[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 1.2  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;
  // charge must be changed with momentum for backward motion
  Double_t charge =
    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(charge, 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);
  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
  GetFromGeant3Parameters(vGeant3, charge);
}

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