792da47cbc64c909f162de2bed36735a08692561
[u/mrichter/AliRoot.git] / 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 #include <AliESDfriendTrack.h>     //CkovAngle()
31
32 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
33 AliHMPIDRecon::AliHMPIDRecon():
34   TNamed("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
97   InitVars(nClusTot);
98   
99   Float_t xPc,yPc,th,ph;
100   pTrk->GetHMPIDtrk(xPc,yPc,th,ph);        //initialize this track: th and ph angles at middle of RAD 
101   SetTrack(xRa,yRa,th,ph);
102
103   fParam->SetRefIdx(nmean);
104
105   Float_t mipX=-1,mipY=-1;
106   Int_t chId=-1,mipQ=-1,sizeClu = -1;
107   
108   fPhotCnt=0;
109   
110   Int_t nPads = 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     nPads+=pClu->Size();    
115     if(iClu == index) {                                                                       // this is the MIP! not a photon candidate: just store mip info
116       mipX = pClu->X();
117       mipY = pClu->Y();
118       mipQ=(Int_t)pClu->Q();
119       sizeClu=pClu->Size();
120       continue;                                                             
121     }
122     chId=pClu->Ch();
123     if(pClu->Q()>2*fParam->QCut()) continue;
124     Double_t thetaCer,phiCer;
125     if(FindPhotCkov(pClu->X(),pClu->Y(),thetaCer,phiCer)){                                    //find ckov angle for this  photon candidate
126       fPhotCkov[fPhotCnt]=thetaCer;                                                           //actual theta Cerenkov (in TRS)
127       fPhotPhi [fPhotCnt]=phiCer;
128       fPhotClusIndex[fPhotCnt]=iClu;                                                             //actual phi   Cerenkov (in TRS): -pi to come back to "unusual" ref system (X,Y,-Z)
129       fPhotCnt++;                                                                             //increment counter of photon candidates
130     }
131   }//clusters loop
132
133   pTrk->SetHMPIDmip(mipX,mipY,mipQ,fPhotCnt);                                                 //store mip info in any case 
134   pTrk->SetHMPIDcluIdx(chId,index+1000*sizeClu);                                              //set index of cluster
135   
136   if(fPhotCnt<nMinPhotAcc) {                                                                 //no reconstruction with <=3 photon candidates
137     pTrk->SetHMPIDsignal(kNoPhotAccept);                                                      //set the appropriate flag
138     return;
139   }
140     
141   fMipPos.Set(mipX,mipY);
142     
143 //PATTERN RECOGNITION STARTED: 
144   if(fPhotCnt>fParam->MultCut()) fIsWEIGHT = kTRUE; // offset to take into account bkg in reconstruction
145   else                           fIsWEIGHT = kFALSE;
146     
147   Int_t iNrec=FlagPhot(HoughResponse(),pCluLst,pTrk);                                                      //flag photons according to individual theta ckov with respect to most probable
148   
149   pTrk->SetHMPIDmip(mipX,mipY,mipQ,iNrec);                                                  //store mip info 
150
151   if(iNrec<nMinPhotAcc){
152     pTrk->SetHMPIDsignal(kNoPhotAccept);                                                    //no photon candidates are accepted
153     return;
154   }
155   
156   Int_t occupancy = (Int_t)(1000*(nPads/(6.*80.*48.))); 
157   
158   Double_t thetaC = FindRingCkov(pCluLst->GetEntries());                                    //find the best reconstructed theta Cherenkov
159 //    FindRingGeom(thetaC,2);
160   pTrk->SetHMPIDsignal(thetaC+occupancy);                                                   //store theta Cherenkov and chmaber occupancy
161   pTrk->SetHMPIDchi2(fCkovSigma2);                                                          //store experimental ring angular resolution squared
162   
163   DeleteVars();
164 }//CkovAngle()
165 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
166 Bool_t AliHMPIDRecon::FindPhotCkov(Double_t cluX,Double_t cluY,Double_t &thetaCer,Double_t &phiCer)
167 {
168 // Finds Cerenkov angle  for this photon candidate
169 // Arguments: cluX,cluY - position of cadidate's cluster  
170 // Returns: Cerenkov angle 
171
172   TVector3 dirCkov;
173   
174   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();     //z position of middle of RAD
175   TVector3 rad(fTrkPos.X(),fTrkPos.Y(),zRad);                        //impact point at middle of RAD
176   TVector3  pc(cluX,cluY,0.5*fParam->WinThick()+fParam->GapIdx());   //mip at PC
177   Double_t cluR = TMath::Sqrt((cluX-fTrkPos.X())*(cluX-fTrkPos.X())+
178                               (cluY-fTrkPos.Y())*(cluY-fTrkPos.Y()));//ref. distance impact RAD-CLUSTER   
179   Double_t phi=(pc-rad).Phi();                                       //phi of photon
180     
181   Double_t ckov1=0;
182   Double_t ckov2=0.75+fTrkDir.Theta();                        //start to find theta cerenkov in DRS
183   const Double_t kTol=0.01;
184   Int_t iIterCnt = 0;
185   while(1){
186     if(iIterCnt>=50) return kFALSE;
187     Double_t ckov=0.5*(ckov1+ckov2);
