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 //______________________________________________________
920 Bool_t AliExternalTrackParam::RotateParamOnly(Double_t alpha)
922 // rotate to new frame, ignore covariance
923 if (TMath::Abs(fP[2]) >= kAlmost1) {
924 AliError(Form("Precondition is not satisfied: |sin(phi)|>1 ! %f",fP[2]));
928 if (alpha < -TMath::Pi()) alpha += 2*TMath::Pi();
929 else if (alpha >= TMath::Pi()) alpha -= 2*TMath::Pi();
935 Double_t ca=TMath::Cos(alpha-fAlpha), sa=TMath::Sin(alpha-fAlpha);
936 Double_t sf=fP2, cf=TMath::Sqrt((1.- fP2)*(1.+fP2)); // Improve precision
937 // RS: check if rotation does no invalidate track model (cos(local_phi)>=0, i.e. particle
938 // direction in local frame is along the X axis
939 if ((cf*ca+sf*sa)<0) {
940 AliDebug(1,Form("Rotation failed: local cos(phi) would become %.2f",cf*ca+sf*sa));
944 Double_t tmp=sf*ca - cf*sa;
946 if (TMath::Abs(tmp) >= kAlmost1) {
947 if (TMath::Abs(tmp) > 1.+ Double_t(FLT_EPSILON))
948 AliWarning(Form("Rotation failed ! %.10e",tmp));
958 Bool_t AliExternalTrackParam::Invert() {
959 //------------------------------------------------------------------
960 // Transform this track to the local coord. system rotated by 180 deg.
961 //------------------------------------------------------------------
963 fAlpha += TMath::Pi();
964 while (fAlpha < -TMath::Pi()) fAlpha += 2*TMath::Pi();
965 while (fAlpha >= TMath::Pi()) fAlpha -= 2*TMath::Pi();
972 fC[1] = -fC[1]; // since the fP1 and fP2 are not inverted, their covariances with others change sign
982 Bool_t AliExternalTrackParam::PropagateTo(Double_t xk, Double_t b) {
983 //----------------------------------------------------------------
984 // Propagate this track to the plane X=xk (cm) in the field "b" (kG)
985 //----------------------------------------------------------------
987 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
989 Double_t crv=GetC(b);
990 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
992 Double_t x2r = crv*dx;
993 Double_t f1=fP[2], f2=f1 + x2r;
994 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
995 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
996 if (TMath::Abs(fP[4])< kAlmost0) return kFALSE;
998 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
1001 &fC10=fC[1], &fC11=fC[2],
1002 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
1003 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
1004 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
1006 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
1007 if (TMath::Abs(r1)<kAlmost0) return kFALSE;
1008 if (TMath::Abs(r2)<kAlmost0) return kFALSE;
1011 double dy2dx = (f1+f2)/(r1+r2);
1014 if (TMath::Abs(x2r)<0.05) fP1 += dx*(r2 + f2*dy2dx)*fP3; // Many thanks to P.Hristov !
1016 // for small dx/R the linear apporximation of the arc by the segment is OK,
1017 // but at large dx/R the error is very large and leads to incorrect Z propagation
1018 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
1019 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
1020 // double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
1021 // double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
1022 // fP1 += rot/crv*fP3;
1024 double rot = TMath::ASin(r1*f2 - r2*f1); // more economic version from Yura.
1025 if (f1*f1+f2*f2>1 && f1*f2<0) { // special cases of large rotations or large abs angles
1026 if (f2>0) rot = TMath::Pi() - rot; //
1027 else rot = -TMath::Pi() - rot;
1034 Double_t f02= dx/(r1*r1*r1); Double_t cc=crv/fP4;
1035 Double_t f04=0.5*dx*dx/(r1*r1*r1); f04*=cc;
1036 Double_t f12= dx*fP3*f1/(r1*r1*r1);
1037 Double_t f14=0.5*dx*dx*fP3*f1/(r1*r1*r1); f14*=cc;
1038 Double_t f13= dx/r1;
1039 Double_t f24= dx; f24*=cc;
1041 Double_t rinv = 1./r1;
1042 Double_t r3inv = rinv*rinv*rinv;
1043 Double_t f24= x2r/fP4;
1044 Double_t f02= dx*r3inv;
1045 Double_t f04=0.5*f24*f02;
1046 Double_t f12= f02*fP3*f1;
1047 Double_t f14=0.5*f24*f02*fP3*f1;
1048 Double_t f13= dx*rinv;
1051 Double_t b00=f02*fC20 + f04*fC40, b01=f12*fC20 + f14*fC40 + f13*fC30;
1052 Double_t b02=f24*fC40;
1053 Double_t b10=f02*fC21 + f04*fC41, b11=f12*fC21 + f14*fC41 + f13*fC31;
1054 Double_t b12=f24*fC41;
1055 Double_t b20=f02*fC22 + f04*fC42, b21=f12*fC22 + f14*fC42 + f13*fC32;
1056 Double_t b22=f24*fC42;
1057 Double_t b40=f02*fC42 + f04*fC44, b41=f12*fC42 + f14*fC44 + f13*fC43;
1058 Double_t b42=f24*fC44;
1059 Double_t b30=f02*fC32 + f04*fC43, b31=f12*fC32 + f14*fC43 + f13*fC33;
1060 Double_t b32=f24*fC43;
1063 Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a02=f02*b22+f04*b42;
1064 Double_t a11=f12*b21+f14*b41+f13*b31,a12=f12*b22+f14*b42+f13*b32;
1065 Double_t a22=f24*b42;
1067 //F*C*Ft = C + (b + bt + a)
1068 fC00 += b00 + b00 + a00;
1069 fC10 += b10 + b01 + a01;
1070 fC20 += b20 + b02 + a02;
1073 fC11 += b11 + b11 + a11;
1074 fC21 += b21 + b12 + a12;
1077 fC22 += b22 + b22 + a22;
1086 Bool_t AliExternalTrackParam::PropagateParamOnlyTo(Double_t xk, Double_t b) {
1087 //----------------------------------------------------------------
1088 // Propagate this track to the plane X=xk (cm) in the field "b" (kG)
1089 // Only parameters are propagated, not the matrix. To be used for small
1090 // distances only (<mm, i.e. misalignment)
1091 //----------------------------------------------------------------
1093 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
1095 Double_t crv=GetC(b);
1096 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1098 Double_t x2r = crv*dx;
1099 Double_t f1=fP[2], f2=f1 + x2r;
1100 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1101 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1102 if (TMath::Abs(fP[4])< kAlmost0) return kFALSE;
1104 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
1105 if (TMath::Abs(r1)<kAlmost0) return kFALSE;
1106 if (TMath::Abs(r2)<kAlmost0) return kFALSE;
1109 double dy2dx = (f1+f2)/(r1+r2);
1112 if (TMath::Abs(x2r)<0.05) fP[1] += dx*(r2 + f2*dy2dx)*fP[3]; // Many thanks to P.Hristov !
1114 // for small dx/R the linear apporximation of the arc by the segment is OK,
1115 // but at large dx/R the error is very large and leads to incorrect Z propagation
1116 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
1117 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
1118 // double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
1119 // double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
1120 // fP1 += rot/crv*fP3;
1122 double rot = TMath::ASin(r1*f2 - r2*f1); // more economic version from Yura.
1123 if (f1*f1+f2*f2>1 && f1*f2<0) { // special cases of large rotations or large abs angles
1124 if (f2>0) rot = TMath::Pi() - rot; //
1125 else rot = -TMath::Pi() - rot;
1127 fP[1] += fP[3]/crv*rot;
1133 AliExternalTrackParam::Propagate(Double_t alpha, Double_t x, Double_t b) {
1134 //------------------------------------------------------------------
1135 // Transform this track to the local coord. system rotated
1136 // by angle "alpha" (rad) with respect to the global coord. system,
1137 // and propagate this track to the plane X=xk (cm) in the field "b" (kG)
1138 //------------------------------------------------------------------
1140 //Save the parameters
1143 Double_t ps[5], cs[15];
1144 for (Int_t i=0; i<5; i++) ps[i]=fP[i];
1145 for (Int_t i=0; i<15; i++) cs[i]=fC[i];
1148 if (PropagateTo(x,b)) return kTRUE;
1150 //Restore the parameters, if the operation failed
1153 for (Int_t i=0; i<5; i++) fP[i]=ps[i];
1154 for (Int_t i=0; i<15; i++) fC[i]=cs[i];
1158 Bool_t AliExternalTrackParam::PropagateBxByBz
1159 (Double_t alpha, Double_t x, Double_t b[3]) {
1160 //------------------------------------------------------------------
1161 // Transform this track to the local coord. system rotated
1162 // by angle "alpha" (rad) with respect to the global coord. system,
1163 // and propagate this track to the plane X=xk (cm),
1164 // taking into account all three components of the B field, "b[3]" (kG)
1165 //------------------------------------------------------------------
1167 //Save the parameters
1170 Double_t ps[5], cs[15];
1171 for (Int_t i=0; i<5; i++) ps[i]=fP[i];
1172 for (Int_t i=0; i<15; i++) cs[i]=fC[i];
1175 if (PropagateToBxByBz(x,b)) return kTRUE;
1177 //Restore the parameters, if the operation failed
1180 for (Int_t i=0; i<5; i++) fP[i]=ps[i];
1181 for (Int_t i=0; i<15; i++) fC[i]=cs[i];
1186 void AliExternalTrackParam::Propagate(Double_t len, Double_t x[3],
1187 Double_t p[3], Double_t bz) const {
1188 //+++++++++++++++++++++++++++++++++++++++++
1189 // Origin: K. Shileev (Kirill.Shileev@cern.ch)
1190 // Extrapolate track along simple helix in magnetic field
1191 // Arguments: len -distance alogn helix, [cm]
1192 // bz - mag field, [kGaus]
1193 // Returns: x and p contain extrapolated positon and momentum
1194 // The momentum returned for straight-line tracks is meaningless !
