HMPID/AliHMPIDRecon.cxx

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   3  *                                                                        *
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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
 111   const Int_t nMinPhotAcc = 3;                      // Minimum number of photons required to perform the pattern recognition
 112
 113
 114   Int_t nClusTot = pCluLst->GetEntries();
 115   if(nClusTot>fParam->MultCut()) fIsWEIGHT = kTRUE; // offset to take into account bkg in reconstruction
 116   else                           fIsWEIGHT = kFALSE;
 117
 118   InitVars(nClusTot);
 119
 120   Float_t xRa,yRa,th,ph;
 121   pTrk->GetHMPIDtrk(xRa,yRa,th,ph);        //initialize this track: th and ph angles at middle of RAD
 122   SetTrack(xRa,yRa,th,ph);
 123
 124   fParam->SetRefIdx(nmean);
 125
 126   Float_t dMin=999,mipX=-1,mipY=-1;Int_t chId=-1,mipId=-1,mipQ=-1;
 127   fPhotCnt=0;
 128   for (Int_t iClu=0; iClu<pCluLst->GetEntriesFast();iClu++){//clusters loop
 129     AliHMPIDCluster *pClu=(AliHMPIDCluster*)pCluLst->UncheckedAt(iClu);                       //get pointer to current cluster
 130     chId=pClu->Ch();
 131     if(pClu->Q()>qthre){                                                                      //charge compartible with MIP clusters
 132       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
 133       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
 134     }else{                                                                                    //charge compatible with photon cluster
 135       Double_t thetaCer,phiCer;
 136       if(FindPhotCkov(pClu->X(),pClu->Y(),thetaCer,phiCer)){                                  //find ckov angle for this  photon candidate
 137         fPhotCkov[fPhotCnt]=thetaCer;                                                         //actual theta Cerenkov (in TRS)
 138         fPhotPhi [fPhotCnt]=phiCer;                                                           //actual phi   Cerenkov (in TRS): -pi to come back to "unusual" ref system (X,Y,-Z)
 139         //PH        Printf("photon n. %i reconstructed theta = %f",fPhotCnt,fPhotCkov[fPhotCnt]);
 140         fPhotCnt++;                                                                           //increment counter of photon candidates
 141       }
 142     }
 143   }//clusters loop
 144
 145   if(fPhotCnt<=nMinPhotAcc) {                                                                 //no reconstruction with <=3 photon candidates
 146     pTrk->SetHMPIDsignal(kNoPhotAccept);                                                      //set the appropriate flag
 147     pTrk->SetHMPIDmip(mipX,mipY,mipQ,fPhotCnt);                                               //store mip info
 148     pTrk->SetHMPIDcluIdx(-1,-1);                                                              //set index of cluster
 149     return;
 150   }
 151
 152   if(mipId==-1) {
 153     pTrk->SetHMPIDcluIdx(chId,9999);                                                          //set index of cluster
 154     pTrk->SetHMPIDsignal(kMipQdcCut);
 155     return;
 156   }                                                                                           //no clusters with QDC more the threshold at all
