[u/mrichter/AliRoot.git] / MUON / AliMUONTrackParam.cxx

/**************************************************************************
 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

/*
$Log$
Revision 1.4  2000/07/03 07:53:31  morsch
Double declaration problem on HP solved.

Revision 1.3  2000/06/30 10:15:48  gosset
Changes to EventReconstructor...:
precision fit with multiple Coulomb scattering;
extrapolation to vertex with Branson correction in absorber (JPC)

Revision 1.2  2000/06/15 07:58:49  morsch
Code from MUON-dev joined

Revision 1.1.2.3  2000/06/09 21:03:09  morsch
Make includes consistent with new file structure.

Revision 1.1.2.2  2000/06/09 12:58:05  gosset
Removed comment beginnings in Log sections of .cxx files
Suppressed most violations of coding rules

Revision 1.1.2.1  2000/06/07 14:44:53  gosset
Addition of files for track reconstruction in C++
*/

//__________________________________________________________________________
//
// Track parameters in ALICE dimuon spectrometer
//__________________________________________________________________________

#include <iostream.h>

#include "AliCallf77.h" 
#include "AliMUON.h" 
#include "AliMUONHitForRec.h" 
#include "AliMUONSegment.h" 
#include "AliMUONTrackParam.h" 
#include "AliMUONChamber.h" 
#include "AliRun.h" 

ClassImp(AliMUONTrackParam) // Class implementation in ROOT context

#ifndef WIN32 
# define reco_ghelix reco_ghelix_
#else 
# define reco_ghelix RECO_GHELIX
#endif 

extern "C"
{
void type_of_call reco_ghelix(Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New);
}

// Inline functions for Get and Set: inline removed because it does not work !!!!
Double_t AliMUONTrackParam::GetInverseBendingMomentum(void) {
  // Get fInverseBendingMomentum
  return fInverseBendingMomentum;}
void AliMUONTrackParam::SetInverseBendingMomentum(Double_t InverseBendingMomentum) {
  // Set fInverseBendingMomentum
  fInverseBendingMomentum = InverseBendingMomentum;}
Double_t AliMUONTrackParam::GetBendingSlope(void) {
  // Get fBendingSlope
  return fBendingSlope;}
void AliMUONTrackParam::SetBendingSlope(Double_t BendingSlope) {
  // Set fBendingSlope
  fBendingSlope = BendingSlope;}
Double_t AliMUONTrackParam::GetNonBendingSlope(void) {
  // Get fNonBendingSlope
  return fNonBendingSlope;}
void AliMUONTrackParam::SetNonBendingSlope(Double_t NonBendingSlope) {
  // Set fNonBendingSlope
  fNonBendingSlope = NonBendingSlope;}
Double_t AliMUONTrackParam::GetZ(void) {
  // Get fZ
  return fZ;}
void AliMUONTrackParam::SetZ(Double_t Z) {
  // Set fZ
  fZ = Z;}
Double_t AliMUONTrackParam::GetBendingCoor(void) {
  // Get fBendingCoor
  return fBendingCoor;}
void AliMUONTrackParam::SetBendingCoor(Double_t BendingCoor) {
  // Set fBendingCoor
  fBendingCoor = BendingCoor;}
Double_t AliMUONTrackParam::GetNonBendingCoor(void) {
  // Get fNonBendingCoor
  return fNonBendingCoor;}
void AliMUONTrackParam::SetNonBendingCoor(Double_t NonBendingCoor) {
  // Set fNonBendingCoor
  fNonBendingCoor = NonBendingCoor;}