1195 //+++++++++++++++++++++++++++++++++++++++++
1198 if (OneOverPt() < kAlmost0 || TMath::Abs(bz) < kAlmost0Field || GetC(bz) < kAlmost0){ //straight-line tracks
1199 Double_t unit[3]; GetDirection(unit);
1204 p[0]=unit[0]/kAlmost0;
1205 p[1]=unit[1]/kAlmost0;
1206 p[2]=unit[2]/kAlmost0;
1210 Double_t a = -kB2C*bz*GetSign();
1211 Double_t rho = a/pp;
1212 x[0] += p[0]*TMath::Sin(rho*len)/a - p[1]*(1-TMath::Cos(rho*len))/a;
1213 x[1] += p[1]*TMath::Sin(rho*len)/a + p[0]*(1-TMath::Cos(rho*len))/a;
1214 x[2] += p[2]*len/pp;
1217 p[0] = p0 *TMath::Cos(rho*len) - p[1]*TMath::Sin(rho*len);
1218 p[1] = p[1]*TMath::Cos(rho*len) + p0 *TMath::Sin(rho*len);
1222 Bool_t AliExternalTrackParam::Intersect(Double_t pnt[3], Double_t norm[3],
1223 Double_t bz) const {
1224 //+++++++++++++++++++++++++++++++++++++++++
1225 // Origin: K. Shileev (Kirill.Shileev@cern.ch)
1226 // Finds point of intersection (if exists) of the helix with the plane.
1227 // Stores result in fX and fP.
1228 // Arguments: planePoint,planeNorm - the plane defined by any plane's point
1229 // and vector, normal to the plane
1230 // Returns: kTrue if helix intersects the plane, kFALSE otherwise.
1231 //+++++++++++++++++++++++++++++++++++++++++
1232 Double_t x0[3]; GetXYZ(x0); //get track position in MARS
1234 //estimates initial helix length up to plane
1236 (pnt[0]-x0[0])*norm[0] + (pnt[1]-x0[1])*norm[1] + (pnt[2]-x0[2])*norm[2];
1237 Double_t dist=99999,distPrev=dist;
1239 while(TMath::Abs(dist)>0.00001){
1240 //calculates helix at the distance s from x0 ALONG the helix
1241 Propagate(s,x,p,bz);
1243 //distance between current helix position and plane
1244 dist=(x[0]-pnt[0])*norm[0]+(x[1]-pnt[1])*norm[1]+(x[2]-pnt[2])*norm[2];
1246 if(TMath::Abs(dist) >= TMath::Abs(distPrev)) {return kFALSE;}
1250 //on exit pnt is intersection point,norm is track vector at that point,
1252 for (Int_t i=0; i<3; i++) {pnt[i]=x[i]; norm[i]=p[i];}
1257 AliExternalTrackParam::GetPredictedChi2(const Double_t p[2],const Double_t cov[3]) const {
1258 //----------------------------------------------------------------
1259 // Estimate the chi2 of the space point "p" with the cov. matrix "cov"
1260 //----------------------------------------------------------------
1261 Double_t sdd = fC[0] + cov[0];
1262 Double_t sdz = fC[1] + cov[1];
1263 Double_t szz = fC[2] + cov[2];
1264 Double_t det = sdd*szz - sdz*sdz;
1266 if (TMath::Abs(det) < kAlmost0) return kVeryBig;
1268 Double_t d = fP[0] - p[0];
1269 Double_t z = fP[1] - p[1];
1271 return (d*szz*d - 2*d*sdz*z + z*sdd*z)/det;
1274 Double_t AliExternalTrackParam::
1275 GetPredictedChi2(const Double_t p[3],const Double_t covyz[3],const Double_t covxyz[3]) const {
1276 //----------------------------------------------------------------
1277 // Estimate the chi2 of the 3D space point "p" and
1278 // the full covariance matrix "covyz" and "covxyz"
1280 // Cov(x,x) ... : covxyz[0]
1281 // Cov(y,x) ... : covxyz[1] covyz[0]
1282 // Cov(z,x) ... : covxyz[2] covyz[1] covyz[2]
1283 //----------------------------------------------------------------
1291 Double_t f=GetSnp();
1292 if (TMath::Abs(f) >= kAlmost1) return kVeryBig;
1293 Double_t r=TMath::Sqrt((1.-f)*(1.+f));
1294 Double_t a=f/r, b=GetTgl()/r;
1296 Double_t s2=333.*333.; //something reasonably big (cm^2)
1299 v(0,0)= s2; v(0,1)= a*s2; v(0,2)= b*s2;;
1300 v(1,0)=a*s2; v(1,1)=a*a*s2 + GetSigmaY2(); v(1,2)=a*b*s2 + GetSigmaZY();
1301 v(2,0)=b*s2; v(2,1)=a*b*s2 + GetSigmaZY(); v(2,2)=b*b*s2 + GetSigmaZ2();
1303 v(0,0)+=covxyz[0]; v(0,1)+=covxyz[1]; v(0,2)+=covxyz[2];
1304 v(1,0)+=covxyz[1]; v(1,1)+=covyz[0]; v(1,2)+=covyz[1];
1305 v(2,0)+=covxyz[2]; v(2,1)+=covyz[1]; v(2,2)+=covyz[2];
1308 if (!v.IsValid()) return kVeryBig;
1311 for (Int_t i = 0; i < 3; i++)
1312 for (Int_t j = 0; j < 3; j++) chi2 += res[i]*res[j]*v(i,j);
1317 Double_t AliExternalTrackParam::
1318 GetPredictedChi2(const AliExternalTrackParam *t) const {
1319 //----------------------------------------------------------------
1320 // Estimate the chi2 (5 dof) of this track with respect to the track
1321 // given by the argument.
1322 // The two tracks must be in the same reference system
1323 // and estimated at the same reference plane.
1324 //----------------------------------------------------------------
1326 if (TMath::Abs(t->GetAlpha()-GetAlpha()) > FLT_EPSILON) {
1327 AliError("The reference systems of the tracks differ !");
1330 if (TMath::Abs(t->GetX()-GetX()) > FLT_EPSILON) {
1331 AliError("The reference of the tracks planes differ !");
1336 c(0,0)=GetSigmaY2();
1337 c(1,0)=GetSigmaZY(); c(1,1)=GetSigmaZ2();
1338 c(2,0)=GetSigmaSnpY(); c(2,1)=GetSigmaSnpZ(); c(2,2)=GetSigmaSnp2();
1339 c(3,0)=GetSigmaTglY(); c(3,1)=GetSigmaTglZ(); c(3,2)=GetSigmaTglSnp(); c(3,3)=GetSigmaTgl2();
1340 c(4,0)=GetSigma1PtY(); c(4,1)=GetSigma1PtZ(); c(4,2)=GetSigma1PtSnp(); c(4,3)=GetSigma1PtTgl(); c(4,4)=GetSigma1Pt2();
1342 c(0,0)+=t->GetSigmaY2();
1343 c(1,0)+=t->GetSigmaZY(); c(1,1)+=t->GetSigmaZ2();
1344 c(2,0)+=t->GetSigmaSnpY();c(2,1)+=t->GetSigmaSnpZ();c(2,2)+=t->GetSigmaSnp2();
1345 c(3,0)+=t->GetSigmaTglY();c(3,1)+=t->GetSigmaTglZ();c(3,2)+=t->GetSigmaTglSnp();c(3,3)+=t->GetSigmaTgl2();
1346 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();
1348 c(0,2)=c(2,0); c(1,2)=c(2,1);
1349 c(0,3)=c(3,0); c(1,3)=c(3,1); c(2,3)=c(3,2);
1350 c(0,4)=c(4,0); c(1,4)=c(4,1); c(2,4)=c(4,2); c(3,4)=c(4,3);
1353 if (!c.IsValid()) return kVeryBig;
1359 GetSnp() - t->GetSnp(),
1360 GetTgl() - t->GetTgl(),
1361 GetSigned1Pt() - t->GetSigned1Pt()
1365 for (Int_t i = 0; i < 5; i++)
1366 for (Int_t j = 0; j < 5; j++) chi2 += res[i]*res[j]*c(i,j);
1371 Bool_t AliExternalTrackParam::
1372 PropagateTo(Double_t p[3],Double_t covyz[3],Double_t covxyz[3],Double_t bz) {
1373 //----------------------------------------------------------------
1374 // Propagate this track to the plane
1375 // the 3D space point "p" (with the covariance matrix "covyz" and "covxyz")
1377 // The magnetic field is "bz" (kG)
1379 // The track curvature and the change of the covariance matrix
1380 // of the track parameters are negleted !
1381 // (So the "step" should be small compared with 1/curvature)
1382 //----------------------------------------------------------------
1384 Double_t f=GetSnp();
1385 if (TMath::Abs(f) >= kAlmost1) return kFALSE;
1386 Double_t r=TMath::Sqrt((1.-f)*(1.+f));
1387 Double_t a=f/r, b=GetTgl()/r;
1389 Double_t s2=333.*333.; //something reasonably big (cm^2)
1392 tV(0,0)= s2; tV(0,1)= a*s2; tV(0,2)= b*s2;
1393 tV(1,0)=a*s2; tV(1,1)=a*a*s2; tV(1,2)=a*b*s2;
1394 tV(2,0)=b*s2; tV(2,1)=a*b*s2; tV(2,2)=b*b*s2;
1397 pV(0,0)=covxyz[0]; pV(0,1)=covxyz[1]; pV(0,2)=covxyz[2];
1398 pV(1,0)=covxyz[1]; pV(1,1)=covyz[0]; pV(1,2)=covyz[1];
1399 pV(2,0)=covxyz[2]; pV(2,1)=covyz[1]; pV(2,2)=covyz[2];
1401 TMatrixDSym tpV(tV);
1404 if (!tpV.IsValid()) return kFALSE;
1406 TMatrixDSym pW(3),tW(3);
1407 for (Int_t i=0; i<3; i++)
1408 for (Int_t j=0; j<3; j++) {
1410 for (Int_t k=0; k<3; k++) {
1411 pW(i,j) += tV(i,k)*tpV(k,j);
1412 tW(i,j) += pV(i,k)*tpV(k,j);
1416 Double_t t[3] = {GetX(), GetY(), GetZ()};
1419 for (Int_t i=0; i<3; i++) x += (tW(0,i)*t[i] + pW(0,i)*p[i]);
1420 Double_t crv=GetC(bz);
1421 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1423 if (TMath::Abs(f) >= kAlmost1) return kFALSE;
1427 for (Int_t i=0; i<3; i++) fP[0] += (tW(1,i)*t[i] + pW(1,i)*p[i]);
1429 for (Int_t i=0; i<3; i++) fP[1] += (tW(2,i)*t[i] + pW(2,i)*p[i]);
1434 Double_t *AliExternalTrackParam::GetResiduals(
1435 Double_t *p,Double_t *cov,Bool_t updated) const {
1436 //------------------------------------------------------------------
1437 // Returns the track residuals with the space point "p" having
1438 // the covariance matrix "cov".
1439 // If "updated" is kTRUE, the track parameters expected to be updated,
1440 // otherwise they must be predicted.
