ITS Offline

1. ITS Offline M. Masera ITS offline

2. ITS offline meeting 19/5/03 • Agenda: • 1) Communications (M. Masera) • 2) AliRoot status (P. Hristov) • 3) NewIO (P. Skowronski - to be confirmed) • 4) ITS geometry (B. Nilsen) • 5) SSD beam test in AliRoot (M. Masera for E. Fragiacomo - canceled) • 6) PID with the ITS (M. Masera for B. Batyunya) • 7) ITS standalone tracking at low Pt (E. Crescio) • 8) Offline ITS: personpower in 2003/04. Discussion. • 9) A.O.B. • The attendance was quite low: 7 people (2 from Cern core offline group) ITS offline

3. A meeting dedicated to reconstruction was held at GSI on May, 7-8-9. A copy of the slides presented can be found in: http://alice.web.cern.ch/Alice/ppr/web/GSI070503/GSI070503.html Resolution on track impact parameter (Dainese, Turrisi) An ALICE note has been written (on the referee’s desk now) Results for Pb-Pb: For p-p the resolution is 30% worse (50% at high pt) due to the poorer primary vertex resolution Dependence on the pixel layer thickness: decrease of 10% at 1 GeV/c when going from 400 (present design) to 600 m. GSI meeting / ITS related topics ITS offline

4. GSI meeting / ITS related topics • Primary vertex determination (Dainese, Masera, Riggi). A. Dainese reported on his work, which is for the time being finished. The classes for vertex finding have been released and an ALICE note has been submitted. • C. Kuhn reported on his results on hyperons reconstruction (see next three slides). ITS offline

5. Fiducial zone : 0.9 < R < 2.9 cm position angular momentum efficiency acceptance resolution resolution resolution (%) (%) (mm) (mrad) (%) 0 K 0.27 9.0 1.7 40 6 s L 1.4 30 4.5 0.35 3.5 X 0.32 8.5 2.3 5 0.4  6.7 1.5 4 0.2 0.25 Good tracks: TPC + 6 ITS layers ITS offline

6. acceptance efficiency produced Reconstructed produced / p S / B per event (%) (%) (%) per event o o 45 < q < 135 0 K 5 250 6 40 6 6 s L 2 100 4.5 30 1.3 6 X 15 0.3 0.4 5 0.003 ~ 6  2.5 0.05 0.2 4 0.0002 ~ 1 Fiducial zone : 0.9 < R < 2.9 cm Good tracks: TPC + 6 ITS layers  W 9000 events 0 80 000 events K s 20 events ITS offline

7. Fiducial zone : 0.9 < R < 6.9 cm Good tracks: TPC + 5 ITS layers acceptance efficiency produced Reconstructed produced / p S / B per event (%) (%) (%) per event o o 45 <  < 135 0 5 250 12 43 12 4 K s L 2 100 10 32 3.2 5 X 15 0.3 1.6 5 0.012 ~ 3  2.5 0.05 1.4 4 0.0014 ~ 0.5 0 Acceptance x 2 For K and L : s Acceptance x 4 , x 7 For  and W : ITS offline

8. GSI meeting / ITS related topics • Combined PID and tracking • there are some proposals for a global PID and ESD (aka DST) structures (from Y. Belikov, M. Ivanov and S. Radomski). The discussion will continue on the next offline week • For PID, each detector system should provide a conditional probability, i.e. • A combined PID can be achieved combining the various conditional prob. Via the Bayes theorem  we will have a Bayesian identification tool • A new ITS PID set of classes has just been released (B. Batyunya, S. Zaporojets). A first estimate of prob. Weights is given

9. PID in ITS • A new version of ITS PID classes (AliITSPid and AliITStracksPidV2) and their test macros have been just committed to the CVS repository • The particle identification (pions/kaons and protons) is carried out via dE/dx measurements by SDD and SSD in the 1/2 region (p<1.2 GeV/c) • The fiducial regions, the conditional probabilities and the contaminations have been determined starting from a sample of 480 HIJING events reconstructed with TPC+ITS V2 tracking ITS offline

10. AliGenBox: Equal number of different kinds of particles with flat pt distribution (Torino) HIJING (Dubna) ITS offline

11. dE/dx distributions (truncated mean: 2 out of 4) from different kind of particles. Generator: HIJING Distributions fitted with 2 or 3 gaussians ITS offline 300 < p < 380 MeV/c

12. Momentum interval: 0.384<p<0.416 GeV/c Protons kaons Pions Distributions fitted with a convolution integral of a Landau and a gaussian. 5 parameters. Generator: AliGenBox (Torino – very preliminary) ITS offline

13. Efficiencies and contaminations Low eff. due to fake tracks ITS offline

14. Efficiencies without fake tracks Next step: reduction of the misidentification induced by fake tracks + truncated mean = pion contamination ITS offline