188     dirCkov.SetMagThetaPhi(1,ckov,phi);
189     TVector2 posC=TraceForward(dirCkov);                      //trace photon with actual angles
190     Double_t dist=cluR-(posC-fTrkPos).Mod();                  //get distance between trial point and cluster position
191     if(posC.X()==-999) dist = - 999;                          //total reflection problem
192     iIterCnt++;                                               //counter step
193     if     (dist> kTol) ckov1=ckov;                           //cluster @ larger ckov
194     else if(dist<-kTol) ckov2=ckov;                           //cluster @ smaller ckov
195     else{                                                     //precision achived: ckov in DRS found
196       dirCkov.SetMagThetaPhi(1,ckov,phi);                     //
197       Lors2Trs(dirCkov,thetaCer,phiCer);                       //find ckov (in TRS:the effective Cherenkov angle!)
198       return kTRUE;
199     }
200   }
201 }//FindPhotTheta()
202 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
203 TVector2 AliHMPIDRecon::TraceForward(TVector3 dirCkov)const
204 {
205   //Trace forward a photon from (x,y) up to PC
206   // Arguments: dirCkov photon vector in LORS
207   //   Returns: pos of traced photon at PC
208   
209   TVector2 pos(-999,-999);
210   Double_t thetaCer = dirCkov.Theta();
211   if(thetaCer > TMath::ASin(1./fParam->GetRefIdx())) return pos;          //total refraction on WIN-GAP boundary
212   Double_t zRad= -0.5*fParam->RadThick()-0.5*fParam->WinThick();          //z position of middle of RAD
213   TVector3  posCkov(fTrkPos.X(),fTrkPos.Y(),zRad);                        //RAD: photon position is track position @ middle of RAD 
214   Propagate(dirCkov,posCkov,           -0.5*fParam->WinThick());          //go to RAD-WIN boundary  
215   Refract  (dirCkov,         fParam->GetRefIdx(),fParam->WinIdx());       //RAD-WIN refraction
216   Propagate(dirCkov,posCkov,            0.5*fParam->WinThick());          //go to WIN-GAP boundary
217   Refract  (dirCkov,         fParam->WinIdx(),fParam->GapIdx());          //WIN-GAP refraction
218   Propagate(dirCkov,posCkov,0.5*fParam->WinThick()+fParam->GapThick());   //go to PC
219   pos.Set(posCkov.X(),posCkov.Y());
220   return pos;
221 }//TraceForward()
222 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
223 void AliHMPIDRecon::Lors2Trs(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
224 {
225   //Theta Cerenkov reconstruction 
226   // Arguments: dirCkov photon vector in LORS
227   //   Returns: thetaCer of photon in TRS
228   //              phiCer of photon in TRS
229 //  TVector3 dirTrk;
230 //  dirTrk.SetMagThetaPhi(1,fTrkDir.Theta(),fTrkDir.Phi());
231 //  Double_t thetaCer = TMath::ACos(dirCkov*dirTrk);
232   TRotation mtheta;   mtheta.RotateY(-fTrkDir.Theta());
233   TRotation mphi;       mphi.RotateZ(-fTrkDir.Phi());
234   TRotation mrot=mtheta*mphi;
235   TVector3 dirCkovTRS;
236   dirCkovTRS=mrot*dirCkov;
237   phiCer  = dirCkovTRS.Phi();                                          //actual value of the phi of the photon
238   thetaCer= dirCkovTRS.Theta();                                        //actual value of thetaCerenkov of the photon
239 }
240 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
241 void AliHMPIDRecon::Trs2Lors(TVector3 dirCkov,Double_t &thetaCer,Double_t &phiCer)const
242 {
243   //Theta Cerenkov reconstruction 
244   // Arguments: dirCkov photon vector in TRS
245   //   Returns: thetaCer of photon in LORS
246   //              phiCer of photon in LORS
247   TRotation mtheta;   mtheta.RotateY(fTrkDir.Theta());
248   TRotation mphi;       mphi.RotateZ(fTrkDir.Phi());
249   TRotation mrot=mphi*mtheta;
250   TVector3 dirCkovLORS;
251   dirCkovLORS=mrot*dirCkov;
252   phiCer  = dirCkovLORS.Phi();                                          //actual value of the phi of the photon
253   thetaCer= dirCkovLORS.Theta();                                        //actual value of thetaCerenkov of the photon
254 }
255 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
256 void AliHMPIDRecon::FindRingGeom(Double_t ckovAng,Int_t level)
257 {
258 // Find area covered in the PC acceptance
259 // Arguments: ckovAng - cerenkov angle
260 //            level   - precision in finding area and portion of ring accepted (multiple of 50)
261 //   Returns: area of the ring in cm^2 for given theta ckov
262    
263   Int_t kN=50*level;
264   Int_t nPoints = 0;
265   Double_t area=0;
266   
267   Bool_t first=kFALSE;
268   TVector2 pos1;
269   
270   for(Int_t i=0;i<kN;i++){
271    if(!first) {
272       pos1=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                                    //find a good trace for the first photon
273      if(pos1.X()==-999) continue;                                                                   //no area: open ring                  
274      if(!fParam->IsInside(pos1.X(),pos1.Y(),0)) {
275        pos1 = IntWithEdge(fMipPos,pos1);                                                            // find the very first intersection...