 157     pTrk->SetHMPIDcluIdx(chId,mipId);                                                         //set index of cluster
 158     if(dMin>fParam->DistCut()) {pTrk->SetHMPIDsignal(kMipDistCut); return;}                   //closest cluster with enough charge is still too far from intersection
 159
 160   fMipPos.Set(mipX,mipY);
 161
 162
 163 //PATTERN RECOGNITION STARTED:
 164
 165   Int_t iNrec=FlagPhot(HoughResponse());                                                      //flag photons according to individual theta ckov with respect to most probable
 166   pTrk->SetHMPIDmip(mipX,mipY,mipQ,iNrec);                                                    //store mip info
 167
 168   if(iNrec<1){
 169     pTrk->SetHMPIDsignal(kNoPhotAccept);                                                      //no photon candidates are accepted
 170     return;
 171   }
 172   Double_t thetaC = FindRingCkov(pCluLst->GetEntries());                                    //find the best reconstructed theta Cherenkov
 173 //    FindRingGeom(thetaC,2);
 174   pTrk->SetHMPIDsignal(thetaC);                                                             //store theta Cherenkov
 175   pTrk->SetHMPIDchi2(fCkovSigma2);                                                          //store errors squared
 176
 177   DeleteVars();
 178 }//CkovAngle()
 179 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 180 Bool_t AliHMPIDRecon::FindPhotCkov(Double_t cluX,Double_t cluY,Double_t &thetaCer,Double_t &phiCer)
 181 {
 182 // Finds Cerenkov angle  for this photon candidate
 183 // Arguments: cluX,cluY - position of cadidate's cluster
 184 // Returns: Cerenkov angle
 185
 186   TVector3 dirCkov;
 187
 188   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();     //z position of middle of RAD
 189   TVector3 rad(fTrkPos.X(),fTrkPos.Y(),zRad);                        //impact point at middle of RAD
 190   TVector3  pc(cluX,cluY,0.5*fParam->WinThick()+fParam->GapIdx());   //mip at PC
 191   Double_t cluR = TMath::Sqrt((cluX-fTrkPos.X())*(cluX-fTrkPos.X())+
 192                               (cluY-fTrkPos.Y())*(cluY-fTrkPos.Y()));//ref. distance impact RAD-CLUSTER
 193   Double_t phi=(pc-rad).Phi();                                       //phi of photon
 194
 195   Double_t ckov1=0;
 196   Double_t ckov2=0.75+fTrkDir.Theta();                        //start to find theta cerenkov in DRS
 197   const Double_t kTol=0.01;
 198   Int_t iIterCnt = 0;
 199   while(1){
 200     if(iIterCnt>=50) return kFALSE;
 201     Double_t ckov=0.5*(ckov1+ckov2);
 202     dirCkov.SetMagThetaPhi(1,ckov,phi);
 203     TVector2 posC=TraceForward(dirCkov);                      //trace photon with actual angles
 204     Double_t dist=cluR-(posC-fTrkPos).Mod();                  //get distance between trial point and cluster position
 205     if(posC.X()==-999) dist = - 999;                          //total reflection problem
 206     iIterCnt++;                                               //counter step
 207     if     (dist> kTol) ckov1=ckov;                           //cluster @ larger ckov
 208     else if(dist<-kTol) ckov2=ckov;                           //cluster @ smaller ckov
 209     else{                                                     //precision achived: ckov in DRS found
