VZERO/AliVZERODigitizer.cxx

   1 /**************************************************************************
   2  * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
   3  *                                                                        *
   4  * Author: The ALICE Off-line Project.                                    *
   5  * Contributors are mentioned in the code where appropriate.              *
   6  *                                                                        *
   7  * Permission to use, copy, modify and distribute this software and its   *
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  10  * copies and that both the copyright notice and this permission notice   *
  11  * appear in the supporting documentation. The authors make no claims     *
  12  * about the suitability of this software for any purpose. It is          *
  13  * provided "as is" without express or implied warranty.                  *
  14  **************************************************************************/
  15
  16 /* $Id$ */
  17
  18 ///_________________________________________________________________________
  19 ///
  20 /// This class constructs Digits out of Hits
  21 ///
  22 ///
  23
  24 // --- Standard library ---
  25
  26 // --- ROOT system ---
  27 #include <TMath.h>
  28 #include <TTree.h>
  29 #include <TMap.h>
  30 #include <TGeoManager.h>
  31 #include <TGeoPhysicalNode.h>
  32 #include <AliGeomManager.h>
  33 #include <TRandom.h>
  34 #include <TF1.h>
  35 #include <TH1F.h>
  36
  37 // --- AliRoot header files ---
  38 #include "AliRun.h"
  39 #include "AliVZERO.h"
  40 #include "AliVZEROhit.h"
  41 #include "AliRunLoader.h"
  42 #include "AliLoader.h"
  43 #include "AliGRPObject.h"
  44 #include "AliRunDigitizer.h"
  45 #include "AliCDBManager.h"
  46 #include "AliCDBStorage.h"
  47 #include "AliCDBEntry.h"
  48 #include "AliVZEROCalibData.h"
  49 #include "AliCTPTimeParams.h"
  50 #include "AliVZEROdigit.h"
  51 #include "AliVZERODigitizer.h"
  52
  53 ClassImp(AliVZERODigitizer)
  54
  55  AliVZERODigitizer::AliVZERODigitizer()
  56                    :AliDigitizer(),
  57                     fCalibData(GetCalibData()),
  58                     fPhotoCathodeEfficiency(0.18),
  59                     fNdigits(0),
  60                     fDigits(0),
  61                     fSignalShape(NULL),
  62                     fPMResponse(NULL),
  63                     fSinglePhESpectrum(NULL)
  64
  65 {
  66   // default constructor
  67
  68 //    fNdigits = 0;
  69 //    fDigits  = 0;
  70 //
  71 //    fPhotoCathodeEfficiency =   0.18;
  72 //    fPMVoltage              =  768.0;
  73 //    fPMGain = TMath::Power((fPMVoltage / 112.5) ,7.04277);
  74
  75 //   fCalibData = GetCalibData();
  76
  77   fSignalShape = new TF1("VZEROSignalShape",this,&AliVZERODigitizer::SignalShape,0,200,6,"AliVZERODigitizer","SignalShape");
  78   //  fSignalShape->SetParameters(0,1.57345e1,-4.25603e-1,2.9,6.40982,3.69339e-01);
  79   //  fSignalShape->SetParameters(1.34330e+00,1.13007e+02,-4.95705e-01,
  80   //                          3.68911e+00,1.01040e+00, 3.94675e-01);
  81   fSignalShape->SetParameters(-1.07335e+00,2.16002e+01,-1.26133e-01,
  82                               1.41619e+00,5.50334e-01,3.86111e-01);
  83
