[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 1.9  2000/10/16 15:30:40  gosset
TotalMomentumEnergyLoss:
correction for change in the absorber composition (JP Cussonneau)

Revision 1.8  2000/10/02 21:28:09  fca
Removal of useless dependecies via forward declarations

Revision 1.7  2000/10/02 16:58:29  egangler
Cleaning of the code :
-> coding conventions
-> void Streamers
-> some useless includes removed or replaced by "class" statement

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 "AliMUONTrackParam.h" 
#include "AliMUONChamber.h"
#include "AliRun.h" 
#include "AliMagF.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];
  }
}

  //__________________________________________________________________________
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;
    }
  }
  deltaP = 0.88 * deltaP; // !!!! changes in the absorber composition ????
  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	$Log$
3831f268	18	Revision 1.9 2000/10/16 15:30:40 gosset
	19	TotalMomentumEnergyLoss:
	20	correction for change in the absorber composition (JP Cussonneau)
	21
6372a28d	22	Revision 1.8 2000/10/02 21:28:09 fca
	23	Removal of useless dependecies via forward declarations
	24
94de3818	25	Revision 1.7 2000/10/02 16:58:29 egangler
	26	Cleaning of the code :
	27	-> coding conventions
	28	-> void Streamers
	29	-> some useless includes removed or replaced by "class" statement
	30
ecfa008b	31	Revision 1.6 2000/09/19 09:49:50 gosset
	32	AliMUONEventReconstructor package
	33	* track extrapolation independent from reco_muon.F, use of AliMagF...
	34	* possibility to use new magnetic field (automatic from generated root file)
	35
a6f03ddb	36	Revision 1.5 2000/07/18 16:04:06 gosset
	37	AliMUONEventReconstructor package:
	38	* a few minor modifications and more comments
	39	* a few corrections
	40	* right sign for Z of raw clusters
	41	* right loop over chambers inside station
	42	* symmetrized covariance matrix for measurements (TrackChi2MCS)
	43	* right sign of charge in extrapolation (ExtrapToZ)
	44	* right zEndAbsorber for Branson correction below 3 degrees
	45	* use of TVirtualFitter instead of TMinuit for AliMUONTrack::Fit
	46	* no parameter for AliMUONTrack::Fit() but more fit parameters in Track object
	47
956019b6	48	Revision 1.4 2000/07/03 07:53:31 morsch
	49	Double declaration problem on HP solved.
	50
88962f0c	51	Revision 1.3 2000/06/30 10:15:48 gosset
	52	Changes to EventReconstructor...:
	53	precision fit with multiple Coulomb scattering;
	54	extrapolation to vertex with Branson correction in absorber (JPC)
	55
04b5ea16	56	Revision 1.2 2000/06/15 07:58:49 morsch
	57	Code from MUON-dev joined
	58
a9e2aefa	59	Revision 1.1.2.3 2000/06/09 21:03:09 morsch
	60	Make includes consistent with new file structure.
	61
	62	Revision 1.1.2.2 2000/06/09 12:58:05 gosset
	63	Removed comment beginnings in Log sections of .cxx files
	64	Suppressed most violations of coding rules
	65
	66	Revision 1.1.2.1 2000/06/07 14:44:53 gosset
	67	Addition of files for track reconstruction in C++
	68	*/
	69
3831f268	70	///////////////////////////////////////////////////
	71	//
	72	// Track parameters
	73	// in
	74	// ALICE
	75	// dimuon
	76	// spectrometer
a9e2aefa	77	//
3831f268	78	///////////////////////////////////////////////////
a9e2aefa	79
	80	#include <iostream.h>
	81
	82	#include "AliCallf77.h"
3831f268	83	#include "AliMUON.h"
a9e2aefa	84	#include "AliMUONTrackParam.h"
3831f268	85	#include "AliMUONChamber.h"
a9e2aefa	86	#include "AliRun.h"
94de3818	87	#include "AliMagF.h"
a9e2aefa	88
	89	ClassImp(AliMUONTrackParam) // Class implementation in ROOT context
	90
a6f03ddb	91	// A few calls in Fortran or from Fortran (extrap.F).
	92	// Needed, instead of calls to Geant subroutines,
	93	// because double precision is necessary for track fit converging with Minuit.
