Adding drift lignth correction for Time of Flight

[u/mrichter/AliRoot.git] / TPC / AliTPCTransform.cxx

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//-------------------------------------------------------
//          Implementation of the TPC transformation class
//
//   Origin: Marian Ivanov   Marian.Ivanov@cern.ch
//           Magnus Mager
//
//   Class for tranformation of the coordinate frame
//   Transformation  
//    local coordinate frame (sector, padrow, pad, timebine) ==>
//    rotated global (tracking) cooridnate frame (sector, lx,ly,lz)
//
//    Unisochronity  - (substract time0 - pad by pad)
//    Drift velocity - Currently common drift velocity - functionality of AliTPCParam
//    ExB effect     - 
//
//    Usage:
//          AliTPCclustererMI::AddCluster
//          AliTPCtrackerMI::Transform
//    
//-------------------------------------------------------

/* To test it:
   cdb=AliCDBManager::Instance()
   cdb->SetDefaultStorage("local:///u/mmager/mycalib1")
   c=AliTPCcalibDB::Instance()
   c->SetRun(0)
   Double_t x[]={1.0,2.0,3.0}
   Int_t i[]={4}
   AliTPCTransform trafo
   trafo.Transform(x,i,0,1)
 */

/* $Id$ */

#include "AliTPCROC.h"
#include "AliTPCCalPad.h"
#include "AliTPCCalROC.h"
#include "AliTPCcalibDB.h"
#include "AliTPCParam.h"
#include "TMath.h"
#include "AliLog.h"
#include "AliTPCExB.h"
#include "TGeoMatrix.h"
#include "AliTPCTransform.h"

ClassImp(AliTPCTransform)


AliTPCTransform::AliTPCTransform() {
  //
  // Speed it up a bit!
  //
  for (Int_t i=0;i<18;++i) {
    Double_t alpha=TMath::DegToRad()*(10.+20.*(i%18));
    fSins[i]=TMath::Sin(alpha);
    fCoss[i]=TMath::Cos(alpha);
  }
}

AliTPCTransform::~AliTPCTransform() {
  //
  // Destructor
  //
}

void AliTPCTransform::Transform(Double_t *x,Int_t *i,UInt_t /*time*/,
				Int_t /*coordinateType*/, Float_t *primvtx) {
  // input: x[0] - pad row
  //        x[1] - pad 
  //        x[2] - time in us
  //        i[0] - sector
  // output: x[0] - x (all in the rotated global coordinate frame)
  //         x[1] - y
  //         x[2] - z
  //
  //  primvtx     - position of the primary vertex
  //                used for the TOF correction
  //                TOF of particle calculated assuming the speed-of-light and 
  //                line approximation  
  //
  

  Int_t row=TMath::Nint(x[0]);
  Int_t pad=TMath::Nint(x[1]);
  Int_t sector=i[0];
  AliTPCcalibDB*  calib=AliTPCcalibDB::Instance();
  //
  AliTPCCalPad * time0TPC = calib->GetPadTime0(); 
  AliTPCParam  * param    = calib->GetParameters(); 
  if (!time0TPC){
    AliFatal("Time unisochronity missing");
  }

  if (!param){
    AliFatal("Parameters missing");
  }

  Double_t xx[3];
  //  Apply Time0 correction - Pad by pad fluctuation
  //
  x[2]-=time0TPC->GetCalROC(sector)->GetValue(row,pad);
  //
  // Tranform from pad - time coordinate system to the rotated global (tracking) system
  //
  Local2RotatedGlobal(sector,x);
  //
  //
  //
  // Alignment
  //TODO:  calib->GetParameters()->GetClusterMatrix(sector)->LocalToMaster(x,xx);
  RotatedGlobal2Global(sector,x);
  //
  //
  // ExB correction
  //
  calib->GetExB()->Correct(x,xx);
  //
  // Time of flight correction
  //
  Float_t deltaDr =0
  if (primvtx){
    Float_t dist=0;
    dist+=(primvtx[0]-x[0])*(primvtx[0]-x[0]);
    dist+=(primvtx[1]-x[1])*(primvtx[1]-x[1]);
    dist+=(primvtx[0]-x[2])*(primvtx[0]-x[2]);
    dist = TMath::Sqrt(dist);
    // drift length correction because of TOF
    // the drift velocity is in cm/s therefore multiplication by 0.01
    deltaDr = (dist*(0.01*param->GetDriftV()))/TMath::C();
  }
  xx[2]-=deltaDr;
  //
  Global2RotatedGlobal(sector,xx);

  x[0]=xx[0];x[1]=xx[1];x[2]=xx[2];
}

void AliTPCTransform::Local2RotatedGlobal(Int_t sector, Double_t *x) const {
  //
  //  
  // Tranform coordinate from  
  // row, pad, time to x,y,z
  //
  // Drift Velocity 
  // Current implementation - common drift velocity - for full chamber
  // TODO: use a map or parametrisation!
  //
  //  
  //
  AliTPCcalibDB*  calib=AliTPCcalibDB::Instance();
  AliTPCParam  * param    = calib->GetParameters(); 
  if (!param){
    AliFatal("Parameters missing");
  }
  Int_t row=TMath::Nint(x[0]);
  Int_t pad=TMath::Nint(x[1]);
  //
  const Int_t kNIS=param->GetNInnerSector(), kNOS=param->GetNOuterSector();
  Double_t sign = 1.;
  Double_t zwidth    = param->GetZWidth();
  Double_t padWidth  = 0;
  Double_t padLength = 0;
  Double_t    maxPad    = 0;
  //
  if (sector < kNIS) {
    maxPad = param->GetNPadsLow(row);
    sign = (sector < kNIS/2) ? 1 : -1;
    padLength = param->GetPadPitchLength(sector,row);
    padWidth = param->GetPadPitchWidth(sector);
  } else {
    maxPad = param->GetNPadsUp(row);
    sign = ((sector-kNIS) < kNOS/2) ? 1 : -1;
    padLength = param->GetPadPitchLength(sector,row);
    padWidth  = param->GetPadPitchWidth(sector);
  }
  //
  // X coordinate
  x[0] = param->GetPadRowRadii(sector,row);  // padrow X position - ideal
  //
  // Y coordinate
  //
  x[1]=(x[1]-0.5*maxPad)*padWidth;
  //
  // Z coordinate
  //
  x[2]*= zwidth;  // tranform time bin to the distance to the ROC
  x[2]-= 3.*param->GetZSigma() + param->GetNTBinsL1()*zwidth;
  // subtract the time offsets
  x[2] = sign*( param->GetZLength(sector) - x[2]);
}

inline void AliTPCTransform::RotatedGlobal2Global(Int_t sector,Double_t *x) const {
  //
  // transform possition rotated global to the global
  //
  Double_t cos,sin;
  GetCosAndSin(sector,cos,sin);
  Double_t tmp=x[0];
  x[0]= cos*tmp+sin*x[1];
  x[1]=-sin*tmp+cos*x[1];
}

inline void AliTPCTransform::Global2RotatedGlobal(Int_t sector,Double_t *x) const {
  //
  // tranform possition Global2RotatedGlobal
  //
  Double_t cos,sin;
  GetCosAndSin(sector,cos,sin);
  Double_t tmp=x[0];
  x[0]= cos*tmp-sin*x[1];
  x[1]= sin*tmp+cos*x[1];
}

inline void AliTPCTransform::GetCosAndSin(Int_t sector,Double_t &cos,
					  Double_t &sin) const {
  cos=fCoss[sector%18];
  sin=fSins[sector%18];
}