 210       dirCkov.SetMagThetaPhi(1,ckov,phi);                     //
 211       Lors2Trs(dirCkov,thetaCer,phiCer);                       //find ckov (in TRS:the effective Cherenkov angle!)
 212       return kTRUE;
 213     }
 214   }
 215 }//FindPhotTheta()
 216 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 217 TVector2 AliHMPIDRecon::TraceForward(TVector3 dirCkov)const
 218 {
 219   //Trace forward a photon from (x,y) up to PC
 220   // Arguments: dirCkov photon vector in LORS
 221   //   Returns: pos of traced photon at PC
 222
 223   TVector2 pos(-999,-999);
 224   Double_t thetaCer = dirCkov.Theta();
 225   if(thetaCer > TMath::ASin(1./fParam->GetRefIdx())) return pos;          //total refraction on WIN-GAP boundary
 226   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();          //z position of middle of RAD
 227   TVector3  posCkov(fTrkPos.X(),fTrkPos.Y(),zRad);                        //RAD: photon position is track position @ middle of RAD
 228   Propagate(dirCkov,posCkov,           -0.5*fParam->WinThick());          //go to RAD-WIN boundary
 229   Refract  (dirCkov,         fParam->GetRefIdx(),fParam->WinIdx());       //RAD-WIN refraction
 230   Propagate(dirCkov,posCkov,            0.5*fParam->WinThick());          //go to WIN-GAP boundary
 231   Refract  (dirCkov,         fParam->WinIdx(),fParam->GapIdx());          //WIN-GAP refraction
 232   Propagate(dirCkov,posCkov,0.5*fParam->WinThick()+fParam->GapThick());   //go to PC
 233   pos.Set(posCkov.X(),posCkov.Y());
 234   return pos;
 235 }//TraceForward()
 236 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 237 void AliHMPIDRecon::Lors2Trs(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
 238 {
 239   //Theta Cerenkov reconstruction
 240   // Arguments: dirCkov photon vector in LORS
 241   //   Returns: thetaCer of photon in TRS
 242   //              phiCer of photon in TRS
 243 //  TVector3 dirTrk;
 244 //  dirTrk.SetMagThetaPhi(1,fTrkDir.Theta(),fTrkDir.Phi());
 245 //  Double_t thetaCer = TMath::ACos(dirCkov*dirTrk);
 246   TRotation mtheta;   mtheta.RotateY(-fTrkDir.Theta());
 247   TRotation mphi;       mphi.RotateZ(-fTrkDir.Phi());
 248   TRotation mrot=mtheta*mphi;
 249   TVector3 dirCkovTRS;
 250   dirCkovTRS=mrot*dirCkov;
 251   phiCer  = dirCkovTRS.Phi();                                          //actual value of the phi of the photon
 252   thetaCer= dirCkovTRS.Theta();                                        //actual value of thetaCerenkov of the photon
 253 }
 254 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 255 void AliHMPIDRecon::Trs2Lors(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
 256 {
 257   //Theta Cerenkov reconstruction
 258   // Arguments: dirCkov photon vector in TRS
 259   //   Returns: thetaCer of photon in LORS
 260   //              phiCer of photon in LORS
 261   TRotation mtheta;   mtheta.RotateY(fTrkDir.Theta());
 262   TRotation mphi;       mphi.RotateZ(fTrkDir.Phi());
 263   TRotation mrot=mphi*mtheta;
 264   TVector3 dirCkovLORS;
 265   dirCkovLORS=mrot*dirCkov;
 266   phiCer  = dirCkovLORS.Phi();                                          //actual value of the phi of the photon
 267   thetaCer= dirCkovLORS.Theta();                                        //actual value of thetaCerenkov of the photon
 268 }
 269 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 270 void AliHMPIDRecon::FindRingGeom(Double_t ckovAng,Int_t level)
 271 {
 272 // Find area covered in the PC acceptance
 273 // Arguments: ckovAng - cerenkov angle
 274 //            level   - precision in finding area and portion of ring accepted (multiple of 50)
 275 //   Returns: area of the ring in cm^2 for given theta ckov
 276
 277   Int_t kN=50*level;
 278   Int_t nPoints = 0;
 279   Double_t area=0;
 280
 281   Bool_t first=kFALSE;
 282   TVector2 pos1;
 283
 284   for(Int_t i=0;i<kN;i++){
 285    if(!first) {
 286       pos1=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                                    //find a good trace for the first photon
 287      if(pos1.X()==-999) continue;                                                                   //no area: open ring
 288      if(!fParam->IsInside(pos1.X(),pos1.Y(),0)) {
 289        pos1 = IntWithEdge(fMipPos,pos1);                                                            // find the very first intersection...
 290      } else {
 291        if(!AliHMPIDParam::IsInDead(pos1.X(),pos1.Y())) nPoints++;                                   //photon is accepted if not in dead zone
 292      }
 293      first=kTRUE;
 294      continue;
 295    }
 296    TVector2 pos2=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                              //trace the next photon
 297    if(pos2.X()==-999) continue;                                                                     //no area: open ring
 298    if(!fParam->IsInside(pos2.X(),pos2.Y(),0)) {
 299      pos2 = IntWithEdge(fMipPos,pos2);
 300    } else {
 301      if(!AliHMPIDParam::IsInDead(pos2.X(),pos2.Y())) nPoints++;                                     //photon is accepted if not in dead zone
 302    }
 303    area+=TMath::Abs((pos1-fMipPos).X()*(pos2-fMipPos).Y()-(pos1-fMipPos).Y()*(pos2-fMipPos).X());   //add area of the triangle...
