[Frost] tagger sag

[Michael Dugger]

Hi,

I know that the study Sungkyun performed was to help verify the eloss 
momentum corrections, and I think that this is a reasonable way to look at 
his study. However, this sort of study is also very useful in determining 
the tagger sag. Since the eloss correction is not as pronounced for the 
Carbon and CH2 targets, these targets can give us a good picture on the 
tagger sag situation.

If you look at the CLAS note:
http://www1.jlab.org/ul/Physics/Hall-B/clas/public/2009-030.pdf

Fig. 5 on page 6 shows the tagger sag correction to be on the order of 
0.5% for g1c data. For g8b data, the sag correction was between 0.2 to 
1.0% (Fig. 6 page 7). This means that we need to look for energy effects 
on the order of 0.1% to be sure that the tagger sag is not an issue.

For g8b it was found that the tagger sag correction was important in 
obtaining reasonable pulls for the FSU kinematic fitter (see table 1 on 
page 7).

One way to get a better look at the energy study is to use:
[E_calculated - E_measured]/E_measured
instead of
E_calculated/E_measured.

Since Mike Williams used this sort of parametrization for g1c (and I 
did the same for g8b), we can more easily compare results between the 
different run periods to see if the shape of the energy correction 
distributions look similar. The tagger sag has a "signature" three bump 
pattern that should be clearly visible once we get to the 0.1% level.

-Michael