  //__________________________________________________________________________
void AliMUONTrackParam::ExtrapToZ(Double_t Z)
{
  // Track parameter extrapolation to the plane at "Z".
  // On return, the track parameters resulting from the extrapolation
  // replace the current track parameters.
  // Use "reco_ghelix" which should be replaced by something else !!!!
  if (this->fZ == Z) return; // nothing to be done if same Z
  Double_t forwardBackward; // +1 if forward, -1 if backward
  if (Z > this->fZ) forwardBackward = 1.0;
  else forwardBackward = -1.0;
  Double_t temp, vGeant3[7], vGeant3New[7]; // 7 in parameter ????
  Int_t iGeant3, stepNumber;
  Int_t maxStepNumber = 5000; // in parameter ????
  // For safety: return kTRUE or kFALSE ????
  // Parameter vector for calling GHELIX in Geant3
  SetGeant3Parameters(vGeant3, forwardBackward);
  // For use of reco_ghelix...: invert X and Y, PX/PTOT and PY/PTOT !!!!
  temp = vGeant3[0]; vGeant3[0] = vGeant3[1]; vGeant3[1] = temp;
  temp = vGeant3[3]; vGeant3[3] = vGeant3[4]; vGeant3[4] = temp;
  // sign of charge (sign of fInverseBendingMomentum if forward motion)
  // must be also changed if backward extrapolation
  Double_t chargeExtrap = forwardBackward *
    TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum);
  Double_t stepLength = 6.0; // in parameter ????
  // Extrapolation loop
  stepNumber = 0;
  while (((forwardBackward * (vGeant3[2] - Z)) <= 0.0) &&
	 (stepNumber < maxStepNumber)) {
    stepNumber++;
    // call Geant3 "ghelix" subroutine through a copy in "reco_muon.F":
    // the true function should be called, but how ???? and remove prototyping ...
    reco_ghelix(chargeExtrap, stepLength, vGeant3, vGeant3New);
    if ((forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z
    // better use TArray ????
    for (iGeant3 = 0; iGeant3 < 7; iGeant3++)
      {vGeant3[iGeant3] = vGeant3New[iGeant3];}
  }
  // check maxStepNumber ????
  // For use of reco_ghelix...:
  // invert back X and Y, PX/PTOT and PY/PTOT, both for vGeant3 and vGeant3New !!!!
  temp = vGeant3[0]; vGeant3[0] = vGeant3[1]; vGeant3[1] = temp;
  temp = vGeant3New[0]; vGeant3New[0] = vGeant3New[1]; vGeant3New[1] = temp;
  temp = vGeant3[3]; vGeant3[3] = vGeant3[4]; vGeant3[4] = temp;
  temp = vGeant3New[3]; vGeant3New[3] = vGeant3New[4]; vGeant3New[4] = temp;
  // Interpolation back to exact Z (2nd order)
  // should be in function ???? using TArray ????
  Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2
  Double_t dZ1i = Z - vGeant3[2]; // 1-i
  Double_t dZi2 = vGeant3New[2] - Z; // i->2
  Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12;
  Double_t xSecond =
    ((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12;
  Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12;
  Double_t ySecond =
    ((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12;
  vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X
  vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y
  vGeant3[2] = Z; // Z
  Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i);
  Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i);
  // (PX, PY, PZ)/PTOT assuming forward motion
  vGeant3[5] =
    1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT
  vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT
  vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT
  // Track parameters from Geant3 parameters,
  // with charge back for forward motion
  GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward);
}

  //__________________________________________________________________________
void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward)
{
  // Set vector of Geant3 parameters pointed to by "VGeant3"
  // from track parameters in current AliMUONTrackParam.
  // Since AliMUONTrackParam is only geometry, one uses "ForwardBackward"
  // to know whether the particle is going forward (+1) or backward (-1).
  VGeant3[0] = this->fNonBendingCoor; // X
  VGeant3[1] = this->fBendingCoor; // Y
  VGeant3[2] = this->fZ; // Z
  Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum);
  Double_t pZ =
    pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope);
  VGeant3[6] =
    TMath::Sqrt(pYZ * pYZ +
		pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT
  VGeant3[5] = ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT
  VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT
  VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT
}

  //__________________________________________________________________________
void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge)
{
  // Get track parameters in current AliMUONTrackParam
  // from Geant3 parameters pointed to by "VGeant3",
  // assumed to be calculated for forward motion in Z.
  // "InverseBendingMomentum" is signed with "Charge".
  this->fNonBendingCoor = VGeant3[0]; // X
  this->fBendingCoor = VGeant3[1]; // Y
  this->fZ = VGeant3[2]; // Z
  Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]);
  this->fInverseBendingMomentum = Charge / pYZ;
  this->fBendingSlope = VGeant3[4] / VGeant3[5];
  this->fNonBendingSlope = VGeant3[3] / VGeant3[5];
}

