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 ///////////////////////////////////////////////////
26 ///////////////////////////////////////////////////
28 //#include <Riostream.h>
30 #include "AliMUONTrackParam.h"
31 #include "AliMUONConstants.h"
32 #include "AliESDMuonTrack.h"
35 #include "AliTracker.h"
36 #include "AliMUONHitForRec.h"
38 ClassImp(AliMUONTrackParam) // Class implementation in ROOT context
40 //_________________________________________________________________________
41 AliMUONTrackParam::AliMUONTrackParam()
43 fInverseBendingMomentum(0.),
53 // get field from outside
54 fkField = AliTracker::GetFieldMap();
55 if (!fkField) AliFatal("No field available");
58 //_________________________________________________________________________
59 AliMUONTrackParam::AliMUONTrackParam(const AliMUONTrackParam& theMUONTrackParam)
60 : TObject(theMUONTrackParam),
61 fInverseBendingMomentum(theMUONTrackParam.fInverseBendingMomentum),
62 fBendingSlope(theMUONTrackParam.fBendingSlope),
63 fNonBendingSlope(theMUONTrackParam.fNonBendingSlope),
64 fZ(theMUONTrackParam.fZ),
65 fBendingCoor(theMUONTrackParam.fBendingCoor),
66 fNonBendingCoor(theMUONTrackParam.fNonBendingCoor),
67 fkField(theMUONTrackParam.fkField),
68 fHitForRecPtr(theMUONTrackParam.fHitForRecPtr)
73 //_________________________________________________________________________
74 AliMUONTrackParam& AliMUONTrackParam::operator=(const AliMUONTrackParam& theMUONTrackParam)
76 /// Asignment operator
77 if (this == &theMUONTrackParam)
80 // base class assignement
81 TObject::operator=(theMUONTrackParam);
83 fInverseBendingMomentum = theMUONTrackParam.fInverseBendingMomentum;
84 fBendingSlope = theMUONTrackParam.fBendingSlope;
85 fNonBendingSlope = theMUONTrackParam.fNonBendingSlope;
86 fZ = theMUONTrackParam.fZ;
87 fBendingCoor = theMUONTrackParam.fBendingCoor;
88 fNonBendingCoor = theMUONTrackParam.fNonBendingCoor;
89 fkField = theMUONTrackParam.fkField;
90 fHitForRecPtr = theMUONTrackParam.fHitForRecPtr;
95 //__________________________________________________________________________
96 AliMUONTrackParam::~AliMUONTrackParam()
99 /// Update the number of TrackHit's connected to the attached HitForRec if any
100 if (fHitForRecPtr) fHitForRecPtr->SetNTrackHits(fHitForRecPtr->GetNTrackHits() - 1); // decrement NTrackHits of hit
103 //__________________________________________________________________________
104 void AliMUONTrackParam::SetTrackParam(AliMUONTrackParam& theMUONTrackParam)
106 /// Set track parameters from "TrackParam" leaving pointer to fHitForRecPtr unchanged
107 fInverseBendingMomentum = theMUONTrackParam.fInverseBendingMomentum;
108 fBendingSlope = theMUONTrackParam.fBendingSlope;
109 fNonBendingSlope = theMUONTrackParam.fNonBendingSlope;
110 fZ = theMUONTrackParam.fZ;
111 fBendingCoor = theMUONTrackParam.fBendingCoor;
112 fNonBendingCoor = theMUONTrackParam.fNonBendingCoor;
116 //__________________________________________________________________________
117 AliMUONHitForRec* AliMUONTrackParam::GetHitForRecPtr(void) const
119 /// return pointer to HitForRec attached to the current TrackParam
120 /// this method should not be called when fHitForRecPtr == NULL
121 if (!fHitForRecPtr) AliWarning("AliMUONTrackParam::GetHitForRecPtr: fHitForRecPtr == NULL");
122 return fHitForRecPtr;
125 //__________________________________________________________________________
126 Int_t AliMUONTrackParam::Compare(const TObject* TrackParam) const
128 /// "Compare" function to sort with decreasing Z (spectro. muon Z <0).
129 /// Returns 1 (0, -1) if Z of current TrackHit
130 /// is smaller than (equal to, larger than) Z of TrackHit
131 if (fHitForRecPtr->GetZ() < ((AliMUONTrackParam*)TrackParam)->fHitForRecPtr->GetZ()) return(1);
132 else if (fHitForRecPtr->GetZ() == ((AliMUONTrackParam*)TrackParam)->fHitForRecPtr->GetZ()) return(0);
136 //_________________________________________________________________________
137 void AliMUONTrackParam::GetParamFrom(const AliESDMuonTrack& esdMuonTrack)
139 /// assigned value form ESD track.