276      } else {
277        if(!AliHMPIDParam::IsInDead(pos1.X(),pos1.Y())) nPoints++;                                   //photon is accepted if not in dead zone
278      }
279      first=kTRUE;
280      continue;
281    }
282    TVector2 pos2=TracePhot(ckovAng,Double_t(TMath::TwoPi()*(i+1)/kN));                              //trace the next photon
283    if(pos2.X()==-999) continue;                                                                     //no area: open ring             
284    if(!fParam->IsInside(pos2.X(),pos2.Y(),0)) {
285      pos2 = IntWithEdge(fMipPos,pos2);
286    } else {
287      if(!AliHMPIDParam::IsInDead(pos2.X(),pos2.Y())) nPoints++;                                     //photon is accepted if not in dead zone
288    }
289    area+=TMath::Abs((pos1-fMipPos).X()*(pos2-fMipPos).Y()-(pos1-fMipPos).Y()*(pos2-fMipPos).X());   //add area of the triangle...            
290    pos1 = pos2;
291   }
292 //---  find area and length of the ring;
293   fRingAcc = (Double_t)nPoints/(Double_t)kN;
294   area*=0.5;
295   fRingArea = area;
296 }//FindRingGeom()
297 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
298 TVector2 AliHMPIDRecon::IntWithEdge(TVector2 p1,TVector2 p2)const
299 {
300 // It finds the intersection of the line for 2 points traced as photons
301 // and the edge of a given PC
302 // Arguments: 2 points obtained tracing the photons
303 //   Returns: intersection point with detector (PC) edges
304
305   Double_t xmin = (p1.X()<p2.X())? p1.X():p2.X(); 
306   Double_t xmax = (p1.X()<p2.X())? p2.X():p1.X(); 
307   Double_t ymin = (p1.Y()<p2.Y())? p1.Y():p2.Y(); 
308   Double_t ymax = (p1.Y()<p2.Y())? p2.Y():p1.Y(); 
309   
310   Double_t m = TMath::Tan((p2-p1).Phi());
311   TVector2 pint;
312   //intersection with low  X
313   pint.Set((Double_t)(p1.X() + (0-p1.Y())/m),0.);
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 high X  
318   pint.Set((Double_t)(p1.X() + (fParam->SizeAllY()-p1.Y())/m),(Double_t)(fParam->SizeAllY()));
319   if(pint.X()>=0 && pint.X()<=fParam->SizeAllX() &&
320      pint.X()>=xmin && pint.X()<=xmax            &&
321      pint.Y()>=ymin && pint.Y()<=ymax) return pint;
322   //intersection with left Y  
323   pint.Set(0.,(Double_t)(p1.Y() + m*(0-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   //intersection with righ Y  
328   pint.Set((Double_t)(fParam->SizeAllX()),(Double_t)(p1.Y() + m*(fParam->SizeAllX()-p1.X())));
329   if(pint.Y()>=0 && pint.Y()<=fParam->SizeAllY() &&
330      pint.Y()>=ymin && pint.Y()<=ymax            &&
331      pint.X()>=xmin && pint.X()<=xmax) return pint;
332   return p1;
333 }//IntWithEdge()
334 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
335 Double_t AliHMPIDRecon::FindRingCkov(Int_t)
336 {
337 // 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
338 // collecting errors for all single Ckov candidates thetas. (Assuming they are independent)  
339 // Arguments: iNclus- total number of clusters in chamber for background estimation
340 //    Return: best estimation of track Theta ckov
341
342   Double_t wei = 0.;
343   Double_t weightThetaCerenkov = 0.;
344
345   Double_t ckovMin=9999.,ckovMax=0.;
346   Double_t sigma2 = 0;   //to collect error squared for this ring
347   
