Particle Flow in MARLIN
15/11/2005
P.Krstonosic - ECFA Vienna
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Prerequisites
• In order to discuss ( and compare ) PFA algorithms in any
software package some prerequisites should be fulfilled or kept
under strict control
• Clear definition what is Particle Flow
• Event generation
• Event simulation
• Digitization & Calibration
• Knowledge of software limitation and consistent output result
• If we manage to keep previous parameters under control
(nontrivial task by the way) it is possible to use available software in
MARLIN and come to the correct conclusions on the basis of it’s
output
15/11/2005
P.Krstonosic - ECFA Vienna
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Prerequisites
• Clear definition what is Particle Flow
Unfortunately already here confusion term shows as a most important
• Jet energy resolution :
 Ejet   PPU   JFU   DG   PFA
• PPU Pure Physical Uncertainties:
 PPU      E lumi   ISR   E
• JFU Jet finder Uncertainties:  JFU   JetFinderAlgorithm
• DG Detector Geometry Term:
 DG   toBeamTube   DeadZones
For PFA quality estimation one should first of all split of independent terms
or remove them from analysis.
Correct Particle-Flow analysis and comparison is possible ONLY after such
splitting
15/11/2005
P.Krstonosic - ECFA Vienna
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Prerequisites
• Event Generation
has closest relation to the
• PPU Pure Physical Uncertainties:
 PPU      E lumi   ISR   E
In order not to make life harder it is possible to generate events in the
way that reduces this uncertainty to the minimum for example
Z pole events without ISR, without beam energy spread and with only
light quarks in final state. Excellent events for P-flow studies but NOT
for any optimization since they are unrealistic or even unphysical.
• JFU Jet finder Uncertainties:
 JFU   JetFinderAlgorithm
On analysis of Z pole events there is no need for jet finder thus this term
does not contribute
15/11/2005
P.Krstonosic - ECFA Vienna
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Prerequisites
•Event simulation
Implicitly accounts the DG properly
• DG Detector Geometry Term:
 DG   toBeamTube   DeadZones
But can also introduce additional sources of spread in software
comparison studies due to the possible difference in :
RangeCut
PhysicsList
We should also not forget that program for simulation should store
proper input event information according to the LCIO MCParticle
definitions to allow full analysis - quantum leap in Mokka5.03
download now !
Digitization and Calibration issues that are now introduced could
also have significant effect if not properly implemented.
15/11/2005
P.Krstonosic - ECFA Vienna
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Prerequisites
And last but not the least
• Knowledge of software limitation
Although representatives of all software development teams will try to
convince you that software is plug&play this is ( may be ) true for the
installation but it does NOT refer to the physics analysis based on
the shipped software.
Now we are ready for the start
15/11/2005
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
If we start from a given event it is possible to proceed in to two branches
Using true information
1.
2.
3.
Analysis on the hep,
stdhep information
Smearing according
to the appropriate
particle history
PPF – perfect
particle flow
15/11/2005
Reconstruction
1.
2.
Event
P.Krstonosic - ECFA Vienna
Clustering + tracking
Wolf – PF
reconstruction and it
includes finding V0,
kinks and
assignment of
clusters to the V0
and the kinks
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Particle Flow in MARLIN
•One should select particles that have an ability to be measured in principle by
some of the sub-detectors.
• Then one calculates jet energy or di-jet mass for these carefully selected particles
or jets from HEP record directly – this will be the reference energy or mass for PFA
quality estimation
• On the other side of calculation full simulation should be used to get particle
splitting into account ( particle decays in the tracker region, possible gamma
conversion before calorimeter and possible bremsstrahlung gammas)
• At the end of such a procedure one should get the particles that reached a
calorimeter, and/or measured at the tracker.
• The next step would be to apply calorimeters energy resolution to the particles
that reached calorimeter. Make replacement for the charged particles with the
tracker resolution taking into account its decay, gamma conversion and
bremsstrahlung process.