  //__________________________________________________________________________
void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam)
{
  // Track parameters extrapolated from current track parameters ("this")
  // to both chambers of the station(0..) "Station"
  // are returned in the array (dimension 2) of track parameters
  // pointed to by "TrackParam" (index 0 and 1 for first and second chambers).
  Double_t extZ[2], z1, z2;
  Int_t i1, i2;
  AliMUON *pMUON = (AliMUON*) gAlice->GetModule("MUON"); // necessary ????
  // range of Station to be checked ????
  z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber
  z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber
  // First and second Z to extrapolate at
  if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;}
  else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;}
  else {
    cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl;
    cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 <<
      ") and z2 (" << z2 << ") of station(0..) " << Station << endl;
  }
  extZ[i1] = z1;
  extZ[i2] = z2;
  // copy of track parameters
  TrackParam[i1] = *this;
  // first extrapolation
  (&(TrackParam[i1]))->ExtrapToZ(extZ[0]);
  TrackParam[i2] = TrackParam[i1];
  // second extrapolation
  (&(TrackParam[i2]))->ExtrapToZ(extZ[1]);
  return;
}

  //__________________________________________________________________________
void AliMUONTrackParam::ExtrapToVertex()
{
  // Extrapolation to the vertex.
  // Returns the track parameters resulting from the extrapolation,
  // in the current TrackParam.
  // Changes parameters according to Branson correction through the absorber 
  
  Double_t zAbsorber = 503.0; // to be coherent with the Geant absorber geometry !!!!
  // Extrapolates track parameters upstream to the "Z" end of the front absorber
  ExtrapToZ(zAbsorber);
    // Makes Branson correction (multiple scattering + energy loss)
  BransonCorrection();
}

  //__________________________________________________________________________
void AliMUONTrackParam::BransonCorrection()
{
  // Branson correction of track parameters
  // the entry parameters have to be calculated at the end of the absorber
  Double_t zEndAbsorber, zBP, xBP, yBP;
  Double_t  pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
  Int_t sign;
  // Would it be possible to calculate all that from Geant configuration ????
  // and to get the Branson parameters from a function in ABSO module ????
  // with an eventual contribution from other detectors like START ????
  // Radiation lengths outer part theta > 3 degres
  static Double_t x01[9] = { 18.8,    // C (cm)
			     10.397,   // Concrete (cm)
			     0.56,    // Plomb (cm)
			     47.26,   // Polyethylene (cm)
			     0.56,   // Plomb (cm)
			     47.26,   // Polyethylene (cm)
			     0.56,   // Plomb (cm)
			     47.26,   // Polyethylene (cm)
			     0.56 };   // Plomb (cm)
  // inner part theta < 3 degres
  static Double_t x02[3] = { 18.8,    // C (cm)
			     10.397,   // Concrete (cm)
			     0.35 };    // W (cm) 
  // z positions of the materials inside the absober outer part theta > 3 degres
  static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 };
  // inner part theta < 3 degres
  static Double_t z2[4] = { 90, 315, 467, 503 };
  static Bool_t first = kTRUE;
  static Double_t zBP1, zBP2, rLimit;
  // Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call)
  if (first) {
    first = kFALSE;
    Double_t aNBP = 0.0;
    Double_t aDBP = 0.0;
    Int_t iBound;
    