  84   fPMResponse = new TF1("VZEROPMResponse",this,&AliVZERODigitizer::PMResponse,-kPMRespTime,2.*kPMRespTime,0,"AliVZERODigitizer","PMResponse");
  85   fSinglePhESpectrum = new TF1("VZEROSinglePhESpectrum",this,&AliVZERODigitizer::SinglePhESpectrum,0,20,0,"AliVZERODigitizer","SinglePhESpectrum");
  86
  87   // Now get the CTP L0->L1 delay
  88   AliCDBEntry *entry = AliCDBManager::Instance()->Get("GRP/CTP/CTPtiming");
  89   if (!entry) AliFatal("CTP timing parameters are not found in OCDB !");
  90   AliCTPTimeParams *ctpParams = (AliCTPTimeParams*)entry->GetObject();
  91   Float_t l1Delay = (Float_t)ctpParams->GetDelayL1L0()*25.0;
  92
  93   AliCDBEntry *entry2 = AliCDBManager::Instance()->Get("VZERO/Calib/TimeDelays");
  94   if (!entry2) AliFatal("VZERO time delays are not found in OCDB !");
  95   TH1F *delays = (TH1F*)entry2->GetObject();
  96
  97   for(Int_t i = 0 ; i < 64; ++i) {
  98
  99     for(Int_t j = 0; j < kNClocks; ++j) fAdc[i][j] = 0;
 100     fLeadingTime[i] = fTimeWidth[i] = 0;
 101
 102     fPmGain[i] = fCalibData->GetGain(i);
 103
 104     fAdcPedestal[i][0] = fCalibData->GetPedestal(i);
 105     fAdcSigma[i][0]    = fCalibData->GetSigma(i);
 106     fAdcPedestal[i][1] = fCalibData->GetPedestal(i+64);
 107     fAdcSigma[i][1]    = fCalibData->GetSigma(i+64);
 108
 109     Int_t board = AliVZEROCalibData::GetBoardNumber(i);
 110     fNBins[i] = TMath::Nint(((Float_t)(fCalibData->GetMatchWindow(board)+1)*25.0+
 111                              (Float_t)kMaxTDCWidth*fCalibData->GetWidthResolution(board))/
 112                             fCalibData->GetTimeResolution(board));
 113     fNBinsLT[i] = TMath::Nint(((Float_t)(fCalibData->GetMatchWindow(board)+1)*25.0)/
 114                               fCalibData->GetTimeResolution(board));
 115     fBinSize[i] = fCalibData->GetTimeResolution(board);
 116     fHptdcOffset[i] = (((Float_t)fCalibData->GetTriggerCountOffset(board)-
 117                         (Float_t)fCalibData->GetRollOver(board))*25.0+
 118                        fCalibData->GetTimeOffset(i)+
 119                        l1Delay+
 120                        delays->GetBinContent(i+1)+
 121                        kV0Offset);
 122
 123     fTime[i] = new Float_t[fNBins[i]];
 124     memset(fTime[i],0,fNBins[i]*sizeof(Float_t));
 125   }
 126
 127 }
 128
 129 //____________________________________________________________________________
 130   AliVZERODigitizer::AliVZERODigitizer(AliRunDigitizer* manager)
 131                     :AliDigitizer(manager),
 132                      fCalibData(GetCalibData()),
 133                      fPhotoCathodeEfficiency(0.18),
 134                      fNdigits(0),
 135                      fDigits(0),
 136                      fSignalShape(NULL),
 137                      fPMResponse(NULL),
 138                      fSinglePhESpectrum(NULL)
 139
 140 {
 141   // constructor
 142   // Initialize OCDB and containers used in the digitization
 143
 144   fSignalShape = new TF1("VZEROSignalShape",this,&AliVZERODigitizer::SignalShape,0,200,6,"AliVZERODigitizer","SignalShape");
 145   //  fSignalShape->SetParameters(0,1.57345e1,-4.25603e-1,2.9,6.40982,3.69339e-01);
 146   //  fSignalShape->SetParameters(1.34330e+00,1.13007e+02,-4.95705e-01,
 147   //                          3.68911e+00,1.01040e+00, 3.94675e-01);
