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 **************************************************************************/
18 ///////////////////////////////////////////////////////////////////////////////
20 // Implementation of the external track parameterisation class. //
22 // This parameterisation is used to exchange tracks between the detectors. //
23 // A set of functions returning the position and the momentum of tracks //
24 // in the global coordinate system as well as the track impact parameters //
26 // Origin: I.Belikov, CERN, Jouri.Belikov@cern.ch //
27 ///////////////////////////////////////////////////////////////////////////////
31 #include <TMatrixDSym.h>
32 #include <TPolyMarker3D.h>
36 #include "AliExternalTrackParam.h"
37 #include "AliVVertex.h"
40 ClassImp(AliExternalTrackParam)
42 Double32_t AliExternalTrackParam::fgMostProbablePt=kMostProbablePt;
43 Bool_t AliExternalTrackParam::fgUseLogTermMS = kFALSE;;
44 //_____________________________________________________________________________
45 AliExternalTrackParam::AliExternalTrackParam() :
51 // default constructor
53 for (Int_t i = 0; i < 5; i++) fP[i] = 0;
54 for (Int_t i = 0; i < 15; i++) fC[i] = 0;
57 //_____________________________________________________________________________
58 AliExternalTrackParam::AliExternalTrackParam(const AliExternalTrackParam &track):
66 for (Int_t i = 0; i < 5; i++) fP[i] = track.fP[i];
67 for (Int_t i = 0; i < 15; i++) fC[i] = track.fC[i];
71 //_____________________________________________________________________________
72 AliExternalTrackParam& AliExternalTrackParam::operator=(const AliExternalTrackParam &trkPar)
75 // assignment operator
79 AliVTrack::operator=(trkPar);
81 fAlpha = trkPar.fAlpha;
83 for (Int_t i = 0; i < 5; i++) fP[i] = trkPar.fP[i];
84 for (Int_t i = 0; i < 15; i++) fC[i] = trkPar.fC[i];
91 //_____________________________________________________________________________
92 AliExternalTrackParam::AliExternalTrackParam(Double_t x, Double_t alpha,
93 const Double_t param[5],
94 const Double_t covar[15]) :
100 // create external track parameters from given arguments
102 for (Int_t i = 0; i < 5; i++) fP[i] = param[i];
103 for (Int_t i = 0; i < 15; i++) fC[i] = covar[i];
107 //_____________________________________________________________________________
108 void AliExternalTrackParam::CopyFromVTrack(const AliVTrack *vTrack)
111 // Recreate TrackParams from VTrack
112 // This is not a copy contructor !
115 AliError("Source VTrack is NULL");
119 AliError("Copy of itself is requested");
123 if (vTrack->InheritsFrom(AliExternalTrackParam::Class())) {
124 AliDebug(1,"Source itself is AliExternalTrackParam, using assignment operator");
125 *this = *(AliExternalTrackParam*)vTrack;
129 AliVTrack::operator=( *vTrack );
131 Double_t xyz[3],pxpypz[3],cv[21];
133 pxpypz[0]=vTrack->Px();
134 pxpypz[1]=vTrack->Py();
135 pxpypz[2]=vTrack->Pz();
136 vTrack->GetCovarianceXYZPxPyPz(cv);
137 Short_t sign = (Short_t)vTrack->Charge();
138 Set(xyz,pxpypz,cv,sign);
141 //_____________________________________________________________________________
142 AliExternalTrackParam::AliExternalTrackParam(const AliVTrack *vTrack) :
148 // Constructor from virtual track,
149 // This is not a copy contructor !
152 if (vTrack->InheritsFrom("AliExternalTrackParam")) {
153 AliError("This is not a copy constructor. Use AliExternalTrackParam(const AliExternalTrackParam &) !");
154 AliWarning("Calling the default constructor...");
155 AliExternalTrackParam();
159 Double_t xyz[3],pxpypz[3],cv[21];
161 pxpypz[0]=vTrack->Px();
162 pxpypz[1]=vTrack->Py();
163 pxpypz[2]=vTrack->Pz();
164 vTrack->GetCovarianceXYZPxPyPz(cv);
165 Short_t sign = (Short_t)vTrack->Charge();
167 Set(xyz,pxpypz,cv,sign);
170 //_____________________________________________________________________________
171 AliExternalTrackParam::AliExternalTrackParam(Double_t xyz[3],Double_t pxpypz[3],
172 Double_t cv[21],Short_t sign) :
178 // constructor from the global parameters
181 Set(xyz,pxpypz,cv,sign);
185 //_____________________________________________________________________________
186 void AliExternalTrackParam::Set(Double_t xyz[3],Double_t pxpypz[3],
187 Double_t cv[21],Short_t sign)
190 // create external track parameters from the global parameters
191 // x,y,z,px,py,pz and their 6x6 covariance matrix
192 // A.Dainese 10.10.08
194 // Calculate alpha: the rotation angle of the corresponding local system.
196 // For global radial position inside the beam pipe, alpha is the
197 // azimuthal angle of the momentum projected on (x,y).
199 // For global radial position outside the ITS, alpha is the
200 // azimuthal angle of the centre of the TPC sector in which the point
203 const double kSafe = 1e-5;
204 Double_t radPos2 = xyz[0]*xyz[0]+xyz[1]*xyz[1];
205 Double_t radMax = 45.; // approximately ITS outer radius
206 if (radPos2 < radMax*radMax) { // inside the ITS
207 fAlpha = TMath::ATan2(pxpypz[1],pxpypz[0]);
208 } else { // outside the ITS
209 Float_t phiPos = TMath::Pi()+TMath::ATan2(-xyz[1], -xyz[0]);
211 TMath::DegToRad()*(20*((((Int_t)(phiPos*TMath::RadToDeg()))/20))+10);
214 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
215 // protection: avoid alpha being too close to 0 or +-pi/2
216 if (TMath::Abs(sn)<2*kSafe) {
217 if (fAlpha>0) fAlpha += fAlpha< TMath::Pi()/2. ? 2*kSafe : -2*kSafe;
218 else fAlpha += fAlpha>-TMath::Pi()/2. ? -2*kSafe : 2*kSafe;
219 cs=TMath::Cos(fAlpha);
220 sn=TMath::Sin(fAlpha);
222 else if (TMath::Abs(cs)<2*kSafe) {
223 if (fAlpha>0) fAlpha += fAlpha> TMath::Pi()/2. ? 2*kSafe : -2*kSafe;
224 else fAlpha += fAlpha>-TMath::Pi()/2. ? 2*kSafe : -2*kSafe;
225 cs=TMath::Cos(fAlpha);
226 sn=TMath::Sin(fAlpha);
228 // Get the vertex of origin and the momentum
229 TVector3 ver(xyz[0],xyz[1],xyz[2]);
230 TVector3 mom(pxpypz[0],pxpypz[1],pxpypz[2]);
232 // avoid momenta along axis
233 if (TMath::Abs(mom[0])<kSafe) mom[0] = TMath::Sign(kSafe*TMath::Abs(mom[1]), mom[0]);
234 if (TMath::Abs(mom[1])<kSafe) mom[1] = TMath::Sign(kSafe*TMath::Abs(mom[0]), mom[1]);
236 // Rotate to the local coordinate system
237 ver.RotateZ(-fAlpha);
238 mom.RotateZ(-fAlpha);
241 // x of the reference plane
244 Double_t charge = (Double_t)sign;
248 fP[2] = TMath::Sin(mom.Phi());
249 fP[3] = mom.Pz()/mom.Pt();
250 fP[4] = TMath::Sign(1/mom.Pt(),charge);
252 if (TMath::Abs( 1-fP[2]) < 3*kSafe) fP[2] = 1.- 3*kSafe; //Protection
253 else if (TMath::Abs(-1-fP[2]) < 3*kSafe) fP[2] =-1.+ 3*kSafe; //Protection
255 // Covariance matrix (formulas to be simplified)
256 Double_t pt=1./TMath::Abs(fP[4]);
257 // avoid alpha+phi being to close to +-pi/2 in the cov.matrix evaluation
259 Double_t r=TMath::Sqrt((1.-fp2)*(1.+fp2));
261 Double_t m00=-sn;// m10=cs;
262 Double_t m23=-pt*(sn + fp2*cs/r), m43=-pt*pt*(r*cs - fp2*sn);
263 Double_t m24= pt*(cs - fp2*sn/r), m44=-pt*pt*(r*sn + fp2*cs);
264 Double_t m35=pt, m45=-pt*pt*fP[3];
270 Double_t cv34 = TMath::Sqrt(cv[3 ]*cv[3 ]+cv[4 ]*cv[4 ]);
271 Double_t a1=cv[13]-cv[9]*(m23*m44+m43*m24)/m23/m43;
272 Double_t a2=m23*m24-m23*(m23*m44+m43*m24)/m43;
273 Double_t a3=m43*m44-m43*(m23*m44+m43*m24)/m23;
274 Double_t a4=cv[14]+2.*cv[9]; //cv[14]-2.*cv[9]*m24*m44/m23/m43;
275 Double_t a5=m24*m24-2.*m24*m44*m23/m43;
276 Double_t a6=m44*m44-2.*m24*m44*m43/m23;
278 fC[0 ] = cv[0 ]+cv[2 ];
279 fC[1 ] = TMath::Sign(cv34,cv[3 ]/m00);
281 fC[3 ] = (cv[10]*m43-cv[6]*m44)/(m24*m43-m23*m44)/m00;
282 fC[10] = (cv[6]/m00-fC[3 ]*m23)/m43;
283 fC[6 ] = (cv[15]/m00-fC[10]*m45)/m35;
284 fC[4 ] = (cv[12]*m43-cv[8]*m44)/(m24*m43-m23*m44);
285 fC[11] = (cv[8]-fC[4]*m23)/m43;
286 fC[7 ] = cv[17]/m35-fC[11]*m45/m35;
287 fC[5 ] = TMath::Abs((a4*a3-a6*a1)/(a5*a3-a6*a2));
288 fC[14] = TMath::Abs((a1-a2*fC[5])/a3);
289 fC[12] = (cv[9]-fC[5]*m23*m23-fC[14]*m43*m43)/m23/m43;
290 Double_t b1=cv[18]-fC[12]*m23*m45-fC[14]*m43*m45;
293 Double_t b4=cv[19]-fC[12]*m24*m45-fC[14]*m44*m45;
296 fC[8 ] = (b4-b6*b1/b3)/(b5-b6*b2/b3);
297 fC[13] = b1/b3-b2*fC[8]/b3;
298 fC[9 ] = TMath::Abs((cv[20]-fC[14]*(m45*m45)-fC[13]*2.*m35*m45)/(m35*m35));
306 //_____________________________________________________________________________
307 void AliExternalTrackParam::Set(Double_t xyz[3],Double_t pxpypz[3],
308 Double_t cv[21],Short_t sign)
311 // create external track parameters from the global parameters
312 // x,y,z,px,py,pz and their 6x6 covariance matrix
313 // A.Dainese 10.10.08
315 // Calculate alpha: the rotation angle of the corresponding local system.
317 // For global radial position inside the beam pipe, alpha is the
318 // azimuthal angle of the momentum projected on (x,y).
