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 Revision 1.5 2000/07/18 16:04:06 gosset
19 AliMUONEventReconstructor package:
20 * a few minor modifications and more comments
22 * right sign for Z of raw clusters
23 * right loop over chambers inside station
24 * symmetrized covariance matrix for measurements (TrackChi2MCS)
25 * right sign of charge in extrapolation (ExtrapToZ)
26 * right zEndAbsorber for Branson correction below 3 degrees
27 * use of TVirtualFitter instead of TMinuit for AliMUONTrack::Fit
28 * no parameter for AliMUONTrack::Fit() but more fit parameters in Track object
30 Revision 1.4 2000/07/03 07:53:31 morsch
31 Double declaration problem on HP solved.
33 Revision 1.3 2000/06/30 10:15:48 gosset
34 Changes to EventReconstructor...:
35 precision fit with multiple Coulomb scattering;
36 extrapolation to vertex with Branson correction in absorber (JPC)
38 Revision 1.2 2000/06/15 07:58:49 morsch
39 Code from MUON-dev joined
41 Revision 1.1.2.3 2000/06/09 21:03:09 morsch
42 Make includes consistent with new file structure.
44 Revision 1.1.2.2 2000/06/09 12:58:05 gosset
45 Removed comment beginnings in Log sections of .cxx files
46 Suppressed most violations of coding rules
48 Revision 1.1.2.1 2000/06/07 14:44:53 gosset
49 Addition of files for track reconstruction in C++
52 //__________________________________________________________________________
54 // Track parameters in ALICE dimuon spectrometer
55 //__________________________________________________________________________
59 #include "AliCallf77.h"
61 #include "AliMUONHitForRec.h"
62 #include "AliMUONSegment.h"
63 #include "AliMUONTrackParam.h"
64 #include "AliMUONChamber.h"
67 ClassImp(AliMUONTrackParam) // Class implementation in ROOT context
69 // A few calls in Fortran or from Fortran (extrap.F).
70 // Needed, instead of calls to Geant subroutines,
71 // because double precision is necessary for track fit converging with Minuit.
72 // The "extrap" functions should be translated into C++ ????
74 # define extrap_onestep_helix extrap_onestep_helix_
75 # define extrap_onestep_helix3 extrap_onestep_helix3_
76 # define extrap_onestep_rungekutta extrap_onestep_rungekutta_
77 # define gufld_double gufld_double_
79 # define extrap_onestep_helix EXTRAP_ONESTEP_HELIX
80 # define extrap_onestep_helix3 EXTRAP_ONESTEP_HELIX3
81 # define extrap_onestep_rungekutta EXTRAP_ONESTEP_RUNGEKUTTA
82 # define gufld_double GUFLD_DOUBLE
86 void type_of_call extrap_onestep_helix
87 (Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New);
89 void type_of_call extrap_onestep_helix3
90 (Double_t &Field, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New);
92 void type_of_call extrap_onestep_rungekutta
93 (Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New);
95 void type_of_call gufld_double(Double_t *Position, Double_t *Field) {
96 // interface to "gAlice->Field()->Field" for arguments in double precision
98 x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2];
99 gAlice->Field()->Field(x, b);
100 Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2];
104 // Inline functions for Get and Set: inline removed because it does not work !!!!
105 Double_t AliMUONTrackParam::GetInverseBendingMomentum(void) {
106 // Get fInverseBendingMomentum
107 return fInverseBendingMomentum;}
108 void AliMUONTrackParam::SetInverseBendingMomentum(Double_t InverseBendingMomentum) {
109 // Set fInverseBendingMomentum
110 fInverseBendingMomentum = InverseBendingMomentum;}
111 Double_t AliMUONTrackParam::GetBendingSlope(void) {
113 return fBendingSlope;}
114 void AliMUONTrackParam::SetBendingSlope(Double_t BendingSlope) {
116 fBendingSlope = BendingSlope;}
117 Double_t AliMUONTrackParam::GetNonBendingSlope(void) {
118 // Get fNonBendingSlope
119 return fNonBendingSlope;}
120 void AliMUONTrackParam::SetNonBendingSlope(Double_t NonBendingSlope) {
121 // Set fNonBendingSlope
122 fNonBendingSlope = NonBendingSlope;}
123 Double_t AliMUONTrackParam::GetZ(void) {
126 void AliMUONTrackParam::SetZ(Double_t Z) {
129 Double_t AliMUONTrackParam::GetBendingCoor(void) {
131 return fBendingCoor;}
132 void AliMUONTrackParam::SetBendingCoor(Double_t BendingCoor) {
134 fBendingCoor = BendingCoor;}
135 Double_t AliMUONTrackParam::GetNonBendingCoor(void) {
136 // Get fNonBendingCoor
137 return fNonBendingCoor;}
138 void AliMUONTrackParam::SetNonBendingCoor(Double_t NonBendingCoor) {
139 // Set fNonBendingCoor
140 fNonBendingCoor = NonBendingCoor;}
142 //__________________________________________________________________________
143 void AliMUONTrackParam::ExtrapToZ(Double_t Z)
145 // Track parameter extrapolation to the plane at "Z".