    for (iBound = 0; iBound < 9; iBound++) {
      aNBP = aNBP +
	(z1[iBound+1] * z1[iBound+1] * z1[iBound+1] -
	 z1[iBound]   * z1[iBound]   * z1[iBound]    ) / x01[iBound];
      aDBP = aDBP +
	(z1[iBound+1] * z1[iBound+1] - z1[iBound]   * z1[iBound]    ) / x01[iBound];
    }
    zBP1 = (2.0 * aNBP) / (3.0 * aDBP);
    aNBP = 0.0;
    aDBP = 0.0;
    for (iBound = 0; iBound < 3; iBound++) {
      aNBP = aNBP +
	(z2[iBound+1] * z2[iBound+1] * z2[iBound+1] -
	 z2[iBound]   * z2[iBound ]  * z2[iBound]    ) / x02[iBound];
      aDBP = aDBP +
	(z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound];
    }
    zBP2 = (2.0 * aNBP) / (3.0 * aDBP);
    rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
  }

  pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
  sign = 1;      
  if (fInverseBendingMomentum < 0) sign = -1;     
  pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); 
  pX = pZ * fNonBendingSlope; 
  pY = pZ * fBendingSlope; 
  pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX);
  xEndAbsorber = fNonBendingCoor; 
  yEndAbsorber = fBendingCoor; 
  radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;

  if (radiusEndAbsorber2 > rLimit*rLimit) {
    zEndAbsorber = z1[9];
    zBP = zBP1;
  } else {
    zEndAbsorber = z2[3];
    zBP = zBP2;
  }

  xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
  yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);

  // new parameters after Branson and energy loss corrections
  pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP);
  pX = pZ * xBP / zBP;
  pY = pZ * yBP / zBP;
  fBendingSlope = pY / pZ;
  fNonBendingSlope = pX / pZ;
  
  pT = TMath::Sqrt(pX * pX + pY * pY);      
  theta = TMath::ATan2(pT, pZ); 
  pTotal =
    TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);

  fInverseBendingMomentum = (sign / pTotal) *
    TMath::Sqrt(1.0 +
		fBendingSlope * fBendingSlope +
		fNonBendingSlope * fNonBendingSlope) /
    TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);

  // vertex position at (0,0,0)
  // should be taken from vertex measurement ???
  fBendingCoor = 0.0;
  fNonBendingCoor = 0;
  fZ= 0;
}

  //__________________________________________________________________________
Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t rLimit, Double_t pTotal, Double_t theta, Double_t xEndAbsorber, Double_t yEndAbsorber)
{
  // Returns the total momentum corrected from energy loss in the front absorber
  Double_t deltaP, pTotalCorrected;