320 // For global radial position outside the ITS, alpha is the
321 // azimuthal angle of the centre of the TPC sector in which the point
324 const double kSafe = 1e-5;
325 Double_t radPos2 = xyz[0]*xyz[0]+xyz[1]*xyz[1];
326 Double_t radMax = 45.; // approximately ITS outer radius
327 if (radPos2 < radMax*radMax) { // inside the ITS
328 fAlpha = TMath::ATan2(pxpypz[1],pxpypz[0]);
329 } else { // outside the ITS
330 Float_t phiPos = TMath::Pi()+TMath::ATan2(-xyz[1], -xyz[0]);
332 TMath::DegToRad()*(20*((((Int_t)(phiPos*TMath::RadToDeg()))/20))+10);
335 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
336 // protection: avoid alpha being too close to 0 or +-pi/2
337 if (TMath::Abs(sn)<2*kSafe) {
338 if (fAlpha>0) fAlpha += fAlpha< TMath::Pi()/2. ? 2*kSafe : -2*kSafe;
339 else fAlpha += fAlpha>-TMath::Pi()/2. ? -2*kSafe : 2*kSafe;
340 cs=TMath::Cos(fAlpha);
341 sn=TMath::Sin(fAlpha);
343 else if (TMath::Abs(cs)<2*kSafe) {
344 if (fAlpha>0) fAlpha += fAlpha> TMath::Pi()/2. ? 2*kSafe : -2*kSafe;
345 else fAlpha += fAlpha>-TMath::Pi()/2. ? 2*kSafe : -2*kSafe;
346 cs=TMath::Cos(fAlpha);
347 sn=TMath::Sin(fAlpha);
349 // Get the vertex of origin and the momentum
350 TVector3 ver(xyz[0],xyz[1],xyz[2]);
351 TVector3 mom(pxpypz[0],pxpypz[1],pxpypz[2]);
353 // Rotate to the local coordinate system
354 ver.RotateZ(-fAlpha);
355 mom.RotateZ(-fAlpha);
358 // x of the reference plane
361 Double_t charge = (Double_t)sign;
365 fP[2] = TMath::Sin(mom.Phi());
366 fP[3] = mom.Pz()/mom.Pt();
367 fP[4] = TMath::Sign(1/mom.Pt(),charge);
369 if (TMath::Abs( 1-fP[2]) < kSafe) fP[2] = 1.- kSafe; //Protection
370 else if (TMath::Abs(-1-fP[2]) < kSafe) fP[2] =-1.+ kSafe; //Protection
372 // Covariance matrix (formulas to be simplified)
373 Double_t pt=1./TMath::Abs(fP[4]);
374 Double_t r=TMath::Sqrt((1.-fP[2])*(1.+fP[2]));
376 Double_t cv34 = TMath::Sqrt(cv[3 ]*cv[3 ]+cv[4 ]*cv[4 ]);
379 double sgcheck = r*sn + fP[2]*cs;
380 if (TMath::Abs(sgcheck)>=1-kSafe) { // special case: lab phi is +-pi/2
382 sgcheck = TMath::Sign(1.0,sgcheck);
384 else if (TMath::Abs(sgcheck)<kSafe) {
385 sgcheck = TMath::Sign(1.0,cs);
386 special = 2; // special case: lab phi is 0
389 fC[0 ] = cv[0 ]+cv[2 ];
390 fC[1 ] = TMath::Sign(cv34,-cv[3 ]*sn);
395 double pti2 = pti*pti;
398 fC[4 ] = -sgcheck*cv[8]*r*pti;
399 fC[5 ] = TMath::Abs(cv[9]*r*r*pti2);
400 fC[6 ] = (cv[10]*fP[3]-sgcheck*cv[15])*pti/r;
401 fC[7 ] = (cv[17]-sgcheck*cv[12]*fP[3])*pti;
402 fC[8 ] = (-sgcheck*cv[18]+cv[13]*fP[3])*r*pti2;
403 fC[9 ] = TMath::Abs( cv[20]-2*sgcheck*cv[19]*fP[3]+cv[14]*fP[3]*fP[3])*pti2;
404 fC[10] = cv[10]*pti2/r*q;
405 fC[11] = -sgcheck*cv[12]*pti2*q;
406 fC[12] = cv[13]*r*pti*pti2*q;
407 fC[13] = (-sgcheck*cv[19]+cv[14]*fP[3])*r*pti2*pti;
408 fC[14] = TMath::Abs(cv[14]*pti2*pti2);
409 } else if (special==2) {
411 double pti2 = pti*pti;
413 fC[3 ] = -cv[10]*pti*cs/sn;
414 fC[4 ] = cv[12]*cs*pti;
415 fC[5 ] = TMath::Abs(cv[14]*cs*cs*pti2);
416 fC[6 ] = (sgcheck*cv[6]*fP[3]-cv[15])*pti/sn;
417 fC[7 ] = (cv[17]-sgcheck*cv[8]*fP[3])*pti;
418 fC[8 ] = (cv[19]-sgcheck*cv[13]*fP[3])*cs*pti2;
419 fC[9 ] = TMath::Abs( cv[20]-2*sgcheck*cv[18]*fP[3]+cv[9]*fP[3]*fP[3])*pti2;
420 fC[10] = sgcheck*cv[6]*pti2/sn*q;
421 fC[11] = -sgcheck*cv[8]*pti2*q;
422 fC[12] = -sgcheck*cv[13]*cs*pti*pti2*q;
423 fC[13] = (-sgcheck*cv[18]+cv[9]*fP[3])*pti2*pti*q;
424 fC[14] = TMath::Abs(cv[9]*pti2*pti2);
427 Double_t m00=-sn;// m10=cs;
428 Double_t m23=-pt*(sn + fP[2]*cs/r), m43=-pt*pt*(r*cs - fP[2]*sn);
429 Double_t m24= pt*(cs - fP[2]*sn/r), m44=-pt*pt*(r*sn + fP[2]*cs);
430 Double_t m35=pt, m45=-pt*pt*fP[3];
436 Double_t a1=cv[13]-cv[9]*(m23*m44+m43*m24)/m23/m43;
437 Double_t a2=m23*m24-m23*(m23*m44+m43*m24)/m43;
438 Double_t a3=m43*m44-m43*(m23*m44+m43*m24)/m23;
439 Double_t a4=cv[14]+2.*cv[9]; //cv[14]-2.*cv[9]*m24*m44/m23/m43;
440 Double_t a5=m24*m24-2.*m24*m44*m23/m43;
441 Double_t a6=m44*m44-2.*m24*m44*m43/m23;
443 fC[3 ] = (cv[10]*m43-cv[6]*m44)/(m24*m43-m23*m44)/m00;
444 fC[10] = (cv[6]/m00-fC[3 ]*m23)/m43;
445 fC[6 ] = (cv[15]/m00-fC[10]*m45)/m35;
446 fC[4 ] = (cv[12]*m43-cv[8]*m44)/(m24*m43-m23*m44);
447 fC[11] = (cv[8]-fC[4]*m23)/m43;
448 fC[7 ] = cv[17]/m35-fC[11]*m45/m35;
449 fC[5 ] = TMath::Abs((a4*a3-a6*a1)/(a5*a3-a6*a2));
450 fC[14] = TMath::Abs((a1-a2*fC[5])/a3);
451 fC[12] = (cv[9]-fC[5]*m23*m23-fC[14]*m43*m43)/m23/m43;
452 Double_t b1=cv[18]-fC[12]*m23*m45-fC[14]*m43*m45;
455 Double_t b4=cv[19]-fC[12]*m24*m45-fC[14]*m44*m45;
458 fC[8 ] = (b4-b6*b1/b3)/(b5-b6*b2/b3);
459 fC[13] = b1/b3-b2*fC[8]/b3;
460 fC[9 ] = TMath::Abs((cv[20]-fC[14]*(m45*m45)-fC[13]*2.*m35*m45)/(m35*m35));
467 //_____________________________________________________________________________
468 void AliExternalTrackParam::Reset() {
470 // Resets all the parameters to 0
473 for (Int_t i = 0; i < 5; i++) fP[i] = 0;
474 for (Int_t i = 0; i < 15; i++) fC[i] = 0;
477 //_____________________________________________________________________________
478 void AliExternalTrackParam::AddCovariance(const Double_t c[15]) {
480 // Add "something" to the track covarince matrix.
481 // May be needed to account for unknown mis-calibration/mis-alignment
484 fC[1] +=c[1]; fC[2] +=c[2];
485 fC[3] +=c[3]; fC[4] +=c[4]; fC[5] +=c[5];
486 fC[6] +=c[6]; fC[7] +=c[7]; fC[8] +=c[8]; fC[9] +=c[9];
487 fC[10]+=c[10]; fC[11]+=c[11]; fC[12]+=c[12]; fC[13]+=c[13]; fC[14]+=c[14];
492 Double_t AliExternalTrackParam::GetP() const {
493 //---------------------------------------------------------------------
494 // This function returns the track momentum
495 // Results for (nearly) straight tracks are meaningless !
496 //---------------------------------------------------------------------
497 if (TMath::Abs(fP[4])<=kAlmost0) return kVeryBig;
498 return TMath::Sqrt(1.+ fP[3]*fP[3])/TMath::Abs(fP[4]);
501 Double_t AliExternalTrackParam::Get1P() const {
502 //---------------------------------------------------------------------
503 // This function returns the 1/(track momentum)
504 //---------------------------------------------------------------------
505 return TMath::Abs(fP[4])/TMath::Sqrt(1.+ fP[3]*fP[3]);
508 //_______________________________________________________________________
509 Double_t AliExternalTrackParam::GetD(Double_t x,Double_t y,Double_t b) const {
510 //------------------------------------------------------------------
511 // This function calculates the transverse impact parameter
512 // with respect to a point with global coordinates (x,y)
513 // in the magnetic field "b" (kG)
514 //------------------------------------------------------------------
515 if (TMath::Abs(b) < kAlmost0Field) return GetLinearD(x,y);
516 Double_t rp4=GetC(b);
518 Double_t xt=fX, yt=fP[0];
520 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
521 Double_t a = x*cs + y*sn;
522 y = -x*sn + y*cs; x=a;
525 sn=rp4*xt - fP[2]; cs=rp4*yt + TMath::Sqrt((1.- fP[2])*(1.+fP[2]));
526 a=2*(xt*fP[2] - yt*TMath::Sqrt((1.-fP[2])*(1.+fP[2])))-rp4*(xt*xt + yt*yt);
527 return -a/(1 + TMath::Sqrt(sn*sn + cs*cs));
530 //_______________________________________________________________________
531 void AliExternalTrackParam::
532 GetDZ(Double_t x, Double_t y, Double_t z, Double_t b, Float_t dz[2]) const {
533 //------------------------------------------------------------------
534 // This function calculates the transverse and longitudinal impact parameters
535 // with respect to a point with global coordinates (x,y)
536 // in the magnetic field "b" (kG)
537 //------------------------------------------------------------------
538 Double_t f1 = fP[2], r1 = TMath::Sqrt((1.-f1)*(1.+f1));
539 Double_t xt=fX, yt=fP[0];
540 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
541 Double_t a = x*cs + y*sn;
542 y = -x*sn + y*cs; x=a;
545 Double_t rp4=GetC(b);
546 if ((TMath::Abs(b) < kAlmost0Field) || (TMath::Abs(rp4) < kAlmost0)) {
547 dz[0] = -(xt*f1 - yt*r1);
548 dz[1] = fP[1] + (dz[0]*f1 - xt)/r1*fP[3] - z;
552 sn=rp4*xt - f1; cs=rp4*yt + r1;
553 a=2*(xt*f1 - yt*r1)-rp4*(xt*xt + yt*yt);
554 Double_t rr=TMath::Sqrt(sn*sn + cs*cs);
556 Double_t f2 = -sn/rr, r2 = TMath::Sqrt((1.-f2)*(1.+f2));
557 dz[1] = fP[1] + fP[3]/rp4*TMath::ASin(f2*r1 - f1*r2) - z;
560 //_______________________________________________________________________
561 Double_t AliExternalTrackParam::GetLinearD(Double_t xv,Double_t yv) const {
562 //------------------------------------------------------------------
563 // This function calculates the transverse impact parameter
564 // with respect to a point with global coordinates (xv,yv)
565 // neglecting the track curvature.
566 //------------------------------------------------------------------
567 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
568 Double_t x= xv*cs + yv*sn;
569 Double_t y=-xv*sn + yv*cs;
571 Double_t d = (fX-x)*fP[2] - (fP[0]-y)*TMath::Sqrt((1.-fP[2])*(1.+fP[2]));
576 Bool_t AliExternalTrackParam::CorrectForMeanMaterialdEdx
577 (Double_t xOverX0, Double_t xTimesRho, Double_t mass,
580 //------------------------------------------------------------------
581 // This function corrects the track parameters for the crossed material.
582 // "xOverX0" - X/X0, the thickness in units of the radiation length.
583 // "xTimesRho" - is the product length*density (g/cm^2).
584 // It should be passed as negative when propagating tracks
585 // from the intreaction point to the outside of the central barrel.
586 // "mass" - the mass of this particle (GeV/c^2). Negative mass means charge=2 particle
587 // "dEdx" - mean enery loss (GeV/(g/cm^2)
588 // "anglecorr" - switch for the angular correction
589 //------------------------------------------------------------------
594 Double_t &fC22=fC[5];
595 Double_t &fC33=fC[9];
596 Double_t &fC43=fC[13];
597 Double_t &fC44=fC[14];
599 //Apply angle correction, if requested
601 Double_t angle=TMath::Sqrt((1.+ fP3*fP3)/((1-fP2)*(1.+fP2)));
607 if (mass<0) p += p; // q=2 particle
609 Double_t beta2=p2/(p2 + mass*mass);
611 //Calculating the multiple scattering corrections******************
617 //Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*TMath::Abs(d)*9.36*2.33;
618 Double_t theta2=0.0136*0.0136/(beta2*p2)*TMath::Abs(xOverX0);
619 if (GetUseLogTermMS()) {
620 double lt = 1+0.038*TMath::Log(TMath::Abs(xOverX0));
621 if (lt>0) theta2 *= lt*lt;
623 if (mass<0) theta2 *= 4; // q=2 particle
624 if(theta2>TMath::Pi()*TMath::Pi()) return kFALSE;
625 cC22 = theta2*((1.-fP2)*(1.+fP2))*(1. + fP3*fP3);
626 cC33 = theta2*(1. + fP3*fP3)*(1. + fP3*fP3);
627 cC43 = theta2*fP3*fP4*(1. + fP3*fP3);
628 cC44 = theta2*fP3*fP4*fP3*fP4;
631 //Calculating the energy loss corrections************************
633 if ((xTimesRho != 0.) && (beta2 < 1.)) {
634 Double_t dE=dEdx*xTimesRho;
635 Double_t e=TMath::Sqrt(p2 + mass*mass);
636 if ( TMath::Abs(dE) > 0.3*e ) return kFALSE; //30% energy loss is too much!
637 if ( (1.+ dE/p2*(dE + 2*e)) < 0. ) return kFALSE;
638 cP4 = 1./TMath::Sqrt(1.+ dE/p2*(dE + 2*e)); //A precise formula by Ruben !
639 if (TMath::Abs(fP4*cP4)>100.) return kFALSE; //Do not track below 10 MeV/c
642 // Approximate energy loss fluctuation (M.Ivanov)
643 const Double_t knst=0.07; // To be tuned.
644 Double_t sigmadE=knst*TMath::Sqrt(TMath::Abs(dE));
645 cC44 += ((sigmadE*e/p2*fP4)*(sigmadE*e/p2*fP4));
649 //Applying the corrections*****************************
661 Bool_t AliExternalTrackParam::CorrectForMeanMaterial
662 (Double_t xOverX0, Double_t xTimesRho, Double_t mass,
664 Double_t (*Bethe)(Double_t)) {
665 //------------------------------------------------------------------
666 // This function corrects the track parameters for the crossed material.
667 // "xOverX0" - X/X0, the thickness in units of the radiation length.
668 // "xTimesRho" - is the product length*density (g/cm^2).
669 // It should be passed as negative when propagating tracks
670 // from the intreaction point to the outside of the central barrel.
