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87594435 | 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 | ||
acd84897 | 16 | /* $Id$ */ |
fb17acd4 | 17 | |
87594435 | 18 | //------------------------------------------------------------------------- |
19 | // Implementation of the AliKalmanTrack class | |
066782e8 | 20 | // that is the base for AliTPCtrack, AliITStrackV2 and AliTRDtrack |
87594435 | 21 | // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch |
22 | //------------------------------------------------------------------------- | |
23 | ||
24 | #include "AliKalmanTrack.h" | |
74f9526e | 25 | #include "AliPDG.h" |
26 | #include "TPDGCode.h" | |
27 | #include "TDatabasePDG.h" | |
87594435 | 28 | |
29 | ClassImp(AliKalmanTrack) | |
30 | ||
116cbefd | 31 | Double_t AliKalmanTrack::fgConvConst; |
9b280d80 | 32 | |
e2afb3b6 | 33 | //_______________________________________________________________________ |
34 | AliKalmanTrack::AliKalmanTrack(): | |
35 | fLab(-3141593), | |
36 | fChi2(0), | |
37 | fMass(0.13957), | |
38 | fN(0) | |
39 | { | |
116cbefd | 40 | // |
41 | // Default constructor | |
42 | // | |
8de97894 | 43 | if (fgConvConst==0) { |
9b859005 | 44 | Fatal("AliKalmanTrack()", "The magnetic field has not been set!"); |
8de97894 | 45 | } |
74f9526e | 46 | |
47 | fStartTimeIntegral = kFALSE; | |
48 | fIntegratedLength = 0; | |
49 | for(Int_t i=0; i<5; i++) fIntegratedTime[i] = 0; | |
e2afb3b6 | 50 | } |
51 | ||
52 | //_______________________________________________________________________ | |
53 | AliKalmanTrack::AliKalmanTrack(const AliKalmanTrack &t): | |
54 | TObject(t), | |
55 | fLab(t.fLab), | |
56 | fChi2(t.fChi2), | |
57 | fMass(t.fMass), | |
58 | fN(t.fN) | |
59 | { | |
116cbefd | 60 | // |
61 | // Copy constructor | |
62 | // | |
8de97894 | 63 | if (fgConvConst==0) { |
9b859005 | 64 | Fatal("AliKalmanTrack(const AliKalmanTrack&)", |
8de97894 | 65 | "The magnetic field has not been set!"); |
8de97894 | 66 | } |
74f9526e | 67 | |
68 | fStartTimeIntegral = t.fStartTimeIntegral; | |
69 | fIntegratedLength = t.fIntegratedLength; | |
70 | ||
71 | for (Int_t i=0; i<5; i++) | |
72 | fIntegratedTime[i] = t.fIntegratedTime[i]; | |
73 | } | |
c5507f6d | 74 | |
75 | //_______________________________________________________________________ | |
76 | Double_t AliKalmanTrack::GetX() const | |
77 | { | |
fc7be9e3 | 78 | // Returns the X coordinate of the current track position |
c5507f6d | 79 | Warning("GetX()","Method must be overloaded !\n"); |
80 | return 0.; | |
81 | } | |
82 | //_______________________________________________________________________ | |
83 | Double_t AliKalmanTrack::GetdEdx() const | |
84 | { | |
fc7be9e3 | 85 | // Returns the dE/dx of the track |
c5507f6d | 86 | Warning("GetdEdx()","Method must be overloaded !\n"); |
87 | return 0.; | |
88 | } | |
89 | ||
90 | //_______________________________________________________________________ | |
91 | Double_t AliKalmanTrack::GetY() const | |
92 | { | |
fc7be9e3 | 93 | // Returns the Y coordinate of the current track position |
c5507f6d | 94 | Double_t par[5]; |
95 | Double_t localX = GetX(); | |
96 | GetExternalParameters(localX, par); | |
97 | return par[0]; | |
98 | } | |
99 | //_______________________________________________________________________ | |
100 | Double_t AliKalmanTrack::GetZ() const | |
