[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 1.6  2000/09/19 09:49:50  gosset
AliMUONEventReconstructor package
* track extrapolation independent from reco_muon.F, use of AliMagF...
* possibility to use new magnetic field (automatic from generated root file)

Revision 1.5  2000/07/18 16:04:06  gosset
AliMUONEventReconstructor package:
* a few minor modifications and more comments
* a few corrections
  * right sign for Z of raw clusters
  * right loop over chambers inside station
  * symmetrized covariance matrix for measurements (TrackChi2MCS)
  * right sign of charge in extrapolation (ExtrapToZ)
  * right zEndAbsorber for Branson correction below 3 degrees
* use of TVirtualFitter instead of TMinuit for AliMUONTrack::Fit
* no parameter for AliMUONTrack::Fit() but more fit parameters in Track object

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

  // A few calls in Fortran or from Fortran (extrap.F).
  // Needed, instead of calls to Geant subroutines,
  // because double precision is necessary for track fit converging with Minuit.
  // The "extrap" functions should be translated into C++ ????
#ifndef WIN32 
# define extrap_onestep_helix extrap_onestep_helix_
# define extrap_onestep_helix3 extrap_onestep_helix3_
# define extrap_onestep_rungekutta extrap_onestep_rungekutta_
# define gufld_double gufld_double_
#else 
# define extrap_onestep_helix EXTRAP_ONESTEP_HELIX
# define extrap_onestep_helix3 EXTRAP_ONESTEP_HELIX3
# define extrap_onestep_rungekutta EXTRAP_ONESTEP_RUNGEKUTTA
# define gufld_double GUFLD_DOUBLE
#endif 

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

  void type_of_call extrap_onestep_helix3
  (Double_t &Field, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New);

  void type_of_call extrap_onestep_rungekutta
  (Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New);

  void type_of_call gufld_double(Double_t *Position, Double_t *Field) {
    // interface to "gAlice->Field()->Field" for arguments in double precision
    Float_t x[3], b[3];
    x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2];
    gAlice->Field()->Field(x, b);
    Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2];
  }
}

// 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.
  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 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 EXTRAP_ONESTEP
  SetGeant3Parameters(vGeant3, forwardBackward);
  // sign of charge (sign of fInverseBendingMomentum if forward motion)
  // must be 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++;
    // Option for switching between helix and Runge-Kutta ???? 
    // extrap_onestep_rungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New);
    extrap_onestep_helix(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 ????
  // 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 = -1, i2 = -1; // = -1 to avoid compilation warnings
  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	$Log$
ecfa008b	18	Revision 1.6 2000/09/19 09:49:50 gosset
	19	AliMUONEventReconstructor package
	20	* track extrapolation independent from reco_muon.F, use of AliMagF...
	21	* possibility to use new magnetic field (automatic from generated root file)
	22
a6f03ddb	23	Revision 1.5 2000/07/18 16:04:06 gosset
	24	AliMUONEventReconstructor package:
	25	* a few minor modifications and more comments
	26	* a few corrections
	27	* right sign for Z of raw clusters
	28	* right loop over chambers inside station
	29	* symmetrized covariance matrix for measurements (TrackChi2MCS)
	30	* right sign of charge in extrapolation (ExtrapToZ)
	31	* right zEndAbsorber for Branson correction below 3 degrees
	32	* use of TVirtualFitter instead of TMinuit for AliMUONTrack::Fit
	33	* no parameter for AliMUONTrack::Fit() but more fit parameters in Track object
	34
956019b6	35	Revision 1.4 2000/07/03 07:53:31 morsch
	36	Double declaration problem on HP solved.
	37
88962f0c	38	Revision 1.3 2000/06/30 10:15:48 gosset
	39	Changes to EventReconstructor...:
	40	precision fit with multiple Coulomb scattering;
	41	extrapolation to vertex with Branson correction in absorber (JPC)
