In the STepManager fluctuations due to light collection and attenuation has been...

[u/mrichter/AliRoot.git] / EMCAL / AliEMCALv1.cxx

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 * Author: The ALICE Off-line Project.                                    *
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 * documentation strictly for non-commercial purposes is hereby granted   *
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 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

/* $Id$ */

//_________________________________________________________________________
// Implementation version v1 of EMCAL Manager class 
// An object of this class does not produce digits
// It is the one to use if you do want to produce outputs in TREEH 
//                  
//*-- Author: Sahal Yacoob (LBL /UCT)
//*--       : Jennifer Klay (LBL)

// This Class not stores information on all particles prior to EMCAL entry - in order to facilitate analysis.
// This is done by setting fIShunt =2, and flagging all parents of particles entering the EMCAL.

// 15/02/2002 .... Yves Schutz
//  1. fSamplingFraction and fLayerToPreshowerRatio have been removed
//  2. Timing signal is collected and added to hit

// --- ROOT system ---
#include "TPGON.h"
#include "TTUBS.h"
#include "TNode.h"
#include "TRandom.h"
#include "TTree.h"
#include "TGeometry.h"
#include "TParticle.h"

// --- Standard library ---

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <strstream.h>
#include <iostream.h>
#include <math.h>
// --- AliRoot header files ---

#include "AliEMCALv1.h"
#include "AliEMCALHit.h"
#include "AliEMCALGeometry.h"
#include "AliConst.h"
#include "AliRun.h"
#include "AliMC.h"

ClassImp(AliEMCALv1)


//______________________________________________________________________
AliEMCALv1::AliEMCALv1():AliEMCALv0(){
  // ctor
    fLightYieldMean = 0 ; 
    fIntrinsicAPDEfficiency = fLightFactor = fLightYieldAttenuation =   fAPDFactor = fAPDGain = fRecalibrationFactor = fAPDFactor = 0. ; 
}

//______________________________________________________________________
AliEMCALv1::AliEMCALv1(const char *name, const char *title):
    AliEMCALv0(name,title){
    // Standard Creator.

    fHits= new TClonesArray("AliEMCALHit",1000);
    gAlice->AddHitList(fHits);

    fNhits = 0;
    fIshunt     =  2; // All hits are associated with particles entering the calorimeter

    //Photoelectron statistics:
    // The light yield is a poissonian distribution of the number of
    // photons created in a plastic layer, calculated using following formula
    // NumberOfPhotons = EnergyLost * LightYieldMean* APDEfficiency *
    //              exp (-LightYieldAttenuation * DistanceToPINdiodeFromTheHit)
    // LightYieldMean is parameter calculated to be over 100000 photons per GeV (a guess)
    // APDEfficiency is 0.02655
    // fLightYieldAttenuation is 0.0045 a guess
    // TO BE FIXED
    //***** Need a method in geometry to retrieve the fiber length corresponding to each layer
    //***** See the step manager for the light attenuation calculation 
    // The number of electrons created in the APD is
    // NumberOfElectrons = APDGain * LightYield
    // The APD Gain is 300
    
    fLightYieldMean         = 10000000.;  // This is a guess
    fIntrinsicAPDEfficiency = 0.02655 ;
    fLightFactor            = fLightYieldMean * fIntrinsicAPDEfficiency ; 
    fLightYieldAttenuation  = 0.0045 ; // an other guess 
    fAPDGain                = 300. ;
    fRecalibrationFactor    = 13.418/ fLightYieldMean ;
    fAPDFactor              = (fRecalibrationFactor/100.) * fAPDGain ; 

}

//______________________________________________________________________
AliEMCALv1::~AliEMCALv1(){
    // dtor

    if ( fHits) {
	fHits->Delete();
	delete fHits;
	fHits = 0;
    }
}
//______________________________________________________________________
void AliEMCALv1::AddHit(Int_t shunt, Int_t primary, Int_t tracknumber, Int_t iparent, Float_t ienergy, 
			Int_t id, Float_t * hits,Float_t * p){
    // Add a hit to the hit list.
    // An EMCAL hit is the sum of all hits in a single segment 
    //   originating from the same enterring particle 
    Int_t hitCounter;
    
