1 /**************************************************************************
2 * Copyright(c) 1998-1999, 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 **************************************************************************/
17 // This class stores a tracklet (a track that lives only in a single TPC
18 // sector). Its objects can be constructed out of TPCseeds, that are
19 // holding the necessary cluster information.
24 #include "AliTPCTracklet.h"
25 #include "TObjArray.h"
26 #include "TLinearFitter.h"
27 #include "AliTPCseed.h"
28 #include "AliESDVertex.h"
29 #include "AliTracker.h"
30 #include "TTreeStream.h"
32 #include "TDecompChol.h"
37 ClassImp(AliTPCTracklet)
39 const Double_t AliTPCTracklet::kB2C=0.299792458e-3;
41 AliTPCTracklet::AliTPCTracklet()
42 : fNClusters(0),fNStoredClusters(0),fClusters(0),fSector(-1),fOuter(0),
43 fInner(0),fPrimary(0) {
45 // The default constructor. It is intended to be used for I/O only.
49 AliTPCTracklet::AliTPCTracklet(const AliTPCseed *track,Int_t sector,
50 TrackType type,Bool_t storeClusters)
51 : fNClusters(0),fNStoredClusters(0),fClusters(0),fSector(sector),fOuter(0),
52 fInner(0),fPrimary(0) {
54 // Contructor for a tracklet out of a track. Only clusters within a given
58 //TODO: only kalman works
60 for (Int_t i=0;i<160;++i) {
61 AliTPCclusterMI *c=track->GetClusterPointer(i);
62 if (c&&c->GetDetector()==sector)
67 fClusters=new AliTPCclusterMI[fNClusters];
68 for (Int_t i=0;i<160;++i) {
69 AliTPCclusterMI *c=track->GetClusterPointer(i);
70 if (c&&c->GetDetector()==sector)
71 fClusters[fNStoredClusters]=c;
78 FitKalman(track,sector);
82 FitLinear(track,sector,type);
85 FitRiemann(track,sector);
91 AliTPCTracklet::AliTPCTracklet(const TObjArray &clusters,Int_t sector,
92 TrackType type,Bool_t storeClusters) {
96 AliTPCTracklet::AliTPCTracklet(const AliTPCTracklet &t)
97 : fNClusters(t.fNClusters),fNStoredClusters(t.fNStoredClusters),fClusters(0),
98 fSector(t.fSector),fOuter(0),fInner(0),
101 // The copy constructor. You can copy tracklets!
105 fClusters=new AliTPCclusterMI[t.fNStoredClusters];
106 for (int i=0;i<t.fNStoredClusters;++i)
107 fClusters[i]=t.fClusters[i];
110 fOuter=new AliExternalTrackParam(*t.fOuter);
112 fInner=new AliExternalTrackParam(*t.fInner);
114 fPrimary=new AliExternalTrackParam(*t.fPrimary);
117 AliTPCTracklet& AliTPCTracklet::operator=(const AliTPCTracklet &t) {
119 // The assignment constructor. You can assign tracklets!
122 fNClusters=t.fNClusters;
123 fNStoredClusters=fNStoredClusters;
126 fClusters=new AliTPCclusterMI[t.fNStoredClusters];
127 for (int i=0;i<t.fNStoredClusters;++i)
128 fClusters[i]=t.fClusters[i];
137 fOuter=new AliExternalTrackParam(*t.fOuter);
148 fInner=new AliExternalTrackParam(*t.fInner);
157 *fPrimary=*t.fPrimary;
159 fPrimary=new AliExternalTrackParam(*t.fPrimary);
169 AliTPCTracklet::~AliTPCTracklet() {
171 // The destructor. Yes, you can even destruct tracklets.