140 fInverseBendingMomentum = esdMuonTrack.GetInverseBendingMomentum();
141 fBendingSlope = TMath::Tan(esdMuonTrack.GetThetaY());
142 fNonBendingSlope = TMath::Tan(esdMuonTrack.GetThetaX());
143 fZ = esdMuonTrack.GetZ();
144 fBendingCoor = esdMuonTrack.GetBendingCoor();
145 fNonBendingCoor = esdMuonTrack.GetNonBendingCoor();
148 //_________________________________________________________________________
149 void AliMUONTrackParam::SetParamFor(AliESDMuonTrack& esdMuonTrack)
151 /// assigned value form ESD track.
152 esdMuonTrack.SetInverseBendingMomentum(fInverseBendingMomentum);
153 esdMuonTrack.SetThetaX(TMath::ATan(fNonBendingSlope));
154 esdMuonTrack.SetThetaY(TMath::ATan(fBendingSlope));
155 esdMuonTrack.SetZ(fZ);
156 esdMuonTrack.SetBendingCoor(fBendingCoor);
157 esdMuonTrack.SetNonBendingCoor(fNonBendingCoor);
160 //__________________________________________________________________________
161 void AliMUONTrackParam::ExtrapToZ(Double_t Z)
163 /// Track parameter extrapolation to the plane at "Z".
164 /// On return, the track parameters resulting from the extrapolation
165 /// replace the current track parameters.
166 if (this->fZ == Z) return; // nothing to be done if same Z
167 Double_t forwardBackward; // +1 if forward, -1 if backward
168 if (Z < this->fZ) forwardBackward = 1.0; // spectro. z<0
169 else forwardBackward = -1.0;
170 Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ????
171 Int_t iGeant3, stepNumber;
172 Int_t maxStepNumber = 5000; // in parameter ????
173 // For safety: return kTRUE or kFALSE ????
174 // Parameter vector for calling EXTRAP_ONESTEP
175 SetGeant3Parameters(vGeant3, forwardBackward);
176 // sign of charge (sign of fInverseBendingMomentum if forward motion)
177 // must be changed if backward extrapolation
178 Double_t chargeExtrap = forwardBackward *
179 TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum);
180 Double_t stepLength = 6.0; // in parameter ????
181 // Extrapolation loop
183 while (((-forwardBackward * (vGeant3[2] - Z)) <= 0.0) && // spectro. z<0
184 (stepNumber < maxStepNumber)) {
186 // Option for switching between helix and Runge-Kutta ????
187 //ExtrapOneStepRungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New);
188 ExtrapOneStepHelix(chargeExtrap, stepLength, vGeant3, vGeant3New);
189 if ((-forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z spectro. z<0
190 // better use TArray ????
191 for (iGeant3 = 0; iGeant3 < 7; iGeant3++)
192 {vGeant3[iGeant3] = vGeant3New[iGeant3];}
194 // check maxStepNumber ????
195 // Interpolation back to exact Z (2nd order)
196 // should be in function ???? using TArray ????
197 Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2
198 if (TMath::Abs(dZ12) > 0) {
199 Double_t dZ1i = Z - vGeant3[2]; // 1-i
200 Double_t dZi2 = vGeant3New[2] - Z; // i->2
201 Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12;
203 ((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12;
204 Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12;
206 ((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12;
207 vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X
208 vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y
210 Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i);
211 Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i);
212 // (PX, PY, PZ)/PTOT assuming forward motion
214 1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT
215 vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT
216 vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT
218 AliWarning(Form("Extrap. to Z not reached, Z = %f",Z));
220 // Track parameters from Geant3 parameters,
221 // with charge back for forward motion
222 GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward);
225 //__________________________________________________________________________
226 void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward)
228 /// Set vector of Geant3 parameters pointed to by "VGeant3"
229 /// from track parameters in current AliMUONTrackParam.
230 /// Since AliMUONTrackParam is only geometry, one uses "ForwardBackward"
231 /// to know whether the particle is going forward (+1) or backward (-1).
232 VGeant3[0] = this->fNonBendingCoor; // X
233 VGeant3[1] = this->fBendingCoor; // Y
234 VGeant3[2] = this->fZ; // Z
235 Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum);
237 pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope);
239 TMath::Sqrt(pYZ * pYZ +
240 pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT
241 VGeant3[5] = -ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT spectro. z<0
242 VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT
243 VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT
246 //__________________________________________________________________________
247 void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge)
249 /// Get track parameters in current AliMUONTrackParam
250 /// from Geant3 parameters pointed to by "VGeant3",
251 /// assumed to be calculated for forward motion in Z.