  Double_t radiusEndAbsorber2 =
    xEndAbsorber *xEndAbsorber + yEndAbsorber * yEndAbsorber;
  // Parametrization to be redone according to change of absorber material ????
  // See remark in function BransonCorrection !!!!
  // The name is not so good, and there are many arguments !!!!
  if (radiusEndAbsorber2 < rLimit * rLimit) {
    if (pTotal < 15) {
      deltaP = 2.737 + 0.0494 * pTotal - 0.001123 * pTotal * pTotal;
    } else {
      deltaP = 3.0643 + 0.01346 *pTotal;
    }
  } else {
    if (pTotal < 15) {
      deltaP  = 2.1380 + 0.0351 * pTotal - 0.000853 * pTotal * pTotal;
    } else { 
      deltaP = 2.407 + 0.00702 * pTotal;
    }
  }
  pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
  return pTotalCorrected;
}
Commit	Line	Data
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	$Log$
956019b6	18	Revision 1.4 2000/07/03 07:53:31 morsch
	19	Double declaration problem on HP solved.
	20
88962f0c	21	Revision 1.3 2000/06/30 10:15:48 gosset
	22	Changes to EventReconstructor...:
	23	precision fit with multiple Coulomb scattering;
	24	extrapolation to vertex with Branson correction in absorber (JPC)
	25
04b5ea16	26	Revision 1.2 2000/06/15 07:58:49 morsch
	27	Code from MUON-dev joined
	28
a9e2aefa	29	Revision 1.1.2.3 2000/06/09 21:03:09 morsch
	30	Make includes consistent with new file structure.
	31
	32	Revision 1.1.2.2 2000/06/09 12:58:05 gosset
	33	Removed comment beginnings in Log sections of .cxx files
	34	Suppressed most violations of coding rules
	35
	36	Revision 1.1.2.1 2000/06/07 14:44:53 gosset
	37	Addition of files for track reconstruction in C++
	38	*/
	39
	40	//__________________________________________________________________________
	41	//
	42	// Track parameters in ALICE dimuon spectrometer
	43	//__________________________________________________________________________
	44
	45	#include <iostream.h>
	46
	47	#include "AliCallf77.h"
	48	#include "AliMUON.h"
	49	#include "AliMUONHitForRec.h"
	50	#include "AliMUONSegment.h"
	51	#include "AliMUONTrackParam.h"
	52	#include "AliMUONChamber.h"
	53	#include "AliRun.h"
	54
	55	ClassImp(AliMUONTrackParam) // Class implementation in ROOT context
	56
	57	#ifndef WIN32
	58	# define reco_ghelix reco_ghelix_
	59	#else
	60	# define reco_ghelix RECO_GHELIX
	61	#endif
	62
	63	extern "C"
	64	{
	65	void type_of_call reco_ghelix(Double_t &Charge, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	66	}
	67
	68	// Inline functions for Get and Set: inline removed because it does not work !!!!
	69	Double_t AliMUONTrackParam::GetInverseBendingMomentum(void) {
	70	// Get fInverseBendingMomentum
	71	return fInverseBendingMomentum;}
	72	void AliMUONTrackParam::SetInverseBendingMomentum(Double_t InverseBendingMomentum) {
	73	// Set fInverseBendingMomentum
	74	fInverseBendingMomentum = InverseBendingMomentum;}
	75	Double_t AliMUONTrackParam::GetBendingSlope(void) {
	76	// Get fBendingSlope
	77	return fBendingSlope;}
	78	void AliMUONTrackParam::SetBendingSlope(Double_t BendingSlope) {
	79	// Set fBendingSlope
	80	fBendingSlope = BendingSlope;}
	81	Double_t AliMUONTrackParam::GetNonBendingSlope(void) {
	82	// Get fNonBendingSlope
	83	return fNonBendingSlope;}
	84	void AliMUONTrackParam::SetNonBendingSlope(Double_t NonBendingSlope) {
	85	// Set fNonBendingSlope
	86	fNonBendingSlope = NonBendingSlope;}
	87	Double_t AliMUONTrackParam::GetZ(void) {
	88	// Get fZ
	89	return fZ;}
	90	void AliMUONTrackParam::SetZ(Double_t Z) {
	91	// Set fZ
	92	fZ = Z;}
93	Double_t AliMUONTrackParam::GetBendingCoor(void) {
94	// Get fBendingCoor
95	return fBendingCoor;}
96	void AliMUONTrackParam::SetBendingCoor(Double_t BendingCoor) {
97	// Set fBendingCoor
98	fBendingCoor = BendingCoor;}
99	Double_t AliMUONTrackParam::GetNonBendingCoor(void) {
100	// Get fNonBendingCoor
101	return fNonBendingCoor;}
102	void AliMUONTrackParam::SetNonBendingCoor(Double_t NonBendingCoor) {
103	// Set fNonBendingCoor
104	fNonBendingCoor = NonBendingCoor;}
105
106	//__________________________________________________________________________
107	void AliMUONTrackParam::ExtrapToZ(Double_t Z)
108	{
109	// Track parameter extrapolation to the plane at "Z".
