Changes to EventReconstructor...:
[u/mrichter/AliRoot.git] / MUON / AliMUONTrack.cxx
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a9e2aefa 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/*
17$Log$
04b5ea16 18Revision 1.3 2000/06/25 13:23:28 hristov
19stdlib.h needed for non-Linux compilation
20
f6e92cf4 21Revision 1.2 2000/06/15 07:58:48 morsch
22Code from MUON-dev joined
23
a9e2aefa 24Revision 1.1.2.3 2000/06/12 10:11:34 morsch
25Dummy copy constructor and assignment operator added
26
27Revision 1.1.2.2 2000/06/09 12:58:05 gosset
28Removed comment beginnings in Log sections of .cxx files
29Suppressed most violations of coding rules
30
31Revision 1.1.2.1 2000/06/07 14:44:53 gosset
32Addition of files for track reconstruction in C++
33*/
34
35//__________________________________________________________________________
36//
37// Reconstructed track in ALICE dimuon spectrometer
38//__________________________________________________________________________
39
40#include "AliMUONTrack.h"
41
42#include <iostream.h>
43
44#include <TClonesArray.h>
45#include <TMinuit.h>
04b5ea16 46#include <TMath.h>
47#include <TMatrix.h>
a9e2aefa 48
49#include "AliMUONEventReconstructor.h"
50#include "AliMUONHitForRec.h"
51#include "AliMUONSegment.h"
52#include "AliMUONTrackHit.h"
53
f6e92cf4 54#include <stdlib.h>
55
04b5ea16 56// variables to be known from minimization functions
a9e2aefa 57static AliMUONTrack *trackBeingFitted;
58static AliMUONTrackParam *trackParamBeingFitted;
59
04b5ea16 60// Functions to be minimized with Minuit
a9e2aefa 61void TrackChi2(Int_t &NParam, Double_t *Gradient, Double_t &Chi2, Double_t *Param, Int_t Flag);
04b5ea16 62void TrackChi2MCS(Int_t &NParam, Double_t *Gradient, Double_t &Chi2, Double_t *Param, Int_t Flag);
63
64Double_t MultipleScatteringAngle2(AliMUONTrackHit *TrackHit);
a9e2aefa 65
66ClassImp(AliMUONTrack) // Class implementation in ROOT context
67
68 //__________________________________________________________________________
69AliMUONTrack::AliMUONTrack(AliMUONSegment* BegSegment, AliMUONSegment* EndSegment, AliMUONEventReconstructor* EventReconstructor)
70{
71 // Constructor from two Segment's
72 fEventReconstructor = EventReconstructor; // link back to EventReconstructor
73 // memory allocation for the TClonesArray of reconstructed TrackHit's
74 fTrackHitsPtr = new TClonesArray("AliMUONTrackHit", 10);
75 fNTrackHits = 0;
76 AddSegment(BegSegment); // add hits from BegSegment
77 AddSegment(EndSegment); // add hits from EndSegment
78 fTrackHitsPtr->Sort(); // sort TrackHits according to increasing Z
79 SetTrackParamAtVertex(); // set track parameters at vertex
04b5ea16 80 fFitMCS = 0;
a9e2aefa 81 return;
82}
83
84 //__________________________________________________________________________
85AliMUONTrack::AliMUONTrack(AliMUONSegment* Segment, AliMUONHitForRec* HitForRec, AliMUONEventReconstructor* EventReconstructor)
86{
87 // Constructor from one Segment and one HitForRec
88 fEventReconstructor = EventReconstructor; // link back to EventReconstructor
89 // memory allocation for the TClonesArray of reconstructed TrackHit's
90 fTrackHitsPtr = new TClonesArray("AliMUONTrackHit", 10);
91 fNTrackHits = 0;
92 AddSegment(Segment); // add hits from Segment
93 AddHitForRec(HitForRec); // add HitForRec
94 fTrackHitsPtr->Sort(); // sort TrackHits according to increasing Z
95 SetTrackParamAtVertex(); // set track parameters at vertex
04b5ea16 96 fFitMCS = 0;
a9e2aefa 97 return;
98}
99
100AliMUONTrack::AliMUONTrack (const AliMUONTrack& MUONTrack)
101{
102// Dummy copy constructor
103}
104
105AliMUONTrack & AliMUONTrack::operator=(const AliMUONTrack& MUONTrack)
106{
107// Dummy assignment operator
108 return *this;
109}
110
04b5ea16 111 //__________________________________________________________________________
112void AliMUONTrack::SetFitMCS(Int_t FitMCS)
113{
114 // Set track fit option with or without multiple Coulomb scattering
115 // from "FitMCS" argument: 0 without, 1 with
116 fFitMCS = FitMCS;
117 // better implementation with enum(with, without) ????
