v4-16-Release: bug reports, committed fixes and proposed changes

P. Hristov14/05/2009

Weekly offline meeting

Committed modification

• #48026: New magnetic field map much slower than old one ?

– the existing field in v4-16-Release has some jumps of up to few 10s Gauss, which is fixed in the update (Ruben).

• Use Root v5-23-04 for the continuation of the productions and for the analysis of the data

– No changes are needed in AliRoot

– Contains fix in TGeo needed by ZDC

– Changes needed on CAF

– Will be used in the next tagged versions v4-16-Rev-11, v4-17-01

Proposed changes

• #50317 Correct AliGenPythia for B-jet studies

– Needed for the EMCAL production

– Jennifer to provide the final modifications (trunk and release).

• #50301 Please install new AliTPCPreprocessor in Release

– From rev. 32103

• #50274 Wrong orientation of TPC clusters (Simulation with Geant4)

– From rev. 32362

• #49055 Artifact in the Z vertex distribution reconstructed with T0

– From rev. 32319

• The new RAW format: patch exists

New reports

• #50416 TRD tracks not propagated to the outer wall of TPC

• #50391 Implementing the possibility to correct the tracking for non-zero transverse components of the B-field.

• #50386 AliESDInputHandler: crash when opening .zip archive on CAF

• #50343 simulation seg fault in AliMUONv1::UpdateInternalGeometry

• #50254 Additional info in ESD track for TRD PID [request]

• #50225 AliAODHandler doesn't work correctly with merged events

• #50174 Index out of bound in TPC digitization for ppbench

(Black = v4-16-Release, Blue=trunk)

Active investigations: #47881 Position of outer track parameter not symmetric and not “outer”

1. The AliTPCtrack::PropagateTo function was modified.In case of step outside of TPC volume the track is not propagated.(The material description is not correct)

2. For unknown reason the TRD updates the Outer parameters even being outside of the acceptance. The code responsible was not localized.

3. Running the same reconstruction code without and with outer detectors the efficiency to refit decrease from 100 % to 98 %. The effect is visible mainly for big theta.

The TPC outer parameters have to be backuped in the AliESDfriend and incase of big difference (>n sigma) between TPC backup and current AliESDtrack parameters have to be replaced.

Active investigations: #49294: High-pt fake tracks are produced in 0 < phi < 30

0. I agree with Youri that we should apply proposed cut (on the relative precision of 1/PT). On top we have to minimize tails in pt pulls. The tail will define our cut.

1. The width of the pt pulls for tracks not decaying in the TPC is around(1,1.1) (TPC stand alone)

2. In case the particle decays inside of the TPC significant the tails of the distribution are more significant and the width is two times bigger.

3. The deteoration also visible in case particle decays inside of the TRD and the TRD info is used for refit.

To be done:

1. Backup TPC outer information in ESD friend track and start TPC refit from this point if the mismatch between current param and backup is bigger than n-sigma threshold.

2. 2. Check all high pt tracks for kink point which can cause the tails in 1/pt residuals.

Active investigations: #44264: Shift in the reconstructed PT

Observed pt shift and strong dependence of this shift on the theta is explained by not taking the Br and Brfi component of the mag field into account in AliExternalTrackParam::PropagateTo. It is not detector related.

The correction for p_t can be roughly estimated deltapt/pt ~ pz/pr * Br/Bz The fact that the effect is not detector specific can be demonstrated using the exact MC track references instead of the detector clusters in the reconstruction.(The code AliMCTrackingTestTask::FitTrackRefs+see attached picture.)

Conclusion:

1. ALL components of mag field should be taken into account in the propagatemethod.

2. Effect is proportional to the Br/Bz which is on the level of 0-2%

3. The effect of the vxB effect to the angular and position shift can not beneglected

4. Somebody should impliment as soon as possible correct PropagateTo method -not approximation - as all parameters are affected.

Active investigations: #46277: TPC z shift

The theta dependent z shift for track extrapolated to the TRD is observed also from the fit of MC data in case the Br and Brfi field is neglected during track propagation. The effect is also pt dependent, basically the track is deflected by a fraction a curvature in y direction.