101 | { | |
fc7be9e3 | 102 | // Returns the Z coordinate of the current track position |
c5507f6d | 103 | Double_t par[5]; |
104 | Double_t localX = GetX(); | |
105 | GetExternalParameters(localX, par); | |
106 | return par[1]; | |
107 | } | |
108 | //_______________________________________________________________________ | |
109 | Double_t AliKalmanTrack::GetSnp() const | |
110 | { | |
fc7be9e3 | 111 | // Returns the Sin(phi), where phi is the angle between the transverse |
112 | // momentum (in xOy plane) and the X axis | |
c5507f6d | 113 | Double_t par[5]; |
114 | Double_t localX = GetX(); | |
115 | GetExternalParameters(localX, par); | |
116 | return par[2]; | |
117 | } | |
118 | //_______________________________________________________________________ | |
119 | Double_t AliKalmanTrack::GetTgl() const | |
120 | { | |
fc7be9e3 | 121 | // Returns the Tan(lambda), where lambda is the dip angle (between |
122 | // the bending plane (xOy) and the momentum of the track | |
c5507f6d | 123 | Double_t par[5]; |
124 | Double_t localX = GetX(); | |
125 | GetExternalParameters(localX, par); | |
126 | return par[3]; | |
127 | } | |
128 | //_______________________________________________________________________ | |
129 | Double_t AliKalmanTrack::Get1Pt() const | |
130 | { | |
fc7be9e3 | 131 | // Returns 1/pT |
c5507f6d | 132 | Double_t par[5]; |
133 | Double_t localX = GetX(); | |
134 | GetExternalParameters(localX, par); | |
135 | return par[4]; | |
136 | } | |
137 | ||
138 | //_______________________________________________________________________ | |
139 | Double_t AliKalmanTrack::Phi() const | |
140 | { | |
141 | // return global phi of track | |
142 | ||
143 | Double_t par[5]; | |
144 | Double_t localX = GetX(); | |
145 | GetExternalParameters(localX, par); | |
79e94bf8 | 146 | if (par[2] > 1.) par[2] = 1.; |
147 | if (par[2] < -1.) par[2] = -1.; | |
c5507f6d | 148 | Double_t phi = TMath::ASin(par[2]) + GetAlpha(); |
149 | while (phi < 0) phi += TMath::TwoPi(); | |
150 | while (phi > TMath::TwoPi()) phi -= TMath::TwoPi(); | |
151 | return phi; | |
152 | } | |
153 | //_______________________________________________________________________ | |
154 | Double_t AliKalmanTrack::SigmaPhi() const | |
155 | { | |
156 | // return error of global phi of track | |
157 | ||
158 | Double_t par[5]; | |
159 | Double_t cov[15]; | |
160 | Double_t localX = GetX(); | |
161 | GetExternalParameters(localX, par); | |
162 | GetExternalCovariance(cov); | |
163 | return TMath::Sqrt(TMath::Abs(cov[5] / (1. - par[2]*par[2]))); | |
164 | } | |
165 | //_______________________________________________________________________ | |
166 | Double_t AliKalmanTrack::Theta() const | |
167 | { | |
168 | // return global theta of track | |
169 | ||
170 | Double_t par[5]; | |
171 | Double_t localX = GetX(); | |
172 | GetExternalParameters(localX, par); | |
173 | return TMath::Pi()/2. - TMath::ATan(par[3]); | |
174 | } | |
175 | //_______________________________________________________________________ | |
176 | Double_t AliKalmanTrack::SigmaTheta() const | |
177 | { | |
178 | // return error of global theta of track | |
179 | ||
180 | Double_t par[5]; | |
181 | Double_t cov[15]; | |
182 | Double_t localX = GetX(); | |
183 | GetExternalParameters(localX, par); | |
184 | GetExternalCovariance(cov); | |
