Removing obsolete TRD calls
[u/mrichter/AliRoot.git] / STEER / AliExternalTrackParam.cxx
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51ad6848 1/**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
3 * *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
6 * *
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 **************************************************************************/
15
16/* $Id$ */
17
18///////////////////////////////////////////////////////////////////////////////
19// //
49d13e89 20// Implementation of the external track parameterisation class. //
51ad6848 21// //
49d13e89 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 //
25// are implemented.
26// Origin: I.Belikov, CERN, Jouri.Belikov@cern.ch //
51ad6848 27///////////////////////////////////////////////////////////////////////////////
51ad6848 28#include "AliExternalTrackParam.h"
29#include "AliKalmanTrack.h"
5b77d93c 30#include "AliTracker.h"
edc97986 31#include "AliStrLine.h"
f76701bf 32#include "AliESDVertex.h"
5b77d93c 33
51ad6848 34
35ClassImp(AliExternalTrackParam)
36
51ad6848 37//_____________________________________________________________________________
90e48c0c 38AliExternalTrackParam::AliExternalTrackParam() :
90e48c0c 39 fX(0),
c9ec41e8 40 fAlpha(0)
51ad6848 41{
90e48c0c 42 //
43 // default constructor
44 //
c9ec41e8 45 for (Int_t i = 0; i < 5; i++) fP[i] = 0;
46 for (Int_t i = 0; i < 15; i++) fC[i] = 0;
51ad6848 47}
48
49//_____________________________________________________________________________
50AliExternalTrackParam::AliExternalTrackParam(Double_t x, Double_t alpha,
51 const Double_t param[5],
90e48c0c 52 const Double_t covar[15]) :
90e48c0c 53 fX(x),
c9ec41e8 54 fAlpha(alpha)
51ad6848 55{
90e48c0c 56 //
57 // create external track parameters from given arguments
58 //
c9ec41e8 59 for (Int_t i = 0; i < 5; i++) fP[i] = param[i];
60 for (Int_t i = 0; i < 15; i++) fC[i] = covar[i];
51ad6848 61}
62
90e48c0c 63//_____________________________________________________________________________
64AliExternalTrackParam::AliExternalTrackParam(const AliKalmanTrack& track) :
c9ec41e8 65 fAlpha(track.GetAlpha())
51ad6848 66{
67 //
68 //
c9ec41e8 69 track.GetExternalParameters(fX,fP);
70 track.GetExternalCovariance(fC);
51ad6848 71}
72
51ad6848 73//_____________________________________________________________________________
c9ec41e8 74void AliExternalTrackParam::Set(const AliKalmanTrack& track) {
75 //
76 //
77 fAlpha=track.GetAlpha();
78 track.GetExternalParameters(fX,fP);
79 track.GetExternalCovariance(fC);
51ad6848 80}
81
82//_____________________________________________________________________________
c9ec41e8 83void AliExternalTrackParam::Reset() {
84 fX=fAlpha=0.;
85 for (Int_t i = 0; i < 5; i++) fP[i] = 0;
86 for (Int_t i = 0; i < 15; i++) fC[i] = 0;
51ad6848 87}
88
c9ec41e8 89Double_t AliExternalTrackParam::GetP() const {
90 //---------------------------------------------------------------------
91 // This function returns the track momentum
92 // Results for (nearly) straight tracks are meaningless !
93 //---------------------------------------------------------------------
1d99986f 94 if (TMath::Abs(fP[4])<=0) return 1e+33;
c9ec41e8 95 return TMath::Sqrt(1.+ fP[3]*fP[3])/TMath::Abs(fP[4]);
51ad6848 96}
97
1d99986f 98Double_t AliExternalTrackParam::Get1P() const {
99 //---------------------------------------------------------------------
100 // This function returns the 1/(track momentum)
101 //---------------------------------------------------------------------
102 return TMath::Abs(fP[4])/TMath::Sqrt(1.+ fP[3]*fP[3]);
103}
104
c9ec41e8 105//_______________________________________________________________________
c7bafca9 106Double_t AliExternalTrackParam::GetD(Double_t x,Double_t y,Double_t b) const {
c9ec41e8 107 //------------------------------------------------------------------
108 // This function calculates the transverse impact parameter
109 // with respect to a point with global coordinates (x,y)
110 // in the magnetic field "b" (kG)
111 //------------------------------------------------------------------
49d13e89 112 Double_t rp4=kB2C*b*fP[4];
c9ec41e8 113
114 Double_t xt=fX, yt=fP[0];
115
116 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
117 Double_t a = x*cs + y*sn;
118 y = -x*sn + y*cs; x=a;
119 xt-=x; yt-=y;
120
121 sn=rp4*xt - fP[2]; cs=rp4*yt + TMath::Sqrt(1.- fP[2]*fP[2]);
122 a=2*(xt*fP[2] - yt*TMath::Sqrt(1.- fP[2]*fP[2]))-rp4*(xt*xt + yt*yt);
123 if (rp4<0) a=-a;
124 return a/(1 + TMath::Sqrt(sn*sn + cs*cs));
51ad6848 125}
126
49d13e89 127//_______________________________________________________________________
128Double_t AliExternalTrackParam::GetLinearD(Double_t xv,Double_t yv) const {
129 //------------------------------------------------------------------
130 // This function calculates the transverse impact parameter
131 // with respect to a point with global coordinates (xv,yv)
132 // neglecting the track curvature.
