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[u/mrichter/AliRoot.git] / ITS / AliITSsimulationSSD.cxx

/**************************************************************************
 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/
/* $Id$ */

#include <stdio.h>
#include <stdlib.h>
#include <Riostream.h>
#include <TObjArray.h>
#include <TParticle.h>
#include <TRandom.h>
#include <TMath.h>
#include <TH1.h>

#include "AliITSmodule.h"
#include "AliITSMapA2.h"
#include "AliITSpList.h"
#include "AliITSresponseSSD.h"
#include "AliITSsegmentationSSD.h"
#include "AliITSdcsSSD.h"
#include "AliITS.h"
#include "AliITShit.h"
#include "AliITSdigit.h"
#include "AliRun.h"
#include "AliITSgeom.h"
#include "AliITSsimulationSSD.h"
#include "AliITSTableSSD.h"

ClassImp(AliITSsimulationSSD);
////////////////////////////////////////////////////////////////////////
// Version: 0
// Written by Enrico Fragiacomo
// July 2000
//
// AliITSsimulationSSD is the simulation of SSDs.

//----------------------------------------------------------------------
AliITSsimulationSSD::AliITSsimulationSSD(){
  //default Constructor

  fDCS     = 0;
  fDifConst[0] = fDifConst[1] = 0.0;
  fDriftVel[0] = fDriftVel[1] = 0.0;
  fMapA2   = 0;
//  fpList    = 0;
}
//----------------------------------------------------------------------
AliITSsimulationSSD::AliITSsimulationSSD(AliITSsegmentation *seg,
                                         AliITSresponse *resp){
    // Constructor 
    // Input:
    //   AliITSsegmentationSSD *seg  Pointer to the SSD segmentation to be used
    //   AliITSresponseSSD   *resp Pointer to the SSD responce class to be used
    // Outputs:
    //   none.
    // Return
    //   none.

    fDCS     = 0;
    fDifConst[0] = fDifConst[1] = 0.0;
    fDriftVel[0] = fDriftVel[1] = 0.0;
    fMapA2   = 0;
//    fpList    = 0;
    Init((AliITSsegmentationSSD*)seg,(AliITSresponseSSD*)resp);
}
//----------------------------------------------------------------------
void AliITSsimulationSSD::Init(AliITSsegmentationSSD *seg,
                               AliITSresponseSSD *resp){
    // Inilizer, Inilizes all of the variable as needed in a standard place.
    // Input:
    //   AliITSsegmentationSSD *seg  Pointer to the SSD segmentation to be used
    //   AliITSresponseSSD   *resp Pointer to the SSD responce class to be used
    // Outputs:
    //   none.
    // Return
    //   none.

    fSegmentation    = seg;
    fResponse        = resp;
    Float_t noise[2] = {0.,0.};
    fResponse->GetNoiseParam(noise[0],noise[1]); // retrieves noise parameters
    fDCS             = new AliITSdcsSSD(seg,resp); 

    SetDriftVelocity(); // use default values in .h file
    SetIonizeE();       // use default values in .h file
    SetDiffConst();     // use default values in .h file
    fpList           = new AliITSpList(2,GetNStrips());
    fMapA2           = new AliITSMapA2(fSegmentation);
}
//______________________________________________________________________
AliITSsimulationSSD& AliITSsimulationSSD::operator=(
                                         const AliITSsimulationSSD &s){
  // Operator =

  if(this==&s) return *this;

  this->fDCS         = new AliITSdcsSSD(*(s.fDCS));
  this->fMapA2       = s.fMapA2;
  this->fIonE        = s.fIonE;
  this->fDifConst[0] = s.fDifConst[0];
  this->fDifConst[1] = s.fDifConst[1];
  this->fDriftVel[0] = s.fDriftVel[0];
  this->fDriftVel[1] = s.fDriftVel[1];
  return *this;
}
//______________________________________________________________________
AliITSsimulationSSD::AliITSsimulationSSD(const AliITSsimulationSSD &source){
  // copy constructor

  *this = source;
}
//______________________________________________________________________
AliITSsimulationSSD::~AliITSsimulationSSD() {
  // destructor
  delete fMapA2;
  delete fDCS;
}
//______________________________________________________________________
void AliITSsimulationSSD::InitSimulationModule(Int_t module,Int_t event){
    // Creates maps to build the list of tracks for each sumable digit
    // Inputs:
    //   Int_t module    // Module number to be simulated
    //   Int_t event     // Event number to be simulated
    // Outputs:
    //   none.
    // Return
    //    none.

    fModule = module;
    fEvent  = event;
    fMapA2->ClearMap();
    fpList->ClearMap();
}
//______________________________________________________________________
void AliITSsimulationSSD::FinishSDigitiseModule(){
    // Does the Sdigits to Digits work
    // Inputs:
    //   none.
    // Outputs:
    //   none.
    // Return:
    //   none.