	42
04b5ea16	43	Revision 1.2 2000/06/15 07:58:49 morsch
	44	Code from MUON-dev joined
	45
a9e2aefa	46	Revision 1.1.2.3 2000/06/09 21:03:09 morsch
	47	Make includes consistent with new file structure.
	48
	49	Revision 1.1.2.2 2000/06/09 12:58:05 gosset
	50	Removed comment beginnings in Log sections of .cxx files
	51	Suppressed most violations of coding rules
	52
	53	Revision 1.1.2.1 2000/06/07 14:44:53 gosset
	54	Addition of files for track reconstruction in C++
	55	*/
	56
	57	//__________________________________________________________________________
	58	//
	59	// Track parameters in ALICE dimuon spectrometer
	60	//__________________________________________________________________________
	61
	62	#include <iostream.h>
	63
	64	#include "AliCallf77.h"
	65	#include "AliMUON.h"
	66	#include "AliMUONHitForRec.h"
	67	#include "AliMUONSegment.h"
	68	#include "AliMUONTrackParam.h"
	69	#include "AliMUONChamber.h"
	70	#include "AliRun.h"
	71
	72	ClassImp(AliMUONTrackParam) // Class implementation in ROOT context
	73
a6f03ddb	74	// A few calls in Fortran or from Fortran (extrap.F).
	75	// Needed, instead of calls to Geant subroutines,
	76	// because double precision is necessary for track fit converging with Minuit.
	77	// The "extrap" functions should be translated into C++ ????
a9e2aefa	78	#ifndef WIN32
a6f03ddb	79	# define extrap_onestep_helix extrap_onestep_helix_
	80	# define extrap_onestep_helix3 extrap_onestep_helix3_
	81	# define extrap_onestep_rungekutta extrap_onestep_rungekutta_
	82	# define gufld_double gufld_double_
a9e2aefa	83	#else
a6f03ddb	84	# define extrap_onestep_helix EXTRAP_ONESTEP_HELIX
	85	# define extrap_onestep_helix3 EXTRAP_ONESTEP_HELIX3
	86	# define extrap_onestep_rungekutta EXTRAP_ONESTEP_RUNGEKUTTA
	87	# define gufld_double GUFLD_DOUBLE
a9e2aefa	88	#endif
a9e2aefa	89
a6f03ddb	90	extern "C" {
	91	void type_of_call extrap_onestep_helix
	92	(Double_t &Charge, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	93
	94	void type_of_call extrap_onestep_helix3
	95	(Double_t &Field, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	96
	97	void type_of_call extrap_onestep_rungekutta
	98	(Double_t &Charge, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	99
	100	void type_of_call gufld_double(Double_t Position, Double_t Field) {
	101	// interface to "gAlice->Field()->Field" for arguments in double precision
	102	Float_t x[3], b[3];
	103	x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2];
	104	gAlice->Field()->Field(x, b);
	105	Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2];
	106	}
a9e2aefa	107	}
	108
	109	// Inline functions for Get and Set: inline removed because it does not work !!!!
	110	Double_t AliMUONTrackParam::GetInverseBendingMomentum(void) {
	111	// Get fInverseBendingMomentum
	112	return fInverseBendingMomentum;}
	113	void AliMUONTrackParam::SetInverseBendingMomentum(Double_t InverseBendingMomentum) {
	114	// Set fInverseBendingMomentum
	115	fInverseBendingMomentum = InverseBendingMomentum;}
	116	Double_t AliMUONTrackParam::GetBendingSlope(void) {
	117	// Get fBendingSlope
	118	return fBendingSlope;}
	119	void AliMUONTrackParam::SetBendingSlope(Double_t BendingSlope) {
	120	// Set fBendingSlope
	121	fBendingSlope = BendingSlope;}
	122	Double_t AliMUONTrackParam::GetNonBendingSlope(void) {
	123	// Get fNonBendingSlope
	124	return fNonBendingSlope;}
	125	void AliMUONTrackParam::SetNonBendingSlope(Double_t NonBendingSlope) {
	126	// Set fNonBendingSlope
	127	fNonBendingSlope = NonBendingSlope;}
	128	Double_t AliMUONTrackParam::GetZ(void) {
	129	// Get fZ
	130	return fZ;}
	131	void AliMUONTrackParam::SetZ(Double_t Z) {
	132	// Set fZ
	133	fZ = Z;}
	134	Double_t AliMUONTrackParam::GetBendingCoor(void) {
	135	// Get fBendingCoor
	136	return fBendingCoor;}
	137	void AliMUONTrackParam::SetBendingCoor(Double_t BendingCoor) {
	138	// Set fBendingCoor
	139	fBendingCoor = BendingCoor;}
	140	Double_t AliMUONTrackParam::GetNonBendingCoor(void) {
	141	// Get fNonBendingCoor
	142	return fNonBendingCoor;}
	143	void AliMUONTrackParam::SetNonBendingCoor(Double_t NonBendingCoor) {
	144	// Set fNonBendingCoor
	145	fNonBendingCoor = NonBendingCoor;}
	146
	147	//__________________________________________________________________________
	148	void AliMUONTrackParam::ExtrapToZ(Double_t Z)
	149	{
	150	// Track parameter extrapolation to the plane at "Z".
