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 #include <AliESDfriendTrack.h>     //CkovAngle()
  31
  32 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  33 AliHMPIDRecon::AliHMPIDRecon():
  34   TTask("RichRec","RichPat"),
  35   fPhotCnt(-1),
  36   fPhotFlag(0x0),
  37   fPhotClusIndex(0x0),
  38   fPhotCkov(0x0),
  39   fPhotPhi(0x0),
  40   fPhotWei(0x0),
  41   fCkovSigma2(0),
  42   fIsWEIGHT(kFALSE),
  43   fDTheta(0.001),
  44   fWindowWidth(0.045),
  45   fRingArea(0),
  46   fRingAcc(0),
  47   fTrkDir(0,0,1),  // Just for test
  48   fTrkPos(30,40),  // Just for test
  49   fMipPos(0,0),
  50   fPc(0,0),
  51   fParam(AliHMPIDParam::Instance())
  52 {
  53 //..
  54 //init of data members
  55 //..
  56
  57   fParam->SetRefIdx(fParam->MeanIdxRad()); // initialization of ref index to a default one
  58 }
  59 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  60 void AliHMPIDRecon::InitVars(Int_t n)
  61 {
  62 //..
  63 //Init some variables
  64 //..
  65   if(n<=0) return;
  66   fPhotFlag = new Int_t[n];
  67   fPhotClusIndex  = new Int_t[n];
  68   fPhotCkov = new Double_t[n];
  69   fPhotPhi  = new Double_t[n];
  70   fPhotWei  = new Double_t[n];
  71 //
  72 }
  73 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  74 void AliHMPIDRecon::DeleteVars()const
  75 {
  76 //..
  77 //Delete variables
  78 //..
  79   delete [] fPhotFlag;
  80   delete [] fPhotClusIndex;
  81   delete [] fPhotCkov;
  82   delete [] fPhotPhi;
  83   delete [] fPhotWei;
  84 }
  85 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  86 void AliHMPIDRecon::CkovAngle(AliESDtrack *pTrk,TClonesArray *pCluLst,Int_t index,Double_t nmean,Float_t xRa,Float_t yRa)
  87 {
  88 // Pattern recognition method based on Hough transform
  89 // Arguments:   pTrk     - track for which Ckov angle is to be found
  90 //              pCluLst  - list of clusters for this chamber
  91 //   Returns:            - track ckov angle, [rad],
  92
  93
  94   AliESDfriendTrack *pFriendTrk = (AliESDfriendTrack*)pTrk->GetFriendTrack();
  95
  96   const Int_t nMinPhotAcc = 3;                      // Minimum number of photons required to perform the pattern recognition
  97
  98   Int_t nClusTot = pCluLst->GetEntries();
  99   if(nClusTot>fParam->MultCut()) fIsWEIGHT = kTRUE; // offset to take into account bkg in reconstruction
 100   else                           fIsWEIGHT = kFALSE;
 101
 102   InitVars(nClusTot);
 103
 104   Float_t xPc,yPc,th,ph;
 105   pTrk->GetHMPIDtrk(xPc,yPc,th,ph);        //initialize this track: th and ph angles at middle of RAD
 106   SetTrack(xRa,yRa,th,ph);
 107
 108   fParam->SetRefIdx(nmean);
 109
 110   Float_t mipX=-1,mipY=-1;
 111   Int_t chId=-1,mipQ=-1,sizeClu = -1;
 112
 113   fPhotCnt=0;
 114
 115   for (Int_t iClu=0; iClu<pCluLst->GetEntriesFast();iClu++){//clusters loop
 116     AliHMPIDCluster *pClu=(AliHMPIDCluster*)pCluLst->UncheckedAt(iClu);                       //get pointer to current cluster
 117     if(iClu == index) {                                                                       // this is the MIP! not a photon candidate: just store mip info
 118       mipX = pClu->X();
 119       mipY = pClu->Y();
 120       mipQ=(Int_t)pClu->Q();
 121       sizeClu=pClu->Size();
 122       continue;
 123     }
 124     chId=pClu->Ch();
 125     Double_t thetaCer,phiCer;
 126     if(FindPhotCkov(pClu->X(),pClu->Y(),thetaCer,phiCer)){                                    //find ckov angle for this  photon candidate
 127       fPhotCkov[fPhotCnt]=thetaCer;                                                           //actual theta Cerenkov (in TRS)
 128       fPhotPhi [fPhotCnt]=phiCer;
 129       fPhotClusIndex[fPhotCnt]=iClu;                                                             //actual phi   Cerenkov (in TRS): -pi to come back to "unusual" ref system (X,Y,-Z)