    FillMapFrompList(fpList);  // need to check if needed here or not????
    SDigitToDigit(fModule,fpList);
    fpList->ClearMap();
    fMapA2->ClearMap();
}
//______________________________________________________________________
void AliITSsimulationSSD::DigitiseModule(AliITSmodule *mod,
                                         Int_t dummy0,Int_t dummy1) {
  // Digitizes hits for one SSD module
  Int_t module     = mod->GetIndex();

  HitsToAnalogDigits(mod,fpList);
  SDigitToDigit(module,fpList);

  fpList->ClearMap();
  fMapA2->ClearMap();
}
//______________________________________________________________________
void AliITSsimulationSSD::SDigitiseModule(AliITSmodule *mod,Int_t dummy0,
                                          Int_t dummy1) {
  // Produces Summable/Analog digits and writes them to the SDigit tree. 

  HitsToAnalogDigits(mod,fpList);

  WriteSDigits(fpList);

  fpList->ClearMap();
  fMapA2->ClearMap();
}
//______________________________________________________________________
void AliITSsimulationSSD::SDigitToDigit(Int_t module,AliITSpList *pList){
  // Takes the pList and finishes the digitization.
                               
  //    FillMapFrompList(pList);  //commented out to avoid double counting of the
                                //charge

  ApplyNoise(pList,module);
  ApplyCoupling(pList,module);

  ChargeToSignal(pList);
}
//______________________________________________________________________
void AliITSsimulationSSD::HitsToAnalogDigits(AliITSmodule *mod,
                                             AliITSpList *pList){
    // Loops over all hits to produce Analog/floating point digits. This
    // is also the first task in producing standard digits.
    Int_t lasttrack     = -2;
    Int_t idtrack       = -2;
    Double_t x0=0.0, y0=0.0, z0=0.0;
    Double_t x1=0.0, y1=0.0, z1=0.0;
    Double_t de=0.0;
    Int_t module = mod->GetIndex();

    TObjArray *hits = mod->GetHits();
    Int_t nhits     = hits->GetEntriesFast();
    if (nhits<=0) return;
    AliITSTableSSD * tav = new AliITSTableSSD(GetNStrips());
    module = mod->GetIndex();
    if ( mod->GetLayer() == 6 ) GetSegmentation()->SetLayer(6);
    if ( mod->GetLayer() == 5 ) GetSegmentation()->SetLayer(5);
    for(Int_t i=0; i<nhits; i++) {    
	// LineSegmentL returns 0 if the hit is entering
	// If hits is exiting returns positions of entering and exiting hits
	// Returns also energy loss
//	cout << i << " ";
//	cout << mod->GetHit(i)->GetXL() << " "<<mod->GetHit(i)->GetYL();
//	cout << " " << mod->GetHit(i)->GetZL();
//	cout << endl;
	if (mod->LineSegmentL(i, x0, x1, y0, y1, z0, z1, de, idtrack)) {
	    HitToDigit(module, x0, y0, z0, x1, y1, z1, de,tav);
	    if (lasttrack != idtrack || i==(nhits-1)) {
		GetList(idtrack,i,module,pList,tav);
	    } // end if
	    lasttrack=idtrack;
	} // end if
    }  // end loop over hits
    delete tav; tav=0;
    return;
}
//----------------------------------------------------------------------
void AliITSsimulationSSD::HitToDigit(Int_t module, Double_t x0, Double_t y0, 
                                     Double_t z0, Double_t x1, Double_t y1, 
                                     Double_t z1, Double_t de,
                                     AliITSTableSSD *tav) {
    // Turns hits in SSD module into one or more digits.
    Float_t tang[2] = {0.0,0.0};
    GetSegmentation()->Angles(tang[0], tang[1]);//stereo<<->tan(stereo)~=stereo
    Double_t x, y, z;
    Double_t dex=0.0, dey=0.0, dez=0.0; 
    Double_t pairs; // pair generation energy per step.
    Double_t sigma[2] = {0.,0.};// standard deviation of the diffusion gaussian
    Double_t tdrift[2] = {0.,0.}; // time of drift
    Double_t w;
    Double_t inf[2], sup[2], par0[2];                 