185 | return TMath::Sqrt(TMath::Abs(cov[5])) / (1. + par[3]*par[3]); | |
186 | } | |
187 | //_______________________________________________________________________ | |
8de97894 | 188 | Double_t AliKalmanTrack::Eta() const |
189 | { | |
190 | // return global eta of track | |
191 | ||
192 | return -TMath::Log(TMath::Tan(Theta()/2.)); | |
193 | } | |
194 | //_______________________________________________________________________ | |
c5507f6d | 195 | Double_t AliKalmanTrack::Px() const |
196 | { | |
197 | // return x component of track momentum | |
198 | ||
199 | Double_t par[5]; | |
200 | Double_t localX = GetX(); | |
201 | GetExternalParameters(localX, par); | |
202 | Double_t phi = TMath::ASin(par[2]) + GetAlpha(); | |
203 | return TMath::Cos(phi) / TMath::Abs(par[4]); | |
204 | } | |
205 | //_______________________________________________________________________ | |
206 | Double_t AliKalmanTrack::Py() const | |
207 | { | |
208 | // return y component of track momentum | |
209 | ||
210 | Double_t par[5]; | |
211 | Double_t localX = GetX(); | |
212 | GetExternalParameters(localX, par); | |
213 | Double_t phi = TMath::ASin(par[2]) + GetAlpha(); | |
214 | return TMath::Sin(phi) / TMath::Abs(par[4]); | |
215 | } | |
216 | //_______________________________________________________________________ | |
217 | Double_t AliKalmanTrack::Pz() const | |
218 | { | |
219 | // return z component of track momentum | |
220 | ||
221 | Double_t par[5]; | |
222 | Double_t localX = GetX(); | |
223 | GetExternalParameters(localX, par); | |
224 | return par[3] / TMath::Abs(par[4]); | |
225 | } | |
226 | //_______________________________________________________________________ | |
227 | Double_t AliKalmanTrack::Pt() const | |
228 | { | |
229 | // return transverse component of track momentum | |
230 | ||
231 | Double_t par[5]; | |
232 | Double_t localX = GetX(); | |
233 | GetExternalParameters(localX, par); | |
234 | return 1. / TMath::Abs(par[4]); | |
235 | } | |
236 | //_______________________________________________________________________ | |
237 | Double_t AliKalmanTrack::SigmaPt() const | |
238 | { | |
239 | // return error of transverse component of track momentum | |
240 | ||
241 | Double_t par[5]; | |
242 | Double_t cov[15]; | |
243 | Double_t localX = GetX(); | |
244 | GetExternalParameters(localX, par); | |
245 | GetExternalCovariance(cov); | |
246 | return TMath::Sqrt(cov[14]) / TMath::Abs(par[4]); | |
247 | } | |
248 | //_______________________________________________________________________ | |
249 | Double_t AliKalmanTrack::P() const | |
250 | { | |
251 | // return total track momentum | |
252 | ||
253 | Double_t par[5]; | |
254 | Double_t localX = GetX(); | |
255 | GetExternalParameters(localX, par); | |
79e94bf8 | 256 | return 1. / TMath::Abs(par[4] * TMath::Cos(TMath::ATan(par[3]))); |
c5507f6d | 257 | } |
74f9526e | 258 | //_______________________________________________________________________ |
259 | void AliKalmanTrack::StartTimeIntegral() | |
260 | { | |
49a7a79a | 261 | // Sylwester Radomski, GSI |
262 | // S.Radomski@gsi.de | |
74f9526e | 263 | // |
264 | // Start time integration | |
265 | // To be called at Vertex by ITS tracker | |
266 | // | |
267 | ||
268 | //if (fStartTimeIntegral) | |
269 | // Warning("StartTimeIntegral", "Reseting Recorded Time."); | |
270 | ||
271 | fStartTimeIntegral = kTRUE; | |
