GSI, March 11th , 2014
Status of the
Road Finding
Pattern Recognition :
progress of the
Cleanup task
Gianluigi Boca
Pavia University
Gianluigi Boca, 11/3/2014
As it is well known, one basic problem in this type of pattern
recognition (and maybe also in some of the other Pattern Recogntions
investigated in Panda) is the presence of ghost tracks caused by the very
high interaction rate in Panda (event overlap).
found tracks
true tracks
NO CLEANUP
Gianluigi Boca, 11/3/2014
I have written a ‘Cleanup’ procedure since a very long time, which
eliminates tracks with missing hits along the trajectory.
However
this procedure has never been refined as it could be.
Consequently the present version overeliminates the tracks leading
to a loss in efficiency in the PR when the cleanup procedure must
be turned on in the presence of event mixing.
Gianluigi Boca, 11/3/2014
Performance of the present Cleanup code
Performance : Track Reconstruction Efficiency
% of the reconstructed tracks having AT LEAST 80% of the TRUE
Stt+Mvd hits.
MC generation : Box Generator;
multiplicities from 1 up to 8; momenta from 0.3 to 10 GeV/c.
No Bkg
Gianluigi Boca, 11/3/2014
Bkg added
I have written a ‘Cleanup’ procedure since a very long time, which
eliminates tracks with missing hits along the trajectory.
However
this procedure has never been refined as it could be.
Consequently the present version overeliminates the tracks leading
to a loss in efficiency in the PR when the cleanup procedure must
be turned on in the presence of event mixing.
Presently I am rewriting the procedure in a systematic way, trying to
exploit all the possibilities intrinsic to the STT, MVD and SciTil
subsistems.
The work is still in progress, today I’d like to report the method I am
following and the status of the work.
This procedure is contained in a class that can be used as a black box
in case other Pattern Recognition needed it.
Scheme of
the Cleanup Task
Gianluigi Boca, 11/3/2014
1
Use the XY positions of the hits to eliminate spurious tracks not
having all the hits they should;
2
Use the Z f positions of the skew hits to eliminate spurious
tracks not having all the hits they should.
Gianluigi Boca, 11/3/2014
STT layout, XY view
outer axial Stt
skew Stt
inner axial Stt
Gianluigi Boca, 11/3/2014
1
Use the XY positions of the hits to eliminate spurious tracks not
having all the hits they should
- subdivide track in arcs crossing a certain Stt axial straw sector;
outer axial
Arc of track
inner axial
Arc of track
1
Use the XY positions of the hits to eliminate spurious tracks not
having all the hits they should
- subdivide track in arcs crossing a certain Stt axial straw sector;
- require continuity of hits in each Stt sector;
exception to continuity rule : allow 1 axial Stt missing hit overall
due to expected 98 % straw efficiency;
continuity of
hits in track
continuity of
hits in track
1
Use the XY positions of the hits to eliminate spurious tracks not
having all the hits they should
- subdivide track in arcs crossing a certain Stt axial straw sector;
- require continuity of hits in each Stt sector;
exception to continuity rule : allow 1 axial Stt missing hit overall
due to expected 98 % straw efficiency;
- require that the track has the entrance/exit hits (boundary hits);
exception most external hit is not necessarily required to touch
the boundary (very forward tracks);
Gianluigi Boca, 11/3/2014
1
Use the XY positions of the hits to eliminate spurious tracks not
having all the hits they should
- subdivide track in arcs crossing a certain Stt axial straw sector;
- require continuity of hits in each Stt sector;
exception to continuity rule : allow 1 axial Stt missing hit overall
due to expected 98 % straw efficiency;
- require that the track has the entrance/exit
exit hit hits (boundary hits);
exception most external hit is not necessarily required to touch
the boundary (very forward tracks);
entrance hit
Gianluigi Boca, 11/3/2014
1
Use the XY positions of the hits to eliminate spurious tracks not
having all the hits they should
- subdivide track in arcs crossing a certain Stt axial straw sector;
- require continuity of hits in each Stt sector;
exception to continuity rule : allow 1 axial Stt missing hit overall
due to expected 98 % straw efficiency;
- require that the track has the entrance/exit hits (boundary hits);
exception most external hit is not necessarily required to touch
the boundary (very forward tracks);
- require hit in the SciTil system when track reached that;
Gianluigi Boca, 11/3/2014
1
Use the XY positions of the hits to eliminate spurious tracks not
having all the hits they should
SciTil hit
- subdivide track in arcs crossing a certain Stt axial straw sector;
- require continuity of hits in each Stt sector;
exception to continuity rule : allow 1 axial Stt missing hit overall
due to expected 98 % straw efficiency;
- require that the track has the entrance/exit hits (boundary hits);
exception most external hit is not necessarily required to touch
the boundary (very forward tracks);
- require hit in the SciTil system when track reached that;
Gianluigi Boca, 11/3/2014
1
Use the XY positions of the hits to eliminate spurious tracks not
having all the hits they should
- subdivide track in arcs crossing a certain Stt axial straw sector;
- require continuity of hits in each Stt sector;
exception to continuity rule : allow 1 axial Stt missing hit overall
due to expected 98 % straw efficiency;
- require that the track has the entrance/exit hits (boundary hits);
exception most external hit is not necessarily required to touch
the boundary (very forward tracks);
- require hit in the SciTil system when track reached that;
- require continuity of hits in the Mvd system;
Gianluigi Boca, 11/3/2014
1
Use the XY positions of the hits to eliminate spurious tracks not
having all thepixel
hits they should
strip
- subdivide track in arcs crossing a certain Stt axial straw sector;
- require continuity of hits in each Stt sector;
exception to continuity ruleMvd
: allow
hits1 axial Stt missing hit overall
due to expected 98 % straw efficiency;
- require that the track has the entrance/exit hits (boundary hits);
exception most external hit is not necessarily required to touch
the boundary (very forward tracks);
- require hit in the SciTil system when track reached that;
- require continuity of hits in the Mvd system;
Gianluigi Boca, 11/3/2014
2
Use the Z f positions of the skew hits to eliminate spurious
tracks not having all the hits they should.
