[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 1.8  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 "AliMUONHitForRec.h" 
#include "AliMUONSegment.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];
  }
}

// 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;
    }
  }
  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	$Log$
6372a28d	18	Revision 1.8 2000/10/02 21:28:09 fca
	19	Removal of useless dependecies via forward declarations
	20
94de3818	21	Revision 1.7 2000/10/02 16:58:29 egangler
	22	Cleaning of the code :
	23	-> coding conventions
	24	-> void Streamers
	25	-> some useless includes removed or replaced by "class" statement
	26
ecfa008b	27	Revision 1.6 2000/09/19 09:49:50 gosset
	28	AliMUONEventReconstructor package
	29	* track extrapolation independent from reco_muon.F, use of AliMagF...
	30	* possibility to use new magnetic field (automatic from generated root file)
	31
a6f03ddb	32	Revision 1.5 2000/07/18 16:04:06 gosset
	33	AliMUONEventReconstructor package:
	34	* a few minor modifications and more comments
	35	* a few corrections
	36	* right sign for Z of raw clusters
	37	* right loop over chambers inside station
	38	* symmetrized covariance matrix for measurements (TrackChi2MCS)
	39	* right sign of charge in extrapolation (ExtrapToZ)
	40	* right zEndAbsorber for Branson correction below 3 degrees
	41	* use of TVirtualFitter instead of TMinuit for AliMUONTrack::Fit
	42	* no parameter for AliMUONTrack::Fit() but more fit parameters in Track object
	43
956019b6	44	Revision 1.4 2000/07/03 07:53:31 morsch
	45	Double declaration problem on HP solved.
	46
88962f0c	47	Revision 1.3 2000/06/30 10:15:48 gosset
	48	Changes to EventReconstructor...:
	49	precision fit with multiple Coulomb scattering;
	50	extrapolation to vertex with Branson correction in absorber (JPC)
	51
04b5ea16	52	Revision 1.2 2000/06/15 07:58:49 morsch
	53	Code from MUON-dev joined
	54
a9e2aefa	55	Revision 1.1.2.3 2000/06/09 21:03:09 morsch
	56	Make includes consistent with new file structure.
	57
	58	Revision 1.1.2.2 2000/06/09 12:58:05 gosset
	59	Removed comment beginnings in Log sections of .cxx files
	60	Suppressed most violations of coding rules
	61
	62	Revision 1.1.2.1 2000/06/07 14:44:53 gosset
	63	Addition of files for track reconstruction in C++
	64	*/
	65
	66	//__________________________________________________________________________
	67	//
	68	// Track parameters in ALICE dimuon spectrometer
	69	//__________________________________________________________________________
	70
	71	#include <iostream.h>
	72
	73	#include "AliCallf77.h"
	74	#include "AliMUON.h"
	75	#include "AliMUONHitForRec.h"
	76	#include "AliMUONSegment.h"
	77	#include "AliMUONTrackParam.h"
	78	#include "AliMUONChamber.h"
	79	#include "AliRun.h"
94de3818	80	#include "AliMagF.h"
a9e2aefa	81
	82	ClassImp(AliMUONTrackParam) // Class implementation in ROOT context
	83
a6f03ddb	84	// A few calls in Fortran or from Fortran (extrap.F).
	85	// Needed, instead of calls to Geant subroutines,
	86	// because double precision is necessary for track fit converging with Minuit.
	87	// The "extrap" functions should be translated into C++ ????
a9e2aefa	88	#ifndef WIN32
a6f03ddb	89	# define extrap_onestep_helix extrap_onestep_helix_
	90	# define extrap_onestep_helix3 extrap_onestep_helix3_
	91	# define extrap_onestep_rungekutta extrap_onestep_rungekutta_
	92	# define gufld_double gufld_double_
a9e2aefa	93	#else
a6f03ddb	94	# define extrap_onestep_helix EXTRAP_ONESTEP_HELIX
	95	# define extrap_onestep_helix3 EXTRAP_ONESTEP_HELIX3
	96	# define extrap_onestep_rungekutta EXTRAP_ONESTEP_RUNGEKUTTA
	97	# define gufld_double GUFLD_DOUBLE
a9e2aefa	98	#endif
a9e2aefa	99
a6f03ddb	100	extern "C" {
	101	void type_of_call extrap_onestep_helix
	102	(Double_t &Charge, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	103
	104	void type_of_call extrap_onestep_helix3
	105	(Double_t &Field, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	106
	107	void type_of_call extrap_onestep_rungekutta
	108	(Double_t &Charge, Double_t &StepLength, Double_t VGeant3, Double_t VGeant3New);
	109
	110	void type_of_call gufld_double(Double_t Position, Double_t Field) {
	111	// interface to "gAlice->Field()->Field" for arguments in double precision
	112	Float_t x[3], b[3];
	113	x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2];
	114	gAlice->Field()->Field(x, b);
	115	Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2];
	116	}
a9e2aefa	117	}
	118
	119	// Inline functions for Get and Set: inline removed because it does not work !!!!