252 /// "InverseBendingMomentum" is signed with "Charge".
253 this->fNonBendingCoor = VGeant3[0]; // X
254 this->fBendingCoor = VGeant3[1]; // Y
255 this->fZ = VGeant3[2]; // Z
256 Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]);
257 this->fInverseBendingMomentum = Charge / pYZ;
258 this->fBendingSlope = VGeant3[4] / VGeant3[5];
259 this->fNonBendingSlope = VGeant3[3] / VGeant3[5];
262 //__________________________________________________________________________
263 void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam)
265 /// Track parameters extrapolated from current track parameters ("this")
266 /// to both chambers of the station(0..) "Station"
267 /// are returned in the array (dimension 2) of track parameters
268 /// pointed to by "TrackParam" (index 0 and 1 for first and second chambers).
269 Double_t extZ[2], z1, z2;
270 Int_t i1 = -1, i2 = -1; // = -1 to avoid compilation warnings
271 // range of Station to be checked ????
272 z1 = AliMUONConstants::DefaultChamberZ(2 * Station);
273 z2 = AliMUONConstants::DefaultChamberZ(2 * Station + 1);
274 // First and second Z to extrapolate at
275 if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;}
276 else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;}
278 AliError(Form("Starting Z (%f) in between z1 (%f) and z2 (%f) of station(0..)%d",this->fZ,z1,z2,Station));
279 // cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl;
280 // cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 <<
281 // ") and z2 (" << z2 << ") of station(0..) " << Station << endl;
285 // copy of track parameters
286 TrackParam[i1] = *this;
287 // first extrapolation
288 (&(TrackParam[i1]))->ExtrapToZ(extZ[0]);
289 TrackParam[i2] = TrackParam[i1];
290 // second extrapolation
291 (&(TrackParam[i2]))->ExtrapToZ(extZ[1]);
295 //__________________________________________________________________________
296 void AliMUONTrackParam::ExtrapToVertex(Double_t xVtx, Double_t yVtx, Double_t zVtx)
298 /// Extrapolation to the vertex.
299 /// Returns the track parameters resulting from the extrapolation in the current TrackParam.
300 /// Changes parameters according to Branson correction through the absorber
302 Double_t zAbsorber = -503.0; // to be coherent with the Geant absorber geometry !!!!
304 // Extrapolates track parameters upstream to the "Z" end of the front absorber
305 ExtrapToZ(zAbsorber); // !!!
306 // Makes Branson correction (multiple scattering + energy loss)
307 BransonCorrection(xVtx,yVtx,zVtx);
308 // Makes a simple magnetic field correction through the absorber
309 FieldCorrection(zAbsorber);
313 // Keep this version for future developments
314 //__________________________________________________________________________
315 // void AliMUONTrackParam::BransonCorrection()
317 // // Branson correction of track parameters
318 // // the entry parameters have to be calculated at the end of the absorber
319 // Double_t zEndAbsorber, zBP, xBP, yBP;
320 // Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
322 // // Would it be possible to calculate all that from Geant configuration ????
323 // // and to get the Branson parameters from a function in ABSO module ????
324 // // with an eventual contribution from other detectors like START ????