	151	// On return, the track parameters resulting from the extrapolation
	152	// replace the current track parameters.
a9e2aefa	153	if (this->fZ == Z) return; // nothing to be done if same Z
	154	Double_t forwardBackward; // +1 if forward, -1 if backward
	155	if (Z > this->fZ) forwardBackward = 1.0;
	156	else forwardBackward = -1.0;
a6f03ddb	157	Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ????
a9e2aefa	158	Int_t iGeant3, stepNumber;
	159	Int_t maxStepNumber = 5000; // in parameter ????
	160	// For safety: return kTRUE or kFALSE ????
a6f03ddb	161	// Parameter vector for calling EXTRAP_ONESTEP
a9e2aefa	162	SetGeant3Parameters(vGeant3, forwardBackward);
956019b6	163	// sign of charge (sign of fInverseBendingMomentum if forward motion)
a6f03ddb	164	// must be changed if backward extrapolation
956019b6	165	Double_t chargeExtrap = forwardBackward *
956019b6	166	TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum);
a9e2aefa	167	Double_t stepLength = 6.0; // in parameter ????
	168	// Extrapolation loop
	169	stepNumber = 0;
	170	while (((forwardBackward * (vGeant3[2] - Z)) <= 0.0) &&
	171	(stepNumber < maxStepNumber)) {
	172	stepNumber++;
a6f03ddb	173	// Option for switching between helix and Runge-Kutta ????
	174	// extrap_onestep_rungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New);
	175	extrap_onestep_helix(chargeExtrap, stepLength, vGeant3, vGeant3New);
a9e2aefa	176	if ((forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z
	177	// better use TArray ????
	178	for (iGeant3 = 0; iGeant3 < 7; iGeant3++)
	179	{vGeant3[iGeant3] = vGeant3New[iGeant3];}
	180	}
	181	// check maxStepNumber ????
a9e2aefa	182	// Interpolation back to exact Z (2nd order)
	183	// should be in function ???? using TArray ????
	184	Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2
	185	Double_t dZ1i = Z - vGeant3[2]; // 1-i
	186	Double_t dZi2 = vGeant3New[2] - Z; // i->2
	187	Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12;
	188	Double_t xSecond =
	189	((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12;
	190	Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12;
	191	Double_t ySecond =
	192	((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12;
	193	vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X
	194	vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y
	195	vGeant3[2] = Z; // Z
	196	Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i);
	197	Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i);
956019b6	198	// (PX, PY, PZ)/PTOT assuming forward motion
a9e2aefa	199	vGeant3[5] =
	200	1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT
	201	vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT
	202	vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT
956019b6	203	// Track parameters from Geant3 parameters,
	204	// with charge back for forward motion
	205	GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward);
a9e2aefa	206	}
	207
	208	//__________________________________________________________________________
	209	void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward)
	210	{
	211	// Set vector of Geant3 parameters pointed to by "VGeant3"
	212	// from track parameters in current AliMUONTrackParam.
	213	// Since AliMUONTrackParam is only geometry, one uses "ForwardBackward"
	214	// to know whether the particle is going forward (+1) or backward (-1).
	215	VGeant3[0] = this->fNonBendingCoor; // X
	216	VGeant3[1] = this->fBendingCoor; // Y
	217	VGeant3[2] = this->fZ; // Z
	218	Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum);
	219	Double_t pZ =
	220	pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope);
	221	VGeant3[6] =
	222	TMath::Sqrt(pYZ * pYZ +
	223	pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT
	224	VGeant3[5] = ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT
	225	VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT
	226	VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT
	227	}
	228
	229	//__________________________________________________________________________
	230	void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge)
	231	{
	232	// Get track parameters in current AliMUONTrackParam
956019b6	233	// from Geant3 parameters pointed to by "VGeant3",
956019b6	234	// assumed to be calculated for forward motion in Z.
a9e2aefa	235	// "InverseBendingMomentum" is signed with "Charge".