• During the energy to momentum substitutions it should be taken into account the
shower overlap term in to the particle-flow resolution estimation. This information is
available as hit contribution that refers to the stable particle.
15/11/2005
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
N
Initial energy
distribution of
generated events , Z
pole , no ISR, no
beam spread , only
qqbar final state
Due to the current implementation of storing input information
15/11/2005
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
Energy distribution after
selection of possibly
measurable particles
with generator status 1.
N
This distribution
includes contribution
from removed initial
neutrinos
This stage should be
the starting point for
perfect reconstruction
15/11/2005
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
N
N
E2 distribution contains E1 plus additional spread due to the
additional neutrinos from decays in TPC, cut on the low Pt
particles and secondary particles that are lost .
This stage should be the starting point for smearing
procedures ( fast MC ) . In any case smearing will be
accurate up to the accuracy of selection of primaries.
15/11/2005
P.Krstonosic - ECFA Vienna
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Calculation according to the sub detector resolutions ( Ecal 11%,
Hcal 50%/sqrt(E)+4%)
e  e   Z 0  qq
Effect
To be
reviewed
Ev  0
Cone  5o
Pt  0.36
 HCAL
 ECAL
M neutral
M charged
at 91.2GeV
 [GeV]
 [GeV]
 [GeV]
separate
not joined
to total
0.84
0.84
total (% / E )
0.84 (8.80%)
0.73
1.11
1.11(11.65%)
9.28
1.36
1.76
1.76(18.40%)
32.20
1.40
1.40
2.25(23.53%)
34.12
0.57
1.51
2.32(24.27%)
5.66
0.53
1.60
2.38(24.90%)
4.89
0.30
1.63
2.40(25.10%)
1.57
%
12.28
Natural question arises how are the masses assigned ! And how large is the angular
error on the neutral objects
15/11/2005
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
Perfect Particle flow
Use of the track
cheater in the full
tracking system,
Cluster cheater
for calorimeters
and a MCParticle
tree not only for
track cluster
substitution but
also for full IP
propagation.
lost
track
15/11/2005
neutral
cluster
track
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
Results at Snowmass
Full realistic reconstruction
Looks like it is easy to make simple conclusion that there is
degradation of PF performance with increase of the B field .
15/11/2005
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
6T
4T
Perfect Particle flow after full simulation
Looks that there is no B field dependence
Who is right ??
15/11/2005
2T
4T
6T
sigma
1.59
1.58
1.61
fraction
0.74
0.73
0.67
P.Krstonosic - ECFA Vienna
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Measure of clustering performance?
1 algorithm
2 algorithm
1 true
70MeV
980MeV
2 true
750MeV
0
Quality = 1 ?!
Quality ~
 Ematch  980  750  0.96
 Ematrix 980  750  70
In order to take into account
second case normalization
was done for the full energy in
calorimeter and not to the
energy in the matrix
15/11/2005
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
In the Wolf processor there was hidden
DCA cut ( 3cm ) on the tracks
15/11/2005
Change in the double counted
energy coming from kinks
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
On the left reconstructed Z0 Mass
(tracking in TPC + TrackwiseClustering + Wolf)
On the right trackcheater in TPC only + clustercheater + Wolf
(no V0 and kink finding)
15/11/2005
P.Krstonosic - ECFA Vienna
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Particle Flow in MARLIN
On the left Track cheater in TPC only + clustercheater + Wolf
(no V0 and kink finding)
On the right Track cheater in the whole tracking system +
cluster cheater + basic kink and V0 finding
15/11/2005
P.Krstonosic - ECFA Vienna
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Conclusion
• There is no B field dependence on the performance of perfect
particle flow algorithm – any significant dependence just reveals
the caveats in the code
• Implemented reconstruction shows significant dependence
mainly due to the absence of dedicated V0 and kink finding
• Clustering performance is stable against B filed with minimal
dependence
• Processors for detail analysis will be released soon
• Information about available software and the new developments
you can find on http://www-flc.desy.de/ilcsoft
15/11/2005
P.Krstonosic - ECFA Vienna
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