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