	236	this->fNonBendingCoor = VGeant3[0]; // X
	237	this->fBendingCoor = VGeant3[1]; // Y
	238	this->fZ = VGeant3[2]; // Z
	239	Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]);
	240	this->fInverseBendingMomentum = Charge / pYZ;
	241	this->fBendingSlope = VGeant3[4] / VGeant3[5];
	242	this->fNonBendingSlope = VGeant3[3] / VGeant3[5];
	243	}
	244
	245	//__________________________________________________________________________
	246	void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam)
	247	{
	248	// Track parameters extrapolated from current track parameters ("this")
	249	// to both chambers of the station(0..) "Station"
	250	// are returned in the array (dimension 2) of track parameters
	251	// pointed to by "TrackParam" (index 0 and 1 for first and second chambers).
	252	Double_t extZ[2], z1, z2;
ecfa008b	253	Int_t i1 = -1, i2 = -1; // = -1 to avoid compilation warnings
a9e2aefa	254	AliMUON pMUON = (AliMUON) gAlice->GetModule("MUON"); // necessary ????
	255	// range of Station to be checked ????
	256	z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber
	257	z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber
	258	// First and second Z to extrapolate at
	259	if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;}
	260	else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;}
	261	else {
	262	cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl;
	263	cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 <<
	264	") and z2 (" << z2 << ") of station(0..) " << Station << endl;
	265	}
	266	extZ[i1] = z1;
	267	extZ[i2] = z2;
	268	// copy of track parameters
	269	TrackParam[i1] = *this;
	270	// first extrapolation
	271	(&(TrackParam[i1]))->ExtrapToZ(extZ[0]);
	272	TrackParam[i2] = TrackParam[i1];
	273	// second extrapolation
	274	(&(TrackParam[i2]))->ExtrapToZ(extZ[1]);
	275	return;
	276	}
	277
04b5ea16	278	//__________________________________________________________________________
	279	void AliMUONTrackParam::ExtrapToVertex()
	280	{
	281	// Extrapolation to the vertex.
	282	// Returns the track parameters resulting from the extrapolation,
	283	// in the current TrackParam.
956019b6	284	// Changes parameters according to Branson correction through the absorber
04b5ea16	285
	286	Double_t zAbsorber = 503.0; // to be coherent with the Geant absorber geometry !!!!
	287	// Extrapolates track parameters upstream to the "Z" end of the front absorber
	288	ExtrapToZ(zAbsorber);
	289	// Makes Branson correction (multiple scattering + energy loss)
	290	BransonCorrection();
	291	}
	292
	293	//__________________________________________________________________________
	294	void AliMUONTrackParam::BransonCorrection()
	295	{
	296	// Branson correction of track parameters
	297	// the entry parameters have to be calculated at the end of the absorber
	298	Double_t zEndAbsorber, zBP, xBP, yBP;
	299	Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
	300	Int_t sign;
	301	// Would it be possible to calculate all that from Geant configuration ????
956019b6	302	// and to get the Branson parameters from a function in ABSO module ????
956019b6	303	// with an eventual contribution from other detectors like START ????
