Prsentation PowerPoint

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TRACKING TEAM
Introduction What has been done What still
needs to be done
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Tracking Team
started at the Global Level Processing meeting
(15-16/05/2003 in Legnaro) Web site
http//www-csnsm.in2p3.fr/groupes/strucnuc/trackte
am.html
Members France Strasbourg, Orsay
Italy Legnaro, Padova, Milano
Poland Krakow Roumania Bucharest
Sweden Stockholm, Uppsala UK
York Team leader A. Lopez-Martens
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Aim of tracking

• Read for each event the list of deposited
  energies and positions of all the interactions
  points in AGATA
• e1, x1, y1,,z1
• e2, x2, y2,z2
• ..
• en, xn, yn,zn
• Disentangle the interaction points i.e
  reconstruct individual photon trajectories and
  write out photon energies, incident and
  scattering directions

Polarization measurement
E1, (?,?)inc,1,(?,?)sc,1 E2, (?,?)inc,2,(?,?)sc,2
Ei, (?,?)inc,i,(?,?)sc,i
Optimization ?ph x P/T
Doppler correction
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Physical Processes in Ge for photons
Compton
Photon range ?(E) MA/(Nav.?) . 1/??E
?(10 keV) 55 ?m ?(100 keV) 0.3 cm
?(200 keV) 1.1 cm
?(500 keV) 2.3 cm ?(1 MeV) 3.3 cm
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Property of Compton Scattering
source
1
3
e1
E?0
0
?1
e3
2
E?2
E?1
?2
e2
assuming that the e- is at rest, from
conservation of energy momentum
incident energy at i
cos(?i) 1 mec2 (1/E?i 1/E?(i-1))
scattered energy at i E?(i-1)-ei
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Some complications
!
Interaction position ? position of energy
deposition
?inc
?sc
?ion/?Brem Ee- (MeV) /21.8
e-
?
!
Electron momentum profile gt change in
scattering direction
!
Rayleigh scattering gt change in incident
direction
!
Interaction of neutrons or other particles gt
adds totally uncorrelated interaction points
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Additional Complications
From PSA uncertainty in position of interaction
x
x
x
x
position resolution
From preamp energy threshold
x
x
x
From preprocessing energy resolution
x
True interactions What comes out of PSA
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Events of interest total E absorption
Series of Compton scatters photoelectric
interaction (which might be so close that PSA
thinks its 1 single interaction point !)
Single photoelectric interaction
Pair production Compton interactions
Photoelectric interactions
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Existing Algorithms or Algorithms currently being
developed

• Clusterisation forward tracking
• G. Schmid et al., NIM A 430 (1999) 69
• D. Bazzacco, mgt code
• Lopez-Martens et al., NIM A 533 (2004) 454
• Back-tracking algorithm
• J. Van der Marel and B. Cederwall, NIMA 437
  (1999) 538
• L. Milechina and B. Cederwall, NIMA 508 (2003)
  394
• A. Lopez-Martens et al., NIM A 533 (2004) 454
• Clusterisation Probabilistic method
• I. Piqueras et al., NIMA 516 (2004) 122
• 1st hit identification with Fuzzy Logic and/or
  fuzzy cluster
• creation
• C. Rossi Alvarez
• D. Bucurescu (see corresponding talk)

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Whats been decided/done
Systematically use secondary particle tracking
for simulations (default option in the Agata
code) 5mm packing distance Tracked gammas in
the full 180/120/ configurations with all dead
materials, capsules, cryostats, and compared
their performance (http//agata.pd.infn.it/docume
nts/simulations/comparison.html) Compared
different algorithms with same simulated data (A.
Lopez-Martens et al., NIM A 533 (2004) 454)
Started combining the good features of different
algorithms Started tracking neutrons (see J.
Ljungvalls talk) Started checking background
suppression capacities of algorithms (see E.
Farneas talk)
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What needs to be done

• Pair production event tracking (anything new ?)
• Single interaction points (anything better than
  what we have now ?)
• Improve background suppression of algorithms
• Take into account ancillary information (?)
• Use  real  position uncertainties within a
  detector
• Compute  real  effective distances in Ge (not
  assuming a 4? Ge shell).now done ?
• Produce data (what format ?) for data analysis
• Optimize tracking codes for speed
• Online implementation

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Where is Waely ?