Using tracks from your production /lustre/alice/local/TRDdata/SIM/P-Flat/TRUNK I got the slope about -0.4 mm/tan(theta) for tracks bellow 1 GeV.For tracks over 2 GeV the slope ( from MC fitting) was negligible.

I do not say that this is full explanation, but currently the first task is to implement correct Propagate method.

Active investigations: #46277: TPC z shift

I added new data memebers to the AliESDfriend track AliExternalTrackParam * fTPCOut; // tpc outer parameters AliExternalTrackParam * fITSOut; // its outer parameters AliExternalTrackParam * fTRDIn; // trd inner parameters

There are 2 reasons why I want to add them.

1. I can discard the information from outer detectors in case there is big chi2 mismatch between fTPCout and current ESDtrack parameters. (because of kink decays, big -non consistent material budget correction, and also bugs)

2. We can do QA - matching of the track parameters from different detectors.

Active investigations

• #48080 Dip at zero in the distribution of residuals (phi-angle, impact parameter in the transverse plane): PbPb events

– Investigated by Martin, Andrea,Yuri and Francesco

– Reproduced with pp events when vertexer Z is used instead of vertexer 3D.

– Doesn’t depend on the XY position of the vertex: forcing X=0, Y=0 in vertexer 3D doesn’t reproduce the problem.

– Using (0,0,0) as vertex doesn’t reproduce the dip (possibly because of the smearing).

– Switching off AliITStrackV2::Improve method (return at the first line) “cures” the dip with vertexer Z. Confirmed.

– Still a lot of work needed…

High priority (my selection)

• #49416 ClusterFinder - too many deconvoluted clusters

• #48981 Problem in "on the flight" V0 finder

Old slides

Previous reports

• #49538 PbPb bench crash:F-TGeoPcon::ComputeBBox: Wrong section order

– AliSHILv3 has to be fixed

• #49069 EventSpecies and QA...

– The event specie is not set in AliReconstruction. Laurent proposed a fix.

• #48898 Different track indices in the ESD kink loop and the ESD track loop

– “Marian knows how to fix the problem”. Second reminder is sent.

• #48748 Number of foundable clusters in TPC needs refinement

– No news

• #48360 Every MC production job writes an object back to OCDB. Temporary modification in sim.C/rec.C

Previous reports II

• #47113 Wrong TPC cluster bitmap stored in ESD. Still not OK

– Wrong bit map for the TPC clusters assigned to a track: eta dependency. No news

– No effect in HBT analysis (Adam).

#44511: Eta dependency of PID efficiency dE/dx not OK

#46796: Multiply reconstructed tracks (phi = 0 and 180 deg) ~1% fake tracks. This is consistent with the particle decays when some clusters

from the daughter track are assigned to the mother one or vice versa.

More investigations?

Work in progress (?)

#46278: Bug/artifact in SPD tracklet finding

Caused by the selection on DeltaPhi in the ITS vertexer 3D. PB to decide.

#46372: Primary vertex reconstruction: events with multiple primary vertices

Preliminary results shown

The updates in the ESD available in the trunk

Proposal: introduce it when we start pileup production with v4-16-Release

Work in progress (?)

#47452: TPC drift velocity correction

(was TPC-TOF matching in LHC08d raw-data reconstruction)

Affects not only TOF matching but also all the other barrel detectors

Laser and ITS/TPC matching algorithms will give the absolute Vdrift (under development)

Low number of laser tracks prevents (~30 instead of ~300/event) is an obstacle for the calibration

#45031: LHC machine parameters to go into GRP

Presented at the physics board. My understanding of the decision: take all the information.

Proposal: implementation upon the PB's decision, not urgent for current MC production

Other reports

• #47413 Correct treatment (in both cluster- and track finders) of the SSD modules that are dead on one side

– New development, not assigned.

• #47412 The tracking and PID efficiency for secondary anti-protons is higher than for secondary protons: artifact in the definition of “findable” track, still under investigation

• #47411 Implementing a "PID consistency check" with efficiency constant over momentum. No news.

• #47410 Improvements in the stand-alone ITS tracker: taking into account the energy losses, possibility to start from the outer. No news