[SBS_sim] g17 results

[Evaristo Cisbani]

Dear Ole,

I answer to your questions in the text below:

On Tue, 2011-03-08 at 10:48 -0500, Ole Hansen wrote:
> 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 entrance is HC0_G10a

> - "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?
> 

The geometry details are still confusing. Anyway:

The longitudinal (along z) size of the single GEM is 7.5835 cm (include
the electronics boards). The active area of the GEM is upstream (closer
to the target) and its thickness is 1.5835 cm (the rest is the
electronics, out of the GEM active area). Figure prod_g17_gem_detail.png
probably give you some guess.

The "Chamber x Coor Targ" is the distance of the Chamber center from the
target.

Therefore, the entrance of the first GEM chamber is at (HC0_G10a):

 304.522 - 7.5835/2. = 300.7303 cm

Which correspond to (rounded): 299.922 + 0.80835 = 300.7303 cm

The readout plane (RO_Strips) is at 0.78575+0.45625 = 1.24200 from the
GEM entrance, that is at 2.05035 from the VEW

which should be 2.05625 cm (the difference is the thickness of the
entrance window that I probably count twice in the readme.txt - I have
to redo the calculation carefully - in any case the difference is quite
small).


> - 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?
> 

Misprint cm is in fact mm and the size are halfsize (a la GEANT): 200 mm
is halfsize 40 cm and so on for 250


Evaristo

> So much for now, talk to you at the meeting in 10 minutes,
> 
> Ole
> 
> plain text document attachment (results_v3_g17-0.txt)
> analyzer [0] .L SBSsim/replay_xy_MC.C+
> Info in <TUnixSystem::ACLiC>: creating shared library /home/ole/TreeSearch-GEM/./SBSsim/replay_xy_MC_C.so
> analyzer [1] plot_xy()
> Production? g17-0
> Events with >= 1 matching tracks = 4477
> Events with == 1 matching track  = 4476
> >=1 track efficiency = 89.54%
> ==1 track efficiency = 89.52%
> Events with ==1 track in kinematics window = 4584
> Mis-reconstructed fraction = 2.35602%
> MC track in kine window = 4944 (98.88%)
> Recomputed ==1 track efficiency = 90.534
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-- 
 Evaristo Cisbani                      office : +39 06 4990 2847 
 Istituto Superiore di Sanita`         lab    : +39 06 4990 2347
 Department of Technology and Health   fax    : +39 06 4938 7075 
 and Istituto Nazionale di Fisica Nucleare Roma - gruppo Sanita`
 via Regina Elena 299 - 00161 Rome     web    : www.iss.infn.it/cisbani
 Italy
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