    // Steps in the module are determined "manually" (i.e. No Geant)
    // NumOfSteps divide path between entering and exiting hits in steps 
    Int_t numOfSteps = NumOfSteps(x1, y1, z1, dex, dey, dez);
    // Enery loss is equally distributed among steps
    de    = de/numOfSteps;
    pairs = de/GetIonizeE(); // e-h pairs generated
    for(Int_t j=0; j<numOfSteps; j++) {     // stepping
	x = x0 + (j+0.5)*dex;
	y = y0 + (j+0.5)*dey;
	if ( y > (GetSegmentation()->Dy()/2+10)*1.0E-4 ) {
	    // check if particle is within the detector
	    Warning("HitToDigit","hit out of detector y0=%e,y=%e,dey=%e,j =%e",
		    y0,y,dey,j);
	    return;
	} // end if
	z = z0 + (j+0.5)*dez;
//	cout <<"HitToDigit "<<x<<" "<<y<<" "<<z<< " "<<dex<<" "<<dey<<" "<<dez<<endl;
	// calculate drift time
	// y is the minimum path
	tdrift[0] = (y+(GetSegmentation()->Dy()*1.0E-4)/2)/GetDriftVelocity(0);
	tdrift[1] = ((GetSegmentation()->Dy()*1.0E-4)/2-y)/GetDriftVelocity(1);

	for(Int_t k=0; k<2; k++) {   // both sides    remember: 0=Pside 1=Nside

	    tang[k]=TMath::Tan(tang[k]);

	    // w is the coord. perpendicular to the strips
	    /*
	    if(k==0) {
		w = (x+(GetSegmentation()->Dx()*1.0E-4)/2) -
		    (z+(GetSegmentation()->Dz()*1.0E-4)/2)*tang[k]; 
	    }else{
		w = (x+(GetSegmentation()->Dx()*1.0E-4)/2) + 
		    (z-(GetSegmentation()->Dz()*1.0E-4)/2)*tang[k];
	    } // end if
	    w /= (GetStripPitch()*1.0E-4); // w is converted in units of pitch
	    */
	    { // replacement block for the above.
		Float_t xp=x*1.e+4,zp=z*1.e+4; // microns
		GetSegmentation()->GetPadTxz(xp,zp);
		if(k==0) w = xp; // P side strip number
		else w = zp; // N side strip number
	    } // end test block

	    if((w<(-0.5)) || (w>(GetNStrips()-0.5))) {
		// this check rejects hits in regions not covered by strips
		// 0.5 takes into account boundaries 
		//cout << "x,z="<<x<<","<<z<<" w="<<w<<" Nstrips="<<GetNStrips()<<endl;
		return; // There are dead region on the SSD sensitive volume.
	    } // end if

	    // sigma is the standard deviation of the diffusion gaussian
	    if(tdrift[k]<0) return;
	    sigma[k] = TMath::Sqrt(2*GetDiffConst(k)*tdrift[k]);
	    sigma[k] /= (GetStripPitch()*1.0E-4);  //units of Pitch
	    if(sigma[k]==0.0) { 	
		Error("HitToDigit"," sigma[%d]=0",k);
		exit(0);
	    } // end if

	    par0[k] = pairs;
	    // we integrate the diffusion gaussian from -3sigma to 3sigma 
	    inf[k] = w - 3*sigma[k]; // 3 sigma from the gaussian average  
	    sup[k] = w + 3*sigma[k]; // 3 sigma from the gaussian average
	    // IntegrateGaussian does the actual
	    // integration of diffusion gaussian
	    IntegrateGaussian(k, par0[k], w, sigma[k], inf[k], sup[k],tav);
	}  // end for loop over side (0=Pside, 1=Nside)      
    } // end stepping
}
//______________________________________________________________________
void AliITSsimulationSSD::ApplyNoise(AliITSpList *pList,Int_t module){
  // Apply Noise.
  Int_t    k,ix;
  Double_t signal,noise;
  Double_t noiseP[2] = {0.,0.};
  Float_t a,b;