110	// On return, the track parameters resulting from the extrapolation
111	// replace the current track parameters.
112	// Use "reco_ghelix" which should be replaced by something else !!!!
113	if (this->fZ == Z) return; // nothing to be done if same Z
114	Double_t forwardBackward; // +1 if forward, -1 if backward
115	if (Z > this->fZ) forwardBackward = 1.0;
116	else forwardBackward = -1.0;
117	Double_t temp, vGeant3[7], vGeant3New[7]; // 7 in parameter ????
118	Int_t iGeant3, stepNumber;
119	Int_t maxStepNumber = 5000; // in parameter ????
120	// For safety: return kTRUE or kFALSE ????
121	// Parameter vector for calling GHELIX in Geant3
122	SetGeant3Parameters(vGeant3, forwardBackward);
123	// For use of reco_ghelix...: invert X and Y, PX/PTOT and PY/PTOT !!!!
124	temp = vGeant3[0]; vGeant3[0] = vGeant3[1]; vGeant3[1] = temp;
125	temp = vGeant3[3]; vGeant3[3] = vGeant3[4]; vGeant3[4] = temp;
956019b6	126	// sign of charge (sign of fInverseBendingMomentum if forward motion)
	127	// must be also changed if backward extrapolation
	128	Double_t chargeExtrap = forwardBackward *
	129	TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum);
a9e2aefa	130	Double_t stepLength = 6.0; // in parameter ????
	131	// Extrapolation loop
	132	stepNumber = 0;
	133	while (((forwardBackward * (vGeant3[2] - Z)) <= 0.0) &&
	134	(stepNumber < maxStepNumber)) {
	135	stepNumber++;
	136	// call Geant3 "ghelix" subroutine through a copy in "reco_muon.F":
	137	// the true function should be called, but how ???? and remove prototyping ...
956019b6	138	reco_ghelix(chargeExtrap, stepLength, vGeant3, vGeant3New);
a9e2aefa	139	if ((forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z
	140	// better use TArray ????
	141	for (iGeant3 = 0; iGeant3 < 7; iGeant3++)
	142	{vGeant3[iGeant3] = vGeant3New[iGeant3];}
	143	}
	144	// check maxStepNumber ????
	145	// For use of reco_ghelix...:
	146	// invert back X and Y, PX/PTOT and PY/PTOT, both for vGeant3 and vGeant3New !!!!
	147	temp = vGeant3[0]; vGeant3[0] = vGeant3[1]; vGeant3[1] = temp;
	148	temp = vGeant3New[0]; vGeant3New[0] = vGeant3New[1]; vGeant3New[1] = temp;
	149	temp = vGeant3[3]; vGeant3[3] = vGeant3[4]; vGeant3[4] = temp;
	150	temp = vGeant3New[3]; vGeant3New[3] = vGeant3New[4]; vGeant3New[4] = temp;
	151	// Interpolation back to exact Z (2nd order)
	152	// should be in function ???? using TArray ????
	153	Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2
	154	Double_t dZ1i = Z - vGeant3[2]; // 1-i
	155	Double_t dZi2 = vGeant3New[2] - Z; // i->2
	156	Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12;
	157	Double_t xSecond =
	158	((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12;
	159	Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12;
	160	Double_t ySecond =
	161	((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12;
	162	vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X
	163	vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y
	164	vGeant3[2] = Z; // Z
	165	Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i);
	166	Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i);
956019b6	167	// (PX, PY, PZ)/PTOT assuming forward motion
a9e2aefa	168	vGeant3[5] =
	169	1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT
	170	vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT
	171	vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT
956019b6	172	// Track parameters from Geant3 parameters,
	173	// with charge back for forward motion
	174	GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward);
a9e2aefa	175	}
	176
	177	//__________________________________________________________________________
	178	void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward)
	179	{
	180	// Set vector of Geant3 parameters pointed to by "VGeant3"
	181	// from track parameters in current AliMUONTrackParam.
	182	// Since AliMUONTrackParam is only geometry, one uses "ForwardBackward"
	183	// to know whether the particle is going forward (+1) or backward (-1).
	184	VGeant3[0] = this->fNonBendingCoor; // X
	185	VGeant3[1] = this->fBendingCoor; // Y
	186	VGeant3[2] = this->fZ; // Z
	187	Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum);
	188	Double_t pZ =