118 return;
119}
120
a9e2aefa 121// Inline functions for Get and Set: inline removed because it does not work !!!!
122AliMUONTrackParam* AliMUONTrack::GetTrackParamAtVertex(void) {
123 // Get pointer to fTrackParamAtVertex
124 return &fTrackParamAtVertex;}
125AliMUONTrackParam* AliMUONTrack::GetTrackParamAtFirstHit(void) {
126 // Get pointer to TrackParamAtFirstHit
127 return ((AliMUONTrackHit*) (fTrackHitsPtr->First()))->GetTrackParam();}
128TClonesArray* AliMUONTrack::GetTrackHitsPtr(void) {
129 // Get fTrackHitsPtr
130 return fTrackHitsPtr;}
131Int_t AliMUONTrack::GetNTrackHits(void) {
132 // Get fNTrackHits
133 return fNTrackHits;}
134
135 //__________________________________________________________________________
136void AliMUONTrack::RecursiveDump(void)
137{
138 // Recursive dump of AliMUONTrack, i.e. with dump of TrackHit's and HitForRec's
139 AliMUONTrackHit *trackHit;
140 AliMUONHitForRec *hitForRec;
141 cout << "Recursive dump of Track: " << this << endl;
142 // Track
143 this->Dump();
144 for (Int_t trackHitIndex = 0; trackHitIndex < fNTrackHits; trackHitIndex++) {
145 trackHit = (AliMUONTrackHit*) ((*fTrackHitsPtr)[trackHitIndex]);
146 // TrackHit
147 cout << "TrackHit: " << trackHit << " (index: " << trackHitIndex << ")" << endl;
148 trackHit->Dump();
149 hitForRec = trackHit->GetHitForRecPtr();
150 // HitForRec
151 cout << "HitForRec: " << hitForRec << endl;
152 hitForRec->Dump();
153 }
154 return;
155}
156
157 //__________________________________________________________________________
158void AliMUONTrack::Fit(AliMUONTrackParam *TrackParam, Int_t NParam)
159{
160 // Fit the current track ("this"),
161 // starting with track parameters pointed to by "TrackParam",
162 // and with 3 or 5 parameters ("NParam"):
163 // 3 if one keeps X and Y fixed in "TrackParam",
164 // 5 if one lets them vary.
165 if ((NParam != 3) && (NParam != 5)) {
166 cout << "ERROR in AliMUONTrack::Fit, NParam = " << NParam;
167 cout << " , i.e. neither 3 nor 5 ====> EXIT" << endl;
168 exit(0); // right instruction for exit ????
169 }
170 Int_t error = 0;
171 Double_t arg[1], benC, errorParam, invBenP, lower, nonBenC, upper, x, y;
172 TString parName;
173 TMinuit *minuit = new TMinuit(5);
174 trackBeingFitted = this; // for the track to be known from the function to minimize
175 trackParamBeingFitted = TrackParam; // for the track parameters to be known from the function to minimize; possible to use only Minuit parameters ????
04b5ea16 176 // try to use TVirtualFitter to get this feature automatically !!!!
a9e2aefa 177 minuit->mninit(5, 10, 7); // sysrd, syswr, syssa: useful ????
178 // how to go faster ???? choice of Minuit parameters like EDM ????
04b5ea16 179 // choice of function to be minimized according to fFitMCS
180 if (fFitMCS == 0) minuit->SetFCN(TrackChi2);
181 else minuit->SetFCN(TrackChi2MCS);
a9e2aefa 182 minuit->SetPrintLevel(1); // More printing !!!!