348   for(Int_t i=0;i<fPhotCnt;i++){//candidates loop
349     if(fPhotFlag[i] == 2){
350       if(fPhotCkov[i]<ckovMin) ckovMin=fPhotCkov[i];                         //find max and min Theta ckov from all candidates within probable window
351       if(fPhotCkov[i]>ckovMax) ckovMax=fPhotCkov[i]; 
352       weightThetaCerenkov += fPhotCkov[i]*fPhotWei[i];
353       wei += fPhotWei[i];                                                    //collect weight as sum of all candidate weghts   
354       
355       sigma2 += 1./fParam->Sigma2(fTrkDir.Theta(),fTrkDir.Phi(),fPhotCkov[i],fPhotPhi[i]);
356     }
357   }//candidates loop
358   
359   if(sigma2>0) fCkovSigma2=1./sigma2;
360   else         fCkovSigma2=1e10;  
361   
362   if(wei != 0.) weightThetaCerenkov /= wei; else weightThetaCerenkov = 0.;
363   return weightThetaCerenkov;
364 }//FindCkovRing()
365 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
366 Int_t AliHMPIDRecon::FlagPhot(Double_t ckov,TClonesArray *pCluLst, AliESDtrack *pTrk)
367 {
368 // Flag photon candidates if their individual ckov angle is inside the window around ckov angle returned by  HoughResponse()
369 // Arguments: ckov- value of most probable ckov angle for track as returned by HoughResponse()
370 //   Returns: number of photon candidates happened to be inside the window
371
372 // Photon Flag:  Flag = 0 initial set; 
373 //               Flag = 1 good candidate (charge compatible with photon); 
374 //               Flag = 2 photon used for the ring;
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       AddObjectToFriends(pCluLst,i,pTrk);
390       iInsideCnt++;
391     }
392   }
393       
394   return iInsideCnt;
395   
396 }//FlagPhot()
397 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
398 void  AliHMPIDRecon::AddObjectToFriends(TClonesArray *pCluLst, Int_t photonIndex, AliESDtrack *pTrk)
399 {
400 // Add AliHMPIDcluster object to ESD friends
401     
402   AliHMPIDCluster *pClu=(AliHMPIDCluster*)pCluLst->UncheckedAt(fPhotClusIndex[photonIndex]);      
403   AliHMPIDCluster *pClus = new AliHMPIDCluster(*pClu);
404   pClus->SetChi2(fPhotCkov[photonIndex]);  
405   pTrk->AddCalibObject(pClus);   
406 }    
407 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
408 TVector2 AliHMPIDRecon::TracePhot(Double_t ckovThe,Double_t ckovPhi)const
409 {
410 // Trace a single Ckov photon from emission point somewhere in radiator up to photocathode taking into account ref indexes of materials it travereses
411 // Arguments: ckovThe,ckovPhi- photon ckov angles in TRS, [rad]
412 //   Returns: distance between photon point on PC and track projection  
413   
414   Double_t theta,phi;
415   TVector3  dirTRS,dirLORS;   
416   dirTRS.SetMagThetaPhi(1,ckovThe,ckovPhi);                     //photon in TRS
417   Trs2Lors(dirTRS,theta,phi);
418   dirLORS.SetMagThetaPhi(1,theta,phi);                          //photon in LORS
419   return TraceForward(dirLORS);                                 //now foward tracing
420 }//TracePhot()
421 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
422 void AliHMPIDRecon::Propagate(const TVector3 dir,TVector3 &pos,Double_t z)const
423 {
424 // Finds an intersection point between a line and XY plane shifted along Z.
