]> git.uio.no Git - u/mrichter/AliRoot.git/blobdiff - TRD/AliTRDdigitizer.cxx
undo precedent change
[u/mrichter/AliRoot.git] / TRD / AliTRDdigitizer.cxx
index 3fd273cbed421cc3659ade47166b1eebf708cb18..d4742ce915faf78fb99d5e457889fc0f6074b7a1 100644 (file)
 
 /*
 $Log$
+Revision 1.29  2001/11/14 19:44:25  hristov
+Numeric const casted (Alpha)
+
+Revision 1.28  2001/11/14 16:35:58  cblume
+Inherits now from AliDetector
+
+Revision 1.27  2001/11/14 10:50:45  cblume
+Changes in digits IO. Add merging of summable digits
+
+Revision 1.26  2001/11/06 17:19:41  cblume
+Add detailed geometry and simple simulator
+
+Revision 1.25  2001/06/27 09:54:44  cblume
+Moved fField initialization to InitDetector()
+
+Revision 1.24  2001/05/21 16:45:47  hristov
+Last minute changes (C.Blume)
+
+Revision 1.23  2001/05/07 08:04:48  cblume
+New TRF and PRF. Speedup of the code. Digits from amplification region included
+
+Revision 1.22  2001/03/30 14:40:14  cblume
+Update of the digitization parameter
+
+Revision 1.21  2001/03/13 09:30:35  cblume
+Update of digitization. Moved digit branch definition to AliTRD
+
 Revision 1.20  2001/02/25 20:19:00  hristov
 Minor correction: loop variable declared only once for HP, Sun
 
@@ -101,12 +128,14 @@ Add new TRD classes
 ///////////////////////////////////////////////////////////////////////////////
 //                                                                           //
 //  Creates and handles digits from TRD hits                                 //
+//  Author: C. Blume (C.Blume@gsi.de)                                        //
 //                                                                           //
 //  The following effects are included:                                      //
 //      - Diffusion                                                          //
 //      - ExB effects                                                        //
 //      - Gas gain including fluctuations                                    //
 //      - Pad-response (simple Gaussian approximation)                       //
+//      - Time-response                                                      //
 //      - Electronics noise                                                  //
 //      - Electronics gain                                                   //
 //      - Digitization                                                       //
@@ -114,8 +143,11 @@ Add new TRD classes
 //  The corresponding parameter can be adjusted via the various              //
 //  Set-functions. If these parameters are not explicitly set, default       //
 //  values are used (see Init-function).                                     //
-//  To produce digits from a root-file with TRD-hits use the                 //
-//  slowDigitsCreate.C macro.                                                //
+//  As an example on how to use this class to produce digits from hits       //
+//  have a look at the macro hits2digits.C                                   //
+//  The production of summable digits is demonstrated in hits2sdigits.C      //
+//  and the subsequent conversion of the s-digits into normal digits is      //
+//  explained in sdigits2digits.C.                                           //
 //                                                                           //
 ///////////////////////////////////////////////////////////////////////////////
 
@@ -128,8 +160,12 @@ Add new TRD classes
 #include <TTree.h>
 #include <TFile.h>
 #include <TF1.h>
+#include <TList.h>
+#include <TTask.h>
 
 #include "AliRun.h"
+#include "AliMagF.h"
+#include "AliRunDigitizer.h"
 
 #include "AliTRD.h"
 #include "AliTRDhit.h"
@@ -143,82 +179,114 @@ Add new TRD classes
 ClassImp(AliTRDdigitizer)
 
 //_____________________________________________________________________________
-AliTRDdigitizer::AliTRDdigitizer():TNamed()
+AliTRDdigitizer::AliTRDdigitizer()
 {
   //
   // AliTRDdigitizer default constructor
   //
 
-  fInputFile      = NULL;
-  fDigits         = NULL;
-  fTRD            = NULL;
-  fGeo            = NULL;
-  fPRF            = NULL;
-  fPRFsmp         = NULL;
-  fTRF            = NULL;
-  fTRFint         = NULL;
-
-  fEvent          = 0;
-  fGasGain        = 0.0;
-  fNoise          = 0.0;
-  fChipGain       = 0.0;
-  fSinRange       = 0.0;
-  fSoutRange      = 0.0;
-  fADCoutRange    = 0.0;
-  fADCinRange     = 0.0;
-  fADCthreshold   = 0;
-  fDiffusionOn    = 0;
-  fDiffusionT     = 0.0;
-  fDiffusionL     = 0.0;
-  fElAttachOn     = 0;
-  fElAttachProp   = 0.0;
-  fExBOn          = 0;
-  fOmegaTau       = 0.0;
-  fPRFOn          = 0;
-  fTRFOn          = 0;
-  fDriftVelocity  = 0.0;
-  fPadCoupling    = 0.0;
-  fTimeCoupling   = 0.0;
-  fTimeBinWidth   = 0.0;
-
-  fPRFbin         = 0;
-  fPRFlo          = 0.0;
-  fPRFhi          = 0.0;
-  fPRFwid         = 0.0;
-  fPRFpad         = 0;
-  fTRFbin         = 0;
-  fTRFlo          = 0.0;
-  fTRFhi          = 0.0;
-  fTRFwid         = 0.0;
-
-  fCompress       = kTRUE;
-  fVerbose        = 1;
-  fSDigits        = kFALSE;
+  fInputFile          = NULL;
+  fDigitsManager      = NULL;
+  fSDigitsManagerList = NULL;
+  fSDigitsManager     = NULL;
+  fTRD                = NULL;
+  fGeo                = NULL;
+  fPRFsmp             = NULL;
+  fTRFsmp             = NULL;
+
+  fEvent              = 0;
+  fGasGain            = 0.0;
+  fNoise              = 0.0;
+  fChipGain           = 0.0;
+  fADCoutRange        = 0.0;
+  fADCinRange         = 0.0;
+  fADCthreshold       = 0;
+  fDiffusionOn        = 0;
+  fDiffusionT         = 0.0;
+  fDiffusionL         = 0.0;
+  fElAttachOn         = 0;
+  fElAttachProp       = 0.0;
+  fExBOn              = 0;
+  fOmegaTau           = 0.0;
+  fPRFOn              = 0;
+  fTRFOn              = 0;
+  fDriftVelocity      = 0.0;
+  fPadCoupling        = 0.0;
+  fTimeCoupling       = 0.0;
+  fTimeBinWidth       = 0.0;
+  fField              = 0.0;
+
+  fPRFbin             = 0;
+  fPRFlo              = 0.0;
+  fPRFhi              = 0.0;
+  fPRFwid             = 0.0;
+  fPRFpad             = 0;
+  fTRFbin             = 0;
+  fTRFlo              = 0.0;
+  fTRFhi              = 0.0;
+  fTRFwid             = 0.0;
+
+  fCompress           = kTRUE;
+  fVerbose            = 0;
+  fSDigits            = kFALSE;
+  fSDigitsScale       = 0.0;
 
 }
 
 //_____________________________________________________________________________
 AliTRDdigitizer::AliTRDdigitizer(const Text_t *name, const Text_t *title)
-                :TNamed(name,title)
+                :AliDigitizer(name,title)
 {
   //
-  // AliTRDdigitizer default constructor
+  // AliTRDdigitizer constructor
+  //
+
+  fInputFile          = NULL;
+
+  fDigitsManager      = NULL;
+  fSDigitsManager     = NULL;
+  fSDigitsManagerList = NULL;
+
+  fTRD                = NULL;
+  fGeo                = NULL;
+  fPRFsmp             = NULL;
+  fTRFsmp             = NULL;
+
+  fEvent              = 0;
+
+  fCompress           = kTRUE;
+  fVerbose            = 0;
+  fSDigits            = kFALSE;
+
+  Init();
+
+}
+
+//_____________________________________________________________________________
+AliTRDdigitizer::AliTRDdigitizer(AliRunDigitizer *manager
+                                , const Text_t *name, const Text_t *title)
+                :AliDigitizer(manager,name,title)
+{
   //
+  // AliTRDdigitizer constructor
+  //
+
+  fInputFile          = NULL;
 
-  fInputFile     = NULL;
-  fDigits        = NULL;
-  fTRD           = NULL;
-  fGeo           = NULL;
-  fPRF           = NULL;
-  fPRFsmp        = NULL;
-  fTRF           = NULL;
-  fTRFint        = NULL;
+  fDigitsManager      = NULL;
+  fSDigitsManager     = NULL;
+  fSDigitsManagerList = NULL;
 
-  fEvent         = 0;
+  fTRD                = NULL;
+  fGeo                = NULL;
+  fPRFsmp             = NULL;
+  fTRFsmp             = NULL;
 
-  fCompress      = kTRUE;
-  fVerbose       = 1;
-  fSDigits       = kFALSE;
+  fEvent              = 0;
+
+  fCompress           = kTRUE;
+  fVerbose            = 0;
+  fSDigits            = kFALSE;
 
   Init();
 
@@ -245,14 +313,34 @@ AliTRDdigitizer::~AliTRDdigitizer()
   if (fInputFile) {
     fInputFile->Close();
     delete fInputFile;
+    fInputFile = NULL;
+  }
+
+  if (fDigitsManager) {
+    delete fDigitsManager;
+    fDigitsManager = NULL;
+  }
+
+  if (fSDigitsManager) {
+    delete fSDigitsManager;
+    fSDigitsManager = NULL;
+  }
+
+  if (fSDigitsManagerList) {
+    fSDigitsManagerList->Delete();
+    delete fSDigitsManagerList;
+    fSDigitsManagerList = NULL;
   }
 
-  if (fDigits) {
-    delete fDigits;
+  if (fTRFsmp) {
+    delete fTRFsmp;
+    fTRFsmp = NULL;
   }
 