146 // On return, the track parameters resulting from the extrapolation
147 // replace the current track parameters.
148 if (this->fZ == Z) return; // nothing to be done if same Z
149 Double_t forwardBackward; // +1 if forward, -1 if backward
150 if (Z > this->fZ) forwardBackward = 1.0;
151 else forwardBackward = -1.0;
152 Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ????
153 Int_t iGeant3, stepNumber;
154 Int_t maxStepNumber = 5000; // in parameter ????
155 // For safety: return kTRUE or kFALSE ????
156 // Parameter vector for calling EXTRAP_ONESTEP
157 SetGeant3Parameters(vGeant3, forwardBackward);
158 // sign of charge (sign of fInverseBendingMomentum if forward motion)
159 // must be changed if backward extrapolation
160 Double_t chargeExtrap = forwardBackward *
161 TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum);
162 Double_t stepLength = 6.0; // in parameter ????
163 // Extrapolation loop
165 while (((forwardBackward * (vGeant3[2] - Z)) <= 0.0) &&
166 (stepNumber < maxStepNumber)) {
168 // Option for switching between helix and Runge-Kutta ????
169 // extrap_onestep_rungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New);
170 extrap_onestep_helix(chargeExtrap, stepLength, vGeant3, vGeant3New);
171 if ((forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z
172 // better use TArray ????
173 for (iGeant3 = 0; iGeant3 < 7; iGeant3++)
174 {vGeant3[iGeant3] = vGeant3New[iGeant3];}
176 // check maxStepNumber ????
177 // Interpolation back to exact Z (2nd order)
178 // should be in function ???? using TArray ????
179 Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2
180 Double_t dZ1i = Z - vGeant3[2]; // 1-i
181 Double_t dZi2 = vGeant3New[2] - Z; // i->2
182 Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12;
184 ((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12;
185 Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12;
187 ((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12;
188 vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X
189 vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y
191 Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i);
192 Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i);
193 // (PX, PY, PZ)/PTOT assuming forward motion
195 1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT
196 vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT
197 vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT
198 // Track parameters from Geant3 parameters,
199 // with charge back for forward motion
200 GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward);
203 //__________________________________________________________________________
204 void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward)
206 // Set vector of Geant3 parameters pointed to by "VGeant3"
207 // from track parameters in current AliMUONTrackParam.
208 // Since AliMUONTrackParam is only geometry, one uses "ForwardBackward"
209 // to know whether the particle is going forward (+1) or backward (-1).
210 VGeant3[0] = this->fNonBendingCoor; // X
211 VGeant3[1] = this->fBendingCoor; // Y
212 VGeant3[2] = this->fZ; // Z
213 Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum);
215 pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope);
217 TMath::Sqrt(pYZ * pYZ +
218 pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT
219 VGeant3[5] = ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT
220 VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT
221 VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT
224 //__________________________________________________________________________
225 void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge)
227 // Get track parameters in current AliMUONTrackParam
228 // from Geant3 parameters pointed to by "VGeant3",
229 // assumed to be calculated for forward motion in Z.
230 // "InverseBendingMomentum" is signed with "Charge".
231 this->fNonBendingCoor = VGeant3[0]; // X
232 this->fBendingCoor = VGeant3[1]; // Y
233 this->fZ = VGeant3[2]; // Z
234 Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]);
235 this->fInverseBendingMomentum = Charge / pYZ;
236 this->fBendingSlope = VGeant3[4] / VGeant3[5];
237 this->fNonBendingSlope = VGeant3[3] / VGeant3[5];
240 //__________________________________________________________________________
241 void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam)
243 // Track parameters extrapolated from current track parameters ("this")
244 // to both chambers of the station(0..) "Station"
245 // are returned in the array (dimension 2) of track parameters
246 // pointed to by "TrackParam" (index 0 and 1 for first and second chambers).
247 Double_t extZ[2], z1, z2;
249 AliMUON *pMUON = (AliMUON*) gAlice->GetModule("MUON"); // necessary ????
250 // range of Station to be checked ????