  fResponse->GetNoiseParam(a,b); // retrieves noise parameters
  noiseP[0] = (Double_t) a; noiseP[1] = (Double_t) b;
  for(k=0;k<2;k++){                    // both sides (0=Pside, 1=Nside)
	for(ix=0;ix<GetNStrips();ix++){      // loop over strips
	    noise  = gRandom->Gaus(0,noiseP[k]);// get noise to signal
	    signal = noise + fMapA2->GetSignal(k,ix);//get signal from map
	    if(signal<0.) signal=0.0;           // in case noise is negative...
	    fMapA2->SetHit(k,ix,signal); // give back signal to map
	    if(signal>0.0) pList->AddNoise(k,ix,module,noise);
	} // loop over strip 
  } // loop over k (P or N side)
}
//______________________________________________________________________
void AliITSsimulationSSD::ApplyCoupling(AliITSpList *pList,Int_t module) {
  // Apply the effect of electronic coupling between channels
  Int_t ix;
  Double_t signalLeft=0, signalRight=0,signal=0;

  for(ix=0;ix<GetNStrips();ix++){
	// P side coupling
	if(ix>0.)signalLeft = fMapA2->GetSignal(0,ix-1)*fDCS->GetCouplingPL();
	else signalLeft = 0.0;
	if(ix<(GetNStrips()-1)) signalRight = fMapA2->GetSignal(0,ix+1)*
                              fDCS->GetCouplingPR();
	else signalRight = 0.0;
	signal = signalLeft + signalRight;
	fMapA2->AddSignal(0,ix,signal);
	if(signal>0.0) pList->AddNoise(0,ix,module,signal);

	signalLeft = signalRight = signal = 0.0;
	// N side coupling
	if(ix>0.) signalLeft = fMapA2->GetSignal(1,ix-1)*fDCS->GetCouplingNL();
	else signalLeft = 0.0;
	if(ix<(GetNStrips()-1)) signalRight = fMapA2->GetSignal(1,ix+1)*
                              fDCS->GetCouplingNR();
	else signalRight = 0.0;
	signal = signalLeft + signalRight;
	fMapA2->AddSignal(1,ix,signal);
	if(signal>0.0) pList->AddNoise(1,ix,module,signal);
  } // loop over strips 
}
//______________________________________________________________________
Float_t AliITSsimulationSSD::F(Float_t av, Float_t x, Float_t s) {
  // Computes the integral of a gaussian using Error Function
  Float_t sqrt2 = TMath::Sqrt(2.0);
  Float_t sigm2 = sqrt2*s;
  Float_t integral;

  integral = 0.5 * TMath::Erf( (x - av) / sigm2);
  return integral;
}
//______________________________________________________________________
void AliITSsimulationSSD::IntegrateGaussian(Int_t k,Double_t par, Double_t w,
                                            Double_t sigma, 
                                            Double_t inf, Double_t sup,
                                            AliITSTableSSD *tav) {
  // integrate the diffusion gaussian
  // remind: inf and sup are w-3sigma and w+3sigma
  //         we could define them here instead of passing them
  //         this way we are free to introduce asimmetry

  Double_t a=0.0, b=0.0;
  Double_t dXCharge1 = 0.0, dXCharge2 = 0.0;
  // dXCharge1 and 2 are the charge to two neighbouring strips
  // Watch that we only involve at least two strips
  // Numbers greater than 2 of strips in a cluster depend on
  //  geometry of the track and delta rays, not charge diffusion!   
  
