1 /**************************************************************************
2 * Copyright(c) 1998-2003, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
16 //-----------------------------------------------------------------
17 // Implementation of the vertexer from ESD tracks
19 // Origin: AliITSVertexerTracks
21 // andrea.dainese@pd.infn.it
23 // massimo.masera@to.infn.it
24 // Moved to STEER and adapted to ESD tracks:
25 // F.Prino, Torino, prino@to.infn.it
26 //-----------------------------------------------------------------
28 //---- Root headers --------
30 //---- AliRoot headers -----
31 #include "AliStrLine.h"
32 #include "AliVertexerTracks.h"
34 #include "AliESDtrack.h"
36 ClassImp(AliVertexerTracks)
39 //----------------------------------------------------------------------------
40 AliVertexerTracks::AliVertexerTracks():
44 // Default constructor
51 //-----------------------------------------------------------------------------
52 AliVertexerTracks::AliVertexerTracks(Double_t xStart, Double_t yStart):
56 // Standard constructor
58 SetVtxStart(xStart,yStart);
63 //-----------------------------------------------------------------------------
64 AliVertexerTracks::~AliVertexerTracks() {
66 // The objects poited by the following pointers are not owned
67 // by this class and are not deleted
69 //----------------------------------------------------------------------------
70 Int_t AliVertexerTracks::PrepareTracks(TTree &trkTree) {
72 // Propagate tracks to initial vertex position and store them in a TObjArray
74 Double_t alpha,xlStart;
77 Int_t nEntries = (Int_t)trkTree.GetEntries();
78 if(!fTrkArray.IsEmpty()) fTrkArray.Clear();
79 fTrkArray.Expand(nEntries);
81 for(Int_t i=0; i<nEntries; i++) {
82 AliESDtrack *track = new AliESDtrack;
83 trkTree.SetBranchAddress("tracks",&track);
86 // propagate track to vtxSeed
87 alpha = track->GetAlpha();
88 xlStart = fNominalPos[0]*TMath::Cos(alpha)+fNominalPos[1]*TMath::Sin(alpha);
89 track->PropagateTo(xlStart,GetField()); // to vtxSeed
90 fTrkArray.AddLast(track);
95 //----------------------------------------------------------------------------
96 AliVertex* AliVertexerTracks::VertexForSelectedTracks(TTree *trkTree) {
98 // Return vertex from tracks in trkTree
101 // get tracks and propagate them to initial vertex position
102 Int_t nTrks = PrepareTracks(*trkTree);
103 if(nTrks < fMinTracks) {
104 printf("TooFewTracks\n");
105 Double_t vtx[3]={0,0,0};
107 fVert.SetDispersion(999);
108 fVert.SetNContributors(-5);
112 // Set initial vertex position from ESD
113 if(fAlgo==1) StrLinVertexFinderMinDist(1);
114 if(fAlgo==2) StrLinVertexFinderMinDist(0);
115 if(fAlgo==3) HelixVertexFinder();
116 if(fAlgo==4) VertexFinder(1);
117 if(fAlgo==5) VertexFinder(0);
121 //----------------------------------------------------------------------------
122 AliESDVertex* AliVertexerTracks::FindVertex(const AliESD *event) {
124 // This is a simple wrapping (by Jouri.Belikov@cern.ch) over the original
125 // code by the authors of this class.
