Additional protection
[u/mrichter/AliRoot.git] / VZERO / AliVZERODigitizer.cxx
index 7acb828..7fe9308 100644 (file)
  * provided "as is" without express or implied warranty.                  *
  **************************************************************************/
  
-//_________________________________________________________________________
-//
-// This  constructs Digits out of Hits
-//
+/* $Id$ */
+
+///_________________________________________________________________________
+///
+/// This class constructs Digits out of Hits
+///
+///
 
 // --- Standard library ---
-#include <Riostream.h>
-#include <stdlib.h>
 
 // --- ROOT system ---
-#include <TFile.h>
-#include <TFolder.h>
-#include <TROOT.h>
-#include <TSystem.h>
+#include <TMath.h>
 #include <TTree.h>
-#include <TVirtualMC.h>
+#include <TMap.h>
+#include <TGeoManager.h>
+#include <TGeoPhysicalNode.h>
+#include <AliGeomManager.h>
+#include <TRandom.h>
+#include <TF1.h>
+#include <TH1F.h>
 
 // --- AliRoot header files ---
-#include "AliVZEROConst.h"
 #include "AliRun.h"
 #include "AliVZERO.h"
 #include "AliVZEROhit.h"
-#include "AliHit.h"
-#include "AliDetector.h"
 #include "AliRunLoader.h"
 #include "AliLoader.h"
-#include "AliConfig.h"
+#include "AliGRPObject.h"
 #include "AliRunDigitizer.h"
-#include "AliDigitizer.h"
-#include "AliHeader.h"
-#include "AliStack.h"
-#include "AliVZERODigitizer.h"
+#include "AliCDBManager.h"
+#include "AliCDBStorage.h"
+#include "AliCDBEntry.h"
+#include "AliVZEROCalibData.h"
+#include "AliCTPTimeParams.h"
 #include "AliVZEROdigit.h"
-#include "AliMC.h"
+#include "AliVZERODigitizer.h"
+#include "AliVZEROSDigit.h"
 
 ClassImp(AliVZERODigitizer)
 
  AliVZERODigitizer::AliVZERODigitizer()
+                   :AliDigitizer(),
+                    fCalibData(GetCalibData()),
+                    fPhotoCathodeEfficiency(0.18),
+                    fNdigits(0),
+                    fDigits(0),
+                    fSignalShape(NULL),
+                    fPMResponse(NULL),
+                    fSinglePhESpectrum(NULL),
+                   fEvenOrOdd(kFALSE),
+                   fTask(kHits2Digits),
+                   fVZERO(NULL)
 {
-   if (!fDigits) fDigits = new TClonesArray("AliVZEROdigit", 1000);
-   
-   fNevents = 0 ;     
-   fDigits = 0 ;
-   fNdigits = 0;
-   fHits = 0 ;
-   fRunLoader = 0;
-  
-   fPhotoCathodeEfficiency =   0.18;
-   fPMVoltage              =  768.0;
-   fPMGain = TMath::Power((fPMVoltage / 112.5) ,7.04277);     
+  // default constructor
+  // Initialize OCDB and containers used in the digitization
+
+  Init();
 }
 
 //____________________________________________________________________________ 
+  AliVZERODigitizer::AliVZERODigitizer(AliVZERO *vzero, DigiTask_t task)
+                    :AliDigitizer(),
+                    fCalibData(GetCalibData()),
+                     fPhotoCathodeEfficiency(0.18),
+                    fNdigits(0),
+                     fDigits(0),
+                    fSignalShape(NULL),
+                     fPMResponse(NULL),
+                     fSinglePhESpectrum(NULL),
+                    fEvenOrOdd(kFALSE),
+                    fTask(task),
+                    fVZERO(vzero)
+{
+  // constructor
+  // Initialize OCDB and containers used in the digitization
+
+  Init();
+}
+           
+//____________________________________________________________________________ 
   AliVZERODigitizer::AliVZERODigitizer(AliRunDigitizer* manager)
-                    :AliDigitizer(manager)
-                    
+                    :AliDigitizer(manager),
+                    fCalibData(GetCalibData()),
+                     fPhotoCathodeEfficiency(0.18),
+                    fNdigits(0),
+                     fDigits(0),
+                    fSignalShape(NULL),
+                     fPMResponse(NULL),
+                     fSinglePhESpectrum(NULL),
+                    fEvenOrOdd(kFALSE),
+                    fTask(kHits2Digits),
+                    fVZERO(NULL)
 {
   // constructor
-  
-  fNevents = 0;     
-  fDigits = 0;
-  fNdigits = 0;
-  fHits = 0;
-  fRunLoader = 0;
-  
-  fPhotoCathodeEfficiency =   0.18;
-  fPMVoltage              =  768.0;
-  fPMGain = TMath::Power( (fPMVoltage / 112.5) ,7.04277 );
+  // Initialize OCDB and containers used in the digitization
+
+  Init();
 }
            