 148   fSignalShape->SetParameters(-1.07335e+00,2.16002e+01,-1.26133e-01,
 149                               1.41619e+00,5.50334e-01,3.86111e-01);
 150   fPMResponse = new TF1("VZEROPMResponse",this,&AliVZERODigitizer::PMResponse,-kPMRespTime,2.*kPMRespTime,0,"AliVZERODigitizer","PMResponse");
 151   fSinglePhESpectrum = new TF1("VZEROSinglePhESpectrum",this,&AliVZERODigitizer::SinglePhESpectrum,0,20,0,"AliVZERODigitizer","SinglePhESpectrum");
 152
 153   // Now get the CTP L0->L1 delay
 154   AliCDBEntry *entry = AliCDBManager::Instance()->Get("GRP/CTP/CTPtiming");
 155   if (!entry) AliFatal("CTP timing parameters are not found in OCDB !");
 156   AliCTPTimeParams *ctpParams = (AliCTPTimeParams*)entry->GetObject();
 157   Float_t l1Delay = (Float_t)ctpParams->GetDelayL1L0()*25.0;
 158
 159   AliCDBEntry *entry2 = AliCDBManager::Instance()->Get("VZERO/Calib/TimeDelays");
 160   if (!entry2) AliFatal("VZERO time delays are not found in OCDB !");
 161   TH1F *delays = (TH1F*)entry2->GetObject();
 162
 163   for(Int_t i = 0 ; i < 64; ++i) {
 164
 165     for(Int_t j = 0; j < kNClocks; ++j) fAdc[i][j] = 0;
 166     fLeadingTime[i] = fTimeWidth[i] = 0;
 167
 168     fPmGain[i] = fCalibData->GetGain(i);
 169
 170     fAdcPedestal[i][0] = fCalibData->GetPedestal(i);
 171     fAdcSigma[i][0]    = fCalibData->GetSigma(i);
 172     fAdcPedestal[i][1] = fCalibData->GetPedestal(i+64);
 173     fAdcSigma[i][1]    = fCalibData->GetSigma(i+64);
 174
 175     Int_t board = AliVZEROCalibData::GetBoardNumber(i);
 176     fNBins[i] = TMath::Nint(((Float_t)(fCalibData->GetMatchWindow(board)+1)*25.0+
 177                              (Float_t)kMaxTDCWidth*fCalibData->GetWidthResolution(board))/
 178                             fCalibData->GetTimeResolution(board));
 179     fNBinsLT[i] = TMath::Nint(((Float_t)(fCalibData->GetMatchWindow(board)+1)*25.0)/
 180                               fCalibData->GetTimeResolution(board));
 181     fBinSize[i] = fCalibData->GetTimeResolution(board);
 182     fHptdcOffset[i] = (((Float_t)fCalibData->GetTriggerCountOffset(board)-
 183                         (Float_t)fCalibData->GetRollOver(board))*25.0+
 184                        fCalibData->GetTimeOffset(i)+
 185                        l1Delay+
 186                        delays->GetBinContent(i+1)+
 187                        kV0Offset);
 188
 189     fTime[i] = new Float_t[fNBins[i]];
 190     memset(fTime[i],0,fNBins[i]*sizeof(Float_t));
 191   }
 192 }
 193
 194 //____________________________________________________________________________
 195   AliVZERODigitizer::~AliVZERODigitizer()
 196 {
 197   // destructor
 198
 199   if (fDigits) {
 200     fDigits->Delete();
 201     delete fDigits;
 202     fDigits=0;
 203   }
 204
 205   if (fSignalShape) {
 206     delete fSignalShape;
 207     fSignalShape = NULL;
 208   }
 209   if (fPMResponse) {
 210     delete fPMResponse;
 211     fPMResponse = NULL;
 212   }
 213   if (fSinglePhESpectrum) {
 214     delete fSinglePhESpectrum;
 215     fSinglePhESpectrum = NULL;
 216   }
 217
 218   for(Int_t i = 0 ; i < 64; ++i) {
 219     if (fTime[i]) delete [] fTime[i];
 220   }
 221 }
 222
 223 //_____________________________________________________________________________
 224 Bool_t AliVZERODigitizer::Init()
 225 {
 226   // Initialises the digitizer
 227