-  if (fPRF) delete fPRF;
-  if (fTRF) delete fTRF;
+  if (fPRFsmp) {
+    delete fPRFsmp;
+    fPRFsmp = NULL;
+  }
 
 }
 
@@ -277,61 +365,60 @@ void AliTRDdigitizer::Copy(TObject &d)
 
   Int_t iBin;
 
-  ((AliTRDdigitizer &) d).fInputFile      = NULL;
-  ((AliTRDdigitizer &) d).fDigits         = NULL;
-  ((AliTRDdigitizer &) d).fTRD            = NULL;
-  ((AliTRDdigitizer &) d).fGeo            = NULL;
-
-  ((AliTRDdigitizer &) d).fEvent          = 0;
-
-  ((AliTRDdigitizer &) d).fGasGain        = fGasGain;
-  ((AliTRDdigitizer &) d).fNoise          = fNoise;
-  ((AliTRDdigitizer &) d).fChipGain       = fChipGain;
-  ((AliTRDdigitizer &) d).fSoutRange      = fSoutRange;
-  ((AliTRDdigitizer &) d).fSinRange       = fSinRange;
-  ((AliTRDdigitizer &) d).fADCoutRange    = fADCoutRange;
-  ((AliTRDdigitizer &) d).fADCinRange     = fADCinRange;
-  ((AliTRDdigitizer &) d).fADCthreshold   = fADCthreshold;
-  ((AliTRDdigitizer &) d).fDiffusionOn    = fDiffusionOn; 
-  ((AliTRDdigitizer &) d).fDiffusionT     = fDiffusionT;
-  ((AliTRDdigitizer &) d).fDiffusionL     = fDiffusionL;
-  ((AliTRDdigitizer &) d).fElAttachOn     = fElAttachOn;
-  ((AliTRDdigitizer &) d).fElAttachProp   = fElAttachProp;
-  ((AliTRDdigitizer &) d).fExBOn          = fExBOn;
-  ((AliTRDdigitizer &) d).fOmegaTau       = fOmegaTau;
-  ((AliTRDdigitizer &) d).fLorentzFactor  = fLorentzFactor;
-  ((AliTRDdigitizer &) d).fDriftVelocity  = fDriftVelocity;
-  ((AliTRDdigitizer &) d).fPadCoupling    = fPadCoupling;
-  ((AliTRDdigitizer &) d).fTimeCoupling   = fTimeCoupling;
-  ((AliTRDdigitizer &) d).fTimeBinWidth   = fTimeBinWidth;
-  ((AliTRDdigitizer &) d).fPRFOn          = fPRFOn;
-  ((AliTRDdigitizer &) d).fTRFOn          = fTRFOn;
-
-  ((AliTRDdigitizer &) d).fCompress       = fCompress;
-  ((AliTRDdigitizer &) d).fVerbose        = fVerbose;
-  ((AliTRDdigitizer &) d).fSDigits        = fSDigits;
-
-  fPRF->Copy(*((AliTRDdigitizer &) d).fPRF);
-  fTRF->Copy(*((AliTRDdigitizer &) d).fTRF);
-
-  ((AliTRDdigitizer &) d).fPRFbin         = fPRFbin;
-  ((AliTRDdigitizer &) d).fPRFlo          = fPRFlo;
-  ((AliTRDdigitizer &) d).fPRFhi          = fPRFhi;
-  ((AliTRDdigitizer &) d).fPRFwid         = fPRFwid;
-  ((AliTRDdigitizer &) d).fPRFpad         = fPRFpad;
+  ((AliTRDdigitizer &) d).fInputFile          = NULL;
+  ((AliTRDdigitizer &) d).fSDigitsManagerList = NULL;
+  ((AliTRDdigitizer &) d).fSDigitsManager     = NULL;
+  ((AliTRDdigitizer &) d).fDigitsManager      = NULL;
+  ((AliTRDdigitizer &) d).fTRD                = NULL;
+  ((AliTRDdigitizer &) d).fGeo                = NULL;
+
+  ((AliTRDdigitizer &) d).fEvent              = 0;
+
+  ((AliTRDdigitizer &) d).fGasGain            = fGasGain;
+  ((AliTRDdigitizer &) d).fNoise              = fNoise;
+  ((AliTRDdigitizer &) d).fChipGain           = fChipGain;
+  ((AliTRDdigitizer &) d).fADCoutRange        = fADCoutRange;
+  ((AliTRDdigitizer &) d).fADCinRange         = fADCinRange;
+  ((AliTRDdigitizer &) d).fADCthreshold       = fADCthreshold;
+  ((AliTRDdigitizer &) d).fDiffusionOn        = fDiffusionOn; 
+  ((AliTRDdigitizer &) d).fDiffusionT         = fDiffusionT;
+  ((AliTRDdigitizer &) d).fDiffusionL         = fDiffusionL;
+  ((AliTRDdigitizer &) d).fElAttachOn         = fElAttachOn;
+  ((AliTRDdigitizer &) d).fElAttachProp       = fElAttachProp;
+  ((AliTRDdigitizer &) d).fExBOn              = fExBOn;
+  ((AliTRDdigitizer &) d).fOmegaTau           = fOmegaTau;
+  ((AliTRDdigitizer &) d).fLorentzFactor      = fLorentzFactor;
+  ((AliTRDdigitizer &) d).fDriftVelocity      = fDriftVelocity;
+  ((AliTRDdigitizer &) d).fPadCoupling        = fPadCoupling;
+  ((AliTRDdigitizer &) d).fTimeCoupling       = fTimeCoupling;
+  ((AliTRDdigitizer &) d).fTimeBinWidth       = fTimeBinWidth;
+  ((AliTRDdigitizer &) d).fField              = fField;
+  ((AliTRDdigitizer &) d).fPRFOn              = fPRFOn;
+  ((AliTRDdigitizer &) d).fTRFOn              = fTRFOn;
+
+  ((AliTRDdigitizer &) d).fCompress           = fCompress;
+  ((AliTRDdigitizer &) d).fVerbose            = fVerbose;
+  ((AliTRDdigitizer &) d).fSDigits            = fSDigits;
+  ((AliTRDdigitizer &) d).fSDigitsScale       = fSDigitsScale;
+
+  ((AliTRDdigitizer &) d).fPRFbin             = fPRFbin;
+  ((AliTRDdigitizer &) d).fPRFlo              = fPRFlo;
+  ((AliTRDdigitizer &) d).fPRFhi              = fPRFhi;
+  ((AliTRDdigitizer &) d).fPRFwid             = fPRFwid;
+  ((AliTRDdigitizer &) d).fPRFpad             = fPRFpad;
   if (((AliTRDdigitizer &) d).fPRFsmp) delete ((AliTRDdigitizer &) d).fPRFsmp;
   ((AliTRDdigitizer &) d).fPRFsmp = new Float_t[fPRFbin];
   for (iBin = 0; iBin < fPRFbin; iBin++) {
     ((AliTRDdigitizer &) d).fPRFsmp[iBin] = fPRFsmp[iBin];
   }                                                                             
-  ((AliTRDdigitizer &) d).fTRFbin         = fTRFbin;
-  ((AliTRDdigitizer &) d).fTRFlo          = fTRFlo;
-  ((AliTRDdigitizer &) d).fTRFhi          = fTRFhi;
-  ((AliTRDdigitizer &) d).fTRFwid         = fTRFwid;
-  if (((AliTRDdigitizer &) d).fTRFint) delete ((AliTRDdigitizer &) d).fTRFint;
-  ((AliTRDdigitizer &) d).fTRFint = new Float_t[fTRFbin];
+  ((AliTRDdigitizer &) d).fTRFbin             = fTRFbin;
+  ((AliTRDdigitizer &) d).fTRFlo              = fTRFlo;
+  ((AliTRDdigitizer &) d).fTRFhi              = fTRFhi;
+  ((AliTRDdigitizer &) d).fTRFwid             = fTRFwid;
+  if (((AliTRDdigitizer &) d).fTRFsmp) delete ((AliTRDdigitizer &) d).fTRFsmp;
+  ((AliTRDdigitizer &) d).fTRFsmp = new Float_t[fTRFbin];
   for (iBin = 0; iBin < fTRFbin; iBin++) {
-    ((AliTRDdigitizer &) d).fTRFint[iBin] = fTRFint[iBin];
+    ((AliTRDdigitizer &) d).fTRFsmp[iBin] = fTRFsmp[iBin];
   }                                      
                                        
 }
@@ -408,7 +495,7 @@ Float_t AliTRDdigitizer::TimeResponse(Float_t time)
 
   Int_t iBin = ((Int_t) ((time - fTRFlo) / fTRFwid)); 
   if ((iBin >= 0) && (iBin < fTRFbin)) {
-    return fTRFint[iBin];
+    return fTRFsmp[iBin];
   }
   else {
     return 0.0;
@@ -417,55 +504,41 @@ Float_t AliTRDdigitizer::TimeResponse(Float_t time)
 }
 
 //_____________________________________________________________________________
-void AliTRDdigitizer::Init()
+Bool_t AliTRDdigitizer::Init()
 {
   //
   // Initializes the digitization procedure with standard values
   //
 
-  // Get the detector geometry
-  InitDetector();
-
   // The default parameter for the digitization
-  fGasGain        = 2.0E3;
-  fChipGain       = 20.;
+  fGasGain        = 2800.;
+  fChipGain       = 6.1;
   fNoise          = 1000.;
   fADCoutRange    = 1023.;          // 10-bit ADC
-  fADCinRange     = 2000.;          // 2V input range
+  fADCinRange     = 1000.;          // 1V input range
   fADCthreshold   = 1;
 
   // For the summable digits
-  fSinRange       = 1000000.;
-  fSoutRange      = 1000000.;
+  fSDigitsScale   = 100.;
+
+  // The drift velocity (cm / mus)
+  fDriftVelocity  = 1.5;
 