671 // "mass" - the mass of this particle (GeV/c^2). mass<0 means charge=2
672 // "anglecorr" - switch for the angular correction
673 // "Bethe" - function calculating the energy loss (GeV/(g/cm^2))
674 //------------------------------------------------------------------
676 Double_t bg=GetP()/mass;
679 AliDebug(2,Form("Mass %f corresponds to unknown PID particle",mass));
684 Double_t dEdx=Bethe(bg);
685 if (mass<0) dEdx *= 4;
687 return CorrectForMeanMaterialdEdx(xOverX0,xTimesRho,mass,dEdx,anglecorr);
690 Bool_t AliExternalTrackParam::CorrectForMeanMaterialZA
691 (Double_t xOverX0, Double_t xTimesRho, Double_t mass,
698 //------------------------------------------------------------------
699 // This function corrects the track parameters for the crossed material
700 // using the full Geant-like Bethe-Bloch formula parameterization
701 // "xOverX0" - X/X0, the thickness in units of the radiation length.
702 // "xTimesRho" - is the product length*density (g/cm^2).
703 // It should be passed as negative when propagating tracks
704 // from the intreaction point to the outside of the central barrel.
705 // "mass" - the mass of this particle (GeV/c^2). mass<0 means charge=2 particle
706 // "density" - mean density (g/cm^3)
707 // "zOverA" - mean Z/A
708 // "exEnergy" - mean exitation energy (GeV)
709 // "jp1" - density effect first junction point
710 // "jp2" - density effect second junction point
711 // "anglecorr" - switch for the angular correction
713 // The default values of the parameters are for silicon
715 //------------------------------------------------------------------
717 Double_t bg=GetP()/mass;
720 AliDebug(2,Form("Mass %f corresponds to unknown PID particle",mass));
725 Double_t dEdx=BetheBlochGeant(bg,density,jp1,jp2,exEnergy,zOverA);
727 if (mass<0) dEdx *= 4;
728 return CorrectForMeanMaterialdEdx(xOverX0,xTimesRho,mass,dEdx,anglecorr);
733 Bool_t AliExternalTrackParam::CorrectForMaterial
734 (Double_t d, Double_t x0, Double_t mass, Double_t (*Bethe)(Double_t)) {
735 //------------------------------------------------------------------
736 // Deprecated function !
737 // Better use CorrectForMeanMaterial instead of it.
739 // This function corrects the track parameters for the crossed material
740 // "d" - the thickness (fraction of the radiation length)
741 // It should be passed as negative when propagating tracks
742 // from the intreaction point to the outside of the central barrel.
743 // "x0" - the radiation length (g/cm^2)
744 // "mass" - the mass of this particle (GeV/c^2)
745 //------------------------------------------------------------------
747 return CorrectForMeanMaterial(d,x0*d,mass,kTRUE,Bethe);
751 Double_t AliExternalTrackParam::BetheBlochAleph(Double_t bg,
758 // This is the empirical ALEPH parameterization of the Bethe-Bloch formula.
759 // It is normalized to 1 at the minimum.
763 // The default values for the kp* parameters are for ALICE TPC.
764 // The returned value is in MIP units
767 Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
769 Double_t aa = TMath::Power(beta,kp4);
770 Double_t bb = TMath::Power(1./bg,kp5);
772 bb=TMath::Log(kp3+bb);
774 return (kp2-aa-bb)*kp1/aa;
777 Double_t AliExternalTrackParam::BetheBlochGeant(Double_t bg,
784 // This is the parameterization of the Bethe-Bloch formula inspired by Geant.
787 // kp0 - density [g/cm^3]
788 // kp1 - density effect first junction point
789 // kp2 - density effect second junction point
790 // kp3 - mean excitation energy [GeV]
793 // The default values for the kp* parameters are for silicon.
794 // The returned value is in [GeV/(g/cm^2)].
797 const Double_t mK = 0.307075e-3; // [GeV*cm^2/g]
798 const Double_t me = 0.511e-3; // [GeV/c^2]
799 const Double_t rho = kp0;
800 const Double_t x0 = kp1*2.303;
801 const Double_t x1 = kp2*2.303;
802 const Double_t mI = kp3;
803 const Double_t mZA = kp4;
804 const Double_t bg2 = bg*bg;
805 const Double_t maxT= 2*me*bg2; // neglecting the electron mass
809 const Double_t x=TMath::Log(bg);
810 const Double_t lhwI=TMath::Log(28.816*1e-9*TMath::Sqrt(rho*mZA)/mI);
814 const Double_t r=(x1-x)/(x1-x0);
815 d2 = lhwI + x - 0.5 + (0.5 - lhwI - x0)*r*r*r;
818 return mK*mZA*(1+bg2)/bg2*
819 (0.5*TMath::Log(2*me*bg2*maxT/(mI*mI)) - bg2/(1+bg2) - d2);
822 Double_t AliExternalTrackParam::BetheBlochSolid(Double_t bg) {
823 //------------------------------------------------------------------
824 // This is an approximation of the Bethe-Bloch formula,
825 // reasonable for solid materials.
826 // All the parameters are, in fact, for Si.
827 // The returned value is in [GeV/(g/cm^2)]
828 //------------------------------------------------------------------
830 return BetheBlochGeant(bg);
833 Double_t AliExternalTrackParam::BetheBlochGas(Double_t bg) {
834 //------------------------------------------------------------------
835 // This is an approximation of the Bethe-Bloch formula,
836 // reasonable for gas materials.
837 // All the parameters are, in fact, for Ne.
838 // The returned value is in [GeV/(g/cm^2)]
839 //------------------------------------------------------------------
841 const Double_t rho = 0.9e-3;
842 const Double_t x0 = 2.;
843 const Double_t x1 = 4.;
844 const Double_t mI = 140.e-9;
845 const Double_t mZA = 0.49555;
847 return BetheBlochGeant(bg,rho,x0,x1,mI,mZA);
850 Bool_t AliExternalTrackParam::Rotate(Double_t alpha) {
851 //------------------------------------------------------------------
852 // Transform this track to the local coord. system rotated
853 // by angle "alpha" (rad) with respect to the global coord. system.
854 //------------------------------------------------------------------
855 if (TMath::Abs(fP[2]) >= kAlmost1) {
856 AliError(Form("Precondition is not satisfied: |sin(phi)|>1 ! %f",fP[2]));
860 if (alpha < -TMath::Pi()) alpha += 2*TMath::Pi();
861 else if (alpha >= TMath::Pi()) alpha -= 2*TMath::Pi();
865 Double_t &fC00=fC[0];
866 Double_t &fC10=fC[1];
867 Double_t &fC20=fC[3];
868 Double_t &fC21=fC[4];
869 Double_t &fC22=fC[5];
870 Double_t &fC30=fC[6];
871 Double_t &fC32=fC[8];
872 Double_t &fC40=fC[10];
873 Double_t &fC42=fC[12];
876 Double_t ca=TMath::Cos(alpha-fAlpha), sa=TMath::Sin(alpha-fAlpha);
877 Double_t sf=fP2, cf=TMath::Sqrt((1.- fP2)*(1.+fP2)); // Improve precision
878 // RS: check if rotation does no invalidate track model (cos(local_phi)>=0, i.e. particle
879 // direction in local frame is along the X axis
880 if ((cf*ca+sf*sa)<0) {
881 AliDebug(1,Form("Rotation failed: local cos(phi) would become %.2f",cf*ca+sf*sa));
885 Double_t tmp=sf*ca - cf*sa;
887 if (TMath::Abs(tmp) >= kAlmost1) {
888 if (TMath::Abs(tmp) > 1.+ Double_t(FLT_EPSILON))
889 AliWarning(Form("Rotation failed ! %.10e",tmp));
897 if (TMath::Abs(cf)<kAlmost0) {
898 AliError(Form("Too small cosine value %f",cf));
902 Double_t rr=(ca+sf/cf*sa);
919 Bool_t AliExternalTrackParam::Invert() {
920 //------------------------------------------------------------------
921 // Transform this track to the local coord. system rotated by 180 deg.
922 //------------------------------------------------------------------
924 fAlpha += TMath::Pi();
925 while (fAlpha < -TMath::Pi()) fAlpha += 2*TMath::Pi();
926 while (fAlpha >= TMath::Pi()) fAlpha -= 2*TMath::Pi();
933 fC[1] = -fC[1]; // since the fP1 and fP2 are not inverted, their covariances with others change sign
943 Bool_t AliExternalTrackParam::PropagateTo(Double_t xk, Double_t b) {
944 //----------------------------------------------------------------
945 // Propagate this track to the plane X=xk (cm) in the field "b" (kG)
946 //----------------------------------------------------------------
948 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
950 Double_t crv=GetC(b);
951 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
953 Double_t x2r = crv*dx;
954 Double_t f1=fP[2], f2=f1 + x2r;
955 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
956 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
957 if (TMath::Abs(fP[4])< kAlmost0) return kFALSE;
959 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
962 &fC10=fC[1], &fC11=fC[2],
963 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
964 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
965 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
967 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
968 if (TMath::Abs(r1)<kAlmost0) return kFALSE;
969 if (TMath::Abs(r2)<kAlmost0) return kFALSE;
972 double dy2dx = (f1+f2)/(r1+r2);
975 if (TMath::Abs(x2r)<0.05) fP1 += dx*(r2 + f2*dy2dx)*fP3; // Many thanks to P.Hristov !
977 // for small dx/R the linear apporximation of the arc by the segment is OK,
978 // but at large dx/R the error is very large and leads to incorrect Z propagation
979 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
980 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
981 // double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
982 // double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
983 // fP1 += rot/crv*fP3;
985 fP1 += fP3/crv*TMath::ASin(r1*f2 - r2*f1); // more economic version from Yura.
990 Double_t f02= dx/(r1*r1*r1); Double_t cc=crv/fP4;
991 Double_t f04=0.5*dx*dx/(r1*r1*r1); f04*=cc;
992 Double_t f12= dx*fP3*f1/(r1*r1*r1);
993 Double_t f14=0.5*dx*dx*fP3*f1/(r1*r1*r1); f14*=cc;
995 Double_t f24= dx; f24*=cc;
997 Double_t rinv = 1./r1;
998 Double_t r3inv = rinv*rinv*rinv;
999 Double_t f24= x2r/fP4;
1000 Double_t f02= dx*r3inv;
1001 Double_t f04=0.5*f24*f02;
1002 Double_t f12= f02*fP3*f1;
1003 Double_t f14=0.5*f24*f02*fP3*f1;
1004 Double_t f13= dx*rinv;
1007 Double_t b00=f02*fC20 + f04*fC40, b01=f12*fC20 + f14*fC40 + f13*fC30;
1008 Double_t b02=f24*fC40;
1009 Double_t b10=f02*fC21 + f04*fC41, b11=f12*fC21 + f14*fC41 + f13*fC31;
1010 Double_t b12=f24*fC41;
1011 Double_t b20=f02*fC22 + f04*fC42, b21=f12*fC22 + f14*fC42 + f13*fC32;
1012 Double_t b22=f24*fC42;
1013 Double_t b40=f02*fC42 + f04*fC44, b41=f12*fC42 + f14*fC44 + f13*fC43;
1014 Double_t b42=f24*fC44;
1015 Double_t b30=f02*fC32 + f04*fC43, b31=f12*fC32 + f14*fC43 + f13*fC33;
1016 Double_t b32=f24*fC43;
1019 Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a02=f02*b22+f04*b42;
1020 Double_t a11=f12*b21+f14*b41+f13*b31,a12=f12*b22+f14*b42+f13*b32;
1021 Double_t a22=f24*b42;
1023 //F*C*Ft = C + (b + bt + a)
1024 fC00 += b00 + b00 + a00;
1025 fC10 += b10 + b01 + a01;
1026 fC20 += b20 + b02 + a02;
1029 fC11 += b11 + b11 + a11;
1030 fC21 += b21 + b12 + a12;
1033 fC22 += b22 + b22 + a22;
1042 Bool_t AliExternalTrackParam::PropagateParamOnlyTo(Double_t xk, Double_t b) {
1043 //----------------------------------------------------------------
1044 // Propagate this track to the plane X=xk (cm) in the field "b" (kG)
1045 // Only parameters are propagated, not the matrix. To be used for small
1046 // distances only (<mm, i.e. misalignment)
1047 //----------------------------------------------------------------
1049 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
1051 Double_t crv=GetC(b);
1052 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1054 Double_t x2r = crv*dx;
1055 Double_t f1=fP[2], f2=f1 + x2r;
1056 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1057 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1058 if (TMath::Abs(fP[4])< kAlmost0) return kFALSE;
1060 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
1061 if (TMath::Abs(r1)<kAlmost0) return kFALSE;
1062 if (TMath::Abs(r2)<kAlmost0) return kFALSE;
1065 double dy2dx = (f1+f2)/(r1+r2);
1067 fP[1] += dx*(r2 + f2*dy2dx)*fP[3]; // Many thanks to P.Hristov !