1441 //------------------------------------------------------------------
1442 static Double_t res[2];
1444 Double_t r00=cov[0], r01=cov[1], r11=cov[2];
1446 r00-=fC[0]; r01-=fC[1]; r11-=fC[2];
1448 r00+=fC[0]; r01+=fC[1]; r11+=fC[2];
1450 Double_t det=r00*r11 - r01*r01;
1452 if (TMath::Abs(det) < kAlmost0) return 0;
1454 Double_t tmp=r00; r00=r11/det; r11=tmp/det;
1456 if (r00 < 0.) return 0;
1457 if (r11 < 0.) return 0;
1459 Double_t dy = fP[0] - p[0];
1460 Double_t dz = fP[1] - p[1];
1462 res[0]=dy*TMath::Sqrt(r00);
1463 res[1]=dz*TMath::Sqrt(r11);
1468 Bool_t AliExternalTrackParam::Update(const Double_t p[2], const Double_t cov[3]) {
1469 //------------------------------------------------------------------
1470 // Update the track parameters with the space point "p" having
1471 // the covariance matrix "cov"
1472 //------------------------------------------------------------------
1473 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
1476 &fC10=fC[1], &fC11=fC[2],
1477 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
1478 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
1479 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
1481 Double_t r00=cov[0], r01=cov[1], r11=cov[2];
1482 r00+=fC00; r01+=fC10; r11+=fC11;
1483 Double_t det=r00*r11 - r01*r01;
1485 if (TMath::Abs(det) < kAlmost0) return kFALSE;
1488 Double_t tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;
1490 Double_t k00=fC00*r00+fC10*r01, k01=fC00*r01+fC10*r11;
1491 Double_t k10=fC10*r00+fC11*r01, k11=fC10*r01+fC11*r11;
1492 Double_t k20=fC20*r00+fC21*r01, k21=fC20*r01+fC21*r11;
1493 Double_t k30=fC30*r00+fC31*r01, k31=fC30*r01+fC31*r11;
1494 Double_t k40=fC40*r00+fC41*r01, k41=fC40*r01+fC41*r11;
1496 Double_t dy=p[0] - fP0, dz=p[1] - fP1;
1497 Double_t sf=fP2 + k20*dy + k21*dz;
1498 if (TMath::Abs(sf) > kAlmost1) return kFALSE;
1500 fP0 += k00*dy + k01*dz;
1501 fP1 += k10*dy + k11*dz;
1503 fP3 += k30*dy + k31*dz;
1504 fP4 += k40*dy + k41*dz;
1506 Double_t c01=fC10, c02=fC20, c03=fC30, c04=fC40;
1507 Double_t c12=fC21, c13=fC31, c14=fC41;
1509 fC00-=k00*fC00+k01*fC10; fC10-=k00*c01+k01*fC11;
1510 fC20-=k00*c02+k01*c12; fC30-=k00*c03+k01*c13;
1511 fC40-=k00*c04+k01*c14;
1513 fC11-=k10*c01+k11*fC11;
1514 fC21-=k10*c02+k11*c12; fC31-=k10*c03+k11*c13;
1515 fC41-=k10*c04+k11*c14;
1517 fC22-=k20*c02+k21*c12; fC32-=k20*c03+k21*c13;
1518 fC42-=k20*c04+k21*c14;
1520 fC33-=k30*c03+k31*c13;
1521 fC43-=k30*c04+k31*c14;
1523 fC44-=k40*c04+k41*c14;
1531 AliExternalTrackParam::GetHelixParameters(Double_t hlx[6], Double_t b) const {
1532 //--------------------------------------------------------------------
1533 // External track parameters -> helix parameters
1534 // "b" - magnetic field (kG)
1535 //--------------------------------------------------------------------
1536 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1538 hlx[0]=fP[0]; hlx[1]=fP[1]; hlx[2]=fP[2]; hlx[3]=fP[3];
1540 hlx[5]=fX*cs - hlx[0]*sn; // x0
1541 hlx[0]=fX*sn + hlx[0]*cs; // y0
1543 hlx[2]=TMath::ASin(hlx[2]) + fAlpha; // phi0
1545 hlx[4]=GetC(b); // C
1549 static void Evaluate(const Double_t *h, Double_t t,
1550 Double_t r[3], //radius vector
1551 Double_t g[3], //first defivatives
1552 Double_t gg[3]) //second derivatives
1554 //--------------------------------------------------------------------
1555 // Calculate position of a point on a track and some derivatives
1556 //--------------------------------------------------------------------
1557 Double_t phase=h[4]*t+h[2];
1558 Double_t sn=TMath::Sin(phase), cs=TMath::Cos(phase);
1562 if (TMath::Abs(h[4])>kAlmost0) {
1563 r[0] += (sn - h[6])/h[4];
1564 r[1] -= (cs - h[7])/h[4];
1566 r[2] = h[1] + h[3]*t;
1568 g[0] = cs; g[1]=sn; g[2]=h[3];
1570 gg[0]=-h[4]*sn; gg[1]=h[4]*cs; gg[2]=0.;
1573 Double_t AliExternalTrackParam::GetDCA(const AliExternalTrackParam *p,
1574 Double_t b, Double_t &xthis, Double_t &xp) const {
1575 //------------------------------------------------------------
1576 // Returns the (weighed !) distance of closest approach between
1577 // this track and the track "p".
1578 // Other returned values:
1579 // xthis, xt - coordinates of tracks' reference planes at the DCA
1580 //-----------------------------------------------------------
1581 Double_t dy2=GetSigmaY2() + p->GetSigmaY2();
1582 Double_t dz2=GetSigmaZ2() + p->GetSigmaZ2();
1585 Double_t p1[8]; GetHelixParameters(p1,b);
1586 p1[6]=TMath::Sin(p1[2]); p1[7]=TMath::Cos(p1[2]);
1587 Double_t p2[8]; p->GetHelixParameters(p2,b);
1588 p2[6]=TMath::Sin(p2[2]); p2[7]=TMath::Cos(p2[2]);
1591 Double_t r1[3],g1[3],gg1[3]; Double_t t1=0.;
1592 Evaluate(p1,t1,r1,g1,gg1);
1593 Double_t r2[3],g2[3],gg2[3]; Double_t t2=0.;
1594 Evaluate(p2,t2,r2,g2,gg2);
1596 Double_t dx=r2[0]-r1[0], dy=r2[1]-r1[1], dz=r2[2]-r1[2];
1597 Double_t dm=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
1601 Double_t gt1=-(dx*g1[0]/dx2 + dy*g1[1]/dy2 + dz*g1[2]/dz2);
1602 Double_t gt2=+(dx*g2[0]/dx2 + dy*g2[1]/dy2 + dz*g2[2]/dz2);
1603 Double_t h11=(g1[0]*g1[0] - dx*gg1[0])/dx2 +
1604 (g1[1]*g1[1] - dy*gg1[1])/dy2 +
1605 (g1[2]*g1[2] - dz*gg1[2])/dz2;
1606 Double_t h22=(g2[0]*g2[0] + dx*gg2[0])/dx2 +
1607 (g2[1]*g2[1] + dy*gg2[1])/dy2 +
1608 (g2[2]*g2[2] + dz*gg2[2])/dz2;
1609 Double_t h12=-(g1[0]*g2[0]/dx2 + g1[1]*g2[1]/dy2 + g1[2]*g2[2]/dz2);
1611 Double_t det=h11*h22-h12*h12;
1614 if (TMath::Abs(det)<1.e-33) {
1615 //(quasi)singular Hessian
1618 dt1=-(gt1*h22 - gt2*h12)/det;
1619 dt2=-(h11*gt2 - h12*gt1)/det;
1622 if ((dt1*gt1+dt2*gt2)>0) {dt1=-dt1; dt2=-dt2;}
1624 //check delta(phase1) ?
1625 //check delta(phase2) ?
1627 if (TMath::Abs(dt1)/(TMath::Abs(t1)+1.e-3) < 1.e-4)
1628 if (TMath::Abs(dt2)/(TMath::Abs(t2)+1.e-3) < 1.e-4) {
1629 if ((gt1*gt1+gt2*gt2) > 1.e-4/dy2/dy2)
1630 AliDebug(1," stopped at not a stationary point !");
1631 Double_t lmb=h11+h22; lmb=lmb-TMath::Sqrt(lmb*lmb-4*det);
1633 AliDebug(1," stopped at not a minimum !");
1638 for (Int_t div=1 ; ; div*=2) {
1639 Evaluate(p1,t1+dt1,r1,g1,gg1);
1640 Evaluate(p2,t2+dt2,r2,g2,gg2);
1641 dx=r2[0]-r1[0]; dy=r2[1]-r1[1]; dz=r2[2]-r1[2];
1642 dd=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
1646 AliDebug(1," overshoot !"); break;
1656 if (max<=0) AliDebug(1," too many iterations !");
1658 Double_t cs=TMath::Cos(GetAlpha());
1659 Double_t sn=TMath::Sin(GetAlpha());
1660 xthis=r1[0]*cs + r1[1]*sn;
1662 cs=TMath::Cos(p->GetAlpha());
1663 sn=TMath::Sin(p->GetAlpha());
1664 xp=r2[0]*cs + r2[1]*sn;
1666 return TMath::Sqrt(dm*TMath::Sqrt(dy2*dz2));
1669 Double_t AliExternalTrackParam::
1670 PropagateToDCA(AliExternalTrackParam *p, Double_t b) {
1671 //--------------------------------------------------------------
1672 // Propagates this track and the argument track to the position of the
1673 // distance of closest approach.
1674 // Returns the (weighed !) distance of closest approach.
1675 //--------------------------------------------------------------
1677 Double_t dca=GetDCA(p,b,xthis,xp);
1679 if (!PropagateTo(xthis,b)) {
1680 //AliWarning(" propagation failed !");
1684 if (!p->PropagateTo(xp,b)) {
1685 //AliWarning(" propagation failed !";
1693 Bool_t AliExternalTrackParam::PropagateToDCA(const AliVVertex *vtx,
1694 Double_t b, Double_t maxd, Double_t dz[2], Double_t covar[3]) {
1696 // Propagate this track to the DCA to vertex "vtx",
1697 // if the (rough) transverse impact parameter is not bigger then "maxd".
1698 // Magnetic field is "b" (kG).
1700 // a) The track gets extapolated to the DCA to the vertex.
1701 // b) The impact parameters and their covariance matrix are calculated.