325 // // Radiation lengths outer part theta > 3 degres
326 // static Double_t x01[9] = { 18.8, // C (cm)
327 // 10.397, // Concrete (cm)
328 // 0.56, // Plomb (cm)
329 // 47.26, // Polyethylene (cm)
330 // 0.56, // Plomb (cm)
331 // 47.26, // Polyethylene (cm)
332 // 0.56, // Plomb (cm)
333 // 47.26, // Polyethylene (cm)
334 // 0.56 }; // Plomb (cm)
335 // // inner part theta < 3 degres
336 // static Double_t x02[3] = { 18.8, // C (cm)
337 // 10.397, // Concrete (cm)
339 // // z positions of the materials inside the absober outer part theta > 3 degres
340 // static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 };
341 // // inner part theta < 3 degres
342 // static Double_t z2[4] = { 90, 315, 467, 503 };
343 // static Bool_t first = kTRUE;
344 // static Double_t zBP1, zBP2, rLimit;
345 // // Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call)
348 // Double_t aNBP = 0.0;
349 // Double_t aDBP = 0.0;
352 // for (iBound = 0; iBound < 9; iBound++) {
354 // (z1[iBound+1] * z1[iBound+1] * z1[iBound+1] -
355 // z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound];
357 // (z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound];
359 // zBP1 = (2.0 * aNBP) / (3.0 * aDBP);
362 // for (iBound = 0; iBound < 3; iBound++) {
364 // (z2[iBound+1] * z2[iBound+1] * z2[iBound+1] -
365 // z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound];
367 // (z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound];
369 // zBP2 = (2.0 * aNBP) / (3.0 * aDBP);
370 // rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
373 // pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
375 // if (fInverseBendingMomentum < 0) sign = -1;
376 // pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope));
377 // pX = pZ * fNonBendingSlope;
378 // pY = pZ * fBendingSlope;
379 // pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX);
380 // xEndAbsorber = fNonBendingCoor;
381 // yEndAbsorber = fBendingCoor;
382 // radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
384 // if (radiusEndAbsorber2 > rLimit*rLimit) {
385 // zEndAbsorber = z1[9];
388 // zEndAbsorber = z2[3];
392 // xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
393 // yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
395 // // new parameters after Branson and energy loss corrections
396 // pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP);
397 // pX = pZ * xBP / zBP;
398 // pY = pZ * yBP / zBP;
399 // fBendingSlope = pY / pZ;
400 // fNonBendingSlope = pX / pZ;
402 // pT = TMath::Sqrt(pX * pX + pY * pY);
403 // theta = TMath::ATan2(pT, pZ);
405 // TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
407 // fInverseBendingMomentum = (sign / pTotal) *
409 // fBendingSlope * fBendingSlope +
410 // fNonBendingSlope * fNonBendingSlope) /
411 // TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
413 // // vertex position at (0,0,0)
414 // // should be taken from vertex measurement ???
415 // fBendingCoor = 0.0;
416 // fNonBendingCoor = 0;
420 void AliMUONTrackParam::BransonCorrection(Double_t xVtx,Double_t yVtx,Double_t zVtx)
422 /// Branson correction of track parameters
423 // the entry parameters have to be calculated at the end of the absorber
424 // simplified version: the z positions of Branson's planes are no longer calculated
425 // but are given as inputs. One can use the macros MUONTestAbso.C and DrawTestAbso.C
426 // to test this correction.
427 // Would it be possible to calculate all that from Geant configuration ????
428 // and to get the Branson parameters from a function in ABSO module ????
429 // with an eventual contribution from other detectors like START ????
430 // change to take into account the vertex postition (real, reconstruct,....)
432 Double_t zBP, xBP, yBP;
433 Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
435 static Bool_t first = kTRUE;
436 static Double_t zBP1, zBP2, rLimit, thetaLimit, zEndAbsorber;
437 // zBP1 for outer part and zBP2 for inner part (only at the first call)
441 zEndAbsorber = -503; // spectro (z<0)
442 thetaLimit = 3.0 * (TMath::Pi()) / 180.;
443 rLimit = TMath::Abs(zEndAbsorber) * TMath::Tan(thetaLimit);
444 zBP1 = -450; // values close to those calculated with EvalAbso.C
448 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
450 if (fInverseBendingMomentum < 0) sign = -1;
454 pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX);
455 xEndAbsorber = fNonBendingCoor;
456 yEndAbsorber = fBendingCoor;
457 radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
459 if (radiusEndAbsorber2 > rLimit*rLimit) {
465 xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
466 yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
468 // new parameters after Branson and energy loss corrections
469 // Float_t zSmear = zBP - gRandom->Gaus(0.,2.); // !!! possible smearing of Z vertex position
471 Float_t zSmear = zBP ;
473 pZ = pTotal * (zSmear-zVtx) / TMath::Sqrt((xBP-xVtx) * (xBP-xVtx) + (yBP-yVtx) * (yBP-yVtx) +( zSmear-zVtx) * (zSmear-zVtx) );
474 pX = pZ * (xBP - xVtx)/ (zSmear-zVtx);
475 pY = pZ * (yBP - yVtx) / (zSmear-zVtx);
476 fBendingSlope = pY / pZ;
477 fNonBendingSlope = pX / pZ;
480 pT = TMath::Sqrt(pX * pX + pY * pY);
481 theta = TMath::ATan2(pT, TMath::Abs(pZ));
482 pTotal = TotalMomentumEnergyLoss(thetaLimit, pTotal, theta);
484 fInverseBendingMomentum = (sign / pTotal) *
486 fBendingSlope * fBendingSlope +
487 fNonBendingSlope * fNonBendingSlope) /
488 TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
490 // vertex position at (0,0,0)
491 // should be taken from vertex measurement ???