-  // Transverse and longitudinal diffusion coefficients (Xe/Isobutane)
+  // Diffusion on
   fDiffusionOn    = 1;
-  fDiffusionT     = 0.060;
-  fDiffusionL     = 0.017;
+
+  // E x B effects
+  fExBOn          = 0;
 
   // Propability for electron attachment
   fElAttachOn     = 0;
   fElAttachProp   = 0.0;
 
-  // E x B effects
-  fExBOn          = 0;
-  // omega * tau.= arctan(Lorentz-angle)
-  fOmegaTau       = 0.19438031;
-
   // The pad response function
   fPRFOn          =  1;
-  fPRFlo          = -3.0;
-  fPRFhi          =  3.0;
-  fPRFbin         = 120;
-  fPRFwid         = (fPRFhi - fPRFlo) / ((Float_t) fPRFbin);
-  fPRFpad         = ((Int_t) (1.0 / fPRFwid));
-  fPRF            = new TF1("PRF","[0]*([1]+exp(-x*x/(2.0*[2])))",fPRFlo,fPRFhi);
-  fPRF->SetParameter(0, 0.8872);
-  fPRF->SetParameter(1,-0.00573);
-  fPRF->SetParameter(2, 0.454 * 0.454);
 
-  // The drift velocity (cm / mus)
-  fDriftVelocity  = 2.0;
+  // The time response function
+  fTRFOn          =  1;
 
   // The pad coupling factor (same number as for the TPC)
   fPadCoupling    = 0.5;
@@ -473,34 +546,41 @@ void AliTRDdigitizer::Init()
   // The time coupling factor (same number as for the TPC)
   fTimeCoupling   = 0.4;
 
-  ReInit();
+  return kTRUE;
 
 }
 
 //_____________________________________________________________________________
-void AliTRDdigitizer::ReInit()
+Bool_t AliTRDdigitizer::ReInit()
 {
   //
-  // Re-initializes the digitization procedure after a change in the parameter
+  // Reinitializes the digitization procedure after a change in the parameter
   //
 
+  if (!fGeo) {
+    printf("AliTRDdigitizer::ReInit -- ");
+    printf("No geometry defined. Run InitDetector() first\n");
+    return kFALSE;
+  }
+
   // Calculate the time bin width in ns
   fTimeBinWidth   = fGeo->GetTimeBinSize() / fDriftVelocity * 1000.0;
 
-  // The time response function (in ns)
-  // The FWHM of the TRF is automatically set equal to the time bin width
-  fTRFOn          =  1;
-  Float_t loTRF   = -2.0 * fTimeBinWidth;
-  Float_t hiTRF   = 10.0 * fTimeBinWidth;
-  fTRF            = new TF1("TRF",TRFlandau,loTRF,hiTRF,3);
-  //fTRF->SetParameter(0,  1.0 / 24.24249);
-  fTRF->SetParameter(0,  5.56);
-  fTRF->SetParameter(1,  0.0);
-  fTRF->SetParameter(2,  0.25 * fTimeBinWidth);
-  fTRFbin         = 120;
-  fTRFlo          = loTRF * fDriftVelocity / 1000.0;
-  fTRFhi          = hiTRF * fDriftVelocity / 1000.0;
-  fTRFwid         = (fTRFhi - fTRFlo) / ((Float_t) fTRFbin);
+  // The range and the binwidth for the sampled TRF 
+  fTRFbin = 100;
+  // Start 0.2 mus before the signal
+  fTRFlo  = -0.2 * fDriftVelocity;
+  // End the maximum driftlength after the signal 
+  fTRFhi  = AliTRDgeometry::DrThick() 
+          + fGeo->GetTimeAfter() * fGeo->GetTimeBinSize();
+  fTRFwid = (fTRFhi - fTRFlo) / ((Float_t) fTRFbin);
+
+  // Transverse and longitudinal diffusion coefficients (Xe/CO2)
+  fDiffusionT     = GetDiffusionT(fDriftVelocity,fField);
+  fDiffusionL     = GetDiffusionL(fDriftVelocity,fField);
+
+  // omega * tau.= tan(Lorentz-angle)
+  fOmegaTau       = GetOmegaTau(fDriftVelocity,fField);
 
   // The Lorentz factor
   if (fExBOn) {
@@ -510,6 +590,8 @@ void AliTRDdigitizer::ReInit()
     fLorentzFactor = 1.0;
   }
 
+  return kTRUE;
+
 }
 
 //_____________________________________________________________________________
@@ -517,16 +599,142 @@ void AliTRDdigitizer::SampleTRF()
 {
   //
   // Samples the time response function
+  // It is defined according to Vasiles simulation of the preamp shaper
+  // output and includes the effect of the ion tail (based on Tariqs 
+  // Garfield simulation) and a shaping time of 125 ns FWHM
   //
 
-  if (fTRFint) delete fTRFint;
-  fTRFint = new Float_t[fTRFbin];
-  Float_t loTRF    = fTRFlo / fDriftVelocity * 1000.0;
-  Float_t hiTRF    = fTRFhi / fDriftVelocity * 1000.0;
+  Int_t   ipos1;
+  Int_t   ipos2;
+  Float_t diff;
+
+  const Int_t kNpasa = 200;
+  Float_t time[kNpasa]   = {  -0.280000, -0.270000, -0.260000, -0.250000
+                            , -0.240000, -0.230000, -0.220000, -0.210000
+                            , -0.200000, -0.190000, -0.180000, -0.170000
+                            , -0.160000, -0.150000, -0.140000, -0.130000
+                            , -0.120000, -0.110000, -0.100000, -0.090000
+                            , -0.080000, -0.070000, -0.060000, -0.050000
+                            , -0.040000, -0.030000, -0.020000, -0.010000
+                            , -0.000000,  0.010000,  0.020000,  0.030000
+                            ,  0.040000,  0.050000,  0.060000,  0.070000
+                            ,  0.080000,  0.090000,  0.100000,  0.110000
+                            ,  0.120000,  0.130000,  0.140000,  0.150000
+                            ,  0.160000,  0.170000,  0.180000,  0.190000
+                            ,  0.200000,  0.210000,  0.220000,  0.230000
+                            ,  0.240000,  0.250000,  0.260000,  0.270000
+                            ,  0.280000,  0.290000,  0.300000,  0.310000
+                            ,  0.320000,  0.330000,  0.340000,  0.350000
+                            ,  0.360000,  0.370000,  0.380000,  0.390000
+                            ,  0.400000,  0.410000,  0.420000,  0.430000
+                            ,  0.440000,  0.450000,  0.460000,  0.470000
+                            ,  0.480000,  0.490000,  0.500000,  0.510000
+                            ,  0.520000,  0.530000,  0.540000,  0.550000
+                            ,  0.560000,  0.570000,  0.580000,  0.590000
+                            ,  0.600000,  0.610000,  0.620000,  0.630000
+                            ,  0.640000,  0.650000,  0.660000,  0.670000
+                            ,  0.680000,  0.690000,  0.700000,  0.710000
+                            ,  0.720000,  0.730000,  0.740000,  0.750000
+                            ,  0.760000,  0.770000,  0.780000,  0.790000
+                            ,  0.800000,  0.810000,  0.820000,  0.830000
+                            ,  0.840000,  0.850000,  0.860000,  0.870000
+                            ,  0.880000,  0.890000,  0.900000,  0.910000
+                            ,  0.920000,  0.930000,  0.940000,  0.950000
+                            ,  0.960000,  0.970000,  0.980000,  0.990000
+                            ,  1.000000,  1.010000,  1.020000,  1.030000
+                            ,  1.040000,  1.050000,  1.060000,  1.070000
+                            ,  1.080000,  1.090000,  1.100000,  1.110000
+                            ,  1.120000,  1.130000,  1.140000,  1.150000
+                            ,  1.160000,  1.170000,  1.180000,  1.190000
+                            ,  1.200000,  1.210000,  1.220000,  1.230000
+                            ,  1.240000,  1.250000,  1.260000,  1.270000
+                            ,  1.280000,  1.290000,  1.300000,  1.310000
+                            ,  1.320000,  1.330000,  1.340000,  1.350000
+                            ,  1.360000,  1.370000,  1.380000,  1.390000
+                            ,  1.400000,  1.410000,  1.420000,  1.430000
+                            ,  1.440000,  1.450000,  1.460000,  1.470000
+                            ,  1.480000,  1.490000,  1.500000,  1.510000
+                            ,  1.520000,  1.530000,  1.540000,  1.550000
+                            ,  1.560000,  1.570000,  1.580000,  1.590000
+                            ,  1.600000,  1.610000,  1.620000,  1.630000
+                            ,  1.640000,  1.650000,  1.660000,  1.670000
+                           ,  1.680000,  1.690000,  1.700000,  1.710000 };
+
+  Float_t signal[kNpasa] = {   0.000000,  0.000000,  0.000000,  0.000000 
+                            ,  0.000000,  0.000000,  0.000000,  0.000000
+                            ,  0.000000,  0.000000,  0.000000,  0.000000
+                            ,  0.000000,  0.000000,  0.000000,  0.000098
+                            ,  0.003071,  0.020056,  0.066053,  0.148346
+                            ,  0.263120,  0.398496,  0.540226,  0.674436
+                            ,  0.790977,  0.883083,  0.947744,  0.985714
+                            ,  0.999248,  0.992105,  0.967669,  0.930827
+                            ,  0.884586,  0.833083,  0.778571,  0.723684
+                            ,  0.669173,  0.617293,  0.567669,  0.521805
+                            ,  0.479699,  0.440977,  0.405639,  0.373985
+                            ,  0.345526,  0.320038,  0.297256,  0.276917
+                            ,  0.258797,  0.242632,  0.228195,  0.215301
+                            ,  0.203759,  0.193383,  0.184023,  0.175564
+                            ,  0.167895,  0.160940,  0.154549,  0.148722
+                            ,  0.143308,  0.138346,  0.133722,  0.129398
+                            ,  0.125376,  0.121617,  0.118045,  0.114699
+                            ,  0.111541,  0.108571,  0.105714,  0.103008
+                            ,  0.100414,  0.097970,  0.095602,  0.093346
+                            ,  0.091165,  0.089060,  0.087068,  0.085150
+                            ,  0.083308,  0.081541,  0.079812,  0.078158
+                            ,  0.076541,  0.075000,  0.073496,  0.072068
+                            ,  0.070677,  0.069286,  0.068008,  0.066729
+                            ,  0.065489,  0.064286,  0.063120,  0.061992
+                            ,  0.060902,  0.059850,  0.058797,  0.057820
+                            ,  0.056842,  0.055902,  0.054962,  0.054060
+                            ,  0.053158,  0.052293,  0.051466,  0.050639
+                            ,  0.049850,  0.049060,  0.048308,  0.047556
+                            ,  0.046842,  0.046128,  0.045451,  0.044774
+                            ,  0.044098,  0.043459,  0.042820,  0.042218
+                            ,  0.041617,  0.041015,  0.040451,  0.039887
+                            ,  0.039323,  0.038797,  0.038271,  0.037744
+                            ,  0.037237,  0.036744,  0.036259,  0.035786
+                            ,  0.035323,  0.034872,  0.034429,  0.033996
+                            ,  0.033575,  0.033162,  0.032756,  0.032361
+                            ,  0.031974,  0.031594,  0.031222,  0.030857
+                            ,  0.030496,  0.030143,  0.029793,  0.029451
+                            ,  0.029109,  0.028774,  0.028444,  0.028113
+                            ,  0.027793,  0.027477,  0.027165,  0.026861
+                            ,  0.026564,  0.026271,  0.025981,  0.025699
+                            ,  0.025421,  0.025147,  0.024880,  0.024613
+                            ,  0.024353,  0.024094,  0.023842,  0.023590
+                            ,  0.023346,  0.023102,  0.022865,  0.022628
+                            ,  0.022398,  0.022173,  0.021951,  0.021733
+                            ,  0.021519,  0.021308,  0.021098,  0.020891
+                            ,  0.020688,  0.020485,  0.020286,  0.020090
+                            ,  0.019895,  0.019707,  0.019519,  0.019335
+                            ,  0.019150,  0.018974,  0.018797,  0.018624
+                            ,  0.018451,  0.018282,  0.018113,  0.017947
+                           ,  0.017782,  0.017617,  0.017455,  0.017297 };
+
+  if (fTRFsmp) delete fTRFsmp;
+  fTRFsmp = new Float_t[fTRFbin];
+
+  Float_t loTRF    = TMath::Max(fTRFlo / fDriftVelocity,time[0]);
+  Float_t hiTRF    = TMath::Min(fTRFhi / fDriftVelocity,time[kNpasa-1]);
   Float_t binWidth = (hiTRF - loTRF) / ((Float_t) fTRFbin);
+
+  // Take the linear interpolation
   for (Int_t iBin = 0; iBin < fTRFbin; iBin++) {
+
     Float_t bin = (((Float_t) iBin) + 0.5) * binWidth + loTRF;
-    fTRFint[iBin] = fTRF->Eval(bin);
+    ipos1 = ipos2 = 0;
+    diff  = 0;
+    do {
+      diff = bin - time[ipos2++];
+    } while (diff > 0);
+    ipos2--;
+    if (ipos2 > kNpasa) ipos2 = kNpasa - 1;
+    ipos1 = ipos2 - 1;
+
+    fTRFsmp[iBin] = signal[ipos2] 
+                  + diff * (signal[ipos2] - signal[ipos1]) 
+                         / (  time[ipos2] -   time[ipos1]);
+
   }
 