 228   // Initialises the Digit array
 229   fDigits = new TClonesArray ("AliVZEROdigit", 1000);
 230
 231   return kTRUE;
 232 }
 233
 234 //____________________________________________________________________________
 235 void AliVZERODigitizer::Exec(Option_t* /*option*/)
 236 {
 237   // Creates digits from hits
 238   fNdigits     =    0;
 239
 240   for(Int_t i = 0 ; i < 64; ++i) {
 241     memset(fTime[i],0,fNBins[i]*sizeof(Float_t));
 242     for(Int_t j = 0; j < kNClocks; ++j) fAdc[i][j] = 0;
 243     fLeadingTime[i] = fTimeWidth[i] = 0;
 244   }
 245   Float_t integral = fPMResponse->Integral(-kPMRespTime,2.*kPMRespTime);
 246   Float_t meansPhE = fSinglePhESpectrum->Mean(0,20);
 247
 248   AliRunLoader* outRunLoader =  AliRunLoader::GetRunLoader(fManager->GetOutputFolderName());
 249   if (!outRunLoader) {
 250     Error("Exec", "Can not get output Run Loader");
 251     return;
 252   }
 253
 254   AliLoader* outLoader = outRunLoader->GetLoader("VZEROLoader");
 255
 256   if (!outLoader) {
 257     Error("Exec", "Can not get output VZERO Loader");
 258     return;
 259   }
 260
 261   const char* mode = "update";
 262   if(outRunLoader->GetEventNumber() == 0) mode = "recreate";
 263   outLoader->LoadDigits(mode);
 264
 265   if (!outLoader->TreeD()) outLoader->MakeTree("D");
 266   outLoader->MakeDigitsContainer();
 267   TTree* treeD  = outLoader->TreeD();
 268   Int_t bufsize = 16000;
 269   treeD->Branch("VZERODigit", &fDigits, bufsize);
 270
 271   for (Int_t iInput = 0; iInput < fManager->GetNinputs(); iInput++) {
 272      AliRunLoader* runLoader = AliRunLoader::GetRunLoader(fManager->GetInputFolderName(iInput));
 273      AliLoader* loader = runLoader->GetLoader("VZEROLoader");
 274      if (!loader) {
 275        Error("Exec", "Can not get VZERO Loader for input %d", iInput);
 276        continue;
 277          }
 278
 279      if (!runLoader->GetAliRun()) runLoader->LoadgAlice();
 280
 281      AliVZERO* vzero = (AliVZERO*) runLoader->GetAliRun()->GetDetector("VZERO");
 282      if (!vzero) {
 283        Error("Exec", "No VZERO detector for input %d", iInput);
 284        continue;
 285          }
 286
 287      loader->LoadHits();
 288      TTree* treeH = loader->TreeH();
 289      if (!treeH) {
 290        Error("Exec", "Cannot get TreeH for input %d", iInput);
 291        continue;
 292          }
 293
 294      TClonesArray* hits = vzero->Hits();
 295
 296      //     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};
 297      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};
 298 //  Now makes Digits from hits
 299      Int_t nTracks = (Int_t) treeH->GetEntries();
 300      for (Int_t iTrack = 0; iTrack < nTracks; iTrack++) {
 301          vzero->ResetHits();
 302          treeH->GetEvent(iTrack);
 303          Int_t nHits = hits->GetEntriesFast();
 304          for (Int_t iHit = 0; iHit < nHits; iHit++) {
 305            AliVZEROhit* hit = (AliVZEROhit *)hits->UncheckedAt(iHit);
 306            Int_t nPhot = hit->Nphot();
 307            Int_t cell  = hit->Cell();
 308            Int_t pmt = Cell2Pmt(cell);
 309            Float_t dt_scintillator = gRandom->Gaus(0,kIntTimeRes);
 310            Float_t t = dt_scintillator + 1e9*hit->Tof();
 311            if (pmt < 32) t += kV0CDelayCables;
 312            t += fHptdcOffset[pmt];
