HMPID/AliHMPIDRecon.cxx

   1 /**************************************************************************
   2  * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
   3  *                                                                        *
   4  * Author: The ALICE Off-line Project.                                    *
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  15
  16 //////////////////////////////////////////////////////////////////////////
  17 //                                                                      //
  18 // AliHMPIDRecon                                                         //
  19 //                                                                      //
  20 // HMPID class to perfom pattern recognition based on Hough transfrom    //
  21 // for single chamber                                                   //
  22 //////////////////////////////////////////////////////////////////////////
  23
  24 #include "AliHMPIDRecon.h"   //class header
  25 #include "AliHMPIDCluster.h" //CkovAngle()
  26 #include <TRotation.h>       //TracePhot()
  27 #include <TH1D.h>            //HoughResponse()
  28 #include <TClonesArray.h>    //CkovAngle()
  29 #include <AliESDtrack.h>     //CkovAngle()
  30
  31 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  32 AliHMPIDRecon::AliHMPIDRecon():
  33   TTask("RichRec","RichPat"),
  34   fPhotCnt(-1),
  35   fPhotFlag(0x0),
  36   fPhotCkov(0x0),
  37   fPhotPhi(0x0),
  38   fPhotWei(0x0),
  39   fCkovSigma2(0),
  40   fIsWEIGHT(kFALSE),
  41   fDTheta(0.001),
  42   fWindowWidth(0.045),
  43   fRingArea(0),
  44   fRingAcc(0),
  45   fTrkDir(0,0,1),  // Just for test
  46   fTrkPos(30,40),  // Just for test
  47   fMipPos(0,0),
  48   fPc(0,0),
  49   fParam(AliHMPIDParam::Instance())
  50 {
  51 //..
  52 //init of data members
  53 //..
  54
  55   fParam->SetRefIdx(fParam->MeanIdxRad()); // initialization of ref index to a default one
  56 }
  57 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  58 void AliHMPIDRecon::InitVars(Int_t n)
  59 {
  60 //..
  61 //Init some variables
  62 //..
  63   if(n<0) return;
  64   fPhotFlag = new Int_t[n];
  65   fPhotCkov = new Double_t[n];
  66   fPhotPhi  = new Double_t[n];
  67   fPhotWei  = new Double_t[n];
  68 //
  69 }
  70 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  71 void AliHMPIDRecon::DeleteVars()const
  72 {
  73 //..
  74 //Delete variables
  75 //..
  76   delete fPhotFlag;
  77   delete fPhotCkov;
  78   delete fPhotPhi;
  79   delete fPhotWei;
  80 }
  81 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  82 void AliHMPIDRecon::CkovAngle(AliESDtrack *pTrk,TClonesArray *pCluLst,Double_t nmean,Double_t qthre)
  83 {
  84 // Pattern recognition method based on Hough transform
  85 // Arguments:   pTrk     - track for which Ckov angle is to be found
  86 //              pCluLst  - list of clusters for this chamber
  87 //   Returns:            - track ckov angle, [rad],
  88
  89
  90   const Int_t nMinPhotAcc = 3;                      // Minimum number of photons required to perform the pattern recognition
  91
  92
  93   Int_t nClusTot = pCluLst->GetEntries();
  94   if(nClusTot>fParam->MultCut()) fIsWEIGHT = kTRUE; // offset to take into account bkg in reconstruction
  95   else                           fIsWEIGHT = kFALSE;
  96
  97   InitVars(nClusTot);
  98
  99   Float_t xRa,yRa,th,ph;
 100   pTrk->GetHMPIDtrk(xRa,yRa,th,ph);        //initialize this track: th and ph angles at middle of RAD
 101   SetTrack(xRa,yRa,th,ph);
 102
 103   fParam->SetRefIdx(nmean);
 104
 105   Float_t dMin=999,mipX=-1,mipY=-1;Int_t chId=-1,mipId=-1,mipQ=-1;
 106   fPhotCnt=0;
 107   for (Int_t iClu=0; iClu<pCluLst->GetEntriesFast();iClu++){//clusters loop
 108     AliHMPIDCluster *pClu=(AliHMPIDCluster*)pCluLst->UncheckedAt(iClu);                       //get pointer to current cluster
 109     chId=pClu->Ch();
 110     if(pClu->Q()>qthre){                                                                      //charge compartible with MIP clusters
 111       Float_t dX=fPc.X()-pClu->X(),dY=fPc.Y()-pClu->Y(),d =TMath::Sqrt(dX*dX+dY*dY);          //distance between current cluster and intersection point
 112       if( d < dMin) {mipId=iClu; dMin=d;mipX=pClu->X();mipY=pClu->Y();mipQ=(Int_t)pClu->Q();} //current cluster is closer, overwrite data for min cluster
 113     }else{                                                                                    //charge compatible with photon cluster
 114       Double_t thetaCer,phiCer;
 115       if(FindPhotCkov(pClu->X(),pClu->Y(),thetaCer,phiCer)){                                  //find ckov angle for this  photon candidate
