TRACKING TEAM

Introduction

What has been done

What still needs to be done

Tracking Team

started at the Global Level Processing meeting (15-16/05/2003 in Legnaro)Web site: http://www-csnsm.in2p3.fr/groupes/strucnuc/trackteam.htmlMembers:

France: Strasbourg, Orsay Italy: Legnaro, Padova, Milano Poland: Krakow Roumania: Bucharest Sweden: Stockholm, Uppsala UK: York

Team leader: A. Lopez-Martens

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

E1, ()inc,1,()sc,1

E2, ()inc,2,()sc,2

………………………………Ei, ()inc,i,()sc,i

Doppler correction

Polarization measurement

Optimization: ph x P/T

Physical Processes in Ge for photons

Compton

(10 keV) ~ 55 m (100 keV) ~ 0.3 cm (200 keV) ~ 1.1 cm(500 keV) ~ 2.3 cm (1 MeV) ~ 3.3 cm

Photon range(E) = MA/(Nav.) . 1/E

1

2

3source

1

2

e1

e2

e3

Property of Compton Scattering

E0

cos(i) = 1 – mec2 (1/Ei – 1/Ei-1))

incident energy at i

scattered energy at i = Ei-1)-ei

assuming that the e- is at rest, from conservation of energy & momentum:

E1E2

0

Electron momentum profile => change in scattering direction!

Some complications……

! Interaction position position of energy deposition

e-

scinc

!

Interaction of neutrons or other particles => adds totally uncorrelated interaction points

ion/Brem ~ Ee- (MeV) /21.8

!

Rayleigh scattering => change in incident direction

Additional Complications …

From PSA: uncertainty in position of interaction

xx

position resolution

From preamp:energy threshold

xx

xx

x

From preprocessing:energy resolution x True interactions

What comes out of PSA

Events of interest : total E absorption

Series of Compton scatters+ photoelectric interaction(which might be so close that PSA thinks it’s 1 single interaction point !)

Single photoelectric interaction

Pair production +Compton interactions +Photoelectric interactions

Existing Algorithmsor Algorithms currently being developed

- Clusterisation + forward trackingG. Schmid et al., NIM A 430 (1999) 69D. Bazzacco, mgt* codeA. Lopez-Martens et al., NIM A 533 (2004) 454

- Back-tracking algorithmJ. Van der Marel and B. Cederwall, NIMA 437 (1999) 538L. Milechina and B. Cederwall, NIMA 508 (2003) 394A. Lopez-Martens et al., NIM A 533 (2004) 454

- Clusterisation + Probabilistic methodI. Piqueras et al., NIMA 516 (2004) 122

A. 1st hit identification with Fuzzy Logic and/or fuzzy cluster creation C. Rossi AlvarezD. Bucurescu (see corresponding talk)

What’s 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/documents/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. Ljungvall’s talk)

Started checking background suppression capacities of algorithms (see E. Farnea’s talk)

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

What needs to be done

Where is Waely ?