Bug #1857
Another issue with Tracker recon and alignment
100%
Description
I have another issue with tracker recon/alignment stuff. This time I am concerned about space points and helical track fit.
Files
Updated by Rogers, Chris almost 7 years ago
- File x.png x.png added
- File test_tracker_fitting.tar.gz test_tracker_fitting.tar.gz added
- Category set to Tracker
- Assignee set to Hunt, Christopher
- Target version set to Future MAUS release
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.
Updated by Hunt, Christopher almost 7 years ago
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.
Updated by Rogers, Chris almost 7 years ago
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.
Updated by Rogers, Chris almost 7 years ago
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.
Updated by Rajaram, Durga almost 7 years ago
MAUS-v2.5.0, 7469 MC:
http://reco.mice.rl.ac.uk/MAUS-v2.5.0/MC/mc_3mm200_07469_MAUS-v250_1.root
Updated by Rogers, Chris almost 7 years ago
- 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...