 //____________________________________________________________________________ 
@@ -91,149 +120,521 @@ ClassImp(AliVZERODigitizer)
   if (fDigits) {
     fDigits->Delete();
     delete fDigits;
-    fDigits=0; }
+    fDigits=0; 
+  }
+
+  if (fSignalShape) {
+    delete fSignalShape;
+    fSignalShape = NULL;
+  }
+  if (fPMResponse) {
+    delete fPMResponse;
+    fPMResponse = NULL;
+  }
+  if (fSinglePhESpectrum) {
+    delete fSinglePhESpectrum;
+    fSinglePhESpectrum = NULL;
+  }
+
+  for(Int_t i = 0 ; i < 64; ++i) {
+    if (fTime[i]) delete [] fTime[i];
+  }
 }
 
-//____________________________________________________________________________
-void AliVZERODigitizer::OpengAliceFile(const char *file)
+//_____________________________________________________________________________
+Bool_t AliVZERODigitizer::Init()
 {
-  // Loads galice.root file and corresponding header, kinematics
-  // hits and  digits 
-  
-  fRunLoader = AliRunLoader::Open(file,AliConfig::fgkDefaultEventFolderName,
-                                  "UPDATE");
-  
-  if (!fRunLoader)
-   {
-     Error("Open","Can not open session for file %s.",file);
-   }
-  
-  fRunLoader->LoadgAlice();
-  fRunLoader->LoadHeader();
-  fRunLoader->LoadKinematics();
+  // Initialises the digitizer
+  // Initialize OCDB and containers used in the digitization
 
-  gAlice = fRunLoader->GetAliRun();
-  
-  if (gAlice)
-    { printf("<AliVZEROdigitizer::Open> ");
-      printf("AliRun object found on file.\n");}
-  else
-    { printf("<AliVZEROdigitizer::Open> ");
-      printf("Could not find AliRun object.\n");}
-    
-  // Initialise Hit and Digit arrays
-  fHits   = new TClonesArray ("AliVZEROhit", 1000);
-  fDigits = new TClonesArray ("AliVZEROdigit", 1000);
-
-  fVZERO  = (AliVZERO*) gAlice->GetDetector("VZERO");
-  fVZEROLoader = fRunLoader->GetLoader("VZEROLoader");
+  // check if the digitizer was already initialized
+  if (fSignalShape) return kTRUE;
+
+  fSignalShape = new TF1("VZEROSignalShape",this,&AliVZERODigitizer::SignalShape,0,200,6,"AliVZERODigitizer","SignalShape");
+  //  fSignalShape->SetParameters(0,1.57345e1,-4.25603e-1,2.9,6.40982,3.69339e-01);
+  //  fSignalShape->SetParameters(1.34330e+00,1.13007e+02,-4.95705e-01,
+  //                         3.68911e+00,1.01040e+00, 3.94675e-01);
+  fSignalShape->SetParameters(-1.07335e+00,2.16002e+01,-1.26133e-01,
+                             1.41619e+00,5.50334e-01,3.86111e-01);
+  fPMResponse = new TF1("VZEROPMResponse",this,&AliVZERODigitizer::PMResponse,-kPMRespTime,2.*kPMRespTime,0,"AliVZERODigitizer","PMResponse");
+  fSinglePhESpectrum = new TF1("VZEROSinglePhESpectrum",this,&AliVZERODigitizer::SinglePhESpectrum,0,20,0,"AliVZERODigitizer","SinglePhESpectrum");
   