179 void AliTPCTracklet::FitKalman(const AliTPCseed *track,Int_t sector) {
180 AliTPCseed *t=new AliTPCseed(*track);
181 if (!t->Rotate(TMath::DegToRad()*(sector%18*20.+10.)-t->GetAlpha())) {
185 // fit from inner to outer row
186 AliTPCseed *outerSeed=new AliTPCseed(*t);
188 for (Int_t i=0;i<160;++i) {
189 AliTPCclusterMI *c=t->GetClusterPointer(i);
190 if (c&&c->GetDetector()==sector) {
192 outerSeed->ResetCovariance(100.);
195 Double_t r[3]={c->GetX(),c->GetY(),c->GetZ()};
196 Double_t cov[3]={0.1,0.,0.1}; //TODO: correct error parametrisation
197 if (!outerSeed->PropagateTo(r[0]) ||
198 !static_cast<AliExternalTrackParam*>(outerSeed)->Update(&r[1],cov)) {
206 fOuter=new AliExternalTrackParam(*outerSeed);
208 // fit from outer to inner rows
209 AliTPCseed *innerSeed=new AliTPCseed(*t);
211 for (Int_t i=159;i>=0;--i) {
212 AliTPCclusterMI *c=t->GetClusterPointer(i);
213 if (c&&c->GetDetector()==sector) {
215 innerSeed->ResetCovariance(100.);
218 Double_t r[3]={c->GetX(),c->GetY(),c->GetZ()};
219 Double_t cov[3]={0.1,0.,0.1};
220 if (!innerSeed->PropagateTo(r[0]) ||
221 !static_cast<AliExternalTrackParam*>(innerSeed)->Update(&r[1],cov)) {
229 fInner=new AliExternalTrackParam(*innerSeed);
230 // propagate to the primary vertex
232 AliTPCseed *primarySeed=new AliTPCseed(*innerSeed);
233 Double_t pos[]={0.,0.,0.};
234 Double_t sigma[]={.1,.1,.1}; //TODO: is this correct?
235 AliESDVertex vertex(pos,sigma);
236 if (primarySeed->PropagateToVertex(&vertex))
237 fPrimary=new AliExternalTrackParam(*primarySeed);
239 // for better comparison one does not want to have alpha changed...
240 if (!fPrimary->Rotate(fInner->GetAlpha())) {
250 void AliTPCTracklet::FitLinear(const AliTPCseed *track,Int_t sector,
254 fy.StoreData(kFALSE);
255 fz.StoreData(kFALSE);
258 fy.SetFormula("1 ++ x");
259 fz.SetFormula("1 ++ x");
262 fy.SetFormula("1 ++ x ++ x*x");
263 fz.SetFormula("1 ++ x");
268 for (Int_t i=0;i<160;++i) {
269 AliTPCclusterMI *c=track->GetClusterPointer(i);
270 if (c&&c->GetDetector()==sector) {
271 Double_t x=c->GetX();
272 fy.AddPoint(&x,c->GetY());
273 fz.AddPoint(&x,c->GetZ());
274 xmax=TMath::Max(xmax,x);
275 xmin=TMath::Min(xmin,x);
280 Double_t a[3]={fy.GetParameter(0),
282 type==kQuadratic?fy.GetParameter(2):0.};
283 Double_t ca[6]={fy.GetCovarianceMatrixElement(0,0),
284 fy.GetCovarianceMatrixElement(1,0),