1703 // In the case of success, the returned value is kTRUE
1704 // (otherwise, it's kFALSE)
1706 Double_t alpha=GetAlpha();
1707 Double_t sn=TMath::Sin(alpha), cs=TMath::Cos(alpha);
1708 Double_t x=GetX(), y=GetParameter()[0], snp=GetParameter()[2];
1709 Double_t xv= vtx->GetX()*cs + vtx->GetY()*sn;
1710 Double_t yv=-vtx->GetX()*sn + vtx->GetY()*cs, zv=vtx->GetZ();
1713 //Estimate the impact parameter neglecting the track curvature
1714 Double_t d=TMath::Abs(x*snp - y*TMath::Sqrt((1.-snp)*(1.+snp)));
1715 if (d > maxd) return kFALSE;
1717 //Propagate to the DCA
1718 Double_t crv=GetC(b);
1719 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1721 Double_t tgfv=-(crv*x - snp)/(crv*y + TMath::Sqrt((1.-snp)*(1.+snp)));
1722 sn=tgfv/TMath::Sqrt(1.+ tgfv*tgfv); cs=TMath::Sqrt((1.-sn)*(1.+sn));
1723 if (TMath::Abs(tgfv)>0.) cs = sn/tgfv;
1727 yv=-xv*sn + yv*cs; xv=x;
1729 if (!Propagate(alpha+TMath::ASin(sn),xv,b)) return kFALSE;
1731 if (dz==0) return kTRUE;
1732 dz[0] = GetParameter()[0] - yv;
1733 dz[1] = GetParameter()[1] - zv;
1735 if (covar==0) return kTRUE;
1736 Double_t cov[6]; vtx->GetCovarianceMatrix(cov);
1738 //***** Improvements by A.Dainese
1739 alpha=GetAlpha(); sn=TMath::Sin(alpha); cs=TMath::Cos(alpha);
1740 Double_t s2ylocvtx = cov[0]*sn*sn + cov[2]*cs*cs - 2.*cov[1]*cs*sn;
1741 covar[0] = GetCovariance()[0] + s2ylocvtx; // neglecting correlations
1742 covar[1] = GetCovariance()[1]; // between (x,y) and z
1743 covar[2] = GetCovariance()[2] + cov[5]; // in vertex's covariance matrix
1749 Bool_t AliExternalTrackParam::PropagateToDCABxByBz(const AliVVertex *vtx,
1750 Double_t b[3], Double_t maxd, Double_t dz[2], Double_t covar[3]) {
1752 // Propagate this track to the DCA to vertex "vtx",
1753 // if the (rough) transverse impact parameter is not bigger then "maxd".
1755 // This function takes into account all three components of the magnetic
1756 // field given by the b[3] arument (kG)
1758 // a) The track gets extapolated to the DCA to the vertex.
1759 // b) The impact parameters and their covariance matrix are calculated.
1761 // In the case of success, the returned value is kTRUE
1762 // (otherwise, it's kFALSE)
1764 Double_t alpha=GetAlpha();
1765 Double_t sn=TMath::Sin(alpha), cs=TMath::Cos(alpha);
1766 Double_t x=GetX(), y=GetParameter()[0], snp=GetParameter()[2];
1767 Double_t xv= vtx->GetX()*cs + vtx->GetY()*sn;
1768 Double_t yv=-vtx->GetX()*sn + vtx->GetY()*cs, zv=vtx->GetZ();
1771 //Estimate the impact parameter neglecting the track curvature
1772 Double_t d=TMath::Abs(x*snp - y*TMath::Sqrt((1.-snp)*(1.+snp)));
1773 if (d > maxd) return kFALSE;
1775 //Propagate to the DCA
1776 Double_t crv=GetC(b[2]);
1777 if (TMath::Abs(b[2]) < kAlmost0Field) crv=0.;
1779 Double_t tgfv=-(crv*x - snp)/(crv*y + TMath::Sqrt((1.-snp)*(1.+snp)));
1780 sn=tgfv/TMath::Sqrt(1.+ tgfv*tgfv); cs=TMath::Sqrt((1.-sn)*(1.+sn));
1781 if (TMath::Abs(tgfv)>0.) cs = sn/tgfv;
1785 yv=-xv*sn + yv*cs; xv=x;
1787 if (!PropagateBxByBz(alpha+TMath::ASin(sn),xv,b)) return kFALSE;
1789 if (dz==0) return kTRUE;
1790 dz[0] = GetParameter()[0] - yv;
1791 dz[1] = GetParameter()[1] - zv;
1793 if (covar==0) return kTRUE;
1794 Double_t cov[6]; vtx->GetCovarianceMatrix(cov);
1796 //***** Improvements by A.Dainese
1797 alpha=GetAlpha(); sn=TMath::Sin(alpha); cs=TMath::Cos(alpha);
1798 Double_t s2ylocvtx = cov[0]*sn*sn + cov[2]*cs*cs - 2.*cov[1]*cs*sn;
1799 covar[0] = GetCovariance()[0] + s2ylocvtx; // neglecting correlations
1800 covar[1] = GetCovariance()[1]; // between (x,y) and z
1801 covar[2] = GetCovariance()[2] + cov[5]; // in vertex's covariance matrix
1807 void AliExternalTrackParam::GetDirection(Double_t d[3]) const {
1808 //----------------------------------------------------------------
1809 // This function returns a unit vector along the track direction
1810 // in the global coordinate system.
1811 //----------------------------------------------------------------
1812 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1814 Double_t csp =TMath::Sqrt((1.-snp)*(1.+snp));
1815 Double_t norm=TMath::Sqrt(1.+ fP[3]*fP[3]);
1816 d[0]=(csp*cs - snp*sn)/norm;
1817 d[1]=(snp*cs + csp*sn)/norm;
1821 Bool_t AliExternalTrackParam::GetPxPyPz(Double_t p[3]) const {
1822 //---------------------------------------------------------------------
1823 // This function returns the global track momentum components
1824 // Results for (nearly) straight tracks are meaningless !
1825 //---------------------------------------------------------------------
1826 p[0]=fP[4]; p[1]=fP[2]; p[2]=fP[3];
1827 return Local2GlobalMomentum(p,fAlpha);
1830 Double_t AliExternalTrackParam::Px() const {
1831 //---------------------------------------------------------------------
1832 // Returns x-component of momentum
1833 // Result for (nearly) straight tracks is meaningless !
1834 //---------------------------------------------------------------------
1836 Double_t p[3]={kVeryBig,kVeryBig,kVeryBig};
1842 Double_t AliExternalTrackParam::Py() const {
1843 //---------------------------------------------------------------------
1844 // Returns y-component of momentum
1845 // Result for (nearly) straight tracks is meaningless !
1846 //---------------------------------------------------------------------
1848 Double_t p[3]={kVeryBig,kVeryBig,kVeryBig};
1854 Double_t AliExternalTrackParam::Xv() const {
1855 //---------------------------------------------------------------------
1856 // Returns x-component of first track point
1857 //---------------------------------------------------------------------
1859 Double_t r[3]={0.,0.,0.};
1865 Double_t AliExternalTrackParam::Yv() const {
1866 //---------------------------------------------------------------------
1867 // Returns y-component of first track point
1868 //---------------------------------------------------------------------
1870 Double_t r[3]={0.,0.,0.};
1876 Double_t AliExternalTrackParam::Theta() const {
1877 // return theta angle of momentum
1879 return 0.5*TMath::Pi() - TMath::ATan(fP[3]);
1882 Double_t AliExternalTrackParam::Phi() const {
1883 //---------------------------------------------------------------------
1884 // Returns the azimuthal angle of momentum
1886 //---------------------------------------------------------------------
1888 Double_t phi=TMath::ASin(fP[2]) + fAlpha;
1889 if (phi<0.) phi+=2.*TMath::Pi();
1890 else if (phi>=2.*TMath::Pi()) phi-=2.*TMath::Pi();
1895 Double_t AliExternalTrackParam::PhiPos() const {
1896 //---------------------------------------------------------------------
1897 // Returns the azimuthal angle of position
1899 //---------------------------------------------------------------------
1900 Double_t r[3]={0.,0.,0.};
1902 Double_t phi=TMath::ATan2(r[1],r[0]);
1903 if (phi<0.) phi+=2.*TMath::Pi();
1908 Double_t AliExternalTrackParam::M() const {
1909 // return particle mass
1911 // No mass information available so far.
1912 // Redifine in derived class!
1917 Double_t AliExternalTrackParam::E() const {
1918 // return particle energy
1920 // No PID information available so far.
1921 // Redifine in derived class!
1926 Double_t AliExternalTrackParam::Eta() const {
1927 // return pseudorapidity
1929 return -TMath::Log(TMath::Tan(0.5 * Theta()));
1932 Double_t AliExternalTrackParam::Y() const {
1935 // No PID information available so far.
1936 // Redifine in derived class!
1941 Bool_t AliExternalTrackParam::GetXYZ(Double_t *r) const {
1942 //---------------------------------------------------------------------
1943 // This function returns the global track position
1944 //---------------------------------------------------------------------
1945 r[0]=fX; r[1]=fP[0]; r[2]=fP[1];
1946 return Local2GlobalPosition(r,fAlpha);
1949 Bool_t AliExternalTrackParam::GetCovarianceXYZPxPyPz(Double_t cv[21]) const {
1950 //---------------------------------------------------------------------
1951 // This function returns the global covariance matrix of the track params
1953 // Cov(x,x) ... : cv[0]
1954 // Cov(y,x) ... : cv[1] cv[2]
1955 // Cov(z,x) ... : cv[3] cv[4] cv[5]
1956 // Cov(px,x)... : cv[6] cv[7] cv[8] cv[9]
1957 // Cov(py,x)... : cv[10] cv[11] cv[12] cv[13] cv[14]
1958 // Cov(pz,x)... : cv[15] cv[16] cv[17] cv[18] cv[19] cv[20]
1960 // Results for (nearly) straight tracks are meaningless !