 }
@@ -538,11 +746,31 @@ void AliTRDdigitizer::SamplePRF()
   // Samples the pad response function
   //
 
+  const Int_t kPRFbin = 61;
+  Float_t prf[kPRFbin] = { 0.002340, 0.003380, 0.004900, 0.007080, 0.010220
+                         , 0.014740, 0.021160, 0.030230, 0.042800, 0.059830
+                         , 0.082030, 0.109700, 0.142550, 0.179840, 0.220610
+                         , 0.263980, 0.309180, 0.355610, 0.402790, 0.450350
+                         , 0.497930, 0.545190, 0.591740, 0.637100, 0.680610
+                         , 0.721430, 0.758400, 0.790090, 0.814720, 0.830480
+                         , 0.835930, 0.830480, 0.814710, 0.790070, 0.758390
+                         , 0.721410, 0.680590, 0.637080, 0.591730, 0.545180
+                         , 0.497920, 0.450340, 0.402790, 0.355610, 0.309190
+                         , 0.263990, 0.220630, 0.179850, 0.142570, 0.109720
+                         , 0.082040, 0.059830, 0.042820, 0.030230, 0.021170
+                         , 0.014740, 0.010230, 0.007080, 0.004900, 0.003380
+                        , 0.002340 };
+
+  fPRFlo  = -1.5;
+  fPRFhi  =  1.5;
+  fPRFbin = kPRFbin;
+  fPRFwid = (fPRFhi - fPRFlo) / ((Float_t) fPRFbin);
+  fPRFpad = ((Int_t) (1.0 / fPRFwid));
+
   if (fPRFsmp) delete fPRFsmp;
   fPRFsmp = new Float_t[fPRFbin];
   for (Int_t iBin = 0; iBin < fPRFbin; iBin++) {
-    Float_t bin = (((Float_t ) iBin) + 0.5) * fPRFwid + fPRFlo;
-    fPRFsmp[iBin] = TMath::Max(fPRF->Eval(bin),0.0);
+    fPRFsmp[iBin] = prf[iBin];
   }
 
 }
@@ -557,19 +785,25 @@ Bool_t AliTRDdigitizer::Open(const Char_t *name, Int_t nEvent)
   // Connect the AliRoot file containing Geometry, Kine, and Hits
   fInputFile = (TFile*) gROOT->GetListOfFiles()->FindObject(name);
   if (!fInputFile) {
-    printf("AliTRDdigitizer::Open -- ");
-    printf("Open the ALIROOT-file %s.\n",name);
+    if (fVerbose > 0) {
+      printf("AliTRDdigitizer::Open -- ");
+      printf("Open the AliROOT-file %s.\n",name);
+    }
     fInputFile = new TFile(name,"UPDATE");
   }
   else {
-    printf("AliTRDdigitizer::Open -- ");
-    printf("%s is already open.\n",name);
+    if (fVerbose > 0) {
+      printf("AliTRDdigitizer::Open -- ");
+      printf("%s is already open.\n",name);
+    }
   }
 
   gAlice = (AliRun*) fInputFile->Get("gAlice");
   if (gAlice) {
-    printf("AliTRDdigitizer::Open -- ");
-    printf("AliRun object found on file.\n");
+    if (fVerbose > 0) {
+      printf("AliTRDdigitizer::Open -- ");
+      printf("AliRun object found on file.\n");
+    }
   }
   else {
     printf("AliTRDdigitizer::Open -- ");
@@ -587,7 +821,12 @@ Bool_t AliTRDdigitizer::Open(const Char_t *name, Int_t nEvent)
     return kFALSE;
   }
 
-  return InitDetector();
+  if (InitDetector()) {
+    return MakeBranch();
+  }
+  else {
+    return kFALSE;
+  }
 
 }
 
@@ -608,22 +847,36 @@ Bool_t AliTRDdigitizer::InitDetector()
 
   // Get the geometry
   fGeo = fTRD->GetGeometry();
-  printf("AliTRDdigitizer::InitDetector -- ");
-  printf("Geometry version %d\n",fGeo->IsVersion());
+  if (fVerbose > 0) {
+    printf("AliTRDdigitizer::InitDetector -- ");
+    printf("Geometry version %d\n",fGeo->IsVersion());
+  }
 
-  return kTRUE;
+  // The magnetic field strength in Tesla
+  fField = 0.2 * gAlice->Field()->Factor();
+
+  // Create a digits manager
+  fDigitsManager = new AliTRDdigitsManager();
+  fDigitsManager->SetSDigits(fSDigits);
+  fDigitsManager->CreateArrays();
+  fDigitsManager->SetEvent(fEvent);
+  fDigitsManager->SetVerbose(fVerbose);
+
+  // The list for the input s-digits manager to be merged
+  fSDigitsManagerList = new TList();
+
+  return ReInit();
 
 }
 
 //_____________________________________________________________________________
-Bool_t AliTRDdigitizer::SumSDigits()
+Bool_t AliTRDdigitizer::MakeBranch(const Char_t *file)
 {
-  //
-  // Sums up the summable digits and creates final digits
-  // Not yet implemented
+  // 
+  // Create the branches for the digits array
   //
 
-  return kFALSE;
+  return fDigitsManager->MakeBranch(file);
 
 }
 
@@ -631,7 +884,7 @@ Bool_t AliTRDdigitizer::SumSDigits()
 Bool_t AliTRDdigitizer::MakeDigits()
 {
   //
-  // Creates summable digits.
+  // Creates digits.
   //
 
   ///////////////////////////////////////////////////////////////
@@ -639,7 +892,7 @@ Bool_t AliTRDdigitizer::MakeDigits()
   ///////////////////////////////////////////////////////////////
 
   // Converts number of electrons to fC
-  const Float_t kEl2fC  = 1.602E-19 * 1.0E15; 
+  const Double_t kEl2fC  = 1.602E-19 * 1.0E15; 
 
