HMPID/AliHMPIDRecon.cxx

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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   Int_t     fPhotCnt;                           // counter of photons candidate
  32   Int_t    *fPhotFlag;                          // flags of photon candidates
  33   Double_t *fPhotCkov;                          // Ckov angles of photon candidates, [rad]
  34   Double_t *fPhotPhi;                           // phis of photons candidates, [rad]
  35   Double_t *fPhotWei;                           // weigths of photon candidates
  36   Double_t  fCkovSigma2;                        // sigma2 of the reconstructed ring
  37
  38   Bool_t    fIsWEIGHT;                          // flag to consider weight procedure
  39   Float_t   fDTheta;                            // Step for sliding window
  40   Float_t   fWindowWidth;                       // Hough width of sliding window
  41
  42   Double_t  fRingArea;                          // area of a given ring
  43   Double_t  fRingAcc;                           // fraction of the ring accepted by geometry
  44   TVector3  fTrkDir;                            // track direction in LORS at RAD
  45   TVector2  fTrkPos;                            // track positon in LORS at RAD
  46   TVector2  fMipPos;                            // mip positon for a given track
  47   TVector2  fPc;                                // track position at PC
  48
  49   AliHMPIDParam *fParam;                        // Pointer to AliHMPIDParam
  50
  51
  52 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  53 AliHMPIDRecon::AliHMPIDRecon():
  54   TTask("RichRec","RichPat"),
  55   fPhotCnt(-1),
  56   fPhotFlag(0x0),
  57   fPhotCkov(0x0),
  58   fPhotPhi(0x0),
  59   fPhotWei(0x0),
  60   fCkovSigma2(0),
  61   fIsWEIGHT(kFALSE),
  62   fDTheta(0.001),
  63   fWindowWidth(0.045),
  64   fRingArea(0),
  65   fRingAcc(0),
  66   fTrkDir(0,0,1),  // Just for test
  67   fTrkPos(30,40),  // Just for test
  68   fMipPos(0,0),
  69   fPc(0,0),
  70   fParam(AliHMPIDParam::Instance())
  71 {
  72 //..
  73 //init of data members
  74 //..
  75
  76   fParam->SetRefIdx(fParam->MeanIdxRad()); // initialization of ref index to a default one
  77 }
  78 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  79 void AliHMPIDRecon::InitVars(Int_t n)
  80 {
  81 //..
  82 //Init some variables
  83 //..
  84   if(n<0) return;
  85   fPhotFlag = new Int_t[n];
  86   fPhotCkov = new Double_t[n];
  87   fPhotPhi  = new Double_t[n];
  88   fPhotWei  = new Double_t[n];
  89 //
  90 }
  91 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  92 void AliHMPIDRecon::DeleteVars()const
  93 {
  94 //..
  95 //Delete variables
  96 //..
  97   delete fPhotFlag;
  98   delete fPhotCkov;
  99   delete fPhotPhi;
 100   delete fPhotWei;
 101 }
 102 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 103 void AliHMPIDRecon::CkovAngle(AliESDtrack *pTrk,TClonesArray *pCluLst,Double_t nmean,Double_t qthre)
 104 {
 105 // Pattern recognition method based on Hough transform
 106 // Arguments:   pTrk     - track for which Ckov angle is to be found
 107 //              pCluLst  - list of clusters for this chamber
 108 //   Returns:            - track ckov angle, [rad],
 109
 110   Int_t nClusTot = pCluLst->GetEntries();
 111   if(nClusTot>fParam->MultCut()) fIsWEIGHT = kTRUE; // offset to take into account bkg in reconstruction
 112   else                           fIsWEIGHT = kFALSE;
 113
 114   InitVars(nClusTot);
 115
 116   Float_t xRa,yRa,th,ph;
 117   pTrk->GetHMPIDtrk(xRa,yRa,th,ph);        //initialize this track: th and ph angles at middle of RAD
 118   SetTrack(xRa,yRa,th,ph);
 119
 120   fParam->SetRefIdx(nmean);
 121
 122   Float_t dMin=999,mipX=-1,mipY=-1;Int_t chId=-1,mipId=-1,mipQ=-1;
 123   fPhotCnt=0;
 124   for (Int_t iClu=0; iClu<pCluLst->GetEntriesFast();iClu++){//clusters loop
 125     AliHMPIDCluster *pClu=(AliHMPIDCluster*)pCluLst->UncheckedAt(iClu);                       //get pointer to current cluster
 126     chId=pClu->Ch();
 127     if(pClu->Q()>qthre){                                                                      //charge compartible with MIP clusters
 128       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
 129       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