  Double_t strip = TMath::Floor(w);         // closest strip on the left

  if ( TMath::Abs((strip - w)) < 0.5) { 
      // gaussian mean is closer to strip on the left
      a = inf;                         // integration starting point
      if((strip+0.5)<=sup) {
	  // this means that the tail of the gaussian goes beyond
	  // the middle point between strips ---> part of the signal
	  // is given to the strip on the right
	  b = strip + 0.5;               // integration stopping point
	  dXCharge1 = F( w, b, sigma) - F(w, a, sigma);
	  dXCharge2 = F( w, sup, sigma) - F(w ,b, sigma); 
      }else { 
	  // this means that all the charge is given to the strip on the left
	  b = sup;
	  dXCharge1 = 0.9973;   // gaussian integral at 3 sigmas
	  dXCharge2 = 0.0;
      } // end if
      dXCharge1 = par * dXCharge1;// normalize by mean of number of carriers
      dXCharge2 = par * dXCharge2;

      // for the time being, signal is the charge
      // in ChargeToSignal signal is converted in ADC channel
      fMapA2->AddSignal(k,(Int_t)strip,dXCharge1);
      tav->Add(k,(Int_t)strip);
      if(((Int_t) strip) < (GetNStrips()-1)) {
	  // strip doesn't have to be the last (remind: last=GetNStrips()-1)
	  // otherwise part of the charge is lost
	  fMapA2->AddSignal(k,((Int_t)strip+1),dXCharge2);
	  tav->Add(k,((Int_t)(strip+1)));
      } // end if
  }else{
      // gaussian mean is closer to strip on the right
      strip++;     // move to strip on the rigth
      b = sup;     // now you know where to stop integrating
      if((strip-0.5)>=inf) { 
	  // tail of diffusion gaussian on the left goes left of
	  // middle point between strips
	  a = strip - 0.5;        // integration starting point
	  dXCharge1 = F(w, b, sigma) - F(w, a, sigma);
	  dXCharge2 = F(w, a, sigma) - F(w, inf, sigma);
      }else {
	  a = inf;
	  dXCharge1 = 0.9973;   // gaussian integral at 3 sigmas
	  dXCharge2 = 0.0;
      } // end if
      dXCharge1 = par * dXCharge1;    // normalize by means of carriers
      dXCharge2 = par * dXCharge2;
      // for the time being, signal is the charge
      // in ChargeToSignal signal is converted in ADC channel
      fMapA2->AddSignal(k,(Int_t)strip,dXCharge1);
      tav->Add(k,(Int_t)strip);
      if(((Int_t) strip) > 0) {
	  // strip doesn't have to be the first
	  // otherwise part of the charge is lost
	  fMapA2->AddSignal(k,((Int_t)strip-1),dXCharge2);
	  tav->Add(k,((Int_t)(strip-1)));
      } // end if
  } // end if
}
//______________________________________________________________________
Int_t AliITSsimulationSSD::NumOfSteps(Double_t x, Double_t y, Double_t z,
                                      Double_t & dex,Double_t & dey,Double_t & dez){
  // number of steps
  // it also returns steps for each coord
  //AliITSsegmentationSSD *seg = new AliITSsegmentationSSD();

  Double_t step = 25E-4;
  //step = (Double_t) seg->GetStepSize();  // step size (cm)
  Int_t numOfSteps = (Int_t) (TMath::Sqrt(x*x+y*y+z*z)/step); 

  if (numOfSteps < 1) numOfSteps = 1;       // one step, at least

  // we could condition the stepping depending on the incident angle
  // of the track
  dex = x/numOfSteps;
  dey = y/numOfSteps;
  dez = z/numOfSteps;

  return numOfSteps;
}
//----------------------------------------------------------------------
void AliITSsimulationSSD::GetList(Int_t label,Int_t hit,Int_t mod,
                                  AliITSpList *pList,AliITSTableSSD *tav) {
  // loop over nonzero digits
  Int_t ix,i;
  Double_t signal=0.;

  for(Int_t k=0; k<2; k++) {
    ix=tav->Use(k);
    while(ix>-1){
      signal = fMapA2->GetSignal(k,ix);
      if(signal==0.0) {
        ix=tav->Use(k);
        continue;
      } // end if signal==0.0
      // check the signal magnitude
      for(i=0;i<pList->GetNSignals(k,ix);i++){
        signal -= pList->GetTSignal(k,ix,i);
      } // end for i
      //  compare the new signal with already existing list
      if(signal>0)pList->AddSignal(k,ix,label,hit,mod,signal);
      ix=tav->Use(k);
    } // end of loop on strips
  } // end of loop on P/N side
  tav->Clear();
}
//----------------------------------------------------------------------
void AliITSsimulationSSD::ChargeToSignal(AliITSpList *pList) {
  // charge to signal
  static AliITS *aliITS = (AliITS*)gAlice->GetModule("ITS");
  Float_t threshold = 0.;
  Int_t size = AliITSdigitSSD::GetNTracks();
  Int_t * digits = new Int_t[size];
  Int_t * tracks = new Int_t[size];
  Int_t * hits = new Int_t[size];
  Int_t j1;
  Float_t charges[3] = {0.0,0.0,0.0};
  Float_t signal;
  Float_t noise[2] = {0.,0.};