   ///////////////////////////////////////////////////////////////
 
@@ -649,6 +902,9 @@ Bool_t AliTRDdigitizer::MakeDigits()
   // Number of track dictionary arrays
   const Int_t kNDict = AliTRDdigitsManager::kNDict;
 
+  // Half the width of the amplification region
+  const Float_t kAmWidth = AliTRDgeometry::AmThick() / 2.;
+
   Int_t   iRow, iCol, iTime, iPad;
   Int_t   iDict  = 0;
   Int_t   nBytes = 0;
@@ -658,26 +914,33 @@ Bool_t AliTRDdigitizer::MakeDigits()
   Int_t   totalSizeDict1  = 0;
   Int_t   totalSizeDict2  = 0;
 
+  Int_t   timeTRDbeg = 0;
+  Int_t   timeTRDend = 1;
+
+  Float_t pos[3];
+  Float_t rot[3];
+  Float_t xyz[3];
+  Float_t padSignal[kNpad];
+  Float_t signalOld[kNpad];
+
   AliTRDdataArrayF *signals = 0;
   AliTRDdataArrayI *digits  = 0;
   AliTRDdataArrayI *dictionary[kNDict];
 
-  // Create a digits manager
-  fDigits = new AliTRDdigitsManager();
-
   // Create a container for the amplitudes
   AliTRDsegmentArray *signalsArray 
                      = new AliTRDsegmentArray("AliTRDdataArrayF",AliTRDgeometry::Ndet());
 
-  if (!fGeo) {
-    printf("AliTRDdigitizer::MakeDigits -- ");
-    printf("No geometry defined\n");
-    return kFALSE;
+  if (fTRFOn) {
+    timeTRDbeg = ((Int_t) (-fTRFlo / fGeo->GetTimeBinSize())) - 1;
+    timeTRDend = ((Int_t) ( fTRFhi / fGeo->GetTimeBinSize())) - 1;
+    if (fVerbose > 0) {
+      printf("AliTRDdigitizer::MakeDigits -- ");
+      printf("Sample the TRF between -%d and %d\n",timeTRDbeg,timeTRDend);
+    }
   }
 
-  printf("AliTRDdigitizer::MakeDigits -- ");
-  printf("Start creating digits.\n");
-  if (fVerbose > 0) this->Dump();
+  Float_t elAttachProp = fElAttachProp / 100.; 
 
   // Create the sampled PRF
   SamplePRF();
@@ -685,6 +948,17 @@ Bool_t AliTRDdigitizer::MakeDigits()
   // Create the sampled TRF
   SampleTRF();
 
+  if (!fGeo) {
+    printf("AliTRDdigitizer::MakeDigits -- ");
+    printf("No geometry defined\n");
+    return kFALSE;
+  }
+
+  if (fVerbose > 0) {
+    printf("AliTRDdigitizer::MakeDigits -- ");
+    printf("Start creating digits.\n");
+  }
+
   // Get the pointer to the hit tree
   TTree *HitTree = gAlice->TreeH();
 
@@ -718,7 +992,6 @@ Bool_t AliTRDdigitizer::MakeDigits()
       countHits++;
 
       AliTRDhit *hit = (AliTRDhit *) fTRD->Hits()->UncheckedAt(iHit);
-      Float_t pos[3];
               pos[0]   = hit->X();
               pos[1]   = hit->Y();
               pos[2]   = hit->Z();
@@ -734,12 +1007,18 @@ Bool_t AliTRDdigitizer::MakeDigits()
       Int_t   nRowMax     = fGeo->GetRowMax(plane,chamber,sector);
       Int_t   nColMax     = fGeo->GetColMax(plane);
       Int_t   nTimeMax    = fGeo->GetTimeMax();
+      Int_t   nTimeBefore = fGeo->GetTimeBefore();
+      Int_t   nTimeAfter  = fGeo->GetTimeAfter();
+      Int_t   nTimeTotal  = fGeo->GetTimeTotal();
       Float_t row0        = fGeo->GetRow0(plane,chamber,sector);
       Float_t col0        = fGeo->GetCol0(plane);
       Float_t time0       = fGeo->GetTime0(plane);
       Float_t rowPadSize  = fGeo->GetRowPadSize(plane,chamber,sector);
       Float_t colPadSize  = fGeo->GetColPadSize(plane);
       Float_t timeBinSize = fGeo->GetTimeBinSize();
+      Float_t divideRow   = 1.0 / rowPadSize;
+      Float_t divideCol   = 1.0 / colPadSize;
+      Float_t divideTime  = 1.0 / timeBinSize;
 
       if (fVerbose > 1) {
         printf("Analyze hit no. %d ",iHit);
@@ -749,14 +1028,16 @@ Bool_t AliTRDdigitizer::MakeDigits()
               ,plane,sector,chamber);
         printf("nRowMax = %d, nColMax = %d, nTimeMax = %d\n" 
               ,nRowMax,nColMax,nTimeMax);
+        printf("nTimeBefore = %d, nTimeAfter = %d, nTimeTotal = %d\n"
+             ,nTimeBefore,nTimeAfter,nTimeTotal);
         printf("row0 = %f, col0 = %f, time0 = %f\n"
               ,row0,col0,time0);
         printf("rowPadSize = %f, colPadSize = %f, timeBinSize = %f\n"
               ,rowPadSize,colPadSize,timeBinSize); 
       }
        
-      // Don't analyze test hits with amplitude 0.
-      if (((Int_t) q) == 0) continue;
+      // Don't analyze test hits
+      if (hit->FromTest()) continue;
 
       if (detector != detectorOld) {
 
@@ -785,7 +1066,7 @@ Bool_t AliTRDdigitizer::MakeDigits()
             printf("AliTRDdigitizer::MakeDigits -- ");
             printf("Allocate a new container ... ");
          }
-          signals->Allocate(nRowMax,nColMax,nTimeMax);
+          signals->Allocate(nRowMax,nColMax,nTimeTotal);
        }
         else {
          // Expand an existing one
@@ -799,9 +1080,9 @@ Bool_t AliTRDdigitizer::MakeDigits()
        }
        // The same for the dictionary
         for (iDict = 0; iDict < kNDict; iDict++) {       
-          dictionary[iDict] = fDigits->GetDictionary(detector,iDict);
+          dictionary[iDict] = fDigitsManager->GetDictionary(detector,iDict);
           if (dictionary[iDict]->GetNtime() == 0) {
-            dictionary[iDict]->Allocate(nRowMax,nColMax,nTimeMax);
+            dictionary[iDict]->Allocate(nRowMax,nColMax,nTimeTotal);
          }
           else {
             if (fCompress) dictionary[iDict]->Expand();
@@ -812,41 +1093,31 @@ Bool_t AliTRDdigitizer::MakeDigits()
       }
 
       // Rotate the sectors on top of each other
-      Float_t rot[3];
       fGeo->Rotate(detector,pos,rot);
 
-      // The driftlength
+      // The driftlength. It is negative if the hit is in the 
+      // amplification region.
       Float_t driftlength = time0 - rot[0];
-      if ((driftlength < 0) || 
-          (driftlength > AliTRDgeometry::DrThick())) continue;
-      Float_t driftlengthL = driftlength;
-      if (fExBOn) driftlengthL /= TMath::Sqrt(fLorentzFactor);
 
-      // The hit position in pad coordinates (center pad)
-      // The pad row (z-direction)
-      Int_t  rowH = (Int_t) ((rot[2] -  row0) /  rowPadSize);
-      // The pad column (rphi-direction)  
-      Int_t  colH = (Int_t) ((rot[1] -  col0) /  colPadSize);
-      // The time bucket
-      Int_t timeH = (Int_t) (driftlength      / timeBinSize);
-      if (fVerbose > 1) {
-        printf("rowH = %d, colH = %d, timeH = %d\n"
-              ,rowH,colH,timeH);
-      }
+      // Take also the drift in the amplification region into account
+      // The drift length is at the moment still the same, regardless of
+      // the position relativ to the wire. This non-isochronity needs still
+      // to be implemented.
+      Float_t driftlengthL = TMath::Abs(driftlength + kAmWidth);
+      if (fExBOn) driftlengthL /= TMath::Sqrt(fLorentzFactor);
 
       // Loop over all electrons of this hit
       // TR photons produce hits with negative charge
       Int_t nEl = ((Int_t) TMath::Abs(q));
       for (Int_t iEl = 0; iEl < nEl; iEl++) {
 
-        Float_t xyz[3];
         xyz[0] = rot[0];
         xyz[1] = rot[1];
         xyz[2] = rot[2];
 
         // Electron attachment
         if (fElAttachOn) {
-          if (gRandom->Rndm() < (driftlengthL * fElAttachProp / 100.)) 
+          if (gRandom->Rndm() < (driftlengthL * elAttachProp)) 
             continue;
         }
 
@@ -855,22 +1126,42 @@ Bool_t AliTRDdigitizer::MakeDigits()
           if (!(Diffusion(driftlengthL,xyz))) continue;
        }
 
-        // Apply E x B effects
+        // Apply E x B effects (depends on drift direction)
         if (fExBOn) { 
-          if (!(ExB(driftlength,xyz))) continue;   
+          if (!(ExB(driftlength+kAmWidth,xyz))) continue;   
        }
 
-        // The electron position 
+        // The electron position after diffusion and ExB in pad coordinates 
         // The pad row (z-direction)
-        Int_t  rowE = (Int_t) ((xyz[2] -  row0) /  rowPadSize);
-        if (( rowE < 0) || ( rowE >=  nRowMax)) continue;
-        // The pad column (rphi-direction)
-        Int_t  colE = (Int_t) ((xyz[1] -  col0) /  colPadSize);
-        if (( colE < 0) || ( colE >=  nColMax)) continue;
-        // The time bucket
-        Int_t timeE = (Int_t) ((time0 - xyz[0]) / timeBinSize);
-        if ((timeE < 0) || (timeE >= nTimeMax)) continue;
+        Int_t  rowE = ((Int_t) ((xyz[2] -  row0) * divideRow));
+        if ((rowE < 0) || (rowE >= nRowMax)) continue;   
 