127 Int_t nt=event->GetNumberOfTracks(), nacc=0;
129 AliESDtrack *t=event->GetTrack(nt);
130 if ((t->GetStatus()&AliESDtrack::kITSrefit)==0) continue;
131 fTrkArray.AddLast(t);
135 // get tracks and propagate them to initial vertex position
136 if(nacc < fMinTracks) {
137 printf("TooFewTracks\n");
138 Double_t vtx[3]={0,0,0};
140 fVert.SetDispersion(999);
141 fVert.SetNContributors(-5);
144 case 1: StrLinVertexFinderMinDist(1); break;
145 case 2: StrLinVertexFinderMinDist(0); break;
146 case 3: HelixVertexFinder(); break;
147 case 4: VertexFinder(1); break;
148 case 5: VertexFinder(0); break;
149 default: printf("Wrong algorithm\n"); break;
157 //----------------------------------------------------------------------------
158 AliVertex* AliVertexerTracks::VertexForSelectedTracks(TObjArray *trkArray) {
160 // Return vertex from array of tracks
163 // get tracks and propagate them to initial vertex position
164 Int_t nTrks = trkArray->GetEntriesFast();
165 if(nTrks < fMinTracks) {
166 printf("TooFewTracks\n");
167 Double_t vtx[3]={0,0,0};
169 fVert.SetDispersion(999);
170 fVert.SetNContributors(-5);
173 TTree *trkTree = new TTree("TreeT","tracks");
174 AliESDtrack *esdTrack = 0;
175 trkTree->Branch("tracks","AliESDtrack",&esdTrack);
176 for(Int_t i=0; i<nTrks; i++){
177 esdTrack = (AliESDtrack*)trkArray->At(i);
181 AliVertex *vtx = VertexForSelectedTracks(trkTree);
186 //---------------------------------------------------------------------------
187 void AliVertexerTracks::VertexFinder(Int_t optUseWeights) {
189 // Get estimate of vertex position in (x,y) from tracks DCA
193 for(Int_t i=0;i<2;i++)initPos[i]=fNominalPos[i];
194 Int_t nacc = (Int_t)fTrkArray.GetEntriesFast();
195 Double_t aver[3]={0.,0.,0.};
196 Double_t aversq[3]={0.,0.,0.};
197 Double_t sigmasq[3]={0.,0.,0.};
202 Double_t alpha,mindist;
203 Double_t field=GetField();
205 for(Int_t i=0; i<nacc; i++){
206 track1 = (AliESDtrack*)fTrkArray.At(i);
207 alpha=track1->GetAlpha();
208 mindist = TMath::Cos(alpha)*fNominalPos[0]+TMath::Sin(alpha)*fNominalPos[1];
209 AliStrLine *line1 = new AliStrLine();
210 track1->ApproximateHelixWithLine(mindist,field,line1);
212 for(Int_t j=i+1; j<nacc; j++){
213 track2 = (AliESDtrack*)fTrkArray.At(j);
214 alpha=track2->GetAlpha();
215 mindist = TMath::Cos(alpha)*fNominalPos[0]+TMath::Sin(alpha)*fNominalPos[1];
216 AliStrLine *line2 = new AliStrLine();
217 track2->ApproximateHelixWithLine(mindist,field,line2);
218 Double_t distCA=line2->GetDCA(line1);
219 if(fDCAcut<=0 || (fDCAcut>0&&distCA<fDCAcut)){
220 Double_t pnt1[3],pnt2[3],crosspoint[3];
222 if(optUseWeights<=0){
223 Int_t retcode = line2->Cross(line1,crosspoint);
226 for(Int_t jj=0;jj<3;jj++)aver[jj]+=crosspoint[jj];
227 for(Int_t jj=0;jj<3;jj++)aversq[jj]+=(crosspoint[jj]*crosspoint[jj]);
