- 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.