	189	pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope);
	190	VGeant3[6] =
	191	TMath::Sqrt(pYZ * pYZ +
	192	pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT
	193	VGeant3[5] = ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT
	194	VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT
	195	VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT
	196	}
	197
	198	//__________________________________________________________________________
	199	void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge)
	200	{
	201	// Get track parameters in current AliMUONTrackParam
956019b6	202	// from Geant3 parameters pointed to by "VGeant3",
956019b6	203	// assumed to be calculated for forward motion in Z.
a9e2aefa	204	// "InverseBendingMomentum" is signed with "Charge".
	205	this->fNonBendingCoor = VGeant3[0]; // X
	206	this->fBendingCoor = VGeant3[1]; // Y
	207	this->fZ = VGeant3[2]; // Z
	208	Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]);
	209	this->fInverseBendingMomentum = Charge / pYZ;
	210	this->fBendingSlope = VGeant3[4] / VGeant3[5];
	211	this->fNonBendingSlope = VGeant3[3] / VGeant3[5];
	212	}
	213
	214	//__________________________________________________________________________
	215	void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam)
	216	{
	217	// Track parameters extrapolated from current track parameters ("this")
	218	// to both chambers of the station(0..) "Station"
	219	// are returned in the array (dimension 2) of track parameters
	220	// pointed to by "TrackParam" (index 0 and 1 for first and second chambers).
	221	Double_t extZ[2], z1, z2;
	222	Int_t i1, i2;
	223	AliMUON pMUON = (AliMUON) gAlice->GetModule("MUON"); // necessary ????
	224	// range of Station to be checked ????
	225	z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber
	226	z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber
	227	// First and second Z to extrapolate at
	228	if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;}
	229	else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;}
	230	else {
	231	cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl;
	232	cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 <<
	233	") and z2 (" << z2 << ") of station(0..) " << Station << endl;
	234	}
	235	extZ[i1] = z1;
	236	extZ[i2] = z2;
	237	// copy of track parameters
	238	TrackParam[i1] = *this;
	239	// first extrapolation
	240	(&(TrackParam[i1]))->ExtrapToZ(extZ[0]);
	241	TrackParam[i2] = TrackParam[i1];
	242	// second extrapolation
	243	(&(TrackParam[i2]))->ExtrapToZ(extZ[1]);
	244	return;
	245	}
	246
04b5ea16	247	//__________________________________________________________________________
	248	void AliMUONTrackParam::ExtrapToVertex()
	249	{
	250	// Extrapolation to the vertex.
	251	// Returns the track parameters resulting from the extrapolation,
	252	// in the current TrackParam.
956019b6	253	// Changes parameters according to Branson correction through the absorber
04b5ea16	254
	255	Double_t zAbsorber = 503.0; // to be coherent with the Geant absorber geometry !!!!
	256	// Extrapolates track parameters upstream to the "Z" end of the front absorber
	257	ExtrapToZ(zAbsorber);
	258	// Makes Branson correction (multiple scattering + energy loss)
	259	BransonCorrection();
	260	}
	261
	262	//__________________________________________________________________________
	263	void AliMUONTrackParam::BransonCorrection()
	264	{
	265	// Branson correction of track parameters
	266	// the entry parameters have to be calculated at the end of the absorber
	267	Double_t zEndAbsorber, zBP, xBP, yBP;
	268	Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
	269	Int_t sign;
	270	// Would it be possible to calculate all that from Geant configuration ????
956019b6	271	// and to get the Branson parameters from a function in ABSO module ????
956019b6	272	// with an eventual contribution from other detectors like START ????
04b5ea16	273	// Radiation lengths outer part theta > 3 degres
	274	static Double_t x01[9] = { 18.8, // C (cm)
	275	10.397, // Concrete (cm)
	276	0.56, // Plomb (cm)
	277	47.26, // Polyethylene (cm)
	278	0.56, // Plomb (cm)
	279	47.26, // Polyethylene (cm)