1074 AliExternalTrackParam::Propagate(Double_t alpha, Double_t x, Double_t b) {
1075 //------------------------------------------------------------------
1076 // Transform this track to the local coord. system rotated
1077 // by angle "alpha" (rad) with respect to the global coord. system,
1078 // and propagate this track to the plane X=xk (cm) in the field "b" (kG)
1079 //------------------------------------------------------------------
1081 //Save the parameters
1084 Double_t ps[5], cs[15];
1085 for (Int_t i=0; i<5; i++) ps[i]=fP[i];
1086 for (Int_t i=0; i<15; i++) cs[i]=fC[i];
1089 if (PropagateTo(x,b)) return kTRUE;
1091 //Restore the parameters, if the operation failed
1094 for (Int_t i=0; i<5; i++) fP[i]=ps[i];
1095 for (Int_t i=0; i<15; i++) fC[i]=cs[i];
1099 Bool_t AliExternalTrackParam::PropagateBxByBz
1100 (Double_t alpha, Double_t x, Double_t b[3]) {
1101 //------------------------------------------------------------------
1102 // Transform this track to the local coord. system rotated
1103 // by angle "alpha" (rad) with respect to the global coord. system,
1104 // and propagate this track to the plane X=xk (cm),
1105 // taking into account all three components of the B field, "b[3]" (kG)
1106 //------------------------------------------------------------------
1108 //Save the parameters
1111 Double_t ps[5], cs[15];
1112 for (Int_t i=0; i<5; i++) ps[i]=fP[i];
1113 for (Int_t i=0; i<15; i++) cs[i]=fC[i];
1116 if (PropagateToBxByBz(x,b)) return kTRUE;
1118 //Restore the parameters, if the operation failed
1121 for (Int_t i=0; i<5; i++) fP[i]=ps[i];
1122 for (Int_t i=0; i<15; i++) fC[i]=cs[i];
1127 void AliExternalTrackParam::Propagate(Double_t len, Double_t x[3],
1128 Double_t p[3], Double_t bz) const {
1129 //+++++++++++++++++++++++++++++++++++++++++
1130 // Origin: K. Shileev (Kirill.Shileev@cern.ch)
1131 // Extrapolate track along simple helix in magnetic field
1132 // Arguments: len -distance alogn helix, [cm]
1133 // bz - mag field, [kGaus]
1134 // Returns: x and p contain extrapolated positon and momentum
1135 // The momentum returned for straight-line tracks is meaningless !
1136 //+++++++++++++++++++++++++++++++++++++++++
1139 if (OneOverPt() < kAlmost0 || TMath::Abs(bz) < kAlmost0Field || GetC(bz) < kAlmost0){ //straight-line tracks
1140 Double_t unit[3]; GetDirection(unit);
1145 p[0]=unit[0]/kAlmost0;
1146 p[1]=unit[1]/kAlmost0;
1147 p[2]=unit[2]/kAlmost0;
1151 Double_t a = -kB2C*bz*GetSign();
1152 Double_t rho = a/pp;
1153 x[0] += p[0]*TMath::Sin(rho*len)/a - p[1]*(1-TMath::Cos(rho*len))/a;
1154 x[1] += p[1]*TMath::Sin(rho*len)/a + p[0]*(1-TMath::Cos(rho*len))/a;
1155 x[2] += p[2]*len/pp;
1158 p[0] = p0 *TMath::Cos(rho*len) - p[1]*TMath::Sin(rho*len);
1159 p[1] = p[1]*TMath::Cos(rho*len) + p0 *TMath::Sin(rho*len);
1163 Bool_t AliExternalTrackParam::Intersect(Double_t pnt[3], Double_t norm[3],
1164 Double_t bz) const {
1165 //+++++++++++++++++++++++++++++++++++++++++
1166 // Origin: K. Shileev (Kirill.Shileev@cern.ch)
1167 // Finds point of intersection (if exists) of the helix with the plane.
1168 // Stores result in fX and fP.
1169 // Arguments: planePoint,planeNorm - the plane defined by any plane's point
1170 // and vector, normal to the plane
1171 // Returns: kTrue if helix intersects the plane, kFALSE otherwise.
1172 //+++++++++++++++++++++++++++++++++++++++++
1173 Double_t x0[3]; GetXYZ(x0); //get track position in MARS
1175 //estimates initial helix length up to plane
1177 (pnt[0]-x0[0])*norm[0] + (pnt[1]-x0[1])*norm[1] + (pnt[2]-x0[2])*norm[2];
1178 Double_t dist=99999,distPrev=dist;
1180 while(TMath::Abs(dist)>0.00001){
1181 //calculates helix at the distance s from x0 ALONG the helix
1182 Propagate(s,x,p,bz);
1184 //distance between current helix position and plane
1185 dist=(x[0]-pnt[0])*norm[0]+(x[1]-pnt[1])*norm[1]+(x[2]-pnt[2])*norm[2];
1187 if(TMath::Abs(dist) >= TMath::Abs(distPrev)) {return kFALSE;}
1191 //on exit pnt is intersection point,norm is track vector at that point,
1193 for (Int_t i=0; i<3; i++) {pnt[i]=x[i]; norm[i]=p[i];}
1198 AliExternalTrackParam::GetPredictedChi2(Double_t p[2],Double_t cov[3]) const {
1199 //----------------------------------------------------------------
1200 // Estimate the chi2 of the space point "p" with the cov. matrix "cov"
1201 //----------------------------------------------------------------
1202 Double_t sdd = fC[0] + cov[0];
1203 Double_t sdz = fC[1] + cov[1];
1204 Double_t szz = fC[2] + cov[2];
1205 Double_t det = sdd*szz - sdz*sdz;
1207 if (TMath::Abs(det) < kAlmost0) return kVeryBig;
1209 Double_t d = fP[0] - p[0];
1210 Double_t z = fP[1] - p[1];
1212 return (d*szz*d - 2*d*sdz*z + z*sdd*z)/det;
1215 Double_t AliExternalTrackParam::
1216 GetPredictedChi2(Double_t p[3],Double_t covyz[3],Double_t covxyz[3]) const {
1217 //----------------------------------------------------------------
1218 // Estimate the chi2 of the 3D space point "p" and
1219 // the full covariance matrix "covyz" and "covxyz"
1221 // Cov(x,x) ... : covxyz[0]
1222 // Cov(y,x) ... : covxyz[1] covyz[0]
1223 // Cov(z,x) ... : covxyz[2] covyz[1] covyz[2]
1224 //----------------------------------------------------------------
1232 Double_t f=GetSnp();
1233 if (TMath::Abs(f) >= kAlmost1) return kVeryBig;
1234 Double_t r=TMath::Sqrt((1.-f)*(1.+f));
1235 Double_t a=f/r, b=GetTgl()/r;
1237 Double_t s2=333.*333.; //something reasonably big (cm^2)
1240 v(0,0)= s2; v(0,1)= a*s2; v(0,2)= b*s2;;
1241 v(1,0)=a*s2; v(1,1)=a*a*s2 + GetSigmaY2(); v(1,2)=a*b*s2 + GetSigmaZY();
1242 v(2,0)=b*s2; v(2,1)=a*b*s2 + GetSigmaZY(); v(2,2)=b*b*s2 + GetSigmaZ2();
1244 v(0,0)+=covxyz[0]; v(0,1)+=covxyz[1]; v(0,2)+=covxyz[2];
1245 v(1,0)+=covxyz[1]; v(1,1)+=covyz[0]; v(1,2)+=covyz[1];
1246 v(2,0)+=covxyz[2]; v(2,1)+=covyz[1]; v(2,2)+=covyz[2];
1249 if (!v.IsValid()) return kVeryBig;
1252 for (Int_t i = 0; i < 3; i++)
1253 for (Int_t j = 0; j < 3; j++) chi2 += res[i]*res[j]*v(i,j);
1258 Double_t AliExternalTrackParam::
1259 GetPredictedChi2(const AliExternalTrackParam *t) const {
1260 //----------------------------------------------------------------
1261 // Estimate the chi2 (5 dof) of this track with respect to the track
1262 // given by the argument.
1263 // The two tracks must be in the same reference system
1264 // and estimated at the same reference plane.
1265 //----------------------------------------------------------------
1267 if (TMath::Abs(1. - t->GetAlpha()/GetAlpha()) > FLT_EPSILON) {
1268 AliError("The reference systems of the tracks differ !");
1271 if (TMath::Abs(1. - t->GetX()/GetX()) > FLT_EPSILON) {
1272 AliError("The reference of the tracks planes differ !");
1277 c(0,0)=GetSigmaY2();
1278 c(1,0)=GetSigmaZY(); c(1,1)=GetSigmaZ2();
1279 c(2,0)=GetSigmaSnpY(); c(2,1)=GetSigmaSnpZ(); c(2,2)=GetSigmaSnp2();
1280 c(3,0)=GetSigmaTglY(); c(3,1)=GetSigmaTglZ(); c(3,2)=GetSigmaTglSnp(); c(3,3)=GetSigmaTgl2();
1281 c(4,0)=GetSigma1PtY(); c(4,1)=GetSigma1PtZ(); c(4,2)=GetSigma1PtSnp(); c(4,3)=GetSigma1PtTgl(); c(4,4)=GetSigma1Pt2();
1283 c(0,0)+=t->GetSigmaY2();
1284 c(1,0)+=t->GetSigmaZY(); c(1,1)+=t->GetSigmaZ2();
1285 c(2,0)+=t->GetSigmaSnpY();c(2,1)+=t->GetSigmaSnpZ();c(2,2)+=t->GetSigmaSnp2();
1286 c(3,0)+=t->GetSigmaTglY();c(3,1)+=t->GetSigmaTglZ();c(3,2)+=t->GetSigmaTglSnp();c(3,3)+=t->GetSigmaTgl2();
1287 c(4,0)+=t->GetSigma1PtY();c(4,1)+=t->GetSigma1PtZ();c(4,2)+=t->GetSigma1PtSnp();c(4,3)+=t->GetSigma1PtTgl();c(4,4)+=t->GetSigma1Pt2();
1289 c(0,2)=c(2,0); c(1,2)=c(2,1);
1290 c(0,3)=c(3,0); c(1,3)=c(3,1); c(2,3)=c(3,2);
1291 c(0,4)=c(4,0); c(1,4)=c(4,1); c(2,4)=c(4,2); c(3,4)=c(4,3);
1294 if (!c.IsValid()) return kVeryBig;
1300 GetSnp() - t->GetSnp(),
1301 GetTgl() - t->GetTgl(),
1302 GetSigned1Pt() - t->GetSigned1Pt()
1306 for (Int_t i = 0; i < 5; i++)
1307 for (Int_t j = 0; j < 5; j++) chi2 += res[i]*res[j]*c(i,j);
1312 Bool_t AliExternalTrackParam::
1313 PropagateTo(Double_t p[3],Double_t covyz[3],Double_t covxyz[3],Double_t bz) {
1314 //----------------------------------------------------------------
1315 // Propagate this track to the plane
1316 // the 3D space point "p" (with the covariance matrix "covyz" and "covxyz")
1318 // The magnetic field is "bz" (kG)
1320 // The track curvature and the change of the covariance matrix
1321 // of the track parameters are negleted !
1322 // (So the "step" should be small compared with 1/curvature)
1323 //----------------------------------------------------------------
1325 Double_t f=GetSnp();
1326 if (TMath::Abs(f) >= kAlmost1) return kFALSE;
1327 Double_t r=TMath::Sqrt((1.-f)*(1.+f));
1328 Double_t a=f/r, b=GetTgl()/r;
1330 Double_t s2=333.*333.; //something reasonably big (cm^2)
1333 tV(0,0)= s2; tV(0,1)= a*s2; tV(0,2)= b*s2;
1334 tV(1,0)=a*s2; tV(1,1)=a*a*s2; tV(1,2)=a*b*s2;
1335 tV(2,0)=b*s2; tV(2,1)=a*b*s2; tV(2,2)=b*b*s2;
1338 pV(0,0)=covxyz[0]; pV(0,1)=covxyz[1]; pV(0,2)=covxyz[2];
1339 pV(1,0)=covxyz[1]; pV(1,1)=covyz[0]; pV(1,2)=covyz[1];
1340 pV(2,0)=covxyz[2]; pV(2,1)=covyz[1]; pV(2,2)=covyz[2];
1342 TMatrixDSym tpV(tV);
1345 if (!tpV.IsValid()) return kFALSE;
1347 TMatrixDSym pW(3),tW(3);
1348 for (Int_t i=0; i<3; i++)
1349 for (Int_t j=0; j<3; j++) {
1351 for (Int_t k=0; k<3; k++) {
1352 pW(i,j) += tV(i,k)*tpV(k,j);
1353 tW(i,j) += pV(i,k)*tpV(k,j);
1357 Double_t t[3] = {GetX(), GetY(), GetZ()};
1360 for (Int_t i=0; i<3; i++) x += (tW(0,i)*t[i] + pW(0,i)*p[i]);
1361 Double_t crv=GetC(bz);
1362 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1364 if (TMath::Abs(f) >= kAlmost1) return kFALSE;
1368 for (Int_t i=0; i<3; i++) fP[0] += (tW(1,i)*t[i] + pW(1,i)*p[i]);
1370 for (Int_t i=0; i<3; i++) fP[1] += (tW(2,i)*t[i] + pW(2,i)*p[i]);
1375 Double_t *AliExternalTrackParam::GetResiduals(
1376 Double_t *p,Double_t *cov,Bool_t updated) const {
1377 //------------------------------------------------------------------
1378 // Returns the track residuals with the space point "p" having
1379 // the covariance matrix "cov".
1380 // If "updated" is kTRUE, the track parameters expected to be updated,
1381 // otherwise they must be predicted.