 313            Int_t nPhE;
 314            Float_t prob = lightYieldCorr[pmt]*fPhotoCathodeEfficiency; // Optical losses included!
 315            if (nPhot > 100)
 316              nPhE =gRandom->Gaus(prob*Float_t(nPhot)+0.5,
 317                                  sqrt(Float_t(nPhot)*prob*(1.-prob)));
 318            else
 319              nPhE = gRandom->Binomial(nPhot,prob);
 320            Float_t charge = TMath::Qe()*fPmGain[pmt]*fBinSize[pmt]/integral;
 321            for (Int_t iPhE = 0; iPhE < nPhE; ++iPhE) {
 322              Float_t tPhE = t + fSignalShape->GetRandom(0,fBinSize[pmt]*Float_t(fNBins[pmt]));
 323              Float_t gainVar = fSinglePhESpectrum->GetRandom(0,20)/meansPhE;
 324              Int_t firstBin = TMath::Max(0,(Int_t)((tPhE-kPMRespTime)/fBinSize[pmt]));
 325              Int_t lastBin = TMath::Min(fNBins[pmt]-1,(Int_t)((tPhE+2.*kPMRespTime)/fBinSize[pmt]));
 326              for(Int_t iBin = firstBin; iBin <= lastBin; ++iBin) {
 327                Float_t tempT = fBinSize[pmt]*(0.5+iBin)-tPhE;
 328                fTime[pmt][iBin] += gainVar*charge*fPMResponse->Eval(tempT);
 329              }
 330            }         // ph.e. loop
 331          }           // hit loop
 332      }               // track loop
 333      loader->UnloadHits();
 334   }                  // input loop
 335
 336   Float_t maximum = 0.9*fSignalShape->GetMaximum(0,200); // Not exact, one needs to do this on the convoluted
 337   Float_t integral2 = fSignalShape->Integral(0,200); // function. Anyway the effect is small <10% on the 2.5 ADC thr
 338   for (Int_t ipmt = 0; ipmt < 64; ++ipmt) {
 339     Float_t thr = fCalibData->GetDiscriThr(ipmt)*kChargePerADC*maximum*fBinSize[ipmt]/integral2;
 340     Bool_t ltFound = kFALSE, ttFound = kFALSE;
 341     for (Int_t iBin = 0; iBin < fNBins[ipmt]; ++iBin) {
 342       Float_t t = fBinSize[ipmt]*Float_t(iBin+0.5);
 343       if (fTime[ipmt][iBin] > thr) {
 344         if (!ltFound && (iBin < fNBinsLT[ipmt])) {
 345           ltFound = kTRUE;
 346           fLeadingTime[ipmt] = t;
 347         }
 348       }
 349       else {
 350         if (ltFound) {
 351           if (!ttFound) {
 352             ttFound = kTRUE;
 353             fTimeWidth[ipmt] = t - fLeadingTime[ipmt];
 354           }
 355         }
 356       }
 357       Float_t tadc = t - kADCTimeOffset;
 358       Int_t clock = kNClocks - Int_t(tadc/25.0) - 1;
 359       if (clock >= 0 && clock < kNClocks)
 360         fAdc[ipmt][clock] += fTime[ipmt][iBin]/kChargePerADC;
 361     }
 362     Int_t board = AliVZEROCalibData::GetBoardNumber(ipmt);
 363     if (ltFound && ttFound) {
 364       fTimeWidth[ipmt] = fCalibData->GetWidthResolution(board)*
 365         Float_t(Int_t(fTimeWidth[ipmt]/fCalibData->GetWidthResolution(board)));
 366       if (fTimeWidth[ipmt] < Float_t(kMinTDCWidth)*fCalibData->GetWidthResolution(board))
 367         fTimeWidth[ipmt] = Float_t(kMinTDCWidth)*fCalibData->GetWidthResolution(board);
 368       if (fTimeWidth[ipmt] > Float_t(kMaxTDCWidth)*fCalibData->GetWidthResolution(board))
 369         fTimeWidth[ipmt] = Float_t(kMaxTDCWidth)*fCalibData->GetWidthResolution(board);
 370     }
 371   }
 372
 373   Int_t evenOrOdd = gRandom->Integer(2);
 374   for (Int_t j=0; j<64; ++j){
 375     for (Int_t iClock = 0; iClock < kNClocks; ++iClock) {
 376       Int_t integrator = (iClock + evenOrOdd) % 2;
 377       fAdc[j][iClock]  += gRandom->Gaus(fAdcPedestal[j][integrator], fAdcSigma[j][integrator]);
 378     }
 379   }
 380
 381   // Now add digits to the digit Tree
 382
 383   for (Int_t i=0; i<64; i++) {
 384     //    printf(" cell %d adc ",i);
 385     //    for (Int_t j = 0; j < kNClocks; ++j)
 386     //      printf("%d ", Int_t(fAdc[i][j]));
 387     //    printf("\n");
 388     Float_t totADC = 0;