04b5ea16 183 // set first 3 parameters
184 // could be tried with no limits for the search (min=max=0) ????
a9e2aefa 185 minuit->mnparm(0, "InvBenP",
186 TrackParam->GetInverseBendingMomentum(),
04b5ea16 187 0.003, -0.4, 0.4, error);
a9e2aefa 188 minuit->mnparm(1, "BenS",
189 TrackParam->GetBendingSlope(),
04b5ea16 190 0.001, -0.5, 0.5, error);
a9e2aefa 191 minuit->mnparm(2, "NonBenS",
192 TrackParam->GetNonBendingSlope(),
04b5ea16 193 0.001, -0.5, 0.5, error);
a9e2aefa 194 if (NParam == 5) {
04b5ea16 195 // set last 2 parameters (no limits for the search: min=max=0)
a9e2aefa 196 minuit->mnparm(3, "X",
197 TrackParam->GetNonBendingCoor(),
198 0.03, 0.0, 0.0, error);
199 minuit->mnparm(4, "Y",
200 TrackParam->GetBendingCoor(),
201 0.10, 0.0, 0.0, error);
202 }
203 // search without gradient calculation in the function
204 minuit->mnexcm("SET NOGRADIENT", arg, 0, error);
205 // minimization
206 minuit->mnexcm("MINIMIZE", arg, 0, error);
207 // exit from Minuit
208 minuit->mnexcm("EXIT", arg, 0, error); // necessary ????
209 // print results
210 minuit->mnpout(0, parName, invBenP, errorParam, lower, upper, error);
211 minuit->mnpout(1, parName, benC, errorParam, lower, upper, error);
212 minuit->mnpout(2, parName, nonBenC, errorParam, lower, upper, error);
213 if (NParam == 5) {
214 minuit->mnpout(3, parName, x, errorParam, lower, upper, error);
215 minuit->mnpout(4, parName, y, errorParam, lower, upper, error);
216 }
217 // result of the fit into track parameters
218 TrackParam->SetInverseBendingMomentum(invBenP);
219 TrackParam->SetBendingSlope(benC);
220 TrackParam->SetNonBendingSlope(nonBenC);
221 if (NParam == 5) {
222 TrackParam->SetNonBendingCoor(x);
223 TrackParam->SetBendingCoor(y);
224 }
225 trackBeingFitted = NULL;
226 delete minuit;
227}
228
229 //__________________________________________________________________________
230void AliMUONTrack::AddSegment(AliMUONSegment* Segment)
231{
232 // Add Segment
233 AddHitForRec(Segment->GetHitForRec1()); // 1st hit
234 AddHitForRec(Segment->GetHitForRec2()); // 2nd hit
235}
236
237 //__________________________________________________________________________
238void AliMUONTrack::AddHitForRec(AliMUONHitForRec* HitForRec)
239{
240 // Add HitForRec
241 new ((*fTrackHitsPtr)[fNTrackHits]) AliMUONTrackHit(HitForRec);
242 fNTrackHits++;
243}
244
245 //__________________________________________________________________________
246void AliMUONTrack::SetTrackParamAtHit(Int_t indexHit, AliMUONTrackParam *TrackParam)
247{
248 // Set track parameters at TrackHit with index "indexHit"
249 // from the track parameters pointed to by "TrackParam".
250 AliMUONTrackHit* trackHit = (AliMUONTrackHit*) ((*fTrackHitsPtr)[indexHit]);
251 trackHit->SetTrackParam(TrackParam);
252}
253
254 //__________________________________________________________________________
255void AliMUONTrack::SetTrackParamAtVertex()
256{
257 // Set track parameters at vertex.
258 // TrackHit's are assumed to be only in stations(1..) 4 and 5,
259 // and sorted according to increasing Z..
260 // Parameters are calculated from information in HitForRec's
261 // of first and last TrackHit's.