494 fNonBendingCoor = yVtx;
499 //__________________________________________________________________________
500 Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t thetaLimit, Double_t pTotal, Double_t theta)
502 /// Returns the total momentum corrected from energy loss in the front absorber
503 // One can use the macros MUONTestAbso.C and DrawTestAbso.C
504 // to test this correction.
505 // Momentum energy loss behaviour evaluated with the simulation of single muons (april 2002)
506 Double_t deltaP, pTotalCorrected;
508 // Parametrization to be redone according to change of absorber material ????
509 // See remark in function BransonCorrection !!!!
510 // The name is not so good, and there are many arguments !!!!
511 if (theta < thetaLimit ) {
513 deltaP = 2.5938 + 0.0570 * pTotal - 0.001151 * pTotal * pTotal;
515 deltaP = 3.0714 + 0.011767 *pTotal;
517 deltaP *= 0.75; // AZ
520 deltaP = 2.1207 + 0.05478 * pTotal - 0.00145079 * pTotal * pTotal;
522 deltaP = 2.6069 + 0.0051705 * pTotal;
526 pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
527 return pTotalCorrected;
530 //__________________________________________________________________________
531 void AliMUONTrackParam::FieldCorrection(Double_t Z)
533 /// Correction of the effect of the magnetic field in the absorber
534 // Assume a constant field along Z axis.
537 Double_t pYZ,pX,pY,pZ,pT;
538 Double_t pXNew,pYNew;
541 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
542 c = TMath::Sign(1.0,fInverseBendingMomentum); // particle charge
547 pT = TMath::Sqrt(pX*pX+pY*pY);
549 if (TMath::Abs(pZ) <= 0) return;
551 x[0] = x[2]*fNonBendingSlope;
552 x[1] = x[2]*fBendingSlope;
554 // Take magn. field value at position x.
555 fkField->Field(x, b);
558 // Transverse momentum rotation
559 // Parameterized with the study of DeltaPhi = phiReco - phiGen as a function of pZ.
560 Double_t phiShift = c*0.436*0.0003*bZ*Z/pZ;
561 // Rotate momentum around Z axis.
562 pXNew = pX*TMath::Cos(phiShift) - pY*TMath::Sin(phiShift);
563 pYNew = pX*TMath::Sin(phiShift) + pY*TMath::Cos(phiShift);
565 fBendingSlope = pYNew / pZ;
566 fNonBendingSlope = pXNew / pZ;
568 fInverseBendingMomentum = c / TMath::Sqrt(pYNew*pYNew+pZ*pZ);
571 //__________________________________________________________________________
572 Double_t AliMUONTrackParam::Px() const
574 /// return px from track paramaters
575 Double_t pYZ, pZ, pX;
577 if ( TMath::Abs(fInverseBendingMomentum) > 0 )
578 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
579 pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0)
580 pX = pZ * fNonBendingSlope;
583 //__________________________________________________________________________
584 Double_t AliMUONTrackParam::Py() const
586 /// return px from track paramaters
587 Double_t pYZ, pZ, pY;
589 if ( TMath::Abs(fInverseBendingMomentum) > 0 )
590 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
591 pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0)
592 pY = pZ * fBendingSlope;
595 //__________________________________________________________________________
596 Double_t AliMUONTrackParam::Pz() const
598 /// return px from track paramaters
601 if ( TMath::Abs(fInverseBendingMomentum) > 0 )
602 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
603 pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0)
606 //__________________________________________________________________________
607 Double_t AliMUONTrackParam::P() const
609 /// return p from track paramaters
612 if ( TMath::Abs(fInverseBendingMomentum) > 0 )
613 pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
614 pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0)