04b5ea16	304	// Radiation lengths outer part theta > 3 degres
	305	static Double_t x01[9] = { 18.8, // C (cm)
	306	10.397, // Concrete (cm)
	307	0.56, // Plomb (cm)
	308	47.26, // Polyethylene (cm)
	309	0.56, // Plomb (cm)
	310	47.26, // Polyethylene (cm)
	311	0.56, // Plomb (cm)
	312	47.26, // Polyethylene (cm)
	313	0.56 }; // Plomb (cm)
	314	// inner part theta < 3 degres
	315	static Double_t x02[3] = { 18.8, // C (cm)
	316	10.397, // Concrete (cm)
	317	0.35 }; // W (cm)
	318	// z positions of the materials inside the absober outer part theta > 3 degres
	319	static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 };
	320	// inner part theta < 3 degres
	321	static Double_t z2[4] = { 90, 315, 467, 503 };
	322	static Bool_t first = kTRUE;
	323	static Double_t zBP1, zBP2, rLimit;
	324	// Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call)
	325	if (first) {
	326	first = kFALSE;
	327	Double_t aNBP = 0.0;
	328	Double_t aDBP = 0.0;
88962f0c	329	Int_t iBound;
	330
	331	for (iBound = 0; iBound < 9; iBound++) {
04b5ea16	332	aNBP = aNBP +
	333	(z1[iBound+1] * z1[iBound+1] * z1[iBound+1] -
	334	z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound];
	335	aDBP = aDBP +
	336	(z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound];
	337	}
	338	zBP1 = (2.0 * aNBP) / (3.0 * aDBP);
	339	aNBP = 0.0;
	340	aDBP = 0.0;
88962f0c	341	for (iBound = 0; iBound < 3; iBound++) {
04b5ea16	342	aNBP = aNBP +
	343	(z2[iBound+1] * z2[iBound+1] * z2[iBound+1] -
	344	z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound];
	345	aDBP = aDBP +
	346	(z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound];
	347	}
	348	zBP2 = (2.0 * aNBP) / (3.0 * aDBP);
	349	rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
	350	}
	351
	352	pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
	353	sign = 1;
	354	if (fInverseBendingMomentum < 0) sign = -1;
	355	pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope));
	356	pX = pZ * fNonBendingSlope;
	357	pY = pZ * fBendingSlope;
	358	pTotal = TMath::Sqrt(pYZ pYZ + pX pX);
	359	xEndAbsorber = fNonBendingCoor;
	360	yEndAbsorber = fBendingCoor;
	361	radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
	362
	363	if (radiusEndAbsorber2 > rLimit*rLimit) {
	364	zEndAbsorber = z1[9];
	365	zBP = zBP1;
	366	} else {
956019b6	367	zEndAbsorber = z2[3];
04b5ea16	368	zBP = zBP2;
	369	}
	370
	371	xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
	372	yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
	373
	374	// new parameters after Branson and energy loss corrections
	375	pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP);
	376	pX = pZ * xBP / zBP;
	377	pY = pZ * yBP / zBP;
	378	fBendingSlope = pY / pZ;
	379	fNonBendingSlope = pX / pZ;
	380
	381	pT = TMath::Sqrt(pX * pX + pY * pY);
	382	theta = TMath::ATan2(pT, pZ);
	383	pTotal =
	384	TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
	385
	386	fInverseBendingMomentum = (sign / pTotal) *
	387	TMath::Sqrt(1.0 +
	388	fBendingSlope * fBendingSlope +
	389	fNonBendingSlope * fNonBendingSlope) /
	390	TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
	391
	392	// vertex position at (0,0,0)
	393	// should be taken from vertex measurement ???
	394	fBendingCoor = 0.0;
	395	fNonBendingCoor = 0;
	396	fZ= 0;
	397	}
	398
	399	//__________________________________________________________________________
	400	Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t rLimit, Double_t pTotal, Double_t theta, Double_t xEndAbsorber, Double_t yEndAbsorber)
	401	{
	402	// Returns the total momentum corrected from energy loss in the front absorber
	403	Double_t deltaP, pTotalCorrected;
	404
	405	Double_t radiusEndAbsorber2 =
	406	xEndAbsorber xEndAbsorber + yEndAbsorber yEndAbsorber;
	407	// Parametrization to be redone according to change of absorber material ????
956019b6	408	// See remark in function BransonCorrection !!!!
04b5ea16	409	// The name is not so good, and there are many arguments !!!!
	410	if (radiusEndAbsorber2 < rLimit * rLimit) {
	411	if (pTotal < 15) {
	412	deltaP = 2.737 + 0.0494 * pTotal - 0.001123 * pTotal * pTotal;
	413	} else {
	414	deltaP = 3.0643 + 0.01346 *pTotal;
	415	}
	416	} else {
	417	if (pTotal < 15) {
	418	deltaP = 2.1380 + 0.0351 * pTotal - 0.000853 * pTotal * pTotal;
	419	} else {
	420	deltaP = 2.407 + 0.00702 * pTotal;
	421	}
	422	}
	423	pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
	424	return pTotalCorrected;
	425	}
	426