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. *
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8 * documentation strictly for non-commercial purposes is hereby granted *
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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 Revision 1.7 2000/10/02 16:58:29 egangler
19 Cleaning of the code :
22 -> some useless includes removed or replaced by "class" statement
24 Revision 1.6 2000/09/19 09:49:50 gosset
25 AliMUONEventReconstructor package
26 * track extrapolation independent from reco_muon.F, use of AliMagF...
27 * possibility to use new magnetic field (automatic from generated root file)
29 Revision 1.5 2000/07/18 16:04:06 gosset
30 AliMUONEventReconstructor package:
31 * a few minor modifications and more comments
33 * right sign for Z of raw clusters
34 * right loop over chambers inside station
35 * symmetrized covariance matrix for measurements (TrackChi2MCS)
36 * right sign of charge in extrapolation (ExtrapToZ)
37 * right zEndAbsorber for Branson correction below 3 degrees
38 * use of TVirtualFitter instead of TMinuit for AliMUONTrack::Fit
39 * no parameter for AliMUONTrack::Fit() but more fit parameters in Track object
41 Revision 1.4 2000/07/03 07:53:31 morsch
42 Double declaration problem on HP solved.
44 Revision 1.3 2000/06/30 10:15:48 gosset
45 Changes to EventReconstructor...:
46 precision fit with multiple Coulomb scattering;
47 extrapolation to vertex with Branson correction in absorber (JPC)
49 Revision 1.2 2000/06/15 07:58:49 morsch
50 Code from MUON-dev joined
52 Revision 1.1.2.3 2000/06/09 21:03:09 morsch
53 Make includes consistent with new file structure.
55 Revision 1.1.2.2 2000/06/09 12:58:05 gosset
56 Removed comment beginnings in Log sections of .cxx files
57 Suppressed most violations of coding rules
59 Revision 1.1.2.1 2000/06/07 14:44:53 gosset
60 Addition of files for track reconstruction in C++
63 //__________________________________________________________________________
65 // Track parameters in ALICE dimuon spectrometer
66 //__________________________________________________________________________
70 #include "AliCallf77.h"
72 #include "AliMUONHitForRec.h"
73 #include "AliMUONSegment.h"
74 #include "AliMUONTrackParam.h"
75 #include "AliMUONChamber.h"
79 ClassImp(AliMUONTrackParam) // Class implementation in ROOT context
81 // A few calls in Fortran or from Fortran (extrap.F).
82 // Needed, instead of calls to Geant subroutines,
83 // because double precision is necessary for track fit converging with Minuit.
84 // The "extrap" functions should be translated into C++ ????
86 # define extrap_onestep_helix extrap_onestep_helix_
87 # define extrap_onestep_helix3 extrap_onestep_helix3_
88 # define extrap_onestep_rungekutta extrap_onestep_rungekutta_
89 # define gufld_double gufld_double_
91 # define extrap_onestep_helix EXTRAP_ONESTEP_HELIX
92 # define extrap_onestep_helix3 EXTRAP_ONESTEP_HELIX3
93 # define extrap_onestep_rungekutta EXTRAP_ONESTEP_RUNGEKUTTA
94 # define gufld_double GUFLD_DOUBLE
98 void type_of_call extrap_onestep_helix
99 (Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New);
101 void type_of_call extrap_onestep_helix3
102 (Double_t &Field, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New);
104 void type_of_call extrap_onestep_rungekutta
105 (Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New);
107 void type_of_call gufld_double(Double_t *Position, Double_t *Field) {
108 // interface to "gAlice->Field()->Field" for arguments in double precision
110 x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2];
111 gAlice->Field()->Field(x, b);
112 Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2];
116 // Inline functions for Get and Set: inline removed because it does not work !!!!
117 Double_t AliMUONTrackParam::GetInverseBendingMomentum(void) {
118 // Get fInverseBendingMomentum
119 return fInverseBendingMomentum;}
120 void AliMUONTrackParam::SetInverseBendingMomentum(Double_t InverseBendingMomentum) {
121 // Set fInverseBendingMomentum
122 fInverseBendingMomentum = InverseBendingMomentum;}
123 Double_t AliMUONTrackParam::GetBendingSlope(void) {
125 return fBendingSlope;}
126 void AliMUONTrackParam::SetBendingSlope(Double_t BendingSlope) {
128 fBendingSlope = BendingSlope;}
129 Double_t AliMUONTrackParam::GetNonBendingSlope(void) {
130 // Get fNonBendingSlope
131 return fNonBendingSlope;}
132 void AliMUONTrackParam::SetNonBendingSlope(Double_t NonBendingSlope) {
133 // Set fNonBendingSlope
134 fNonBendingSlope = NonBendingSlope;}
135 Double_t AliMUONTrackParam::GetZ(void) {
138 void AliMUONTrackParam::SetZ(Double_t Z) {
141 Double_t AliMUONTrackParam::GetBendingCoor(void) {
143 return fBendingCoor;}
144 void AliMUONTrackParam::SetBendingCoor(Double_t BendingCoor) {
146 fBendingCoor = BendingCoor;}
147 Double_t AliMUONTrackParam::GetNonBendingCoor(void) {
148 // Get fNonBendingCoor
149 return fNonBendingCoor;}
150 void AliMUONTrackParam::SetNonBendingCoor(Double_t NonBendingCoor) {
151 // Set fNonBendingCoor
152 fNonBendingCoor = NonBendingCoor;}
154 //__________________________________________________________________________
155 void AliMUONTrackParam::ExtrapToZ(Double_t Z)
157 // Track parameter extrapolation to the plane at "Z".