231 Int_t retcode = line1->CrossPoints(line2,pnt1,pnt2);
233 Double_t alpha, cs, sn;
234 alpha=track1->GetAlpha();
235 cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
236 Double_t sx1=sn*sn*track1->GetSigmaY2(), sy1=cs*cs*track1->GetSigmaY2();
237 alpha=track2->GetAlpha();
238 cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
239 Double_t sx2=sn*sn*track2->GetSigmaY2(), sy2=cs*cs*track2->GetSigmaY2();
240 Double_t sz1=track1->GetSigmaZ2(), sz2=track2->GetSigmaZ2();
241 Double_t wx1=sx2/(sx1+sx2), wx2=1.- wx1;
242 Double_t wy1=sy2/(sy1+sy2), wy2=1.- wy1;
243 Double_t wz1=sz2/(sz1+sz2), wz2=1.- wz1;
244 crosspoint[0]=wx1*pnt1[0] + wx2*pnt2[0];
245 crosspoint[1]=wy1*pnt1[1] + wy2*pnt2[1];
246 crosspoint[2]=wz1*pnt1[2] + wz2*pnt2[2];
249 for(Int_t jj=0;jj<3;jj++)aver[jj]+=crosspoint[jj];
250 for(Int_t jj=0;jj<3;jj++)aversq[jj]+=(crosspoint[jj]*crosspoint[jj]);
259 for(Int_t jj=0;jj<3;jj++){
260 initPos[jj] = aver[jj]/ncombi;
262 sigmasq[jj]=aversq[jj]-initPos[jj]*initPos[jj];
265 sigma=TMath::Sqrt(TMath::Abs(sigma));
268 Warning("VertexFinder","Finder did not succed");
271 fVert.SetXYZ(initPos);
272 fVert.SetDispersion(sigma);
273 fVert.SetNContributors(ncombi);
275 //---------------------------------------------------------------------------
276 void AliVertexerTracks::HelixVertexFinder() {
278 // Get estimate of vertex position in (x,y) from tracks DCA
283 for(Int_t i=0;i<2;i++)initPos[i]=fNominalPos[i];
284 Double_t field=GetField();
286 Int_t nacc = (Int_t)fTrkArray.GetEntriesFast();
288 Double_t aver[3]={0.,0.,0.};
289 Double_t averquad[3]={0.,0.,0.};
290 Double_t sigmaquad[3]={0.,0.,0.};
297 Double_t alpha, cs, sn;
298 Double_t crosspoint[3];
299 for(Int_t i=0; i<nacc; i++){
300 track1 = (AliESDtrack*)fTrkArray.At(i);
303 for(Int_t j=i+1; j<nacc; j++){
304 track2 = (AliESDtrack*)fTrkArray.At(j);
306 distCA=track2->PropagateToDCA(track1,field);
308 if(fDCAcut<=0 ||(fDCAcut>0&&distCA<fDCAcut)){
309 track1->GetExternalParameters(x,par);
310 alpha=track1->GetAlpha();
311 cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
312 Double_t x1=x*cs - par[0]*sn;
313 Double_t y1=x*sn + par[0]*cs;
315 Double_t sx1=sn*sn*track1->GetSigmaY2(), sy1=cs*cs*track1->GetSigmaY2();
316 track2->GetExternalParameters(x,par);
317 alpha=track2->GetAlpha();
318 cs=TMath::Cos(alpha); sn=TMath::Sin(alpha);
319 Double_t x2=x*cs - par[0]*sn;
320 Double_t y2=x*sn + par[0]*cs;
322 Double_t sx2=sn*sn*track2->GetSigmaY2(), sy2=cs*cs*track2->GetSigmaY2();
323 Double_t sz1=track1->GetSigmaZ2(), sz2=track2->GetSigmaZ2();
324 Double_t wx1=sx2/(sx1+sx2), wx2=1.- wx1;
325 Double_t wy1=sy2/(sy1+sy2), wy2=1.- wy1;
326 Double_t wz1=sz2/(sz1+sz2), wz2=1.- wz1;
327 crosspoint[0]=wx1*x1 + wx2*x2;
328 crosspoint[1]=wy1*y1 + wy2*y2;
329 crosspoint[2]=wz1*z1 + wz2*z2;
332 for(Int_t jj=0;jj<3;jj++)aver[jj]+=crosspoint[jj];