	120	Double_t AliMUONTrackParam::GetInverseBendingMomentum(void) {
	121	// Get fInverseBendingMomentum
	122	return fInverseBendingMomentum;}
	123	void AliMUONTrackParam::SetInverseBendingMomentum(Double_t InverseBendingMomentum) {
	124	// Set fInverseBendingMomentum
	125	fInverseBendingMomentum = InverseBendingMomentum;}
	126	Double_t AliMUONTrackParam::GetBendingSlope(void) {
	127	// Get fBendingSlope
	128	return fBendingSlope;}
	129	void AliMUONTrackParam::SetBendingSlope(Double_t BendingSlope) {
	130	// Set fBendingSlope
	131	fBendingSlope = BendingSlope;}
	132	Double_t AliMUONTrackParam::GetNonBendingSlope(void) {
	133	// Get fNonBendingSlope
	134	return fNonBendingSlope;}
	135	void AliMUONTrackParam::SetNonBendingSlope(Double_t NonBendingSlope) {
	136	// Set fNonBendingSlope
	137	fNonBendingSlope = NonBendingSlope;}
	138	Double_t AliMUONTrackParam::GetZ(void) {
	139	// Get fZ
	140	return fZ;}
	141	void AliMUONTrackParam::SetZ(Double_t Z) {
	142	// Set fZ
	143	fZ = Z;}
	144	Double_t AliMUONTrackParam::GetBendingCoor(void) {
	145	// Get fBendingCoor
	146	return fBendingCoor;}
	147	void AliMUONTrackParam::SetBendingCoor(Double_t BendingCoor) {
	148	// Set fBendingCoor
	149	fBendingCoor = BendingCoor;}
	150	Double_t AliMUONTrackParam::GetNonBendingCoor(void) {
	151	// Get fNonBendingCoor
	152	return fNonBendingCoor;}
	153	void AliMUONTrackParam::SetNonBendingCoor(Double_t NonBendingCoor) {
	154	// Set fNonBendingCoor
	155	fNonBendingCoor = NonBendingCoor;}
	156
	157	//__________________________________________________________________________
	158	void AliMUONTrackParam::ExtrapToZ(Double_t Z)
	159	{
	160	// Track parameter extrapolation to the plane at "Z".
	161	// On return, the track parameters resulting from the extrapolation
	162	// replace the current track parameters.
a9e2aefa	163	if (this->fZ == Z) return; // nothing to be done if same Z
	164	Double_t forwardBackward; // +1 if forward, -1 if backward
	165	if (Z > this->fZ) forwardBackward = 1.0;
	166	else forwardBackward = -1.0;
a6f03ddb	167	Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ????
a9e2aefa	168	Int_t iGeant3, stepNumber;
	169	Int_t maxStepNumber = 5000; // in parameter ????
	170	// For safety: return kTRUE or kFALSE ????
a6f03ddb	171	// Parameter vector for calling EXTRAP_ONESTEP
a9e2aefa	172	SetGeant3Parameters(vGeant3, forwardBackward);
956019b6	173	// sign of charge (sign of fInverseBendingMomentum if forward motion)
a6f03ddb	174	// must be changed if backward extrapolation
956019b6	175	Double_t chargeExtrap = forwardBackward *
956019b6	176	TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum);
a9e2aefa	177	Double_t stepLength = 6.0; // in parameter ????
	178	// Extrapolation loop
	179	stepNumber = 0;
	180	while (((forwardBackward * (vGeant3[2] - Z)) <= 0.0) &&
	181	(stepNumber < maxStepNumber)) {
	182	stepNumber++;
a6f03ddb	183	// Option for switching between helix and Runge-Kutta ????
	184	// extrap_onestep_rungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New);
	185	extrap_onestep_helix(chargeExtrap, stepLength, vGeant3, vGeant3New);
a9e2aefa	186	if ((forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z
	187	// better use TArray ????
	188	for (iGeant3 = 0; iGeant3 < 7; iGeant3++)
	189	{vGeant3[iGeant3] = vGeant3New[iGeant3];}
	190	}
	191	// check maxStepNumber ????
a9e2aefa	192	// Interpolation back to exact Z (2nd order)
	193	// should be in function ???? using TArray ????
