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 ///////////////////////////////////////////////////////////////////////////////
28 #include <TMatrixDSym.h>
29 #include <TPolyMarker3D.h>
32 #include "AliExternalTrackParam.h"
33 #include "AliMathBase.h"
34 #include "AliVVertex.h"
37 ClassImp(AliExternalTrackParam)
39 Double32_t AliExternalTrackParam::fgMostProbablePt=kMostProbablePt;
41 //_____________________________________________________________________________
42 AliExternalTrackParam::AliExternalTrackParam() :
48 // default constructor
50 for (Int_t i = 0; i < 5; i++) fP[i] = 0;
51 for (Int_t i = 0; i < 15; i++) fC[i] = 0;
54 //_____________________________________________________________________________
55 AliExternalTrackParam::AliExternalTrackParam(const AliExternalTrackParam &track):
63 for (Int_t i = 0; i < 5; i++) fP[i] = track.fP[i];
64 for (Int_t i = 0; i < 15; i++) fC[i] = track.fC[i];
67 //_____________________________________________________________________________
68 AliExternalTrackParam& AliExternalTrackParam::operator=(const AliExternalTrackParam &trkPar)
71 // assignment operator
75 AliVTrack::operator=(trkPar);
77 fAlpha = trkPar.fAlpha;
79 for (Int_t i = 0; i < 5; i++) fP[i] = trkPar.fP[i];
80 for (Int_t i = 0; i < 15; i++) fC[i] = trkPar.fC[i];
86 //_____________________________________________________________________________
87 AliExternalTrackParam::AliExternalTrackParam(Double_t x, Double_t alpha,
88 const Double_t param[5],
89 const Double_t covar[15]) :
95 // create external track parameters from given arguments
97 for (Int_t i = 0; i < 5; i++) fP[i] = param[i];
98 for (Int_t i = 0; i < 15; i++) fC[i] = covar[i];
101 //_____________________________________________________________________________
102 AliExternalTrackParam::AliExternalTrackParam(const AliVTrack *vTrack) :
108 // Constructor from virtual track,
109 // This is not a copy contructor !
112 if (vTrack->InheritsFrom("AliExternalTrackParam")) {
113 AliError("This is not a copy constructor. Use AliExternalTrackParam(const AliExternalTrackParam &) !");
114 AliWarning("Calling the default constructor...");
115 AliExternalTrackParam();
119 Double_t xyz[3],pxpypz[3],cv[21];
121 pxpypz[0]=vTrack->Px();
122 pxpypz[1]=vTrack->Py();
123 pxpypz[2]=vTrack->Pz();
124 vTrack->GetCovarianceXYZPxPyPz(cv);
125 Short_t sign = (Short_t)vTrack->Charge();
127 Set(xyz,pxpypz,cv,sign);
130 //_____________________________________________________________________________
131 AliExternalTrackParam::AliExternalTrackParam(Double_t xyz[3],Double_t pxpypz[3],
132 Double_t cv[21],Short_t sign) :
138 // constructor from the global parameters
141 Set(xyz,pxpypz,cv,sign);
144 //_____________________________________________________________________________
145 void AliExternalTrackParam::Set(Double_t xyz[3],Double_t pxpypz[3],
146 Double_t cv[21],Short_t sign)
149 // create external track parameters from the global parameters
150 // x,y,z,px,py,pz and their 6x6 covariance matrix
151 // A.Dainese 10.10.08
153 // Calculate alpha: the rotation angle of the corresponding local system
154 fAlpha = TMath::ATan2(pxpypz[1],pxpypz[0]);
156 // Get the vertex of origin and the momentum
157 TVector3 ver(xyz[0],xyz[1],xyz[2]);
158 TVector3 mom(pxpypz[0],pxpypz[1],pxpypz[2]);
160 // Rotate to the local coordinate system
161 ver.RotateZ(-fAlpha);
162 mom.RotateZ(-fAlpha);
164 // x of the reference plane
167 Double_t charge = (Double_t)sign;
171 fP[2] = TMath::Sin(mom.Phi());
172 fP[3] = mom.Pz()/mom.Pt();
173 fP[4] = TMath::Sign(1/mom.Pt(),charge);
175 // Covariance matrix (formulas to be simplified)
177 Double_t pt=1./TMath::Abs(fP[4]);
178 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
179 Double_t r=TMath::Sqrt((1.-fP[2])*(1.+fP[2]));
181 Double_t m00=-sn;// m10=cs;
182 Double_t m23=-pt*(sn + fP[2]*cs/r), m43=-pt*pt*(r*cs - fP[2]*sn);
183 Double_t m24= pt*(cs - fP[2]*sn/r), m44=-pt*pt*(r*sn + fP[2]*cs);
184 Double_t m35=pt, m45=-pt*pt*fP[3];
190 Double_t cv34 = TMath::Sqrt(cv[3 ]*cv[3 ]+cv[4 ]*cv[4 ]);
191 Double_t a1=cv[13]-cv[9]*(m23*m44+m43*m24)/m23/m43;
192 Double_t a2=m23*m24-m23*(m23*m44+m43*m24)/m43;
193 Double_t a3=m43*m44-m43*(m23*m44+m43*m24)/m23;
194 Double_t a4=cv[14]-2.*cv[9]*m24*m44/m23/m43;
195 Double_t a5=m24*m24-2.*m24*m44*m23/m43;
196 Double_t a6=m44*m44-2.*m24*m44*m43/m23;
198 fC[0 ] = cv[0 ]+cv[2 ];
199 fC[1 ] = TMath::Sign(cv34,cv[3 ]/m00);
201 fC[3 ] = (cv[10]/m44-cv[6]/m43)/(m24/m44-m23/m43)/m00;
202 fC[10] = (cv[6]/m00-fC[3 ]*m23)/m43;
203 fC[6 ] = (cv[15]/m00-fC[10]*m45)/m35;
204 fC[4 ] = (cv[12]-cv[8]*m44/m43)/(m24-m23*m44/m43);
205 fC[11] = (cv[8]-fC[4]*m23)/m43;
206 fC[7 ] = cv[17]/m35-fC[11]*m45/m35;
207 fC[5 ] = TMath::Abs((a4-a6*a1/a3)/(a5-a6*a2/a3));
208 fC[14] = TMath::Abs(a1/a3-a2*fC[5]/a3);
209 fC[12] = (cv[9]-fC[5]*m23*m23-fC[14]*m43*m43)/m23/m43;
210 Double_t b1=cv[18]-fC[12]*m23*m45-fC[14]*m43*m45;
213 Double_t b4=cv[19]-fC[12]*m24*m45-fC[14]*m44*m45;
216 fC[8 ] = (b4-b6*b1/b3)/(b5-b6*b2/b3);
217 fC[13] = b1/b3-b2*fC[8]/b3;
218 fC[9 ] = TMath::Abs((cv[20]-fC[14]*(m45*m45)-fC[13]*2.*m35*m45)/(m35*m35));
223 //_____________________________________________________________________________
224 void AliExternalTrackParam::Reset() {
226 // Resets all the parameters to 0
229 for (Int_t i = 0; i < 5; i++) fP[i] = 0;
230 for (Int_t i = 0; i < 15; i++) fC[i] = 0;
233 //_____________________________________________________________________________
234 void AliExternalTrackParam::AddCovariance(const Double_t c[15]) {
236 // Add "something" to the track covarince matrix.