5d8718b8 | 272 | for(Int_t i=0; i<fgkTypes; i++) fIntegratedTime[i] = 0; |
74f9526e | 273 | fIntegratedLength = 0; |
274 | } | |
275 | //_______________________________________________________________________ | |
276 | void AliKalmanTrack:: AddTimeStep(Double_t length) | |
277 | { | |
278 | // | |
279 | // Add step to integrated time | |
280 | // this method should be called by a sublasses at the end | |
281 | // of the PropagateTo function or by a tracker | |
282 | // each time step is made. | |
283 | // | |
284 | // If integration not started function does nothing | |
285 | // | |
286 | // Formula | |
287 | // dt = dl * sqrt(p^2 + m^2) / p | |
288 | // p = pT * (1 + tg^2 (lambda) ) | |
289 | // | |
290 | // pt = 1/external parameter [4] | |
291 | // tg lambda = external parameter [3] | |
292 | // | |
293 | // | |
294 | // Sylwester Radomski, GSI | |
295 | // S.Radomski@gsi.de | |
296 | // | |
297 | ||
5d8718b8 | 298 | static const Double_t kcc = 2.99792458e-2; |
74f9526e | 299 | |
300 | if (!fStartTimeIntegral) return; | |
301 | ||
302 | fIntegratedLength += length; | |
303 | ||
5d8718b8 | 304 | static Int_t pdgCode[fgkTypes] = {kElectron, kMuonMinus, kPiPlus, kKPlus, kProton}; |
74f9526e | 305 | TDatabasePDG *db = TDatabasePDG::Instance(); |
306 | ||
307 | Double_t xr, param[5]; | |
308 | Double_t pt, tgl; | |
309 | ||
310 | GetExternalParameters(xr, param); | |
311 | pt = 1/param[4] ; | |
312 | tgl = param[3]; | |
313 | ||
314 | Double_t p = TMath::Abs(pt * TMath::Sqrt(1+tgl*tgl)); | |
315 | ||
316 | if (length > 100) return; | |
317 | ||
5d8718b8 | 318 | for (Int_t i=0; i<fgkTypes; i++) { |
74f9526e | 319 | |
320 | Double_t mass = db->GetParticle(pdgCode[i])->Mass(); | |
321 | Double_t correction = TMath::Sqrt( pt*pt * (1 + tgl*tgl) + mass * mass ) / p; | |
5d8718b8 | 322 | Double_t time = length * correction / kcc; |
74f9526e | 323 | |
74f9526e | 324 | fIntegratedTime[i] += time; |
325 | } | |
e2afb3b6 | 326 | } |
327 | ||
74f9526e | 328 | //_______________________________________________________________________ |
329 | ||
330 | Double_t AliKalmanTrack::GetIntegratedTime(Int_t pdg) const | |
331 | { | |
49a7a79a | 332 | // Sylwester Radomski, GSI |
333 | // S.Radomski@gsi.de | |
74f9526e | 334 | // |
335 | // Return integrated time hypothesis for a given particle | |
336 | // type assumption. | |
337 | // | |
338 | // Input parameter: | |
339 | // pdg - Pdg code of a particle type | |
340 | // | |
341 | ||
342 | ||
343 | if (!fStartTimeIntegral) { | |
344 | Warning("GetIntegratedTime","Time integration not started"); | |
345 | return 0.; | |
346 | } | |
347 | ||
5d8718b8 | 348 | static Int_t pdgCode[fgkTypes] = {kElectron, kMuonMinus, kPiPlus, kKPlus, kProton}; |
74f9526e | 349 | |
5d8718b8 | 350 | for (Int_t i=0; i<fgkTypes; i++) |
74f9526e | 351 | if (pdgCode[i] == TMath::Abs(pdg)) return fIntegratedTime[i]; |
352 | ||
353 | Warning(":GetIntegratedTime","Particle type [%d] not found", pdg); | |
354 | return 0; | |
355 | } | |
ae982df3 | 356 | |
357 | void AliKalmanTrack::GetIntegratedTimes(Double_t *times) const { | |
358 | for (Int_t i=0; i<fgkTypes; i++) times[i]=fIntegratedTime[i]; | |
359 | } | |
360 | ||
361 | void AliKalmanTrack::SetIntegratedTimes(const Double_t *times) { | |
362 | for (Int_t i=0; i<fgkTypes; i++) fIntegratedTime[i]=times[i]; | |
363 | } | |
364 | ||