 130       fPhotCnt++;                                                                             //increment counter of photon candidates
 131     }
 132   }//clusters loop
 133
 134   pTrk->SetHMPIDmip(mipX,mipY,mipQ,fPhotCnt);                                                 //store mip info in any case
 135   pTrk->SetHMPIDcluIdx(chId,index+1000*sizeClu);                                              //set index of cluster
 136
 137   if(fPhotCnt<=nMinPhotAcc) {                                                                 //no reconstruction with <=3 photon candidates
 138     pTrk->SetHMPIDsignal(kNoPhotAccept);                                                      //set the appropriate flag
 139     return;
 140   }
 141
 142   fMipPos.Set(mipX,mipY);
 143
 144   TClonesArray *pPhotCluLst = pFriendTrk->GetHmpPhotClus();
 145
 146 //PATTERN RECOGNITION STARTED:
 147
 148   Int_t iNrec=FlagPhot(HoughResponse(),pCluLst,pPhotCluLst);                                                      //flag photons according to individual theta ckov with respect to most probable
 149
 150   pTrk->SetHMPIDmip(mipX,mipY,mipQ,iNrec);                                                    //store mip info
 151
 152   if(iNrec<1){
 153     pTrk->SetHMPIDsignal(kNoPhotAccept);                                                      //no photon candidates are accepted
 154     return;
 155   }
 156
 157   Double_t thetaC = FindRingCkov(pCluLst->GetEntries());                                    //find the best reconstructed theta Cherenkov
 158 //    FindRingGeom(thetaC,2);
 159   pTrk->SetHMPIDsignal(thetaC);                                                             //store theta Cherenkov
 160   pTrk->SetHMPIDchi2(fCkovSigma2);                                                          //store errors squared
 161
 162   DeleteVars();
 163 }//CkovAngle()
 164 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 165 Bool_t AliHMPIDRecon::FindPhotCkov(Double_t cluX,Double_t cluY,Double_t &thetaCer,Double_t &phiCer)
 166 {
 167 // Finds Cerenkov angle  for this photon candidate
 168 // Arguments: cluX,cluY - position of cadidate's cluster
 169 // Returns: Cerenkov angle
 170
 171   TVector3 dirCkov;
 172
 173   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();     //z position of middle of RAD
 174   TVector3 rad(fTrkPos.X(),fTrkPos.Y(),zRad);                        //impact point at middle of RAD
 175   TVector3  pc(cluX,cluY,0.5*fParam->WinThick()+fParam->GapIdx());   //mip at PC
 176   Double_t cluR = TMath::Sqrt((cluX-fTrkPos.X())*(cluX-fTrkPos.X())+
 177                               (cluY-fTrkPos.Y())*(cluY-fTrkPos.Y()));//ref. distance impact RAD-CLUSTER
 178   Double_t phi=(pc-rad).Phi();                                       //phi of photon
 179
 180   Double_t ckov1=0;
 181   Double_t ckov2=0.75+fTrkDir.Theta();                        //start to find theta cerenkov in DRS
 182   const Double_t kTol=0.01;
 183   Int_t iIterCnt = 0;
 184   while(1){
 185     if(iIterCnt>=50) return kFALSE;
 186     Double_t ckov=0.5*(ckov1+ckov2);
 187     dirCkov.SetMagThetaPhi(1,ckov,phi);
 188     TVector2 posC=TraceForward(dirCkov);                      //trace photon with actual angles
 189     Double_t dist=cluR-(posC-fTrkPos).Mod();                  //get distance between trial point and cluster position
 190     if(posC.X()==-999) dist = - 999;                          //total reflection problem
 191     iIterCnt++;                                               //counter step
 192     if     (dist> kTol) ckov1=ckov;                           //cluster @ larger ckov
 193     else if(dist<-kTol) ckov2=ckov;                           //cluster @ smaller ckov
 194     else{                                                     //precision achived: ckov in DRS found