 116         fPhotCkov[fPhotCnt]=thetaCer;                                                         //actual theta Cerenkov (in TRS)
 117         fPhotPhi [fPhotCnt]=phiCer;                                                           //actual phi   Cerenkov (in TRS): -pi to come back to "unusual" ref system (X,Y,-Z)
 118         //PH        Printf("photon n. %i reconstructed theta = %f",fPhotCnt,fPhotCkov[fPhotCnt]);
 119         fPhotCnt++;                                                                           //increment counter of photon candidates
 120       }
 121     }
 122   }//clusters loop
 123
 124   if(fPhotCnt<=nMinPhotAcc) {                                                                 //no reconstruction with <=3 photon candidates
 125     pTrk->SetHMPIDsignal(kNoPhotAccept);                                                      //set the appropriate flag
 126     pTrk->SetHMPIDmip(mipX,mipY,mipQ,fPhotCnt);                                               //store mip info
 127     pTrk->SetHMPIDcluIdx(-1,-1);                                                              //set index of cluster
 128     return;
 129   }
 130
 131   if(mipId==-1) {
 132     pTrk->SetHMPIDcluIdx(chId,9999);                                                          //set index of cluster
 133     pTrk->SetHMPIDsignal(kMipQdcCut);
 134     return;
 135   }                                                                                           //no clusters with QDC more the threshold at all
 136     pTrk->SetHMPIDcluIdx(chId,mipId);                                                         //set index of cluster
 137     if(dMin>fParam->DistCut()) {pTrk->SetHMPIDsignal(kMipDistCut); return;}                   //closest cluster with enough charge is still too far from intersection
 138
 139   fMipPos.Set(mipX,mipY);
 140
 141
 142 //PATTERN RECOGNITION STARTED:
 143
 144   Int_t iNrec=FlagPhot(HoughResponse());                                                      //flag photons according to individual theta ckov with respect to most probable
 145   pTrk->SetHMPIDmip(mipX,mipY,mipQ,iNrec);                                                    //store mip info
 146
 147   if(iNrec<1){
 148     pTrk->SetHMPIDsignal(kNoPhotAccept);                                                      //no photon candidates are accepted
 149     return;
 150   }
 151   Double_t thetaC = FindRingCkov(pCluLst->GetEntries());                                    //find the best reconstructed theta Cherenkov
 152 //    FindRingGeom(thetaC,2);
 153   pTrk->SetHMPIDsignal(thetaC);                                                             //store theta Cherenkov
 154   pTrk->SetHMPIDchi2(fCkovSigma2);                                                          //store errors squared
 155
 156   DeleteVars();
 157 }//CkovAngle()
 158 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 159 Bool_t AliHMPIDRecon::FindPhotCkov(Double_t cluX,Double_t cluY,Double_t &thetaCer,Double_t &phiCer)
 160 {
 161 // Finds Cerenkov angle  for this photon candidate
 162 // Arguments: cluX,cluY - position of cadidate's cluster
 163 // Returns: Cerenkov angle
 164
 165   TVector3 dirCkov;
 166
 167   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();     //z position of middle of RAD
 168   TVector3 rad(fTrkPos.X(),fTrkPos.Y(),zRad);                        //impact point at middle of RAD
 169   TVector3  pc(cluX,cluY,0.5*fParam->WinThick()+fParam->GapIdx());   //mip at PC
 170   Double_t cluR = TMath::Sqrt((cluX-fTrkPos.X())*(cluX-fTrkPos.X())+
 171                               (cluY-fTrkPos.Y())*(cluY-fTrkPos.Y()));//ref. distance impact RAD-CLUSTER
 172   Double_t phi=(pc-rad).Phi();                                       //phi of photon
 173
 174   Double_t ckov1=0;
 175   Double_t ckov2=0.75+fTrkDir.Theta();                        //start to find theta cerenkov in DRS
 176   const Double_t kTol=0.01;
 177   Int_t iIterCnt = 0;
 178   while(1){
 179     if(iIterCnt>=50) return kFALSE;
 180     Double_t ckov=0.5*(ckov1+ckov2);
 181     dirCkov.SetMagThetaPhi(1,ckov,phi);
 182     TVector2 posC=TraceForward(dirCkov);                      //trace photon with actual angles
 183     Double_t dist=cluR-(posC-fTrkPos).Mod();                  //get distance between trial point and cluster position
 184     if(posC.X()==-999) dist = - 999;                          //total reflection problem
 185     iIterCnt++;                                               //counter step
 186     if     (dist> kTol) ckov1=ckov;                           //cluster @ larger ckov
 187     else if(dist<-kTol) ckov2=ckov;                           //cluster @ smaller ckov
 188     else{                                                     //precision achived: ckov in DRS found