1961 //---------------------------------------------------------------------
1962 if (TMath::Abs(fP[4])<=kAlmost0) {
1963 for (Int_t i=0; i<21; i++) cv[i]=0.;
1966 if (TMath::Abs(fP[2]) > kAlmost1) {
1967 for (Int_t i=0; i<21; i++) cv[i]=0.;
1970 Double_t pt=1./TMath::Abs(fP[4]);
1971 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1972 Double_t r=TMath::Sqrt((1.-fP[2])*(1.+fP[2]));
1974 Double_t m00=-sn, m10=cs;
1975 Double_t m23=-pt*(sn + fP[2]*cs/r), m43=-pt*pt*(r*cs - fP[2]*sn);
1976 Double_t m24= pt*(cs - fP[2]*sn/r), m44=-pt*pt*(r*sn + fP[2]*cs);
1977 Double_t m35=pt, m45=-pt*pt*fP[3];
1983 cv[0 ] = fC[0]*m00*m00;
1984 cv[1 ] = fC[0]*m00*m10;
1985 cv[2 ] = fC[0]*m10*m10;
1989 cv[6 ] = m00*(fC[3]*m23 + fC[10]*m43);
1990 cv[7 ] = m10*(fC[3]*m23 + fC[10]*m43);
1991 cv[8 ] = fC[4]*m23 + fC[11]*m43;
1992 cv[9 ] = m23*(fC[5]*m23 + fC[12]*m43) + m43*(fC[12]*m23 + fC[14]*m43);
1993 cv[10] = m00*(fC[3]*m24 + fC[10]*m44);
1994 cv[11] = m10*(fC[3]*m24 + fC[10]*m44);
1995 cv[12] = fC[4]*m24 + fC[11]*m44;
1996 cv[13] = m23*(fC[5]*m24 + fC[12]*m44) + m43*(fC[12]*m24 + fC[14]*m44);
1997 cv[14] = m24*(fC[5]*m24 + fC[12]*m44) + m44*(fC[12]*m24 + fC[14]*m44);
1998 cv[15] = m00*(fC[6]*m35 + fC[10]*m45);
1999 cv[16] = m10*(fC[6]*m35 + fC[10]*m45);
2000 cv[17] = fC[7]*m35 + fC[11]*m45;
2001 cv[18] = m23*(fC[8]*m35 + fC[12]*m45) + m43*(fC[13]*m35 + fC[14]*m45);
2002 cv[19] = m24*(fC[8]*m35 + fC[12]*m45) + m44*(fC[13]*m35 + fC[14]*m45);
2003 cv[20] = m35*(fC[9]*m35 + fC[13]*m45) + m45*(fC[13]*m35 + fC[14]*m45);
2010 AliExternalTrackParam::GetPxPyPzAt(Double_t x, Double_t b, Double_t *p) const {
2011 //---------------------------------------------------------------------
2012 // This function returns the global track momentum extrapolated to
2013 // the radial position "x" (cm) in the magnetic field "b" (kG)
2014 //---------------------------------------------------------------------
2016 p[1]=fP[2]+(x-fX)*GetC(b);
2018 return Local2GlobalMomentum(p,fAlpha);
2022 AliExternalTrackParam::GetYAt(Double_t x, Double_t b, Double_t &y) const {
2023 //---------------------------------------------------------------------
2024 // This function returns the local Y-coordinate of the intersection
2025 // point between this track and the reference plane "x" (cm).
2026 // Magnetic field "b" (kG)
2027 //---------------------------------------------------------------------
2029 if(TMath::Abs(dx)<=kAlmost0) {y=fP[0]; return kTRUE;}
2031 Double_t f1=fP[2], f2=f1 + dx*GetC(b);
2033 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
2034 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
2036 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
2037 y = fP[0] + dx*(f1+f2)/(r1+r2);
2042 AliExternalTrackParam::GetZAt(Double_t x, Double_t b, Double_t &z) const {
2043 //---------------------------------------------------------------------
2044 // This function returns the local Z-coordinate of the intersection
2045 // point between this track and the reference plane "x" (cm).
2046 // Magnetic field "b" (kG)
2047 //---------------------------------------------------------------------
2049 if(TMath::Abs(dx)<=kAlmost0) {z=fP[1]; return kTRUE;}
2051 Double_t crv=GetC(b);
2052 Double_t x2r = crv*dx;
2053 Double_t f1=fP[2], f2=f1 + x2r;
2055 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
2056 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
2058 Double_t r1=sqrt((1.-f1)*(1.+f1)), r2=sqrt((1.-f2)*(1.+f2));
2059 double dy2dx = (f1+f2)/(r1+r2);
2060 if (TMath::Abs(x2r)<0.05) {
2061 z = fP[1] + dx*(r2 + f2*dy2dx)*fP[3]; // Many thanks to P.Hristov !
2064 // for small dx/R the linear apporximation of the arc by the segment is OK,
2065 // but at large dx/R the error is very large and leads to incorrect Z propagation
2066 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
2067 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
2068 // Similarly, the rotation angle in linear in dx only for dx<<R
2069 double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
2070 double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
2071 z = fP[1] + rot/crv*fP[3];
2077 AliExternalTrackParam::GetXYZAt(Double_t x, Double_t b, Double_t *r) const {
2078 //---------------------------------------------------------------------
2079 // This function returns the global track position extrapolated to
2080 // the radial position "x" (cm) in the magnetic field "b" (kG)
2081 //---------------------------------------------------------------------
2083 if(TMath::Abs(dx)<=kAlmost0) return GetXYZ(r);
2085 Double_t crv=GetC(b);
2086 Double_t x2r = crv*dx;
2087 Double_t f1=fP[2], f2=f1 + dx*crv;
2089 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
2090 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
2092 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
2093 double dy2dx = (f1+f2)/(r1+r2);
2095 r[1] = fP[0] + dx*dy2dx;
2096 if (TMath::Abs(x2r)<0.05) {
2097 r[2] = fP[1] + dx*(r2 + f2*dy2dx)*fP[3];//Thanks to Andrea & Peter
2100 // for small dx/R the linear apporximation of the arc by the segment is OK,
2101 // but at large dx/R the error is very large and leads to incorrect Z propagation
2102 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
2103 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
2104 // Similarly, the rotation angle in linear in dx only for dx<<R
2105 double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
2106 double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
2107 r[2] = fP[1] + rot/crv*fP[3];
2110 return Local2GlobalPosition(r,fAlpha);
2113 //_____________________________________________________________________________
2114 void AliExternalTrackParam::Print(Option_t* /*option*/) const
2116 // print the parameters and the covariance matrix
2118 printf("AliExternalTrackParam: x = %-12g alpha = %-12g\n", fX, fAlpha);
2119 printf(" parameters: %12g %12g %12g %12g %12g\n",
2120 fP[0], fP[1], fP[2], fP[3], fP[4]);
2121 printf(" covariance: %12g\n", fC[0]);
2122 printf(" %12g %12g\n", fC[1], fC[2]);
2123 printf(" %12g %12g %12g\n", fC[3], fC[4], fC[5]);
2124 printf(" %12g %12g %12g %12g\n",
2125 fC[6], fC[7], fC[8], fC[9]);
2126 printf(" %12g %12g %12g %12g %12g\n",
2127 fC[10], fC[11], fC[12], fC[13], fC[14]);
2130 Double_t AliExternalTrackParam::GetSnpAt(Double_t x,Double_t b) const {
2132 // Get sinus at given x
2134 Double_t crv=GetC(b);
2135 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
2137 Double_t res = fP[2]+dx*crv;
2141 Bool_t AliExternalTrackParam::GetDistance(AliExternalTrackParam *param2, Double_t x, Double_t dist[3], Double_t bz){
2142 //------------------------------------------------------------------------
2143 // Get the distance between two tracks at the local position x
2144 // working in the local frame of this track.
2145 // Origin : Marian.Ivanov@cern.ch
2146 //-----------------------------------------------------------------------
2150 if (!GetYAt(x,bz,xyz[1])) return kFALSE;
2151 if (!GetZAt(x,bz,xyz[2])) return kFALSE;
2154 if (TMath::Abs(GetAlpha()-param2->GetAlpha())<kAlmost0){
2156 if (!param2->GetYAt(x,bz,xyz2[1])) return kFALSE;
2157 if (!param2->GetZAt(x,bz,xyz2[2])) return kFALSE;
2161 Double_t dfi = param2->GetAlpha()-GetAlpha();
2162 Double_t ca = TMath::Cos(dfi), sa = TMath::Sin(dfi);
2163 xyz2[0] = xyz[0]*ca+xyz[1]*sa;
2164 xyz2[1] = -xyz[0]*sa+xyz[1]*ca;
2167 if (!param2->GetYAt(xyz2[0],bz,xyz1[1])) return kFALSE;
2168 if (!param2->GetZAt(xyz2[0],bz,xyz1[2])) return kFALSE;
2170 xyz2[0] = xyz1[0]*ca-xyz1[1]*sa;
2171 xyz2[1] = +xyz1[0]*sa+xyz1[1]*ca;
2174 dist[0] = xyz[0]-xyz2[0];
2175 dist[1] = xyz[1]-xyz2[1];
2176 dist[2] = xyz[2]-xyz2[2];
2183 // Draw functionality.
2184 // Origin: Marian Ivanov, Marian.Ivanov@cern.ch
2187 void AliExternalTrackParam::DrawTrack(Float_t magf, Float_t minR, Float_t maxR, Float_t stepR){
2191 if (minR>maxR) return ;
2192 if (stepR<=0) return ;
2193 Int_t npoints = TMath::Nint((maxR-minR)/stepR)+1;
2194 if (npoints<1) return;
2195 TPolyMarker3D *polymarker = new TPolyMarker3D(npoints);
2196 FillPolymarker(polymarker, magf,minR,maxR,stepR);
2201 void AliExternalTrackParam::FillPolymarker(TPolyMarker3D *pol, Float_t magF, Float_t minR, Float_t maxR, Float_t stepR){
2203 // Fill points in the polymarker
2206 for (Double_t r=minR; r<maxR; r+=stepR){
2208 GetXYZAt(r,magF,point);
2209 pol->SetPoint(counter,point[0],point[1], point[2]);
2210 // printf("xyz\t%f\t%f\t%f\n",point[0], point[1],point[2]);
2215 Int_t AliExternalTrackParam::GetIndex(Int_t i, Int_t j) const {
2217 Int_t min = TMath::Min(i,j);
2218 Int_t max = TMath::Max(i,j);
2220 return min+(max+1)*max/2;
2224 void AliExternalTrackParam::g3helx3(Double_t qfield,
2227 /******************************************************************
2229 * GEANT3 tracking routine in a constant field oriented *
2231 * Tracking is performed with a conventional *
2232 * helix step method *
2234 * Authors R.Brun, M.Hansroul ********* *
2235 * Rewritten V.Perevoztchikov *
2237 * Rewritten in C++ by I.Belikov *
2239 * qfield (kG) - particle charge times magnetic field *
2240 * step (cm) - step length along the helix *
2241 * vect[7](cm,GeV/c) - input/output x, y, z, px/p, py/p ,pz/p, p *
2243 ******************************************************************/
2244 const Int_t ix=0, iy=1, iz=2, ipx=3, ipy=4, ipz=5, ipp=6;
2245 const Double_t kOvSqSix=TMath::Sqrt(1./6.);
2247 Double_t cosx=vect[ipx], cosy=vect[ipy], cosz=vect[ipz];
2249 Double_t rho = qfield*kB2C/vect[ipp];
2250 Double_t tet = rho*step;
2252 Double_t tsint, sintt, sint, cos1t;
2253 if (TMath::Abs(tet) > 0.03) {
2254 sint = TMath::Sin(tet);
2256 tsint = (tet - sint)/tet;
2257 Double_t t=TMath::Sin(0.5*tet);
2261 sintt = (1.-tet*kOvSqSix)*(1.+tet*kOvSqSix); // 1.- tsint;
2266 Double_t f1 = step*sintt;
2267 Double_t f2 = step*cos1t;
2268 Double_t f3 = step*tsint*cosz;
2269 Double_t f4 = -tet*cos1t;
2272 vect[ix] += f1*cosx - f2*cosy;
2273 vect[iy] += f1*cosy + f2*cosx;
2274 vect[iz] += f1*cosz + f3;
2276 vect[ipx] += f4*cosx - f5*cosy;
2277 vect[ipy] += f4*cosy + f5*cosx;
2281 Bool_t AliExternalTrackParam::PropagateToBxByBz(Double_t xk, const Double_t b[3]) {
2282 //----------------------------------------------------------------
2283 // Extrapolate this track to the plane X=xk in the field b[].