	280	0.56, // Plomb (cm)
	281	47.26, // Polyethylene (cm)
	282	0.56 }; // Plomb (cm)
	283	// inner part theta < 3 degres
	284	static Double_t x02[3] = { 18.8, // C (cm)
	285	10.397, // Concrete (cm)
	286	0.35 }; // W (cm)
	287	// z positions of the materials inside the absober outer part theta > 3 degres
	288	static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 };
	289	// inner part theta < 3 degres
	290	static Double_t z2[4] = { 90, 315, 467, 503 };
	291	static Bool_t first = kTRUE;
	292	static Double_t zBP1, zBP2, rLimit;
	293	// Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call)
	294	if (first) {
	295	first = kFALSE;
	296	Double_t aNBP = 0.0;
	297	Double_t aDBP = 0.0;
88962f0c	298	Int_t iBound;
	299
	300	for (iBound = 0; iBound < 9; iBound++) {
04b5ea16	301	aNBP = aNBP +
	302	(z1[iBound+1] * z1[iBound+1] * z1[iBound+1] -
	303	z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound];
	304	aDBP = aDBP +
	305	(z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound];
	306	}
	307	zBP1 = (2.0 * aNBP) / (3.0 * aDBP);
	308	aNBP = 0.0;
	309	aDBP = 0.0;
88962f0c	310	for (iBound = 0; iBound < 3; iBound++) {
04b5ea16	311	aNBP = aNBP +
	312	(z2[iBound+1] * z2[iBound+1] * z2[iBound+1] -
	313	z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound];
	314	aDBP = aDBP +
	315	(z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound];
	316	}
	317	zBP2 = (2.0 * aNBP) / (3.0 * aDBP);
	318	rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
	319	}
	320
	321	pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
	322	sign = 1;
	323	if (fInverseBendingMomentum < 0) sign = -1;
	324	pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope));
	325	pX = pZ * fNonBendingSlope;
	326	pY = pZ * fBendingSlope;
	327	pTotal = TMath::Sqrt(pYZ pYZ + pX pX);
	328	xEndAbsorber = fNonBendingCoor;
	329	yEndAbsorber = fBendingCoor;
	330	radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
	331
	332	if (radiusEndAbsorber2 > rLimit*rLimit) {
	333	zEndAbsorber = z1[9];
	334	zBP = zBP1;
	335	} else {
956019b6	336	zEndAbsorber = z2[3];
04b5ea16	337	zBP = zBP2;
	338	}
	339
	340	xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
	341	yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
	342
	343	// new parameters after Branson and energy loss corrections
	344	pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP);
	345	pX = pZ * xBP / zBP;
	346	pY = pZ * yBP / zBP;
	347	fBendingSlope = pY / pZ;
	348	fNonBendingSlope = pX / pZ;
	349
	350	pT = TMath::Sqrt(pX * pX + pY * pY);
	351	theta = TMath::ATan2(pT, pZ);
	352	pTotal =
	353	TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
	354
	355	fInverseBendingMomentum = (sign / pTotal) *
	356	TMath::Sqrt(1.0 +
	357	fBendingSlope * fBendingSlope +
	358	fNonBendingSlope * fNonBendingSlope) /
	359	TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
	360
	361	// vertex position at (0,0,0)
	362	// should be taken from vertex measurement ???
	363	fBendingCoor = 0.0;
	364	fNonBendingCoor = 0;
	365	fZ= 0;
	366	}
	367
	368	//__________________________________________________________________________
	369	Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t rLimit, Double_t pTotal, Double_t theta, Double_t xEndAbsorber, Double_t yEndAbsorber)
	370	{
	371	// Returns the total momentum corrected from energy loss in the front absorber
	372	Double_t deltaP, pTotalCorrected;
	373
	374	Double_t radiusEndAbsorber2 =
	375	xEndAbsorber xEndAbsorber + yEndAbsorber yEndAbsorber;
	376	// Parametrization to be redone according to change of absorber material ????
956019b6	377	// See remark in function BransonCorrection !!!!
04b5ea16	378	// The name is not so good, and there are many arguments !!!!
	379	if (radiusEndAbsorber2 < rLimit * rLimit) {
	380	if (pTotal < 15) {
	381	deltaP = 2.737 + 0.0494 * pTotal - 0.001123 * pTotal * pTotal;
	382	} else {
	383	deltaP = 3.0643 + 0.01346 *pTotal;
	384	}
	385	} else {
	386	if (pTotal < 15) {
	387	deltaP = 2.1380 + 0.0351 * pTotal - 0.000853 * pTotal * pTotal;
	388	} else {
	389	deltaP = 2.407 + 0.00702 * pTotal;
	390	}
	391	}
	392	pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
	393	return pTotalCorrected;
	394	}
	395