+        // The pad column (rphi-direction)
+        Int_t  colE = ((Int_t) ((xyz[1] -  col0) * divideCol));
+        if ((colE < 0) || (colE >= nColMax)) continue;   
+  
+        // The time bin (negative for hits in the amplification region)
+       // In the amplification region the electrons drift from both sides
+       // to the middle (anode wire plane)
+        Float_t timeDist   = time0 - xyz[0];
+        Float_t timeOffset = 0;
+        Int_t   timeE      = 0;
+        if (timeDist > 0) {
+         // The time bin
+          timeE      = ((Int_t) (timeDist * divideTime));
+          // The distance of the position to the middle of the timebin
+          timeOffset = ((((Float_t) timeE) + 0.5) * timeBinSize) - timeDist;
+       }
+        else {
+         // Difference between half of the amplification gap width and
+         // the distance to the anode wire
+          Float_t anodeDist = kAmWidth - TMath::Abs(timeDist + kAmWidth);
+          // The time bin
+          timeE      = -1 * (((Int_t ) (anodeDist * divideTime)) + 1);
+          // The distance of the position to the middle of the timebin
+          timeOffset = ((((Float_t) timeE) + 0.5) * timeBinSize) + anodeDist;
+       }
         // Apply the gas gain including fluctuations
         Float_t ggRndm = 0.0;
         do {
@@ -879,12 +1170,11 @@ Bool_t AliTRDdigitizer::MakeDigits()
         Int_t signal = (Int_t) (-fGasGain * TMath::Log(ggRndm));
 
         // Apply the pad response 
-        Float_t padSignal[kNpad];
         if (fPRFOn) {
          // The distance of the electron to the center of the pad 
          // in units of pad width
           Float_t dist = (xyz[1] - col0 - (colE + 0.5) * colPadSize) 
-                       / colPadSize;
+                       * divideCol;
           if (!(PadResponse(signal,dist,padSignal))) continue;
        }
        else {
@@ -893,16 +1183,11 @@ Bool_t AliTRDdigitizer::MakeDigits()
           padSignal[2] = 0.0;
        }
 
-        // The distance of the position to the beginning of the timebin
-        Float_t timeOffset = (time0 - timeE * timeBinSize) - xyz[0];
-        Int_t timeTRDbeg = 0;
-        Int_t timeTRDend = 1;
-        if (fTRFOn) {
-          timeTRDbeg =  2;
-          timeTRDend = 11;
-       }
-        for (Int_t iTimeBin = TMath::Max(timeE - timeTRDbeg,       0)
-                 ;iTimeBin < TMath::Min(timeE + timeTRDend,nTimeMax) 
+       // Sample the time response inside the drift region
+       // + additional time bins before and after.
+        // The sampling is done always in the middle of the time bin
+        for (Int_t iTimeBin = TMath::Max(timeE-timeTRDbeg,        -nTimeBefore) 
+                 ;iTimeBin < TMath::Min(timeE+timeTRDend,nTimeMax+nTimeAfter ) 
                  ;iTimeBin++) {
 
          // Apply the time response
@@ -912,51 +1197,40 @@ Bool_t AliTRDdigitizer::MakeDigits()
             timeResponse = TimeResponse(time);
          }
 
-          // Add the signals
-          Float_t signalOld[kNpad] = { 0.0, 0.0, 0.0 };
+          signalOld[0] = 0.0;
+          signalOld[1] = 0.0;
+          signalOld[2] = 0.0;
+
           for (iPad = 0; iPad < kNpad; iPad++) {
+
             Int_t colPos = colE + iPad - 1;
             if (colPos <        0) continue;
             if (colPos >= nColMax) break;
-            signalOld[iPad]  = signals->GetData(rowE,colPos,iTimeBin);
+
+            // Add the signals
+           // Note: The time bin number is shifted by nTimeBefore to avoid negative
+           // time bins. This has to be subtracted later.
+            Int_t iCurrentTimeBin = iTimeBin + nTimeBefore;
+            signalOld[iPad]  = signals->GetDataUnchecked(rowE,colPos,iCurrentTimeBin);
             signalOld[iPad] += padSignal[iPad] * timeResponse;
-            signals->SetData(rowE,colPos,iTimeBin,signalOld[iPad]);
-         }
+            signals->SetDataUnchecked(rowE,colPos,iCurrentTimeBin,signalOld[iPad]);
 
-          // Store the track index in the dictionary
-          // Note: We store index+1 in order to allow the array to be compressed
-          //for (iDict = 0; iDict < kNDict; iDict++) {
-          //  Int_t oldTrack = dictionary[iDict]->GetData(rowE,colE,timeE);
-          //  if (oldTrack == track+1) break;
-          //  //if (oldTrack ==      -1) break;
-          //  if (oldTrack ==       0) {
-          //    dictionary[iDict]->SetData(rowE,colE,timeE,track+1);
-          //    if (fVerbose > 3) {
-          //      printf("    track index = %d\n",track); 
-         //    }
-          //    break;
-          //  }
-          //}
-          for (iPad = 0; iPad < kNpad; iPad++) {
-            Int_t colPos = colE + iPad - 1;
-            if (colPos <        0) continue;
-            if (colPos >= nColMax) break;
-            if (signals->GetData(rowE,colPos,iTimeBin) > 0) {
+            // Store the track index in the dictionary
+            // Note: We store index+1 in order to allow the array to be compressed
+            if (signalOld[iPad] > 0) {
               for (iDict = 0; iDict < kNDict; iDict++) {
-                Int_t oldTrack = dictionary[iDict]->GetData(rowE,colPos,iTimeBin);
+                Int_t oldTrack = dictionary[iDict]->GetDataUnchecked(rowE
+                                                                    ,colPos
+                                                                    ,iCurrentTimeBin);
                 if (oldTrack == track+1) break;
-                //if (oldTrack ==      -1) break;
                 if (oldTrack ==       0) {
-                  dictionary[iDict]->SetData(rowE,colPos,iTimeBin,track+1);
+                  dictionary[iDict]->SetDataUnchecked(rowE,colPos,iCurrentTimeBin,track+1);
                   break;
                 }
               }
             }
-          }
-          //if ((fVerbose > 1) && (iDict == kNDict)) {
-          //  printf("AliTRDdigitizer::MakeDigits -- ");
-          //  printf("More than three tracks for one digit!\n");
-          //}
+
+         }
 
        }
 
@@ -966,8 +1240,10 @@ Bool_t AliTRDdigitizer::MakeDigits()
 
   } // All hits finished
 
-  printf("AliTRDdigitizer::MakeDigits -- ");
-  printf("Finished analyzing %d hits\n",countHits);
+  if (fVerbose > 0) {
+    printf("AliTRDdigitizer::MakeDigits -- ");
+    printf("Finished analyzing %d hits\n",countHits);
+  }
 
   // The total conversion factor
   Float_t convert = kEl2fC * fPadCoupling * fTimeCoupling * fChipGain;
@@ -975,12 +1251,13 @@ Bool_t AliTRDdigitizer::MakeDigits()
   // Loop through all chambers to finalize the digits
   for (Int_t iDet = 0; iDet < AliTRDgeometry::Ndet(); iDet++) {
 
-    Int_t plane    = fGeo->GetPlane(iDet);
-    Int_t sector   = fGeo->GetSector(iDet);
-    Int_t chamber  = fGeo->GetChamber(iDet);
-    Int_t nRowMax  = fGeo->GetRowMax(plane,chamber,sector);
-    Int_t nColMax  = fGeo->GetColMax(plane);
-    Int_t nTimeMax = fGeo->GetTimeMax();
+    Int_t plane       = fGeo->GetPlane(iDet);
+    Int_t sector      = fGeo->GetSector(iDet);
+    Int_t chamber     = fGeo->GetChamber(iDet);
+    Int_t nRowMax     = fGeo->GetRowMax(plane,chamber,sector);
+    Int_t nColMax     = fGeo->GetColMax(plane);
+    Int_t nTimeMax    = fGeo->GetTimeMax();
+    Int_t nTimeTotal  = fGeo->GetTimeTotal();
 
     if (fVerbose > 0) {
       printf("AliTRDdigitizer::MakeDigits -- ");
@@ -988,15 +1265,15 @@ Bool_t AliTRDdigitizer::MakeDigits()
     }
 
     // Add a container for the digits of this detector
-    digits = fDigits->GetDigits(iDet);        
+    digits = fDigitsManager->GetDigits(iDet);        
     // Allocate memory space for the digits buffer
-    digits->Allocate(nRowMax,nColMax,nTimeMax);
+    digits->Allocate(nRowMax,nColMax,nTimeTotal);
 
     // Get the signal container
     signals = (AliTRDdataArrayF *) signalsArray->At(iDet);
     if (signals->GetNtime() == 0) {
       // Create missing containers
-      signals->Allocate(nRowMax,nColMax,nTimeMax);      
+      signals->Allocate(nRowMax,nColMax,nTimeTotal);      
     }
     else {
       // Expand the container if neccessary
@@ -1004,9 +1281,9 @@ Bool_t AliTRDdigitizer::MakeDigits()
     }
     // Create the missing dictionary containers
     for (iDict = 0; iDict < kNDict; iDict++) {       
-      dictionary[iDict] = fDigits->GetDictionary(iDet,iDict);
+      dictionary[iDict] = fDigitsManager->GetDictionary(iDet,iDict);
       if (dictionary[iDict]->GetNtime() == 0) {
-        dictionary[iDict]->Allocate(nRowMax,nColMax,nTimeMax);
+        dictionary[iDict]->Allocate(nRowMax,nColMax,nTimeTotal);
       }
     }
 