237 // May be needed to account for unknown mis-calibration/mis-alignment
240 fC[1] +=c[1]; fC[2] +=c[2];
241 fC[3] +=c[3]; fC[4] +=c[4]; fC[5] +=c[5];
242 fC[6] +=c[6]; fC[7] +=c[7]; fC[8] +=c[8]; fC[9] +=c[9];
243 fC[10]+=c[10]; fC[11]+=c[11]; fC[12]+=c[12]; fC[13]+=c[13]; fC[14]+=c[14];
247 Double_t AliExternalTrackParam::GetP() const {
248 //---------------------------------------------------------------------
249 // This function returns the track momentum
250 // Results for (nearly) straight tracks are meaningless !
251 //---------------------------------------------------------------------
252 if (TMath::Abs(fP[4])<=kAlmost0) return kVeryBig;
253 return TMath::Sqrt(1.+ fP[3]*fP[3])/TMath::Abs(fP[4]);
256 Double_t AliExternalTrackParam::Get1P() const {
257 //---------------------------------------------------------------------
258 // This function returns the 1/(track momentum)
259 //---------------------------------------------------------------------
260 return TMath::Abs(fP[4])/TMath::Sqrt(1.+ fP[3]*fP[3]);
263 //_______________________________________________________________________
264 Double_t AliExternalTrackParam::GetD(Double_t x,Double_t y,Double_t b) const {
265 //------------------------------------------------------------------
266 // This function calculates the transverse impact parameter
267 // with respect to a point with global coordinates (x,y)
268 // in the magnetic field "b" (kG)
269 //------------------------------------------------------------------
270 if (TMath::Abs(b) < kAlmost0Field) return GetLinearD(x,y);
271 Double_t rp4=GetC(b);
273 Double_t xt=fX, yt=fP[0];
275 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
276 Double_t a = x*cs + y*sn;
277 y = -x*sn + y*cs; x=a;
280 sn=rp4*xt - fP[2]; cs=rp4*yt + TMath::Sqrt(1.- fP[2]*fP[2]);
281 a=2*(xt*fP[2] - yt*TMath::Sqrt(1.- fP[2]*fP[2]))-rp4*(xt*xt + yt*yt);
282 return -a/(1 + TMath::Sqrt(sn*sn + cs*cs));
285 //_______________________________________________________________________
286 void AliExternalTrackParam::
287 GetDZ(Double_t x, Double_t y, Double_t z, Double_t b, Float_t dz[2]) const {
288 //------------------------------------------------------------------
289 // This function calculates the transverse and longitudinal impact parameters
290 // with respect to a point with global coordinates (x,y)
291 // in the magnetic field "b" (kG)
292 //------------------------------------------------------------------
293 Double_t f1 = fP[2], r1 = TMath::Sqrt(1. - f1*f1);
294 Double_t xt=fX, yt=fP[0];
295 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
296 Double_t a = x*cs + y*sn;
297 y = -x*sn + y*cs; x=a;
300 Double_t rp4=GetC(b);
301 if ((TMath::Abs(b) < kAlmost0Field) || (TMath::Abs(rp4) < kAlmost0)) {
302 dz[0] = -(xt*f1 - yt*r1);
303 dz[1] = fP[1] + (dz[0]*f1 - xt)/r1*fP[3] - z;
307 sn=rp4*xt - f1; cs=rp4*yt + r1;
308 a=2*(xt*f1 - yt*r1)-rp4*(xt*xt + yt*yt);
309 Double_t rr=TMath::Sqrt(sn*sn + cs*cs);
311 Double_t f2 = -sn/rr, r2 = TMath::Sqrt(1. - f2*f2);
312 dz[1] = fP[1] + fP[3]/rp4*TMath::ASin(f2*r1 - f1*r2) - z;
315 //_______________________________________________________________________
316 Double_t AliExternalTrackParam::GetLinearD(Double_t xv,Double_t yv) const {
317 //------------------------------------------------------------------
318 // This function calculates the transverse impact parameter
319 // with respect to a point with global coordinates (xv,yv)
320 // neglecting the track curvature.
321 //------------------------------------------------------------------
322 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
323 Double_t x= xv*cs + yv*sn;
324 Double_t y=-xv*sn + yv*cs;
326 Double_t d = (fX-x)*fP[2] - (fP[0]-y)*TMath::Sqrt(1.- fP[2]*fP[2]);
331 Bool_t AliExternalTrackParam::CorrectForMeanMaterial
332 (Double_t xOverX0, Double_t xTimesRho, Double_t mass, Bool_t anglecorr,
333 Double_t (*Bethe)(Double_t)) {
334 //------------------------------------------------------------------
335 // This function corrects the track parameters for the crossed material.
336 // "xOverX0" - X/X0, the thickness in units of the radiation length.
337 // "xTimesRho" - is the product length*density (g/cm^2).
338 // "mass" - the mass of this particle (GeV/c^2).
339 //------------------------------------------------------------------
344 Double_t &fC22=fC[5];
345 Double_t &fC33=fC[9];
346 Double_t &fC43=fC[13];
347 Double_t &fC44=fC[14];
349 //Apply angle correction, if requested
351 Double_t angle=TMath::Sqrt((1.+ fP3*fP3)/(1.- fP2*fP2));
358 Double_t beta2=p2/(p2 + mass*mass);
360 //Multiple scattering******************
362 Double_t theta2=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(xOverX0);
363 if(theta2>TMath::Pi()*TMath::Pi()) return kFALSE;
364 //Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*TMath::Abs(d)*9.36*2.33;
365 fC22 += theta2*(1.- fP2*fP2)*(1. + fP3*fP3);
366 fC33 += theta2*(1. + fP3*fP3)*(1. + fP3*fP3);
367 fC43 += theta2*fP3*fP4*(1. + fP3*fP3);
368 fC44 += theta2*fP3*fP4*fP3*fP4;
371 //Energy losses************************
372 if ((xTimesRho != 0.) && (beta2 < 1.)) {
373 Double_t dE=Bethe(p/mass)*xTimesRho;
374 Double_t e=TMath::Sqrt(p2 + mass*mass);
375 if ( TMath::Abs(dE) > 0.3*e ) return kFALSE; //30% energy loss is too much!
377 if (TMath::Abs(fP4)>100.) return kFALSE; // Do not track below 10 MeV/c
380 // Approximate energy loss fluctuation (M.Ivanov)
381 const Double_t knst=0.07; // To be tuned.
382 Double_t sigmadE=knst*TMath::Sqrt(TMath::Abs(dE));
383 fC44+=((sigmadE*e/p2*fP4)*(sigmadE*e/p2*fP4));
391 Bool_t AliExternalTrackParam::CorrectForMaterial
392 (Double_t d, Double_t x0, Double_t mass, Double_t (*Bethe)(Double_t)) {
393 //------------------------------------------------------------------
394 // Deprecated function !
395 // Better use CorrectForMeanMaterial instead of it.