2285 // X [cm] is in the "tracking coordinate system" of this track.
2286 // b[]={Bx,By,Bz} [kG] is in the Global coordidate system.
2287 //----------------------------------------------------------------
2290 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
2291 if (TMath::Abs(fP[4])<=kAlmost0) return kFALSE;
2292 // Do not propagate tracks outside the ALICE detector
2293 if (TMath::Abs(dx)>1e5 ||
2294 TMath::Abs(GetY())>1e5 ||
2295 TMath::Abs(GetZ())>1e5) {
2296 AliWarning(Form("Anomalous track, target X:%f",xk));
2301 Double_t crv=GetC(b[2]);
2302 if (TMath::Abs(b[2]) < kAlmost0Field) crv=0.;
2304 Double_t x2r = crv*dx;
2305 Double_t f1=fP[2], f2=f1 + x2r;
2306 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
2307 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
2310 // Estimate the covariance matrix
2311 Double_t &fP3=fP[3], &fP4=fP[4];
2314 &fC10=fC[1], &fC11=fC[2],
2315 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
2316 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
2317 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
2319 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
2323 Double_t f02= dx/(r1*r1*r1); Double_t cc=crv/fP4;
2324 Double_t f04=0.5*dx*dx/(r1*r1*r1); f04*=cc;
2325 Double_t f12= dx*fP3*f1/(r1*r1*r1);
2326 Double_t f14=0.5*dx*dx*fP3*f1/(r1*r1*r1); f14*=cc;
2327 Double_t f13= dx/r1;
2328 Double_t f24= dx; f24*=cc;
2330 Double_t rinv = 1./r1;
2331 Double_t r3inv = rinv*rinv*rinv;
2332 Double_t f24= x2r/fP4;
2333 Double_t f02= dx*r3inv;
2334 Double_t f04=0.5*f24*f02;
2335 Double_t f12= f02*fP3*f1;
2336 Double_t f14=0.5*f24*f02*fP3*f1;
2337 Double_t f13= dx*rinv;
2340 Double_t b00=f02*fC20 + f04*fC40, b01=f12*fC20 + f14*fC40 + f13*fC30;
2341 Double_t b02=f24*fC40;
2342 Double_t b10=f02*fC21 + f04*fC41, b11=f12*fC21 + f14*fC41 + f13*fC31;
2343 Double_t b12=f24*fC41;
2344 Double_t b20=f02*fC22 + f04*fC42, b21=f12*fC22 + f14*fC42 + f13*fC32;
2345 Double_t b22=f24*fC42;
2346 Double_t b40=f02*fC42 + f04*fC44, b41=f12*fC42 + f14*fC44 + f13*fC43;
2347 Double_t b42=f24*fC44;
2348 Double_t b30=f02*fC32 + f04*fC43, b31=f12*fC32 + f14*fC43 + f13*fC33;
2349 Double_t b32=f24*fC43;
2352 Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a02=f02*b22+f04*b42;
2353 Double_t a11=f12*b21+f14*b41+f13*b31,a12=f12*b22+f14*b42+f13*b32;
2354 Double_t a22=f24*b42;
2356 //F*C*Ft = C + (b + bt + a)
2357 fC00 += b00 + b00 + a00;
2358 fC10 += b10 + b01 + a01;
2359 fC20 += b20 + b02 + a02;
2362 fC11 += b11 + b11 + a11;
2363 fC21 += b21 + b12 + a12;
2366 fC22 += b22 + b22 + a22;
2372 // Appoximate step length
2373 double dy2dx = (f1+f2)/(r1+r2);
2374 Double_t step = (TMath::Abs(x2r)<0.05) ? dx*TMath::Abs(r2 + f2*dy2dx) // chord
2375 : 2.*TMath::ASin(0.5*dx*TMath::Sqrt(1.+dy2dx*dy2dx)*crv)/crv; // arc
2376 step *= TMath::Sqrt(1.+ GetTgl()*GetTgl());
2378 // Get the track's (x,y,z) and (px,py,pz) in the Global System
2379 Double_t r[3]; GetXYZ(r);
2380 Double_t p[3]; GetPxPyPz(p);
2387 // Rotate to the system where Bx=By=0.
2388 Double_t bt=TMath::Sqrt(b[0]*b[0] + b[1]*b[1]);
2389 Double_t cosphi=1., sinphi=0.;
2390 if (bt > kAlmost0) {cosphi=b[0]/bt; sinphi=b[1]/bt;}
2391 Double_t bb=TMath::Sqrt(b[0]*b[0] + b[1]*b[1] + b[2]*b[2]);
2392 Double_t costet=1., sintet=0.;
2393 if (bb > kAlmost0) {costet=b[2]/bb; sintet=bt/bb;}
2396 vect[0] = costet*cosphi*r[0] + costet*sinphi*r[1] - sintet*r[2];
2397 vect[1] = -sinphi*r[0] + cosphi*r[1];
2398 vect[2] = sintet*cosphi*r[0] + sintet*sinphi*r[1] + costet*r[2];
2400 vect[3] = costet*cosphi*p[0] + costet*sinphi*p[1] - sintet*p[2];
2401 vect[4] = -sinphi*p[0] + cosphi*p[1];
2402 vect[5] = sintet*cosphi*p[0] + sintet*sinphi*p[1] + costet*p[2];
2407 // Do the helix step
2408 g3helx3(GetSign()*bb,step,vect);
2411 // Rotate back to the Global System
2412 r[0] = cosphi*costet*vect[0] - sinphi*vect[1] + cosphi*sintet*vect[2];
2413 r[1] = sinphi*costet*vect[0] + cosphi*vect[1] + sinphi*sintet*vect[2];
2414 r[2] = -sintet*vect[0] + costet*vect[2];
2416 p[0] = cosphi*costet*vect[3] - sinphi*vect[4] + cosphi*sintet*vect[5];
2417 p[1] = sinphi*costet*vect[3] + cosphi*vect[4] + sinphi*sintet*vect[5];
2418 p[2] = -sintet*vect[3] + costet*vect[5];
2421 // Rotate back to the Tracking System
2422 Double_t cosalp = TMath::Cos(fAlpha);
2423 Double_t sinalp =-TMath::Sin(fAlpha);
2426 t = cosalp*r[0] - sinalp*r[1];
2427 r[1] = sinalp*r[0] + cosalp*r[1];
2430 t = cosalp*p[0] - sinalp*p[1];
2431 p[1] = sinalp*p[0] + cosalp*p[1];
2435 // Do the final correcting step to the target plane (linear approximation)
2436 Double_t x=r[0], y=r[1], z=r[2];
2437 if (TMath::Abs(dx) > kAlmost0) {
2438 if (TMath::Abs(p[0]) < kAlmost0) return kFALSE;
2446 // Calculate the track parameters
2447 t=TMath::Sqrt(p[0]*p[0] + p[1]*p[1]);
2453 fP[4] = GetSign()/(t*pp);
2458 Bool_t AliExternalTrackParam::PropagateParamOnlyBxByBzTo(Double_t xk, const Double_t b[3]) {
2459 //----------------------------------------------------------------
2460 // Extrapolate this track params (w/o cov matrix) to the plane X=xk in the field b[].
2462 // X [cm] is in the "tracking coordinate system" of this track.
2463 // b[]={Bx,By,Bz} [kG] is in the Global coordidate system.
2464 //----------------------------------------------------------------
2467 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
2468 if (TMath::Abs(fP[4])<=kAlmost0) return kFALSE;
2469 // Do not propagate tracks outside the ALICE detector
2470 if (TMath::Abs(dx)>1e5 ||
2471 TMath::Abs(GetY())>1e5 ||
2472 TMath::Abs(GetZ())>1e5) {
2473 AliWarning(Form("Anomalous track, target X:%f",xk));
2478 Double_t crv=GetC(b[2]);
2479 if (TMath::Abs(b[2]) < kAlmost0Field) crv=0.;
2481 Double_t x2r = crv*dx;
2482 Double_t f1=fP[2], f2=f1 + x2r;
2483 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
2484 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
2486 Double_t r1=TMath::Sqrt((1.-f1)*(1.+f1)), r2=TMath::Sqrt((1.-f2)*(1.+f2));
2488 // Appoximate step length
2489 double dy2dx = (f1+f2)/(r1+r2);
2490 Double_t step = (TMath::Abs(x2r)<0.05) ? dx*TMath::Abs(r2 + f2*dy2dx) // chord
2491 : 2.*TMath::ASin(0.5*dx*TMath::Sqrt(1.+dy2dx*dy2dx)*crv)/crv; // arc
2492 step *= TMath::Sqrt(1.+ GetTgl()*GetTgl());
2494 // Get the track's (x,y,z) and (px,py,pz) in the Global System
2495 Double_t r[3]; GetXYZ(r);
2496 Double_t p[3]; GetPxPyPz(p);
2502 // Rotate to the system where Bx=By=0.