 304    pos1 = pos2;
 305   }
 306 //---  find area and length of the ring;
 307   fRingAcc = (Double_t)nPoints/(Double_t)kN;
 308   area*=0.5;
 309   fRingArea = area;
 310 }//FindRingGeom()
 311 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 312 TVector2 AliHMPIDRecon::IntWithEdge(TVector2 p1,TVector2 p2)const
 313 {
 314 // It finds the intersection of the line for 2 points traced as photons
 315 // and the edge of a given PC
 316 // Arguments: 2 points obtained tracing the photons
 317 //   Returns: intersection point with detector (PC) edges
 318
 319   Double_t xmin = (p1.X()<p2.X())? p1.X():p2.X();
 320   Double_t xmax = (p1.X()<p2.X())? p2.X():p1.X();
 321   Double_t ymin = (p1.Y()<p2.Y())? p1.Y():p2.Y();
 322   Double_t ymax = (p1.Y()<p2.Y())? p2.Y():p1.Y();
 323
 324   Double_t m = TMath::Tan((p2-p1).Phi());
 325   TVector2 pint;
 326   //intersection with low  X
 327   pint.Set((Double_t)(p1.X() + (0-p1.Y())/m),0.);
 328   if(pint.X()>=0 && pint.X()<=fParam->SizeAllX() &&
 329      pint.X()>=xmin && pint.X()<=xmax            &&
 330      pint.Y()>=ymin && pint.Y()<=ymax) return pint;
 331   //intersection with high X
 332   pint.Set((Double_t)(p1.X() + (fParam->SizeAllY()-p1.Y())/m),(Double_t)(fParam->SizeAllY()));
 333   if(pint.X()>=0 && pint.X()<=fParam->SizeAllX() &&
 334      pint.X()>=xmin && pint.X()<=xmax            &&
 335      pint.Y()>=ymin && pint.Y()<=ymax) return pint;
 336   //intersection with left Y
 337   pint.Set(0.,(Double_t)(p1.Y() + m*(0-p1.X())));
 338   if(pint.Y()>=0 && pint.Y()<=fParam->SizeAllY() &&
 339      pint.Y()>=ymin && pint.Y()<=ymax            &&
 340      pint.X()>=xmin && pint.X()<=xmax) return pint;
 341   //intersection with righ Y
 342   pint.Set((Double_t)(fParam->SizeAllX()),(Double_t)(p1.Y() + m*(fParam->SizeAllX()-p1.X())));
 343   if(pint.Y()>=0 && pint.Y()<=fParam->SizeAllY() &&
 344      pint.Y()>=ymin && pint.Y()<=ymax            &&
 345      pint.X()>=xmin && pint.X()<=xmax) return pint;
 346   return p1;
 347 }//IntWithEdge()
 348 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 349 Double_t AliHMPIDRecon::FindRingCkov(Int_t)
 350 {
 351 // 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
 352 // collecting errors for all single Ckov candidates thetas. (Assuming they are independent)
 353 // Arguments: iNclus- total number of clusters in chamber for background estimation
 354 //    Return: best estimation of track Theta ckov
 355
 356   Double_t wei = 0.;
 357   Double_t weightThetaCerenkov = 0.;
 358
 359   Double_t ckovMin=9999.,ckovMax=0.;
 360   Double_t sigma2 = 0;   //to collect error squared for this ring
 361
 362   for(Int_t i=0;i<fPhotCnt;i++){//candidates loop
 363     if(fPhotFlag[i] == 2){
 364       if(fPhotCkov[i]<ckovMin) ckovMin=fPhotCkov[i];                         //find max and min Theta ckov from all candidates within probable window
 365       if(fPhotCkov[i]>ckovMax) ckovMax=fPhotCkov[i];