133 //------------------------------------------------------------------
134 Double_t sn=TMath::Sin(fAlpha), cs=TMath::Cos(fAlpha);
135 Double_t x= xv*cs + yv*sn;
136 Double_t y=-xv*sn + yv*cs;
137
138 Double_t d = (fX-x)*fP[2] - (fP[0]-y)*TMath::Sqrt(1.- fP[2]*fP[2]);
139
140 return d;
141}
142
c7bafca9 143Bool_t AliExternalTrackParam::
144CorrectForMaterial(Double_t d, Double_t x0, Double_t mass) {
145 //------------------------------------------------------------------
146 // This function corrects the track parameters for the crossed material
147 // "d" - the thickness (fraction of the radiation length)
148 // "x0" - the radiation length (g/cm^2)
149 // "mass" - the mass of this particle (GeV/c^2)
150 //------------------------------------------------------------------
151 Double_t &fP2=fP[2];
152 Double_t &fP3=fP[3];
153 Double_t &fP4=fP[4];
154
155 Double_t &fC22=fC[5];
156 Double_t &fC33=fC[9];
157 Double_t &fC43=fC[13];
158 Double_t &fC44=fC[14];
159
160 Double_t p2=(1.+ fP3*fP3)/(fP4*fP4);
161 Double_t beta2=p2/(p2 + mass*mass);
162 d*=TMath::Sqrt((1.+ fP3*fP3)/(1.- fP2*fP2));
163
164 //Multiple scattering******************
165 if (d!=0) {
166 Double_t theta2=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(d);
167 //Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*TMath::Abs(d)*9.36*2.33;
168 fC22 += theta2*(1.- fP2*fP2)*(1. + fP3*fP3);
169 fC33 += theta2*(1. + fP3*fP3)*(1. + fP3*fP3);
170 fC43 += theta2*fP3*fP4*(1. + fP3*fP3);
171 fC44 += theta2*fP3*fP4*fP3*fP4;
172 }
173
174 //Energy losses************************
175 if (x0!=0.) {
176 d*=x0;
177 Double_t dE=0.153e-3/beta2*(log(5940*beta2/(1-beta2)) - beta2)*d;
178 if (beta2/(1-beta2)>3.5*3.5)
179 dE=0.153e-3/beta2*(log(3.5*5940)+0.5*log(beta2/(1-beta2)) - beta2)*d;
180
181 fP4*=(1.- TMath::Sqrt(p2 + mass*mass)/p2*dE);
182 }
183
184 return kTRUE;
185}
186
49d13e89 187Bool_t AliExternalTrackParam::Rotate(Double_t alpha) {
188 //------------------------------------------------------------------
189 // Transform this track to the local coord. system rotated
190 // by angle "alpha" (rad) with respect to the global coord. system.
191 //------------------------------------------------------------------
192 if (alpha < -TMath::Pi()) alpha += 2*TMath::Pi();
193 else if (alpha >= TMath::Pi()) alpha -= 2*TMath::Pi();
194
195 Double_t &fP0=fP[0];
196 Double_t &fP2=fP[2];
197 Double_t &fC00=fC[0];
198 Double_t &fC10=fC[1];
199 Double_t &fC20=fC[3];
200 Double_t &fC21=fC[4];
201 Double_t &fC22=fC[5];
202 Double_t &fC30=fC[6];
203 Double_t &fC32=fC[8];
204 Double_t &fC40=fC[10];
205 Double_t &fC42=fC[12];
206
207 Double_t x=fX;
208 Double_t ca=TMath::Cos(alpha-fAlpha), sa=TMath::Sin(alpha-fAlpha);
209 Double_t sf=fP2, cf=TMath::Sqrt(1.- fP2*fP2);
210
211 fAlpha = alpha;
212 fX = x*ca + fP0*sa;
213 fP0= -x*sa + fP0*ca;
214 fP2= sf*ca - cf*sa;
215
216 Double_t rr=(ca+sf/cf*sa);
217
218 fC00 *= (ca*ca);
219 fC10 *= ca;
220 fC20 *= ca*rr;
221 fC21 *= rr;
222 fC22 *= rr*rr;
223 fC30 *= ca;
224 fC32 *= rr;
225 fC40 *= ca;
226 fC42 *= rr;
227
228 return kTRUE;
229}
230
231Bool_t AliExternalTrackParam::PropagateTo(Double_t xk, Double_t b) {
232 //----------------------------------------------------------------
233 // Propagate this track to the plane X=xk (cm) in the field "b" (kG)
234 //----------------------------------------------------------------
49d13e89 235 Double_t dx=xk-fX;
606833e7 236 if (TMath::Abs(dx)<=0) return kTRUE;
18ebc5ef 237
238 Double_t crv=kB2C*b*fP[4];
49d13e89 239 Double_t f1=fP[2], f2=f1 + crv*dx;
bbefa4c4 240 if (TMath::Abs(f1) >= kAlmost1) return kFALSE;
49d13e89 241 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
242
243 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
244 Double_t
245 &fC00=fC[0],
246 &fC10=fC[1], &fC11=fC[2],
247 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
248 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
249 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
250
251 Double_t r1=TMath::Sqrt(1.- f1*f1), r2=TMath::Sqrt(1.- f2*f2);
252
253 fX=xk;
254 fP0 += dx*(f1+f2)/(r1+r2);
18ebc5ef 255 fP1 += dx*(r2 + f2*(f1+f2)/(r1+r2))*fP3; // Many thanks to P.Hristov !
