class AliDielectronSignalFunc: public AliDielectronSignalExt

Dielectron SignalFunc




  Class used for extracting the signal from an invariant mass spectrum.
  It implements the AliDielectronSignalBase and -Ext classes and it uses user provided
  functions to fit the spectrum with a combined signa+background fit.
  Used invariant mass spectra are provided via an array of histograms. There are serveral method
  to estimate the background and to extract the raw yield from the background subtracted spectra.

  Example usage:

  AliDielectronSignalFunc *sig = new AliDielectronSignalFunc();


  1) invariant mass input spectra

  1.1) Assuming a AliDielectronCF container as data format (check class for more details)
  AliDielectronCFdraw *cf = new AliDielectronCFdraw("path/to/the/output/file.root");
  TObjArray *arrHists = cf->CollectMinvProj(cf->FindStep("Config"));

  1.2) Assuming a AliDielectronHF grid as data format (check class for more details)
  AliDielectronHFhelper *hf = new AliDielectronHFhelper("path/to/the/output/file.root", "ConfigName");
  TObjArray *arrHists = hf->CollectHistos(AliDielectronVarManager::kM);

  1.3) Assuming a single histograms
  TObjArray *histoArray = new TObjArray();
  arrHists->Add(signalPP);            // add the spectrum histograms to the array
  arrHists->Add(signalPM);            // the order is important !!!
  arrHists->Add(signalMM);


  2) background estimation

  2.1) set the method for the background estimation (methods can be found in AliDielectronSignalBase)
  sig->SetMethod(AliDielectronSignalBase::kFitted);
  2.2) rebin the spectras if needed
  //  sig->SetRebin(2);
  2.3) add any background function you like
  TF1 *fB = new TF1("fitBgrd","pol3",minFit,maxFit);


  3) configure the signal extraction

  3.1) chose one of the signal functions (MCshape, CrystalBall, Gauss)
  TF1 *fS = new TF1("fitSign",AliDielectronSignalFunc::PeakFunCB,minFit,maxFit,5); // has 5 parameters
  //  TF1 *fS = new TF1("fitSign",AliDielectronSignalFunc::PeakFunGaus,minFit,maxFit,3); // has 3 parameters
  //  sig->SetMCSignalShape(hMCsign);
  //  TF1 *fS = new TF1("fitSign",AliDielectronSignalFunc::PeakFunMC,minFit,maxFit,1); // requires a MC shape
  3.2) set the method for the signal extraction (methods can be found in AliDielectronSignalBase)
  depending on the method serveral inputs are needed (e.g. MC shape, PDG code of the particle of interest)
  //  sig->SetParticleOfInterest(443); //default is jpsi
  //  sig->SetMCSignalShape(signalMC);
  //  sig->SetIntegralRange(minInt, maxInt);
  sig->SetExtractionMethod(AliDielectronSignal::BinCounting); // this is the default


  4) combined fit of bgrd+signal

  4.1) combine the two functions
  sig->CombineFunc(fS,fB);
  4.2) apply fitting ranges and the fit options
  sig->SetFitRange(minFit, maxFit);
  sig->SetFitOption("NR");


  5) start the processing

  sig->Process(arrHists);
  sig->Print(""); // print values and errors extracted


  6) access the spectra and values created

  6.1) standard spectra as provided filled in AliDielectronSignalExt
  TH1F *hsign = (TH1F*) sig->GetUnlikeSignHistogram();  // same as the input (rebinned)
  TH1F *hbgrd = (TH1F*) sig->GetBackgroundHistogram();  // filled histogram with fitBgrd
  TH1F *hextr = (TH1F*) sig->GetSignalHistogram();      // after backgound extraction (rebinned)
  TObject *oPeak = (TObject*) sig->GetPeakShape();      // can be a TF1 or TH1 depending on the method
  6.2) flow spectra
  TF1 *fFitSign  = sig->GetCombinedFunction();                // combined fit function
  TF1 *fFitExtr  = sig->GetSignalFunction();                  // signal function
  TF1 *fFitBgrd  = sig->GetBackgroundFunction();              // background function
  6.3) access the extracted values and errors
  sig->GetValues();     or GetErrors();                 // yield extraction