1382 //------------------------------------------------------------------
1383 static Double_t res[2];
1385 Double_t r00=cov[0], r01=cov[1], r11=cov[2];
1387 r00-=fC[0]; r01-=fC[1]; r11-=fC[2];
1389 r00+=fC[0]; r01+=fC[1]; r11+=fC[2];
1391 Double_t det=r00*r11 - r01*r01;
1393 if (TMath::Abs(det) < kAlmost0) return 0;
1395 Double_t tmp=r00; r00=r11/det; r11=tmp/det;
1397 if (r00 < 0.) return 0;
1398 if (r11 < 0.) return 0;
1400 Double_t dy = fP[0] - p[0];
1401 Double_t dz = fP[1] - p[1];
1403 res[0]=dy*TMath::Sqrt(r00);
1404 res[1]=dz*TMath::Sqrt(r11);
1409 Bool_t AliExternalTrackParam::Update(Double_t p[2], Double_t cov[3]) {
1410 //------------------------------------------------------------------
1411 // Update the track parameters with the space point "p" having
1412 // the covariance matrix "cov"
1413 //------------------------------------------------------------------
1414 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
1417 &fC10=fC[1], &fC11=fC[2],
1418 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
1419 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
1420 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
1422 Double_t r00=cov[0], r01=cov[1], r11=cov[2];
1423 r00+=fC00; r01+=fC10; r11+=fC11;
1424 Double_t det=r00*r11 - r01*r01;
1426 if (TMath::Abs(det) < kAlmost0) return kFALSE;
1429 Double_t tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;
1431 Double_t k00=fC00*r00+fC10*r01, k01=fC00*r01+fC10*r11;
1432 Double_t k10=fC10*r00+fC11*r01, k11=fC10*r01+fC11*r11;
1433 Double_t k20=fC20*r00+fC21*r01, k21=fC20*r01+fC21*r11;
1434 Double_t k30=fC30*r00+fC31*r01, k31=fC30*r01+fC31*r11;
1435 Double_t k40=fC40*r00+fC41*r01, k41=fC40*r01+fC41*r11;
1437 Double_t dy=p[0] - fP0, dz=p[1] - fP1;
1438 Double_t sf=fP2 + k20*dy + k21*dz;
1439 if (TMath::Abs(sf) > kAlmost1) return kFALSE;
1441 fP0 += k00*dy + k01*dz;
1442 fP1 += k10*dy + k11*dz;
1444 fP3 += k30*dy + k31*dz;
1445 fP4 += k40*dy + k41*dz;
1447 Double_t c01=fC10, c02=fC20, c03=fC30, c04=fC40;
1448 Double_t c12=fC21, c13=fC31, c14=fC41;
1450 fC00-=k00*fC00+k01*fC10; fC10-=k00*c01+k01*fC11;
1451 fC20-=k00*c02+k01*c12; fC30-=k00*c03+k01*c13;
1452 fC40-=k00*c04+k01*c14;
1454 fC11-=k10*c01+k11*fC11;
1455 fC21-=k10*c02+k11*c12; fC31-=k10*c03+k11*c13;
1456 fC41-=k10*c04+k11*c14;
1458 fC22-=k20*c02+k21*c12; fC32-=k20*c03+k21*c13;
1459 fC42-=k20*c04+k21*c14;
1461 fC33-=k30*c03+k31*c13;
1462 fC43-=k30*c04+k31*c14;
1464 fC44-=k40*c04+k41*c14;
1472 AliExternalTrackParam::GetHelixParameters(Double_t hlx[6], Double_t b) const {
1473 //--------------------------------------------------------------------
1474 // External track parameters -> helix parameters
1475 // "b" - magnetic field (kG)
1476 //--------------------------------------------------------------------
1477 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1479 hlx[0]=fP[0]; hlx[1]=fP[1]; hlx[2]=fP[2]; hlx[3]=fP[3];
1481 hlx[5]=fX*cs - hlx[0]*sn; // x0
1482 hlx[0]=fX*sn + hlx[0]*cs; // y0
1484 hlx[2]=TMath::ASin(hlx[2]) + fAlpha; // phi0
1486 hlx[4]=GetC(b); // C
1490 static void Evaluate(const Double_t *h, Double_t t,
1491 Double_t r[3], //radius vector
1492 Double_t g[3], //first defivatives
1493 Double_t gg[3]) //second derivatives
1495 //--------------------------------------------------------------------
1496 // Calculate position of a point on a track and some derivatives
1497 //--------------------------------------------------------------------
1498 Double_t phase=h[4]*t+h[2];
1499 Double_t sn=TMath::Sin(phase), cs=TMath::Cos(phase);
1503 if (TMath::Abs(h[4])>kAlmost0) {
1504 r[0] += (sn - h[6])/h[4];
1505 r[1] -= (cs - h[7])/h[4];
1507 r[2] = h[1] + h[3]*t;
1509 g[0] = cs; g[1]=sn; g[2]=h[3];
1511 gg[0]=-h[4]*sn; gg[1]=h[4]*cs; gg[2]=0.;
1514 Double_t AliExternalTrackParam::GetDCA(const AliExternalTrackParam *p,
1515 Double_t b, Double_t &xthis, Double_t &xp) const {
1516 //------------------------------------------------------------
1517 // Returns the (weighed !) distance of closest approach between
1518 // this track and the track "p".
1519 // Other returned values:
1520 // xthis, xt - coordinates of tracks' reference planes at the DCA
1521 //-----------------------------------------------------------
1522 Double_t dy2=GetSigmaY2() + p->GetSigmaY2();
1523 Double_t dz2=GetSigmaZ2() + p->GetSigmaZ2();
1526 Double_t p1[8]; GetHelixParameters(p1,b);
1527 p1[6]=TMath::Sin(p1[2]); p1[7]=TMath::Cos(p1[2]);
1528 Double_t p2[8]; p->GetHelixParameters(p2,b);
1529 p2[6]=TMath::Sin(p2[2]); p2[7]=TMath::Cos(p2[2]);
1532 Double_t r1[3],g1[3],gg1[3]; Double_t t1=0.;
1533 Evaluate(p1,t1,r1,g1,gg1);
1534 Double_t r2[3],g2[3],gg2[3]; Double_t t2=0.;
1535 Evaluate(p2,t2,r2,g2,gg2);
1537 Double_t dx=r2[0]-r1[0], dy=r2[1]-r1[1], dz=r2[2]-r1[2];
1538 Double_t dm=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
1542 Double_t gt1=-(dx*g1[0]/dx2 + dy*g1[1]/dy2 + dz*g1[2]/dz2);
1543 Double_t gt2=+(dx*g2[0]/dx2 + dy*g2[1]/dy2 + dz*g2[2]/dz2);
1544 Double_t h11=(g1[0]*g1[0] - dx*gg1[0])/dx2 +
1545 (g1[1]*g1[1] - dy*gg1[1])/dy2 +
1546 (g1[2]*g1[2] - dz*gg1[2])/dz2;
1547 Double_t h22=(g2[0]*g2[0] + dx*gg2[0])/dx2 +
1548 (g2[1]*g2[1] + dy*gg2[1])/dy2 +
1549 (g2[2]*g2[2] + dz*gg2[2])/dz2;
1550 Double_t h12=-(g1[0]*g2[0]/dx2 + g1[1]*g2[1]/dy2 + g1[2]*g2[2]/dz2);
1552 Double_t det=h11*h22-h12*h12;
1555 if (TMath::Abs(det)<1.e-33) {
1556 //(quasi)singular Hessian
1559 dt1=-(gt1*h22 - gt2*h12)/det;
1560 dt2=-(h11*gt2 - h12*gt1)/det;
1563 if ((dt1*gt1+dt2*gt2)>0) {dt1=-dt1; dt2=-dt2;}
1565 //check delta(phase1) ?
1566 //check delta(phase2) ?
1568 if (TMath::Abs(dt1)/(TMath::Abs(t1)+1.e-3) < 1.e-4)
1569 if (TMath::Abs(dt2)/(TMath::Abs(t2)+1.e-3) < 1.e-4) {
1570 if ((gt1*gt1+gt2*gt2) > 1.e-4/dy2/dy2)
1571 AliDebug(1," stopped at not a stationary point !");
1572 Double_t lmb=h11+h22; lmb=lmb-TMath::Sqrt(lmb*lmb-4*det);
1574 AliDebug(1," stopped at not a minimum !");
1579 for (Int_t div=1 ; ; div*=2) {
1580 Evaluate(p1,t1+dt1,r1,g1,gg1);
1581 Evaluate(p2,t2+dt2,r2,g2,gg2);
1582 dx=r2[0]-r1[0]; dy=r2[1]-r1[1]; dz=r2[2]-r1[2];
1583 dd=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
1587 AliDebug(1," overshoot !"); break;
1597 if (max<=0) AliDebug(1," too many iterations !");
1599 Double_t cs=TMath::Cos(GetAlpha());
1600 Double_t sn=TMath::Sin(GetAlpha());
1601 xthis=r1[0]*cs + r1[1]*sn;
1603 cs=TMath::Cos(p->GetAlpha());
1604 sn=TMath::Sin(p->GetAlpha());
1605 xp=r2[0]*cs + r2[1]*sn;
1607 return TMath::Sqrt(dm*TMath::Sqrt(dy2*dz2));
1610 Double_t AliExternalTrackParam::
1611 PropagateToDCA(AliExternalTrackParam *p, Double_t b) {
1612 //--------------------------------------------------------------
1613 // Propagates this track and the argument track to the position of the
1614 // distance of closest approach.
1615 // Returns the (weighed !) distance of closest approach.
1616 //--------------------------------------------------------------
1618 Double_t dca=GetDCA(p,b,xthis,xp);
1620 if (!PropagateTo(xthis,b)) {
1621 //AliWarning(" propagation failed !");
1625 if (!p->PropagateTo(xp,b)) {
1626 //AliWarning(" propagation failed !";
1634 Bool_t AliExternalTrackParam::PropagateToDCA(const AliVVertex *vtx,
1635 Double_t b, Double_t maxd, Double_t dz[2], Double_t covar[3]) {
1637 // Propagate this track to the DCA to vertex "vtx",
1638 // if the (rough) transverse impact parameter is not bigger then "maxd".
1639 // Magnetic field is "b" (kG).
1641 // a) The track gets extapolated to the DCA to the vertex.
1642 // b) The impact parameters and their covariance matrix are calculated.
1644 // In the case of success, the returned value is kTRUE
1645 // (otherwise, it's kFALSE)
1647 Double_t alpha=GetAlpha();
1648 Double_t sn=TMath::Sin(alpha), cs=TMath::Cos(alpha);
1649 Double_t x=GetX(), y=GetParameter()[0], snp=GetParameter()[2];
1650 Double_t xv= vtx->GetX()*cs + vtx->GetY()*sn;
1651 Double_t yv=-vtx->GetX()*sn + vtx->GetY()*cs, zv=vtx->GetZ();
1654 //Estimate the impact parameter neglecting the track curvature
1655 Double_t d=TMath::Abs(x*snp - y*TMath::Sqrt((1.-snp)*(1.+snp)));
1656 if (d > maxd) return kFALSE;
1658 //Propagate to the DCA
1659 Double_t crv=GetC(b);
1660 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1662 Double_t tgfv=-(crv*x - snp)/(crv*y + TMath::Sqrt((1.-snp)*(1.+snp)));
1663 sn=tgfv/TMath::Sqrt(1.+ tgfv*tgfv); cs=TMath::Sqrt((1.-sn)*(1.+sn));
1664 if (TMath::Abs(tgfv)>0.) cs = sn/tgfv;
1668 yv=-xv*sn + yv*cs; xv=x;
1670 if (!Propagate(alpha+TMath::ASin(sn),xv,b)) return kFALSE;
1672 if (dz==0) return kTRUE;
1673 dz[0] = GetParameter()[0] - yv;
1674 dz[1] = GetParameter()[1] - zv;
1676 if (covar==0) return kTRUE;
1677 Double_t cov[6]; vtx->GetCovarianceMatrix(cov);
1679 //***** Improvements by A.Dainese
1680 alpha=GetAlpha(); sn=TMath::Sin(alpha); cs=TMath::Cos(alpha);
1681 Double_t s2ylocvtx = cov[0]*sn*sn + cov[2]*cs*cs - 2.*cov[1]*cs*sn;
1682 covar[0] = GetCovariance()[0] + s2ylocvtx; // neglecting correlations
1683 covar[1] = GetCovariance()[1]; // between (x,y) and z
1684 covar[2] = GetCovariance()[2] + cov[5]; // in vertex's covariance matrix
1690 Bool_t AliExternalTrackParam::PropagateToDCABxByBz(const AliVVertex *vtx,
1691 Double_t b[3], Double_t maxd, Double_t dz[2], Double_t covar[3]) {
1693 // Propagate this track to the DCA to vertex "vtx",
1694 // if the (rough) transverse impact parameter is not bigger then "maxd".
1696 // This function takes into account all three components of the magnetic
1697 // field given by the b[3] arument (kG)
1699 // a) The track gets extapolated to the DCA to the vertex.
1700 // b) The impact parameters and their covariance matrix are calculated.
1702 // In the case of success, the returned value is kTRUE
1703 // (otherwise, it's kFALSE)
1705 Double_t alpha=GetAlpha();
1706 Double_t sn=TMath::Sin(alpha), cs=TMath::Cos(alpha);
1707 Double_t x=GetX(), y=GetParameter()[0], snp=GetParameter()[2];
1708 Double_t xv= vtx->GetX()*cs + vtx->GetY()*sn;
1709 Double_t yv=-vtx->GetX()*sn + vtx->GetY()*cs, zv=vtx->GetZ();
1712 //Estimate the impact parameter neglecting the track curvature
1713 Double_t d=TMath::Abs(x*snp - y*TMath::Sqrt((1.-snp)*(1.+snp)));
1714 if (d > maxd) return kFALSE;
1716 //Propagate to the DCA
1717 Double_t crv=GetC(b[2]);
1718 if (TMath::Abs(b[2]) < kAlmost0Field) crv=0.;
1720 Double_t tgfv=-(crv*x - snp)/(crv*y + TMath::Sqrt((1.-snp)*(1.+snp)));
1721 sn=tgfv/TMath::Sqrt(1.+ tgfv*tgfv); cs=TMath::Sqrt((1.-sn)*(1.+sn));
1722 if (TMath::Abs(tgfv)>0.) cs = sn/tgfv;
1726 yv=-xv*sn + yv*cs; xv=x;
1728 if (!PropagateBxByBz(alpha+TMath::ASin(sn),xv,b)) return kFALSE;
1730 if (dz==0) return kTRUE;
1731 dz[0] = GetParameter()[0] - yv;
1732 dz[1] = GetParameter()[1] - zv;
1734 if (covar==0) return kTRUE;
1735 Double_t cov[6]; vtx->GetCovarianceMatrix(cov);
1737 //***** Improvements by A.Dainese
1738 alpha=GetAlpha(); sn=TMath::Sin(alpha); cs=TMath::Cos(alpha);
1739 Double_t s2ylocvtx = cov[0]*sn*sn + cov[2]*cs*cs - 2.*cov[1]*cs*sn;
1740 covar[0] = GetCovariance()[0] + s2ylocvtx; // neglecting correlations
1741 covar[1] = GetCovariance()[1]; // between (x,y) and z
1742 covar[2] = GetCovariance()[2] + cov[5]; // in vertex's covariance matrix
1748 void AliExternalTrackParam::GetDirection(Double_t d[3]) const {
1749 //----------------------------------------------------------------
1750 // This function returns a unit vector along the track direction
1751 // in the global coordinate system.