49d13e89 256 fP2 += dx*crv;
257
258 //f = F - 1
259
260 Double_t f02= dx/(r1*r1*r1); Double_t cc=crv/fP4;
261 Double_t f04=0.5*dx*dx/(r1*r1*r1); f04*=cc;
262 Double_t f12= dx*fP3*f1/(r1*r1*r1);
263 Double_t f14=0.5*dx*dx*fP3*f1/(r1*r1*r1); f14*=cc;
264 Double_t f13= dx/r1;
265 Double_t f24= dx; f24*=cc;
266
267 //b = C*ft
268 Double_t b00=f02*fC20 + f04*fC40, b01=f12*fC20 + f14*fC40 + f13*fC30;
269 Double_t b02=f24*fC40;
270 Double_t b10=f02*fC21 + f04*fC41, b11=f12*fC21 + f14*fC41 + f13*fC31;
271 Double_t b12=f24*fC41;
272 Double_t b20=f02*fC22 + f04*fC42, b21=f12*fC22 + f14*fC42 + f13*fC32;
273 Double_t b22=f24*fC42;
274 Double_t b40=f02*fC42 + f04*fC44, b41=f12*fC42 + f14*fC44 + f13*fC43;
275 Double_t b42=f24*fC44;
276 Double_t b30=f02*fC32 + f04*fC43, b31=f12*fC32 + f14*fC43 + f13*fC33;
277 Double_t b32=f24*fC43;
278
279 //a = f*b = f*C*ft
280 Double_t a00=f02*b20+f04*b40,a01=f02*b21+f04*b41,a02=f02*b22+f04*b42;
281 Double_t a11=f12*b21+f14*b41+f13*b31,a12=f12*b22+f14*b42+f13*b32;
282 Double_t a22=f24*b42;
283
284 //F*C*Ft = C + (b + bt + a)
285 fC00 += b00 + b00 + a00;
286 fC10 += b10 + b01 + a01;
287 fC20 += b20 + b02 + a02;
288 fC30 += b30;
289 fC40 += b40;
290 fC11 += b11 + b11 + a11;
291 fC21 += b21 + b12 + a12;
292 fC31 += b31;
293 fC41 += b41;
294 fC22 += b22 + b22 + a22;
295 fC32 += b32;
296 fC42 += b42;
297
298 return kTRUE;
299}
300
301Double_t
302AliExternalTrackParam::GetPredictedChi2(Double_t p[2],Double_t cov[3]) const {
303 //----------------------------------------------------------------
304 // Estimate the chi2 of the space point "p" with the cov. matrix "cov"
305 //----------------------------------------------------------------
306 Double_t sdd = fC[0] + cov[0];
307 Double_t sdz = fC[1] + cov[1];
308 Double_t szz = fC[2] + cov[2];
309 Double_t det = sdd*szz - sdz*sdz;
310
311 if (TMath::Abs(det) < kAlmost0) return kVeryBig;
312
313 Double_t d = fP[0] - p[0];
314 Double_t z = fP[1] - p[1];
315
316 return (d*szz*d - 2*d*sdz*z + z*sdd*z)/det;
317}
318
319Bool_t AliExternalTrackParam::Update(Double_t p[2], Double_t cov[3]) {
320 //------------------------------------------------------------------
321 // Update the track parameters with the space point "p" having
322 // the covariance matrix "cov"
323 //------------------------------------------------------------------
324 Double_t &fP0=fP[0], &fP1=fP[1], &fP2=fP[2], &fP3=fP[3], &fP4=fP[4];
325 Double_t
326 &fC00=fC[0],
327 &fC10=fC[1], &fC11=fC[2],
328 &fC20=fC[3], &fC21=fC[4], &fC22=fC[5],
329 &fC30=fC[6], &fC31=fC[7], &fC32=fC[8], &fC33=fC[9],
330 &fC40=fC[10], &fC41=fC[11], &fC42=fC[12], &fC43=fC[13], &fC44=fC[14];
331
332 Double_t r00=cov[0], r01=cov[1], r11=cov[2];
333 r00+=fC00; r01+=fC10; r11+=fC11;
334 Double_t det=r00*r11 - r01*r01;
335
336 if (TMath::Abs(det) < kAlmost0) return kFALSE;
337
338