	94	// The "extrap" functions should be translated into C++ ????
a9e2aefa	95	#ifndef WIN32
a6f03ddb	96	# define extrap_onestep_helix extrap_onestep_helix_
	97	# define extrap_onestep_helix3 extrap_onestep_helix3_
	98	# define extrap_onestep_rungekutta extrap_onestep_rungekutta_
	99	# define gufld_double gufld_double_
a9e2aefa	100	#else
a6f03ddb	101	# define extrap_onestep_helix EXTRAP_ONESTEP_HELIX
	102	# define extrap_onestep_helix3 EXTRAP_ONESTEP_HELIX3
	103	# define extrap_onestep_rungekutta EXTRAP_ONESTEP_RUNGEKUTTA
	104	# define gufld_double GUFLD_DOUBLE
a9e2aefa	105	#endif
a9e2aefa	106
a6f03ddb	107	extern "C" {
	108	void type_of_call extrap_onestep_helix
	109	(Double_t &Charge, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	110
	111	void type_of_call extrap_onestep_helix3
	112	(Double_t &Field, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	113
	114	void type_of_call extrap_onestep_rungekutta
	115	(Double_t &Charge, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	116
	117	void type_of_call gufld_double(Double_t Position, Double_t Field) {
	118	// interface to "gAlice->Field()->Field" for arguments in double precision
	119	Float_t x[3], b[3];
	120	x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2];
	121	gAlice->Field()->Field(x, b);
	122	Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2];
	123	}
a9e2aefa	124	}
a9e2aefa	125
a9e2aefa	126	//__________________________________________________________________________
	127	void AliMUONTrackParam::ExtrapToZ(Double_t Z)
	128	{
	129	// Track parameter extrapolation to the plane at "Z".
	130	// On return, the track parameters resulting from the extrapolation
	131	// replace the current track parameters.
a9e2aefa	132	if (this->fZ == Z) return; // nothing to be done if same Z
	133	Double_t forwardBackward; // +1 if forward, -1 if backward
	134	if (Z > this->fZ) forwardBackward = 1.0;
	135	else forwardBackward = -1.0;
a6f03ddb	136	Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ????
a9e2aefa	137	Int_t iGeant3, stepNumber;
	138	Int_t maxStepNumber = 5000; // in parameter ????
	139	// For safety: return kTRUE or kFALSE ????
a6f03ddb	140	// Parameter vector for calling EXTRAP_ONESTEP
a9e2aefa	141	SetGeant3Parameters(vGeant3, forwardBackward);
956019b6	142	// sign of charge (sign of fInverseBendingMomentum if forward motion)
a6f03ddb	143	// must be changed if backward extrapolation
956019b6	144	Double_t chargeExtrap = forwardBackward *
956019b6	145	TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum);
a9e2aefa	146	Double_t stepLength = 6.0; // in parameter ????
	147	// Extrapolation loop
	148	stepNumber = 0;
	149	while (((forwardBackward * (vGeant3[2] - Z)) <= 0.0) &&
	150	(stepNumber < maxStepNumber)) {
	151	stepNumber++;
a6f03ddb	152	// Option for switching between helix and Runge-Kutta ????
	153	// extrap_onestep_rungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New);
	154	extrap_onestep_helix(chargeExtrap, stepLength, vGeant3, vGeant3New);
a9e2aefa	155	if ((forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z
	156	// better use TArray ????
	157	for (iGeant3 = 0; iGeant3 < 7; iGeant3++)
	158	{vGeant3[iGeant3] = vGeant3New[iGeant3];}
	159	}
	160	// check maxStepNumber ????
a9e2aefa	161	// Interpolation back to exact Z (2nd order)
	162	// should be in function ???? using TArray ????
	163	Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2
	164	Double_t dZ1i = Z - vGeant3[2]; // 1-i
	165	Double_t dZi2 = vGeant3New[2] - Z; // i->2
	166	Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12;
	167	Double_t xSecond =
	168	((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12;
	169	Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12;
	170	Double_t ySecond =
	171	((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12;
	172	vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X
	173	vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y
	174	vGeant3[2] = Z; // Z
	175	Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i);
	176	Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i);
956019b6	177	// (PX, PY, PZ)/PTOT assuming forward motion
a9e2aefa	178	vGeant3[5] =
	179	1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT
	180	vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT
	181	vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT
956019b6	182	// Track parameters from Geant3 parameters,
	183	// with charge back for forward motion
	184	GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward);
a9e2aefa	185	}
	186
	187	//__________________________________________________________________________
	188	void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward)
	189	{
	190	// Set vector of Geant3 parameters pointed to by "VGeant3"
	191	// from track parameters in current AliMUONTrackParam.
	192	// Since AliMUONTrackParam is only geometry, one uses "ForwardBackward"
	193	// to know whether the particle is going forward (+1) or backward (-1).