397 // This function corrects the track parameters for the crossed material
398 // "d" - the thickness (fraction of the radiation length)
399 // "x0" - the radiation length (g/cm^2)
400 // "mass" - the mass of this particle (GeV/c^2)
401 //------------------------------------------------------------------
406 Double_t &fC22=fC[5];
407 Double_t &fC33=fC[9];
408 Double_t &fC43=fC[13];
409 Double_t &fC44=fC[14];
413 Double_t beta2=p2/(p2 + mass*mass);
414 d*=TMath::Sqrt((1.+ fP3*fP3)/(1.- fP2*fP2));
416 //Multiple scattering******************
418 Double_t theta2=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(d);
419 if(theta2>TMath::Pi()*TMath::Pi()) return kFALSE;
420 //Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*TMath::Abs(d)*9.36*2.33;
421 fC22 += theta2*(1.- fP2*fP2)*(1. + fP3*fP3);
422 fC33 += theta2*(1. + fP3*fP3)*(1. + fP3*fP3);
423 fC43 += theta2*fP3*fP4*(1. + fP3*fP3);
424 fC44 += theta2*fP3*fP4*fP3*fP4;
427 //Energy losses************************
428 if (x0!=0. && beta2<1) {
430 Double_t dE=Bethe(p/mass)*d;
431 Double_t e=TMath::Sqrt(p2 + mass*mass);
432 if ( TMath::Abs(dE) > 0.3*e ) return kFALSE; //30% energy loss is too much!
435 // Approximate energy loss fluctuation (M.Ivanov)
436 const Double_t knst=0.07; // To be tuned.
437 Double_t sigmadE=knst*TMath::Sqrt(TMath::Abs(dE));
438 fC44+=((sigmadE*e/p2*fP4)*(sigmadE*e/p2*fP4));
445 Double_t AliExternalTrackParam::BetheBlochSolid(Double_t bg) {
446 //------------------------------------------------------------------
447 // This is an approximation of the Bethe-Bloch formula,
448 // reasonable for solid materials.
449 // All the parameters are, in fact, for Si.
450 // The returned value is in [GeV]
451 //------------------------------------------------------------------
453 return AliMathBase::BetheBlochGeant(bg);
456 Double_t AliExternalTrackParam::BetheBlochGas(Double_t bg) {
457 //------------------------------------------------------------------
458 // This is an approximation of the Bethe-Bloch formula,
459 // reasonable for gas materials.
460 // All the parameters are, in fact, for Ne.
461 // The returned value is in [GeV]
462 //------------------------------------------------------------------
464 const Double_t rho = 0.9e-3;
465 const Double_t x0 = 2.;
466 const Double_t x1 = 4.;
467 const Double_t mI = 140.e-9;
468 const Double_t mZA = 0.49555;
470 return AliMathBase::BetheBlochGeant(bg,rho,x0,x1,mI,mZA);
473 Bool_t AliExternalTrackParam::Rotate(Double_t alpha) {
474 //------------------------------------------------------------------
475 // Transform this track to the local coord. system rotated
476 // by angle "alpha" (rad) with respect to the global coord. system.
477 //------------------------------------------------------------------
478 if (TMath::Abs(fP[2]) >= kAlmost1) {
479 AliError(Form("Precondition is not satisfied: |sin(phi)|>1 ! %f",fP[2]));
483 if (alpha < -TMath::Pi()) alpha += 2*TMath::Pi();
484 else if (alpha >= TMath::Pi()) alpha -= 2*TMath::Pi();
488 Double_t &fC00=fC[0];
489 Double_t &fC10=fC[1];
490 Double_t &fC20=fC[3];
491 Double_t &fC21=fC[4];
492 Double_t &fC22=fC[5];
493 Double_t &fC30=fC[6];
494 Double_t &fC32=fC[8];
495 Double_t &fC40=fC[10];
496 Double_t &fC42=fC[12];
499 Double_t ca=TMath::Cos(alpha-fAlpha), sa=TMath::Sin(alpha-fAlpha);
500 Double_t sf=fP2, cf=TMath::Sqrt(1.- fP2*fP2);
502 Double_t tmp=sf*ca - cf*sa;
503 if (TMath::Abs(tmp) >= kAlmost1) return kFALSE;
510 if (TMath::Abs(cf)<kAlmost0) {
511 AliError(Form("Too small cosine value %f",cf));
515 Double_t rr=(ca+sf/cf*sa);
530 Bool_t AliExternalTrackParam::PropagateTo(Double_t xk, Double_t b) {
531 //----------------------------------------------------------------
532 // Propagate this track to the plane X=xk (cm) in the field "b" (kG)
533 //----------------------------------------------------------------
535 if (TMath::Abs(dx)<=kAlmost0) return kTRUE;
537 Double_t crv=GetC(b);
538 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
540 Double_t f1=fP[2], f2=f1 + crv*dx;
541 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
542 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
544 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
547 &fC10=fC[1], &fC11=fC[2],
548 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
549 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
550 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
552 Double_t r1=TMath::Sqrt(1.- f1*f1), r2=TMath::Sqrt(1.- f2*f2);
555 fP0 += dx*(f1+f2)/(r1+r2);
556 fP1 += dx*(r2 + f2*(f1+f2)/(r1+r2))*fP3; // Many thanks to P.Hristov !
561 Double_t f02= dx/(r1*r1*r1); Double_t cc=crv/fP4;
562 Double_t f04=0.5*dx*dx/(r1*r1*r1); f04*=cc;
563 Double_t f12= dx*fP3*f1/(r1*r1*r1);
564 Double_t f14=0.5*dx*dx*fP3*f1/(r1*r1*r1); f14*=cc;
566 Double_t f24= dx; f24*=cc;
569 Double_t b00=f02*fC20 + f04*fC40, b01=f12*fC20 + f14*fC40 + f13*fC30;
570 Double_t b02=f24*fC40;
571 Double_t b10=f02*fC21 + f04*fC41, b11=f12*fC21 + f14*fC41 + f13*fC31;
572 Double_t b12=f24*fC41;
573 Double_t b20=f02*fC22 + f04*fC42, b21=f12*fC22 + f14*fC42 + f13*fC32;
574 Double_t b22=f24*fC42;
575 Double_t b40=f02*fC42 + f04*fC44, b41=f12*fC42 + f14*fC44 + f13*fC43;
576 Double_t b42=f24*fC44;
577 Double_t b30=f02*fC32 + f04*fC43, b31=f12*fC32 + f14*fC43 + f13*fC33;
578 Double_t b32=f24*fC43;
581 Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a02=f02*b22+f04*b42;
582 Double_t a11=f12*b21+f14*b41+f13*b31,a12=f12*b22+f14*b42+f13*b32;
583 Double_t a22=f24*b42;
585 //F*C*Ft = C + (b + bt + a)
586 fC00 += b00 + b00 + a00;
587 fC10 += b10 + b01 + a01;
588 fC20 += b20 + b02 + a02;
591 fC11 += b11 + b11 + a11;
592 fC21 += b21 + b12 + a12;
595 fC22 += b22 + b22 + a22;
602 void AliExternalTrackParam::Propagate(Double_t len, Double_t x[3],
603 Double_t p[3], Double_t bz) const {
604 //+++++++++++++++++++++++++++++++++++++++++
605 // Origin: K. Shileev (Kirill.Shileev@cern.ch)
606 // Extrapolate track along simple helix in magnetic field
607 // Arguments: len -distance alogn helix, [cm]
608 // bz - mag field, [kGaus]
609 // Returns: x and p contain extrapolated positon and momentum
610 // The momentum returned for straight-line tracks is meaningless !