333 for(Int_t jj=0;jj<3;jj++)averquad[jj]+=(crosspoint[jj]*crosspoint[jj]);
339 for(Int_t jj=0;jj<3;jj++){
340 initPos[jj] = aver[jj]/ncombi;
341 averquad[jj]/=ncombi;
342 sigmaquad[jj]=averquad[jj]-initPos[jj]*initPos[jj];
343 sigma+=sigmaquad[jj];
345 sigma=TMath::Sqrt(TMath::Abs(sigma));
348 Warning("HelixVertexFinder","Finder did not succed");
351 fVert.SetXYZ(initPos);
352 fVert.SetDispersion(sigma);
353 fVert.SetNContributors(ncombi);
355 //---------------------------------------------------------------------------
356 void AliVertexerTracks::StrLinVertexFinderMinDist(Int_t optUseWeights){
358 // Calculate the point at minimum distance to prepared tracks
363 for(Int_t i=0;i<2;i++)initPos[i]=fNominalPos[i];
364 const Int_t knacc = (Int_t)fTrkArray.GetEntriesFast();
365 Double_t field=GetField();
368 Double_t (*vectP0)[3]=new Double_t [knacc][3];
369 Double_t (*vectP1)[3]=new Double_t [knacc][3];
372 Double_t dsum[3]={0,0,0};
373 for(Int_t i=0;i<3;i++)
374 for(Int_t j=0;j<3;j++)sum[i][j]=0;
375 for(Int_t i=0; i<knacc; i++){
376 track1 = (AliESDtrack*)fTrkArray.At(i);
377 Double_t alpha=track1->GetAlpha();
378 Double_t mindist = TMath::Cos(alpha)*fNominalPos[0]+TMath::Sin(alpha)*fNominalPos[1];
379 AliStrLine *line1 = new AliStrLine();
380 track1->ApproximateHelixWithLine(mindist,field,line1);
382 Double_t p0[3],cd[3];
385 Double_t p1[3]={p0[0]+cd[0],p0[1]+cd[1],p0[2]+cd[2]};
395 if(optUseWeights==0)GetStrLinDerivMatrix(p0,p1,matr,dknow);
396 if(optUseWeights==1){
398 sigmasq[0]=track1->GetSigmaY2();
399 sigmasq[1]=track1->GetSigmaY2();
400 sigmasq[2]=track1->GetSigmaZ2();
401 GetStrLinDerivMatrix(p0,p1,sigmasq,matr,dknow);
404 for(Int_t iii=0;iii<3;iii++){
405 dsum[iii]+=dknow[iii];
406 for(Int_t lj=0;lj<3;lj++) sum[iii][lj]+=matr[iii][lj];
412 Double_t det=GetDeterminant3X3(sum);
415 for(Int_t zz=0;zz<3;zz++){
416 for(Int_t ww=0;ww<3;ww++){
417 for(Int_t kk=0;kk<3;kk++) vett[ww][kk]=sum[ww][kk];
419 for(Int_t kk=0;kk<3;kk++) vett[kk][zz]=dsum[kk];
420 initPos[zz]=GetDeterminant3X3(vett)/det;
424 for(Int_t i=0; i<knacc; i++){
425 Double_t p0[3]={0,0,0},p1[3]={0,0,0};
426 for(Int_t ii=0;ii<3;ii++){
427 p0[ii]=vectP0[i][ii];
428 p1[ii]=vectP1[i][ii];
430 sigma+=GetStrLinMinDist(p0,p1,initPos);
433 sigma=TMath::Sqrt(sigma);
435 Warning("StrLinVertexFinderMinDist","Finder did not succed");
440 fVert.SetXYZ(initPos);
441 fVert.SetDispersion(sigma);
442 fVert.SetNContributors(knacc);
444 //_______________________________________________________________________
445 Double_t AliVertexerTracks::GetDeterminant3X3(Double_t matr[][3]){
447 Double_t det=matr[0][0]*matr[1][1]*matr[2][2]-matr[0][0]*matr[1][2]*matr[2][1]-matr[0][1]*matr[1][0]*matr[2][2]+matr[0][1]*matr[1][2]*matr[2][0]+matr[0][2]*matr[1][0]*matr[2][1]-matr[0][2]*matr[1][1]*matr[2][0];