 366       weightThetaCerenkov += fPhotCkov[i]*fPhotWei[i];
 367       wei += fPhotWei[i];                                                    //collect weight as sum of all candidate weghts
 368
 369       sigma2 += 1./fParam->Sigma2(fTrkDir.Theta(),fTrkDir.Phi(),fPhotCkov[i],fPhotPhi[i]);
 370     }
 371   }//candidates loop
 372
 373   if(sigma2>0) fCkovSigma2=1./sigma2;
 374   else         fCkovSigma2=1e10;
 375
 376   if(wei != 0.) weightThetaCerenkov /= wei; else weightThetaCerenkov = 0.;
 377   return weightThetaCerenkov;
 378 }//FindCkovRing()
 379 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 380 Int_t AliHMPIDRecon::FlagPhot(Double_t ckov)
 381 {
 382 // Flag photon candidates if their individual ckov angle is inside the window around ckov angle returned by  HoughResponse()
 383 // Arguments: ckov- value of most probable ckov angle for track as returned by HoughResponse()
 384 //   Returns: number of photon candidates happened to be inside the window
 385
 386 // Photon Flag:  Flag = 0 initial set;
 387 //               Flag = 1 good candidate (charge compatible with photon);
 388 //               Flag = 2 photon used for the ring;
 389
 390   Int_t steps = (Int_t)((ckov )/ fDTheta); //how many times we need to have fDTheta to fill the distance between 0  and thetaCkovHough
 391
 392   Double_t tmin = (Double_t)(steps - 1)*fDTheta;
 393   Double_t tmax = (Double_t)(steps)*fDTheta;
 394   Double_t tavg = 0.5*(tmin+tmax);
 395
 396   tmin = tavg - 0.5*fWindowWidth;  tmax = tavg + 0.5*fWindowWidth;
 397
 398   Int_t iInsideCnt = 0; //count photons which Theta ckov inside the window
 399   for(Int_t i=0;i<fPhotCnt;i++){//photon candidates loop
 400     fPhotFlag[i] = 0;
 401     if(fPhotCkov[i] >= tmin && fPhotCkov[i] <= tmax)    {
 402       fPhotFlag[i]=2;
 403       iInsideCnt++;
 404     }
 405   }
 406   return iInsideCnt;
 407 }//FlagPhot()
 408 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 409 TVector2 AliHMPIDRecon::TracePhot(Double_t ckovThe,Double_t ckovPhi)const
 410 {
 411 // Trace a single Ckov photon from emission point somewhere in radiator up to photocathode taking into account ref indexes of materials it travereses
 412 // Arguments: ckovThe,ckovPhi- photon ckov angles in TRS, [rad]
 413 //   Returns: distance between photon point on PC and track projection
 414
 415   Double_t theta,phi;
 416   TVector3  dirTRS,dirLORS;
 417   dirTRS.SetMagThetaPhi(1,ckovThe,ckovPhi);                     //photon in TRS
 418   Trs2Lors(dirTRS,theta,phi);
 419   dirLORS.SetMagThetaPhi(1,theta,phi);                          //photon in LORS
 420   return TraceForward(dirLORS);                                 //now foward tracing
 421 }//TracePhot()
 422 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 423 void AliHMPIDRecon::Propagate(const TVector3 dir,TVector3 &pos,Double_t z)const
 424 {
 425 // Finds an intersection point between a line and XY plane shifted along Z.