616 TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope + fNonBendingSlope * fNonBendingSlope);
620 //__________________________________________________________________________
621 void AliMUONTrackParam::ExtrapOneStepHelix(Double_t charge, Double_t step,
622 Double_t *vect, Double_t *vout) const
624 /// ******************************************************************
626 /// * Performs the tracking of one step in a magnetic field *
627 /// * The trajectory is assumed to be a helix in a constant field *
628 /// * taken at the mid point of the step. *
631 /// * STEP =arc length of the step asked *
632 /// * VECT =input vector (position,direction cos and momentum) *
633 /// * CHARGE= electric charge of the particle *
635 /// * VOUT = same as VECT after completion of the step *
637 /// * ==>Called by : <USER>, GUSWIM *
638 /// * Author m.hansroul ********* *
639 /// * modified s.egli, s.v.levonian *
640 /// * modified v.perevoztchikov
642 /// ******************************************************************
644 // modif: everything in double precision
646 Double_t xyz[3], h[4], hxp[3];
647 Double_t h2xy, hp, rho, tet;
648 Double_t sint, sintt, tsint, cos1t;
649 Double_t f1, f2, f3, f4, f5, f6;
654 const Int_t kipx = 3;
655 const Int_t kipy = 4;
656 const Int_t kipz = 5;
657 const Int_t kipp = 6;
659 const Double_t kec = 2.9979251e-4;
661 // ------------------------------------------------------------------
663 // units are kgauss,centimeters,gev/c
665 vout[kipp] = vect[kipp];
666 if (TMath::Abs(charge) < 0.00001) {
667 for (Int_t i = 0; i < 3; i++) {
668 vout[i] = vect[i] + step * vect[i+3];
669 vout[i+3] = vect[i+3];
673 xyz[0] = vect[kix] + 0.5 * step * vect[kipx];
674 xyz[1] = vect[kiy] + 0.5 * step * vect[kipy];
675 xyz[2] = vect[kiz] + 0.5 * step * vect[kipz];
677 //cmodif: call gufld (xyz, h) changed into:
680 h2xy = h[0]*h[0] + h[1]*h[1];
681 h[3] = h[2]*h[2]+ h2xy;
683 for (Int_t i = 0; i < 3; i++) {
684 vout[i] = vect[i] + step * vect[i+3];
685 vout[i+3] = vect[i+3];
689 if (h2xy < 1.e-12*h[3]) {
690 ExtrapOneStepHelix3(charge*h[2], step, vect, vout);
693 h[3] = TMath::Sqrt(h[3]);
699 hxp[0] = h[1]*vect[kipz] - h[2]*vect[kipy];
700 hxp[1] = h[2]*vect[kipx] - h[0]*vect[kipz];
701 hxp[2] = h[0]*vect[kipy] - h[1]*vect[kipx];
703 hp = h[0]*vect[kipx] + h[1]*vect[kipy] + h[2]*vect[kipz];
705 rho = -charge*h[3]/vect[kipp];
708 if (TMath::Abs(tet) > 0.15) {
709 sint = TMath::Sin(tet);
711 tsint = (tet-sint)/tet;
712 cos1t = 2.*(TMath::Sin(0.5*tet))*(TMath::Sin(0.5*tet))/tet;
715 sintt = (1. - tsint);
722 f3 = step * tsint * hp;
725 f6 = tet * cos1t * hp;
727 vout[kix] = vect[kix] + f1*vect[kipx] + f2*hxp[0] + f3*h[0];
728 vout[kiy] = vect[kiy] + f1*vect[kipy] + f2*hxp[1] + f3*h[1];
729 vout[kiz] = vect[kiz] + f1*vect[kipz] + f2*hxp[2] + f3*h[2];
731 vout[kipx] = vect[kipx] + f4*vect[kipx] + f5*hxp[0] + f6*h[0];
732 vout[kipy] = vect[kipy] + f4*vect[kipy] + f5*hxp[1] + f6*h[1];
733 vout[kipz] = vect[kipz] + f4*vect[kipz] + f5*hxp[2] + f6*h[2];
738 //__________________________________________________________________________
739 void AliMUONTrackParam::ExtrapOneStepHelix3(Double_t field, Double_t step,
740 Double_t *vect, Double_t *vout) const
742 /// ******************************************************************
744 /// * Tracking routine in a constant field oriented *
746 /// * Tracking is performed with a conventional *
747 /// * helix step method *
749 /// * ==>Called by : <USER>, GUSWIM *
750 /// * Authors R.Brun, M.Hansroul ********* *
751 /// * Rewritten V.Perevoztchikov
753 /// ******************************************************************