- there is only one skew straw sector so require continuity of skew
hits (track Stt hits can have only one missing Stt hit overall
axial + skew );
Gianluigi Boca, 11/3/2014
2
Use the Z f positions of the skew hits to eliminate spurious
tracks not having all the hits they should.
continuity of
- there is only one skew straw sector so require continuity of skew
skew hits
hits (track Stt hits can have only one missing Stt hit overall
axial + skew );
skew straw regions
Gianluigi Boca, 11/3/2014
2
Use the Z f positions of the skew hits to eliminate spurious
tracks not having all the hits they should.
- there is only one skew straw sector so require continuity of skew
hits (track Stt hits can have only one missing Stt hit overall
axial + skew );
- first and last hit in skew sector must be at boundary;
exception : for very forward tracks last hit may not be at the
boundary if also there are not hits in the outer axial sector);
Gianluigi Boca, 11/3/2014
2
Use the Z f positions of the skew hits to eliminate spurious
tracks not having all the hits they should.
- there is only one skew straw sector so require continuity of skew
hits (track Stt hits can have only one missing Stt
hithit
overall
exit
entrance hit
axial + skew );
- first and last hit in skew sector must be at boundary;
exception : for very forward tracks last hit may not be at the
boundary if also there are not hits in the outer axial sector);
skew straw regions
Gianluigi Boca, 11/3/2014
2
Use the Z f positions of the skew hits to eliminate spurious
tracks not having all the hits they should.
- there is only one skew straw sector so require continuity of skew
hits (track Stt hits can have only one missing Stt hit overall
axial + skew );
- first and last hit in skew sector must be at boundary;
exception : for very forward tracks last hit may not be at the
boundary if also there are not hits in the outer axial sector);
- continuity of hits at the boundaries between axial and skew straws.
Gianluigi Boca, 11/3/2014
2
Use the Z f positions of the skew hits to eliminate spurious
tracks not having all the hits they should.
axial straw regions
- there is only one skew straw sector so require continuity of skew
hits (track Stt hits can have only one missing Stt
hit
overall
hit
continuity
hit continuity
axial + skew );
- first and last hit in skew sector must be at boundary;
exception : for very forward tracks last hit may not be at the
boundary if also there are not hits in the outer axial sector);
- continuity of hits at the boundaries between axial and skew straws.
skew straw regions
Gianluigi Boca, 11/3/2014
Status of completion
of the
Cleanup Task
Gianluigi Boca, 11/3/2014
1
Use the XY positions of the hits to eliminate spurious tracks not
having all the hits they should
- subdivide track in arcs crossing a certain Stt axial straw sector;
- require continuity of hits in each Stt sector;
exception to continuity rule : allow 1 axial Stt missing hit overall
due to expected 98 % straw efficiency;
- require that the track has the entrance/exit hits (boundary hits);
exception most external hit is not necessarily required to touch
the boundary (very forward tracks);
- require hit in the SciTil system when track reached that;
- require continuity of hits in the Mvd system;
Gianluigi Boca, 11/3/2014
2
Use the Z f positions of the skew hits to eliminate spurious
tracks not having all the hits they should.
- there is only one skew straw sector so require continuity of skew
hits (track Stt hits can have only one missing Stt hit overall
axial + skew );
- first and last hit in skew sector must be at boundary;
exception : for very forward tracks last hit may not be at the
boundary if also there are not hits in the outer axial sector);
- continuity of hits at the boundaries between axial and skew straws.
Gianluigi Boca, 11/3/2014
Future steps
FINISH
the Cleanup algorithm for the events
with background !!
Gianluigi Boca, 11/3/2014