339 Double_t tmp=r00; r00=r11/det; r11=tmp/det; r01=-r01/det;
340
341 Double_t k00=fC00*r00+fC10*r01, k01=fC00*r01+fC10*r11;
342 Double_t k10=fC10*r00+fC11*r01, k11=fC10*r01+fC11*r11;
343 Double_t k20=fC20*r00+fC21*r01, k21=fC20*r01+fC21*r11;
344 Double_t k30=fC30*r00+fC31*r01, k31=fC30*r01+fC31*r11;
345 Double_t k40=fC40*r00+fC41*r01, k41=fC40*r01+fC41*r11;
346
347 Double_t dy=p[0] - fP0, dz=p[1] - fP1;
348 Double_t sf=fP2 + k20*dy + k21*dz;
349 if (TMath::Abs(sf) > kAlmost1) return kFALSE;
350
351 fP0 += k00*dy + k01*dz;
352 fP1 += k10*dy + k11*dz;
353 fP2 = sf;
354 fP3 += k30*dy + k31*dz;
355 fP4 += k40*dy + k41*dz;
356
357 Double_t c01=fC10, c02=fC20, c03=fC30, c04=fC40;
358 Double_t c12=fC21, c13=fC31, c14=fC41;
359
360 fC00-=k00*fC00+k01*fC10; fC10-=k00*c01+k01*fC11;
361 fC20-=k00*c02+k01*c12; fC30-=k00*c03+k01*c13;
362 fC40-=k00*c04+k01*c14;
363
364 fC11-=k10*c01+k11*fC11;
365 fC21-=k10*c02+k11*c12; fC31-=k10*c03+k11*c13;
366 fC41-=k10*c04+k11*c14;
367
368 fC22-=k20*c02+k21*c12; fC32-=k20*c03+k21*c13;
369 fC42-=k20*c04+k21*c14;
370
371 fC33-=k30*c03+k31*c13;
372 fC43-=k30*c04+k31*c14;
373
374 fC44-=k40*c04+k41*c14;
375
376 return kTRUE;
377}
378
c7bafca9 379void
380AliExternalTrackParam::GetHelixParameters(Double_t hlx[6], Double_t b) const {
381 //--------------------------------------------------------------------
382 // External track parameters -> helix parameters
383 // "b" - magnetic field (kG)
384 //--------------------------------------------------------------------
385 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
386
387 hlx[0]=fP[0]; hlx[1]=fP[1]; hlx[2]=fP[2]; hlx[3]=fP[3]; hlx[4]=fP[4];
388
389 hlx[5]=fX*cs - hlx[0]*sn; // x0
390 hlx[0]=fX*sn + hlx[0]*cs; // y0
391//hlx[1]= // z0
392 hlx[2]=TMath::ASin(hlx[2]) + fAlpha; // phi0
393//hlx[3]= // tgl
394 hlx[4]=hlx[4]*kB2C*b; // C
395}
396
397
398static void Evaluate(const Double_t *h, Double_t t,
399 Double_t r[3], //radius vector
400 Double_t g[3], //first defivatives
401 Double_t gg[3]) //second derivatives
402{
403 //--------------------------------------------------------------------
404 // Calculate position of a point on a track and some derivatives
405 //--------------------------------------------------------------------
406 Double_t phase=h[4]*t+h[2];
407 Double_t sn=TMath::Sin(phase), cs=TMath::Cos(phase);
408
409 r[0] = h[5] + (sn - h[6])/h[4];
410 r[1] = h[0] - (cs - h[7])/h[4];
411 r[2] = h[1] + h[3]*t;
412
413 g[0] = cs; g[1]=sn; g[2]=h[3];
414
415 gg[0]=-h[4]*sn; gg[1]=h[4]*cs; gg[2]=0.;
416}
417
418Double_t AliExternalTrackParam::GetDCA(const AliExternalTrackParam *p,
419Double_t b, Double_t &xthis, Double_t &xp) const {
420 //------------------------------------------------------------
421 // Returns the (weighed !) distance of closest approach between
422 // this track and the track "p".