450 //____________________________________________________________________________
451 void AliVertexerTracks::GetStrLinDerivMatrix(Double_t *p0,Double_t *p1,Double_t m[][3],Double_t *d){
454 Double_t x12=p0[0]-p1[0];
455 Double_t y12=p0[1]-p1[1];
456 Double_t z12=p0[2]-p1[2];
457 Double_t kk=x12*x12+y12*y12+z12*z12;
458 m[0][0]=2-2/kk*x12*x12;
459 m[0][1]=-2/kk*x12*y12;
460 m[0][2]=-2/kk*x12*z12;
461 m[1][0]=-2/kk*x12*y12;
462 m[1][1]=2-2/kk*y12*y12;
463 m[1][2]=-2/kk*y12*z12;
464 m[2][0]=-2/kk*x12*z12;
466 m[2][2]=2-2/kk*z12*z12;
467 d[0]=2*p0[0]-2/kk*p0[0]*x12*x12-2/kk*p0[2]*x12*z12-2/kk*p0[1]*x12*y12;
468 d[1]=2*p0[1]-2/kk*p0[1]*y12*y12-2/kk*p0[0]*x12*y12-2/kk*p0[2]*z12*y12;
469 d[2]=2*p0[2]-2/kk*p0[2]*z12*z12-2/kk*p0[0]*x12*z12-2/kk*p0[1]*z12*y12;
472 //____________________________________________________________________________
473 void AliVertexerTracks::GetStrLinDerivMatrix(Double_t *p0,Double_t *p1,Double_t *sigmasq,Double_t m[][3],Double_t *d){
475 Double_t x12=p1[0]-p0[0];
476 Double_t y12=p1[1]-p0[1];
477 Double_t z12=p1[2]-p0[2];
479 Double_t den= x12*x12*sigmasq[1]*sigmasq[2]+y12*y12*sigmasq[0]*sigmasq[2]+z12*z12*sigmasq[0]*sigmasq[1];
481 Double_t kk= 2*(x12*x12/sigmasq[0]+y12*y12/sigmasq[1]+z12*z12/sigmasq[2]);
484 cc[0]=-x12/sigmasq[0];
485 cc[1]=-y12/sigmasq[1];
486 cc[2]=-z12/sigmasq[2];
488 Double_t ww=(-p0[0]*x12*sigmasq[1]*sigmasq[2]-p0[1]*y12*sigmasq[0]*sigmasq[2]-p0[2]*z12*sigmasq[0]*sigmasq[1])/den;
490 Double_t ss= -p0[0]*cc[0]-p0[1]*cc[1]-p0[2]*cc[2];
493 aa[0]=x12*sigmasq[1]*sigmasq[2]/den;
494 aa[1]=y12*sigmasq[0]*sigmasq[2]/den;
495 aa[2]=z12*sigmasq[0]*sigmasq[1]/den;
497 m[0][0]=aa[0]*(aa[0]*kk+2*cc[0])+2*cc[0]*aa[0]+2/sigmasq[0];
498 m[0][1]=aa[1]*(aa[0]*kk+2*cc[0])+2*cc[1]*aa[0];
499 m[0][2]=aa[2]*(aa[0]*kk+2*cc[0])+2*cc[2]*aa[0];
501 m[1][0]=aa[0]*(aa[1]*kk+2*cc[1])+2*cc[0]*aa[1];
502 m[1][1]=aa[1]*(aa[1]*kk+2*cc[1])+2*cc[1]*aa[1]+2/sigmasq[1];
503 m[1][2]=aa[2]*(aa[1]*kk+2*cc[1])+2*cc[2]*aa[1];
505 m[2][0]=aa[0]*(aa[2]*kk+2*cc[2])+2*cc[0]*aa[2];
506 m[2][1]=aa[1]*(aa[2]*kk+2*cc[2])+2*cc[1]*aa[2];
507 m[2][2]=aa[2]*(aa[2]*kk+2*cc[2])+2*cc[2]*aa[2]+2/sigmasq[2];
509 d[0]=-ww*(aa[0]*kk+2*cc[0])-2*ss*aa[0]+2*p0[0]/sigmasq[0];
510 d[1]=-ww*(aa[1]*kk+2*cc[1])-2*ss*aa[1]+2*p0[1]/sigmasq[1];
511 d[2]=-ww*(aa[2]*kk+2*cc[2])-2*ss*aa[2]+2*p0[2]/sigmasq[2];
514 //_____________________________________________________________________________
515 Double_t AliVertexerTracks::GetStrLinMinDist(Double_t *p0,Double_t *p1,Double_t *x0){
517 Double_t x12=p0[0]-p1[0];
518 Double_t y12=p0[1]-p1[1];
519 Double_t z12=p0[2]-p1[2];
520 Double_t x10=p0[0]-x0[0];
521 Double_t y10=p0[1]-x0[1];
522 Double_t z10=p0[2]-x0[2];
523 return ((x10*x10+y10*y10+z10*z10)*(x12*x12+y12*y12+z12*z12)-(x10*x12+y10*y12+z10*z12)*(x10*x12+y10*y12+z10*z12))/(x12*x12+y12*y12+z12*z12);