[SBS_sim] g17 results

[Ole Hansen]

Hi folks,

attached are my latest results for the g17 production. I replayed the 
first 5000 events of the 0% background run. The plots show the 
differences between the reconstructed and MC track parameters. There is 
also a 2d plot of the strange-looking y-difference vs. y-position, 
showing a clear see-saw structure, probably due to clusters that have 
only one active strip (to be investigated more).

I got rid of the offsets in x and y by hand. I showed the offsets at the 
last meeting.

The tracks are projected onto Evaristo's "Virtual Entrance Window" 
plane, so the reconstructed parameters should match the MC input directly.

Overall, the resolutions have improved slightly, which was expected.

Regarding tracking efficiency, the results are very similar to the g16 
replay with 0% background. However, there is a piece of bad news: I 
discovered a (really silly) error in the replay script which caused the 
final number (recomputed efficiency = tracks found/MC track in 
kinematics window) to be too high. After fixing this, I now find that 
indeed (like Evaristo already found) close to 99% of the MC tracks are 
in the central region. This results in a recomputed efficiency of 90.5%. 
See the attached text file.

Now I have a few questions for Evaristo regarding the readme.txt of the 
g17 production:

- "the first GEM 'real entrance window' is at: 0.80835 cm from VEW"
   Further down you list the "MC Geometry Details". Which of those
   detailed materials does t'he first GEM real entrance window'
   correspond to?

- "the first GEM readout plane is at: 2.05625 cm from VEW"
   But below you list the coordinates of all the planes, and it
   says
   Virtual entrance window z = 299.922 cm
   ..
   Chamber0 Coor_targ = 0 0 304.522 cm

   What is the meaning of "Chamber 0  Coor_targ"? I am confused since
   299.922 + 2.05625 = 301.97825, so this Coor_targ is ~2.5 cm behind the
   readout plane?

- In the MC Geometry Details, each element shows a size = 200 250 0.x cm
   but then it says "active volume size is 40 x 50 x ... cm3". What do
   the numbers 200 250 mean? why are they 5 times larger than the active
   volume size?

So much for now, talk to you at the meeting in 10 minutes,

Ole

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