611 //+++++++++++++++++++++++++++++++++++++++++
614 if (OneOverPt() < kAlmost0 || TMath::Abs(bz) < kAlmost0Field ){ //straight-line tracks
615 Double_t unit[3]; GetDirection(unit);
620 p[0]=unit[0]/kAlmost0;
621 p[1]=unit[1]/kAlmost0;
622 p[2]=unit[2]/kAlmost0;
626 Double_t a = -kB2C*bz*GetSign();
628 x[0] += p[0]*TMath::Sin(rho*len)/a - p[1]*(1-TMath::Cos(rho*len))/a;
629 x[1] += p[1]*TMath::Sin(rho*len)/a + p[0]*(1-TMath::Cos(rho*len))/a;
633 p[0] = p0 *TMath::Cos(rho*len) - p[1]*TMath::Sin(rho*len);
634 p[1] = p[1]*TMath::Cos(rho*len) + p0 *TMath::Sin(rho*len);
638 Bool_t AliExternalTrackParam::Intersect(Double_t pnt[3], Double_t norm[3],
640 //+++++++++++++++++++++++++++++++++++++++++
641 // Origin: K. Shileev (Kirill.Shileev@cern.ch)
642 // Finds point of intersection (if exists) of the helix with the plane.
643 // Stores result in fX and fP.
644 // Arguments: planePoint,planeNorm - the plane defined by any plane's point
645 // and vector, normal to the plane
646 // Returns: kTrue if helix intersects the plane, kFALSE otherwise.
647 //+++++++++++++++++++++++++++++++++++++++++
648 Double_t x0[3]; GetXYZ(x0); //get track position in MARS
650 //estimates initial helix length up to plane
652 (pnt[0]-x0[0])*norm[0] + (pnt[1]-x0[1])*norm[1] + (pnt[2]-x0[2])*norm[2];
653 Double_t dist=99999,distPrev=dist;
655 while(TMath::Abs(dist)>0.00001){
656 //calculates helix at the distance s from x0 ALONG the helix
659 //distance between current helix position and plane
660 dist=(x[0]-pnt[0])*norm[0]+(x[1]-pnt[1])*norm[1]+(x[2]-pnt[2])*norm[2];
662 if(TMath::Abs(dist) >= TMath::Abs(distPrev)) {return kFALSE;}
666 //on exit pnt is intersection point,norm is track vector at that point,
668 for (Int_t i=0; i<3; i++) {pnt[i]=x[i]; norm[i]=p[i];}
673 AliExternalTrackParam::GetPredictedChi2(Double_t p[2],Double_t cov[3]) const {
674 //----------------------------------------------------------------
675 // Estimate the chi2 of the space point "p" with the cov. matrix "cov"
676 //----------------------------------------------------------------
677 Double_t sdd = fC[0] + cov[0];
678 Double_t sdz = fC[1] + cov[1];
679 Double_t szz = fC[2] + cov[2];
680 Double_t det = sdd*szz - sdz*sdz;
682 if (TMath::Abs(det) < kAlmost0) return kVeryBig;
684 Double_t d = fP[0] - p[0];
685 Double_t z = fP[1] - p[1];
687 return (d*szz*d - 2*d*sdz*z + z*sdd*z)/det;
690 Double_t AliExternalTrackParam::
691 GetPredictedChi2(Double_t p[3],Double_t covyz[3],Double_t covxyz[3]) const {
692 //----------------------------------------------------------------
693 // Estimate the chi2 of the 3D space point "p" and
694 // the full covariance matrix "covyz" and "covxyz"
696 // Cov(x,x) ... : covxyz[0]
697 // Cov(y,x) ... : covxyz[1] covyz[0]
698 // Cov(z,x) ... : covxyz[2] covyz[1] covyz[2]
699 //----------------------------------------------------------------
708 if (TMath::Abs(f) >= kAlmost1) return kVeryBig;
709 Double_t r=TMath::Sqrt(1.- f*f);
710 Double_t a=f/r, b=GetTgl()/r;
712 Double_t s2=333.*333.; //something reasonably big (cm^2)
715 v(0,0)= s2; v(0,1)= a*s2; v(0,2)= b*s2;;
716 v(1,0)=a*s2; v(1,1)=a*a*s2 + GetSigmaY2(); v(1,2)=a*b*s2 + GetSigmaZY();
717 v(2,0)=b*s2; v(2,1)=a*b*s2 + GetSigmaZY(); v(2,2)=b*b*s2 + GetSigmaZ2();
719 v(0,0)+=covxyz[0]; v(0,1)+=covxyz[1]; v(0,2)+=covxyz[2];
720 v(1,0)+=covxyz[1]; v(1,1)+=covyz[0]; v(1,2)+=covyz[1];
721 v(2,0)+=covxyz[2]; v(2,1)+=covyz[1]; v(2,2)+=covyz[2];
724 if (!v.IsValid()) return kVeryBig;
727 for (Int_t i = 0; i < 3; i++)
728 for (Int_t j = 0; j < 3; j++) chi2 += res[i]*res[j]*v(i,j);
735 Bool_t AliExternalTrackParam::
736 PropagateTo(Double_t p[3],Double_t covyz[3],Double_t covxyz[3],Double_t bz) {
737 //----------------------------------------------------------------
738 // Propagate this track to the plane
739 // the 3D space point "p" (with the covariance matrix "covyz" and "covxyz")
741 // The magnetic field is "bz" (kG)
743 // The track curvature and the change of the covariance matrix
744 // of the track parameters are negleted !