756 Double_t h4, hp, rho, tet;
757 Double_t sint, sintt, tsint, cos1t;
758 Double_t f1, f2, f3, f4, f5, f6;
763 const Int_t kipx = 3;
764 const Int_t kipy = 4;
765 const Int_t kipz = 5;
766 const Int_t kipp = 6;
768 const Double_t kec = 2.9979251e-4;
771 // ------------------------------------------------------------------
773 // units are kgauss,centimeters,gev/c
775 vout[kipp] = vect[kipp];
778 hxp[0] = - vect[kipy];
779 hxp[1] = + vect[kipx];
783 rho = -h4/vect[kipp];
785 if (TMath::Abs(tet) > 0.15) {
786 sint = TMath::Sin(tet);
788 tsint = (tet-sint)/tet;
789 cos1t = 2.* TMath::Sin(0.5*tet) * TMath::Sin(0.5*tet)/tet;
792 sintt = (1. - tsint);
799 f3 = step * tsint * hp;
802 f6 = tet * cos1t * hp;
804 vout[kix] = vect[kix] + f1*vect[kipx] + f2*hxp[0];
805 vout[kiy] = vect[kiy] + f1*vect[kipy] + f2*hxp[1];
806 vout[kiz] = vect[kiz] + f1*vect[kipz] + f3;
808 vout[kipx] = vect[kipx] + f4*vect[kipx] + f5*hxp[0];
809 vout[kipy] = vect[kipy] + f4*vect[kipy] + f5*hxp[1];
810 vout[kipz] = vect[kipz] + f4*vect[kipz] + f6;
814 //__________________________________________________________________________
815 void AliMUONTrackParam::ExtrapOneStepRungekutta(Double_t charge, Double_t step,
816 Double_t* vect, Double_t* vout) const
818 /// ******************************************************************
820 /// * Runge-Kutta method for tracking a particle through a magnetic *
821 /// * field. Uses Nystroem algorithm (See Handbook Nat. Bur. of *
822 /// * Standards, procedure 25.5.20) *
824 /// * Input parameters *
825 /// * CHARGE Particle charge *
826 /// * STEP Step size *
827 /// * VECT Initial co-ords,direction cosines,momentum *
828 /// * Output parameters *
829 /// * VOUT Output co-ords,direction cosines,momentum *
830 /// * User routine called *
831 /// * CALL GUFLD(X,F) *
833 /// * ==>Called by : <USER>, GUSWIM *
834 /// * Authors R.Brun, M.Hansroul ********* *
835 /// * V.Perevoztchikov (CUT STEP implementation) *
838 /// ******************************************************************
840 Double_t h2, h4, f[4];
841 Double_t xyzt[3], a, b, c, ph,ph2;
842 Double_t secxs[4],secys[4],seczs[4],hxp[3];
843 Double_t g1, g2, g3, g4, g5, g6, ang2, dxt, dyt, dzt;
844 Double_t est, at, bt, ct, cba;
845 Double_t f1, f2, f3, f4, rho, tet, hnorm, hp, rho1, sint, cost;
855 Double_t maxit = 1992;
856 Double_t maxcut = 11;
858 const Double_t kdlt = 1e-4;
859 const Double_t kdlt32 = kdlt/32.;
860 const Double_t kthird = 1./3.;
861 const Double_t khalf = 0.5;
862 const Double_t kec = 2.9979251e-4;
864 const Double_t kpisqua = 9.86960440109;
868 const Int_t kipx = 3;
869 const Int_t kipy = 4;
870 const Int_t kipz = 5;
873 // *. ------------------------------------------------------------------
875 // * this constant is for units cm,gev/c and kgauss
879 for(Int_t j = 0; j < 7; j++)
882 Double_t pinv = kec * charge / vect[6];
890 if (TMath::Abs(h) > TMath::Abs(rest)) h = rest;
891 //cmodif: call gufld(vout,f) changed into:
896 // * start of integration
909 secxs[0] = (b * f[2] - c * f[1]) * ph2;
910 secys[0] = (c * f[0] - a * f[2]) * ph2;
911 seczs[0] = (a * f[1] - b * f[0]) * ph2;
912 ang2 = (secxs[0]*secxs[0] + secys[0]*secys[0] + seczs[0]*seczs[0]);
913 if (ang2 > kpisqua) break;
915 dxt = h2 * a + h4 * secxs[0];
916 dyt = h2 * b + h4 * secys[0];
917 dzt = h2 * c + h4 * seczs[0];
922 // * second intermediate point
925 est = TMath::Abs(dxt) + TMath::Abs(dyt) + TMath::Abs(dzt);
927 if (ncut++ > maxcut) break;
936 //cmodif: call gufld(xyzt,f) changed into:
943 secxs[1] = (bt * f[2] - ct * f[1]) * ph2;
944 secys[1] = (ct * f[0] - at * f[2]) * ph2;