 189       dirCkov.SetMagThetaPhi(1,ckov,phi);                     //
 190       Lors2Trs(dirCkov,thetaCer,phiCer);                       //find ckov (in TRS:the effective Cherenkov angle!)
 191       return kTRUE;
 192     }
 193   }
 194 }//FindPhotTheta()
 195 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 196 TVector2 AliHMPIDRecon::TraceForward(TVector3 dirCkov)const
 197 {
 198   //Trace forward a photon from (x,y) up to PC
 199   // Arguments: dirCkov photon vector in LORS
 200   //   Returns: pos of traced photon at PC
 201
 202   TVector2 pos(-999,-999);
 203   Double_t thetaCer = dirCkov.Theta();
 204   if(thetaCer > TMath::ASin(1./fParam->GetRefIdx())) return pos;          //total refraction on WIN-GAP boundary
 205   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();          //z position of middle of RAD
 206   TVector3  posCkov(fTrkPos.X(),fTrkPos.Y(),zRad);                        //RAD: photon position is track position @ middle of RAD
 207   Propagate(dirCkov,posCkov,           -0.5*fParam->WinThick());          //go to RAD-WIN boundary
 208   Refract  (dirCkov,         fParam->GetRefIdx(),fParam->WinIdx());       //RAD-WIN refraction
 209   Propagate(dirCkov,posCkov,            0.5*fParam->WinThick());          //go to WIN-GAP boundary
 210   Refract  (dirCkov,         fParam->WinIdx(),fParam->GapIdx());          //WIN-GAP refraction
 211   Propagate(dirCkov,posCkov,0.5*fParam->WinThick()+fParam->GapThick());   //go to PC
 212   pos.Set(posCkov.X(),posCkov.Y());
 213   return pos;
 214 }//TraceForward()
 215 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 216 void AliHMPIDRecon::Lors2Trs(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
 217 {
 218   //Theta Cerenkov reconstruction
 219   // Arguments: dirCkov photon vector in LORS
 220   //   Returns: thetaCer of photon in TRS
 221   //              phiCer of photon in TRS
 222 //  TVector3 dirTrk;
 223 //  dirTrk.SetMagThetaPhi(1,fTrkDir.Theta(),fTrkDir.Phi());
 224 //  Double_t thetaCer = TMath::ACos(dirCkov*dirTrk);
 225   TRotation mtheta;   mtheta.RotateY(-fTrkDir.Theta());
 226   TRotation mphi;       mphi.RotateZ(-fTrkDir.Phi());
 227   TRotation mrot=mtheta*mphi;
 228   TVector3 dirCkovTRS;
 229   dirCkovTRS=mrot*dirCkov;
 230   phiCer  = dirCkovTRS.Phi();                                          //actual value of the phi of the photon
 231   thetaCer= dirCkovTRS.Theta();                                        //actual value of thetaCerenkov of the photon
 232 }
 233 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 234 void AliHMPIDRecon::Trs2Lors(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
 235 {
 236   //Theta Cerenkov reconstruction
 237   // Arguments: dirCkov photon vector in TRS
 238   //   Returns: thetaCer of photon in LORS
 239   //              phiCer of photon in LORS
 240   TRotation mtheta;   mtheta.RotateY(fTrkDir.Theta());
 241   TRotation mphi;       mphi.RotateZ(fTrkDir.Phi());
 242   TRotation mrot=mphi*mtheta;
 243   TVector3 dirCkovLORS;
 244   dirCkovLORS=mrot*dirCkov;
 245   phiCer  = dirCkovLORS.Phi();                                          //actual value of the phi of the photon
 246   thetaCer= dirCkovLORS.Theta();                                        //actual value of thetaCerenkov of the photon
 247 }
 248 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 249 void AliHMPIDRecon::FindRingGeom(Double_t ckovAng,Int_t level)
 250 {
 251 // Find area covered in the PC acceptance
 252 // Arguments: ckovAng - cerenkov angle
 253 //            level   - precision in finding area and portion of ring accepted (multiple of 50)
 254 //   Returns: area of the ring in cm^2 for given theta ckov
 255
 256   Int_t kN=50*level;
 257   Int_t nPoints = 0;
 258   Double_t area=0;
 259
 260   Bool_t first=kFALSE;
 261   TVector2 pos1;
 262
 263   for(Int_t i=0;i<kN;i++){
 264    if(!first) {
 265       pos1=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                                    //find a good trace for the first photon
 266      if(pos1.X()==-999) continue;                                                                   //no area: open ring
 267      if(!fParam->IsInside(pos1.X(),pos1.Y(),0)) {
 268        pos1 = IntWithEdge(fMipPos,pos1);                                                            // find the very first intersection...