745 // (So the "step" should be small compared with 1/curvature)
746 //----------------------------------------------------------------
749 if (TMath::Abs(f) >= kAlmost1) return kFALSE;
750 Double_t r=TMath::Sqrt(1.- f*f);
751 Double_t a=f/r, b=GetTgl()/r;
753 Double_t s2=333.*333.; //something reasonably big (cm^2)
756 tV(0,0)= s2; tV(0,1)= a*s2; tV(0,2)= b*s2;
757 tV(1,0)=a*s2; tV(1,1)=a*a*s2; tV(1,2)=a*b*s2;
758 tV(2,0)=b*s2; tV(2,1)=a*b*s2; tV(2,2)=b*b*s2;
761 pV(0,0)=covxyz[0]; pV(0,1)=covxyz[1]; pV(0,2)=covxyz[2];
762 pV(1,0)=covxyz[1]; pV(1,1)=covyz[0]; pV(1,2)=covyz[1];
763 pV(2,0)=covxyz[2]; pV(2,1)=covyz[1]; pV(2,2)=covyz[2];
768 if (!tpV.IsValid()) return kFALSE;
770 TMatrixDSym pW(3),tW(3);
771 for (Int_t i=0; i<3; i++)
772 for (Int_t j=0; j<3; j++) {
774 for (Int_t k=0; k<3; k++) {
775 pW(i,j) += tV(i,k)*tpV(k,j);
776 tW(i,j) += pV(i,k)*tpV(k,j);
780 Double_t t[3] = {GetX(), GetY(), GetZ()};
783 for (Int_t i=0; i<3; i++) x += (tW(0,i)*t[i] + pW(0,i)*p[i]);
784 Double_t crv=GetC(bz);
785 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
787 if (TMath::Abs(f) >= kAlmost1) return kFALSE;
791 for (Int_t i=0; i<3; i++) fP[0] += (tW(1,i)*t[i] + pW(1,i)*p[i]);
793 for (Int_t i=0; i<3; i++) fP[1] += (tW(2,i)*t[i] + pW(2,i)*p[i]);
798 Double_t *AliExternalTrackParam::GetResiduals(
799 Double_t *p,Double_t *cov,Bool_t updated) const {
800 //------------------------------------------------------------------
801 // Returns the track residuals with the space point "p" having
802 // the covariance matrix "cov".
803 // If "updated" is kTRUE, the track parameters expected to be updated,
804 // otherwise they must be predicted.
805 //------------------------------------------------------------------
806 static Double_t res[2];
808 Double_t r00=cov[0], r01=cov[1], r11=cov[2];
810 r00-=fC[0]; r01-=fC[1]; r11-=fC[2];
812 r00+=fC[0]; r01+=fC[1]; r11+=fC[2];
814 Double_t det=r00*r11 - r01*r01;
816 if (TMath::Abs(det) < kAlmost0) return 0;
818 Double_t tmp=r00; r00=r11/det; r11=tmp/det;
820 if (r00 < 0.) return 0;
821 if (r11 < 0.) return 0;
823 Double_t dy = fP[0] - p[0];
824 Double_t dz = fP[1] - p[1];
826 res[0]=dy*TMath::Sqrt(r00);
827 res[1]=dz*TMath::Sqrt(r11);
832 Bool_t AliExternalTrackParam::Update(Double_t p[2], Double_t cov[3]) {
833 //------------------------------------------------------------------
834 // Update the track parameters with the space point "p" having
835 // the covariance matrix "cov"
836 //------------------------------------------------------------------
837 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
840 &fC10=fC[1], &fC11=fC[2],
841 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
842 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
843 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
845 Double_t r00=cov[0], r01=cov[1], r11=cov[2];
846 r00+=fC00; r01+=fC10; r11+=fC11;
847 Double_t det=r00*r11 - r01*r01;
849 if (TMath::Abs(det) < kAlmost0) return kFALSE;
852 Double_t tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;
854 Double_t k00=fC00*r00+fC10*r01, k01=fC00*r01+fC10*r11;
855 Double_t k10=fC10*r00+fC11*r01, k11=fC10*r01+fC11*r11;
856 Double_t k20=fC20*r00+fC21*r01, k21=fC20*r01+fC21*r11;
857 Double_t k30=fC30*r00+fC31*r01, k31=fC30*r01+fC31*r11;
858 Double_t k40=fC40*r00+fC41*r01, k41=fC40*r01+fC41*r11;
860 Double_t dy=p[0] - fP0, dz=p[1] - fP1;
861 Double_t sf=fP2 + k20*dy + k21*dz;
862 if (TMath::Abs(sf) > kAlmost1) return kFALSE;
864 fP0 += k00*dy + k01*dz;
865 fP1 += k10*dy + k11*dz;
867 fP3 += k30*dy + k31*dz;
868 fP4 += k40*dy + k41*dz;
870 Double_t c01=fC10, c02=fC20, c03=fC30, c04=fC40;
871 Double_t c12=fC21, c13=fC31, c14=fC41;
873 fC00-=k00*fC00+k01*fC10; fC10-=k00*c01+k01*fC11;
874 fC20-=k00*c02+k01*c12; fC30-=k00*c03+k01*c13;
875 fC40-=k00*c04+k01*c14;
877 fC11-=k10*c01+k11*fC11;
878 fC21-=k10*c02+k11*c12; fC31-=k10*c03+k11*c13;
879 fC41-=k10*c04+k11*c14;
881 fC22-=k20*c02+k21*c12; fC32-=k20*c03+k21*c13;
882 fC42-=k20*c04+k21*c14;
884 fC33-=k30*c03+k31*c13;
885 fC43-=k30*c04+k31*c14;
887 fC44-=k40*c04+k41*c14;
893 AliExternalTrackParam::GetHelixParameters(Double_t hlx[6], Double_t b) const {
894 //--------------------------------------------------------------------
895 // External track parameters -> helix parameters
896 // "b" - magnetic field (kG)
897 //--------------------------------------------------------------------
898 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
900 hlx[0]=fP[0]; hlx[1]=fP[1]; hlx[2]=fP[2]; hlx[3]=fP[3];
902 hlx[5]=fX*cs - hlx[0]*sn; // x0
903 hlx[0]=fX*sn + hlx[0]*cs; // y0
905 hlx[2]=TMath::ASin(hlx[2]) + fAlpha; // phi0
911 static void Evaluate(const Double_t *h, Double_t t,
912 Double_t r[3], //radius vector
913 Double_t g[3], //first defivatives
914 Double_t gg[3]) //second derivatives
916 //--------------------------------------------------------------------
917 // Calculate position of a point on a track and some derivatives
918 //--------------------------------------------------------------------
919 Double_t phase=h[4]*t+h[2];
920 Double_t sn=TMath::Sin(phase), cs=TMath::Cos(phase);
922 r[0] = h[5] + (sn - h[6])/h[4];
923 r[1] = h[0] - (cs - h[7])/h[4];
924 r[2] = h[1] + h[3]*t;
926 g[0] = cs; g[1]=sn; g[2]=h[3];
928 gg[0]=-h[4]*sn; gg[1]=h[4]*cs; gg[2]=0.;
931 Double_t AliExternalTrackParam::GetDCA(const AliExternalTrackParam *p,
932 Double_t b, Double_t &xthis, Double_t &xp) const {
933 //------------------------------------------------------------
934 // Returns the (weighed !) distance of closest approach between
935 // this track and the track "p".