158 // On return, the track parameters resulting from the extrapolation
159 // replace the current track parameters.
160 if (this->fZ == Z) return; // nothing to be done if same Z
161 Double_t forwardBackward; // +1 if forward, -1 if backward
162 if (Z > this->fZ) forwardBackward = 1.0;
163 else forwardBackward = -1.0;
164 Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ????
165 Int_t iGeant3, stepNumber;
166 Int_t maxStepNumber = 5000; // in parameter ????
167 // For safety: return kTRUE or kFALSE ????
168 // Parameter vector for calling EXTRAP_ONESTEP
169 SetGeant3Parameters(vGeant3, forwardBackward);
170 // sign of charge (sign of fInverseBendingMomentum if forward motion)
171 // must be changed if backward extrapolation
172 Double_t chargeExtrap = forwardBackward *
173 TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum);
174 Double_t stepLength = 6.0; // in parameter ????
175 // Extrapolation loop
177 while (((forwardBackward * (vGeant3[2] - Z)) <= 0.0) &&
178 (stepNumber < maxStepNumber)) {
180 // Option for switching between helix and Runge-Kutta ????
181 // extrap_onestep_rungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New);
182 extrap_onestep_helix(chargeExtrap, stepLength, vGeant3, vGeant3New);
183 if ((forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z
184 // better use TArray ????
185 for (iGeant3 = 0; iGeant3 < 7; iGeant3++)
186 {vGeant3[iGeant3] = vGeant3New[iGeant3];}
188 // check maxStepNumber ????
189 // Interpolation back to exact Z (2nd order)
190 // should be in function ???? using TArray ????
191 Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2
192 Double_t dZ1i = Z - vGeant3[2]; // 1-i
193 Double_t dZi2 = vGeant3New[2] - Z; // i->2
194 Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12;
196 ((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12;
197 Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12;
199 ((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12;
200 vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X
201 vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y
203 Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i);
204 Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i);
205 // (PX, PY, PZ)/PTOT assuming forward motion
207 1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT
208 vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT
209 vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT
210 // Track parameters from Geant3 parameters,
211 // with charge back for forward motion
212 GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward);
215 //__________________________________________________________________________
216 void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward)
218 // Set vector of Geant3 parameters pointed to by "VGeant3"
219 // from track parameters in current AliMUONTrackParam.
220 // Since AliMUONTrackParam is only geometry, one uses "ForwardBackward"
221 // to know whether the particle is going forward (+1) or backward (-1).
222 VGeant3[0] = this->fNonBendingCoor; // X
223 VGeant3[1] = this->fBendingCoor; // Y
224 VGeant3[2] = this->fZ; // Z
225 Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum);
227 pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope);
229 TMath::Sqrt(pYZ * pYZ +
230 pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT
231 VGeant3[5] = ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT
232 VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT
233 VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT
236 //__________________________________________________________________________
237 void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge)
239 // Get track parameters in current AliMUONTrackParam
240 // from Geant3 parameters pointed to by "VGeant3",
241 // assumed to be calculated for forward motion in Z.
242 // "InverseBendingMomentum" is signed with "Charge".
243 this->fNonBendingCoor = VGeant3[0]; // X
244 this->fBendingCoor = VGeant3[1]; // Y
245 this->fZ = VGeant3[2]; // Z
246 Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]);
247 this->fInverseBendingMomentum = Charge / pYZ;
248 this->fBendingSlope = VGeant3[4] / VGeant3[5];
249 this->fNonBendingSlope = VGeant3[3] / VGeant3[5];
252 //__________________________________________________________________________
253 void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam)
255 // Track parameters extrapolated from current track parameters ("this")
256 // to both chambers of the station(0..) "Station"
257 // are returned in the array (dimension 2) of track parameters
258 // pointed to by "TrackParam" (index 0 and 1 for first and second chambers).
259 Double_t extZ[2], z1, z2;
260 Int_t i1 = -1, i2 = -1; // = -1 to avoid compilation warnings
261 AliMUON *pMUON = (AliMUON*) gAlice->GetModule("MUON"); // necessary ????
262 // range of Station to be checked ????