 130     }else{                                                                                    //charge compatible with photon cluster
 131       Double_t thetaCer,phiCer;
 132       if(FindPhotCkov(pClu->X(),pClu->Y(),thetaCer,phiCer)){                                  //find ckov angle for this  photon candidate
 133         fPhotCkov[fPhotCnt]=thetaCer;                                                         //actual theta Cerenkov (in TRS)
 134         fPhotPhi [fPhotCnt]=phiCer;                                                           //actual phi   Cerenkov (in TRS): -pi to come back to "unusual" ref system (X,Y,-Z)
 135         //PH        Printf("photon n. %i reconstructed theta = %f",fPhotCnt,fPhotCkov[fPhotCnt]);
 136         fPhotCnt++;                                                                           //increment counter of photon candidates
 137       }
 138     }
 139   }//clusters loop
 140   fMipPos.Set(mipX,mipY);
 141   if(fPhotCnt<=3) pTrk->SetHMPIDsignal(kNoPhotAccept);                                        //no reconstruction with <=3 photon candidates
 142   Int_t iNrec=FlagPhot(HoughResponse());                                                      //flag photons according to individual theta ckov with respect to most probable
 143   pTrk->SetHMPIDmip(mipX,mipY,mipQ,iNrec);                                                    //store mip info
 144
 145   if(mipId==-1)              {pTrk->SetHMPIDsignal(kMipQdcCut);  return;}                     //no clusters with QDC more the threshold at all
 146   if(dMin>fParam->DistCut()) {pTrk->SetHMPIDsignal(kMipDistCut); return;}                     //closest cluster with enough charge is still too far from intersection
 147   pTrk->SetHMPIDcluIdx(chId,mipId);                                                           //set index of cluster
 148   if(iNrec<1){
 149     pTrk->SetHMPIDsignal(kNoPhotAccept);                                                      //no photon candidates are accepted
 150   }
 151   else {
 152     Double_t thetaC = FindRingCkov(pCluLst->GetEntries());                                    //find the best reconstructed theta Cherenkov
 153 //    FindRingGeom(thetaC,2);
 154     pTrk->SetHMPIDsignal(thetaC);                                                             //store theta Cherenkov
 155     pTrk->SetHMPIDchi2(fCkovSigma2);                                                          //store errors squared
 156   }
 157
 158   DeleteVars();
 159 }//CkovAngle()
 160 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 161 Bool_t AliHMPIDRecon::FindPhotCkov(Double_t cluX,Double_t cluY,Double_t &thetaCer,Double_t &phiCer)
 162 {
 163 // Finds Cerenkov angle  for this photon candidate
 164 // Arguments: cluX,cluY - position of cadidate's cluster
 165 // Returns: Cerenkov angle
 166
 167   TVector3 dirCkov;
 168
 169   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();     //z position of middle of RAD
 170   TVector3 rad(fTrkPos.X(),fTrkPos.Y(),zRad);                        //impact point at middle of RAD
 171   TVector3  pc(cluX,cluY,0.5*fParam->WinThick()+fParam->GapIdx());   //mip at PC
 172   Double_t cluR = TMath::Sqrt((cluX-fTrkPos.X())*(cluX-fTrkPos.X())+
 173                               (cluY-fTrkPos.Y())*(cluY-fTrkPos.Y()));//ref. distance impact RAD-CLUSTER
 174   Double_t phi=(pc-rad).Phi();                                       //phi of photon
 175
 176   Double_t ckov1=0;
 177   Double_t ckov2=0.75+fTrkDir.Theta();                        //start to find theta cerenkov in DRS
 178   const Double_t kTol=0.01;
 179   Int_t iIterCnt = 0;
 180   while(1){
 181     if(iIterCnt>=50) return kFALSE;
 182     Double_t ckov=0.5*(ckov1+ckov2);
 183     dirCkov.SetMagThetaPhi(1,ckov,phi);
 184     TVector2 posC=TraceForward(dirCkov);                      //trace photon with actual angles
 185     Double_t dist=cluR-(posC-fTrkPos).Mod();                  //get distance between trial point and cluster position
 186     if(posC.X()==-999) dist = - 999;                          //total reflection problem
 187     iIterCnt++;                                               //counter step
 188     if     (dist> kTol) ckov1=ckov;                           //cluster @ larger ckov
 189     else if(dist<-kTol) ckov2=ckov;                           //cluster @ smaller ckov
 190     else{                                                     //precision achived: ckov in DRS found