936 // Other returned values:
937 // xthis, xt - coordinates of tracks' reference planes at the DCA
938 //-----------------------------------------------------------
939 Double_t dy2=GetSigmaY2() + p->GetSigmaY2();
940 Double_t dz2=GetSigmaZ2() + p->GetSigmaZ2();
943 Double_t p1[8]; GetHelixParameters(p1,b);
944 p1[6]=TMath::Sin(p1[2]); p1[7]=TMath::Cos(p1[2]);
945 Double_t p2[8]; p->GetHelixParameters(p2,b);
946 p2[6]=TMath::Sin(p2[2]); p2[7]=TMath::Cos(p2[2]);
949 Double_t r1[3],g1[3],gg1[3]; Double_t t1=0.;
950 Evaluate(p1,t1,r1,g1,gg1);
951 Double_t r2[3],g2[3],gg2[3]; Double_t t2=0.;
952 Evaluate(p2,t2,r2,g2,gg2);
954 Double_t dx=r2[0]-r1[0], dy=r2[1]-r1[1], dz=r2[2]-r1[2];
955 Double_t dm=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
959 Double_t gt1=-(dx*g1[0]/dx2 + dy*g1[1]/dy2 + dz*g1[2]/dz2);
960 Double_t gt2=+(dx*g2[0]/dx2 + dy*g2[1]/dy2 + dz*g2[2]/dz2);
961 Double_t h11=(g1[0]*g1[0] - dx*gg1[0])/dx2 +
962 (g1[1]*g1[1] - dy*gg1[1])/dy2 +
963 (g1[2]*g1[2] - dz*gg1[2])/dz2;
964 Double_t h22=(g2[0]*g2[0] + dx*gg2[0])/dx2 +
965 (g2[1]*g2[1] + dy*gg2[1])/dy2 +
966 (g2[2]*g2[2] + dz*gg2[2])/dz2;
967 Double_t h12=-(g1[0]*g2[0]/dx2 + g1[1]*g2[1]/dy2 + g1[2]*g2[2]/dz2);
969 Double_t det=h11*h22-h12*h12;
972 if (TMath::Abs(det)<1.e-33) {
973 //(quasi)singular Hessian
976 dt1=-(gt1*h22 - gt2*h12)/det;
977 dt2=-(h11*gt2 - h12*gt1)/det;
980 if ((dt1*gt1+dt2*gt2)>0) {dt1=-dt1; dt2=-dt2;}
982 //check delta(phase1) ?
983 //check delta(phase2) ?
985 if (TMath::Abs(dt1)/(TMath::Abs(t1)+1.e-3) < 1.e-4)
986 if (TMath::Abs(dt2)/(TMath::Abs(t2)+1.e-3) < 1.e-4) {
987 if ((gt1*gt1+gt2*gt2) > 1.e-4/dy2/dy2)
988 AliDebug(1," stopped at not a stationary point !");
989 Double_t lmb=h11+h22; lmb=lmb-TMath::Sqrt(lmb*lmb-4*det);
991 AliDebug(1," stopped at not a minimum !");
996 for (Int_t div=1 ; ; div*=2) {
997 Evaluate(p1,t1+dt1,r1,g1,gg1);
998 Evaluate(p2,t2+dt2,r2,g2,gg2);
999 dx=r2[0]-r1[0]; dy=r2[1]-r1[1]; dz=r2[2]-r1[2];
1000 dd=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
1004 AliDebug(1," overshoot !"); break;
1014 if (max<=0) AliDebug(1," too many iterations !");
1016 Double_t cs=TMath::Cos(GetAlpha());
1017 Double_t sn=TMath::Sin(GetAlpha());
1018 xthis=r1[0]*cs + r1[1]*sn;
1020 cs=TMath::Cos(p->GetAlpha());
1021 sn=TMath::Sin(p->GetAlpha());
1022 xp=r2[0]*cs + r2[1]*sn;
1024 return TMath::Sqrt(dm*TMath::Sqrt(dy2*dz2));
1027 Double_t AliExternalTrackParam::
1028 PropagateToDCA(AliExternalTrackParam *p, Double_t b) {
1029 //--------------------------------------------------------------
1030 // Propagates this track and the argument track to the position of the
1031 // distance of closest approach.
1032 // Returns the (weighed !) distance of closest approach.
1033 //--------------------------------------------------------------
1035 Double_t dca=GetDCA(p,b,xthis,xp);
1037 if (!PropagateTo(xthis,b)) {
1038 //AliWarning(" propagation failed !");
1042 if (!p->PropagateTo(xp,b)) {
1043 //AliWarning(" propagation failed !";
1051 Bool_t AliExternalTrackParam::PropagateToDCA(const AliVVertex *vtx,
1052 Double_t b, Double_t maxd, Double_t dz[2], Double_t covar[3]) {
1054 // Propagate this track to the DCA to vertex "vtx",
1055 // if the (rough) transverse impact parameter is not bigger then "maxd".
1056 // Magnetic field is "b" (kG).
1058 // a) The track gets extapolated to the DCA to the vertex.
1059 // b) The impact parameters and their covariance matrix are calculated.
1061 // In the case of success, the returned value is kTRUE
1062 // (otherwise, it's kFALSE)
1064 Double_t alpha=GetAlpha();
1065 Double_t sn=TMath::Sin(alpha), cs=TMath::Cos(alpha);
1066 Double_t x=GetX(), y=GetParameter()[0], snp=GetParameter()[2];
1067 Double_t xv= vtx->GetX()*cs + vtx->GetY()*sn;
1068 Double_t yv=-vtx->GetX()*sn + vtx->GetY()*cs, zv=vtx->GetZ();
1071 //Estimate the impact parameter neglecting the track curvature
1072 Double_t d=TMath::Abs(x*snp - y*TMath::Sqrt(1.- snp*snp));
1073 if (d > maxd) return kFALSE;
1075 //Propagate to the DCA
1076 Double_t crv=kB2C*b*GetParameter()[4];
1077 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1079 Double_t tgfv=-(crv*x - snp)/(crv*y + TMath::Sqrt(1.-snp*snp));
1080 sn=tgfv/TMath::Sqrt(1.+ tgfv*tgfv); cs=TMath::Sqrt(1.- sn*sn);
1081 if (TMath::Abs(tgfv)>0.) cs = sn/tgfv;
1085 yv=-xv*sn + yv*cs; xv=x;
1087 if (!Propagate(alpha+TMath::ASin(sn),xv,b)) return kFALSE;
1089 if (dz==0) return kTRUE;
1090 dz[0] = GetParameter()[0] - yv;
1091 dz[1] = GetParameter()[1] - zv;
1093 if (covar==0) return kTRUE;
1094 Double_t cov[6]; vtx->GetCovarianceMatrix(cov);
1096 //***** Improvements by A.Dainese
1097 alpha=GetAlpha(); sn=TMath::Sin(alpha); cs=TMath::Cos(alpha);
1098 Double_t s2ylocvtx = cov[0]*sn*sn + cov[2]*cs*cs - 2.*cov[1]*cs*sn;
1099 covar[0] = GetCovariance()[0] + s2ylocvtx; // neglecting correlations
1100 covar[1] = GetCovariance()[1]; // between (x,y) and z
1101 covar[2] = GetCovariance()[2] + cov[5]; // in vertex's covariance matrix
1108 void AliExternalTrackParam::GetDirection(Double_t d[3]) const {
1109 //----------------------------------------------------------------
1110 // This function returns a unit vector along the track direction
1111 // in the global coordinate system.
1112 //----------------------------------------------------------------
1113 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1115 Double_t csp =TMath::Sqrt((1.- snp)*(1.+snp));
1116 Double_t norm=TMath::Sqrt(1.+ fP[3]*fP[3]);
1117 d[0]=(csp*cs - snp*sn)/norm;
1118 d[1]=(snp*cs + csp*sn)/norm;
1122 Bool_t AliExternalTrackParam::GetPxPyPz(Double_t p[3]) const {
1123 //---------------------------------------------------------------------
1124 // This function returns the global track momentum components
1125 // Results for (nearly) straight tracks are meaningless !