423 // Other returned values:
424 // xthis, xt - coordinates of tracks' reference planes at the DCA
425 //-----------------------------------------------------------
426 Double_t dy2=GetSigmaY2() + p->GetSigmaY2();
427 Double_t dz2=GetSigmaZ2() + p->GetSigmaZ2();
428 Double_t dx2=dy2;
429
430 //dx2=dy2=dz2=1.;
431
432 Double_t p1[8]; GetHelixParameters(p1,b);
433 p1[6]=TMath::Sin(p1[2]); p1[7]=TMath::Cos(p1[2]);
434 Double_t p2[8]; p->GetHelixParameters(p2,b);
435 p2[6]=TMath::Sin(p2[2]); p2[7]=TMath::Cos(p2[2]);
436
437
438 Double_t r1[3],g1[3],gg1[3]; Double_t t1=0.;
439 Evaluate(p1,t1,r1,g1,gg1);
440 Double_t r2[3],g2[3],gg2[3]; Double_t t2=0.;
441 Evaluate(p2,t2,r2,g2,gg2);
442
443 Double_t dx=r2[0]-r1[0], dy=r2[1]-r1[1], dz=r2[2]-r1[2];
444 Double_t dm=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
445
446 Int_t max=27;
447 while (max--) {
448 Double_t gt1=-(dx*g1[0]/dx2 + dy*g1[1]/dy2 + dz*g1[2]/dz2);
449 Double_t gt2=+(dx*g2[0]/dx2 + dy*g2[1]/dy2 + dz*g2[2]/dz2);
450 Double_t h11=(g1[0]*g1[0] - dx*gg1[0])/dx2 +
451 (g1[1]*g1[1] - dy*gg1[1])/dy2 +
452 (g1[2]*g1[2] - dz*gg1[2])/dz2;
453 Double_t h22=(g2[0]*g2[0] + dx*gg2[0])/dx2 +
454 (g2[1]*g2[1] + dy*gg2[1])/dy2 +
455 (g2[2]*g2[2] + dz*gg2[2])/dz2;
456 Double_t h12=-(g1[0]*g2[0]/dx2 + g1[1]*g2[1]/dy2 + g1[2]*g2[2]/dz2);
457
458 Double_t det=h11*h22-h12*h12;
459
460 Double_t dt1,dt2;
461 if (TMath::Abs(det)<1.e-33) {
462 //(quasi)singular Hessian
463 dt1=-gt1; dt2=-gt2;
464 } else {
465 dt1=-(gt1*h22 - gt2*h12)/det;
466 dt2=-(h11*gt2 - h12*gt1)/det;
467 }
468
469 if ((dt1*gt1+dt2*gt2)>0) {dt1=-dt1; dt2=-dt2;}
470
471 //check delta(phase1) ?
472 //check delta(phase2) ?
473
474 if (TMath::Abs(dt1)/(TMath::Abs(t1)+1.e-3) < 1.e-4)
475 if (TMath::Abs(dt2)/(TMath::Abs(t2)+1.e-3) < 1.e-4) {
476 if ((gt1*gt1+gt2*gt2) > 1.e-4/dy2/dy2)
477 AliWarning(" stopped at not a stationary point !");
478 Double_t lmb=h11+h22; lmb=lmb-TMath::Sqrt(lmb*lmb-4*det);
479 if (lmb < 0.)
480 AliWarning(" stopped at not a minimum !");
481 break;
482 }
483
484 Double_t dd=dm;
485 for (Int_t div=1 ; ; div*=2) {
486 Evaluate(p1,t1+dt1,r1,g1,gg1);
487 Evaluate(p2,t2+dt2,r2,g2,gg2);
488 dx=r2[0]-r1[0]; dy=r2[1]-r1[1]; dz=r2[2]-r1[2];
489 dd=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2;
490 if (dd<dm) break;
491 dt1*=0.5; dt2*=0.5;
492 if (div>512) {
493 AliWarning(" overshoot !"); break;
494 }
495 }
496 dm=dd;
497
498 t1+=dt1;
499 t2+=dt2;
500
501 }
502
503 if (max<=0) AliWarning(" too many iterations !");
504
505 Double_t cs=TMath::Cos(GetAlpha());
506 Double_t sn=TMath::Sin(GetAlpha());
507 xthis=r1[0]*cs + r1[1]*sn;
508
509 cs=TMath::Cos(p->GetAlpha());
510 sn=TMath::Sin(p->GetAlpha());
511 xp=r2[0]*cs + r2[1]*sn;
512
513 return TMath::Sqrt(dm*TMath::Sqrt(dy2*dz2));
514}
515
516Double_t AliExternalTrackParam::
517PropagateToDCA(AliExternalTrackParam *p, Double_t b) {
518 //--------------------------------------------------------------
519 // Propagates this track and the argument track to the position of the
520 // distance of closest approach.
521 // Returns the (weighed !) distance of closest approach.
522 //--------------------------------------------------------------
523 Double_t xthis,xp;
524 Double_t dca=GetDCA(p,b,xthis,xp);
525
526 if (!PropagateTo(xthis,b)) {
527 //AliWarning(" propagation failed !");
528 return 1e+33;
529 }
530
531 if (!p->PropagateTo(xp,b)) {
532 //AliWarning(" propagation failed !";
533 return 1e+33;
534 }
535
536 return dca;
537}
538
539
540
f76701bf 541
542Bool_t AliExternalTrackParam::PropagateToDCA(const AliESDVertex *vtx, Double_t b, Double_t maxd){
543 //
544 // Try to relate this track to the vertex "vtx",
545 // if the (rough) transverse impact parameter is not bigger then "maxd".
546 // Magnetic field is "b" (kG).
547 //
548 // a) The track gets extapolated to the DCA to the vertex.
549 // b) The impact parameters and their covariance matrix are calculated.