    AliEMCALHit *newHit;
    AliEMCALHit *curHit;
    Bool_t deja = kFALSE;

    newHit = new AliEMCALHit(shunt, primary, tracknumber, iparent, ienergy, id, hits, p);
    for ( hitCounter = fNhits-1; hitCounter >= 0 && !deja; hitCounter-- ) {
	curHit = (AliEMCALHit*) (*fHits)[hitCounter];
	// We add hits with the same tracknumber, while GEANT treats
	// primaries succesively
	if(curHit->GetPrimary() != primary) break;
	if( *curHit == *newHit ) {
	    *curHit = *curHit + *newHit;
	    deja = kTRUE;
	} // end if
    } // end for hitCounter

    if ( !deja ) {
	new((*fHits)[fNhits]) AliEMCALHit(*newHit);
	fNhits++;
    } // end if

    delete newHit;
}
//______________________________________________________________________
void AliEMCALv1::StepManager(void){
  // Accumulates hits as long as the track stays in a single
  // crystal or PPSD gas Cell

  Int_t          id[2];           // (layer, phi, Eta) indices
  Int_t          absid;
  // position wrt MRS and energy deposited
  Float_t        xyzte[5]={0.,0.,0.,0.,0.};// position wrt MRS, time and energy deposited
  Float_t        pmom[4]={0.,0.,0.,0.};
  TLorentzVector pos; // Lorentz vector of the track current position.
  TLorentzVector mom; // Lorentz vector of the track current momentum.
  Int_t tracknumber =  gAlice->CurrentTrack();
  Int_t primary = 0;
  static Int_t iparent = 0;
  static Float_t ienergy = 0;
  Int_t copy = 0;
  
  if(gMC->IsTrackEntering() && (strcmp(gMC->CurrentVolName(),"XALU") == 0)){ // This Particle in enterring the Calorimeter
    gMC->TrackPosition(pos) ;
    xyzte[0] = pos[0] ;
    xyzte[1] = pos[1] ;
    xyzte[2] = pos[2] ;
    if ( (xyzte[0]*xyzte[0] + xyzte[1]*xyzte[1])  
	 <  (fGeom->GetEnvelop(0)+fGeom->GetGap2Active()+1.5 )*(fGeom->GetEnvelop(0)+fGeom->GetGap2Active()+1.5 ) ) {
      iparent = tracknumber;
      gMC->TrackMomentum(mom);
      ienergy = mom[3]; 
      TParticle * part = 0 ;
      Int_t parent = iparent ;
      while ( parent != -1 ) { // <------------- flags this particle to be kept and
	//all the ancestors of this particle
	part = gAlice->Particle(parent) ;
	part->SetBit(kKeepBit);
	parent = part->GetFirstMother() ;
      }
    }
  }
  if(gMC->CurrentVolID(copy) == gMC->VolId("XPHI") ) { // We are in a Scintillator Layer 
    
    Float_t depositedEnergy ; 
    
    if( (depositedEnergy = gMC->Edep()) > 0.){// Track is inside a scintillator and deposits some energy
      
      gMC->TrackPosition(pos);
      xyzte[0] = pos[0];
      xyzte[1] = pos[1];
      xyzte[2] = pos[2];
      xyzte[3] = gMC->TrackTime() ;       
      
      gMC->TrackMomentum(mom);
      pmom[0] = mom[0];
      pmom[1] = mom[1];
      pmom[2] = mom[2];
      pmom[3] = mom[3];
      
      gMC->CurrentVolOffID(1, id[0]); // get the POLY copy number;
      gMC->CurrentVolID(id[1]); // get the phi number inside the layer
      absid = (id[0]-1)*(fGeom->GetNPhi()) + id[1];
      
      //Calculates the light yield, the number of photons produced in the
      //plastic layer 
      // Here we need to know the fiber lebgth to calculate the attenuation
     
      Float_t lengthOfFiber = 0. ;// should be retrieved from the geometry

      Float_t lightYield = gRandom->Poisson(fLightFactor * depositedEnergy *
					    exp(-fLightYieldAttenuation * lengthOfFiber)) ;
      xyzte[4] = fAPDFactor * lightYield  ;
   
      primary = gAlice->GetPrimary(tracknumber);
      AddHit(fIshunt, primary,tracknumber, iparent, ienergy, absid, xyzte, pmom);
    } // there is deposited energy
  }
}