 389     for (Int_t j = 8; j <= 11; ++j) {
 390       Int_t tempadc = Int_t(fAdc[i][j]);
 391       if (tempadc > 1023) tempadc = 1023;
 392       Int_t integrator = (j + evenOrOdd) % 2;
 393       if ((Float_t(tempadc) - fAdcPedestal[i][integrator]) > (2.*fAdcSigma[i][integrator]))
 394         totADC += (Float_t(tempadc) - fAdcPedestal[i][integrator]);
 395     }
 396     totADC += fAdcPedestal[i][(10+evenOrOdd)%2];
 397     AddDigit(i, totADC, fLeadingTime[i], fTimeWidth[i], Bool_t((10+evenOrOdd)%2));
 398   }
 399
 400   treeD->Fill();
 401   outLoader->WriteDigits("OVERWRITE");
 402   outLoader->UnloadDigits();
 403   ResetDigit();
 404 }
 405
 406 //____________________________________________________________________________
 407 void AliVZERODigitizer::AddDigit(Int_t PMnumber, Float_t adc, Float_t time, Float_t width, Bool_t integrator)
 408  {
 409
 410 // Adds Digit
 411
 412   TClonesArray &ldigits = *fDigits;
 413
 414   new(ldigits[fNdigits++]) AliVZEROdigit(PMnumber,adc,time,width,kFALSE,kFALSE,integrator);
 415
 416 }
 417 //____________________________________________________________________________
 418 void AliVZERODigitizer::ResetDigit()
 419 {
 420
 421 // Clears Digits
 422
 423   fNdigits = 0;
 424   if (fDigits) fDigits->Delete();
 425 }
 426
 427 //____________________________________________________________________________
 428 AliVZEROCalibData* AliVZERODigitizer::GetCalibData() const
 429
 430 {
 431   AliCDBManager *man = AliCDBManager::Instance();
 432
 433   AliCDBEntry *entry=0;
 434
 435   entry = man->Get("VZERO/Calib/Data");
 436
 437 //   if(!entry){
 438 //     AliWarning("Load of calibration data from default storage failed!");
 439 //     AliWarning("Calibration data will be loaded from local storage ($ALICE_ROOT)");
 440 //     Int_t runNumber = man->GetRun();
 441 //     entry = man->GetStorage("local://$ALICE_ROOT/OCDB")
 442 //       ->Get("VZERO/Calib/Data",runNumber);
 443 //
 444 //   }
 445
 446   // Retrieval of data in directory VZERO/Calib/Data:
 447
 448
 449   AliVZEROCalibData *calibdata = 0;
 450
 451   if (entry) calibdata = (AliVZEROCalibData*) entry->GetObject();
 452   if (!calibdata)  AliFatal("No calibration data from calibration database !");
 453
 454   return calibdata;
 455
 456 }
 457
 458 double AliVZERODigitizer::SignalShape(double *x, double *par)
 459 {
 460   // this function simulates the time
 461   // of arrival of the photons at the
 462   // photocathode
 463   Double_t xx = x[0];
 464   if (xx <= par[0]) return 0;
 465   Double_t a = 1./TMath::Power((xx-par[0])/par[1],1./par[2]);
 466   if (xx <= par[3]) return a;
 467   Double_t b = 1./TMath::Power((xx-par[3])/par[4],1./par[5]);
 468   Double_t f = a*b/(a+b);
 469   AliDebug(100,Form("x=%f func=%f",xx,f));
 470   return f;
 471 }
 472
 473 double AliVZERODigitizer::PMResponse(double *x, double * /* par */)
 474 {
 475   // this function describes the
 476   // PM time response to a single
 477   // photoelectron
 478   Double_t xx = x[0]+kPMRespTime;
 479   return xx*xx*TMath::Exp(-xx*xx/(kPMRespTime*kPMRespTime));
 480 }
 481
 482 double AliVZERODigitizer::SinglePhESpectrum(double *x, double * /* par */)
 483 {
 484   // this function describes the
 485   // PM amplitude response to a single
 486   // photoelectron
 487   Double_t xx = x[0];
 488   if (xx < 0) return 0;
 489   return (TMath::Poisson(xx,kPMNbOfSecElec)+kPMTransparency*TMath::Poisson(xx,1.0));
 490 }
 491
 492 Int_t AliVZERODigitizer::Cell2Pmt(Int_t cell) const
 493 {
 494   // The method maps the scintillator
 495   // indexes to the PM ones
 496   if (cell < 0 || cell >= 80) {
 497     AliError(Form("Wrong VZERO cell index %d",cell));
 498     return -1;
 499   }
 500   if (cell < 16) return cell;
 501   if (cell < 48) return 8 + cell/2;
 502   return cell - 16;
 503 }