 191       dirCkov.SetMagThetaPhi(1,ckov,phi);                     //
 192       Lors2Trs(dirCkov,thetaCer,phiCer);                       //find ckov (in TRS:the effective Cherenkov angle!)
 193       return kTRUE;
 194     }
 195   }
 196 }//FindPhotTheta()
 197 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 198 TVector2 AliHMPIDRecon::TraceForward(TVector3 dirCkov)const
 199 {
 200   //Trace forward a photon from (x,y) up to PC
 201   // Arguments: dirCkov photon vector in LORS
 202   //   Returns: pos of traced photon at PC
 203
 204   TVector2 pos(-999,-999);
 205   Double_t thetaCer = dirCkov.Theta();
 206   if(thetaCer > TMath::ASin(1./fParam->GetRefIdx())) return pos;          //total refraction on WIN-GAP boundary
 207   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();          //z position of middle of RAD
 208   TVector3  posCkov(fTrkPos.X(),fTrkPos.Y(),zRad);                        //RAD: photon position is track position @ middle of RAD
 209   Propagate(dirCkov,posCkov,           -0.5*fParam->WinThick());          //go to RAD-WIN boundary
 210   Refract  (dirCkov,         fParam->GetRefIdx(),fParam->WinIdx());       //RAD-WIN refraction
 211   Propagate(dirCkov,posCkov,            0.5*fParam->WinThick());          //go to WIN-GAP boundary
 212   Refract  (dirCkov,         fParam->WinIdx(),fParam->GapIdx());          //WIN-GAP refraction
 213   Propagate(dirCkov,posCkov,0.5*fParam->WinThick()+fParam->GapThick());   //go to PC
 214   pos.Set(posCkov.X(),posCkov.Y());
 215   return pos;
 216 }//TraceForward()
 217 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 218 void AliHMPIDRecon::Lors2Trs(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
 219 {
 220   //Theta Cerenkov reconstruction
 221   // Arguments: dirCkov photon vector in LORS
 222   //   Returns: thetaCer of photon in TRS
 223   //              phiCer of photon in TRS
 224 //  TVector3 dirTrk;
 225 //  dirTrk.SetMagThetaPhi(1,fTrkDir.Theta(),fTrkDir.Phi());
 226 //  Double_t thetaCer = TMath::ACos(dirCkov*dirTrk);
 227   TRotation mtheta;   mtheta.RotateY(-fTrkDir.Theta());
 228   TRotation mphi;       mphi.RotateZ(-fTrkDir.Phi());
 229   TRotation mrot=mtheta*mphi;
 230   TVector3 dirCkovTRS;
 231   dirCkovTRS=mrot*dirCkov;
 232   phiCer  = dirCkovTRS.Phi();                                          //actual value of the phi of the photon
 233   thetaCer= dirCkovTRS.Theta();                                        //actual value of thetaCerenkov of the photon
 234 }
 235 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 236 void AliHMPIDRecon::Trs2Lors(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
 237 {
 238   //Theta Cerenkov reconstruction
 239   // Arguments: dirCkov photon vector in TRS
 240   //   Returns: thetaCer of photon in LORS
 241   //              phiCer of photon in LORS
 242   TRotation mtheta;   mtheta.RotateY(fTrkDir.Theta());
 243   TRotation mphi;       mphi.RotateZ(fTrkDir.Phi());
 244   TRotation mrot=mphi*mtheta;
 245   TVector3 dirCkovLORS;
 246   dirCkovLORS=mrot*dirCkov;
 247   phiCer  = dirCkovLORS.Phi();                                          //actual value of the phi of the photon
 248   thetaCer= dirCkovLORS.Theta();                                        //actual value of thetaCerenkov of the photon
 249 }
 250 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 251 void AliHMPIDRecon::FindRingGeom(Double_t ckovAng,Int_t level)
 252 {
 253 // Find area covered in the PC acceptance
 254 // Arguments: ckovAng - cerenkov angle
 255 //            level   - precision in finding area and portion of ring accepted (multiple of 50)
 256 //   Returns: area of the ring in cm^2 for given theta ckov
 257
 258   Int_t kN=50*level;
 259   Int_t nPoints = 0;
 260   Double_t area=0;
 261
 262   Bool_t first=kFALSE;
 263   TVector2 pos1;
 264
 265   for(Int_t i=0;i<kN;i++){
 266    if(!first) {
 267       pos1=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                                    //find a good trace for the first photon
 268      if(pos1.X()==-999) continue;                                                                   //no area: open ring
 269      if(!fParam->IsInside(pos1.X(),pos1.Y(),0)) {
 270        pos1 = IntWithEdge(fMipPos,pos1);                                                            // find the very first intersection...