550 //
551 // In the case of success, the returned value is kTRUE
552 // (otherwise, it's kFALSE)
553 //
554 Double_t alpha=GetAlpha();
555 Double_t sn=TMath::Sin(alpha), cs=TMath::Cos(alpha);
556 Double_t x=GetX(), y=GetParameter()[0], snp=GetParameter()[2];
557 Double_t xv= vtx->GetXv()*cs + vtx->GetYv()*sn;
29fbcc93 558 Double_t yv=-vtx->GetXv()*sn + vtx->GetYv()*cs;
f76701bf 559 x-=xv; y-=yv;
560
561 //Estimate the impact parameter neglecting the track curvature
562 Double_t d=TMath::Abs(x*snp - y*TMath::Sqrt(1.- snp*snp));
563 if (d > maxd) return kFALSE;
564
565 //Propagate to the DCA
566 Double_t crv=0.299792458e-3*b*GetParameter()[4];
567 Double_t tgfv=-(crv*x - snp)/(crv*y + TMath::Sqrt(1.-snp*snp));
568 sn=tgfv/TMath::Sqrt(1.+ tgfv*tgfv); cs=TMath::Sqrt(1.- sn*sn);
569
570 x = xv*cs + yv*sn;
571 yv=-xv*sn + yv*cs; xv=x;
572
573 if (!Propagate(alpha+TMath::ASin(sn),xv,b)) return kFALSE;
29fbcc93 574 return kTRUE;
f76701bf 575}
576
577
578
579
c9ec41e8 580Bool_t Local2GlobalMomentum(Double_t p[3],Double_t alpha) {
581 //----------------------------------------------------------------
582 // This function performs local->global transformation of the
583 // track momentum.
584 // When called, the arguments are:
585 // p[0] = 1/pt of the track;
586 // p[1] = sine of local azim. angle of the track momentum;
587 // p[2] = tangent of the track momentum dip angle;
588 // alpha - rotation angle.
589 // The result is returned as:
590 // p[0] = px
591 // p[1] = py
592 // p[2] = pz
593 // Results for (nearly) straight tracks are meaningless !
594 //----------------------------------------------------------------
595 if (TMath::Abs(p[0])<=0) return kFALSE;
49d13e89 596 if (TMath::Abs(p[1])> kAlmost1) return kFALSE;
c9ec41e8 597
598 Double_t pt=1./TMath::Abs(p[0]);
599 Double_t cs=TMath::Cos(alpha), sn=TMath::Sin(alpha);
600 Double_t r=TMath::Sqrt(1 - p[1]*p[1]);
601 p[0]=pt*(r*cs - p[1]*sn); p[1]=pt*(p[1]*cs + r*sn); p[2]=pt*p[2];
a5e407e9 602
603 return kTRUE;
604}
605
c9ec41e8 606Bool_t Local2GlobalPosition(Double_t r[3],Double_t alpha) {
607 //----------------------------------------------------------------
608 // This function performs local->global transformation of the
609 // track position.
610 // When called, the arguments are:
611 // r[0] = local x
612 // r[1] = local y
613 // r[2] = local z
614 // alpha - rotation angle.
615 // The result is returned as:
616 // r[0] = global x
617 // r[1] = global y
618 // r[2] = global z
619 //----------------------------------------------------------------
620 Double_t cs=TMath::Cos(alpha), sn=TMath::Sin(alpha), x=r[0];
621 r[0]=x*cs - r[1]*sn; r[1]=x*sn + r[1]*cs;
a5e407e9 622
a5e407e9 623 return kTRUE;
51ad6848 624}
625
c9ec41e8 626Bool_t AliExternalTrackParam::GetPxPyPz(Double_t *p) const {
627 //---------------------------------------------------------------------
628 // This function returns the global track momentum components
629 // Results for (nearly) straight tracks are meaningless !
630 //---------------------------------------------------------------------
631 p[0]=fP[4]; p[1]=fP[2]; p[2]=fP[3];
632 return Local2GlobalMomentum(p,fAlpha);
633}
a5e407e9 634
c9ec41e8 635Bool_t AliExternalTrackParam::GetXYZ(Double_t *r) const {
636 //---------------------------------------------------------------------
637 // This function returns the global track position
638 //---------------------------------------------------------------------
639 r[0]=fX; r[1]=fP[0]; r[2]=fP[1];
640 return Local2GlobalPosition(r,fAlpha);
51ad6848 641}
642
c9ec41e8 643Bool_t AliExternalTrackParam::GetCovarianceXYZPxPyPz(Double_t cv[21]) const {
644 //---------------------------------------------------------------------
645 // This function returns the global covariance matrix of the track params
646 //
647 // Cov(x,x) ... : cv[0]
648 // Cov(y,x) ... : cv[1] cv[2]
649 // Cov(z,x) ... : cv[3] cv[4] cv[5]
650 // Cov(px,x)... : cv[6] cv[7] cv[8] cv[9]
651 // Cov(py,x)... : cv[10] cv[11] cv[12] cv[13] cv[14]
652 // Cov(pz,x)... : cv[15] cv[16] cv[17] cv[18] cv[19] cv[20]
a5e407e9 653 //
c9ec41e8 654 // Results for (nearly) straight tracks are meaningless !
