Alignment open issues and tasks
This is an incomplete list of open issues in detector alignment. Please add whatever you think is missing. Or assign yourself to a task.
Stripping for alignment
We would like to have a set of dedicated dsts with tracks suitable for alignment. The best would be to create a selection for the stripping. We want to select
events with
- high momentum tracks, e.g. tracks above 20 GeV
- tracks through velo overlap regions. Use the VeloTrackSelector.
- velo halo tracks. Use the TrackSelector, or eventually VeloTrackSelector
- tracks through IT overlap regions. Use the ITTrackSelector.
- clean J/psis
- clean Ks
- unbiased selected muon tracks of high momentum (use muon-stand alone track reconstruction)
Some of these are already in the express stream. The Ks dst probably exist, but I don't know how clean it is.
To speed up the processing of these events, it would be useful to store the tracks in a separate Track container. I don't know if that is possible in the stripping.
Who: ?
Date entered: 2010-05-17
Tool to display differences between databases
We would like to have a tool to display the difference between alignment databases.
There is now a tool to create a database as the difference between two databases(DBDiff.py) and a tool to plot the contents of databases (plots.py).
Both live in /Alignment/Escher/scripts and are tagged with bursche_20100527 . See
PlotAlignmentDB for details and email me any problems. The code is new so there are probably bugs.
Who: Albert
Date entered: 2010-05-17
Field-on / field-off difference in T station alignment
The alignment constants extracted with field-on and field-off data are not compatible with each other and also not compatible with survey, in particular in the first T stations. Part of the problem is the alignment in 'z': movements in z of several mm are obtained with respect to the survey. These movements are not physical and have lead to a severe curvature bias, which was at some point wrongly attributed to the field. However, even if those z movements are fixed, the field-on and field-off alignment are not compatible. A futher complication here is the internal alignment of IT: the z-position and rotations of the layers inside an IT box are actually not that well constrained.
For a brief overview, see the first few slides of
this talk
.
To solve this issue several studies have been proposed, a.o.
* align the detector with very high momentum tracks (e.g. > 30
GeV).
* revive the RASNIK system to get a handle on the true momevents between field-on and field-off
Who: everybody
Date entered: 2010-05-17
Velo-TT to T matching
There are significant biases left in the matching of Velo-TT to T segments are seen by the
TrckFitMatchMonitor. See e.g. slide 4 of
this talk
.
This is probably just another symptom of the lack in understanding of field-on and field-off alignment.
TT scaling problem
Even after fixing the pitch there are still some remaining problems with scaling in TT. See recent talks by Christophe.
Who: Christophe, ...
Date entered: 2010-05-17
OT/IT alignment versus time
The OT and IT have been opened several times, in the wintershutdown but also at least once this spring. We need to know how stable the alignment is.
From Fred and Dirk:
intervention |
opened |
closed |
frames |
1 |
15:00h, 13 Jan 2010 |
17:00h, 11 Feb 2010 |
all C-frames |
2 |
09:00h, 8 Apr 2010 |
12:50h, 8 Apr 2010 |
T2L01Q02 (C-side T2 first C-frame) |
3 |
12:30h, 26 Apr 2010 |
13:00h, 28 Apr 2010 |
T2 and T3 on A-side, T2 C-side |
4 |
10:15h, 20 May 2010 |
14:30h, 20 May 2010 |
T2L01Q02 (C-side T2 first C-frame) |
Matt: In run numbers:
period |
begin data |
end data |
first run |
last run |
2010-1 |
March 30 |
April8 |
|
69845 |
2010-2 |
April 8 |
April 27 |
69845 |
70832 |
2010-3 |
April 27 |
May 20 |
70832 |
72060 |
2010-4 |
May 20 |
|
72060 |
|
Who:
Date entered: 2010-05-18
Ks mass studies, J/psi mass studies
Study invariant mass as function of kinematic, such as
- phi, Matt's phi: azimuthal asymmetries
- eta, momentum: material
- p(pi+) - p(pi-): q/p bias
These studies would greatly benefit from a dst with a clean selection.
Track-Calo alignment
There is a known displacements of a few (up to 7?) mm of the ECAL C-side with respect to the tracker. See e.g. slide 9 of
this talk
. Olivier Deschamps thinks that 7mm is not physical.
Who: ?
Date entered: 2010-05-17
Track-RICH alignment
The RICH group is doing a great job aligning the RICH, however, it is still unclear (to Wouter) how sensitive the RICH actually is to changes in the alignment of the tracker. Some plots illustrating that would be very useful. In the meantime, Sam and Chris are working on intergarting the RICH in the track fit
Who: ?
Date entered: 2010-06-02
Strange tail in residual distribution of hits in Velo overlap regions
See slide 16-19 of
this talk
.
Note that there is a real problem in simulation as well.
Who: David
Date entered: 2010-05-17
--
WouterHulsbergen - 17-May-2010