  ((AliITSresponseSSD*)fResponse)->GetNoiseParam(noise[0],noise[1]);

  for(Int_t k=0;k<2;k++){         // both sides (0=Pside, 1=Nside)
	// Threshold for zero-suppression
	// It can be defined in AliITSresponseSSD
	//             threshold = (Float_t)fResponse->MinVal(k);
	// I prefer to think adjusting the threshold "manually", looking
	// at the scope, and considering noise standard deviation
	threshold = 4.0*noise[k]; // 4 times noise is a choice
	for(Int_t ix=0;ix<GetNStrips();ix++){     // loop over strips
	    if(fMapA2->GetSignal(k,ix) <= threshold)continue;
	    // convert to ADC signal
	    signal = ((AliITSresponseSSD*)fResponse)->DEvToADC(
                                                      fMapA2->GetSignal(k,ix));
	    if(signal>1024.) signal = 1024.;//if exceeding, accumulate last one
	    digits[0] = k;
	    digits[1] = ix;
	    digits[2] = (Int_t) signal;
	    for(j1=0;j1<size;j1++)if(j1<pList->GetNEnteries()){
		// only three in digit.
		tracks[j1]  = pList->GetTrack(k,ix,j1);
		hits[j1]    = pList->GetHit(k,ix,j1);
	    }else{
		tracks[j1]  = -3;
		hits[j1]    = -1;
	    } // end for j1
	    // finally add digit
	    aliITS->AddSimDigit(2,0,digits,tracks,hits,charges);
	} // end for ix
  } // end for k
  delete [] digits;
  delete [] tracks;
  delete [] hits;
}
//______________________________________________________________________
void AliITSsimulationSSD::WriteSDigits(AliITSpList *pList){
  // Fills the Summable digits Tree
  Int_t i,ni,j,nj;
  static AliITS *aliITS = (AliITS*)gAlice->GetModule("ITS");

  pList->GetMaxMapIndex(ni,nj);
  for(i=0;i<ni;i++)for(j=0;j<nj;j++){
      if(pList->GetSignalOnly(i,j)>0.0){
	  aliITS->AddSumDigit(*(pList->GetpListItem(i,j)));
//	    cout << "pListSSD: " << *(pList->GetpListItem(i,j)) << endl;
      } // end if
  } // end for i,j
  return;
}
//______________________________________________________________________
void AliITSsimulationSSD::FillMapFrompList(AliITSpList *pList){
  // Fills fMap2A from the pList of Summable digits
  Int_t k,ix;

  for(k=0;k<2;k++)for(ix=0;ix<GetNStrips();ix++) 
	fMapA2->AddSignal(k,ix,pList->GetSignal(k,ix));
  return;
}
//______________________________________________________________________
void AliITSsimulationSSD::Print(ostream *os){
  //Standard output format for this class

  //AliITSsimulation::Print(os);
  *os << fIonE <<",";
  *os << fDifConst[0] <<","<< fDifConst[1] <<",";
  *os << fDriftVel[0] <<","<< fDriftVel[1];
  //*os <<","; fDCS->Print(os);
  //*os <<","; fMapA2->Print(os);
}
//______________________________________________________________________
void AliITSsimulationSSD::Read(istream *is){
  // Standard output streaming function.

  //AliITSsimulation::Read(is);
  *is >> fIonE;
  *is >> fDifConst[0] >> fDifConst[1];
  *is >> fDriftVel[0] >> fDriftVel[1];
  //fDCS->Read(is);
  //fMapA2->Read(is);
}
//______________________________________________________________________
ostream &operator<<(ostream &os,AliITSsimulationSSD &source){
  // Standard output streaming function.

  source.Print(&os);
  return os;
}
//______________________________________________________________________
istream &operator>>(istream &os,AliITSsimulationSSD &source){
  // Standard output streaming function.

  source.Read(&os);
  return os;
}
//______________________________________________________________________