655 //---------------------------------------------------------------------
656 if (TMath::Abs(fP[4])<=0) {
657 for (Int_t i=0; i<21; i++) cv[i]=0.;
658 return kFALSE;
a5e407e9 659 }
49d13e89 660 if (TMath::Abs(fP[2]) > kAlmost1) {
c9ec41e8 661 for (Int_t i=0; i<21; i++) cv[i]=0.;
662 return kFALSE;
663 }
664 Double_t pt=1./TMath::Abs(fP[4]);
665 Double_t cs=TMath::Cos(fAlpha), sn=TMath::Sin(fAlpha);
666 Double_t r=TMath::Sqrt(1-fP[2]*fP[2]);
667
668 Double_t m00=-sn, m10=cs;
669 Double_t m23=-pt*(sn + fP[2]*cs/r), m43=-pt*pt*(r*cs - fP[2]*sn);
670 Double_t m24= pt*(cs - fP[2]*sn/r), m44=-pt*pt*(r*sn + fP[2]*cs);
671 Double_t m35=pt, m45=-pt*pt*fP[3];
672
673 cv[0 ] = fC[0]*m00*m00;
674 cv[1 ] = fC[0]*m00*m10;
675 cv[2 ] = fC[0]*m10*m10;
676 cv[3 ] = fC[1]*m00;
677 cv[4 ] = fC[1]*m10;
678 cv[5 ] = fC[2];
679 cv[6 ] = m00*(fC[3]*m23 + fC[10]*m43);
680 cv[7 ] = m10*(fC[3]*m23 + fC[10]*m43);
681 cv[8 ] = fC[4]*m23 + fC[11]*m43;
682 cv[9 ] = m23*(fC[5]*m23 + fC[12]*m43) + m43*(fC[12]*m23 + fC[14]*m43);
683 cv[10] = m00*(fC[3]*m24 + fC[10]*m44);
684 cv[11] = m10*(fC[3]*m24 + fC[10]*m44);
685 cv[12] = fC[4]*m24 + fC[11]*m44;
686 cv[13] = m23*(fC[5]*m24 + fC[12]*m44) + m43*(fC[12]*m24 + fC[14]*m44);
687 cv[14] = m24*(fC[5]*m24 + fC[12]*m44) + m44*(fC[12]*m24 + fC[14]*m44);
688 cv[15] = m00*(fC[6]*m35 + fC[10]*m45);
689 cv[16] = m10*(fC[6]*m35 + fC[10]*m45);
690 cv[17] = fC[7]*m35 + fC[11]*m45;
691 cv[18] = m23*(fC[8]*m35 + fC[12]*m45) + m43*(fC[13]*m35 + fC[14]*m45);
692 cv[19] = m24*(fC[8]*m35 + fC[12]*m45) + m44*(fC[13]*m35 + fC[14]*m45);
693 cv[20] = m35*(fC[9]*m35 + fC[13]*m45) + m45*(fC[13]*m35 + fC[14]*m45);
51ad6848 694
c9ec41e8 695 return kTRUE;
51ad6848 696}
697
51ad6848 698
c9ec41e8 699Bool_t
700AliExternalTrackParam::GetPxPyPzAt(Double_t x, Double_t b, Double_t *p) const {
701 //---------------------------------------------------------------------
702 // This function returns the global track momentum extrapolated to
703 // the radial position "x" (cm) in the magnetic field "b" (kG)
704 //---------------------------------------------------------------------
c9ec41e8 705 p[0]=fP[4];
49d13e89 706 p[1]=fP[2]+(x-fX)*fP[4]*b*kB2C;
c9ec41e8 707 p[2]=fP[3];
708 return Local2GlobalMomentum(p,fAlpha);
51ad6848 709}
710
c9ec41e8 711Bool_t
712AliExternalTrackParam::GetXYZAt(Double_t x, Double_t b, Double_t *r) const {
713 //---------------------------------------------------------------------
714 // This function returns the global track position extrapolated to
715 // the radial position "x" (cm) in the magnetic field "b" (kG)
716 //---------------------------------------------------------------------
c9ec41e8 717 Double_t dx=x-fX;
49d13e89 718 Double_t f1=fP[2], f2=f1 + dx*fP[4]*b*kB2C;
c9ec41e8 719
49d13e89 720 if (TMath::Abs(f2) >= kAlmost1) return kFALSE;
c9ec41e8 721
722 Double_t r1=TMath::Sqrt(1.- f1*f1), r2=TMath::Sqrt(1.- f2*f2);
723 r[0] = x;
724 r[1] = fP[0] + dx*(f1+f2)/(r1+r2);
725 r[2] = fP[1] + dx*(f1+f2)/(f1*r2 + f2*r1)*fP[3];
726 return Local2GlobalPosition(r,fAlpha);
51ad6848 727}
728
729
730//_____________________________________________________________________________
edc97986 731void AliExternalTrackParam::ApproximateHelixWithLine(Double_t xk, Double_t b, AliStrLine *line)
732{
733 //------------------------------------------------------------
734 // Approximate the track (helix) with a straight line tangent to the
735 // helix in the point defined by r (F. Prino, prino@to.infn.it)
736 //------------------------------------------------------------
737 Double_t mom[3];
738 Double_t azim = TMath::ASin(fP[2])+fAlpha;
739 Double_t theta = TMath::Pi()/2. - TMath::ATan(fP[3]);