1126 //---------------------------------------------------------------------
1127 p[0]=fP[4]; p[1]=fP[2]; p[2]=fP[3];
1128 return Local2GlobalMomentum(p,fAlpha);
1131 Double_t AliExternalTrackParam::Px() const {
1132 //---------------------------------------------------------------------
1133 // Returns x-component of momentum
1134 // Result for (nearly) straight tracks is meaningless !
1135 //---------------------------------------------------------------------
1137 Double_t p[3]={kVeryBig,kVeryBig,kVeryBig};
1143 Double_t AliExternalTrackParam::Py() const {
1144 //---------------------------------------------------------------------
1145 // Returns y-component of momentum
1146 // Result for (nearly) straight tracks is meaningless !
1147 //---------------------------------------------------------------------
1149 Double_t p[3]={kVeryBig,kVeryBig,kVeryBig};
1155 Double_t AliExternalTrackParam::Pz() const {
1156 //---------------------------------------------------------------------
1157 // Returns z-component of momentum
1158 // Result for (nearly) straight tracks is meaningless !
1159 //---------------------------------------------------------------------
1161 Double_t p[3]={kVeryBig,kVeryBig,kVeryBig};
1167 Double_t AliExternalTrackParam::Xv() const {
1168 //---------------------------------------------------------------------
1169 // Returns x-component of first track point
1170 //---------------------------------------------------------------------
1172 Double_t r[3]={0.,0.,0.};
1178 Double_t AliExternalTrackParam::Yv() const {
1179 //---------------------------------------------------------------------
1180 // Returns y-component of first track point
1181 //---------------------------------------------------------------------
1183 Double_t r[3]={0.,0.,0.};
1189 Double_t AliExternalTrackParam::Zv() const {
1190 //---------------------------------------------------------------------
1191 // Returns z-component of first track point
1192 //---------------------------------------------------------------------
1194 Double_t r[3]={0.,0.,0.};
1200 Double_t AliExternalTrackParam::Theta() const {
1201 // return theta angle of momentum
1203 return 0.5*TMath::Pi() - TMath::ATan(fP[3]);
1206 Double_t AliExternalTrackParam::Phi() const {
1207 //---------------------------------------------------------------------
1208 // Returns the azimuthal angle of momentum
1210 //---------------------------------------------------------------------
1212 Double_t phi=TMath::ASin(fP[2]) + fAlpha;
1213 if (phi<0.) phi+=2.*TMath::Pi();
1214 else if (phi>=2.*TMath::Pi()) phi-=2.*TMath::Pi();
1219 Double_t AliExternalTrackParam::M() const {
1220 // return particle mass
1222 // No mass information available so far.
1223 // Redifine in derived class!
1228 Double_t AliExternalTrackParam::E() const {
1229 // return particle energy
1231 // No PID information available so far.
1232 // Redifine in derived class!
1237 Double_t AliExternalTrackParam::Eta() const {
1238 // return pseudorapidity
1240 return -TMath::Log(TMath::Tan(0.5 * Theta()));
1243 Double_t AliExternalTrackParam::Y() const {
1246 // No PID information available so far.
1247 // Redifine in derived class!
1252 Bool_t AliExternalTrackParam::GetXYZ(Double_t *r) const {
1253 //---------------------------------------------------------------------
1254 // This function returns the global track position
1255 //---------------------------------------------------------------------
1256 r[0]=fX; r[1]=fP[0]; r[2]=fP[1];
1257 return Local2GlobalPosition(r,fAlpha);
1260 Bool_t AliExternalTrackParam::GetCovarianceXYZPxPyPz(Double_t cv[21]) const {
1261 //---------------------------------------------------------------------
1262 // This function returns the global covariance matrix of the track params
1264 // Cov(x,x) ... : cv[0]
1265 // Cov(y,x) ... : cv[1] cv[2]
1266 // Cov(z,x) ... : cv[3] cv[4] cv[5]
1267 // Cov(px,x)... : cv[6] cv[7] cv[8] cv[9]
1268 // Cov(py,x)... : cv[10] cv[11] cv[12] cv[13] cv[14]
1269 // Cov(pz,x)... : cv[15] cv[16] cv[17] cv[18] cv[19] cv[20]
1271 // Results for (nearly) straight tracks are meaningless !
1272 //---------------------------------------------------------------------
1273 if (TMath::Abs(fP[4])<=kAlmost0) {
1274 for (Int_t i=0; i<21; i++) cv[i]=0.;
1277 if (TMath::Abs(fP[2]) > kAlmost1) {
1278 for (Int_t i=0; i<21; i++) cv[i]=0.;
1281 Double_t pt=1./TMath::Abs(fP[4]);
1282 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
1283 Double_t r=TMath::Sqrt((1.-fP[2])*(1.+fP[2]));
1285 Double_t m00=-sn, m10=cs;
1286 Double_t m23=-pt*(sn + fP[2]*cs/r), m43=-pt*pt*(r*cs - fP[2]*sn);
1287 Double_t m24= pt*(cs - fP[2]*sn/r), m44=-pt*pt*(r*sn + fP[2]*cs);
1288 Double_t m35=pt, m45=-pt*pt*fP[3];
1294 cv[0 ] = fC[0]*m00*m00;
1295 cv[1 ] = fC[0]*m00*m10;
1296 cv[2 ] = fC[0]*m10*m10;
1300 cv[6 ] = m00*(fC[3]*m23 + fC[10]*m43);
1301 cv[7 ] = m10*(fC[3]*m23 + fC[10]*m43);
1302 cv[8 ] = fC[4]*m23 + fC[11]*m43;
1303 cv[9 ] = m23*(fC[5]*m23 + fC[12]*m43) + m43*(fC[12]*m23 + fC[14]*m43);
1304 cv[10] = m00*(fC[3]*m24 + fC[10]*m44);
1305 cv[11] = m10*(fC[3]*m24 + fC[10]*m44);
1306 cv[12] = fC[4]*m24 + fC[11]*m44;
1307 cv[13] = m23*(fC[5]*m24 + fC[12]*m44) + m43*(fC[12]*m24 + fC[14]*m44);
1308 cv[14] = m24*(fC[5]*m24 + fC[12]*m44) + m44*(fC[12]*m24 + fC[14]*m44);
1309 cv[15] = m00*(fC[6]*m35 + fC[10]*m45);
1310 cv[16] = m10*(fC[6]*m35 + fC[10]*m45);
1311 cv[17] = fC[7]*m35 + fC[11]*m45;
1312 cv[18] = m23*(fC[8]*m35 + fC[12]*m45) + m43*(fC[13]*m35 + fC[14]*m45);
1313 cv[19] = m24*(fC[8]*m35 + fC[12]*m45) + m44*(fC[13]*m35 + fC[14]*m45);
1314 cv[20] = m35*(fC[9]*m35 + fC[13]*m45) + m45*(fC[13]*m35 + fC[14]*m45);
1321 AliExternalTrackParam::GetPxPyPzAt(Double_t x, Double_t b, Double_t *p) const {
1322 //---------------------------------------------------------------------
1323 // This function returns the global track momentum extrapolated to
1324 // the radial position "x" (cm) in the magnetic field "b" (kG)
1325 //---------------------------------------------------------------------
1327 p[1]=fP[2]+(x-fX)*GetC(b);
1329 return Local2GlobalMomentum(p,fAlpha);
1333 AliExternalTrackParam::GetYAt(Double_t x, Double_t b, Double_t &y) const {
1334 //---------------------------------------------------------------------
1335 // This function returns the local Y-coordinate of the intersection
1336 // point between this track and the reference plane "x" (cm).