-  if (fVZEROLoader == 0x0){
-      cerr<<"Hits2Digits : Can not find VZERO or VZEROLoader\n";}
-    
-  Int_t retval = fVZEROLoader->LoadHits("read");
-  if (retval){
-     Error("Open","Error occured while loading hits... Exiting.");
-     return;}
-      
-  fVZEROLoader->LoadDigits("recreate");  
+  // Now get the CTP L0->L1 delay
+  AliCDBEntry *entry = AliCDBManager::Instance()->Get("GRP/CTP/CTPtiming");
+  if (!entry) AliFatal("CTP timing parameters are not found in OCDB !");
+  AliCTPTimeParams *ctpParams = (AliCTPTimeParams*)entry->GetObject();
+  Float_t l1Delay = (Float_t)ctpParams->GetDelayL1L0()*25.0;
+
+  AliCDBEntry *entry1 = AliCDBManager::Instance()->Get("GRP/CTP/TimeAlign");
+  if (!entry1) AliFatal("CTP time-alignment is not found in OCDB !");
+  AliCTPTimeParams *ctpTimeAlign = (AliCTPTimeParams*)entry1->GetObject();
+  l1Delay += ((Float_t)ctpTimeAlign->GetDelayL1L0()*25.0);
+
+  AliCDBEntry *entry2 = AliCDBManager::Instance()->Get("VZERO/Calib/TimeDelays");
+  if (!entry2) AliFatal("VZERO time delays are not found in OCDB !");
+  TH1F *delays = (TH1F*)entry2->GetObject();
+
+  for(Int_t i = 0 ; i < 64; ++i) {
+
+    for(Int_t j = 0; j < kNClocks; ++j) fAdc[i][j] = 0;
+    fLeadingTime[i] = fTimeWidth[i] = 0;
+
+    fPmGain[i] = fCalibData->GetGain(i);
+
+    fAdcPedestal[i][0] = fCalibData->GetPedestal(i);
+    fAdcSigma[i][0]    = fCalibData->GetSigma(i); 
+    fAdcPedestal[i][1] = fCalibData->GetPedestal(i+64);
+    fAdcSigma[i][1]    = fCalibData->GetSigma(i+64); 
+
+    Int_t board = AliVZEROCalibData::GetBoardNumber(i);
+    fNBins[i] = TMath::Nint(((Float_t)(fCalibData->GetMatchWindow(board)+1)*25.0+
+                            (Float_t)kMaxTDCWidth*fCalibData->GetWidthResolution(board))/
+                           fCalibData->GetTimeResolution(board));
+    fNBinsLT[i] = TMath::Nint(((Float_t)(fCalibData->GetMatchWindow(board)+1)*25.0)/
+                             fCalibData->GetTimeResolution(board));
+    fBinSize[i] = fCalibData->GetTimeResolution(board);
+    fHptdcOffset[i] = (((Float_t)fCalibData->GetTriggerCountOffset(board)-
+                       (Float_t)fCalibData->GetRollOver(board))*25.0+
+                      fCalibData->GetTimeOffset(i)-
+                      l1Delay+
+                      delays->GetBinContent(i+1)+
+                      kV0Offset);
+
+    fTime[i] = new Float_t[fNBins[i]];
+    memset(fTime[i],0,fNBins[i]*sizeof(Float_t));
+  }
+
+  return kTRUE;
 }
 
 //____________________________________________________________________________
-void AliVZERODigitizer::Exec() 
- { 
+void AliVZERODigitizer::Exec(Option_t* /*option*/) 
+{   
+  // Creates digits from hits
+  fNdigits = 0;  
 