1752 //----------------------------------------------------------------
1753 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1755 Double_t csp =TMath::Sqrt((1.-snp)*(1.+snp));
1756 Double_t norm=TMath::Sqrt(1.+ fP[3]*fP[3]);
1757 d[0]=(csp*cs - snp*sn)/norm;
1758 d[1]=(snp*cs + csp*sn)/norm;
1762 Bool_t AliExternalTrackParam::GetPxPyPz(Double_t p[3]) const {
1763 //---------------------------------------------------------------------
1764 // This function returns the global track momentum components
1765 // Results for (nearly) straight tracks are meaningless !
1766 //---------------------------------------------------------------------
1767 p[0]=fP[4]; p[1]=fP[2]; p[2]=fP[3];
1768 return Local2GlobalMomentum(p,fAlpha);
1771 Double_t AliExternalTrackParam::Px() const {
1772 //---------------------------------------------------------------------
1773 // Returns x-component of momentum
1774 // Result for (nearly) straight tracks is meaningless !
1775 //---------------------------------------------------------------------
1777 Double_t p[3]={kVeryBig,kVeryBig,kVeryBig};
1783 Double_t AliExternalTrackParam::Py() const {
1784 //---------------------------------------------------------------------
1785 // Returns y-component of momentum
1786 // Result for (nearly) straight tracks is meaningless !
1787 //---------------------------------------------------------------------
1789 Double_t p[3]={kVeryBig,kVeryBig,kVeryBig};
1795 Double_t AliExternalTrackParam::Xv() const {
1796 //---------------------------------------------------------------------
1797 // Returns x-component of first track point
1798 //---------------------------------------------------------------------
1800 Double_t r[3]={0.,0.,0.};
1806 Double_t AliExternalTrackParam::Yv() const {
1807 //---------------------------------------------------------------------
1808 // Returns y-component of first track point
1809 //---------------------------------------------------------------------
1811 Double_t r[3]={0.,0.,0.};
1817 Double_t AliExternalTrackParam::Theta() const {
1818 // return theta angle of momentum
1820 return 0.5*TMath::Pi() - TMath::ATan(fP[3]);
1823 Double_t AliExternalTrackParam::Phi() const {
1824 //---------------------------------------------------------------------
1825 // Returns the azimuthal angle of momentum
1827 //---------------------------------------------------------------------
1829 Double_t phi=TMath::ASin(fP[2]) + fAlpha;
1830 if (phi<0.) phi+=2.*TMath::Pi();
1831 else if (phi>=2.*TMath::Pi()) phi-=2.*TMath::Pi();
1836 Double_t AliExternalTrackParam::M() const {
1837 // return particle mass
1839 // No mass information available so far.
1840 // Redifine in derived class!
1845 Double_t AliExternalTrackParam::E() const {
1846 // return particle energy
1848 // No PID information available so far.
1849 // Redifine in derived class!
1854 Double_t AliExternalTrackParam::Eta() const {
1855 // return pseudorapidity
1857 return -TMath::Log(TMath::Tan(0.5 * Theta()));
1860 Double_t AliExternalTrackParam::Y() const {
1863 // No PID information available so far.
1864 // Redifine in derived class!
1869 Bool_t AliExternalTrackParam::GetXYZ(Double_t *r) const {
1870 //---------------------------------------------------------------------
1871 // This function returns the global track position
1872 //---------------------------------------------------------------------
1873 r[0]=fX; r[1]=fP[0]; r[2]=fP[1];
1874 return Local2GlobalPosition(r,fAlpha);
1877 Bool_t AliExternalTrackParam::GetCovarianceXYZPxPyPz(Double_t cv[21]) const {
1878 //---------------------------------------------------------------------
1879 // This function returns the global covariance matrix of the track params
1881 // Cov(x,x) ... : cv[0]
1882 // Cov(y,x) ... : cv[1] cv[2]
1883 // Cov(z,x) ... : cv[3] cv[4] cv[5]
1884 // Cov(px,x)... : cv[6] cv[7] cv[8] cv[9]
1885 // Cov(py,x)... : cv[10] cv[11] cv[12] cv[13] cv[14]
1886 // Cov(pz,x)... : cv[15] cv[16] cv[17] cv[18] cv[19] cv[20]
1888 // Results for (nearly) straight tracks are meaningless !
1889 //---------------------------------------------------------------------
1890 if (TMath::Abs(fP[4])<=kAlmost0) {
1891 for (Int_t i=0; i<21; i++) cv[i]=0.;
1894 if (TMath::Abs(fP[2]) > kAlmost1) {
1895 for (Int_t i=0; i<21; i++) cv[i]=0.;
1898 Double_t pt=1./TMath::Abs(fP[4]);
1899 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1900 Double_t r=TMath::Sqrt((1.-fP[2])*(1.+fP[2]));
1902 Double_t m00=-sn, m10=cs;
1903 Double_t m23=-pt*(sn + fP[2]*cs/r), m43=-pt*pt*(r*cs - fP[2]*sn);
1904 Double_t m24= pt*(cs - fP[2]*sn/r), m44=-pt*pt*(r*sn + fP[2]*cs);
1905 Double_t m35=pt, m45=-pt*pt*fP[3];
1911 cv[0 ] = fC[0]*m00*m00;
1912 cv[1 ] = fC[0]*m00*m10;
1913 cv[2 ] = fC[0]*m10*m10;
1917 cv[6 ] = m00*(fC[3]*m23 + fC[10]*m43);
1918 cv[7 ] = m10*(fC[3]*m23 + fC[10]*m43);
1919 cv[8 ] = fC[4]*m23 + fC[11]*m43;
1920 cv[9 ] = m23*(fC[5]*m23 + fC[12]*m43) + m43*(fC[12]*m23 + fC[14]*m43);
1921 cv[10] = m00*(fC[3]*m24 + fC[10]*m44);
1922 cv[11] = m10*(fC[3]*m24 + fC[10]*m44);
1923 cv[12] = fC[4]*m24 + fC[11]*m44;
1924 cv[13] = m23*(fC[5]*m24 + fC[12]*m44) + m43*(fC[12]*m24 + fC[14]*m44);
1925 cv[14] = m24*(fC[5]*m24 + fC[12]*m44) + m44*(fC[12]*m24 + fC[14]*m44);
1926 cv[15] = m00*(fC[6]*m35 + fC[10]*m45);
1927 cv[16] = m10*(fC[6]*m35 + fC[10]*m45);
1928 cv[17] = fC[7]*m35 + fC[11]*m45;
1929 cv[18] = m23*(fC[8]*m35 + fC[12]*m45) + m43*(fC[13]*m35 + fC[14]*m45);
1930 cv[19] = m24*(fC[8]*m35 + fC[12]*m45) + m44*(fC[13]*m35 + fC[14]*m45);
1931 cv[20] = m35*(fC[9]*m35 + fC[13]*m45) + m45*(fC[13]*m35 + fC[14]*m45);
1938 AliExternalTrackParam::GetPxPyPzAt(Double_t x, Double_t b, Double_t *p) const {
1939 //---------------------------------------------------------------------
1940 // This function returns the global track momentum extrapolated to
1941 // the radial position "x" (cm) in the magnetic field "b" (kG)
1942 //---------------------------------------------------------------------
1944 p[1]=fP[2]+(x-fX)*GetC(b);
1946 return Local2GlobalMomentum(p,fAlpha);
1950 AliExternalTrackParam::GetYAt(Double_t x, Double_t b, Double_t &y) const {
1951 //---------------------------------------------------------------------
1952 // This function returns the local Y-coordinate of the intersection
1953 // point between this track and the reference plane "x" (cm).
1954 // Magnetic field "b" (kG)
1955 //---------------------------------------------------------------------
1957 if(TMath::Abs(dx)<=kAlmost0) {y=fP[0]; return kTRUE;}
1959 Double_t f1=fP[2], f2=f1 + dx*GetC(b);
1961 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1962 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1964 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
1965 y = fP[0] + dx*(f1+f2)/(r1+r2);
1970 AliExternalTrackParam::GetZAt(Double_t x, Double_t b, Double_t &z) const {
1971 //---------------------------------------------------------------------
1972 // This function returns the local Z-coordinate of the intersection
1973 // point between this track and the reference plane "x" (cm).
1974 // Magnetic field "b" (kG)
1975 //---------------------------------------------------------------------
1977 if(TMath::Abs(dx)<=kAlmost0) {z=fP[1]; return kTRUE;}
1979 Double_t crv=GetC(b);
1980 Double_t x2r = crv*dx;
1981 Double_t f1=fP[2], f2=f1 + x2r;
1983 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1984 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1986 Double_t r1=sqrt((1.-f1)*(1.+f1)), r2=sqrt((1.-f2)*(1.+f2));
1987 double dy2dx = (f1+f2)/(r1+r2);
1988 if (TMath::Abs(x2r)<0.05) {
1989 z = fP[1] + dx*(r2 + f2*dy2dx)*fP[3]; // Many thanks to P.Hristov !
1992 // for small dx/R the linear apporximation of the arc by the segment is OK,
1993 // but at large dx/R the error is very large and leads to incorrect Z propagation
1994 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
1995 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
1996 // Similarly, the rotation angle in linear in dx only for dx<<R
1997 double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
1998 double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
1999 z = fP[1] + rot/crv*fP[3];
2005 AliExternalTrackParam::GetXYZAt(Double_t x, Double_t b, Double_t *r) const {
2006 //---------------------------------------------------------------------
2007 // This function returns the global track position extrapolated to
2008 // the radial position "x" (cm) in the magnetic field "b" (kG)
2009 //---------------------------------------------------------------------
2011 if(TMath::Abs(dx)<=kAlmost0) return GetXYZ(r);
2013 Double_t crv=GetC(b);
2014 Double_t x2r = crv*dx;
2015 Double_t f1=fP[2], f2=f1 + dx*crv;
2017 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
2018 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
2020 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
2021 double dy2dx = (f1+f2)/(r1+r2);
2023 r[1] = fP[0] + dx*dy2dx;
2024 if (TMath::Abs(x2r)<0.05) {
2025 r[2] = fP[1] + dx*(r2 + f2*dy2dx)*fP[3];//Thanks to Andrea & Peter
2028 // for small dx/R the linear apporximation of the arc by the segment is OK,
2029 // but at large dx/R the error is very large and leads to incorrect Z propagation
2030 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
2031 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
2032 // Similarly, the rotation angle in linear in dx only for dx<<R
2033 double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
2034 double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
2035 r[2] = fP[1] + rot/crv*fP[3];
2038 return Local2GlobalPosition(r,fAlpha);
2041 //_____________________________________________________________________________
2042 void AliExternalTrackParam::Print(Option_t* /*option*/) const
2044 // print the parameters and the covariance matrix
2046 printf("AliExternalTrackParam: x = %-12g alpha = %-12g\n", fX, fAlpha);
2047 printf(" parameters: %12g %12g %12g %12g %12g\n",
2048 fP[0], fP[1], fP[2], fP[3], fP[4]);
2049 printf(" covariance: %12g\n", fC[0]);
2050 printf(" %12g %12g\n", fC[1], fC[2]);
2051 printf(" %12g %12g %12g\n", fC[3], fC[4], fC[5]);
2052 printf(" %12g %12g %12g %12g\n",
2053 fC[6], fC[7], fC[8], fC[9]);
2054 printf(" %12g %12g %12g %12g %12g\n",
2055 fC[10], fC[11], fC[12], fC[13], fC[14]);
2058 Double_t AliExternalTrackParam::GetSnpAt(Double_t x,Double_t b) const {
2060 // Get sinus at given x
2062 Double_t crv=GetC(b);
2063 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
2065 Double_t res = fP[2]+dx*crv;
2069 Bool_t AliExternalTrackParam::GetDistance(AliExternalTrackParam *param2, Double_t x, Double_t dist[3], Double_t bz){
2070 //------------------------------------------------------------------------
2071 // Get the distance between two tracks at the local position x
2072 // working in the local frame of this track.