 271      } else {
 272        if(!AliHMPIDParam::IsInDead(pos1.X(),pos1.Y())) nPoints++;                                   //photon is accepted if not in dead zone
 273      }
 274      first=kTRUE;
 275      continue;
 276    }
 277    TVector2 pos2=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                              //trace the next photon
 278    if(pos2.X()==-999) continue;                                                                     //no area: open ring
 279    if(!fParam->IsInside(pos2.X(),pos2.Y(),0)) {
 280      pos2 = IntWithEdge(fMipPos,pos2);
 281    } else {
 282      if(!AliHMPIDParam::IsInDead(pos2.X(),pos2.Y())) nPoints++;                                     //photon is accepted if not in dead zone
 283    }
 284    area+=TMath::Abs((pos1-fMipPos).X()*(pos2-fMipPos).Y()-(pos1-fMipPos).Y()*(pos2-fMipPos).X());   //add area of the triangle...
 285    pos1 = pos2;
 286   }
 287 //---  find area and length of the ring;
 288   fRingAcc = (Double_t)nPoints/(Double_t)kN;
 289   area*=0.5;
 290   fRingArea = area;
 291 }//FindRingGeom()
 292 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 293 TVector2 AliHMPIDRecon::IntWithEdge(TVector2 p1,TVector2 p2)const
 294 {
 295 // It finds the intersection of the line for 2 points traced as photons
 296 // and the edge of a given PC
 297 // Arguments: 2 points obtained tracing the photons
 298 //   Returns: intersection point with detector (PC) edges
 299
 300   Double_t xmin = (p1.X()<p2.X())? p1.X():p2.X();
 301   Double_t xmax = (p1.X()<p2.X())? p2.X():p1.X();
 302   Double_t ymin = (p1.Y()<p2.Y())? p1.Y():p2.Y();
 303   Double_t ymax = (p1.Y()<p2.Y())? p2.Y():p1.Y();
 304
 305   Double_t m = TMath::Tan((p2-p1).Phi());
 306   TVector2 pint;
 307   //intersection with low  X
 308   pint.Set((Double_t)(p1.X() + (0-p1.Y())/m),0.);
 309   if(pint.X()>=0 && pint.X()<=fParam->SizeAllX() &&
 310      pint.X()>=xmin && pint.X()<=xmax            &&
 311      pint.Y()>=ymin && pint.Y()<=ymax) return pint;
 312   //intersection with high X
 313   pint.Set((Double_t)(p1.X() + (fParam->SizeAllY()-p1.Y())/m),(Double_t)(fParam->SizeAllY()));
 314   if(pint.X()>=0 && pint.X()<=fParam->SizeAllX() &&
 315      pint.X()>=xmin && pint.X()<=xmax            &&
 316      pint.Y()>=ymin && pint.Y()<=ymax) return pint;
 317   //intersection with left Y
 318   pint.Set(0.,(Double_t)(p1.Y() + m*(0-p1.X())));
 319   if(pint.Y()>=0 && pint.Y()<=fParam->SizeAllY() &&
 320      pint.Y()>=ymin && pint.Y()<=ymax            &&
 321      pint.X()>=xmin && pint.X()<=xmax) return pint;
 322   //intersection with righ Y
 323   pint.Set((Double_t)(fParam->SizeAllX()),(Double_t)(p1.Y() + m*(fParam->SizeAllX()-p1.X())));
 324   if(pint.Y()>=0 && pint.Y()<=fParam->SizeAllY() &&
 325      pint.Y()>=ymin && pint.Y()<=ymax            &&
 326      pint.X()>=xmin && pint.X()<=xmax) return pint;
 327   return p1;
 328 }//IntWithEdge()
 329 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 330 Double_t AliHMPIDRecon::FindRingCkov(Int_t)
 331 {
 332 // 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
 333 // collecting errors for all single Ckov candidates thetas. (Assuming they are independent)
 334 // Arguments: iNclus- total number of clusters in chamber for background estimation
 335 //    Return: best estimation of track Theta ckov
 336
 337   Double_t wei = 0.;
 338   Double_t weightThetaCerenkov = 0.;
