1. Tracking Pattern Recognition
GSI, December 2nd, 2010
Brief summary of
Tracking Pattern Recognition
status in Panda
Gianluigi Boca
Gianluigi Boca, GSI, 2 Dec 2010

2. The detectors for which we have presently a Pattern Recognition
code are the central detectors :
Mvd, Stt, Tpc, Gem and the Muon Drift Tubes (MDT)
Still missing is the Forward Tracker (Straws) because
software development began later than the other detectors
(in spring of this year).
Ideal Pattern Recognition : hits are associated to tracks according
to MC truth
Real Pattern Recognition : hits are associated to tracks as in real
life situation, with PR algorithm.
Gianluigi Boca, GSI, 2 Dec 2010

3. Ideal Pattern Recognition
There has been Ideal PR for all Central Detector since a long time
(at least more than one year ago).
Also existing :
1) Ideal PR for Mvd + Tpc, based on Rieman sphere
algorithm, and it works fine.
2) LHeTrack general purpose pattern recognition package
(works well in region where B field is actually constant )
Gianluigi Boca, GSI, 2 Dec 2010

4. Real Pattern Recognition
Two approaches in Panda :
‘homemade’ code : Panda developers wrote code based
on various Pattern Recognitions techniques.
usage of LHeTrack, a general purpose PR code written by
Russian scientist not active at GSI any more.
Gianluigi Boca, GSI, 2 Dec 2010

5. Real Pattern Recognition
Mvd alone
Homemade code : PR based on Riemann sphere; track vertex
doesn’t have to be in (0,0,0). Efficiency : see Tobias’s talk
at this meeting for efficiencies etc.
LHeTrack code : works well with Mvd detector alone;
track vertex has to be near (0,0,0).
Gianluigi Boca, GSI, 2 Dec 2010

6. Real Pattern Recognition
Stt alone
Homemade : PR based on 2 step process; use of a conformal
mapping, ‘road finding’ procedure, MILP software (GLPK
library) for fast minimization algorithm AND for solving the
straw left/right ambiguity.
Vertex must be within  5 mm from (0,0,0).
See Gianluigi’s talk at March 2010 collaboration meeting
LHeTrack code : doesn’t work well with Stt detector alone;
this is probably due to the fact that Stt hits are not XYZ hits.
Gianluigi Boca, GSI, 2 Dec 2010

7. Real Pattern Recognition
Tpc alone
Homemade : PR based on Rieman sphere ; vertex doesn’t have
to be in (0,0,0). Also a version exists with Hough trasform
method. See Felix’s talk at September 2009 meeting.
LHeTrack code : works well with Tpc detector alone;
track vertex has to be near (0,0,0).
Gianluigi Boca, GSI, 2 Dec 2010

8. Real Pattern Recognition
Gem alone
Homemade : match hits in indiviual stations; find pairs of hits in
adjacent stations ( track segments) from possible tracks
coming from vertex in (0,0,0) by using parabolic formula
( = fast to compute) ; merge track segments into a track;
removal of spurious hits; remove obviously wrong tracks.
See Radek’s talk at December 2009 meeting.
LHeTrack : it doesn’t works well with Gem detector alone;
this may be due to the non-uniformity of B field towards the
edge of the solenoid.
Gianluigi Boca, GSI, 2 Dec 2010

9. Real Pattern Recognition
Muon DT alone
Homemade : PR based on a proximity search starting from
inner hits outwards. See Stefano’s talk at
December 2009 meeting.
Pattern Recognition
MdtHit from inner layer
one tracklet PndMdtTrk
closest hit in next layer
in a search cone
and so on…
Enccap and Muon Filter
threated as single module
LHeTrack code :
it doesn’t
make sense to
use it in this case

10. Real Pattern Recognition
Mvd + Tpc
Homemade code : PR based on Riemann sphere Mvd code
extended to include Tpc hits; track vertex doesn’t have to be
in (0,0,0). Code becomes slow due to high combinatorics.
LHeTrack code : works well also with Mvd + Tpc ;
track vertex has to be near (0,0,0). This is the code practically
used at present.
Gianluigi Boca, GSI, 2 Dec 2010

11. Real Pattern Recognition
Mvd + Stt
Homemade : PR Stt alone; tracks extrapolated in Mdv region and
new hits associated; new fit (in 2 steps) ; use of a conformal
mapping; MILP software (GLPK library) for fast
minimization algorithm AND for solving the straw left/right
ambiguity. Vertex NOT constraind to originate from (0,0,0).
Much better rejection of spurious hits. Better resolution.
see Gianluigi’s talk at September 2010 meeting.
LHeTrack code : doesn’t work well with Mvd + Stt detector;
this is probably due to the fact that Stt hits are not XYZ hits.
Gianluigi Boca, GSI, 2 Dec 2010

12. Real Pattern Recognition
Mvd + Gem
Homemade : PR code ready (see Radek’s talk at this meeting).
Gianluigi Boca, GSI, 2 Dec 2010

13. Real Pattern Recognition
All central detectors
LHeTrack code : in principle it works with any set of
hits whose position is defined by X, Y, Z with small errors.
It works with the assumption of a constant B field  helix
trajectory.
No wonder it tends to fail in non-uniform B field regions
and for the Stt (hit X, Y, Z need to be calculated by prefit).
Gianluigi Boca, GSI, 2 Dec 2010

14. Real Pattern Recognition, work in progress
Mvd + Stt + Gem in overlap region
The overlap region between Stt and Gem goes from
10° <  < 20° in the ‘long’ Stt + 3 Gem geometry
and
14° <  < 21° in the ‘short’ Stt + 4 Gem geometry.
Lia is writing this code : starting from Mvd + Stt homemade
PR it projects tracks onto Gem sensitive planes (with Geane)
and looks for hits to associated to. With new ‘extended’ track
it redoes the track fit.
Gianluigi Boca, GSI, 2 Dec 2010

15. Status of Ideal Pattern Recognition & Track Fitting Software
Done for :
In progress
Mvd
alone
Stt
alone
Tpc
alone
Gem
alone
Forward
Straws
Mvd +
Tpc
Mvd + Tpc + Gem
Muon DT
alone
Mvd + Stt + Gem
Also : LHeTrack general purpose pattern recognition package
(works well in region where B field is actually constant )
For track fitting : Genfit (general Kalman package) ;
Stt alone Kalman code; Stt alone Helix fit
Gianluigi Boca, GSI, 2 Dec 2010

16. Status of Real Pattern Recognition & Track Fitting Software
Existing Pattern Recognition software for :
Detectors alone
Combined Detectors
Mvd
alone
Stt
Mvd + Tpc
with Riemann
(but slow)
Mvd + Tpc
with LHeTrack
Mvd + Gem
(see Radek’s talk)
Muon DT
alone
Mvd + Stt
Also : LHeTrack general purpose pattern recognition package;
works well in region where B field
is constant but not for Stt
Tpc
alone
Gem
Work in progress :
Stt + Gem in overlapping region of 
For track fitting : Genfit (general Kalman package) ; Stt alone Kalman code; Stt alone Helix fit
Gianluigi Boca, GSI, 2 Dec 2010