1337 // Magnetic field "b" (kG)
1338 //---------------------------------------------------------------------
1340 if(TMath::Abs(dx)<=kAlmost0) {y=fP[0]; return kTRUE;}
1342 Double_t f1=fP[2], f2=f1 + dx*GetC(b);
1344 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1345 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1347 Double_t r1=TMath::Sqrt(1.- f1*f1), r2=TMath::Sqrt(1.- f2*f2);
1348 y = fP[0] + dx*(f1+f2)/(r1+r2);
1353 AliExternalTrackParam::GetZAt(Double_t x, Double_t b, Double_t &z) const {
1354 //---------------------------------------------------------------------
1355 // This function returns the local Z-coordinate of the intersection
1356 // point between this track and the reference plane "x" (cm).
1357 // Magnetic field "b" (kG)
1358 //---------------------------------------------------------------------
1360 if(TMath::Abs(dx)<=kAlmost0) {z=fP[1]; return kTRUE;}
1362 Double_t f1=fP[2], f2=f1 + dx*fP[4]*b*kB2C;
1364 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1365 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1367 Double_t r1=sqrt(1.- f1*f1), r2=sqrt(1.- f2*f2);
1368 z = fP[1] + dx*(r2 + f2*(f1+f2)/(r1+r2))*fP[3]; // Many thanks to P.Hristov !
1373 AliExternalTrackParam::GetXYZAt(Double_t x, Double_t b, Double_t *r) const {
1374 //---------------------------------------------------------------------
1375 // This function returns the global track position extrapolated to
1376 // the radial position "x" (cm) in the magnetic field "b" (kG)
1377 //---------------------------------------------------------------------
1379 if(TMath::Abs(dx)<=kAlmost0) return GetXYZ(r);
1381 Double_t f1=fP[2], f2=f1 + dx*GetC(b);
1383 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
1384 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
1386 Double_t r1=TMath::Sqrt(1.- f1*f1), r2=TMath::Sqrt(1.- f2*f2);
1388 r[1] = fP[0] + dx*(f1+f2)/(r1+r2);
1389 r[2] = fP[1] + dx*(r2 + f2*(f1+f2)/(r1+r2))*fP[3];//Thanks to Andrea & Peter
1391 return Local2GlobalPosition(r,fAlpha);
1394 //_____________________________________________________________________________
1395 void AliExternalTrackParam::Print(Option_t* /*option*/) const
1397 // print the parameters and the covariance matrix
1399 printf("AliExternalTrackParam: x = %-12g alpha = %-12g\n", fX, fAlpha);
1400 printf(" parameters: %12g %12g %12g %12g %12g\n",
1401 fP[0], fP[1], fP[2], fP[3], fP[4]);
1402 printf(" covariance: %12g\n", fC[0]);
1403 printf(" %12g %12g\n", fC[1], fC[2]);
1404 printf(" %12g %12g %12g\n", fC[3], fC[4], fC[5]);
1405 printf(" %12g %12g %12g %12g\n",
1406 fC[6], fC[7], fC[8], fC[9]);
1407 printf(" %12g %12g %12g %12g %12g\n",
1408 fC[10], fC[11], fC[12], fC[13], fC[14]);
1411 Double_t AliExternalTrackParam::GetSnpAt(Double_t x,Double_t b) const {
1413 // Get sinus at given x
1415 Double_t crv=GetC(b);
1416 if (TMath::Abs(b) < kAlmost0Field) crv=0.;
1418 Double_t res = fP[2]+dx*crv;
1422 Bool_t AliExternalTrackParam::GetDistance(AliExternalTrackParam *param2, Double_t x, Double_t dist[3], Double_t bz){
1423 //------------------------------------------------------------------------
1424 // Get the distance between two tracks at the local position x
1425 // working in the local frame of this track.
1426 // Origin : Marian.Ivanov@cern.ch
1427 //-----------------------------------------------------------------------
1431 if (!GetYAt(x,bz,xyz[1])) return kFALSE;
1432 if (!GetZAt(x,bz,xyz[2])) return kFALSE;
1435 if (TMath::Abs(GetAlpha()-param2->GetAlpha())<kAlmost0){
1437 if (!param2->GetYAt(x,bz,xyz2[1])) return kFALSE;
1438 if (!param2->GetZAt(x,bz,xyz2[2])) return kFALSE;
1442 Double_t dfi = param2->GetAlpha()-GetAlpha();
1443 Double_t ca = TMath::Cos(dfi), sa = TMath::Sin(dfi);
1444 xyz2[0] = xyz[0]*ca+xyz[1]*sa;
1445 xyz2[1] = -xyz[0]*sa+xyz[1]*ca;
1448 if (!param2->GetYAt(xyz2[0],bz,xyz1[1])) return kFALSE;
1449 if (!param2->GetZAt(xyz2[0],bz,xyz1[2])) return kFALSE;
1451 xyz2[0] = xyz1[0]*ca-xyz1[1]*sa;
1452 xyz2[1] = +xyz1[0]*sa+xyz1[1]*ca;
1455 dist[0] = xyz[0]-xyz2[0];
1456 dist[1] = xyz[1]-xyz2[1];
1457 dist[2] = xyz[2]-xyz2[2];
1464 // Draw functionality.
1465 // Origin: Marian Ivanov, Marian.Ivanov@cern.ch
1468 void AliExternalTrackParam::DrawTrack(Float_t magf, Float_t minR, Float_t maxR, Float_t stepR){
1472 if (minR>maxR) return ;
1473 if (stepR<=0) return ;
1474 Int_t npoints = TMath::Nint((maxR-minR)/stepR)+1;
1475 if (npoints<1) return;
1476 TPolyMarker3D *polymarker = new TPolyMarker3D(npoints);
1477 FillPolymarker(polymarker, magf,minR,maxR,stepR);
1482 void AliExternalTrackParam::FillPolymarker(TPolyMarker3D *pol, Float_t magF, Float_t minR, Float_t maxR, Float_t stepR){
1484 // Fill points in the polymarker
1487 for (Double_t r=minR; r<maxR; r+=stepR){
1489 GetXYZAt(r,magF,point);
1490 pol->SetPoint(counter,point[0],point[1], point[2]);
1491 printf("xyz\t%f\t%f\t%f\n",point[0], point[1],point[2]);
1496 Int_t AliExternalTrackParam::GetIndex(Int_t i, Int_t j) const {
1498 Int_t min = TMath::Min(i,j);
1499 Int_t max = TMath::Max(i,j);
1501 return min+(max+1)*max/2;