	194	VGeant3[0] = this->fNonBendingCoor; // X
	195	VGeant3[1] = this->fBendingCoor; // Y
	196	VGeant3[2] = this->fZ; // Z
	197	Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum);
	198	Double_t pZ =
	199	pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope);
	200	VGeant3[6] =
	201	TMath::Sqrt(pYZ * pYZ +
	202	pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT
	203	VGeant3[5] = ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT
	204	VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT
	205	VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT
	206	}
	207
	208	//__________________________________________________________________________
	209	void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge)
	210	{
	211	// Get track parameters in current AliMUONTrackParam
956019b6	212	// from Geant3 parameters pointed to by "VGeant3",
956019b6	213	// assumed to be calculated for forward motion in Z.
a9e2aefa	214	// "InverseBendingMomentum" is signed with "Charge".
	215	this->fNonBendingCoor = VGeant3[0]; // X
	216	this->fBendingCoor = VGeant3[1]; // Y
	217	this->fZ = VGeant3[2]; // Z
	218	Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]);
	219	this->fInverseBendingMomentum = Charge / pYZ;
	220	this->fBendingSlope = VGeant3[4] / VGeant3[5];
	221	this->fNonBendingSlope = VGeant3[3] / VGeant3[5];
	222	}
	223
	224	//__________________________________________________________________________
	225	void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam)
	226	{
	227	// Track parameters extrapolated from current track parameters ("this")
	228	// to both chambers of the station(0..) "Station"
	229	// are returned in the array (dimension 2) of track parameters
	230	// pointed to by "TrackParam" (index 0 and 1 for first and second chambers).
	231	Double_t extZ[2], z1, z2;
ecfa008b	232	Int_t i1 = -1, i2 = -1; // = -1 to avoid compilation warnings
a9e2aefa	233	AliMUON pMUON = (AliMUON) gAlice->GetModule("MUON"); // necessary ????
	234	// range of Station to be checked ????
	235	z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber
	236	z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber
	237	// First and second Z to extrapolate at
	238	if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;}
	239	else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;}
	240	else {
	241	cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl;
	242	cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 <<
	243	") and z2 (" << z2 << ") of station(0..) " << Station << endl;
	244	}
	245	extZ[i1] = z1;
	246	extZ[i2] = z2;
	247	// copy of track parameters
	248	TrackParam[i1] = *this;
	249	// first extrapolation
	250	(&(TrackParam[i1]))->ExtrapToZ(extZ[0]);
	251	TrackParam[i2] = TrackParam[i1];
	252	// second extrapolation
	253	(&(TrackParam[i2]))->ExtrapToZ(extZ[1]);
	254	return;
	255	}
	256
04b5ea16	257	//__________________________________________________________________________
	258	void AliMUONTrackParam::ExtrapToVertex()
	259	{
	260	// Extrapolation to the vertex.
	261	// Returns the track parameters resulting from the extrapolation,
	262	// in the current TrackParam.
956019b6	263	// Changes parameters according to Branson correction through the absorber
04b5ea16	264
	265	Double_t zAbsorber = 503.0; // to be coherent with the Geant absorber geometry !!!!
	266	// Extrapolates track parameters upstream to the "Z" end of the front absorber
	267	ExtrapToZ(zAbsorber);
	268	// Makes Branson correction (multiple scattering + energy loss)
	269	BransonCorrection();
	270	}
	271
	272	//__________________________________________________________________________
	273	void AliMUONTrackParam::BransonCorrection()
	274	{
	275	// Branson correction of track parameters
	276	// the entry parameters have to be calculated at the end of the absorber
	277	Double_t zEndAbsorber, zBP, xBP, yBP;
	278	Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
	279	Int_t sign;
	280	// Would it be possible to calculate all that from Geant configuration ????
956019b6	281	// and to get the Branson parameters from a function in ABSO module ????
956019b6	282	// with an eventual contribution from other detectors like START ????
