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SHUTTLE prototype for PHOS. B.Polichtchouk IHEP, Protvino ALICE Off-Line Week 4 Oct 2006. PHOS calibration strategy. At the end of each run an array of mean amplitudes in channels will be obtained and can be stored as root file1 on the file exchange server (FES)

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Shuttle prototype for phos
SHUTTLE prototype for PHOS

B.Polichtchouk

IHEP, Protvino

ALICE Off-Line Week

4 Oct 2006


Phos calibration strategy
PHOS calibration strategy

  • At the end of each run an array of mean amplitudes in channels will be obtained and can be stored as root file1 on the file exchange server (FES)

  • At the end of each run the special procedure (“DeadChannelsFinder”) will start finding channels with the average amplitude below the threshold. These channels are declared as dead. Dead channels map will be updated and stored as root file2 on the FES.

  • Then calibration procedures will start, using the combined information from file1 and file2


Phos calibration procedures
PHOS calibration procedures

Two procedures are foreseen:

  • Adjustment of mean amplitudes in channels

    Adjustment coefficient for i-th crystal C[i]=<A[i]>/A0,

    where A0 – mean amplitude in arbitrary chosen “reference” cell.

  • Minimizing the deviation of two-photon invariant mass from the pi0 mass


Aliphoscalibhistoproducer class
AliPHOSCalibHistoProducerclass

class AliPHOSCalibHistoProducer : public TObject {

public:

AliPHOSCalibHistoProducer(AliRawReader* rawReader);

void Run();

void UpdateHistoFile();

void SetUpdatingRate(Int_t rate) { fUpdatingRate = rate;}

protected:

TH1F* fMeanAmp[5][56][64]; // amplitudes in [module][column][row].

AliRawReader* fRawReader; // raw data reader.

TFile* fHistoFile;

Int_t fUpdatingRate;


Aliphoscalibhistoproducer functionality
AliPHOSCalibHistoproducer: functionality

  • Produces root file with calibration histograms on the online machine (GDC/LDC,HLT)

  • Input raw stream is provided by AliRawReader class

  • Updates histograms every Nth event

  • If histogram file already exists in the working directory, updates it

  • At the moment the only kind of histograms is “amplitudes per channel”


Aliphoscalibhistoproducer how to use
AliPHOSCalibHistoProducer:how to use

void run(const char* file="2006run2211.root")

{

AliRawReaderRoot* rf = new AliRawReaderRoot(file);

AliPHOSCalibHistoProducer hp(rf);

hp.Run();

}


Aliphosdeadchannelsfinder
AliPHOSDeadChannelsFinder

…to be implemented


Aliphospreprocessor class
AliPHOSPreprocessor class

  • Uses root files with calibration histograms and dead channels map produced by AliPHOSCalibHistoProducer and AliPHOSDeadChannelsFinder

  • Implements calibration algorithms

  • At the moment only one precalibration algorithm is implemented: adjustment of mean amplitudes in channels

    Adjustment coefficient for i-th crystal C[i]=<A[i]>/A0,

    where A0 – mean amplitude in arbitrary chosen “reference” cell.

  • More elaborated calibration algorithms can be added easily


Summary
Summary

  • Prototype of PHOS preprocessor and procedure for running on the online machine are implemented

  • More elaborate calibration algorithms can be readily added into the PHOS preprocessor


TODO

  • Using of dead channels map in the PHOS preprocessor

  • Special online procedure for pedestals calculation

  • “Pi0 mass” calibration algorithm in the PHOS preprocessor. If AliRoot is not allowed on the online machine, lightweight replacement of AliPHOSClusterizer have to be developed.


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