 426 // Arguments:  dir,pos   - vector along the line and any point of the line
 427 //             z         - z coordinate of plain
 428 //   Returns:  none
 429 //   On exit:  pos is the position if this intesection if any
 430   static TVector3 nrm(0,0,1);
 431          TVector3 pnt(0,0,z);
 432
 433   TVector3 diff=pnt-pos;
 434   Double_t sint=(nrm*diff)/(nrm*dir);
 435   pos+=sint*dir;
 436 }//Propagate()
 437 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 438 void AliHMPIDRecon::Refract(TVector3 &dir,Double_t n1,Double_t n2)const
 439 {
 440 // Refract direction vector according to Snell law
 441 // Arguments:
 442 //            n1 - ref idx of first substance
 443 //            n2 - ref idx of second substance
 444 //   Returns: none
 445 //   On exit: dir is new direction
 446   Double_t sinref=(n1/n2)*TMath::Sin(dir.Theta());
 447   if(TMath::Abs(sinref)>1.) dir.SetXYZ(-999,-999,-999);
 448   else             dir.SetTheta(TMath::ASin(sinref));
 449 }//Refract()
 450 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 451 Double_t AliHMPIDRecon::HoughResponse()
 452 {
 453 //
 454 //    fIdxMip = mipId;
 455
 456 //
 457   Double_t kThetaMax=0.75;
 458   Int_t nChannels = (Int_t)(kThetaMax/fDTheta+0.5);
 459   TH1D *phots   = new TH1D("Rphot"  ,"phots"         ,nChannels,0,kThetaMax);
 460   TH1D *photsw  = new TH1D("RphotWeighted" ,"photsw" ,nChannels,0,kThetaMax);
 461   TH1D *resultw = new TH1D("resultw","resultw"       ,nChannels,0,kThetaMax);
 462   Int_t nBin = (Int_t)(kThetaMax/fDTheta);
 463   Int_t nCorrBand = (Int_t)(fWindowWidth/(2*fDTheta));
 464
 465   for (Int_t i=0; i< fPhotCnt; i++){//photon cadidates loop
 466     Double_t angle = fPhotCkov[i];  if(angle<0||angle>kThetaMax) continue;
 467     phots->Fill(angle);
 468     Int_t bin = (Int_t)(0.5+angle/(fDTheta));
 469     Double_t weight=1.;
 470     if(fIsWEIGHT){
 471       Double_t lowerlimit = ((Double_t)bin)*fDTheta - 0.5*fDTheta;  Double_t upperlimit = ((Double_t)bin)*fDTheta + 0.5*fDTheta;
 472       FindRingGeom(lowerlimit);
 473       Double_t areaLow  = GetRingArea();
 474       FindRingGeom(upperlimit);
 475       Double_t areaHigh = GetRingArea();
 476       Double_t diffArea = areaHigh - areaLow;
 477       if(diffArea>0) weight = 1./diffArea;
 478     }
 479     photsw->Fill(angle,weight);
 480     fPhotWei[i]=weight;
 481   }//photon candidates loop
 482
 483   for (Int_t i=1; i<=nBin;i++){
 484     Int_t bin1= i-nCorrBand;
 485     Int_t bin2= i+nCorrBand;
 486     if(bin1<1) bin1=1;
 487     if(bin2>nBin)bin2=nBin;
 488     Double_t sumPhots=phots->Integral(bin1,bin2);
 489     if(sumPhots<3) continue;                            // if less then 3 photons don't trust to this ring
 490     Double_t sumPhotsw=photsw->Integral(bin1,bin2);
 491     resultw->Fill((Double_t)((i+0.5)*fDTheta),sumPhotsw);
 492   }
 493 // evaluate the "BEST" theta ckov as the maximum value of histogramm
 494   Double_t *pVec = resultw->GetArray();
 495   Int_t locMax = TMath::LocMax(nBin,pVec);
 496   delete phots;delete photsw;delete resultw; // Reset and delete objects
 497
 498   return (Double_t)(locMax*fDTheta+0.5*fDTheta); //final most probable track theta ckov
 499 }//HoughResponse()
 500 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++