 339
 340   Double_t ckovMin=9999.,ckovMax=0.;
 341   Double_t sigma2 = 0;   //to collect error squared for this ring
 342
 343   for(Int_t i=0;i<fPhotCnt;i++){//candidates loop
 344     if(fPhotFlag[i] == 2){
 345       if(fPhotCkov[i]<ckovMin) ckovMin=fPhotCkov[i];                         //find max and min Theta ckov from all candidates within probable window
 346       if(fPhotCkov[i]>ckovMax) ckovMax=fPhotCkov[i];
 347       weightThetaCerenkov += fPhotCkov[i]*fPhotWei[i];
 348       wei += fPhotWei[i];                                                    //collect weight as sum of all candidate weghts
 349
 350       sigma2 += 1./fParam->Sigma2(fTrkDir.Theta(),fTrkDir.Phi(),fPhotCkov[i],fPhotPhi[i]);
 351     }
 352   }//candidates loop
 353
 354   if(sigma2>0) fCkovSigma2=1./sigma2;
 355   else         fCkovSigma2=1e10;
 356
 357   if(wei != 0.) weightThetaCerenkov /= wei; else weightThetaCerenkov = 0.;
 358   return weightThetaCerenkov;
 359 }//FindCkovRing()
 360 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 361 Int_t AliHMPIDRecon::FlagPhot(Double_t ckov)
 362 {
 363 // Flag photon candidates if their individual ckov angle is inside the window around ckov angle returned by  HoughResponse()
 364 // Arguments: ckov- value of most probable ckov angle for track as returned by HoughResponse()
 365 //   Returns: number of photon candidates happened to be inside the window
 366
 367 // Photon Flag:  Flag = 0 initial set;
 368 //               Flag = 1 good candidate (charge compatible with photon);
 369 //               Flag = 2 photon used for the ring;
 370
 371   Int_t steps = (Int_t)((ckov )/ fDTheta); //how many times we need to have fDTheta to fill the distance between 0  and thetaCkovHough
 372
 373   Double_t tmin = (Double_t)(steps - 1)*fDTheta;
 374   Double_t tmax = (Double_t)(steps)*fDTheta;
 375   Double_t tavg = 0.5*(tmin+tmax);
 376
 377   tmin = tavg - 0.5*fWindowWidth;  tmax = tavg + 0.5*fWindowWidth;
 378
 379   Int_t iInsideCnt = 0; //count photons which Theta ckov inside the window
 380   for(Int_t i=0;i<fPhotCnt;i++){//photon candidates loop
 381     fPhotFlag[i] = 0;
 382     if(fPhotCkov[i] >= tmin && fPhotCkov[i] <= tmax)    {
 383       fPhotFlag[i]=2;
 384       iInsideCnt++;
 385     }
 386   }
 387   return iInsideCnt;
 388 }//FlagPhot()
 389 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 390 TVector2 AliHMPIDRecon::TracePhot(Double_t ckovThe,Double_t ckovPhi)const
 391 {
 392 // Trace a single Ckov photon from emission point somewhere in radiator up to photocathode taking into account ref indexes of materials it travereses
 393 // Arguments: ckovThe,ckovPhi- photon ckov angles in TRS, [rad]
 394 //   Returns: distance between photon point on PC and track projection
 395
 396   Double_t theta,phi;
 397   TVector3  dirTRS,dirLORS;
 398   dirTRS.SetMagThetaPhi(1,ckovThe,ckovPhi);                     //photon in TRS
 399   Trs2Lors(dirTRS,theta,phi);
 400   dirLORS.SetMagThetaPhi(1,theta,phi);                          //photon in LORS
 401   return TraceForward(dirLORS);                                 //now foward tracing
 402 }//TracePhot()
 403 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 404 void AliHMPIDRecon::Propagate(const TVector3 dir,TVector3 &pos,Double_t z)const
 405 {
 406 // Finds an intersection point between a line and XY plane shifted along Z.