-  Int_t nbytes;
-  fNdigits = 0;
-  Int_t N; 
-  Int_t map[96];
-  Int_t cell = 0;
-  Float_t cPM = fPhotoCathodeEfficiency * fPMGain;
-            
-  for(Int_t i=0; i<96; i++) map[i] = 0; 
-          
-  fNevents = (Int_t) fRunLoader->TreeE()->GetEntries ();  
-  printf(" Number of events in file =  %d \n", fNevents);
-  
-  for (Int_t ievent = 0; ievent < fNevents; ievent++){
-      
-      for(Int_t i=0; i<96; i++) map[i] = 0;     
-      
-      fRunLoader->GetEvent(ievent);
-      
-      fTreeH = fVZEROLoader->TreeH();
-      if (fTreeH == 0x0)
-       { Error("Exec","Cannot get TreeH");
-         return; }
-             
-      fTreeD = fVZEROLoader->TreeD();
-      if (fTreeD == 0x0)
-      { fVZEROLoader->MakeTree("D");
-        fVZEROLoader->MakeDigitsContainer();
-        fTreeD = fVZEROLoader->TreeD(); }
-       
-      Int_t bufsize = 16000;
-      fTreeD->Branch("VZERODigit", &fDigits, bufsize); 
-      
-//    Now make Digits from hits
-
-      if (fVZERO)
-       {
-         fHits = fVZERO->Hits();
-         
-         Int_t ntracks = (Int_t) fTreeH->GetEntries ();
-//      printf(" Number of Tracks in the TreeH = %d \n", ntracks);
-         for (Int_t track = 0; track < ntracks; track++)
-           {
-             gAlice->ResetHits ();
-             nbytes += fTreeH->GetEvent(track);
-             fParticle = fRunLoader->Stack()->Particle(track);
-             Int_t nhits = fHits->GetEntriesFast();
-             for (Int_t hit = 0; hit < nhits; hit++)
-                 {
-                   fVZEROHit = (AliVZEROhit *)fHits->UncheckedAt(hit);
-                  N    = fVZEROHit->Nphot();
-                  cell = fVZEROHit->Cell();                                    
-                  map[cell] = map[cell] + N;
-                 }           // hit   loop
-           }                 // track loop
-            
-           Int_t icount = 0; 
-          
-           for(Int_t i=0; i<96; i++) {
-             Float_t q1 = Float_t ( map[i] )* cPM * kQe;
-             Float_t noise = gRandom->Gaus(10.5,3.22);
-              Float_t PMresponse  =  q1/kC*TMath::Power(ktheta/kthau,1/(1-ktheta/kthau)) 
-                                 + noise*1e-3;
-             map[i] = Int_t( PMresponse * 200.0);
-             if(map[i] > 3) {
-                icount++;
-//              printf(" Event, cell, adc = %d %d %d\n", ievent, i, map[i]);
-                AddDigit(ievent, i, map[i]);} 
-            }
-
-           fTreeD->Reset();
-           fTreeD->Fill();
-          ResetDigit();
-           fVZEROLoader->WriteDigits("OVERWRITE");  
-          fVZEROLoader->UnloadDigits();     
-      }                     // VZERO loop
-    }  //event loop
+  if (fVZERO && !fManager) {
+    AliLoader *loader = fVZERO->GetLoader();
+    if (!loader) {
+      AliError("Can not get VZERO Loader via AliVZERO object!");
+      return;
+    }
+    AliRunLoader* runLoader = AliRunLoader::Instance();
+    for (Int_t iEvent = 0; iEvent < runLoader->GetNumberOfEvents(); ++iEvent) {
+      runLoader->GetEvent(iEvent);
+      if (fTask == kHits2Digits) {
+       DigitizeHits();
+       DigitizeSDigits();
+       WriteDigits(loader);
+      }
+      else {
+       DigitizeHits();
+       WriteSDigits(loader);
+      }
+    }
+  }
+  else if (fManager) {
+      ReadSDigits();
+      DigitizeSDigits();
+      AliRunLoader *currentLoader = AliRunLoader::GetRunLoader(fManager->GetOutputFolderName());
+      AliLoader *loader = currentLoader->GetLoader("VZEROLoader");
+      if (!loader) { 
+       AliError("Cannot get VZERO Loader via RunDigitizer!");
+       return;
+      }
+      WriteDigits(loader);
+  }
+  else {
+    AliFatal("Invalid digitization task! Exiting!");
+  }
 }
 
 //____________________________________________________________________________
-void AliVZERODigitizer::AddDigit(Int_t eventnumber, Int_t cellnumber, Int_t adc) 
+void AliVZERODigitizer::AddDigit(Int_t pmnumber, Float_t time, Float_t width, Bool_t integrator, Short_t *chargeADC, Int_t *labels) 
  { 
  