262 AliMUONTrackParam *trackParam =
263 &fTrackParamAtVertex; // pointer to track parameters
264 // Pointer to HitForRec of first TrackHit
265 AliMUONHitForRec *firstHit =
266 ((AliMUONTrackHit*) (fTrackHitsPtr->First()))->GetHitForRecPtr();
267 // Pointer to HitForRec of last TrackHit
268 AliMUONHitForRec *lastHit =
269 ((AliMUONTrackHit*) (fTrackHitsPtr->Last()))->GetHitForRecPtr();
270 // Z difference between first and last hits
271 Double_t deltaZ = firstHit->GetZ() - lastHit->GetZ();
272 // bending slope in stations(1..) 4 and 5
273 Double_t bendingSlope =
274 (firstHit->GetBendingCoor() - lastHit->GetBendingCoor()) / deltaZ;
275 trackParam->SetBendingSlope(bendingSlope);
276 // impact parameter
277 Double_t impactParam =
278 firstHit->GetBendingCoor() - bendingSlope * firstHit->GetZ(); // same if from firstHit and lastHit ????
279 // signed bending momentum
280 Double_t signedBendingMomentum =
281 fEventReconstructor->GetBendingMomentumFromImpactParam(impactParam);
282 trackParam->SetInverseBendingMomentum(1.0 / signedBendingMomentum);
283 // bending slope at vertex
284 trackParam->
285 SetBendingSlope(bendingSlope +
286 impactParam / fEventReconstructor->GetSimpleBPosition());
287 // non bending slope
288 Double_t nonBendingSlope =
289 (firstHit->GetNonBendingCoor() - lastHit->GetNonBendingCoor()) / deltaZ;
290 trackParam->SetNonBendingSlope(nonBendingSlope);
291 // vertex coordinates at (0,0,0)
292 trackParam->SetZ(0.0);
293 trackParam->SetBendingCoor(0.0);
294 trackParam->SetNonBendingCoor(0.0);
295}
296
297 //__________________________________________________________________________
298void TrackChi2(Int_t &NParam, Double_t *Gradient, Double_t &Chi2, Double_t *Param, Int_t Flag)
299{
300 // Return the "Chi2" to be minimized with Minuit for track fitting,
301 // with "NParam" parameters
302 // and their current values in array pointed to by "Param".
303 // Assumes that the track hits are sorted according to increasing Z.
304 // Track parameters at each TrackHit are updated accordingly.
04b5ea16 305 // Multiple Coulomb scattering is not taken into account
a9e2aefa 306 AliMUONTrackHit* hit;
307 AliMUONTrackParam param1;
308 Int_t hitNumber;
309 Double_t zHit;
310 Chi2 = 0.0; // initialize Chi2
311 // copy of track parameters to be fitted
312 param1 = *trackParamBeingFitted;
313 // Minuit parameters to be fitted into this copy
314 param1.SetInverseBendingMomentum(Param[0]);
315 param1.SetBendingSlope(Param[1]);
316 param1.SetNonBendingSlope(Param[2]);
317 if (NParam == 5) {
318 param1.SetNonBendingCoor(Param[3]);
319 param1.SetBendingCoor(Param[4]);
320 }
321 // Follow track through all planes of track hits
322 for (hitNumber = 0; hitNumber < trackBeingFitted->GetNTrackHits(); hitNumber++) {
323 hit = (AliMUONTrackHit*) (*(trackBeingFitted->GetTrackHitsPtr()))[hitNumber];
324 zHit = hit->GetHitForRecPtr()->GetZ();
325 // do something special if 2 hits with same Z ????
326 // security against infinite loop ????
327 (&param1)->ExtrapToZ(zHit); // extrapolation
328 hit->SetTrackParam(&param1);
329 // Increment Chi2
330 // done hit per hit, with hit resolution,
331 // and not with point and angle like in "reco_muon.F" !!!!
332 // Needs to add multiple scattering contribution ????
333 Double_t dX =
334 hit->GetHitForRecPtr()->GetNonBendingCoor() - (&param1)->GetNonBendingCoor();
335 Double_t dY =
336 hit->GetHitForRecPtr()->GetBendingCoor() - (&param1)->GetBendingCoor();
337 Chi2 =
338 Chi2 +
339 dX * dX / hit->GetHitForRecPtr()->GetNonBendingReso2() +
340 dY * dY / hit->GetHitForRecPtr()->GetBendingReso2();
341 }
342}
04b5ea16 343
344 //__________________________________________________________________________
345void TrackChi2MCS(Int_t &NParam, Double_t *Gradient, Double_t &Chi2, Double_t *Param, Int_t Flag)
346{
347 // Return the "Chi2" to be minimized with Minuit for track fitting,
348 // with "NParam" parameters
349 // and their current values in array pointed to by "Param".