425 // Arguments:  dir,pos   - vector along the line and any point of the line
426 //             z         - z coordinate of plain 
427 //   Returns:  none
428 //   On exit:  pos is the position if this intesection if any
429   static TVector3 nrm(0,0,1); 
430          TVector3 pnt(0,0,z);
431   
432   TVector3 diff=pnt-pos;
433   Double_t sint=(nrm*diff)/(nrm*dir);
434   pos+=sint*dir;
435 }//Propagate()
436 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
437 void AliHMPIDRecon::Refract(TVector3 &dir,Double_t n1,Double_t n2)const
438 {
439 // Refract direction vector according to Snell law
440 // Arguments: 
441 //            n1 - ref idx of first substance
442 //            n2 - ref idx of second substance
443 //   Returns: none
444 //   On exit: dir is new direction
445   Double_t sinref=(n1/n2)*TMath::Sin(dir.Theta());
446   if(TMath::Abs(sinref)>1.) dir.SetXYZ(-999,-999,-999);
447   else             dir.SetTheta(TMath::ASin(sinref));
448 }//Refract()
449 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
450 Double_t AliHMPIDRecon::HoughResponse()
451 {
452 //
453 //    fIdxMip = mipId;
454
455 //       
456   Double_t kThetaMax=0.75;
457   Int_t nChannels = (Int_t)(kThetaMax/fDTheta+0.5);
458   TH1D *phots   = new TH1D("Rphot"  ,"phots"         ,nChannels,0,kThetaMax);
459   TH1D *photsw  = new TH1D("RphotWeighted" ,"photsw" ,nChannels,0,kThetaMax);
460   TH1D *resultw = new TH1D("resultw","resultw"       ,nChannels,0,kThetaMax);
461   Int_t nBin = (Int_t)(kThetaMax/fDTheta);
462   Int_t nCorrBand = (Int_t)(fWindowWidth/(2*fDTheta));
463   
464   for (Int_t i=0; i< fPhotCnt; i++){//photon cadidates loop
465     Double_t angle = fPhotCkov[i];  if(angle<0||angle>kThetaMax) continue;
466     phots->Fill(angle);
467     Int_t bin = (Int_t)(0.5+angle/(fDTheta));
468     Double_t weight=1.;
469     if(fIsWEIGHT){
470       Double_t lowerlimit = ((Double_t)bin)*fDTheta - 0.5*fDTheta;  Double_t upperlimit = ((Double_t)bin)*fDTheta + 0.5*fDTheta;
471       FindRingGeom(lowerlimit);
472       Double_t areaLow  = GetRingArea();
473       FindRingGeom(upperlimit);
474       Double_t areaHigh = GetRingArea();
475       Double_t diffArea = areaHigh - areaLow;
476       if(diffArea>0) weight = 1./diffArea;
477     }
478     photsw->Fill(angle,weight);
479     fPhotWei[i]=weight;
480   }//photon candidates loop 
481    
482   for (Int_t i=1; i<=nBin;i++){
483     Int_t bin1= i-nCorrBand;
484     Int_t bin2= i+nCorrBand;
485     if(bin1<1) bin1=1;
486     if(bin2>nBin)bin2=nBin;
487     Double_t sumPhots=phots->Integral(bin1,bin2);
488     if(sumPhots<3) continue;                            // if less then 3 photons don't trust to this ring
489     Double_t sumPhotsw=photsw->Integral(bin1,bin2);
490     if((Double_t)((i+0.5)*fDTheta)>0.7) continue;
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 //++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
501   Double_t AliHMPIDRecon::FindRingExt(Double_t ckov,Int_t ch,Double_t xPc,Double_t yPc,Double_t thRa,Double_t phRa)
502 {
503 // To find the acceptance of the ring even from external inputs. 
504 //    
505 //       
506   Double_t xRa = xPc - (fParam->RadThick()+fParam->WinThick()+fParam->GapThick())*TMath::Cos(phRa)*TMath::Tan(thRa); //just linear extrapolation back to RAD
507   Double_t yRa = yPc - (fParam->RadThick()+fParam->WinThick()+fParam->GapThick())*TMath::Sin(phRa)*TMath::Tan(thRa);
508   
509   Int_t nStep = 500;
510   Int_t nPhi = 0;  
511
512   Int_t ipc,ipadx,ipady;
513     
514   if(ckov>0){
515     SetTrack(xRa,yRa,thRa,phRa);
516     for(Int_t j=0;j<nStep;j++){
517       TVector2 pos; pos=TracePhot(ckov,j*TMath::TwoPi()/(Double_t)(nStep-1));
518       if(fParam->IsInDead(pos.X(),pos.Y())) continue;
519       fParam->Lors2Pad(pos.X(),pos.Y(),ipc,ipadx,ipady);
520       ipadx+=(ipc%2)*fParam->kPadPcX;
521       ipady+=(ipc/2)*fParam->kPadPcY;
522       if(ipadx<0 || ipady>160 || ipady<0 || ipady>144 || ch<0 || ch>6) continue;
523       if(fParam->IsDeadPad(ipadx,ipady,ch)) continue;
524       nPhi++;
525     }//point loop
526   return ((Double_t)nPhi/(Double_t)nStep); 
527   }//if
528   return -1;
529 }