 195       dirCkov.SetMagThetaPhi(1,ckov,phi);                     //
 196       Lors2Trs(dirCkov,thetaCer,phiCer);                       //find ckov (in TRS:the effective Cherenkov angle!)
 197       return kTRUE;
 198     }
 199   }
 200 }//FindPhotTheta()
 201 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 202 TVector2 AliHMPIDRecon::TraceForward(TVector3 dirCkov)const
 203 {
 204   //Trace forward a photon from (x,y) up to PC
 205   // Arguments: dirCkov photon vector in LORS
 206   //   Returns: pos of traced photon at PC
 207
 208   TVector2 pos(-999,-999);
 209   Double_t thetaCer = dirCkov.Theta();
 210   if(thetaCer > TMath::ASin(1./fParam->GetRefIdx())) return pos;          //total refraction on WIN-GAP boundary
 211   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();          //z position of middle of RAD
 212   TVector3  posCkov(fTrkPos.X(),fTrkPos.Y(),zRad);                        //RAD: photon position is track position @ middle of RAD
 213   Propagate(dirCkov,posCkov,           -0.5*fParam->WinThick());          //go to RAD-WIN boundary
 214   Refract  (dirCkov,         fParam->GetRefIdx(),fParam->WinIdx());       //RAD-WIN refraction
 215   Propagate(dirCkov,posCkov,            0.5*fParam->WinThick());          //go to WIN-GAP boundary
 216   Refract  (dirCkov,         fParam->WinIdx(),fParam->GapIdx());          //WIN-GAP refraction
 217   Propagate(dirCkov,posCkov,0.5*fParam->WinThick()+fParam->GapThick());   //go to PC
 218   pos.Set(posCkov.X(),posCkov.Y());
 219   return pos;
 220 }//TraceForward()
 221 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 222 void AliHMPIDRecon::Lors2Trs(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
 223 {
 224   //Theta Cerenkov reconstruction
 225   // Arguments: dirCkov photon vector in LORS
 226   //   Returns: thetaCer of photon in TRS
 227   //              phiCer of photon in TRS
 228 //  TVector3 dirTrk;
 229 //  dirTrk.SetMagThetaPhi(1,fTrkDir.Theta(),fTrkDir.Phi());
 230 //  Double_t thetaCer = TMath::ACos(dirCkov*dirTrk);
 231   TRotation mtheta;   mtheta.RotateY(-fTrkDir.Theta());
 232   TRotation mphi;       mphi.RotateZ(-fTrkDir.Phi());
 233   TRotation mrot=mtheta*mphi;
 234   TVector3 dirCkovTRS;
 235   dirCkovTRS=mrot*dirCkov;
 236   phiCer  = dirCkovTRS.Phi();                                          //actual value of the phi of the photon
 237   thetaCer= dirCkovTRS.Theta();                                        //actual value of thetaCerenkov of the photon
 238 }
 239 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 240 void AliHMPIDRecon::Trs2Lors(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
 241 {
 242   //Theta Cerenkov reconstruction
 243   // Arguments: dirCkov photon vector in TRS
 244   //   Returns: thetaCer of photon in LORS
 245   //              phiCer of photon in LORS
 246   TRotation mtheta;   mtheta.RotateY(fTrkDir.Theta());
 247   TRotation mphi;       mphi.RotateZ(fTrkDir.Phi());
 248   TRotation mrot=mphi*mtheta;
 249   TVector3 dirCkovLORS;
 250   dirCkovLORS=mrot*dirCkov;
 251   phiCer  = dirCkovLORS.Phi();                                          //actual value of the phi of the photon
 252   thetaCer= dirCkovLORS.Theta();                                        //actual value of thetaCerenkov of the photon