350 // Assumes that the track hits are sorted according to increasing Z.
351 // Track parameters at each TrackHit are updated accordingly.
352 // Multiple Coulomb scattering is taken into account with covariance matrix.
353 AliMUONTrackParam param1;
354 Chi2 = 0.0; // initialize Chi2
355 // copy of track parameters to be fitted
356 param1 = *trackParamBeingFitted;
357 // Minuit parameters to be fitted into this copy
358 param1.SetInverseBendingMomentum(Param[0]);
359 param1.SetBendingSlope(Param[1]);
360 param1.SetNonBendingSlope(Param[2]);
361 if (NParam == 5) {
362 param1.SetNonBendingCoor(Param[3]);
363 param1.SetBendingCoor(Param[4]);
364 }
365
366 AliMUONTrackHit* hit, hit1, hit2, hit3;
367 Bool_t GoodDeterminant;
368 Int_t hitNumber, hitNumber1, hitNumber2, hitNumber3;
369 Double_t zHit[10], paramBendingCoor[10], paramNonBendingCoor[10], ap[10];
370 Double_t hitBendingCoor[10], hitNonBendingCoor[10];
371 Double_t hitBendingReso2[10], hitNonBendingReso2[10];
372 Int_t numberOfHit = TMath::Min(trackBeingFitted->GetNTrackHits(), 10);
373 TMatrix *covBending = new TMatrix(numberOfHit, numberOfHit);
374 TMatrix *covNonBending = new TMatrix(numberOfHit, numberOfHit);
375
376 // Predicted coordinates and multiple scattering angles are first calculated
377 for (hitNumber = 0; hitNumber < numberOfHit; hitNumber++) {
378 hit = (AliMUONTrackHit*) (*(trackBeingFitted->GetTrackHitsPtr()))[hitNumber];
379 zHit[hitNumber] = hit->GetHitForRecPtr()->GetZ();
380 // do something special if 2 hits with same Z ????
381 // security against infinite loop ????
382 (&param1)->ExtrapToZ(zHit[hitNumber]); // extrapolation
383 hit->SetTrackParam(&param1);
384 paramBendingCoor[hitNumber]= (&param1)->GetBendingCoor();
385 paramNonBendingCoor[hitNumber]= (&param1)->GetNonBendingCoor();
386 hitBendingCoor[hitNumber]= hit->GetHitForRecPtr()->GetBendingCoor();
387 hitNonBendingCoor[hitNumber]= hit->GetHitForRecPtr()->GetNonBendingCoor();
388 hitBendingReso2[hitNumber]= hit->GetHitForRecPtr()->GetBendingReso2();
389 hitNonBendingReso2[hitNumber]= hit->GetHitForRecPtr()->GetNonBendingReso2();
390 ap[hitNumber] = MultipleScatteringAngle2(hit); // multiple scatt. angle ^2
391 }
392
393 // Calculates the covariance matrix
394 for (hitNumber1 = 0; hitNumber1 < numberOfHit; hitNumber1++) {
395 for (hitNumber2 = hitNumber1; hitNumber2 < numberOfHit; hitNumber2++) {
396 (*covBending)(hitNumber1, hitNumber2) = 0;
397 (*covBending)(hitNumber2, hitNumber1) = 0;
398 if (hitNumber1 == hitNumber2){ // diagonal elements
399 (*covBending)(hitNumber2, hitNumber1) =
400 (*covBending)(hitNumber2, hitNumber1) + hitBendingReso2[hitNumber1];
401 }
402 // Multiple Scattering... loop on upstream chambers ??