04b5ea16	283	// Radiation lengths outer part theta > 3 degres
	284	static Double_t x01[9] = { 18.8, // C (cm)
	285	10.397, // Concrete (cm)
	286	0.56, // Plomb (cm)
	287	47.26, // Polyethylene (cm)
	288	0.56, // Plomb (cm)
	289	47.26, // Polyethylene (cm)
	290	0.56, // Plomb (cm)
	291	47.26, // Polyethylene (cm)
	292	0.56 }; // Plomb (cm)
	293	// inner part theta < 3 degres
	294	static Double_t x02[3] = { 18.8, // C (cm)
	295	10.397, // Concrete (cm)
	296	0.35 }; // W (cm)
	297	// z positions of the materials inside the absober outer part theta > 3 degres
	298	static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 };
	299	// inner part theta < 3 degres
	300	static Double_t z2[4] = { 90, 315, 467, 503 };
	301	static Bool_t first = kTRUE;
	302	static Double_t zBP1, zBP2, rLimit;
	303	// Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call)
	304	if (first) {
	305	first = kFALSE;
	306	Double_t aNBP = 0.0;
	307	Double_t aDBP = 0.0;
88962f0c	308	Int_t iBound;
	309
	310	for (iBound = 0; iBound < 9; iBound++) {
04b5ea16	311	aNBP = aNBP +
	312	(z1[iBound+1] * z1[iBound+1] * z1[iBound+1] -
	313	z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound];
	314	aDBP = aDBP +
	315	(z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound];
	316	}
	317	zBP1 = (2.0 * aNBP) / (3.0 * aDBP);
	318	aNBP = 0.0;
	319	aDBP = 0.0;
88962f0c	320	for (iBound = 0; iBound < 3; iBound++) {
04b5ea16	321	aNBP = aNBP +
	322	(z2[iBound+1] * z2[iBound+1] * z2[iBound+1] -
	323	z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound];
	324	aDBP = aDBP +
	325	(z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound];
	326	}
	327	zBP2 = (2.0 * aNBP) / (3.0 * aDBP);
	328	rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
	329	}
	330
	331	pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
	332	sign = 1;
	333	if (fInverseBendingMomentum < 0) sign = -1;
	334	pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope));
	335	pX = pZ * fNonBendingSlope;
	336	pY = pZ * fBendingSlope;
	337	pTotal = TMath::Sqrt(pYZ pYZ + pX pX);
	338	xEndAbsorber = fNonBendingCoor;
	339	yEndAbsorber = fBendingCoor;
	340	radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
	341
	342	if (radiusEndAbsorber2 > rLimit*rLimit) {
	343	zEndAbsorber = z1[9];
	344	zBP = zBP1;
	345	} else {
956019b6	346	zEndAbsorber = z2[3];
04b5ea16	347	zBP = zBP2;
	348	}
	349
	350	xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
	351	yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
	352
	353	// new parameters after Branson and energy loss corrections
	354	pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP);
	355	pX = pZ * xBP / zBP;
	356	pY = pZ * yBP / zBP;
	357	fBendingSlope = pY / pZ;
	358	fNonBendingSlope = pX / pZ;
	359
	360	pT = TMath::Sqrt(pX * pX + pY * pY);
	361	theta = TMath::ATan2(pT, pZ);
	362	pTotal =
	363	TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
	364
	365	fInverseBendingMomentum = (sign / pTotal) *
	366	TMath::Sqrt(1.0 +
	367	fBendingSlope * fBendingSlope +
	368	fNonBendingSlope * fNonBendingSlope) /
	369	TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
	370
	371	// vertex position at (0,0,0)
	372	// should be taken from vertex measurement ???
	373	fBendingCoor = 0.0;
	374	fNonBendingCoor = 0;
	375	fZ= 0;
	376	}
	377
	378	//__________________________________________________________________________
	379	Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t rLimit, Double_t pTotal, Double_t theta, Double_t xEndAbsorber, Double_t yEndAbsorber)
	380	{
	381	// Returns the total momentum corrected from energy loss in the front absorber
	382	Double_t deltaP, pTotalCorrected;
	383
	384	Double_t radiusEndAbsorber2 =
	385	xEndAbsorber xEndAbsorber + yEndAbsorber yEndAbsorber;
	386	// Parametrization to be redone according to change of absorber material ????
956019b6	387	// See remark in function BransonCorrection !!!!
04b5ea16	388	// The name is not so good, and there are many arguments !!!!
	389	if (radiusEndAbsorber2 < rLimit * rLimit) {
	390	if (pTotal < 15) {
	391	deltaP = 2.737 + 0.0494 * pTotal - 0.001123 * pTotal * pTotal;
	392	} else {
	393	deltaP = 3.0643 + 0.01346 *pTotal;
	394	}
	395	} else {
	396	if (pTotal < 15) {
	397	deltaP = 2.1380 + 0.0351 * pTotal - 0.000853 * pTotal * pTotal;
	398	} else {
	399	deltaP = 2.407 + 0.00702 * pTotal;
	400	}
	401	}
6372a28d	402	deltaP = 0.88 * deltaP; // !!!! changes in the absorber composition ????
04b5ea16	403	pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
	404	return pTotalCorrected;
	405	}
	406