 253 }
 254 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 255 void AliHMPIDRecon::FindRingGeom(Double_t ckovAng,Int_t level)
 256 {
 257 // Find area covered in the PC acceptance
 258 // Arguments: ckovAng - cerenkov angle
 259 //            level   - precision in finding area and portion of ring accepted (multiple of 50)
 260 //   Returns: area of the ring in cm^2 for given theta ckov
 261
 262   Int_t kN=50*level;
 263   Int_t nPoints = 0;
 264   Double_t area=0;
 265
 266   Bool_t first=kFALSE;
 267   TVector2 pos1;
 268
 269   for(Int_t i=0;i<kN;i++){
 270    if(!first) {
 271       pos1=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                                    //find a good trace for the first photon
 272      if(pos1.X()==-999) continue;                                                                   //no area: open ring
 273      if(!fParam->IsInside(pos1.X(),pos1.Y(),0)) {
 274        pos1 = IntWithEdge(fMipPos,pos1);                                                            // find the very first intersection...
 275      } else {
 276        if(!AliHMPIDParam::IsInDead(pos1.X(),pos1.Y())) nPoints++;                                   //photon is accepted if not in dead zone
 277      }
 278      first=kTRUE;
 279      continue;
 280    }
 281    TVector2 pos2=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                              //trace the next photon
 282    if(pos2.X()==-999) continue;                                                                     //no area: open ring
 283    if(!fParam->IsInside(pos2.X(),pos2.Y(),0)) {
 284      pos2 = IntWithEdge(fMipPos,pos2);
 285    } else {
 286      if(!AliHMPIDParam::IsInDead(pos2.X(),pos2.Y())) nPoints++;                                     //photon is accepted if not in dead zone
 287    }
 288    area+=TMath::Abs((pos1-fMipPos).X()*(pos2-fMipPos).Y()-(pos1-fMipPos).Y()*(pos2-fMipPos).X());   //add area of the triangle...
 289    pos1 = pos2;
 290   }
 291 //---  find area and length of the ring;
 292   fRingAcc = (Double_t)nPoints/(Double_t)kN;
 293   area*=0.5;
 294   fRingArea = area;
 295 }//FindRingGeom()
 296 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 297 TVector2 AliHMPIDRecon::IntWithEdge(TVector2 p1,TVector2 p2)const
 298 {
 299 // It finds the intersection of the line for 2 points traced as photons
 300 // and the edge of a given PC
 301 // Arguments: 2 points obtained tracing the photons
 302 //   Returns: intersection point with detector (PC) edges
 303
 304   Double_t xmin = (p1.X()<p2.X())? p1.X():p2.X();
 305   Double_t xmax = (p1.X()<p2.X())? p2.X():p1.X();
 306   Double_t ymin = (p1.Y()<p2.Y())? p1.Y():p2.Y();
 307   Double_t ymax = (p1.Y()<p2.Y())? p2.Y():p1.Y();
 308
 309   Double_t m = TMath::Tan((p2-p1).Phi());
 310   TVector2 pint;
 311   //intersection with low  X
 312   pint.Set((Double_t)(p1.X() + (0-p1.Y())/m),0.);
 313   if(pint.X()>=0 && pint.X()<=fParam->SizeAllX() &&
 314      pint.X()>=xmin && pint.X()<=xmax            &&
 315      pint.Y()>=ymin && pint.Y()<=ymax) return pint;
 316   //intersection with high X
 317   pint.Set((Double_t)(p1.X() + (fParam->SizeAllY()-p1.Y())/m),(Double_t)(fParam->SizeAllY()));
