Bug #1857
Another issue with Tracker recon and alignment
Added by Rogers, Chris over 7 years ago.
Updated over 7 years ago.
Description
I have another issue with tracker recon/alignment stuff. This time I am concerned about space points and helical track fit.
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I have another issue with tracker recon/alignment stuff. This time I am concerned about space points and helical track fit. Maybe this will go away when the other tracker recon bug goes away (straight tracks)...
I see the following residuals in x position when doing track fitting in the 7469 geometry, TKU:
| station |
scifi space point residual [mm] |
scifi track residual [mm] |
| 5 |
1.9 |
1.9 |
| 4 |
1.2 |
1.2 |
| 3 |
0.7 |
0.7 |
| 2 |
0.2 |
0.2 |
| 1 |
0.1 |
0.1 |
Note that I also see bias in momentum of order 1 MeV/c, even with perfect 4 T field. I use track_point.pos()/space_point.get_position() and compare with MC truth (virtual hit) at the station. I attach sample x residuals for Station 5 (note I have global track fit residual in there also).
Sample scripts, geometry used and lots more plots are in the attached tar ball.
spacepoint.get_position()
is in Tracker local coordinates. You want spacepoint.get_global_position().
Adan wrote all the spacepoint/PR code I'd check with him if there are any further problems.
There is a (soon to be) well documented momentum bias in the track reconstruction. Due to PatRec+MCS+Eloss+dE/dx calculations we basically need to do a correction after the reconstruction.
I've spoken to Victoria about this, so she is aware, and it will be documented in the SciFi Paper.
I'm trying to get a MICE note out that details where all the biases come from, but I'm struggling a little with time right now. It is on the list though.
spacepoint.get_global_position() has no known issues.
I checked using space_point.get_global_position(). I also found a bug in my script. Revised residuals are more or less similar...
| station |
scifi space point residual [mm] |
scifi track residual [mm] |
| 5 |
1.8 |
1.9 |
| 4 |
1.2 |
1.2 |
| 3 |
0.8 |
0.7 |
| 2 |
0.3 |
0.2 |
| 1 |
0.0 |
0.1 |
I checked against the "official" MC data set, http://reco.mice.rl.ac.uk/MAUS-v2.3.1/MC/mc_3mm200_07469_MAUS-v231_1.root, again using space_point.get_global_position() and track_point.pos() and get following mean residual:
| station |
mean scifi space point x residual [mm] |
scifi track residual [mm] |
| 5 |
0.005 |
0.025 |
| 4 |
0.007 |
-0.012 |
| 3 |
0.039 |
-0.566 |
| 2 |
0.016 |
-0.436 |
| 1 |
0.030 |
0.049 |
Nb: I only looked at first 2000 events or so and I didn't consider e.g. Victoria's cuts. Not as bad, but still significant.
Following merge from 1.5.0 to my global tracking branch...
| station |
scifi space point residual [mm] |
scifi track residual [mm] |
| 5 |
0.024 |
0.075 |
| 4 |
0.050 |
0.140 |
| 3 |
-0.025 |
-0.089 |
| 2 |
-0.069 |
-0.052 |
| 1 |
0.056 |
0.162 |
Looks good. I will close the issue if the "official" MC comes through and looks okay.
- Status changed from Open to Closed
- % Done changed from 0 to 100
From the 2.5.0 full MC:
| station |
scifi space point residual [mm] |
scifi track residual [mm] |
| 5 |
0.005 |
-0.007 |
| 4 |
0.007 |
-0.075 |
| 3 |
0.039 |
-0.028 |
| 2 |
-0.011 |
0.016 |
| 1 |
0.030 |
0.101 |
So looks like it is fixed - closing the issue...
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