 269      } else {
 270        if(!AliHMPIDParam::IsInDead(pos1.X(),pos1.Y())) nPoints++;                                   //photon is accepted if not in dead zone
 271      }
 272      first=kTRUE;
 273      continue;
 274    }
 275    TVector2 pos2=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                              //trace the next photon
 276    if(pos2.X()==-999) continue;                                                                     //no area: open ring
 277    if(!fParam->IsInside(pos2.X(),pos2.Y(),0)) {
 278      pos2 = IntWithEdge(fMipPos,pos2);
 279    } else {
 280      if(!AliHMPIDParam::IsInDead(pos2.X(),pos2.Y())) nPoints++;                                     //photon is accepted if not in dead zone
 281    }
 282    area+=TMath::Abs((pos1-fMipPos).X()*(pos2-fMipPos).Y()-(pos1-fMipPos).Y()*(pos2-fMipPos).X());   //add area of the triangle...
 283    pos1 = pos2;
 284   }
 285 //---  find area and length of the ring;
 286   fRingAcc = (Double_t)nPoints/(Double_t)kN;
 287   area*=0.5;
 288   fRingArea = area;
 289 }//FindRingGeom()
 290 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 291 TVector2 AliHMPIDRecon::IntWithEdge(TVector2 p1,TVector2 p2)const
 292 {
 293 // It finds the intersection of the line for 2 points traced as photons
 294 // and the edge of a given PC
 295 // Arguments: 2 points obtained tracing the photons
 296 //   Returns: intersection point with detector (PC) edges
 297
 298   Double_t xmin = (p1.X()<p2.X())? p1.X():p2.X();
 299   Double_t xmax = (p1.X()<p2.X())? p2.X():p1.X();
 300   Double_t ymin = (p1.Y()<p2.Y())? p1.Y():p2.Y();
 301   Double_t ymax = (p1.Y()<p2.Y())? p2.Y():p1.Y();
 302
 303   Double_t m = TMath::Tan((p2-p1).Phi());
 304   TVector2 pint;
 305   //intersection with low  X
 306   pint.Set((Double_t)(p1.X() + (0-p1.Y())/m),0.);
 307   if(pint.X()>=0 && pint.X()<=fParam->SizeAllX() &&
 308      pint.X()>=xmin && pint.X()<=xmax            &&
 309      pint.Y()>=ymin && pint.Y()<=ymax) return pint;
 310   //intersection with high X
 311   pint.Set((Double_t)(p1.X() + (fParam->SizeAllY()-p1.Y())/m),(Double_t)(fParam->SizeAllY()));
 312   if(pint.X()>=0 && pint.X()<=fParam->SizeAllX() &&
 313      pint.X()>=xmin && pint.X()<=xmax            &&
 314      pint.Y()>=ymin && pint.Y()<=ymax) return pint;
 315   //intersection with left Y
 316   pint.Set(0.,(Double_t)(p1.Y() + m*(0-p1.X())));
 317   if(pint.Y()>=0 && pint.Y()<=fParam->SizeAllY() &&
 318      pint.Y()>=ymin && pint.Y()<=ymax            &&
 319      pint.X()>=xmin && pint.X()<=xmax) return pint;
 320   //intersection with righ Y
 321   pint.Set((Double_t)(fParam->SizeAllX()),(Double_t)(p1.Y() + m*(fParam->SizeAllX()-p1.X())));
 322   if(pint.Y()>=0 && pint.Y()<=fParam->SizeAllY() &&
 323      pint.Y()>=ymin && pint.Y()<=ymax            &&
 324      pint.X()>=xmin && pint.X()<=xmax) return pint;
 325   return p1;
 326 }//IntWithEdge()
 327 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 328 Double_t AliHMPIDRecon::FindRingCkov(Int_t)
 329 {
 330 // Loops on all Ckov candidates and estimates the best Theta Ckov for a ring formed by those candidates. Also estimates an error for that Theat Ckov
 331 // collecting errors for all single Ckov candidates thetas. (Assuming they are independent)
 332 // Arguments: iNclus- total number of clusters in chamber for background estimation
 333 //    Return: best estimation of track Theta ckov
 334