 318   if(pint.X()>=0 && pint.X()<=fParam->SizeAllX() &&
 319      pint.X()>=xmin && pint.X()<=xmax            &&
 320      pint.Y()>=ymin && pint.Y()<=ymax) return pint;
 321   //intersection with left Y
 322   pint.Set(0.,(Double_t)(p1.Y() + m*(0-p1.X())));
 323   if(pint.Y()>=0 && pint.Y()<=fParam->SizeAllY() &&
 324      pint.Y()>=ymin && pint.Y()<=ymax            &&
 325      pint.X()>=xmin && pint.X()<=xmax) return pint;
 326   //intersection with righ Y
 327   pint.Set((Double_t)(fParam->SizeAllX()),(Double_t)(p1.Y() + m*(fParam->SizeAllX()-p1.X())));
 328   if(pint.Y()>=0 && pint.Y()<=fParam->SizeAllY() &&
 329      pint.Y()>=ymin && pint.Y()<=ymax            &&
 330      pint.X()>=xmin && pint.X()<=xmax) return pint;
 331   return p1;
 332 }//IntWithEdge()
 333 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 334 Double_t AliHMPIDRecon::FindRingCkov(Int_t)
 335 {
 336 // 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
 337 // collecting errors for all single Ckov candidates thetas. (Assuming they are independent)
 338 // Arguments: iNclus- total number of clusters in chamber for background estimation
 339 //    Return: best estimation of track Theta ckov
 340
 341   Double_t wei = 0.;
 342   Double_t weightThetaCerenkov = 0.;
 343
 344   Double_t ckovMin=9999.,ckovMax=0.;
 345   Double_t sigma2 = 0;   //to collect error squared for this ring
 346
 347   for(Int_t i=0;i<fPhotCnt;i++){//candidates loop
 348     if(fPhotFlag[i] == 2){
 349       if(fPhotCkov[i]<ckovMin) ckovMin=fPhotCkov[i];                         //find max and min Theta ckov from all candidates within probable window
 350       if(fPhotCkov[i]>ckovMax) ckovMax=fPhotCkov[i];
 351       weightThetaCerenkov += fPhotCkov[i]*fPhotWei[i];
 352       wei += fPhotWei[i];                                                    //collect weight as sum of all candidate weghts
 353
 354       sigma2 += 1./fParam->Sigma2(fTrkDir.Theta(),fTrkDir.Phi(),fPhotCkov[i],fPhotPhi[i]);
 355     }
 356   }//candidates loop
 357
 358   if(sigma2>0) fCkovSigma2=1./sigma2;
 359   else         fCkovSigma2=1e10;
 360
 361   if(wei != 0.) weightThetaCerenkov /= wei; else weightThetaCerenkov = 0.;
 362   return weightThetaCerenkov;
 363 }//FindCkovRing()
 364 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 365 Int_t AliHMPIDRecon::FlagPhot(Double_t ckov,TClonesArray *pCluLst, TClonesArray *pPhotCluLst)
 366 {
 367 // Flag photon candidates if their individual ckov angle is inside the window around ckov angle returned by  HoughResponse()
 368 // Arguments: ckov- value of most probable ckov angle for track as returned by HoughResponse()
 369 //   Returns: number of photon candidates happened to be inside the window
 370
 371 // Photon Flag:  Flag = 0 initial set;
 372 //               Flag = 1 good candidate (charge compatible with photon);
 373 //               Flag = 2 photon used for the ring;
 374   Int_t *PhotIndex = new Int_t[fPhotCnt];
 375
 376   Int_t steps = (Int_t)((ckov )/ fDTheta); //how many times we need to have fDTheta to fill the distance between 0  and thetaCkovHough
 377
 378   Double_t tmin = (Double_t)(steps - 1)*fDTheta;
 379   Double_t tmax = (Double_t)(steps)*fDTheta;
 380   Double_t tavg = 0.5*(tmin+tmax);
