Status of the problems reported in Savannah

1. Status of the problems reported in Savannah 29/01/2009 P.Hristov

2. Bug #44264, Shift in the reconstructed Pt • Tests with v4-16-Rev-01 • A systematic shift ~0.2% observed in the resolution plot • Investigated by Marian, Andrea, Jacek • Dependence on Br and Bphi investigated: not confirmed • Material correction: reducing the step from 5cm to 1 cm, the shift was reduced • Still under discussion: correct strategy for material correction.

3. Bug #44266, Introduce the Bethe-Bloch function in AliMathBase • Use a single instance of the Bethe-Bloch function • Discussion on the common parameterization for gas and solid state detectors: it exists and has to be used • Discussion on the conceptual difference between Bethe-Bloch formula used in PID and for energy loss correction: still opened

4. Bethe-Bloch cont. (Yuri) • The common BB formula parameterization has already been committed. We have, in fact, two formulas: • a function of the material properties (Z, A, rho, etc). This function returns the result in GeV, and used for the material corrections in the tracking. The formula is valid both for gases and solid material (these are only the parameters that differ) • a function of empirical coefficients. The coefficients come out of fitting the experimentally measured dependence of dE/dx on momentum. This function returns the result in MIP. It is used for the PID. • These two functions should be OK for everything. • Now, the detectors should start using it. I sent the corresponding patch to ITS and TPC. ITS already committed it. TPC committed only ~50% of my patch. I asked Marian if he saw any problem with the remaining 50%. Marian answered "No problem. But I want to commit it together with some other changes." So, I'm waiting. • In fact, the BB formulas belong now to AliExternalTrackParam (static functions). This is to avoid the circular dependence ESD <-> STEER, reported by Matthias during the Christmas.

5. Bug #44492, increase in double found tracks • Reported during PWG1 and PB • Investigated by Marian • Most of the doubly found tracks are identified as kink daughters (should be excluded from the analysis) • The rest is under investigation

6. Bug #44493, Shift in the reconstructed radial coordinate of the gamma conversion points • Observed with v4-16-Rev-01 • Reported on PWG1 by Dmitri and on PWG4 by Ana • Antonin has shown that K0s and Lambda do not have this problem. The reconstructed radial coordinate for these particles is not shifted, however the topology is quite different. • The problem is still opened.

7. Bug #44495, check the rel. raise of dE/dx • A comparison between MC and the cosmic data was done by Alexander • Data: Fermi_plateau/MIP = 1.55 +/- 0.01 • MC:Fermi_plateau/MIP = 1.589 • The relative precision of dE/dx is ~5%, the simulation has to agree with the data at a level ~1% • The observed difference is attributed to the lower gain (data), and to the preliminary analysis/calibration • The item can be closed (?)

8. dE/dx cont. (Yuri) • The recommendation of the Physics Board was to demonstrate with the Monte Carlo data, if this effect is because of the lower gain. Marian and Alexander reported about this at the PWG1 meeting. The item in Savannah stays open.

9. Bug #44511, Eta dependency of PID efficiency • The proton PID efficiency shows a marked eta dependency with a peak at eta=0 • Under investigation

10. Bug #44955, FMD need hits for background estimation from MC • Initial idea: to propagate the MC labels to the ESD information instead of using hits • The full chain hits/sdigits/digits to be modified to insure the propagation of the MC labels • Current solution: the background estimation is done using TrackRefs

11. Bug #44956, T0 needs hits to estimate background • Initial idea: the same as in case of FMD • Still opened

12. Bug #45256, MUON digits to include track labels • As part of the framework, the MC labels in the simulated digits are required • Still opened

13. Bug #45419, Checking if the gains stored in OCDB are used in both simulation and reconstruction (PID) • Marian will check it for the TPC simulation. • Alexander will check it for the TPC stand-alone PID. • Massimo will assign somebody to do the same in ITS. • Discussed as item at the detector review. • Still opened

14. Bug #45751, Low V0 efficiency at low momentum and large radii • Caused by a check on the propagation status in the V0 finder • Ongoing work (Yuri): the propagation methods should not change the track parameters if the propagation fails. The following functions will be modified: • AliExternalTrackParam::CorrectForMaterial(...) • AliExternalTrackParam::CorrectForMeanMaterial(...) • AliExternalTrackParam::Propagate(Double_t alpha, Double_t x, Double_t bz) • The detectors propagation functions to be checked • Only then the check on the propagation status can be omitted in very special cases

15. Low V0 efficiency cont. (Yuri) • I would add: even if/when the framework functions do not change the params when they fail, this still has to be done for the detector specific functions. Because they are, often, implemented as a sequence of calls of the framework functions. • The exceptions must be _very_ rare

16. Bug #45933, High memory consumption in the TPC reconstruction of PbPb events

17. Bug #46200: The track length/time calculation in ITS has to be checked • The track length/time is modified in the propagation functions. • A simple replacement of Propagate by PropagateTo affected the track length/time and the TOF PID was completely wrong. • The usage of propagation functions to be carefully verified (Andrea) • Still opened

18. Bug #46277, TPC z shift • The introduction of Gamma4 function in the TPC response caused systematic shift between ITS and TPC that was corrected modifying the parameters of IROC. The same problem is not yet fixed in OROC and causes ~0.4 mm shift between TPC and TRD

19. Bug #46278: Bug/artifact in SPD tracklet finding • Two features are observed: • A depletion of tracks around +- 0.01 • The dip at 0 is removed or smaller

20. To Do: • Jan Fiete checks the hits to exclude problems at the generation level • Andrei checks the geometry for the energy loss correction • Matevz prepares a scan with single particles (fixed Pt and eta)