 // Adds Digit 
  
   TClonesArray &ldigits = *fDigits;  
-  new(ldigits[fNdigits++]) AliVZEROdigit(eventnumber,cellnumber,adc);
+        
+  new(ldigits[fNdigits++]) AliVZEROdigit(pmnumber,time,width,integrator,chargeADC,labels);
+        
+}
+//____________________________________________________________________________
+void AliVZERODigitizer::AddSDigit(Int_t pmnumber, Int_t nbins, Float_t *charges, Int_t *labels) 
+ { 
+// Adds SDigit 
+  TClonesArray &ldigits = *fDigits;  
+        
+  new(ldigits[fNdigits++]) AliVZEROSDigit(pmnumber,nbins,charges,labels);
+        
 }
 //____________________________________________________________________________
-void AliVZERODigitizer::ResetDigit()
+void AliVZERODigitizer::ResetDigits()
 {
+
 // Clears Digits
+
   fNdigits = 0;
   if (fDigits) fDigits->Clear();
 }
+
+//____________________________________________________________________________
+AliVZEROCalibData* AliVZERODigitizer::GetCalibData() const
+
+{
+  AliCDBManager *man = AliCDBManager::Instance();
+
+  AliCDBEntry *entry=0;
+
+  entry = man->Get("VZERO/Calib/Data");
+
+//   if(!entry){
+//     AliWarning("Load of calibration data from default storage failed!");
+//     AliWarning("Calibration data will be loaded from local storage ($ALICE_ROOT)");
+//     Int_t runNumber = man->GetRun();
+//     entry = man->GetStorage("local://$ALICE_ROOT/OCDB")
+//       ->Get("VZERO/Calib/Data",runNumber);
+//     
+//   }
+
+  // Retrieval of data in directory VZERO/Calib/Data:
+
+
+  AliVZEROCalibData *calibdata = 0;
+
+  if (entry) calibdata = (AliVZEROCalibData*) entry->GetObject();
+  if (!calibdata)  AliFatal("No calibration data from calibration database !");
+
+  return calibdata;
+
+}
+
+double AliVZERODigitizer::SignalShape(double *x, double *par)
+{
+  // this function simulates the time
+  // of arrival of the photons at the
+  // photocathode
+  Double_t xx = x[0];
+  if (xx <= par[0]) return 0;
+  Double_t a = 1./TMath::Power((xx-par[0])/par[1],1./par[2]);
+  if (xx <= par[3]) return a;
+  Double_t b = 1./TMath::Power((xx-par[3])/par[4],1./par[5]);
+  Double_t f = a*b/(a+b);
+  AliDebug(100,Form("x=%f func=%f",xx,f));
+  return f;
+}
+
+double AliVZERODigitizer::PMResponse(double *x, double * /* par */)
+{
+  // this function describes the
+  // PM time response to a single
+  // photoelectron
+  Double_t xx = x[0]+kPMRespTime;
+  return xx*xx*TMath::Exp(-xx*xx/(kPMRespTime*kPMRespTime));
+}
+
+double AliVZERODigitizer::SinglePhESpectrum(double *x, double * /* par */)
+{
+  // this function describes the
+  // PM amplitude response to a single
+  // photoelectron
+  Double_t xx = x[0];
+  if (xx < 0) return 0;
+  return (TMath::Poisson(xx,kPMNbOfSecElec)+kPMTransparency*TMath::Poisson(xx,1.0));
+}
+
+Int_t AliVZERODigitizer::Cell2Pmt(Int_t cell) const
+{
+  // The method maps the scintillator
+  // indexes to the PM ones
+  if (cell < 0 || cell >= 80) {
+    AliError(Form("Wrong VZERO cell index %d",cell));
+    return -1;
+  }
+  if (cell < 16) return cell;
+  if (cell < 48) return 8 + cell/2;
+  return cell - 16;
+}
+
+void AliVZERODigitizer::DigitizeHits()
+{
+  // Digitize the hits to the level of
+  // SDigits (fTime arrays)
+
+  for(Int_t i = 0 ; i < 64; ++i) {
+    memset(fTime[i],0,fNBins[i]*sizeof(Float_t));
+    fLabels[i][0] = fLabels[i][1] = fLabels[i][2] = -1;
+  }
+  Float_t integral = fPMResponse->Integral(-kPMRespTime,2.*kPMRespTime);
+  Float_t meansPhE = fSinglePhESpectrum->Mean(0,20);
+
+     AliLoader* loader = fVZERO->GetLoader();