 381
 382   tmin = tavg - 0.5*fWindowWidth;  tmax = tavg + 0.5*fWindowWidth;
 383
 384   Int_t iInsideCnt = 0; //count photons which Theta ckov inside the window
 385   for(Int_t i=0;i<fPhotCnt;i++){//photon candidates loop
 386     fPhotFlag[i] = 0;
 387     if(fPhotCkov[i] >= tmin && fPhotCkov[i] <= tmax)    {
 388       fPhotFlag[i]=2;
 389       PhotIndex[iInsideCnt]=fPhotClusIndex[i];
 390       iInsideCnt++;
 391     }
 392   }
 393
 394   Int_t nPhot = 0;
 395
 396   for (Int_t iClu=0; iClu<pCluLst->GetEntriesFast();iClu++){//clusters loop
 397     AliHMPIDCluster *pClu=(AliHMPIDCluster*)pCluLst->UncheckedAt(iClu);                       //get pointer to current cluster
 398     for(Int_t j=0; j<iInsideCnt; j++){
 399       if(iClu==PhotIndex[j]) {
 400       new ((*pPhotCluLst)[nPhot++]) AliHMPIDCluster(*pClu);  //add this raw cluster
 401      }
 402     }
 403   }
 404
 405   delete [] PhotIndex;
 406
 407   return iInsideCnt;
 408
 409 }//FlagPhot()
 410 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 411 TVector2 AliHMPIDRecon::TracePhot(Double_t ckovThe,Double_t ckovPhi)const
 412 {
 413 // Trace a single Ckov photon from emission point somewhere in radiator up to photocathode taking into account ref indexes of materials it travereses
 414 // Arguments: ckovThe,ckovPhi- photon ckov angles in TRS, [rad]
 415 //   Returns: distance between photon point on PC and track projection
 416
 417   Double_t theta,phi;
 418   TVector3  dirTRS,dirLORS;
 419   dirTRS.SetMagThetaPhi(1,ckovThe,ckovPhi);                     //photon in TRS
 420   Trs2Lors(dirTRS,theta,phi);
 421   dirLORS.SetMagThetaPhi(1,theta,phi);                          //photon in LORS
 422   return TraceForward(dirLORS);                                 //now foward tracing
 423 }//TracePhot()
 424 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 425 void AliHMPIDRecon::Propagate(const TVector3 dir,TVector3 &pos,Double_t z)const
 426 {
 427 // Finds an intersection point between a line and XY plane shifted along Z.
 428 // Arguments:  dir,pos   - vector along the line and any point of the line
 429 //             z         - z coordinate of plain
 430 //   Returns:  none
 431 //   On exit:  pos is the position if this intesection if any
 432   static TVector3 nrm(0,0,1);
 433          TVector3 pnt(0,0,z);
 434
 435   TVector3 diff=pnt-pos;
 436   Double_t sint=(nrm*diff)/(nrm*dir);
 437   pos+=sint*dir;
 438 }//Propagate()
 439 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 440 void AliHMPIDRecon::Refract(TVector3 &dir,Double_t n1,Double_t n2)const
 441 {
 442 // Refract direction vector according to Snell law
 443 // Arguments:
 444 //            n1 - ref idx of first substance
 445 //            n2 - ref idx of second substance
 446 //   Returns: none
 447 //   On exit: dir is new direction
 448   Double_t sinref=(n1/n2)*TMath::Sin(dir.Theta());
 449   if(TMath::Abs(sinref)>1.) dir.SetXYZ(-999,-999,-999);
 450   else             dir.SetTheta(TMath::ASin(sinref));
 451 }//Refract()
 452 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 453 Double_t AliHMPIDRecon::HoughResponse()
 454 {
 455 //
 456 //    fIdxMip = mipId;
 457
 458 //
 459   Double_t kThetaMax=0.75;