285 fy.GetCovarianceMatrixElement(1,1),
286 type==kQuadratic?fy.GetCovarianceMatrixElement(2,0):0.,
287 type==kQuadratic?fy.GetCovarianceMatrixElement(2,1):0.,
288 type==kQuadratic?fy.GetCovarianceMatrixElement(2,2):0.};
289 for (int i=0;i<6;++i) ca[i]*=fy.GetChisquare()/fNClusters;
290 Double_t b[2]={fz.GetParameter(0),
292 Double_t cb[3]={fz.GetCovarianceMatrixElement(0,0),
293 fz.GetCovarianceMatrixElement(1,0),
294 fz.GetCovarianceMatrixElement(1,1)};
295 for (int i=0;i<3;++i) cb[i]*=fz.GetChisquare()/fNClusters;
298 Double_t alpha=track->GetAlpha();
299 Quadratic2Helix(a,ca,b,cb,0.,p,c);
300 fPrimary=new AliExternalTrackParam(0.,alpha,p,c);
301 Quadratic2Helix(a,ca,b,cb,xmin,p,c);
302 fInner=new AliExternalTrackParam(xmin,alpha,p,c);
303 Quadratic2Helix(a,ca,b,cb,xmax,p,c);
304 fOuter=new AliExternalTrackParam(xmax,alpha,p,c);
307 void AliTPCTracklet::Quadratic2Helix(Double_t *a,Double_t *ca,
308 Double_t *b,Double_t *cb,
310 Double_t *p,Double_t *c) {
311 // y(x)=a[0]+a[1]*x+a[2]*x^2
313 // parametrises the corosponding helix at x0
315 // get the polynoms at x0
316 Double_t a0=x0*x0*a[2] + x0*a[1] + a[0];
317 Double_t a1=2.*x0*a[2] + a[1];
319 Double_t ca00=ca[0]+x0*(2.*ca[1]+x0*(ca[2]+2.*ca[3]+x0*(2.*ca[4]+x0*ca[5])));
320 Double_t ca10=ca[1]+x0*(ca[2]+2.*ca[3]+x0*(3.*ca[4]+x0*2.*ca[5]));
321 Double_t ca11=ca[2]+x0*4.*(ca[4]+x0*ca[5]);
322 Double_t ca20=ca[3]+x0*(ca[4]+x0*ca[5]);
323 Double_t ca21=ca[3]+x0*2.*ca[5];
326 Double_t b0=x0*b[1] + b[0];
328 Double_t cb00=cb[0]+x0*(2.*cb[1]+x0*cb[2]);
329 Double_t cb10=cb[1]+x0*cb[2];
332 // transform to helix parameters
333 Double_t f =1.+a1*a1;
336 Double_t fi12=TMath::Sqrt(fi);
337 Double_t fi32=fi*fi12;
339 Double_t fi52=fi2*fi12;
340 Double_t fi3 =fi2*fi;
341 Double_t fi5 =fi2*fi3;
343 Double_t xyz[3]={0.}; // TODO...
344 Double_t fc=1./(GetBz(xyz)*kB2C);
350 p[4]=2.*a2*fi32*fc; // 1/pt
355 c[3] =ca10*fi32; // snp-y0
357 c[5] =ca11*fi3; // snp-snp
359 c[7] =cb10; // tgl-z0
361 c[9] =cb11; // tgl-tgl
362 c[10]=2.*(-3.*a1*a2*ca10+f*ca20)*fi3*fc; // 1/pt-y0
364 c[12]=2.*(-3.*a1*a2*ca11+f*ca21)*fi52*fc; // 1/pt-snp
365 c[13]=0.; // 1/pt-tgl
366 c[14]=(-12.*a1*a2*(-3.*a1*a2*ca11+2.*f*ca21)+4.*f2*ca22)*fi5
371 void AliTPCTracklet::FitRiemann(const AliTPCseed *track,Int_t sector) {
373 fy.StoreData(kFALSE);
374 fy.SetFormula("hyp2");