+     if (!loader) {
+       AliError("Can not get VZERO Loader!");
+       return;
+     }
+     loader->LoadHits();
+     TTree* treeH = loader->TreeH();
+     if (!treeH) {
+       AliError("Cannot get TreeH!");
+       return;
+     }
+     TClonesArray* hits = fVZERO->Hits();
+
+     //     Float_t lightYieldCorr[64] = {0.00707,0.00517,0.00520,0.00537,0.00735,0.00537,0.00733,0.00605,0.00778,0.00749,0.00701,0.00755,0.00732,0.00617,0.00669,0.00525,0.00752,0.00820,0.00797,0.01107,0.01080,0.00889,0.00880,0.01712,0.00866,0.00701,0.00811,0.00602,0.00879,0.00821,0.00861,0.01433,0.00061,0.00032,0.00099,0.00061,0.00034,0.00046,0.00031,0.00122,0.00155,0.00091,0.00032,0.00096,0.00120,0.00067,0.00113,0.00060,0.00158,0.00136,0.00340,0.00066,0.00076,0.00119,0.00129,0.00147,0.00137,0.00117,0.00088,0.00164,0.00128,0.00081,0.00121,0.00250};
+     Float_t lightYieldCorr[64] = {0.01173,0.00874,0.00878,0.00886,0.01151,0.00925,0.01167,0.00983,0.01181,0.01243,0.01115,0.01220,0.01228,0.01053,0.01021,0.00930,0.01270,0.01411,0.01316,0.01894,0.01923,0.01860,0.01738,0.00305,0.01584,0.01251,0.01344,0.00310,0.01302,0.01266,0.01407,0.00338,0.00089,0.00100,0.00130,0.00081,0.00052,0.01230,0.00059,0.02452,0.02980,0.00137,0.01421,0.00116,0.00141,0.00092,0.02480,0.00096,0.00182,0.00174,0.00218,0.00106,0.00116,0.00160,0.00162,0.03097,0.00194,0.00171,0.00132,0.00239,0.00173,0.00118,0.00163,0.00262};
+//  Now makes Digits from hits
+     Int_t nTracks = (Int_t) treeH->GetEntries();
+     for (Int_t iTrack = 0; iTrack < nTracks; iTrack++) {
+         fVZERO->ResetHits();
+         treeH->GetEvent(iTrack);
+         Int_t nHits = hits->GetEntriesFast();
+         for (Int_t iHit = 0; iHit < nHits; iHit++) {
+          AliVZEROhit* hit = (AliVZEROhit *)hits->UncheckedAt(iHit);
+          Int_t nPhot = hit->Nphot();
+          Int_t cell  = hit->Cell();                          
+          Int_t pmt = Cell2Pmt(cell);
+          Int_t trackLabel = hit->GetTrack();
+          for(Int_t l = 0; l < 3; ++l) {
+            if (fLabels[pmt][l] < 0) {
+              fLabels[pmt][l] = trackLabel;
+              break;
+            }
+          }
+          Float_t dt_scintillator = gRandom->Gaus(0,kIntTimeRes);
+          Float_t t = dt_scintillator + 1e9*hit->Tof();
+          if (pmt < 32) t += kV0CDelayCables;
+          t += fHptdcOffset[pmt];
+          Int_t nPhE;
+          Float_t prob = lightYieldCorr[pmt]*fPhotoCathodeEfficiency; // Optical losses included!
+          if (nPhot > 100)
+            nPhE = (Int_t)gRandom->Gaus(prob*Float_t(nPhot)+0.5,
+                                        sqrt(Float_t(nPhot)*prob*(1.-prob)));
+          else
+            nPhE = gRandom->Binomial(nPhot,prob);
+          Float_t charge = TMath::Qe()*fPmGain[pmt]*fBinSize[pmt]/integral;
+          for (Int_t iPhE = 0; iPhE < nPhE; ++iPhE) {
+            Float_t tPhE = t + fSignalShape->GetRandom(0,fBinSize[pmt]*Float_t(fNBins[pmt]));
+            Float_t gainVar = fSinglePhESpectrum->GetRandom(0,20)/meansPhE;
+            Int_t firstBin = TMath::Max(0,(Int_t)((tPhE-kPMRespTime)/fBinSize[pmt]));
+            Int_t lastBin = TMath::Min(fNBins[pmt]-1,(Int_t)((tPhE+2.*kPMRespTime)/fBinSize[pmt]));
+            for(Int_t iBin = firstBin; iBin <= lastBin; ++iBin) {
+              Float_t tempT = fBinSize[pmt]*(0.5+iBin)-tPhE;
+              fTime[pmt][iBin] += gainVar*charge*fPMResponse->Eval(tempT);
+            }
+          }         // ph.e. loop
+         }           // hit loop