403 for (hitNumber3 = 0; hitNumber3 < hitNumber1; hitNumber3++){
404 (*covBending)(hitNumber2, hitNumber1) =
405 (*covBending)(hitNumber2, hitNumber1) +
406 ((zHit[hitNumber1] - zHit[hitNumber3]) *
407 (zHit[hitNumber2] - zHit[hitNumber3]) * ap[hitNumber3]);
408 }
409 (*covNonBending)(hitNumber1, hitNumber2) = 0;
410 (*covNonBending)(hitNumber2, hitNumber1) =
411 (*covBending)(hitNumber2, hitNumber1);
412 if (hitNumber1 == hitNumber2) { // diagonal elements
413 (*covNonBending)(hitNumber2, hitNumber1) =
414 (*covNonBending)(hitNumber2, hitNumber1) -
415 hitBendingReso2[hitNumber1] + hitNonBendingReso2[hitNumber1] ;
416 }
417 }
418 }
419
420 // Inverts covariance matrix
421 GoodDeterminant = kTRUE;
422 if (covBending->Determinant() != 0) {
423 covBending->Invert();
424 } else {
425 GoodDeterminant = kFALSE;
426 cout << "Warning in ChiMCS Determinant Bending=0: " << endl;
427 }
428 if (covNonBending->Determinant() != 0){
429 covNonBending->Invert();
430 } else {
431 GoodDeterminant = kFALSE;
432 cout << "Warning in ChiMCS Determinant non Bending=0: " << endl;
433 }
434
435 // Calculates Chi2
436 if (GoodDeterminant) { // with Multiple Scattering if inversion correct
437 for (hitNumber1=0; hitNumber1 < numberOfHit ; hitNumber1++){
438 for (hitNumber2=0; hitNumber2 < numberOfHit; hitNumber2++){
439 Chi2 = Chi2 +
440 ((*covBending)(hitNumber2, hitNumber1) *
441 (hitBendingCoor[hitNumber1] - paramBendingCoor[hitNumber1]) *
442 (hitBendingCoor[hitNumber2] - paramBendingCoor[hitNumber2]));
443 Chi2 = Chi2 +
444 ((*covNonBending)(hitNumber2, hitNumber1) *
445 (hitNonBendingCoor[hitNumber1] - paramNonBendingCoor[hitNumber1]) *
446 (hitNonBendingCoor[hitNumber2] - paramNonBendingCoor[hitNumber2]));
447 }
448 }
449 } else { // without Multiple Scattering if inversion impossible
450 for (hitNumber1=0; hitNumber1 < numberOfHit ; hitNumber1++) {
451 Chi2 = Chi2 +
452 ((hitBendingCoor[hitNumber1] - paramBendingCoor[hitNumber1]) *
453 (hitBendingCoor[hitNumber1] - paramBendingCoor[hitNumber1]) /
454 hitBendingReso2[hitNumber1]);
455 Chi2 = Chi2 +
456 ((hitNonBendingCoor[hitNumber1] - paramNonBendingCoor[hitNumber1]) *
457 (hitNonBendingCoor[hitNumber1] - paramNonBendingCoor[hitNumber1]) /
458 hitNonBendingReso2[hitNumber1]);
459 }
460 }
461
462 delete covBending;
463 delete covNonBending;
464}
465
466Double_t MultipleScatteringAngle2(AliMUONTrackHit *TrackHit)
467{
468 // Returns square of multiple Coulomb scattering angle
469 // at TrackHit pointed to by "TrackHit"
470 Double_t slopeBending, slopeNonBending, radiationLength, inverseBendingMomentum2, inverseTotalMomentum2;
471 Double_t varMultipleScatteringAngle;
472 AliMUONTrackParam *param = TrackHit->GetTrackParam();
473 slopeBending = param->GetBendingSlope();
474 slopeNonBending = param->GetNonBendingSlope();
475 // thickness in radiation length for the current track,
476 // taking local angle into account
477 radiationLength =
478 trackBeingFitted->GetEventReconstructor()->GetChamberThicknessInX0() *
479 TMath::Sqrt(1.0 +
480 slopeBending * slopeBending + slopeNonBending * slopeNonBending);
481 inverseBendingMomentum2 =
482 param->GetInverseBendingMomentum() * param->GetInverseBendingMomentum();
483 inverseTotalMomentum2 =
484 inverseBendingMomentum2 * (1.0 + slopeBending*slopeBending) /
485 (1.0 + slopeBending *slopeBending + slopeNonBending * slopeNonBending);
486 varMultipleScatteringAngle = 0.0136 * (1.0 + 0.038 * TMath::Log(radiationLength));
487 varMultipleScatteringAngle = inverseTotalMomentum2 * radiationLength *
488 varMultipleScatteringAngle * varMultipleScatteringAngle;
489 return varMultipleScatteringAngle;
490}