@@ -1016,29 +1293,25 @@ Bool_t AliTRDdigitizer::MakeDigits()
     if (CheckDetector(plane,chamber,sector)) {
 
       // Create the digits for this chamber
-      for (iRow  = 0; iRow  <  nRowMax; iRow++ ) {
-        for (iCol  = 0; iCol  <  nColMax; iCol++ ) {
-          for (iTime = 0; iTime < nTimeMax; iTime++) {         
+      for (iRow  = 0; iRow  <  nRowMax;   iRow++ ) {
+        for (iCol  = 0; iCol  <  nColMax;   iCol++ ) {
+          for (iTime = 0; iTime < nTimeTotal; iTime++) {         
 
            // Create summable digits
             if (fSDigits) {
 
-              Float_t signalAmp = signals->GetData(iRow,iCol,iTime);
-              Int_t adc  = 0;
-              if (signalAmp >= fSinRange) {
-                adc = ((Int_t) fSoutRange);
-             }
-              else {
-                adc = ((Int_t) (signalAmp * (fSoutRange / fSinRange)));
-             }
+              Float_t signalAmp = signals->GetDataUnchecked(iRow,iCol,iTime);
+              signalAmp *= fSDigitsScale;
+              signalAmp  = TMath::Min(signalAmp,(Float_t)1.0e9);
+              Int_t adc  = (Int_t) signalAmp;
               nDigits++;
-              digits->SetData(iRow,iCol,iTime,adc);
+              digits->SetDataUnchecked(iRow,iCol,iTime,adc);
 
            }
            // Create normal digits
             else {
 
-              Float_t signalAmp = signals->GetData(iRow,iCol,iTime);
+              Float_t signalAmp = signals->GetDataUnchecked(iRow,iCol,iTime);
 
               // Add the noise
               signalAmp  = TMath::Max((Double_t) gRandom->Gaus(signalAmp,fNoise),0.0);
@@ -1062,7 +1335,7 @@ Bool_t AliTRDdigitizer::MakeDigits()
                   printf("  signal = %f, adc = %d\n",signalAmp,adc);
                }
                 nDigits++;
-                digits->SetData(iRow,iCol,iTime,adc);
+                digits->SetDataUnchecked(iRow,iCol,iTime,adc);
              }
 
            }
@@ -1085,28 +1358,276 @@ Bool_t AliTRDdigitizer::MakeDigits()
     totalSizeDict2  += dictionary[2]->GetSize();
 
     Float_t nPixel = nRowMax * nColMax * nTimeMax;
-    printf("AliTRDdigitizer::MakeDigits -- ");
-    printf("Found %d digits in detector %d (%3.0f).\n"
-          ,nDigits,iDet
-          ,100.0 * ((Float_t) nDigits) / nPixel);
+    if (fVerbose > 0) {
+      printf("AliTRDdigitizer::MakeDigits -- ");
+      printf("Found %d digits in detector %d (%3.0f).\n"
+            ,nDigits,iDet
+            ,100.0 * ((Float_t) nDigits) / nPixel);
+    } 
+
     if (fCompress) signals->Compress(1,0);
 
   }
 
-  printf("AliTRDdigitizer::MakeDigits -- ");
-  printf("Total number of analyzed hits = %d\n",countHits);
+  if (fVerbose > 0) {
+    printf("AliTRDdigitizer::MakeDigits -- ");
+    printf("Total number of analyzed hits = %d\n",countHits);
+    printf("AliTRDdigitizer::MakeDigits -- ");
+    printf("Total digits data size = %d, %d, %d, %d\n",totalSizeDigits
+                                                      ,totalSizeDict0
+                                                      ,totalSizeDict1
+                                                      ,totalSizeDict2);        
+  }
+
+  return kTRUE;
+
+}
+
+//_____________________________________________________________________________
+void AliTRDdigitizer::AddSDigitsManager(AliTRDdigitsManager *man)
+{
+  //
+  // Add a digits manager for s-digits to the input list.
+  //
+
+  fSDigitsManagerList->Add(man);
+
+}
+
+//_____________________________________________________________________________
+Bool_t AliTRDdigitizer::ConvertSDigits()
+{
+  //
+  // Converts s-digits to normal digits
+  //
+
+  // Number of track dictionary arrays
+  const Int_t    kNDict = AliTRDdigitsManager::kNDict;
+
+  // Converts number of electrons to fC
+  const Double_t kEl2fC = 1.602E-19 * 1.0E15; 
+
+  Int_t iDict = 0;
+
+  if (fVerbose > 0) {
+    this->Dump();
+  }
+
+  Double_t sDigitsScale = 1.0 / GetSDigitsScale();
+  Double_t noise        = GetNoise();
+  Double_t padCoupling  = GetPadCoupling();
+  Double_t timeCoupling = GetTimeCoupling();
+  Double_t chipGain     = GetChipGain();
+  Double_t convert      = kEl2fC * padCoupling * timeCoupling * chipGain;;
+  Double_t adcInRange   = GetADCinRange();
+  Double_t adcOutRange  = GetADCoutRange();
+  Int_t    adcThreshold = GetADCthreshold();
+
+  AliTRDdataArrayI *digitsIn;
+  AliTRDdataArrayI *digitsOut;
+  AliTRDdataArrayI *dictionaryIn[kNDict];
+  AliTRDdataArrayI *dictionaryOut[kNDict];
+
+  // Loop through the detectors
+  for (Int_t iDet = 0; iDet < AliTRDgeometry::Ndet(); iDet++) {
+
+    if (fVerbose > 0) {
+      printf("AliTRDdigitizer::ConvertSDigits -- ");
+      printf("Convert detector %d to digits.\n",iDet);
+    }
+
+    Int_t plane      = fGeo->GetPlane(iDet);
+    Int_t sector     = fGeo->GetSector(iDet);
+    Int_t chamber    = fGeo->GetChamber(iDet);
+    Int_t nRowMax    = fGeo->GetRowMax(plane,chamber,sector);
+    Int_t nColMax    = fGeo->GetColMax(plane);
+    Int_t nTimeTotal = fGeo->GetTimeTotal();
+
+    digitsIn  = fSDigitsManager->GetDigits(iDet);
+    digitsIn->Expand();
+    digitsOut = fDigitsManager->GetDigits(iDet);
+    digitsOut->Allocate(nRowMax,nColMax,nTimeTotal);
+    for (iDict = 0; iDict < kNDict; iDict++) {
+      dictionaryIn[iDict]  = fSDigitsManager->GetDictionary(iDet,iDict);
+      dictionaryIn[iDict]->Expand();
+      dictionaryOut[iDict] = fDigitsManager->GetDictionary(iDet,iDict);
+      dictionaryOut[iDict]->Allocate(nRowMax,nColMax,nTimeTotal);
+    }
+
+    for (Int_t iRow  = 0; iRow  <  nRowMax;   iRow++ ) {
+      for (Int_t iCol  = 0; iCol  <  nColMax;   iCol++ ) {
+        for (Int_t iTime = 0; iTime < nTimeTotal; iTime++) {         
+
+          Double_t signal = (Double_t) digitsIn->GetDataUnchecked(iRow,iCol,iTime);
+          signal *= sDigitsScale;
+          // Add the noise
+          signal  = TMath::Max((Double_t) gRandom->Gaus(signal,noise),0.0);
+          // Convert to mV
+          signal *= convert;
+         // Convert to ADC counts. Set the overflow-bit adcOutRange if the 
+         // signal is larger than adcInRange
+          Int_t adc  = 0;
+          if (signal >= adcInRange) {
+            adc = ((Int_t) adcOutRange);
+         }
+          else {
+            adc = ((Int_t) (signal * (adcOutRange / adcInRange)));
+         }
+          // Store the amplitude of the digit if above threshold
+          if (adc > adcThreshold) {
+            digitsOut->SetDataUnchecked(iRow,iCol,iTime,adc);
+         }
+         // Copy the dictionary
+          for (iDict = 0; iDict < kNDict; iDict++) { 
+            Int_t track = dictionaryIn[iDict]->GetDataUnchecked(iRow,iCol,iTime);
+            dictionaryOut[iDict]->SetDataUnchecked(iRow,iCol,iTime,track);
+         }
+
+       }
+      }
+    }
+
+    if (fCompress) {
+      digitsIn->Compress(1,0);
+      digitsOut->Compress(1,0);
+      for (iDict = 0; iDict < kNDict; iDict++) {
+        dictionaryIn[iDict]->Compress(1,0);
+        dictionaryOut[iDict]->Compress(1,0);
+      }
+    }
 
-  printf("AliTRDdigitizer::MakeDigits -- ");
-  printf("Total digits data size = %d, %d, %d, %d\n",totalSizeDigits
-                                                    ,totalSizeDict0
-                                                    ,totalSizeDict1
-                                                    ,totalSizeDict2);        
+  }    
 
   return kTRUE;
 