945 seczs[1] = (at * f[1] - bt * f[0]) * ph2;
949 secxs[2] = (bt * f[2] - ct * f[1]) * ph2;
950 secys[2] = (ct * f[0] - at * f[2]) * ph2;
951 seczs[2] = (at * f[1] - bt * f[0]) * ph2;
952 dxt = h * (a + secxs[2]);
953 dyt = h * (b + secys[2]);
954 dzt = h * (c + seczs[2]);
958 at = a + 2.*secxs[2];
959 bt = b + 2.*secys[2];
960 ct = c + 2.*seczs[2];
962 est = TMath::Abs(dxt)+TMath::Abs(dyt)+TMath::Abs(dzt);
963 if (est > 2.*TMath::Abs(h)) {
964 if (ncut++ > maxcut) break;
973 //cmodif: call gufld(xyzt,f) changed into:
976 z = z + (c + (seczs[0] + seczs[1] + seczs[2]) * kthird) * h;
977 y = y + (b + (secys[0] + secys[1] + secys[2]) * kthird) * h;
978 x = x + (a + (secxs[0] + secxs[1] + secxs[2]) * kthird) * h;
980 secxs[3] = (bt*f[2] - ct*f[1])* ph2;
981 secys[3] = (ct*f[0] - at*f[2])* ph2;
982 seczs[3] = (at*f[1] - bt*f[0])* ph2;
983 a = a+(secxs[0]+secxs[3]+2. * (secxs[1]+secxs[2])) * kthird;
984 b = b+(secys[0]+secys[3]+2. * (secys[1]+secys[2])) * kthird;
985 c = c+(seczs[0]+seczs[3]+2. * (seczs[1]+seczs[2])) * kthird;
987 est = TMath::Abs(secxs[0]+secxs[3] - (secxs[1]+secxs[2]))
988 + TMath::Abs(secys[0]+secys[3] - (secys[1]+secys[2]))
989 + TMath::Abs(seczs[0]+seczs[3] - (seczs[1]+seczs[2]));
991 if (est > kdlt && TMath::Abs(h) > 1.e-4) {
992 if (ncut++ > maxcut) break;
998 // * if too many iterations, go to helix
999 if (iter++ > maxit) break;
1004 cba = 1./ TMath::Sqrt(a*a + b*b + c*c);
1012 if (step < 0.) rest = -rest;
1013 if (rest < 1.e-5*TMath::Abs(step)) return;
1017 // angle too big, use helix
1022 f4 = TMath::Sqrt(f1*f1+f2*f2+f3*f3);
1031 hxp[0] = f2*vect[kipz] - f3*vect[kipy];
1032 hxp[1] = f3*vect[kipx] - f1*vect[kipz];
1033 hxp[2] = f1*vect[kipy] - f2*vect[kipx];
1035 hp = f1*vect[kipx] + f2*vect[kipy] + f3*vect[kipz];
1038 sint = TMath::Sin(tet);
1039 cost = 2.*TMath::Sin(khalf*tet)*TMath::Sin(khalf*tet);
1043 g3 = (tet-sint) * hp*rho1;
1048 vout[kix] = vect[kix] + g1*vect[kipx] + g2*hxp[0] + g3*f1;
1049 vout[kiy] = vect[kiy] + g1*vect[kipy] + g2*hxp[1] + g3*f2;
1050 vout[kiz] = vect[kiz] + g1*vect[kipz] + g2*hxp[2] + g3*f3;
1052 vout[kipx] = vect[kipx] + g4*vect[kipx] + g5*hxp[0] + g6*f1;
1053 vout[kipy] = vect[kipy] + g4*vect[kipy] + g5*hxp[1] + g6*f2;
1054 vout[kipz] = vect[kipz] + g4*vect[kipz] + g5*hxp[2] + g6*f3;
1058 //___________________________________________________________
1059 void AliMUONTrackParam::GetField(Double_t *Position, Double_t *Field) const
1061 /// interface for arguments in double precision (Why ? ChF)
1064 x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2];
1066 fkField->Field(x, b);
1067 Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2];
1071 //_____________________________________________-
1072 void AliMUONTrackParam::Print(Option_t* opt) const
1074 /// Printing TrackParam information
1075 /// "full" option for printing all the information about the TrackParam
1079 if ( sopt.Contains("FULL") ) {
1080 cout << "<AliMUONTrackParam> Bending P=" << setw(5) << setprecision(3) << 1./GetInverseBendingMomentum() <<
1081 ", NonBendSlope=" << setw(5) << setprecision(3) << GetNonBendingSlope()*180./TMath::Pi() <<
1082 ", BendSlope=" << setw(5) << setprecision(3) << GetBendingSlope()*180./TMath::Pi() <<
1083 ", (x,y,z)_IP=(" << setw(5) << setprecision(3) << GetNonBendingCoor() <<
1084 "," << setw(5) << setprecision(3) << GetBendingCoor() <<
1085 "," << setw(5) << setprecision(3) << GetZ() <<
1086 ") cm, (px,py,pz)=(" << setw(5) << setprecision(3) << Px() <<
1087 "," << setw(5) << setprecision(3) << Py() <<
1088 "," << setw(5) << setprecision(3) << Pz() << ") GeV/c" << endl;
1091 cout << "<AliMUONTrackParam>" << endl;