2503 Double_t bt=TMath::Sqrt(b[0]*b[0] + b[1]*b[1]);
2504 Double_t cosphi=1., sinphi=0.;
2505 if (bt > kAlmost0) {cosphi=b[0]/bt; sinphi=b[1]/bt;}
2506 Double_t bb=TMath::Sqrt(b[0]*b[0] + b[1]*b[1] + b[2]*b[2]);
2507 Double_t costet=1., sintet=0.;
2508 if (bb > kAlmost0) {costet=b[2]/bb; sintet=bt/bb;}
2511 vect[0] = costet*cosphi*r[0] + costet*sinphi*r[1] - sintet*r[2];
2512 vect[1] = -sinphi*r[0] + cosphi*r[1];
2513 vect[2] = sintet*cosphi*r[0] + sintet*sinphi*r[1] + costet*r[2];
2515 vect[3] = costet*cosphi*p[0] + costet*sinphi*p[1] - sintet*p[2];
2516 vect[4] = -sinphi*p[0] + cosphi*p[1];
2517 vect[5] = sintet*cosphi*p[0] + sintet*sinphi*p[1] + costet*p[2];
2521 // Do the helix step
2522 g3helx3(GetSign()*bb,step,vect);
2524 // Rotate back to the Global System
2525 r[0] = cosphi*costet*vect[0] - sinphi*vect[1] + cosphi*sintet*vect[2];
2526 r[1] = sinphi*costet*vect[0] + cosphi*vect[1] + sinphi*sintet*vect[2];
2527 r[2] = -sintet*vect[0] + costet*vect[2];
2529 p[0] = cosphi*costet*vect[3] - sinphi*vect[4] + cosphi*sintet*vect[5];
2530 p[1] = sinphi*costet*vect[3] + cosphi*vect[4] + sinphi*sintet*vect[5];
2531 p[2] = -sintet*vect[3] + costet*vect[5];
2533 // Rotate back to the Tracking System
2534 Double_t cosalp = TMath::Cos(fAlpha);
2535 Double_t sinalp =-TMath::Sin(fAlpha);
2538 t = cosalp*r[0] - sinalp*r[1];
2539 r[1] = sinalp*r[0] + cosalp*r[1];
2542 t = cosalp*p[0] - sinalp*p[1];
2543 p[1] = sinalp*p[0] + cosalp*p[1];
2546 // Do the final correcting step to the target plane (linear approximation)
2547 Double_t x=r[0], y=r[1], z=r[2];
2548 if (TMath::Abs(dx) > kAlmost0) {
2549 if (TMath::Abs(p[0]) < kAlmost0) return kFALSE;
2557 // Calculate the track parameters
2558 t=TMath::Sqrt(p[0]*p[0] + p[1]*p[1]);
2564 fP[4] = GetSign()/(t*pp);
2570 Bool_t AliExternalTrackParam::Translate(Double_t *vTrasl,Double_t *covV){
2572 //Translation: in the event mixing, the tracks can be shifted
2573 //of the difference among primary vertices (vTrasl) and
2574 //the covariance matrix is changed accordingly
2575 //(covV = covariance of the primary vertex).
2576 //Origin: "Romita, Rossella" <R.Romita@gsi.de>
2578 TVector3 translation;
2579 // vTrasl coordinates in the local system
2580 translation.SetXYZ(vTrasl[0],vTrasl[1],vTrasl[2]);
2581 translation.RotateZ(-fAlpha);
2582 translation.GetXYZ(vTrasl);
2584 //compute the new x,y,z of the track
2585 Double_t newX=fX-vTrasl[0];
2586 Double_t newY=fP[0]-vTrasl[1];
2587 Double_t newZ=fP[1]-vTrasl[2];
2589 //define the new parameters
2590 Double_t newParam[5];
2597 // recompute the covariance matrix:
2598 // 1. covV in the local system
2599 Double_t cosRot=TMath::Cos(fAlpha), sinRot=TMath::Sin(fAlpha);
2620 if(uUi.Determinant() <= 0.) {return kFALSE;}
2621 TMatrixD uUiQi(uUi,TMatrixD::kMult,qQi);
2622 TMatrixD m(qQi,TMatrixD::kTransposeMult,uUiQi);
2624 //2. compute the new covariance matrix of the track
2625 Double_t sigmaXX=m(0,0);
2626 Double_t sigmaXZ=m(2,0);
2627 Double_t sigmaXY=m(1,0);
2628 Double_t sigmaYY=GetSigmaY2()+m(1,1);
2629 Double_t sigmaYZ=fC[1]+m(1,2);
2630 Double_t sigmaZZ=fC[2]+m(2,2);
2631 Double_t covarianceYY=sigmaYY + (-1.)*((sigmaXY*sigmaXY)/sigmaXX);
2632 Double_t covarianceYZ=sigmaYZ-(sigmaXZ*sigmaXY/sigmaXX);
2633 Double_t covarianceZZ=sigmaZZ-((sigmaXZ*sigmaXZ)/sigmaXX);
2635 Double_t newCov[15];
2636 newCov[0]=covarianceYY;
2637 newCov[1]=covarianceYZ;
2638 newCov[2]=covarianceZZ;
2639 for(Int_t i=3;i<15;i++){
2643 // set the new parameters
2645 Set(newX,fAlpha,newParam,newCov);
2650 void AliExternalTrackParam::CheckCovariance() {
2652 // This function forces the diagonal elements of the covariance matrix to be positive.
2653 // In case the diagonal element is bigger than the maximal allowed value, it is set to
2654 // the limit and the off-diagonal elements that correspond to it are set to zero.
2656 fC[0] = TMath::Abs(fC[0]);
2658 double scl = TMath::Sqrt(kC0max/fC[0]);
2665 fC[2] = TMath::Abs(fC[2]);
2667 double scl = TMath::Sqrt(kC2max/fC[2]);
2674 fC[5] = TMath::Abs(fC[5]);
2676 double scl = TMath::Sqrt(kC5max/fC[5]);
2683 fC[9] = TMath::Abs(fC[9]);
2685 double scl = TMath::Sqrt(kC9max/fC[9]);
2692 fC[14] = TMath::Abs(fC[14]);
2693 if (fC[14]>kC14max) {
2694 double scl = TMath::Sqrt(kC14max/fC[14]);
2702 // The part below is used for tests and normally is commented out
2703 // TMatrixDSym m(5);
2707 // m(1,0)=fC[1]; m(1,1)=fC[2];
2708 // m(2,0)=fC[3]; m(2,1)=fC[4]; m(2,2)=fC[5];
2709 // m(3,0)=fC[6]; m(3,1)=fC[7]; m(3,2)=fC[8]; m(3,3)=fC[9];
2710 // 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];
2713 // m(0,2)=m(2,0); m(1,2)=m(2,1);
2714 // m(0,3)=m(3,0); m(1,3)=m(3,1); m(2,3)=m(3,2);
2715 // m(0,4)=m(4,0); m(1,4)=m(4,1); m(2,4)=m(4,2); m(3,4)=m(4,3);
2716 // m.EigenVectors(eig);
2718 // // assert(eig(0)>=0 && eig(1)>=0 && eig(2)>=0 && eig(3)>=0 && eig(4)>=0);
2719 // if (!(eig(0)>=0 && eig(1)>=0 && eig(2)>=0 && eig(3)>=0 && eig(4)>=0)) {
2720 // AliWarning("Negative eigenvalues of the covariance matrix!");
2726 Bool_t AliExternalTrackParam::ConstrainToVertex(const AliVVertex* vtx, Double_t b[3])
2728 // Constrain TPC inner params constrained
2733 Double_t dz[2], cov[3];
2734 if (!PropagateToDCABxByBz(vtx, b, 3, dz, cov))
2738 vtx->GetCovarianceMatrix(covar);
2740 Double_t p[2]= { fP[0] - dz[0], fP[1] - dz[1] };
2741 Double_t c[3]= { covar[2], 0., covar[5] };
2743 Double_t chi2C = GetPredictedChi2(p,c);
2753 //___________________________________________________________________________________________
2754 Bool_t AliExternalTrackParam::GetXatLabR(Double_t r,Double_t &x, Double_t bz, Int_t dir) const
2756 // Get local X of the track position estimated at the radius lab radius r.
2757 // The track curvature is accounted exactly
2759 // The flag "dir" can be used to remove the ambiguity of which intersection to take (out of 2 possible)
2760 // 0 - take the intersection closest to the current track position
2761 // >0 - go along the track (increasing fX)
2762 // <0 - go backward (decreasing fX)
2764 const Double_t &fy=fP[0], &sn = fP[2];
2765 const double kEps = 1.e-6;
2767 double crv = GetC(bz);
2768 if (TMath::Abs(crv)>kAlmost0) { // helix
2769 // get center of the track circle
2770 double tR = 1./crv; // track radius (for the moment signed)
2771 double cs = TMath::Sqrt((1-sn)*(1+sn));
2772 double x0 = fX - sn*tR;
2773 double y0 = fy + cs*tR;
2774 double r0 = TMath::Sqrt(x0*x0+y0*y0);
2775 // printf("Xc:%+e Yc:%+e tR:%e r0:%e\n",x0,y0,tR,r0);
2777 if (r0<=kAlmost0) return kFALSE; // the track is concentric to circle
2778 tR = TMath::Abs(tR);
2779 double tR2r0=1.,g=0,tmp=0;
2780 if (TMath::Abs(tR-r0)>kEps) {
2782 g = 0.5*(r*r/(r0*tR) - tR2r0 - 1./tR2r0);
2787 g = 0.5*r*r/(r0*tR) - 1;
2788 tmp = 0.5*r*r/(r0*r0);
2790 double det = (1.-g)*(1.+g);
2791 if (det<0) return kFALSE; // does not reach raduis r
2792 det = TMath::Sqrt(det);
2794 // the intersection happens in 2 points: {x0+tR*C,y0+tR*S}
2795 // with C=f*c0+-|s0|*det and S=f*s0-+c0 sign(s0)*det
2796 // where s0 and c0 make direction for the circle center (=x0/r0 and y0/r0)
2800 if (TMath::Abs(y0)>kAlmost0) { // when y0==0 the x,y is unique
2801 double dfx = tR2r0*TMath::Abs(y0)*det;
2802 double dfy = tR2r0*x0*TMath::Sign(det,y0);
2803 if (dir==0) { // chose the one which corresponds to smallest step
2804 double delta = (x-fX)*dfx-(y-fy)*dfy; // the choice of + in C will lead to smaller step if delta<0
2805 if (delta<0) x += dfx;
2808 else if (dir>0) { // along track direction: x must be > fX
2809 x -= dfx; // try the smallest step (dfx is positive)
2810 double dfeps = fX-x; // handle special case of very small step
2811 if (dfeps<-kEps) return kTRUE;
2812 if (TMath::Abs(dfeps)<kEps && // are we already in right r?
2813 TMath::Abs(fX*fX+fy*fy - r*r)<kEps) return fX;
2815 if (x-fX>0) return kTRUE;
2816 if (x-fX<-kEps) return kFALSE;
2817 x = fX; // don't move
2819 else { // backward: x must be < fX
2820 x += dfx; // try the smallest step (dfx is positive)
2821 double dfeps = x-fX; // handle special case of very small step
2822 if (dfeps<-kEps) return kTRUE;
2823 if (TMath::Abs(dfeps)<kEps && // are we already in right r?