377 for (Int_t i=0;i<160;++i) {
378 AliTPCclusterMI *c=track->GetClusterPointer(i);
379 if (c&&c->GetDetector()==sector) {
380 Double_t x=c->GetX();
381 Double_t y=c->GetY();
382 Double_t xy[2]={x,y};
384 Double_t errx=1.,erry=1.;//TODO!
385 Double_t err=TMath::Sqrt(4.*x*x*errx+4.*y*y*erry);
387 fy.AddPoint(xy,r,err);
388 xmax=TMath::Max(xmax,x);
389 xmin=TMath::Min(xmin,x);
393 Double_t a[3]={fy.GetParameter(0),
396 Double_t ca[6]={fy.GetCovarianceMatrixElement(0,0),
397 fy.GetCovarianceMatrixElement(1,0),
398 fy.GetCovarianceMatrixElement(1,1),
399 fy.GetCovarianceMatrixElement(2,0),
400 fy.GetCovarianceMatrixElement(2,1),
401 fy.GetCovarianceMatrixElement(2,2)};
404 fz.StoreData(kFALSE);
405 fz.SetFormula("hyp1");
406 Double_t R=.5*TMath::Sqrt(4.*a[0]+a[1]*a[1]+a[2]*a[2]);
410 for (Int_t i=0;i<160;++i) {
411 AliTPCclusterMI *c=track->GetClusterPointer(i);
412 if (c&&c->GetDetector()==sector) {
413 Double_t x=c->GetX();
414 Double_t y=c->GetY();
417 phi+=2.*TMath::Abs(TMath::ATan2(.5*TMath::Sqrt(dx*dx+dy*dy),R));
419 fz.AddPoint(&phi,c->GetZ(),err);
425 Double_t b[2]={fz.GetParameter(0),
427 Double_t cb[3]={fz.GetCovarianceMatrixElement(0,0),
428 fz.GetCovarianceMatrixElement(1,0),
429 fz.GetCovarianceMatrixElement(1,1)};
433 Double_t alpha=track->GetAlpha();
434 if (Riemann2Helix(a,ca,b,cb,0.,p,c))
435 fPrimary=new AliExternalTrackParam(0.,alpha,p,c);
436 if (Riemann2Helix(a,ca,b,cb,xmin,p,c))
437 fInner=new AliExternalTrackParam(xmin,alpha,p,c);
438 if (Riemann2Helix(a,ca,b,cb,xmax,p,c))
439 fOuter=new AliExternalTrackParam(xmax,alpha,p,c);
442 Bool_t AliTPCTracklet::Riemann2Helix(Double_t *a,Double_t *ca,
443 Double_t *b,Double_t *cb,
445 Double_t *p,Double_t *c) {
448 Double_t xr0=.5*a[1];
449 Double_t yr0=.5*a[2];
450 Double_t R=.5*TMath::Sqrt(4.*a[0]+a[1]*a[1]+a[2]*a[2]);
452 if (dx*dx>=R*R) return kFALSE;
453 Double_t dy=TMath::Sqrt(R*R-dx*dx); //sign!!
454 if (TMath::Abs(yr0+dy)>TMath::Abs(yr0-dy))
457 Double_t tgp=-dx/dy; //TODO: dy!=0
458 Double_t z0=b[0]+TMath::ATan(tgp)*b[1];
459 Double_t xyz[3]={x0,y0,z0};
460 Double_t fc=1./(GetBz(xyz)*kB2C);
464 p[2]=tgp/TMath::Sqrt(1.+tgp*tgp); // snp
466 p[4]=1./R*fc; // 1/pt
480 c[12]=0.; // 1/pt-snp
481 c[13]=0.; // 1/pt-tgl
482 c[14]=0.; // 1/pt-1/pt
487 TObjArray AliTPCTracklet::CreateTracklets(const AliTPCseed *track,
489 Bool_t storeClusters,
491 Int_t maxTracklets) {
492 // The tracklet factory: It creates several tracklets out of a track. They
493 // are created for sectors that fullfill the constraint of having enough
494 // clusters inside. Futhermore you can specify the maximum amount of
495 // tracklets that are to be created.
496 // The tracklets appear in a sorted fashion, beginning with those having the
499 Int_t sectors[72]={0};
500 for (Int_t i=0;i<160;++i) {
501 AliTPCclusterMI *c=track->GetClusterPointer(i);
503 ++sectors[c->GetDetector()];
506 TMath::Sort(72,sectors,indices);
508 if (maxTracklets>72) maxTracklets=72; // just to protect against "users".
509 for (Int_t i=0;i<maxTracklets&§ors[indices[i]]>=minClusters;++i) {
510 tracklets.Add(new AliTPCTracklet(track,indices[i],type,storeClusters));
515 TObjArray AliTPCTracklet::CreateTracklets(const TObjArray &clusters,
517 Bool_t storeClusters,
519 Int_t maxTracklets) {
524 Bool_t AliTPCTracklet::PropagateToMeanX(const AliTPCTracklet &t1,
525 const AliTPCTracklet &t2,
526 AliExternalTrackParam *&t1m,
527 AliExternalTrackParam *&t2m) {
528 // This function propagates two Tracklets to a common x-coordinate. This
529 // x is dermined as the one that is in the middle of the two tracklets (they
530 // are assumed to live on two distinct x-intervalls).
531 // The inner parametrisation of the outer Tracklet and the outer
532 // parametrisation of the inner Tracklet are used and propagated to this
533 // common x. This result is saved not inside the Tracklets but two new
534 // ExternalTrackParams are created (that means you might want to delete
536 // In the case that the alpha angles of the Tracklets differ both angles
537 // are tried out for this propagation.