 335   Double_t wei = 0.;
 336   Double_t weightThetaCerenkov = 0.;
 337
 338   Double_t ckovMin=9999.,ckovMax=0.;
 339   Double_t sigma2 = 0;   //to collect error squared for this ring
 340
 341   for(Int_t i=0;i<fPhotCnt;i++){//candidates loop
 342     if(fPhotFlag[i] == 2){
 343       if(fPhotCkov[i]<ckovMin) ckovMin=fPhotCkov[i];                         //find max and min Theta ckov from all candidates within probable window
 344       if(fPhotCkov[i]>ckovMax) ckovMax=fPhotCkov[i];
 345       weightThetaCerenkov += fPhotCkov[i]*fPhotWei[i];
 346       wei += fPhotWei[i];                                                    //collect weight as sum of all candidate weghts
 347
 348       sigma2 += 1./fParam->Sigma2(fTrkDir.Theta(),fTrkDir.Phi(),fPhotCkov[i],fPhotPhi[i]);
 349     }
 350   }//candidates loop
 351
 352   if(sigma2>0) fCkovSigma2=1./sigma2;
 353   else         fCkovSigma2=1e10;
 354
 355   if(wei != 0.) weightThetaCerenkov /= wei; else weightThetaCerenkov = 0.;
 356   return weightThetaCerenkov;
 357 }//FindCkovRing()
 358 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 359 Int_t AliHMPIDRecon::FlagPhot(Double_t ckov)
 360 {
 361 // Flag photon candidates if their individual ckov angle is inside the window around ckov angle returned by  HoughResponse()
 362 // Arguments: ckov- value of most probable ckov angle for track as returned by HoughResponse()
 363 //   Returns: number of photon candidates happened to be inside the window
 364
 365 // Photon Flag:  Flag = 0 initial set;
 366 //               Flag = 1 good candidate (charge compatible with photon);
 367 //               Flag = 2 photon used for the ring;
 368
 369   Int_t steps = (Int_t)((ckov )/ fDTheta); //how many times we need to have fDTheta to fill the distance between 0  and thetaCkovHough
 370
 371   Double_t tmin = (Double_t)(steps - 1)*fDTheta;
 372   Double_t tmax = (Double_t)(steps)*fDTheta;
 373   Double_t tavg = 0.5*(tmin+tmax);
 374
 375   tmin = tavg - 0.5*fWindowWidth;  tmax = tavg + 0.5*fWindowWidth;
 376
 377   Int_t iInsideCnt = 0; //count photons which Theta ckov inside the window
 378   for(Int_t i=0;i<fPhotCnt;i++){//photon candidates loop
 379     fPhotFlag[i] = 0;
 380     if(fPhotCkov[i] >= tmin && fPhotCkov[i] <= tmax)    {
 381       fPhotFlag[i]=2;
 382       iInsideCnt++;
 383     }
 384   }
 385   return iInsideCnt;
 386 }//FlagPhot()
 387 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 388 TVector2 AliHMPIDRecon::TracePhot(Double_t ckovThe,Double_t ckovPhi)const
 389 {
 390 // Trace a single Ckov photon from emission point somewhere in radiator up to photocathode taking into account ref indexes of materials it travereses
 391 // Arguments: ckovThe,ckovPhi- photon ckov angles in TRS, [rad]
 392 //   Returns: distance between photon point on PC and track projection
 393
 394   Double_t theta,phi;
 395   TVector3  dirTRS,dirLORS;
 396   dirTRS.SetMagThetaPhi(1,ckovThe,ckovPhi);                     //photon in TRS
 397   Trs2Lors(dirTRS,theta,phi);
 398   dirLORS.SetMagThetaPhi(1,theta,phi);                          //photon in LORS
 399   return TraceForward(dirLORS);                                 //now foward tracing
 400 }//TracePhot()
 401 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 402 void AliHMPIDRecon::Propagate(const TVector3 dir,TVector3 &pos,Double_t z)const
 403 {
 404 // Finds an intersection point between a line and XY plane shifted along Z.
