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Feature #1946

Track matching with diffuser

Added by Rogers, Chris about 4 years ago. Updated over 3 years ago.

Status:
Rejected
Priority:
Normal
Assignee:
Category:
Global Reconstruction
Target version:
Start date:
10 November 2017
Due date:
% Done:

0%

Estimated time:
Workflow:
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Description

Turns out the track matching with diffuser yields a very different residual width as compared to track matching without diffuser... making position cut not really useful with diffuser. How do we handle the cuts in this case?


Files

2016-04_1.2_globals.tar.gz (16.7 MB) 2016-04_1.2_globals.tar.gz Rogers, Chris, 10 November 2017 10:22
8645_residual_tof1_x.png (15.4 KB) 8645_residual_tof1_x.png Rogers, Chris, 10 November 2017 10:22
8681_residual_tof1_x.png (14.5 KB) 8681_residual_tof1_x.png Rogers, Chris, 10 November 2017 10:22
event_display_1_energy.png (13.4 KB) event_display_1_energy.png Rogers, Chris, 10 November 2017 11:06
event_display_2_energy.png (13.4 KB) event_display_2_energy.png Rogers, Chris, 10 November 2017 11:06
event_display_3_energy.png (13 KB) event_display_3_energy.png Rogers, Chris, 10 November 2017 11:06
#1

Updated by Rogers, Chris about 4 years ago

Looking at data with the diffuser in, the width of the residual distribution at TOF1 looks pretty broad (100 mm RMS). Obviously the diffuser makes a huge amount of scattering. But this means that the track matching cut is far too tight.

Consider attached plots - I show the residuals distribution for
  • run 8681, which has no diffuser (3-140 beamline, 2016/04 1.2 cooling channel with 3 T in SSU).
  • run 8645, which has the full diffuser (10-140 beamline, 2016/04 1.2 cooling channel with 3 T in SSU).

To generate these plots, I opened the TOF1 position cut right up when running global recon.




The red histogram are events that I consider to be "good", i.e. TOF and TKU are consistent as muons, chi2 in TKU is good and there is only evidence of one particle in TKU and TOF0/1.

The difference in width of the residuals is pretty clear. By default track matching uses a cut at 60 mm, which rejects many "good" tracks when diffuser is in. In the first instance, I propose opening the track matching cut right up so that the algorithm can be used at all when diffuser is in the beamline. Then analysts can make a run-by-run decision on which tracks to accept in post-processing.

One could imagine, in the future, propagating the uncertainties. That is probably a bigger job (though many elements of the code are in place, it will require some reasonably substantive changes).

Thoughts? Comments?

#2

Updated by Rogers, Chris about 4 years ago

Attached a few "event displays" showing energy vs z for the extrapolated track; e.g.

Just checking I didn't do anything dumb like making energy go down instead of up through diffuser etc...

#3

Updated by Rogers, Chris over 3 years ago

  • Status changed from Open to Rejected

Won't fix for now; just note that track matching doesn't really make sense with diffuser closed

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