263 z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber
264 z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber
265 // First and second Z to extrapolate at
266 if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;}
267 else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;}
269 cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl;
270 cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 <<
271 ") and z2 (" << z2 << ") of station(0..) " << Station << endl;
275 // copy of track parameters
276 TrackParam[i1] = *this;
277 // first extrapolation
278 (&(TrackParam[i1]))->ExtrapToZ(extZ[0]);
279 TrackParam[i2] = TrackParam[i1];
280 // second extrapolation
281 (&(TrackParam[i2]))->ExtrapToZ(extZ[1]);
285 //__________________________________________________________________________
286 void AliMUONTrackParam::ExtrapToVertex()
288 // Extrapolation to the vertex.
289 // Returns the track parameters resulting from the extrapolation,
290 // in the current TrackParam.
291 // Changes parameters according to Branson correction through the absorber
293 Double_t zAbsorber = 503.0; // to be coherent with the Geant absorber geometry !!!!
294 // Extrapolates track parameters upstream to the "Z" end of the front absorber
295 ExtrapToZ(zAbsorber);
296 // Makes Branson correction (multiple scattering + energy loss)
300 //__________________________________________________________________________
301 void AliMUONTrackParam::BransonCorrection()
303 // Branson correction of track parameters
304 // the entry parameters have to be calculated at the end of the absorber
305 Double_t zEndAbsorber, zBP, xBP, yBP;
306 Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
308 // Would it be possible to calculate all that from Geant configuration ????
309 // and to get the Branson parameters from a function in ABSO module ????
310 // with an eventual contribution from other detectors like START ????
311 // Radiation lengths outer part theta > 3 degres
312 static Double_t x01[9] = { 18.8, // C (cm)
313 10.397, // Concrete (cm)
315 47.26, // Polyethylene (cm)
317 47.26, // Polyethylene (cm)
319 47.26, // Polyethylene (cm)
320 0.56 }; // Plomb (cm)
321 // inner part theta < 3 degres
322 static Double_t x02[3] = { 18.8, // C (cm)
323 10.397, // Concrete (cm)
325 // z positions of the materials inside the absober outer part theta > 3 degres
326 static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 };
327 // inner part theta < 3 degres
328 static Double_t z2[4] = { 90, 315, 467, 503 };
329 static Bool_t first = kTRUE;
330 static Double_t zBP1, zBP2, rLimit;
331 // Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call)
338 for (iBound = 0; iBound < 9; iBound++) {
340 (z1[iBound+1] * z1[iBound+1] * z1[iBound+1] -
341 z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound];
343 (z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound];
345 zBP1 = (2.0 * aNBP) / (3.0 * aDBP);
348 for (iBound = 0; iBound < 3; iBound++) {
350 (z2[iBound+1] * z2[iBound+1] * z2[iBound+1] -
351 z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound];
353 (z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound];
355 zBP2 = (2.0 * aNBP) / (3.0 * aDBP);
356 rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
359 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
361 if (fInverseBendingMomentum < 0) sign = -1;
362 pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope));
363 pX = pZ * fNonBendingSlope;
364 pY = pZ * fBendingSlope;
365 pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX);
366 xEndAbsorber = fNonBendingCoor;
367 yEndAbsorber = fBendingCoor;
368 radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
370 if (radiusEndAbsorber2 > rLimit*rLimit) {
371 zEndAbsorber = z1[9];
374 zEndAbsorber = z2[3];
378 xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
379 yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
381 // new parameters after Branson and energy loss corrections
382 pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP);
385 fBendingSlope = pY / pZ;
386 fNonBendingSlope = pX / pZ;
388 pT = TMath::Sqrt(pX * pX + pY * pY);
389 theta = TMath::ATan2(pT, pZ);
391 TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
393 fInverseBendingMomentum = (sign / pTotal) *
395 fBendingSlope * fBendingSlope +
396 fNonBendingSlope * fNonBendingSlope) /
397 TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
399 // vertex position at (0,0,0)
400 // should be taken from vertex measurement ???
406 //__________________________________________________________________________
407 Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t rLimit, Double_t pTotal, Double_t theta, Double_t xEndAbsorber, Double_t yEndAbsorber)
409 // Returns the total momentum corrected from energy loss in the front absorber
410 Double_t deltaP, pTotalCorrected;
412 Double_t radiusEndAbsorber2 =
413 xEndAbsorber *xEndAbsorber + yEndAbsorber * yEndAbsorber;
414 // Parametrization to be redone according to change of absorber material ????
415 // See remark in function BransonCorrection !!!!
416 // The name is not so good, and there are many arguments !!!!
417 if (radiusEndAbsorber2 < rLimit * rLimit) {
419 deltaP = 2.737 + 0.0494 * pTotal - 0.001123 * pTotal * pTotal;
421 deltaP = 3.0643 + 0.01346 *pTotal;
425 deltaP = 2.1380 + 0.0351 * pTotal - 0.000853 * pTotal * pTotal;
427 deltaP = 2.407 + 0.00702 * pTotal;
430 pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
431 return pTotalCorrected;