538 // In case of any failure kFALSE is returned, no AliExternalTrackParam
539 // is created und the pointers are set to 0.
541 if (t1.GetInner() && t1.GetOuter() &&
542 t2.GetInner() && t2.GetOuter()) {
543 if (t1.GetOuter()->GetX()<t2.GetInner()->GetX()) {
544 t1m=new AliExternalTrackParam(*t1.GetOuter());
545 t2m=new AliExternalTrackParam(*t2.GetInner());
548 t1m=new AliExternalTrackParam(*t1.GetInner());
549 t2m=new AliExternalTrackParam(*t2.GetOuter());
551 Double_t mx=.5*(t1m->GetX()+t2m->GetX());
558 if (t1m->Rotate(t2m->GetAlpha())
559 && t1m->PropagateTo(mx,b1)
560 && t2m->PropagateTo(mx,b2));
562 if (t2m->Rotate(t1m->GetAlpha())
563 && t1m->PropagateTo(mx,b1)
564 && t2m->PropagateTo(mx,b2));
577 double AliTPCTracklet::GetBz(Double_t *xyz) {
578 if (AliTracker::UniformField())
579 return AliTracker::GetBz();
581 return AliTracker::GetBz(xyz);
584 void AliTPCTracklet::RandomND(Int_t ndim,const Double_t *p,const Double_t *c,
586 // This function generates a n-dimensional random variable x with mean
587 // p and covariance c.
588 // That is done using the cholesky decomposition of the covariance matrix,
589 // Begin_Latex C=U^{t} U End_Latex, with Begin_Latex U End_Latex being an
590 // upper triangular matrix. Given a vector v of iid gausian random variables
591 // with variance 1 one obtains the asked result as: Begin_Latex x=U^t v
593 // c is expected to be in a lower triangular format:
598 static TRandom3 random;
599 Double_t *c2= new Double_t[ndim*ndim];
601 for (Int_t i=0;i<ndim;++i)
602 for (Int_t j=0;j<=i;++j)
603 c2[i*ndim+j]=c2[j*ndim+i]=c[k++];
604 TMatrixDSym cm(ndim,c2);
606 TDecompChol chol(cm);
608 const TVectorD pv(ndim);
609 const_cast<TVectorD*>(&pv)->Use(ndim,const_cast<Double_t*>(p));
612 for (Int_t i=0;i<ndim;++i)
614 TMatrixD L=chol.GetU();
619 TEllipse AliTPCTracklet::ErrorEllipse(Double_t x,Double_t y,
620 Double_t sx,Double_t sy,Double_t sxy) {
622 r_{1,2}=1/2 (a+c#pm#sqrt{(a-c)^{2}+(2b)^{2}})
624 Double_t det1=1./(sx*sy-sxy*sxy);
626 Double_t b=-sxy*det1;
629 Double_t s=TMath::Sqrt(d*d+4.*b*b);
630 Double_t r1=TMath::Sqrt(.5*(a+c-s));
631 Double_t r2=TMath::Sqrt(.5*(a+c+s));
632 Double_t alpha=.5*TMath::ATan2(2.*b,d);
633 return TEllipse(x,y,r1,r2,0.,360.,alpha*TMath::RadToDeg());
636 void AliTPCTracklet::Test(const char* filename) {
639 AliTPCTracklet::Test("");
640 TFile f("AliTPCTrackletDebug.root");
641 TTree *t=f.Get("AliTPCTrackletDebug");
643 TEllipse e=AliTPCTracklet::ErrorEllipse(0.,0.,4.,1.,1.8);
646 TTreeSRedirector ds("AliTPCTrackletDebug.root");
653 for (Int_t i=0;i<10000;++i) {
656 ds<<"AliTPCTrackletDebug"
669 Double_t param[5]={0.};
670 Double_t covar[15]={1.,
675 AliExternalTrackParam track(x,alpha,param,covar);
679 for (Int_t i=0;i<points.GetNPoints();++i) {
682 Double_t param[5]={0.};
683 Double_t covar[15]={1.,
688 AliExternalTrackParam track(x,alpha,param,covar);
689 for (x=90.;x<250.;x+=1.) {
690 track.PropagateTo(x,b);