74f9526e | 365 | //_______________________________________________________________________ |
366 | ||
367 | void AliKalmanTrack::PrintTime() const | |
368 | { | |
49a7a79a | 369 | // Sylwester Radomski, GSI |
370 | // S.Radomski@gsi.de | |
371 | // | |
74f9526e | 372 | // For testing |
373 | // Prints time for all hypothesis | |
374 | // | |
375 | ||
5d8718b8 | 376 | static Int_t pdgCode[fgkTypes] = {kElectron, kMuonMinus, kPiPlus, kKPlus, kProton}; |
74f9526e | 377 | |
5d8718b8 | 378 | for (Int_t i=0; i<fgkTypes; i++) |
74f9526e | 379 | printf("%d: %.2f ", pdgCode[i], fIntegratedTime[i]); |
380 | printf("\n"); | |
381 | } | |
382 | ||
49a7a79a | 383 | static void External2Helix(const AliKalmanTrack *t, Double_t helix[6]) { |
384 | //-------------------------------------------------------------------- | |
385 | // External track parameters -> helix parameters | |
386 | //-------------------------------------------------------------------- | |
387 | Double_t alpha,x,cs,sn; | |
388 | t->GetExternalParameters(x,helix); alpha=t->GetAlpha(); | |
389 | ||
390 | cs=TMath::Cos(alpha); sn=TMath::Sin(alpha); | |
391 | helix[5]=x*cs - helix[0]*sn; // x0 | |
392 | helix[0]=x*sn + helix[0]*cs; // y0 | |
393 | //helix[1]= // z0 | |
394 | helix[2]=TMath::ASin(helix[2]) + alpha; // phi0 | |
395 | //helix[3]= // tgl | |
396 | helix[4]=helix[4]/t->GetConvConst(); // C | |
397 | } | |
398 | ||
399 | static void Evaluate(const Double_t *h, Double_t t, | |
400 | Double_t r[3], //radius vector | |
401 | Double_t g[3], //first defivatives | |
402 | Double_t gg[3]) //second derivatives | |
403 | { | |
404 | //-------------------------------------------------------------------- | |
405 | // Calculate position of a point on a track and some derivatives | |
406 | //-------------------------------------------------------------------- | |
407 | Double_t phase=h[4]*t+h[2]; | |
408 | Double_t sn=TMath::Sin(phase), cs=TMath::Cos(phase); | |
409 | ||
410 | r[0] = h[5] + (sn - h[6])/h[4]; | |
411 | r[1] = h[0] - (cs - h[7])/h[4]; | |
412 | r[2] = h[1] + h[3]*t; | |
413 | ||
414 | g[0] = cs; g[1]=sn; g[2]=h[3]; | |
415 | ||
416 | gg[0]=-h[4]*sn; gg[1]=h[4]*cs; gg[2]=0.; | |
417 | } | |
418 | ||
419 | Double_t AliKalmanTrack:: | |
420 | GetDCA(const AliKalmanTrack *p, Double_t &xthis, Double_t &xp) const { | |
421 | //------------------------------------------------------------ | |
422 | // Returns the (weighed !) distance of closest approach between | |
423 | // this track and the track passed as the argument. | |
424 | // Other returned values: | |
425 | // xthis, xt - coordinates of tracks' reference planes at the DCA | |
426 | //----------------------------------------------------------- | |
427 | Double_t dy2=GetSigmaY2() + p->GetSigmaY2(); | |
428 | Double_t dz2=GetSigmaZ2() + p->GetSigmaZ2(); | |
429 | Double_t dx2=dy2; | |
430 | ||
431 | //dx2=dy2=dz2=1.; | |
432 | ||
433 | Double_t p1[8]; External2Helix(this,p1); | |
434 | p1[6]=TMath::Sin(p1[2]); p1[7]=TMath::Cos(p1[2]); | |
435 | Double_t p2[8]; External2Helix(p,p2); | |
436 | p2[6]=TMath::Sin(p2[2]); p2[7]=TMath::Cos(p2[2]); | |
437 | ||
438 | ||
439 | Double_t r1[3],g1[3],gg1[3]; Double_t t1=0.; | |
440 | Evaluate(p1,t1,r1,g1,gg1); | |
441 | Double_t r2[3],g2[3],gg2[3]; Double_t t2=0.; | |
442 | Evaluate(p2,t2,r2,g2,gg2); | |
74f9526e | 443 | |