251 z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber
252 z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber
253 // First and second Z to extrapolate at
254 if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;}
255 else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;}
257 cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl;
258 cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 <<
259 ") and z2 (" << z2 << ") of station(0..) " << Station << endl;
263 // copy of track parameters
264 TrackParam[i1] = *this;
265 // first extrapolation
266 (&(TrackParam[i1]))->ExtrapToZ(extZ[0]);
267 TrackParam[i2] = TrackParam[i1];
268 // second extrapolation
269 (&(TrackParam[i2]))->ExtrapToZ(extZ[1]);
273 //__________________________________________________________________________
274 void AliMUONTrackParam::ExtrapToVertex()
276 // Extrapolation to the vertex.
277 // Returns the track parameters resulting from the extrapolation,
278 // in the current TrackParam.
279 // Changes parameters according to Branson correction through the absorber
281 Double_t zAbsorber = 503.0; // to be coherent with the Geant absorber geometry !!!!
282 // Extrapolates track parameters upstream to the "Z" end of the front absorber
283 ExtrapToZ(zAbsorber);
284 // Makes Branson correction (multiple scattering + energy loss)
288 //__________________________________________________________________________
289 void AliMUONTrackParam::BransonCorrection()
291 // Branson correction of track parameters
292 // the entry parameters have to be calculated at the end of the absorber
293 Double_t zEndAbsorber, zBP, xBP, yBP;
294 Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
296 // Would it be possible to calculate all that from Geant configuration ????
297 // and to get the Branson parameters from a function in ABSO module ????
298 // with an eventual contribution from other detectors like START ????
299 // Radiation lengths outer part theta > 3 degres
300 static Double_t x01[9] = { 18.8, // C (cm)
301 10.397, // Concrete (cm)
303 47.26, // Polyethylene (cm)
305 47.26, // Polyethylene (cm)
307 47.26, // Polyethylene (cm)
308 0.56 }; // Plomb (cm)
309 // inner part theta < 3 degres
310 static Double_t x02[3] = { 18.8, // C (cm)
311 10.397, // Concrete (cm)
313 // z positions of the materials inside the absober outer part theta > 3 degres
314 static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 };
315 // inner part theta < 3 degres
316 static Double_t z2[4] = { 90, 315, 467, 503 };
317 static Bool_t first = kTRUE;
318 static Double_t zBP1, zBP2, rLimit;
319 // Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call)
326 for (iBound = 0; iBound < 9; iBound++) {
328 (z1[iBound+1] * z1[iBound+1] * z1[iBound+1] -
329 z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound];
331 (z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound];
333 zBP1 = (2.0 * aNBP) / (3.0 * aDBP);
336 for (iBound = 0; iBound < 3; iBound++) {
338 (z2[iBound+1] * z2[iBound+1] * z2[iBound+1] -
339 z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound];
341 (z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound];
343 zBP2 = (2.0 * aNBP) / (3.0 * aDBP);
344 rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
347 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
349 if (fInverseBendingMomentum < 0) sign = -1;
350 pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope));
351 pX = pZ * fNonBendingSlope;
352 pY = pZ * fBendingSlope;
353 pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX);
354 xEndAbsorber = fNonBendingCoor;
355 yEndAbsorber = fBendingCoor;
356 radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
358 if (radiusEndAbsorber2 > rLimit*rLimit) {
359 zEndAbsorber = z1[9];
362 zEndAbsorber = z2[3];
366 xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
367 yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
369 // new parameters after Branson and energy loss corrections
370 pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP);
373 fBendingSlope = pY / pZ;
374 fNonBendingSlope = pX / pZ;
376 pT = TMath::Sqrt(pX * pX + pY * pY);
377 theta = TMath::ATan2(pT, pZ);
379 TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
381 fInverseBendingMomentum = (sign / pTotal) *
383 fBendingSlope * fBendingSlope +
384 fNonBendingSlope * fNonBendingSlope) /
385 TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
387 // vertex position at (0,0,0)
388 // should be taken from vertex measurement ???
394 //__________________________________________________________________________
395 Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t rLimit, Double_t pTotal, Double_t theta, Double_t xEndAbsorber, Double_t yEndAbsorber)
397 // Returns the total momentum corrected from energy loss in the front absorber
398 Double_t deltaP, pTotalCorrected;
400 Double_t radiusEndAbsorber2 =
401 xEndAbsorber *xEndAbsorber + yEndAbsorber * yEndAbsorber;
402 // Parametrization to be redone according to change of absorber material ????
403 // See remark in function BransonCorrection !!!!
404 // The name is not so good, and there are many arguments !!!!
405 if (radiusEndAbsorber2 < rLimit * rLimit) {
407 deltaP = 2.737 + 0.0494 * pTotal - 0.001123 * pTotal * pTotal;
409 deltaP = 3.0643 + 0.01346 *pTotal;
413 deltaP = 2.1380 + 0.0351 * pTotal - 0.000853 * pTotal * pTotal;
415 deltaP = 2.407 + 0.00702 * pTotal;
418 pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
419 return pTotalCorrected;