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### Test TPC Off-line analysis

Marian Ivanov

TPC commissioning

- Test of TPC
- 2 TPC sectors
- not full TPC operational, no magnetic field
- Cosmic test
- 3 voltages settings
- 1 nominal voltage (statistic ~ 2000 triggered events (~10000 tracks))
- +- 50 volts (statistic ~ 300 events)
- Laser test
- Drift velocity determination, monitoring
- Alignment
- Stability test – important for ExB correction

Data flow

Raw data – Date format format

Rootification

Raw data – Root format forma

Reconstruction (Clusterization, tracking)

ESD – Tracks – default mode

Clusters and Signals (calibration mode)

Offline

Post processing Calibration

Data volume

- Raw data – One run (given sector ,voltage setting)
- 60 files x 1.5 GBy ~ 90 GBy
- Public access - Castor path /castor/cern.ch/user/m/miranov/testtpc2006/rawdata
- Rootified data
- 60 files x 0.65 GBy ~ 40 GBy
- Public access - Castor path /castor/cern.ch/user/m/miranov/testtpc2006/rootdata
- Reconstructed data
- 60 files x (AliESDs.root ~ 0.4 MBy + TPCtracks.root ~ 0.8 MBy + FitSignal.root ~ 100 MBy) ~ 6 GBy
- Public access - Castor path /castor/cern.ch/user/m/miranov/testtpc2006/rec0606
- Further reconstruction pass with new directory created

CPU requirements

- Raw data to Rootified data
- Downloading of the data to local storage
- 60 x 3 min ~ 3 hours
- Rootification
- 60 x 3 min ~ 3 hours
- Downloading and rootification done in bunches of files (Done in parallel)–Response time ~ 3 hours
- Reconstruction
- 60 x 40 min
- Done in parallel on LSF batch system
- Response time ~ 1-2 hour (waiting time in batch queue)
- Total response time given mainly by data transfer
- In optimal condition – Direct storage of rootified data on CASTOR + High priority in the batch queue ~ 1 hour

Offline Reconstruction (Cluster finder)

- Find clusters
- TPCRecPoints.root (Default mode)
- + In Mode without pedestal subtraction
- Estimation of pedestal event by event
- Pedestal and noise calibration (histograming and fitting of amplitude spectra)
- Signal fitting (optimization of parameters for tail cancellation)
- Reconstruction per file

Offline Reconstruction (Tracking)

- ESD
- AliESDs.root(Default mode)
- + In calibration mode
- Full TPC track stored
- Clusters belonging to track
- Extrapolation point at each pad row intersection (position, angle, estimated uncertainty, estimated shape parameters)
- Calibration: Parameterization of space point resolution and shape

Offline analysis

- Gain measurement
- Space point resolution, response function
- Signal fitting, processing
- Calibration

Offline analysis

- Input data
- Tracks and clusters – chain of Tree of tracks
- TPCtracks.root
- Pedestal & noise – chain of tree of fitted parameters histogram of amplitude spectra (mean –pedestal estimation, sigma – noise estimation)
- TPCsignal.root
- Signal shape – chain of tree with fitted signals (parameters of fit, graphs and position (sector, pad, row))
- FitSignal.root

Analysis

- .L TestAnalisys.C
- AddChains(runNumber);
- Loop over all files with given run number add trees to the chain
- Select();
- Make default selection
- Example:
- Track.fN>60 && abs(Track.fP4)<0.001
- Number of cluster per track bigger than 60, remove tracks with big curvature (most probably delta electrons)
- Do predefined plots
- See following slides
- Analysis done per run

Noise Analysis

- NoiseSector(“Sector==3”,”Run 872 sector 3 (V(A3_IROC) =1400 V)

Gain analysis

- Statistic not sufficient for pad by pad calibration
- 3 default plot
- Gain as function of pad-row
- Gain as function of pad position (phi angle)
- Gain as function of z position (electron capture)

Gain analysis (run872)

- ProfileMaxRow(“Cl.fDetector==49”, “Sector 49”,100)
- Arguments: cut, comment, binning

Gain analysis

- ProfileMaxPhi(“Cl.fDetector==49”, “Sector 49”,25)
- Arguments: cut, descriptor, binning

Gain - electron capture (run 567)

- The Q total (Total charge in the cluster) as function of Z position
- Relative decrease ~7 % (mainly due to electron capture + threshold effect) on full TPC drift (bigger statistic needed to be not influenced by Landau fluctuation

Response function

- PRFYZ(cut, “Run 872”)
- Arguments : selection, comment

Response function

- PRFZZ(cut, “Run 872”)
- Arguments : selection, comment

Space Resolution

- Left side Run 872
- Command ResYZ(cutinner, cutouter, comment)
- Right side Run 567

Signal processing

- Signal fitting added to analysis chain to tune parameters for tail cancelation
- Plans to include also Bernardo Mota algorithm to estimate tail cancellation parameters

Signal processing

- The signal fitting
- Fit function – convolution of Gaussian distribution with the sum of two exponential distributions
- Two exponential distributions approximate k/time distribution
- Possibility to reduce exponential components

Signal processing

- Lambda 0 parameter
- Command P3Z(“Sector==3”,”Sector==39”, comment)

Signal processing (Run872)

- Lambda 1 parameter
- Command P5Z(“Sector==3”,”Sector==39”, comment)

Conclusion

- Ongoing work on automatization of the analysis chain
- Currently ~ 4 hours for analysis chain (mainly due data transfer ~ 100 GBy per one run)
- Will be reduced
- The default histograms and pictures defined
- Next plan:
- Calibration
- Gain calibration
- Time offset calibration
- Alignement

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