15. Neural tracking in ITS / 1 • B=0.2 T • “Full” Hijing parametrized event (dN/dy=8000) • Efficiency: 5 layers / 6 • A. Pulvirenti gave an update at the GSI meeting on the status of his neural and combined (ITS+TPC) tracking method • Stand-alone ITS tracking has an efficiency of almost 79% for the highest multipilicity events for high transverse momentum tracks (Pt > 1 GeV/c) • “Combined” tracking increases by ~8-12% the tracking efficiency in the high transverse momentum range (Pt > 1 GeV / c), and gives an appreciable contribution for the Kaon reconstruction efficiency (+12-20%). Kalman only Kalman + neural ITS offline

16. Neural tracking in ITS / 2 Particles with transverse momentum > 1 GeV/c Summary table ITS offline

17. Another standalone ITS tracking • Presented by E. Crescio at GSI for the first time • Method inspired by the “grouping algorithm” described in:ALICE/ITS 99-34 “Tracking of the high Pt particles in ITS stand-alone detector”, P. Kindziuk, P. Lesczynski, A. Maliszewski, J. Mazur, J. Pluta, A. Roszczewski, H. Gutbrod • optimized for tracks with pT < 1 GeV/c • Use, as much as possible, of classes already implemented in Aliroot • Compatibility with V2 reconstruction ITS offline

18. Tracking efficiency (1) AliGenBox () B=0.4 T ITS only Trackable: one cluster for each layer of the ITS (6/6) ITS offline

19. Tracking efficiency (2) + ITSstand-alone V2 reconstruction + ITS stand-alone Trackable: one cluster for each layer of the ITS (6/6) ITS offline

20. Tracking efficiency (3) Trackable: one cluster for each layer of the ITS (6/6) ITS offline

21. Tracking efficiency (9) Hijing Param 4000 -8<<8 B=0.4 T ITS only Trackable: one cluster for each layer of the ITS (6/6) ITS offline

22. Tracking efficiency (10) Trackable: one cluster for each layer of the ITS (6/6) ITS offline

23. To do list A first display prototype exists! • Extensive debugging, especially at high pt • Optimization of the code (it is still very slow) • Internal note • A new class to display simulated and reconstructed tracks ITS offline

24. Status of AliRoot • P. Hristov and P. Skowronski presented the status of AliRoot and of the newIO • The newIO will become the default during the next offline week • The new IO has been already merged with the present aliroot version and tested with success up to tracking • ITS users are urged to test it  Action: M. Masera and R. Barbera ITS offline

25. New code for geometry (B.Nilsen) • SSD Cone is one class • Missing only holes to mount Ladder supports • Material definitions are the same as before • Would require changes to galice.cuts file. • Needs separate class structure • Needs proper material definitions • Needs testing for multiple copies of SSD Cone class • Need to write display code for ROOT display… ITS offline

26. New Geometry • Drawing for SSD thermal/support tube and SDD cone are available. • All of these drawings are presently being revised and are not yet put into EDMS as agreed. • For FMD and PMD: high priority must be put on SPD support structures and services. • Present AliITSvPPRasymmFMD geometry not a good substitute. • There will be no drawings of any services for quite some time. Therefore all the available information about these services are needed so that something can be mocked up. ITS offline

27. Present code structure • Each Geant geometry primitive has its own data class. All of these classes are derived from a common base class which is derived from TObject. • Copy numbers are accounted for automatically • Volume name are not limited to 3 characters (I+3 => 4 characters) • ITS objects, like the SSD cone, are a separate class, derived from a common base class. • This common base class contains useful interfaces to the existing Geant routine interfaces. • Geant volume names are created automatically and volumes are identified from longer volume names. • The ITS object classes use the new primitive geometry classes. • These more complicated object classes should behave in many of the same ways as the primitives (as far as copies, translations and rotations) ITS offline

28. Bjorn is considering expanding the primitive geometry data class to • Include most of the functions of the other class (e.g. SSD cone class). • Include knowledge of mother-daughter relationships • Add a materials class • Predefined “standard” element properties. • Easier to make mixtures and compounds. • Easily make mixtures of mixtures and compounds…. • Deal with the galice.cuts file in a better way. • What is available at present works. • Some of what has been requested will be more difficult to support in the present form. • Rene et al. are still developing the new geometrical modeler. We want to be compatible. • Is it worth the effort to continue on with these developments, or should the effort be put into coding up the geometry? ITS offline

29. Person power / 1 • LHCC asked F. Carminati to make an evaluation of the effort on the core offline • This evaluation has been internally extended to the whole offline • see the attached Excel spreadsheet with • Names and months/year in 2003/4 (their own evaluation) • tasks ITS offline

30. Person power / 2 • The effort on analysis and reconstruction tasks appears to be adequate • Personpower is barely sufficient on tasks like: • simulation of detector response • geometry coding • library maintenance • framework (uncovered) • alignment • Subdetector experts: • SPD: B.Batyunya, T.Virgili • SDD: P.Cerello • SSD: E. Fragiacomo ITS offline