+     }               // track loop
+     loader->UnloadHits();
+}
+
+
+void AliVZERODigitizer::DigitizeSDigits()
+{
+  // Digitize the fTime arrays (SDigits) to the level of
+  // Digits (fAdc arrays)
+  for(Int_t i = 0 ; i < 64; ++i) {
+    for(Int_t j = 0; j < kNClocks; ++j) fAdc[i][j] = 0;
+    fLeadingTime[i] = fTimeWidth[i] = 0;
+  }
+
+  Float_t maximum = 0.9*fSignalShape->GetMaximum(0,200); // Not exact, one needs to do this on the convoluted
+  Float_t integral2 = fSignalShape->Integral(0,200); // function. Anyway the effect is small <10% on the 2.5 ADC thr
+  for (Int_t ipmt = 0; ipmt < 64; ++ipmt) {
+    Float_t thr = fCalibData->GetDiscriThr(ipmt)*kChargePerADC*maximum*fBinSize[ipmt]/integral2;
+    Bool_t ltFound = kFALSE, ttFound = kFALSE;
+    for (Int_t iBin = 0; iBin < fNBins[ipmt]; ++iBin) {
+      Float_t t = fBinSize[ipmt]*Float_t(iBin);
+      if (fTime[ipmt][iBin] > thr) {
+       if (!ltFound && (iBin < fNBinsLT[ipmt])) {
+         ltFound = kTRUE;
+         fLeadingTime[ipmt] = t;
+       }
+      }
+      else {
+       if (ltFound) {
+         if (!ttFound) {
+           ttFound = kTRUE;
+           fTimeWidth[ipmt] = t - fLeadingTime[ipmt];
+         }
+       }
+      }
+      Float_t tadc = t - kClockOffset - fCalibData->GetTimeOffset(ipmt);
+      Int_t clock = kNClocks/2 - Int_t(tadc/25.0);
+      if (clock >= 0 && clock < kNClocks)
+       fAdc[ipmt][clock] += fTime[ipmt][iBin]/kChargePerADC;
+    }
+    Int_t board = AliVZEROCalibData::GetBoardNumber(ipmt);
+    if (ltFound && ttFound) {
+      fTimeWidth[ipmt] = fCalibData->GetWidthResolution(board)*
+       Float_t(Int_t(fTimeWidth[ipmt]/fCalibData->GetWidthResolution(board)));
+      if (fTimeWidth[ipmt] < Float_t(kMinTDCWidth)*fCalibData->GetWidthResolution(board))
+       fTimeWidth[ipmt] = Float_t(kMinTDCWidth)*fCalibData->GetWidthResolution(board);
+      if (fTimeWidth[ipmt] > Float_t(kMaxTDCWidth)*fCalibData->GetWidthResolution(board))
+       fTimeWidth[ipmt] = Float_t(kMaxTDCWidth)*fCalibData->GetWidthResolution(board);
+    }
+  }
+
+  fEvenOrOdd = gRandom->Integer(2);
+  for (Int_t j=0; j<64; ++j){
+    for (Int_t iClock = 0; iClock < kNClocks; ++iClock) {
+      Int_t integrator = (iClock + fEvenOrOdd) % 2;
+      fAdc[j][iClock]  += gRandom->Gaus(fAdcPedestal[j][integrator], fAdcSigma[j][integrator]);
+    }
+  }
+       
+}
+
+void AliVZERODigitizer::WriteDigits(AliLoader *loader)
+{
+  // Take fAdc arrays filled by the previous
+  // method and produce and add digits to the digit Tree
+
+  loader->LoadDigits("UPDATE");
+
+  if (!loader->TreeD()) loader->MakeTree("D");
+  loader->MakeDigitsContainer();
+  TTree* treeD  = loader->TreeD();
+  DigitsArray();
+  treeD->Branch("VZERODigit", &fDigits); 
+  
+  Short_t *chargeADC = new Short_t[kNClocks];
+  for (Int_t i=0; i<64; i++) {      
+    for (Int_t j = 0; j < kNClocks; ++j) {
+      Int_t tempadc = Int_t(fAdc[i][j]);
+      if (tempadc > 1023) tempadc = 1023;
+      chargeADC[j] = tempadc;
+    }
+    AddDigit(i, fLeadingTime[i], fTimeWidth[i], Bool_t((10+fEvenOrOdd)%2), chargeADC, fLabels[i]);
+  }
+  delete [] chargeADC;
+
+  treeD->Fill();
+  loader->WriteDigits("OVERWRITE");  
+  loader->UnloadDigits();     
+  ResetDigits();
+}
+
+void AliVZERODigitizer::WriteSDigits(AliLoader *loader)
+{
+  // Take fTime arrays filled by the previous
+  // method and produce and add sdigits to the sdigit Tree
+
+  loader->LoadSDigits("UPDATE");
+
+  if (!loader->TreeS()) loader->MakeTree("S");