740 mom[0] = TMath::Sin(theta)*TMath::Cos(azim);
741 mom[1] = TMath::Sin(theta)*TMath::Sin(azim);
742 mom[2] = TMath::Cos(theta);
743 Double_t pos[3];
744 GetXYZAt(xk,b,pos);
745 line->SetP0(pos);
746 line->SetCd(mom);
747}
748//_____________________________________________________________________________
51ad6848 749void AliExternalTrackParam::Print(Option_t* /*option*/) const
750{
751// print the parameters and the covariance matrix
752
753 printf("AliExternalTrackParam: x = %-12g alpha = %-12g\n", fX, fAlpha);
754 printf(" parameters: %12g %12g %12g %12g %12g\n",
c9ec41e8 755 fP[0], fP[1], fP[2], fP[3], fP[4]);
756 printf(" covariance: %12g\n", fC[0]);
757 printf(" %12g %12g\n", fC[1], fC[2]);
758 printf(" %12g %12g %12g\n", fC[3], fC[4], fC[5]);
51ad6848 759 printf(" %12g %12g %12g %12g\n",
c9ec41e8 760 fC[6], fC[7], fC[8], fC[9]);
51ad6848 761 printf(" %12g %12g %12g %12g %12g\n",
c9ec41e8 762 fC[10], fC[11], fC[12], fC[13], fC[14]);
51ad6848 763}
5b77d93c 764
765
766Bool_t AliExternalTrackParam::PropagateTo(Double_t xToGo, Double_t mass, Double_t maxStep, Bool_t rotateTo){
767 //----------------------------------------------------------------
768 // Propagate this track to the plane X=xk (cm)
769 // correction for unhomogenity of the magnetic field and the
770 // the correction for the material is included
771 //
772 // Require acces to magnetic field and geomanager
773 //
774 // mass - mass used in propagation - used for energy loss correction
775 // maxStep - maximal step for propagation
776 //----------------------------------------------------------------
777 const Double_t kEpsilon = 0.00001;
778 Double_t xpos = GetX();
779 Double_t dir = (xpos<xToGo) ? 1.:-1.;
780 //
781 while ( (xToGo-xpos)*dir > kEpsilon){
782 Double_t step = dir*TMath::Min(TMath::Abs(xToGo-xpos), maxStep);
783 Double_t x = xpos+step;
784 Double_t xyz0[3],xyz1[3],param[7];
785 GetXYZ(xyz0); //starting global position
786 Float_t pos0[3] = {xyz0[0],xyz0[1],xyz0[2]};
787 Double_t magZ = AliTracker::GetBz(pos0);
788 if (!GetXYZAt(x,magZ,xyz1)) return kFALSE; // no prolongation
789 AliKalmanTrack::MeanMaterialBudget(xyz0,xyz1,param);
790 if (!PropagateTo(x,magZ)) return kFALSE;
791 Double_t distance = param[4];
792 if (!CorrectForMaterial(distance,param[1],param[0],mass)) return kFALSE;
793 if (rotateTo){
794 GetXYZ(xyz0); // global position
795 Double_t alphan = TMath::ATan2(xyz0[1], xyz0[0]);
796 if (!Rotate(alphan)) return kFALSE;
797 }
798 xpos = GetX();
799 }
800 return kTRUE;
801}
802
803//_____________________________________________________________________________
804Bool_t AliExternalTrackParam::CorrectForMaterial(Double_t d, Double_t x0, Double_t rho, Double_t mass)
805{
806 //
807 // Take into account material effects assuming:
808 // x0 - mean rad length
809 // rho - mean density
810
811 //
812 // multiple scattering
813 //
814 if (mass<=0) {
815 AliError("Non-positive mass");
816 return kFALSE;
817 }
818 Double_t p2=(1.+ fP[3]*fP[3])/(fP[4]*fP[4]);
819 Double_t beta2=p2/(p2 + mass*mass);
820 Double_t theta2=14.1*14.1/(beta2*p2*1e6)*d/x0*rho;
821 //
822 fC[5] += theta2*(1.- fP[2]*fP[2])*(1. + fP[3]*fP[3]);
823 fC[9] += theta2*(1. + fP[3]*fP[3])*(1. + fP[3]*fP[3]);
824 fC[13] += theta2*fP[3]*fP[4]*(1. + fP[3]*fP[3]);
825 fC[14] += theta2*fP[3]*fP[4]*fP[3]*fP[4];
826 //
827 Double_t dE=0.153e-3/beta2*(log(5940*beta2/(1-beta2+1e-10)) - beta2)*d*rho;
828 fP[4] *=(1.- TMath::Sqrt(p2+mass*mass)/p2*dE);
829 //
830 Double_t sigmade = 0.02*TMath::Sqrt(TMath::Abs(dE)); // energy loss fluctuation
831 Double_t sigmac2 = sigmade*sigmade*fP[4]*fP[4]*(p2+mass*mass)/(p2*p2);
832 fC[14] += sigmac2;
833 return kTRUE;
834}
835
836