other settings.

Code used to generate this plot h.kumac and myheepcheck.f.

Note- Just for interest. Here is the same plot without the RC affects to show that I have the sign put in correctly for this affect. The plots in the panel below all shift by a few MeV in the direction of the tails compared to the previous panel.

See also a change to the procedure here (02/16/06).
Another change to the procedure was also made here (03/28/06).