2073 // Origin : Marian.Ivanov@cern.ch
2074 //-----------------------------------------------------------------------
2078 if (!GetYAt(x,bz,xyz[1])) return kFALSE;
2079 if (!GetZAt(x,bz,xyz[2])) return kFALSE;
2082 if (TMath::Abs(GetAlpha()-param2->GetAlpha())<kAlmost0){
2084 if (!param2->GetYAt(x,bz,xyz2[1])) return kFALSE;
2085 if (!param2->GetZAt(x,bz,xyz2[2])) return kFALSE;
2089 Double_t dfi = param2->GetAlpha()-GetAlpha();
2090 Double_t ca = TMath::Cos(dfi), sa = TMath::Sin(dfi);
2091 xyz2[0] = xyz[0]*ca+xyz[1]*sa;
2092 xyz2[1] = -xyz[0]*sa+xyz[1]*ca;
2095 if (!param2->GetYAt(xyz2[0],bz,xyz1[1])) return kFALSE;
2096 if (!param2->GetZAt(xyz2[0],bz,xyz1[2])) return kFALSE;
2098 xyz2[0] = xyz1[0]*ca-xyz1[1]*sa;
2099 xyz2[1] = +xyz1[0]*sa+xyz1[1]*ca;
2102 dist[0] = xyz[0]-xyz2[0];
2103 dist[1] = xyz[1]-xyz2[1];
2104 dist[2] = xyz[2]-xyz2[2];
2111 // Draw functionality.
2112 // Origin: Marian Ivanov, Marian.Ivanov@cern.ch
2115 void AliExternalTrackParam::DrawTrack(Float_t magf, Float_t minR, Float_t maxR, Float_t stepR){
2119 if (minR>maxR) return ;
2120 if (stepR<=0) return ;
2121 Int_t npoints = TMath::Nint((maxR-minR)/stepR)+1;
2122 if (npoints<1) return;
2123 TPolyMarker3D *polymarker = new TPolyMarker3D(npoints);
2124 FillPolymarker(polymarker, magf,minR,maxR,stepR);
2129 void AliExternalTrackParam::FillPolymarker(TPolyMarker3D *pol, Float_t magF, Float_t minR, Float_t maxR, Float_t stepR){
2131 // Fill points in the polymarker
2134 for (Double_t r=minR; r<maxR; r+=stepR){
2136 GetXYZAt(r,magF,point);
2137 pol->SetPoint(counter,point[0],point[1], point[2]);
2138 // printf("xyz\t%f\t%f\t%f\n",point[0], point[1],point[2]);
2143 Int_t AliExternalTrackParam::GetIndex(Int_t i, Int_t j) const {
2145 Int_t min = TMath::Min(i,j);
2146 Int_t max = TMath::Max(i,j);
2148 return min+(max+1)*max/2;
2152 void AliExternalTrackParam::g3helx3(Double_t qfield,
2155 /******************************************************************
2157 * GEANT3 tracking routine in a constant field oriented *
2159 * Tracking is performed with a conventional *
2160 * helix step method *
2162 * Authors R.Brun, M.Hansroul ********* *
2163 * Rewritten V.Perevoztchikov *
2165 * Rewritten in C++ by I.Belikov *
2167 * qfield (kG) - particle charge times magnetic field *
2168 * step (cm) - step length along the helix *
2169 * vect[7](cm,GeV/c) - input/output x, y, z, px/p, py/p ,pz/p, p *
2171 ******************************************************************/
2172 const Int_t ix=0, iy=1, iz=2, ipx=3, ipy=4, ipz=5, ipp=6;
2173 const Double_t kOvSqSix=TMath::Sqrt(1./6.);
2175 Double_t cosx=vect[ipx], cosy=vect[ipy], cosz=vect[ipz];
2177 Double_t rho = qfield*kB2C/vect[ipp];
2178 Double_t tet = rho*step;
2180 Double_t tsint, sintt, sint, cos1t;
2181 if (TMath::Abs(tet) > 0.03) {
2182 sint = TMath::Sin(tet);
2184 tsint = (tet - sint)/tet;
2185 Double_t t=TMath::Sin(0.5*tet);
2189 sintt = (1.-tet*kOvSqSix)*(1.+tet*kOvSqSix); // 1.- tsint;
2194 Double_t f1 = step*sintt;
2195 Double_t f2 = step*cos1t;
2196 Double_t f3 = step*tsint*cosz;
2197 Double_t f4 = -tet*cos1t;
2200 vect[ix] += f1*cosx - f2*cosy;
2201 vect[iy] += f1*cosy + f2*cosx;
2202 vect[iz] += f1*cosz + f3;
2204 vect[ipx] += f4*cosx - f5*cosy;
2205 vect[ipy] += f4*cosy + f5*cosx;
2209 Bool_t AliExternalTrackParam::PropagateToBxByBz(Double_t xk, const Double_t b[3]) {
2210 //----------------------------------------------------------------
2211 // Extrapolate this track to the plane X=xk in the field b[].
2213 // X [cm] is in the "tracking coordinate system" of this track.
2214 // b[]={Bx,By,Bz} [kG] is in the Global coordidate system.
2215 //----------------------------------------------------------------
2218 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
2219 if (TMath::Abs(fP[4])<=kAlmost0) return kFALSE;
2220 // Do not propagate tracks outside the ALICE detector
2221 if (TMath::Abs(dx)>1e5 ||
2222 TMath::Abs(GetY())>1e5 ||
2223 TMath::Abs(GetZ())>1e5) {
2224 AliWarning(Form("Anomalous track, target X:%f",xk));
2229 Double_t crv=GetC(b[2]);
2230 if (TMath::Abs(b[2]) < kAlmost0Field) crv=0.;
2232 Double_t x2r = crv*dx;
2233 Double_t f1=fP[2], f2=f1 + x2r;
2234 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
2235 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
2238 // Estimate the covariance matrix
2239 Double_t &fP3=fP[3], &fP4=fP[4];
2242 &fC10=fC[1], &fC11=fC[2],
2243 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
2244 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
2245 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
2247 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
2251 Double_t f02= dx/(r1*r1*r1); Double_t cc=crv/fP4;
2252 Double_t f04=0.5*dx*dx/(r1*r1*r1); f04*=cc;
2253 Double_t f12= dx*fP3*f1/(r1*r1*r1);
2254 Double_t f14=0.5*dx*dx*fP3*f1/(r1*r1*r1); f14*=cc;
2255 Double_t f13= dx/r1;
2256 Double_t f24= dx; f24*=cc;
2258 Double_t rinv = 1./r1;
2259 Double_t r3inv = rinv*rinv*rinv;
2260 Double_t f24= x2r/fP4;
2261 Double_t f02= dx*r3inv;
2262 Double_t f04=0.5*f24*f02;
2263 Double_t f12= f02*fP3*f1;
2264 Double_t f14=0.5*f24*f02*fP3*f1;
2265 Double_t f13= dx*rinv;
2268 Double_t b00=f02*fC20 + f04*fC40, b01=f12*fC20 + f14*fC40 + f13*fC30;
2269 Double_t b02=f24*fC40;
2270 Double_t b10=f02*fC21 + f04*fC41, b11=f12*fC21 + f14*fC41 + f13*fC31;
2271 Double_t b12=f24*fC41;
2272 Double_t b20=f02*fC22 + f04*fC42, b21=f12*fC22 + f14*fC42 + f13*fC32;
2273 Double_t b22=f24*fC42;
2274 Double_t b40=f02*fC42 + f04*fC44, b41=f12*fC42 + f14*fC44 + f13*fC43;
2275 Double_t b42=f24*fC44;
2276 Double_t b30=f02*fC32 + f04*fC43, b31=f12*fC32 + f14*fC43 + f13*fC33;
2277 Double_t b32=f24*fC43;
2280 Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a02=f02*b22+f04*b42;
2281 Double_t a11=f12*b21+f14*b41+f13*b31,a12=f12*b22+f14*b42+f13*b32;
2282 Double_t a22=f24*b42;
2284 //F*C*Ft = C + (b + bt + a)
2285 fC00 += b00 + b00 + a00;
2286 fC10 += b10 + b01 + a01;
2287 fC20 += b20 + b02 + a02;
2290 fC11 += b11 + b11 + a11;
2291 fC21 += b21 + b12 + a12;
2294 fC22 += b22 + b22 + a22;
2300 // Appoximate step length
2301 double dy2dx = (f1+f2)/(r1+r2);
2302 Double_t step = (TMath::Abs(x2r)<0.05) ? dx*TMath::Abs(r2 + f2*dy2dx) // chord
2303 : 2.*TMath::ASin(0.5*dx*TMath::Sqrt(1.+dy2dx*dy2dx)*crv)/crv; // arc
2304 step *= TMath::Sqrt(1.+ GetTgl()*GetTgl());
2306 // Get the track's (x,y,z) and (px,py,pz) in the Global System
2307 Double_t r[3]; GetXYZ(r);
2308 Double_t p[3]; GetPxPyPz(p);
2315 // Rotate to the system where Bx=By=0.
2316 Double_t bt=TMath::Sqrt(b[0]*b[0] + b[1]*b[1]);
2317 Double_t cosphi=1., sinphi=0.;
2318 if (bt > kAlmost0) {cosphi=b[0]/bt; sinphi=b[1]/bt;}
2319 Double_t bb=TMath::Sqrt(b[0]*b[0] + b[1]*b[1] + b[2]*b[2]);
2320 Double_t costet=1., sintet=0.;
2321 if (bb > kAlmost0) {costet=b[2]/bb; sintet=bt/bb;}
2324 vect[0] = costet*cosphi*r[0] + costet*sinphi*r[1] - sintet*r[2];
2325 vect[1] = -sinphi*r[0] + cosphi*r[1];
2326 vect[2] = sintet*cosphi*r[0] + sintet*sinphi*r[1] + costet*r[2];
2328 vect[3] = costet*cosphi*p[0] + costet*sinphi*p[1] - sintet*p[2];
2329 vect[4] = -sinphi*p[0] + cosphi*p[1];
2330 vect[5] = sintet*cosphi*p[0] + sintet*sinphi*p[1] + costet*p[2];
2335 // Do the helix step
2336 g3helx3(GetSign()*bb,step,vect);
2339 // Rotate back to the Global System
2340 r[0] = cosphi*costet*vect[0] - sinphi*vect[1] + cosphi*sintet*vect[2];
2341 r[1] = sinphi*costet*vect[0] + cosphi*vect[1] + sinphi*sintet*vect[2];
2342 r[2] = -sintet*vect[0] + costet*vect[2];
2344 p[0] = cosphi*costet*vect[3] - sinphi*vect[4] + cosphi*sintet*vect[5];
2345 p[1] = sinphi*costet*vect[3] + cosphi*vect[4] + sinphi*sintet*vect[5];
2346 p[2] = -sintet*vect[3] + costet*vect[5];
2349 // Rotate back to the Tracking System
2350 Double_t cosalp = TMath::Cos(fAlpha);
2351 Double_t sinalp =-TMath::Sin(fAlpha);
2354 t = cosalp*r[0] - sinalp*r[1];
2355 r[1] = sinalp*r[0] + cosalp*r[1];
2358 t = cosalp*p[0] - sinalp*p[1];
2359 p[1] = sinalp*p[0] + cosalp*p[1];
2363 // Do the final correcting step to the target plane (linear approximation)
2364 Double_t x=r[0], y=r[1], z=r[2];
2365 if (TMath::Abs(dx) > kAlmost0) {
2366 if (TMath::Abs(p[0]) < kAlmost0) return kFALSE;
2374 // Calculate the track parameters
2375 t=TMath::Sqrt(p[0]*p[0] + p[1]*p[1]);
2381 fP[4] = GetSign()/(t*pp);
2386 Bool_t AliExternalTrackParam::Translate(Double_t *vTrasl,Double_t *covV){
2388 //Translation: in the event mixing, the tracks can be shifted
2389 //of the difference among primary vertices (vTrasl) and
2390 //the covariance matrix is changed accordingly
2391 //(covV = covariance of the primary vertex).
2392 //Origin: "Romita, Rossella" <R.Romita@gsi.de>
2394 TVector3 translation;
2395 // vTrasl coordinates in the local system
2396 translation.SetXYZ(vTrasl[0],vTrasl[1],vTrasl[2]);
2397 translation.RotateZ(-fAlpha);
2398 translation.GetXYZ(vTrasl);
2400 //compute the new x,y,z of the track
2401 Double_t newX=fX-vTrasl[0];
2402 Double_t newY=fP[0]-vTrasl[1];
2403 Double_t newZ=fP[1]-vTrasl[2];
2405 //define the new parameters
2406 Double_t newParam[5];
2413 // recompute the covariance matrix:
2414 // 1. covV in the local system
2415 Double_t cosRot=TMath::Cos(fAlpha), sinRot=TMath::Sin(fAlpha);
2436 if(uUi.Determinant() <= 0.) {return kFALSE;}
2437 TMatrixD uUiQi(uUi,TMatrixD::kMult,qQi);
2438 TMatrixD m(qQi,TMatrixD::kTransposeMult,uUiQi);
2440 //2. compute the new covariance matrix of the track
2441 Double_t sigmaXX=m(0,0);
2442 Double_t sigmaXZ=m(2,0);
2443 Double_t sigmaXY=m(1,0);
2444 Double_t sigmaYY=GetSigmaY2()+m(1,1);
2445 Double_t sigmaYZ=fC[1]+m(1,2);
2446 Double_t sigmaZZ=fC[2]+m(2,2);
2447 Double_t covarianceYY=sigmaYY + (-1.)*((sigmaXY*sigmaXY)/sigmaXX);
2448 Double_t covarianceYZ=sigmaYZ-(sigmaXZ*sigmaXY/sigmaXX);
2449 Double_t covarianceZZ=sigmaZZ-((sigmaXZ*sigmaXZ)/sigmaXX);
2451 Double_t newCov[15];
2452 newCov[0]=covarianceYY;
2453 newCov[1]=covarianceYZ;
2454 newCov[2]=covarianceZZ;
2455 for(Int_t i=3;i<15;i++){
2459 // set the new parameters
2461 Set(newX,fAlpha,newParam,newCov);
2466 void AliExternalTrackParam::CheckCovariance() {
2468 // This function forces the diagonal elements of the covariance matrix to be positive.
2469 // In case the diagonal element is bigger than the maximal allowed value, it is set to
2470 // the limit and the off-diagonal elements that correspond to it are set to zero.