 407 // Arguments:  dir,pos   - vector along the line and any point of the line
 408 //             z         - z coordinate of plain
 409 //   Returns:  none
 410 //   On exit:  pos is the position if this intesection if any
 411   static TVector3 nrm(0,0,1);
 412          TVector3 pnt(0,0,z);
 413
 414   TVector3 diff=pnt-pos;
 415   Double_t sint=(nrm*diff)/(nrm*dir);
 416   pos+=sint*dir;
 417 }//Propagate()
 418 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 419 void AliHMPIDRecon::Refract(TVector3 &dir,Double_t n1,Double_t n2)const
 420 {
 421 // Refract direction vector according to Snell law
 422 // Arguments:
 423 //            n1 - ref idx of first substance
 424 //            n2 - ref idx of second substance
 425 //   Returns: none
 426 //   On exit: dir is new direction
 427   Double_t sinref=(n1/n2)*TMath::Sin(dir.Theta());
 428   if(TMath::Abs(sinref)>1.) dir.SetXYZ(-999,-999,-999);
 429   else             dir.SetTheta(TMath::ASin(sinref));
 430 }//Refract()
 431 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 432 Double_t AliHMPIDRecon::HoughResponse()
 433 {
 434 //
 435 //    fIdxMip = mipId;
 436
 437 //
 438   Double_t kThetaMax=0.75;
 439   Int_t nChannels = (Int_t)(kThetaMax/fDTheta+0.5);
 440   TH1D *phots   = new TH1D("Rphot"  ,"phots"         ,nChannels,0,kThetaMax);
 441   TH1D *photsw  = new TH1D("RphotWeighted" ,"photsw" ,nChannels,0,kThetaMax);
 442   TH1D *resultw = new TH1D("resultw","resultw"       ,nChannels,0,kThetaMax);
 443   Int_t nBin = (Int_t)(kThetaMax/fDTheta);
 444   Int_t nCorrBand = (Int_t)(fWindowWidth/(2*fDTheta));
 445
 446   for (Int_t i=0; i< fPhotCnt; i++){//photon cadidates loop
 447     Double_t angle = fPhotCkov[i];  if(angle<0||angle>kThetaMax) continue;
 448     phots->Fill(angle);
 449     Int_t bin = (Int_t)(0.5+angle/(fDTheta));
 450     Double_t weight=1.;
 451     if(fIsWEIGHT){
 452       Double_t lowerlimit = ((Double_t)bin)*fDTheta - 0.5*fDTheta;  Double_t upperlimit = ((Double_t)bin)*fDTheta + 0.5*fDTheta;
 453       FindRingGeom(lowerlimit);
 454       Double_t areaLow  = GetRingArea();
 455       FindRingGeom(upperlimit);
 456       Double_t areaHigh = GetRingArea();
 457       Double_t diffArea = areaHigh - areaLow;
 458       if(diffArea>0) weight = 1./diffArea;
 459     }
 460     photsw->Fill(angle,weight);
 461     fPhotWei[i]=weight;
 462   }//photon candidates loop
 463
 464   for (Int_t i=1; i<=nBin;i++){
 465     Int_t bin1= i-nCorrBand;
 466     Int_t bin2= i+nCorrBand;
 467     if(bin1<1) bin1=1;
 468     if(bin2>nBin)bin2=nBin;
 469     Double_t sumPhots=phots->Integral(bin1,bin2);
 470     if(sumPhots<3) continue;                            // if less then 3 photons don't trust to this ring
 471     Double_t sumPhotsw=photsw->Integral(bin1,bin2);
 472     resultw->Fill((Double_t)((i+0.5)*fDTheta),sumPhotsw);
 473   }
 474 // evaluate the "BEST" theta ckov as the maximum value of histogramm
 475   Double_t *pVec = resultw->GetArray();
 476   Int_t locMax = TMath::LocMax(nBin,pVec);
 477   delete phots;delete photsw;delete resultw; // Reset and delete objects
 478
 479   return (Double_t)(locMax*fDTheta+0.5*fDTheta); //final most probable track theta ckov
 480 }//HoughResponse()
 481 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++