2824 TMath::Abs(fX*fX+fy*fy - r*r)<kEps) return fX;
2826 if (x-fX<0) return kTRUE;
2827 if (x-fX>kEps) return kFALSE;
2828 x = fX; // don't move
2831 else { // special case: track touching the circle just in 1 point
2832 if ( (dir>0&&x<fX) || (dir<0&&x>fX) ) return kFALSE;
2835 else { // this is a straight track
2836 if (TMath::Abs(sn)>=kAlmost1) { // || to Y axis
2837 double det = (r-fX)*(r+fX);
2838 if (det<0) return kFALSE; // does not reach raduis r
2840 if (dir==0) return kTRUE;
2841 det = TMath::Sqrt(det);
2842 if (dir>0) { // along the track direction
2843 if (sn>0) {if (fy>det) return kFALSE;} // track is along Y axis and above the circle
2844 else {if (fy<-det) return kFALSE;} // track is against Y axis amd belo the circle
2846 else if(dir>0) { // agains track direction
2847 if (sn>0) {if (fy<-det) return kFALSE;} // track is along Y axis
2848 else if (fy>det) return kFALSE; // track is against Y axis
2851 else if (TMath::Abs(sn)<=kAlmost0) { // || to X axis
2852 double det = (r-fy)*(r+fy);
2853 if (det<0) return kFALSE; // does not reach raduis r
2854 det = TMath::Sqrt(det);
2856 x = fX>0 ? det : -det; // choose the solution requiring the smalest step
2859 else if (dir>0) { // along the track direction
2860 if (fX > det) return kFALSE; // current point is in on the right from the circle
2861 else if (fX <-det) x = -det; // on the left
2862 else x = det; // within the circle
2864 else { // against the track direction
2865 if (fX <-det) return kFALSE;
2866 else if (fX > det) x = det;
2870 else { // general case of straight line
2871 double cs = TMath::Sqrt((1-sn)*(1+sn));
2872 double xsyc = fX*sn-fy*cs;
2873 double det = (r-xsyc)*(r+xsyc);
2874 if (det<0) return kFALSE; // does not reach raduis r
2875 det = TMath::Sqrt(det);
2876 double xcys = fX*cs+fy*sn;
2878 if (dir==0) t += t>0 ? -det:det; // chose the solution requiring the smalest step
2879 else if (dir>0) { // go in increasing fX direction. ( t+-det > 0)
2880 if (t>=-det) t += -det; // take minimal step giving t>0
2881 else return kFALSE; // both solutions have negative t
2883 else { // go in increasing fX direction. (t+-det < 0)
2884 if (t<det) t -= det; // take minimal step giving t<0
2885 else return kFALSE; // both solutions have positive t
2893 //_________________________________________________________
2894 Bool_t AliExternalTrackParam::GetXYZatR(Double_t xr,Double_t bz, Double_t *xyz, Double_t* alpSect) const
2896 // This method has 3 modes of behaviour
2897 // 1) xyz[3] array is provided but alpSect pointer is 0: calculate the position of track intersection
2898 // with circle of radius xr and fill it in xyz array
2899 // 2) alpSect pointer is provided: find alpha of the sector where the track reaches local coordinate xr
2900 // Note that in this case xr is NOT the radius but the local coordinate.
2901 // If the xyz array is provided, it will be filled by track lab coordinates at local X in this sector
2902 // 3) Neither alpSect nor xyz pointers are provided: just check if the track reaches radius xr
2905 double crv = GetC(bz);
2906 if ( (TMath::Abs(bz))<kAlmost0Field ) crv=0.;
2907 const double &fy = fP[0];
2908 const double &fz = fP[1];
2909 const double &sn = fP[2];
2910 const double &tgl = fP[3];
2912 // general circle parameterization:
2913 // x = (r0+tR)cos(phi0) - tR cos(t+phi0)
2914 // y = (r0+tR)sin(phi0) - tR sin(t+phi0)
2915 // where qb is the sign of the curvature, tR is the track's signed radius and r0
2916 // is the DCA of helix to origin
2918 double tR = 1./crv; // track radius signed
2919 double cs = TMath::Sqrt((1-sn)*(1+sn));
2920 double x0 = fX - sn*tR; // helix center coordinates
2921 double y0 = fy + cs*tR;
2922 double phi0 = TMath::ATan2(y0,x0); // angle of PCA wrt to the origin
2923 if (tR<0) phi0 += TMath::Pi();
2924 if (phi0 > TMath::Pi()) phi0 -= 2.*TMath::Pi();
2925 else if (phi0 <-TMath::Pi()) phi0 += 2.*TMath::Pi();
2926 double cs0 = TMath::Cos(phi0);
2927 double sn0 = TMath::Sin(phi0);
2928 double r0 = x0*cs0 + y0*sn0 - tR; // DCA to origin
2929 double r2R = 1.+r0/tR;
2932 if (r2R<kAlmost0) return kFALSE; // helix is centered at the origin, no specific intersection with other concetric circle
2933 if (!xyz && !alpSect) return kTRUE;
2934 double xr2R = xr/tR;
2935 double r2Ri = 1./r2R;
2936 // the intersection cos(t) = [1 + (r0/tR+1)^2 - (r0/tR)^2]/[2(1+r0/tR)]
2937 double cosT = 0.5*(r2R + (1-xr2R*xr2R)*r2Ri);
2938 if ( TMath::Abs(cosT)>kAlmost1 ) {
2939 // printf("Does not reach : %f %f\n",r0,tR);
2940 return kFALSE; // track does not reach the radius xr
2943 double t = TMath::ACos(cosT);
2945 // intersection point
2947 xyzi[0] = x0 - tR*TMath::Cos(t+phi0);
2948 xyzi[1] = y0 - tR*TMath::Sin(t+phi0);
2949 if (xyz) { // if postition is requested, then z is needed:
2950 double t0 = TMath::ATan2(cs,-sn) - phi0;
2951 double z0 = fz - t0*tR*tgl;
2952 xyzi[2] = z0 + tR*t*tgl;
2956 Local2GlobalPosition(xyzi,fAlpha);
2965 double &alp = *alpSect;
2966 // determine the sector of crossing
2967 double phiPos = TMath::Pi()+TMath::ATan2(-xyzi[1],-xyzi[0]);
2968 int sect = ((Int_t)(phiPos*TMath::RadToDeg()))/20;
2969 alp = TMath::DegToRad()*(20*sect+10);
2970 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
2973 Double_t ca=TMath::Cos(alp-fAlpha), sa=TMath::Sin(alp-fAlpha);
2974 if ((cs*ca+sn*sa)<0) {
2975 AliDebug(1,Form("Rotation to target sector impossible: local cos(phi) would become %.2f",cs*ca+sn*sa));
2980 if (TMath::Abs(f1) >= kAlmost1) {
2981 AliDebug(1,Form("Rotation to target sector impossible: local sin(phi) would become %.2f",f1));
2985 double tmpX = fX*ca + fy*sa;
2986 double tmpY = -fX*sa + fy*ca;
2988 // estimate Y at X=xr
2992 if (TMath::Abs(f2) >= kAlmost1) {
2993 AliDebug(1,Form("Propagation in target sector failed ! %.10e",f2));
2996 r1 = TMath::Sqrt((1.-f1)*(1.+f1));
2997 r2 = TMath::Sqrt((1.-f2)*(1.+f2));
2998 dy2dx = (f1+f2)/(r1+r2);
2999 yloc = tmpY + dx*dy2dx;
3000 if (yloc>ylocMax) {alp += 2*TMath::Pi()/18; sect++;}
3001 else if (yloc<-ylocMax) {alp -= 2*TMath::Pi()/18; sect--;}
3003 if (alp >= TMath::Pi()) alp -= 2*TMath::Pi();
3004 else if (alp < -TMath::Pi()) alp += 2*TMath::Pi();
3005 // if (sect>=18) sect = 0;
3006 // if (sect<=0) sect = 17;
3009 // if alpha was requested, then recalculate the position at intersection in sector
3013 if (TMath::Abs(x2r)<0.05) xyz[2] = fz + dx*(r2 + f2*dy2dx)*tgl;
3015 // for small dx/R the linear apporximation of the arc by the segment is OK,
3016 // but at large dx/R the error is very large and leads to incorrect Z propagation
3017 // angle traversed delta = 2*asin(dist_start_end / R / 2), hence the arc is: R*deltaPhi
3018 // The dist_start_end is obtained from sqrt(dx^2+dy^2) = x/(r1+r2)*sqrt(2+f1*f2+r1*r2)
3019 // Similarly, the rotation angle in linear in dx only for dx<<R
3020 double chord = dx*TMath::Sqrt(1+dy2dx*dy2dx); // distance from old position to new one
3021 double rot = 2*TMath::ASin(0.5*chord*crv); // angular difference seen from the circle center
3022 xyz[2] = fz + rot/crv*tgl;
3024 Local2GlobalPosition(xyz,alp);
3032 Double_t AliExternalTrackParam::GetParameterAtRadius(Double_t r, Double_t bz, Int_t parType) const
3035 // Get track parameters at the radius of interest.
3036 // Given function is aimed to be used to interactivelly (tree->Draw())
3037 // access track properties at different radii
3039 // TO BE USED WITH SPECICAL CARE -
3040 // it is aimed to be used for rough calculation as constant field and
3041 // no correction for material is used
3043 // r - radius of interest
3044 // bz - magentic field
3045 // retun values dependens on parType:
3055 // parType = 7 - global position phi
3056 // parType = 8 - global direction phi
3057 // parType = 9 - direction phi- positionphi
3065 Bool_t res = GetXatLabR(r,localX,bz,1);
3071 // position parameters
3073 GetXYZAt(localX,bz,xyz);
3075 return xyz[parType];
3078 if (parType==6) return TMath::Sqrt(xyz[0]*xyz[0]+xyz[1]*xyz[1]);
3079 if (parType==7) return TMath::ATan2(xyz[1],xyz[0]);
3081 // momenta parameters
3083 GetPxPyPzAt(localX,bz,pxyz);
3084 if (parType==8) return TMath::ATan2(pxyz[1],pxyz[0]);
3086 Double_t diff = TMath::ATan2(pxyz[1],pxyz[0])-TMath::ATan2(xyz[1],xyz[0]);
3087 if (diff>TMath::Pi()) diff-=TMath::TwoPi();
3088 if (diff<-TMath::Pi()) diff+=TMath::TwoPi();
3091 if (parType>=3&&parType<6) {
3092 return pxyz[parType%3];