 }
 
+//_____________________________________________________________________________
+Bool_t AliTRDdigitizer::MergeSDigits()
+{
+  //
+  // Merges the input s-digits:
+  //   - The amplitude of the different inputs are summed up.
+  //   - Of the track IDs from the input dictionaries only one is
+  //     kept for each input. This works for maximal 3 different merged inputs.
+  //
+
+  // Number of track dictionary arrays
+  const Int_t kNDict = AliTRDdigitsManager::kNDict;
+
+  Int_t iDict = 0;
+
+  AliTRDdataArrayI *digitsA;
+  AliTRDdataArrayI *digitsB;
+  AliTRDdataArrayI *dictionaryA[kNDict];
+  AliTRDdataArrayI *dictionaryB[kNDict];
+
+  // Get the first s-digits
+  fSDigitsManager = (AliTRDdigitsManager *) fSDigitsManagerList->First();
+  if (!fSDigitsManager) return kFALSE;
+
+  // Loop through the other sets of s-digits
+  AliTRDdigitsManager *mergeSDigitsManager;
+  mergeSDigitsManager = (AliTRDdigitsManager *) 
+                        fSDigitsManagerList->After(fSDigitsManager);
+
+  if (fVerbose > 0) {
+    if (mergeSDigitsManager) {
+      printf("AliTRDdigitizer::MergeSDigits -- ");
+      printf("Merge serveral input files.\n");
+    }
+    else {
+      printf("AliTRDdigitizer::MergeSDigits -- ");
+      printf("Only one input file.\n");
+    }
+  }
+
+  Int_t iMerge = 0;
+  while (mergeSDigitsManager) {
+
+    iMerge++;
+
+    // Loop through the detectors
+    for (Int_t iDet = 0; iDet < AliTRDgeometry::Ndet(); iDet++) {
+
+      Int_t plane      = fGeo->GetPlane(iDet);
+      Int_t sector     = fGeo->GetSector(iDet);
+      Int_t chamber    = fGeo->GetChamber(iDet);
+      Int_t nRowMax    = fGeo->GetRowMax(plane,chamber,sector);
+      Int_t nColMax    = fGeo->GetColMax(plane);
+      Int_t nTimeTotal = fGeo->GetTimeTotal();
+
+      // Loop through the pixels of one detector and add the signals
+      digitsA = fSDigitsManager->GetDigits(iDet);
+      digitsB = mergeSDigitsManager->GetDigits(iDet);
+      digitsA->Expand();
+      digitsB->Expand();
+      for (iDict = 0; iDict < kNDict; iDict++) {
+        dictionaryA[iDict] = fSDigitsManager->GetDictionary(iDet,iDict);
+        dictionaryB[iDict] = mergeSDigitsManager->GetDictionary(iDet,iDict);
+        dictionaryA[iDict]->Expand();
+        dictionaryB[iDict]->Expand();
+      }
+
+      if (fVerbose > 0) {
+        printf("AliTRDdigitizer::MergeSDigits -- ");
+        printf("Merge detector %d of input no.%d.\n",iDet,iMerge);
+      }
+
+      for (Int_t iRow  = 0; iRow  <  nRowMax;   iRow++ ) {
+        for (Int_t iCol  = 0; iCol  <  nColMax;   iCol++ ) {
+          for (Int_t iTime = 0; iTime < nTimeTotal; iTime++) {         
+
+           // Add the amplitudes of the summable digits 
+            Int_t ampA = digitsA->GetDataUnchecked(iRow,iCol,iTime);
+            Int_t ampB = digitsB->GetDataUnchecked(iRow,iCol,iTime);
+            ampA += ampB;
+            digitsA->SetDataUnchecked(iRow,iCol,iTime,ampA);
+
+           // Take only one track from each input
+            Int_t track = dictionaryB[0]->GetDataUnchecked(iRow,iCol,iTime);
+            if (iMerge < kNDict) {
+              dictionaryA[iMerge]->SetDataUnchecked(iRow,iCol,iTime,track);
+           }
+
+         }
+       }
+      }
+
+      if (fCompress) {
+        digitsA->Compress(1,0);
+        digitsB->Compress(1,0);
+        for (iDict = 0; iDict < kNDict; iDict++) {
+          dictionaryA[iDict]->Compress(1,0);
+          dictionaryB[iDict]->Compress(1,0);
+        }
+      }
+
+    }    
+
+    // The next set of s-digits
+    mergeSDigitsManager = (AliTRDdigitsManager *) 
+                          fSDigitsManagerList->After(mergeSDigitsManager);
+
+  }
+
+  return kTRUE;
+
+}
+
+//_____________________________________________________________________________
+Bool_t AliTRDdigitizer::SDigits2Digits()
+{
+  //
+  // Merges the input s-digits and converts them to normal digits
+  //
+
+  if (!MergeSDigits()) return kFALSE;
+
+  return ConvertSDigits();
+
+}
+
 //_____________________________________________________________________________
 Bool_t AliTRDdigitizer::CheckDetector(Int_t plane, Int_t chamber, Int_t sector)
 {
@@ -1142,62 +1663,92 @@ Bool_t AliTRDdigitizer::WriteDigits()
   // Writes out the TRD-digits and the dictionaries
   //
 
-  // Create the branches
-  if (!(gAlice->TreeD()->GetBranch("TRDdigits"))) { 
-    return kFALSE;
-    //if (!fDigits->MakeBranch()) {
-    //  printf("AliTRDdigitizer::WriteDigits -- ");
-    //  printf("MakeBranch failed.\n");
-    //  return kFALSE;
-    //}
-  }
-
   // Store the digits and the dictionary in the tree
-  fDigits->WriteDigits();
-
-  // Write the new tree into the input file (use overwrite option)
-  Char_t treeName[15];
-  sprintf(treeName,"TreeD%d",fEvent);
-  printf("AliTRDdigitizer::WriteDigits -- ");
-  printf("Write the digits tree %s for event %d.\n"
-        ,treeName,fEvent);
-  gAlice->TreeD()->Write(treeName,TObject::kOverwrite);
-  return kTRUE;
+  return fDigitsManager->WriteDigits();
 
 }
 
 //_____________________________________________________________________________
-void AliTRDdigitizer::SetPRF(TF1 *prf)
+Float_t AliTRDdigitizer::GetDiffusionL(Float_t vd, Float_t b)
 {
   //
-  // Defines a new pad response function
+  // Returns the longitudinal diffusion coefficient for a given drift 
+  // velocity <vd> and a B-field <b> for Xe/CO2 (15%).
+  // The values are according to a GARFIELD simulation.
   //
 
-  if (fPRF) delete fPRF;
-  fPRF = prf;     
+  const Int_t kNb = 5;
+  Float_t p0[kNb] = {  0.007440,  0.007493,  0.007513,  0.007672,  0.007831 };
+  Float_t p1[kNb] = {  0.019252,  0.018912,  0.018636,  0.018012,  0.017343 };
+  Float_t p2[kNb] = { -0.005042, -0.004926, -0.004867, -0.004650, -0.004424 };
+  Float_t p3[kNb] = {  0.000195,  0.000189,  0.000195,  0.000182,  0.000169 };
+
+  Int_t ib = ((Int_t) (10 * (b - 0.15)));
+  ib       = TMath::Max(  0,ib);
+  ib       = TMath::Min(kNb,ib);
+
+  Float_t diff = p0[ib] 
+               + p1[ib] * vd
+               + p2[ib] * vd*vd
+               + p3[ib] * vd*vd*vd;
+
+  return diff;
 
 }
 
 //_____________________________________________________________________________
-void AliTRDdigitizer::SetTRF(TF1 *trf)
+Float_t AliTRDdigitizer::GetDiffusionT(Float_t vd, Float_t b)
 {
   //
-  // Defines a new time response function
+  // Returns the transverse diffusion coefficient for a given drift 
+  // velocity <vd> and a B-field <b> for Xe/CO2 (15%).
+  // The values are according to a GARFIELD simulation.
   //
 
-  if (fTRF) delete fTRF;
-  fTRF = trf;     
+  const Int_t kNb = 5;
+  Float_t p0[kNb] = {  0.009550,  0.009599,  0.009674,  0.009757,  0.009850 };
+  Float_t p1[kNb] = {  0.006667,  0.006539,  0.006359,  0.006153,  0.005925 };
+  Float_t p2[kNb] = { -0.000853, -0.000798, -0.000721, -0.000635, -0.000541 };
+  Float_t p3[kNb] = {  0.000131,  0.000122,  0.000111,  0.000098,  0.000085 };
+
+  Int_t ib = ((Int_t) (10 * (b - 0.15)));
+  ib       = TMath::Max(  0,ib);
+  ib       = TMath::Min(kNb,ib);
+
+  Float_t diff = p0[ib] 
+               + p1[ib] * vd
+               + p2[ib] * vd*vd
+               + p3[ib] * vd*vd*vd;
+
+  return diff;
 
 }
 
 //_____________________________________________________________________________
-Double_t TRFlandau(Double_t *x, Double_t *par)
+Float_t AliTRDdigitizer::GetOmegaTau(Float_t vd, Float_t b)
 {
+  //
+  // Returns omega*tau (tan(Lorentz-angle)) for a given drift velocity <vd> 
+  // and a B-field <b> for Xe/CO2 (15%).
+  // The values are according to a GARFIELD simulation.
+  //
 
-  Double_t xx = x[0];
-  Double_t landau = par[0] * TMath::Landau(xx,par[1],par[2]);
+  const Int_t kNb = 5;
+  Float_t p0[kNb] = {  0.004810,  0.007412,  0.010252,  0.013409,  0.016888 };
+  Float_t p1[kNb] = {  0.054875,  0.081534,  0.107333,  0.131983,  0.155455 };
+  Float_t p2[kNb] = { -0.008682, -0.012896, -0.016987, -0.020880, -0.024623 };
+  Float_t p3[kNb] = {  0.000155,  0.000238,  0.000330,  0.000428,  0.000541 };
 
-  return landau;
+  Int_t ib = ((Int_t) (10 * (b - 0.15)));
+  ib       = TMath::Max(  0,ib);
+  ib       = TMath::Min(kNb,ib);
+
+  Float_t alphaL = p0[ib] 
+                 + p1[ib] * vd
+                 + p2[ib] * vd*vd
+                 + p3[ib] * vd*vd*vd;
+
+  return TMath::Tan(alphaL);
 
 }
+