+  loader->MakeSDigitsContainer();
+  TTree* treeS  = loader->TreeS();
+  SDigitsArray();
+  treeS->Branch("VZEROSDigit", &fDigits); 
+  
+  for (Int_t ipmt = 0; ipmt < 64; ++ipmt) {
+    AddSDigit(ipmt,fNBins[ipmt],fTime[ipmt],fLabels[ipmt]);
+  }
+
+  treeS->Fill();
+  loader->WriteSDigits("OVERWRITE");  
+  loader->UnloadSDigits();     
+  ResetDigits();
+}
+
+void AliVZERODigitizer::ReadSDigits()
+{
+  // Read SDigits which are then to precessed
+  // in the following method
+  for(Int_t i = 0 ; i < 64; ++i) {
+    memset(fTime[i],0,fNBins[i]*sizeof(Float_t));
+    fLabels[i][0] = fLabels[i][1] = fLabels[i][2] = -1;
+  }
+
+  // Loop over input files
+  Int_t nFiles= fManager->GetNinputs();
+  for (Int_t inputFile = 0; inputFile < nFiles; inputFile++) {
+    // Get the current loader 
+    AliRunLoader* currentLoader = 
+      AliRunLoader::GetRunLoader(fManager->GetInputFolderName(inputFile));
+
+    AliLoader *loader = currentLoader->GetLoader("VZEROLoader");
+    loader->LoadSDigits("READ");
+  
+    // Get the tree of summable digits
+    TTree* sdigitsTree = loader->TreeS();
+    if (!sdigitsTree)  {
+      AliError("No sdigit tree from manager");
+      continue;
+    }
+
+    // Get the branch 
+    TBranch* sdigitsBranch = sdigitsTree->GetBranch("VZEROSDigit");
+    if (!sdigitsBranch) {
+      AliError("Failed to get sdigit branch");
+      return;
+    }
+
+    // Set the branch address
+    TClonesArray *sdigitsArray = NULL;
+    sdigitsBranch->SetAddress(&sdigitsArray);
+
+    // Sum contributions from the sdigits
+    // Get number of entries in the tree 
+    Int_t nentries  = Int_t(sdigitsBranch->GetEntries());
+    for (Int_t entry = 0; entry < nentries; ++entry)  {
+      sdigitsBranch->GetEntry(entry);
+      // Get the number of sdigits 
+      Int_t nsdigits = sdigitsArray->GetEntries();
+      for (Int_t sdigit = 0; sdigit < nsdigits; sdigit++) {
+       AliVZEROSDigit* sDigit = static_cast<AliVZEROSDigit*>(sdigitsArray->UncheckedAt(sdigit));
+       Int_t pmNumber = sDigit->PMNumber();
+       Int_t nbins = sDigit->GetNBins();
+       if (nbins != fNBins[pmNumber]) {
+         AliError(Form("Incompatible number of bins between digitizer (%d) and sdigit (%d) for PM %d! Skipping sdigit!",
+                       fNBins[pmNumber],nbins,pmNumber));
+         continue;
+       }
+       // Sum the charges
+       Float_t *charges = sDigit->GetCharges();
+       for(Int_t iBin = 0; iBin < nbins; ++iBin) fTime[pmNumber][iBin] += charges[iBin];
+       // and the labels
+       Int_t *labels = sDigit->GetTracks();
+       Int_t j = 0;
+       for(Int_t i = 0; i < 3; ++i) {
+         if (fLabels[pmNumber][i] < 0) {
+           if (labels[j] < 0) break;
+           fLabels[pmNumber][i] = labels[j];
+           j++;
+         }
+       }
+      }
+    }
+    loader->UnloadSDigits();
+  }
+}
+
+//____________________________________________________________________
+TClonesArray*
+AliVZERODigitizer::DigitsArray() 
+{
+  // Initialize digit array if not already and
+  // return pointer to it. 
+  if (!fDigits) { 
+    fDigits = new TClonesArray("AliVZEROdigit", 64);
+    fNdigits = 0;
+  }
+  return fDigits;
+}
+
+//____________________________________________________________________
+TClonesArray*
+AliVZERODigitizer::SDigitsArray() 
+{
+  // Initialize sdigit array if not already and
+  // return pointer to it. 
+  if (!fDigits) { 
+    fDigits = new TClonesArray("AliVZEROSDigit", 64);
+    fNdigits = 0;
+  }
+  return fDigits;
+}