49a7a79a | 444 | Double_t dx=r2[0]-r1[0], dy=r2[1]-r1[1], dz=r2[2]-r1[2]; |
445 | Double_t dm=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2; | |
446 | ||
447 | Int_t max=27; | |
448 | while (max--) { | |
449 | Double_t gt1=-(dx*g1[0]/dx2 + dy*g1[1]/dy2 + dz*g1[2]/dz2); | |
450 | Double_t gt2=+(dx*g2[0]/dx2 + dy*g2[1]/dy2 + dz*g2[2]/dz2); | |
451 | Double_t h11=(g1[0]*g1[0] - dx*gg1[0])/dx2 + | |
452 | (g1[1]*g1[1] - dy*gg1[1])/dy2 + | |
453 | (g1[2]*g1[2] - dz*gg1[2])/dz2; | |
454 | Double_t h22=(g2[0]*g2[0] + dx*gg2[0])/dx2 + | |
455 | (g2[1]*g2[1] + dy*gg2[1])/dy2 + | |
456 | (g2[2]*g2[2] + dz*gg2[2])/dz2; | |
457 | Double_t h12=-(g1[0]*g2[0]/dx2 + g1[1]*g2[1]/dy2 + g1[2]*g2[2]/dz2); | |
458 | ||
459 | Double_t det=h11*h22-h12*h12; | |
460 | ||
461 | Double_t dt1,dt2; | |
462 | if (TMath::Abs(det)<1.e-33) { | |
463 | //(quasi)singular Hessian | |
464 | dt1=-gt1; dt2=-gt2; | |
465 | } else { | |
466 | dt1=-(gt1*h22 - gt2*h12)/det; | |
467 | dt2=-(h11*gt2 - h12*gt1)/det; | |
468 | } | |
469 | ||
470 | if ((dt1*gt1+dt2*gt2)>0) {dt1=-dt1; dt2=-dt2;} | |
471 | ||
472 | //check delta(phase1) ? | |
473 | //check delta(phase2) ? | |
474 | ||
475 | if (TMath::Abs(dt1)/(TMath::Abs(t1)+1.e-3) < 1.e-4) | |
476 | if (TMath::Abs(dt2)/(TMath::Abs(t2)+1.e-3) < 1.e-4) { | |
477 | if ((gt1*gt1+gt2*gt2) > 1.e-4/dy2/dy2) | |
478 | Warning("GetDCA"," stopped at not a stationary point !\n"); | |
479 | Double_t lmb=h11+h22; lmb=lmb-TMath::Sqrt(lmb*lmb-4*det); | |
480 | if (lmb < 0.) | |
481 | Warning("GetDCA"," stopped at not a minimum !\n"); | |
482 | break; | |
483 | } | |
484 | ||
485 | Double_t dd=dm; | |
486 | for (Int_t div=1 ; ; div*=2) { | |
487 | Evaluate(p1,t1+dt1,r1,g1,gg1); | |
488 | Evaluate(p2,t2+dt2,r2,g2,gg2); | |
489 | dx=r2[0]-r1[0]; dy=r2[1]-r1[1]; dz=r2[2]-r1[2]; | |
490 | dd=dx*dx/dx2 + dy*dy/dy2 + dz*dz/dz2; | |
491 | if (dd<dm) break; | |
492 | dt1*=0.5; dt2*=0.5; | |
493 | if (div>512) { | |
494 | Warning("GetDCA"," overshoot !\n"); break; | |
495 | } | |
496 | } | |
497 | dm=dd; | |
498 | ||
499 | t1+=dt1; | |
500 | t2+=dt2; | |
501 | ||
502 | } | |
503 | ||
504 | if (max<=0) Warning("GetDCA"," too many iterations !\n"); | |
505 | ||
506 | Double_t cs=TMath::Cos(GetAlpha()); | |
507 | Double_t sn=TMath::Sin(GetAlpha()); | |
508 | xthis=r1[0]*cs + r1[1]*sn; | |
509 | ||
510 | cs=TMath::Cos(p->GetAlpha()); | |
511 | sn=TMath::Sin(p->GetAlpha()); | |
512 | xp=r2[0]*cs + r2[1]*sn; | |
513 | ||
514 | return TMath::Sqrt(dm*TMath::Sqrt(dy2*dz2)); | |
515 | } | |
516 | ||
517 | Double_t AliKalmanTrack:: | |
518 | PropagateToDCA(AliKalmanTrack *p, Double_t d, Double_t x0) { | |
519 | //-------------------------------------------------------------- | |
520 | // Propagates this track and the argument track to the position of the | |
521 | // distance of closest approach. | |
522 | // Returns the (weighed !) distance of closest approach. | |
523 | //-------------------------------------------------------------- | |
524 | Double_t xthis,xp; | |
525 | Double_t dca=GetDCA(p,xthis,xp); | |
526 | ||
527 | if (!PropagateTo(xthis,d,x0)) { | |
528 | //Warning("PropagateToDCA"," propagation failed !\n"); | |
529 | return 1e+33; | |
530 | } | |
531 | ||
532 | if (!p->PropagateTo(xp,d,x0)) { | |
533 | //Warning("PropagateToDCA"," propagation failed !\n"; | |
534 | return 1e+33; | |
535 | } | |
536 | ||
537 | return dca; | |
538 | } |