2472 fC[0] = TMath::Abs(fC[0]);
2474 double scl = TMath::Sqrt(kC0max/fC[0]);
2481 fC[2] = TMath::Abs(fC[2]);
2483 double scl = TMath::Sqrt(kC2max/fC[2]);
2490 fC[5] = TMath::Abs(fC[5]);
2492 double scl = TMath::Sqrt(kC5max/fC[5]);
2499 fC[9] = TMath::Abs(fC[9]);
2501 double scl = TMath::Sqrt(kC9max/fC[9]);
2508 fC[14] = TMath::Abs(fC[14]);
2509 if (fC[14]>kC14max) {
2510 double scl = TMath::Sqrt(kC14max/fC[14]);
2518 // The part below is used for tests and normally is commented out
2519 // TMatrixDSym m(5);
2523 // m(1,0)=fC[1]; m(1,1)=fC[2];
2524 // m(2,0)=fC[3]; m(2,1)=fC[4]; m(2,2)=fC[5];
2525 // m(3,0)=fC[6]; m(3,1)=fC[7]; m(3,2)=fC[8]; m(3,3)=fC[9];
2526 // m(4,0)=fC[10]; m(4,1)=fC[11]; m(4,2)=fC[12]; m(4,3)=fC[13]; m(4,4)=fC[14];
2529 // m(0,2)=m(2,0); m(1,2)=m(2,1);
2530 // m(0,3)=m(3,0); m(1,3)=m(3,1); m(2,3)=m(3,2);
2531 // m(0,4)=m(4,0); m(1,4)=m(4,1); m(2,4)=m(4,2); m(3,4)=m(4,3);
2532 // m.EigenVectors(eig);
2534 // // assert(eig(0)>=0 && eig(1)>=0 && eig(2)>=0 && eig(3)>=0 && eig(4)>=0);
2535 // if (!(eig(0)>=0 && eig(1)>=0 && eig(2)>=0 && eig(3)>=0 && eig(4)>=0)) {
2536 // AliWarning("Negative eigenvalues of the covariance matrix!");
2542 Bool_t AliExternalTrackParam::ConstrainToVertex(const AliVVertex* vtx, Double_t b[3])
2544 // Constrain TPC inner params constrained
2549 Double_t dz[2], cov[3];
2550 if (!PropagateToDCABxByBz(vtx, b, 3, dz, cov))
2554 vtx->GetCovarianceMatrix(covar);
2556 Double_t p[2]= { fP[0] - dz[0], fP[1] - dz[1] };
2557 Double_t c[3]= { covar[2], 0., covar[5] };
2559 Double_t chi2C = GetPredictedChi2(p,c);
2569 //___________________________________________________________________________________________
2570 Bool_t AliExternalTrackParam::GetXatLabR(Double_t r,Double_t &x, Double_t bz, Int_t dir) const
2572 // Get local X of the track position estimated at the radius lab radius r.
2573 // The track curvature is accounted exactly
2575 // The flag "dir" can be used to remove the ambiguity of which intersection to take (out of 2 possible)
2576 // 0 - take the intersection closest to the current track position
2577 // >0 - go along the track (increasing fX)
2578 // <0 - go backward (decreasing fX)
2580 const Double_t &fy=fP[0], &sn = fP[2];
2582 double crv = GetC(bz);
2583 if (TMath::Abs(crv)<=kAlmost0) { // this is a straight track
2584 if (TMath::Abs(sn)>=kAlmost1) { // || to Y axis
2585 double det = (r-fX)*(r+fX);
2586 if (det<0) return kFALSE; // does not reach raduis r
2588 if (dir==0) return kTRUE;
2589 det = TMath::Sqrt(det);
2590 if (dir>0) { // along the track direction
2591 if (sn>0) {if (fy>det) return kFALSE;} // track is along Y axis and above the circle
2592 else {if (fy<-det) return kFALSE;} // track is against Y axis amd belo the circle
2594 else { // agains track direction
2595 if (sn>0) {if (fy<-det) return kFALSE;} // track is along Y axis
2596 else if (fy>det) return kFALSE; // track is against Y axis
2599 else if (TMath::Abs(sn)<=kAlmost0) { // || to X axis
2600 double det = (r-fy)*(r+fy);
2601 if (det<0) return kFALSE; // does not reach raduis r
2602 det = TMath::Sqrt(det);
2604 x = fX>0 ? det : -det; // choose the solution requiring the smalest step
2607 else if (dir>0) { // along the track direction
2608 if (fX > det) return kFALSE; // current point is in on the right from the circle
2609 else if (fX <-det) x = -det; // on the left
2610 else x = det; // within the circle
2612 else { // against the track direction
2613 if (fX <-det) return kFALSE;
2614 else if (fX > det) x = det;
2618 else { // general case of straight line
2619 double cs = TMath::Sqrt((1-sn)*(1+sn));
2620 double xsyc = fX*sn-fy*cs;
2621 double det = (r-xsyc)*(r+xsyc);
2622 if (det<0) return kFALSE; // does not reach raduis r
2623 det = TMath::Sqrt(det);
2624 double xcys = fX*cs+fy*sn;
2626 if (dir==0) t += t>0 ? -det:det; // chose the solution requiring the smalest step
2627 else if (dir>0) { // go in increasing fX direction. ( t+-det > 0)
2628 if (t>=-det) t += -det; // take minimal step giving t>0
2629 else return kFALSE; // both solutions have negative t
2631 else { // go in increasing fX direction. (t+-det < 0)
2632 if (t<det) t -= det; // take minimal step giving t<0
2633 else return kFALSE; // both solutions have positive t
2639 // get center of the track circle
2640 double tR = 1./crv; // track radius (for the moment signed)
2641 double cs = TMath::Sqrt((1-sn)*(1+sn));
2642 double x0 = fX - sn*tR;
2643 double y0 = fy + cs*tR;
2644 double r0 = TMath::Sqrt(x0*x0+y0*y0);
2645 // printf("Xc:%+e Yc:%+e\n",x0,y0);
2647 if (r0<=kAlmost0) return kFALSE; // the track is concentric to circle
2648 tR = TMath::Abs(tR);
2649 double tR2r0 = tR/r0;
2650 double g = 0.5*(r*r/(r0*tR) - tR2r0 - 1./tR2r0);
2651 double det = (1.-g)*(1.+g);
2652 if (det<0) return kFALSE; // does not reach raduis r
2653 det = TMath::Sqrt(det);
2655 // the intersection happens in 2 points: {x0+tR*C,y0+tR*S}
2656 // with C=f*c0+-|s0|*det and S=f*s0-+c0 sign(s0)*det
2657 // where s0 and c0 make direction for the circle center (=x0/r0 and y0/r0)
2659 double tmp = 1.+g*tR2r0;
2662 if (TMath::Abs(y0)>kAlmost0) { // when y0==0 the x,y is unique
2663 double dfx = tR2r0*TMath::Abs(y0)*det;
2664 double dfy = tR2r0*x0*TMath::Sign(det,y0);
2665 if (dir==0) { // chose the one which corresponds to smallest step
2666 double delta = (x-fX)*dfx-(y-fy)*dfy; // the choice of + in C will lead to smaller step if delta<0
2667 if (delta<0) x += dfx;
2670 else if (dir>0) { // along track direction: x must be > fX
2671 x -= dfx; // try the smallest step (dfx is positive)
2672 if (x<fX && (x+=dfx+dfx)<fX) return kFALSE;
2674 else { // backward: x must be < fX
2675 x += dfx; // try the smallest step (dfx is positive)
2676 if (x>fX && (x-=dfx+dfx)>fX) return kFALSE;
2679 else { // special case: track touching the circle just in 1 point
2680 if ( (dir>0&&x<fX) || (dir<0&&x>fX) ) return kFALSE;
2686 //_________________________________________________________
2687 Bool_t AliExternalTrackParam::GetXYZatR(Double_t xr,Double_t bz, Double_t *xyz, Double_t* alpSect) const
2689 // This method has 3 modes of behaviour
2690 // 1) xyz[3] array is provided but alpSect pointer is 0: calculate the position of track intersection
2691 // with circle of radius xr and fill it in xyz array
2692 // 2) alpSect pointer is provided: find alpha of the sector where the track reaches local coordinate xr
2693 // Note that in this case xr is NOT the radius but the local coordinate.
2694 // If the xyz array is provided, it will be filled by track lab coordinates at local X in this sector
2695 // 3) Neither alpSect nor xyz pointers are provided: just check if the track reaches radius xr
2698 double crv = GetC(bz);
2699 if ( (TMath::Abs(bz))<kAlmost0Field ) crv=0.;
2700 const double &fy = fP[0];
2701 const double &fz = fP[1];
2702 const double &sn = fP[2];
2703 const double &tgl = fP[3];
2705 // general circle parameterization:
2706 // x = (r0+tR)cos(phi0) - tR cos(t+phi0)
2707 // y = (r0+tR)sin(phi0) - tR sin(t+phi0)
2708 // where qb is the sign of the curvature, tR is the track's signed radius and r0
2709 // is the DCA of helix to origin
2711 double tR = 1./crv; // track radius signed
2712 double cs = TMath::Sqrt((1-sn)*(1+sn));
2713 double x0 = fX - sn*tR; // helix center coordinates
2714 double y0 = fy + cs*tR;
2715 double phi0 = TMath::ATan2(y0,x0); // angle of PCA wrt to the origin
2716 if (tR<0) phi0 += TMath::Pi();
2717 if (phi0 > TMath::Pi()) phi0 -= 2.*TMath::Pi();
2718 else if (phi0 <-TMath::Pi()) phi0 += 2.*TMath::Pi();
2719 double cs0 = TMath::Cos(phi0);
2720 double sn0 = TMath::Sin(phi0);
2721 double r0 = x0*cs0 + y0*sn0 - tR; // DCA to origin
2722 double r2R = 1.+r0/tR;
2725 if (r2R<kAlmost0) return kFALSE; // helix is centered at the origin, no specific intersection with other concetric circle
2726 if (!xyz && !alpSect) return kTRUE;
2727 double xr2R = xr/tR;
2728 double r2Ri = 1./r2R;
2729 // the intersection cos(t) = [1 + (r0/tR+1)^2 - (r0/tR)^2]/[2(1+r0/tR)]
2730 double cosT = 0.5*(r2R + (1-xr2R*xr2R)*r2Ri);
2731 if ( TMath::Abs(cosT)>kAlmost1 ) {
2732 // printf("Does not reach : %f %f\n",r0,tR);
2733 return kFALSE; // track does not reach the radius xr
2736 double t = TMath::ACos(cosT);
2738 // intersection point
2740 xyzi[0] = x0 - tR*TMath::Cos(t+phi0);
2741 xyzi[1] = y0 - tR*TMath::Sin(t+phi0);
2742 if (xyz) { // if postition is requested, then z is needed:
2743 double t0 = TMath::ATan2(cs,-sn) - phi0;
2744 double z0 = fz - t0*tR*tgl;
2745 xyzi[2] = z0 + tR*t*tgl;
2749 Local2GlobalPosition(xyzi,fAlpha);
2758 double &alp = *alpSect;
2759 // determine the sector of crossing
2760 double phiPos = TMath::Pi()+TMath::ATan2(-xyzi[1],-xyzi[0]);
2761 int sect = ((Int_t)(phiPos*TMath::RadToDeg()))/20;
2762 alp = TMath::DegToRad()*(20*sect+10);
2763 double x2r,f1,f2,r1,r2,dx,dy2dx,yloc=0, ylocMax = xr*TMath::Tan(TMath::Pi()/18); // min max Y within sector at given X
2766 Double_t ca=TMath::Cos(alp-fAlpha), sa=TMath::Sin(alp-fAlpha);
2767 if ((cs*ca+sn*sa)<0) {
2768 AliDebug(1,Form("Rotation to target sector impossible: local cos(phi) would become %.2f",cs*ca+sn*sa));
2773 if (TMath::Abs(f1) >= kAlmost1) {
2774 AliDebug(1,Form("Rotation to target sector impossible: local sin(phi) would become %.2f",f1));
2778 double tmpX = fX*ca + fy*sa;
2779 double tmpY = -fX*sa + fy*ca;
2781 // estimate Y at X=xr
2785 if (TMath::Abs(f2) >= kAlmost1) {
2786 AliDebug(1,Form("Propagation in target sector failed ! %.10e",f2));
2789 r1 = TMath::Sqrt((1.-f1)*(1.+f1));
2790 r2 = TMath::Sqrt((1.-f2)*(1.+f2));
2791 dy2dx = (f1+f2)/(r1+r2);
2792 yloc = tmpY + dx*dy2dx;
2793 if (yloc>ylocMax) {alp += 2*TMath::Pi()/18; sect++;}
2794 else if (yloc<-ylocMax) {alp -= 2*TMath::Pi()/18; sect--;}
2796 if (alp >= TMath::Pi()) alp -= 2*TMath::Pi();
2797 else if (alp < -TMath::Pi()) alp += 2*TMath::Pi();
2798 // if (sect>=18) sect = 0;
2799 // if (sect<=0) sect = 17;
2802 // if alpha was requested, then recalculate the position at intersection in sector
2806 if (TMath::Abs(x2r)<0.05) xyz[2] = fz + dx*(r2 + f2*dy2dx)*tgl;
2808 // for small dx/R the linear apporximation of the arc by the segment is OK,
2809 // but at large dx/R the error is very large and leads to incorrect Z propagation
2810 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
2811 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
2812 // Similarly, the rotation angle in linear in dx only for dx<<R
2813 double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
2814 double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
2815 xyz[2] = fz + rot/crv*tgl;
2817 Local2GlobalPosition(xyz,alp);