 405 // Arguments:  dir,pos   - vector along the line and any point of the line
 406 //             z         - z coordinate of plain
 407 //   Returns:  none
 408 //   On exit:  pos is the position if this intesection if any
 409   static TVector3 nrm(0,0,1);
 410          TVector3 pnt(0,0,z);
 411
 412   TVector3 diff=pnt-pos;
 413   Double_t sint=(nrm*diff)/(nrm*dir);
 414   pos+=sint*dir;
 415 }//Propagate()
 416 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 417 void AliHMPIDRecon::Refract(TVector3 &dir,Double_t n1,Double_t n2)const
 418 {
 419 // Refract direction vector according to Snell law
 420 // Arguments:
 421 //            n1 - ref idx of first substance
 422 //            n2 - ref idx of second substance
 423 //   Returns: none
 424 //   On exit: dir is new direction
 425   Double_t sinref=(n1/n2)*TMath::Sin(dir.Theta());
 426   if(TMath::Abs(sinref)>1.) dir.SetXYZ(-999,-999,-999);
 427   else             dir.SetTheta(TMath::ASin(sinref));
 428 }//Refract()
 429 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 430 Double_t AliHMPIDRecon::HoughResponse()
 431 {
 432 //
 433 //    fIdxMip = mipId;
 434
 435 //
 436   Double_t kThetaMax=0.75;
 437   Int_t nChannels = (Int_t)(kThetaMax/fDTheta+0.5);
 438   TH1D *phots   = new TH1D("Rphot"  ,"phots"         ,nChannels,0,kThetaMax);
 439   TH1D *photsw  = new TH1D("RphotWeighted" ,"photsw" ,nChannels,0,kThetaMax);
 440   TH1D *resultw = new TH1D("resultw","resultw"       ,nChannels,0,kThetaMax);
 441   Int_t nBin = (Int_t)(kThetaMax/fDTheta);
 442   Int_t nCorrBand = (Int_t)(fWindowWidth/(2*fDTheta));
 443
 444   for (Int_t i=0; i< fPhotCnt; i++){//photon cadidates loop
 445     Double_t angle = fPhotCkov[i];  if(angle<0||angle>kThetaMax) continue;
 446     phots->Fill(angle);
 447     Int_t bin = (Int_t)(0.5+angle/(fDTheta));
 448     Double_t weight=1.;
 449     if(fIsWEIGHT){
 450       Double_t lowerlimit = ((Double_t)bin)*fDTheta - 0.5*fDTheta;  Double_t upperlimit = ((Double_t)bin)*fDTheta + 0.5*fDTheta;
 451       FindRingGeom(lowerlimit);
 452       Double_t areaLow  = GetRingArea();
 453       FindRingGeom(upperlimit);
 454       Double_t areaHigh = GetRingArea();
 455       Double_t diffArea = areaHigh - areaLow;
 456       if(diffArea>0) weight = 1./diffArea;
 457     }
 458     photsw->Fill(angle,weight);
 459     fPhotWei[i]=weight;
 460   }//photon candidates loop
 461
 462   for (Int_t i=1; i<=nBin;i++){
 463     Int_t bin1= i-nCorrBand;
 464     Int_t bin2= i+nCorrBand;
 465     if(bin1<1) bin1=1;
 466     if(bin2>nBin)bin2=nBin;
 467     Double_t sumPhots=phots->Integral(bin1,bin2);
 468     if(sumPhots<3) continue;                            // if less then 3 photons don't trust to this ring
 469     Double_t sumPhotsw=photsw->Integral(bin1,bin2);
 470     resultw->Fill((Double_t)((i+0.5)*fDTheta),sumPhotsw);
 471   }
 472 // evaluate the "BEST" theta ckov as the maximum value of histogramm
 473   Double_t *pVec = resultw->GetArray();
 474   Int_t locMax = TMath::LocMax(nBin,pVec);
 475   delete phots;delete photsw;delete resultw; // Reset and delete objects
 476
 477   return (Double_t)(locMax*fDTheta+0.5*fDTheta); //final most probable track theta ckov
 478 }//HoughResponse()
 479 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++