 460   Int_t nChannels = (Int_t)(kThetaMax/fDTheta+0.5);
 461   TH1D *phots   = new TH1D("Rphot"  ,"phots"         ,nChannels,0,kThetaMax);
 462   TH1D *photsw  = new TH1D("RphotWeighted" ,"photsw" ,nChannels,0,kThetaMax);
 463   TH1D *resultw = new TH1D("resultw","resultw"       ,nChannels,0,kThetaMax);
 464   Int_t nBin = (Int_t)(kThetaMax/fDTheta);
 465   Int_t nCorrBand = (Int_t)(fWindowWidth/(2*fDTheta));
 466
 467   for (Int_t i=0; i< fPhotCnt; i++){//photon cadidates loop
 468     Double_t angle = fPhotCkov[i];  if(angle<0||angle>kThetaMax) continue;
 469     phots->Fill(angle);
 470     Int_t bin = (Int_t)(0.5+angle/(fDTheta));
 471     Double_t weight=1.;
 472     if(fIsWEIGHT){
 473       Double_t lowerlimit = ((Double_t)bin)*fDTheta - 0.5*fDTheta;  Double_t upperlimit = ((Double_t)bin)*fDTheta + 0.5*fDTheta;
 474       FindRingGeom(lowerlimit);
 475       Double_t areaLow  = GetRingArea();
 476       FindRingGeom(upperlimit);
 477       Double_t areaHigh = GetRingArea();
 478       Double_t diffArea = areaHigh - areaLow;
 479       if(diffArea>0) weight = 1./diffArea;
 480     }
 481     photsw->Fill(angle,weight);
 482     fPhotWei[i]=weight;
 483   }//photon candidates loop
 484
 485   for (Int_t i=1; i<=nBin;i++){
 486     Int_t bin1= i-nCorrBand;
 487     Int_t bin2= i+nCorrBand;
 488     if(bin1<1) bin1=1;
 489     if(bin2>nBin)bin2=nBin;
 490     Double_t sumPhots=phots->Integral(bin1,bin2);
 491     if(sumPhots<3) continue;                            // if less then 3 photons don't trust to this ring
 492     Double_t sumPhotsw=photsw->Integral(bin1,bin2);
 493     resultw->Fill((Double_t)((i+0.5)*fDTheta),sumPhotsw);
 494   }
 495 // evaluate the "BEST" theta ckov as the maximum value of histogramm
 496   Double_t *pVec = resultw->GetArray();
 497   Int_t locMax = TMath::LocMax(nBin,pVec);
 498   delete phots;delete photsw;delete resultw; // Reset and delete objects
 499
 500   return (Double_t)(locMax*fDTheta+0.5*fDTheta); //final most probable track theta ckov
 501 }//HoughResponse()
 502 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 503   Double_t AliHMPIDRecon::FindRingExt(Double_t ckov,Int_t ch,Double_t xPc,Double_t yPc,Double_t thRa,Double_t phRa)
 504 {
 505 // To find the acceptance of the ring even from external inputs.
 506 //
 507 //
 508   Double_t xRa = xPc - (fParam->RadThick()+fParam->WinThick()+fParam->GapThick())*TMath::Cos(phRa)*TMath::Tan(thRa); //just linear extrapolation back to RAD
 509   Double_t yRa = yPc - (fParam->RadThick()+fParam->WinThick()+fParam->GapThick())*TMath::Sin(phRa)*TMath::Tan(thRa);
 510
 511   Int_t nStep = 500;
 512   Int_t nPhi = 0;
 513
 514   Int_t ipc,ipadx,ipady;
 515
 516   if(ckov>0){
 517     SetTrack(xRa,yRa,thRa,phRa);
 518     for(Int_t j=0;j<nStep;j++){
 519       TVector2 pos; pos=TracePhot(ckov,j*TMath::TwoPi()/(Double_t)(nStep-1));
 520       if(fParam->IsInDead(pos.X(),pos.Y())) continue;
 521       fParam->Lors2Pad(pos.X(),pos.Y(),ipc,ipadx,ipady);
 522       ipadx+=(ipc%2)*fParam->kPadPcX;
 523       ipady+=(ipc/2)*fParam->kPadPcY;
 524       if(fParam->IsDeadPad(ipadx,ipady,ch)) continue;
 525       nPhi++;
 526     }//point loop
 527   return ((Double_t)nPhi/(Double_t)nStep);
 528   }//if
 529   return -1;
 530 }