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Tracking Reconstruction
THIS PAGE IS OUT OF DATE! The current tracking home page is here
[documentation]
[public plots]
[meetings]
[OPR]
[tracking efficiency]
[task list]
[validations]
[open issues]
[open projects]
Tracking meetings take place regularly:
- each Wednesday, 10:00 am
- SLAC Group C conference room (Bldg 84 (CLA), B259)
- 1-510-665-5437, press 1, enter 123168#
- agenda posted in the
Tracking hypernews
To contribute send a mail to the
tracking coordinator (Jürgen Kroseberg), or post contributions
at the
Tracking hypernews.
Study of the tracking reconstruction efficiency (primarily Monte
Carlo and data matching) with application to physics analyses is
performed by the
tracking efficiency task force. The K-short efficiency
corrections can be found here for run
1-3 and run
4.
A link of issues that are currently followed up in the tracking
meetings can be found
here.
Below follows an incomplete list of 'open' development
projects. If you would like to contribute in these or any other
areas, please contact the tracking coordinator or show up at the
tracking meeting.
- Cleaning up the default track list
The default list of charged tracks still contains a
'significant' fraction of duplicate or ghost tracks, for
example due to loopers. The importance of improving the
quality of the track list is increasing, since the 'rest of
the event' becomes more important for physics analysis.
- Left-right ambiguity assignment in TrkDchRadHitAdder
Gerry Lynch has recently shown (posting)
that there is room for improvement in in the assignment of
left-right signs in the algorithm that propagates SVT tracks
through the DCH. One suggestion is to make the algorithm
follow different track 'branches' for the different lr sign
solutions. This project takes an estimated 4 months for a
student. It should lead to better track parameters for low
momentum tracks.
- DCH end-plate geometry
There is a dip-angle dependent mismatch in $z_0$ when
comparing SVT and DCH tracks. The effect cannot be removed
by global alignment and probably indicates a problem in the
DCH (end-plate) geometry. Several people have studied this
effect in the past, but a new person is needed to explore
the subject further and implement a solution. Since the
nature of the problem is not understood, it is hard to give
a time-scale. Solving this problem should lead to improved
SVT-DCH track matching and momentum resolution.
- Tracking algorithm improvements
- TrkPoca fails in some cases. Ideally this should
never happen. Further diagnostics and ultimate fix
is necessary.
- TrkPoca very sensitive to the initial values for
SvtHits in the phi view of wafer 1 in layers 4 and 5 (HN836).
- Helix fit in TrkFitter is not robust and returns
pathological fit sometimes. Ideally this should
never happen. Further diagnostics and ultimate
fix is necessary. Physics motivation - Ks.
- Bfield
Existing mass shifts could possibly be attributed to
inaccuracies in the magnetic field. There exists new
measurements of te B1 fringe field.
- Event T0 algorithm
Improvement of the algorithm and track selection for the
determination of the event time.
- SVT local alignment
There are a few possible biases remain in the local alignment.
First, elliptical distortion is not very well constrained, this could
be improved with large d0 cosmics. Second, small phi and tanDip angle
biases are suspected due to possible bias in the boost constraint
in the alignment. We would like to fit for boost at the same time
with wafer positions to validate the boost itself (both in x and z).
Third, we need to investigate constraining of global position of
the SVT in the alignment (in particular slow drift). Any other
development may reveal something else (e.g. wafer curvatures in
outer layers and in z direction).
- SVT-DCH global alignment
Perform more robust fit (minimize direction in addition to position
of svt- and dch-track mismatch), use cosmic and hadronic tracks in
alignment (there is no GA for cosmic runs at the moment). Allow tcl
parameters to be added to database GA values if local alignment is
changed.
- Time-to-distance calibration
The DCH time-to-distance
relation and the corresponding resolution function are very
stable over time and thus need not be calibrated
frequently. However, some question remain about the quality of
the existing calibration. In particular, the hit errors seem to
be underestimated by about 20%, leading to poor overall
track chisquares. This issue must be resolved if we want to
use chisquares for track selection.
- Boost bias
Babar calculates the beam energies from
information provided by PEP, applying some corrections that were
tuned quite a while ago. Promp calibration runs a boost
calibration based on two prong events. The calibrated boost does
not agree with the boostprovided by PEP. This must be understood
because it affects the SVT local alignment which uses the boost
as a constraint.
- Momentum resolution
There are some indications that the
momentum resolution in data is worse than in MC. An analysis
involving a few clean decays, such as Ks->pipi, D*->Dpi and
J/Psi->mumu could resolve this issue in a time schale of a few
months.
There is no well defined limit to the group of people working on
the tracking issues. There is also no well defined boundary between
SVT, DCH, and general tracking. The following is not a complete
list (and it does not reflect previous contributions):
- SVT T0 calibration: Gerry Lunch
- SVT global alignment and beam spot: Max Baak, Gerhard Raven
- SVT local alignment: Andrei Gritsan, Dave Brown, Doug
Roberts, Bram Lillard, Gena Kukartsev
- SVT hit resolution: Wouter Hulsbergen
- SVT software coordination: John Walsh
- Svt-to-DCH hit adding: Mike Kelsey, Eric Charles
- DCH t-to-d calibration: Ed Hill, Haleh Hadavand, David
MacFarlane, Soeren Prell, Gerhard Raven
- DCH software coordination: Mike Kelsey
- Tracking efficiency: Luca Cavoto + task force
- B Field calibration: Bill Dunwoodie
- Momentum 'calibration': Jon Coleman, Bill Dunwoodie
- Track reconstruction software: Dave Brown, Gerhard Raven
- Tracking evaluation: Gerry Lynch
- Tracking monitoring: Thomas Allmendinger, Jürgen Kroseberg
- Tracking coordination: Jürgen Kroseberg
Below are the links to the tracking task lists for the current and previous
years. For historical reasons, certain tasks are associated with SVT or
DCH subsystems and could be found in the corresponding entries in the
Technical Coordinator's Page (for example, SVT local alignment
and DCH time-to-distance calibration). Certain tracking validation
tasks do not have FTE assigned under "tracking reconstruction" and
should be referred to Physics tasks.
This list is out of date
- ee->mumu (S.Wagner, A.Gritsan)
- cosmics (S.Wagner, A.Gritsan)
- KS->pipi (M.Spitznagel)
- Jpsi->mumu (T.Hall)
- phi (T.Hadig)
- D0 (B.Lockman, D.Williams)
- deltaE (M.Baak, A.Gritsan)
Return to BABAR reconstruction software page, BABAR Computing Home Page, or BABAR
Home Page.
Maintained by Jürgen Kroseberg
Last modified: Dec 17 2004
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