	194	Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2
	195	Double_t dZ1i = Z - vGeant3[2]; // 1-i
	196	Double_t dZi2 = vGeant3New[2] - Z; // i->2
	197	Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12;
	198	Double_t xSecond =
	199	((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12;
	200	Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12;
	201	Double_t ySecond =
	202	((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12;
	203	vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X
	204	vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y
	205	vGeant3[2] = Z; // Z
	206	Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i);
	207	Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i);
956019b6	208	// (PX, PY, PZ)/PTOT assuming forward motion
a9e2aefa	209	vGeant3[5] =
	210	1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT
	211	vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT
	212	vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT
956019b6	213	// Track parameters from Geant3 parameters,
	214	// with charge back for forward motion
	215	GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward);
a9e2aefa	216	}
	217
	218	//__________________________________________________________________________
	219	void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward)
	220	{
	221	// Set vector of Geant3 parameters pointed to by "VGeant3"
	222	// from track parameters in current AliMUONTrackParam.
	223	// Since AliMUONTrackParam is only geometry, one uses "ForwardBackward"
	224	// to know whether the particle is going forward (+1) or backward (-1).
	225	VGeant3[0] = this->fNonBendingCoor; // X
	226	VGeant3[1] = this->fBendingCoor; // Y
	227	VGeant3[2] = this->fZ; // Z
	228	Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum);
	229	Double_t pZ =
	230	pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope);
	231	VGeant3[6] =
	232	TMath::Sqrt(pYZ * pYZ +
	233	pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT
	234	VGeant3[5] = ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT
	235	VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT
	236	VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT
	237	}
	238
	239	//__________________________________________________________________________
	240	void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge)
	241	{
	242	// Get track parameters in current AliMUONTrackParam
956019b6	243	// from Geant3 parameters pointed to by "VGeant3",
956019b6	244	// assumed to be calculated for forward motion in Z.
a9e2aefa	245	// "InverseBendingMomentum" is signed with "Charge".
	246	this->fNonBendingCoor = VGeant3[0]; // X
	247	this->fBendingCoor = VGeant3[1]; // Y
	248	this->fZ = VGeant3[2]; // Z
	249	Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]);
	250	this->fInverseBendingMomentum = Charge / pYZ;
	251	this->fBendingSlope = VGeant3[4] / VGeant3[5];
	252	this->fNonBendingSlope = VGeant3[3] / VGeant3[5];
	253	}
	254
	255	//__________________________________________________________________________
	256	void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam)
	257	{
	258	// Track parameters extrapolated from current track parameters ("this")
	259	// to both chambers of the station(0..) "Station"
	260	// are returned in the array (dimension 2) of track parameters
	261	// pointed to by "TrackParam" (index 0 and 1 for first and second chambers).
	262	Double_t extZ[2], z1, z2;
ecfa008b	263	Int_t i1 = -1, i2 = -1; // = -1 to avoid compilation warnings
a9e2aefa	264	AliMUON pMUON = (AliMUON) gAlice->GetModule("MUON"); // necessary ????
	265	// range of Station to be checked ????
	266	z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber
	267	z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber
	268	// First and second Z to extrapolate at
	269	if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;}
	270	else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;}
	271	else {
	272	cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl;
	273	cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 <<
	274	") and z2 (" << z2 << ") of station(0..) " << Station << endl;
	275	}
	276	extZ[i1] = z1;
	277	extZ[i2] = z2;
	278	// copy of track parameters
	279	TrackParam[i1] = *this;
	280	// first extrapolation
	281	(&(TrackParam[i1]))->ExtrapToZ(extZ[0]);
	282	TrackParam[i2] = TrackParam[i1];
	283	// second extrapolation
	284	(&(TrackParam[i2]))->ExtrapToZ(extZ[1]);
	285	return;
	286	}
	287
04b5ea16	288	//__________________________________________________________________________
	289	void AliMUONTrackParam::ExtrapToVertex()
	290	{
	291	// Extrapolation to the vertex.
	292	// Returns the track parameters resulting from the extrapolation,
	293	// in the current TrackParam.
956019b6	294	// Changes parameters according to Branson correction through the absorber
04b5ea16	295
	296	Double_t zAbsorber = 503.0; // to be coherent with the Geant absorber geometry !!!!
	297	// Extrapolates track parameters upstream to the "Z" end of the front absorber
	298	ExtrapToZ(zAbsorber);
	299	// Makes Branson correction (multiple scattering + energy loss)
	300	BransonCorrection();
	301	}
	302
	303	//__________________________________________________________________________
	304	void AliMUONTrackParam::BransonCorrection()
	305	{
	306	// Branson correction of track parameters
	307	// the entry parameters have to be calculated at the end of the absorber
	308	Double_t zEndAbsorber, zBP, xBP, yBP;
	309	Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
	310	Int_t sign;
	311	// Would it be possible to calculate all that from Geant configuration ????
956019b6	312	// and to get the Branson parameters from a function in ABSO module ????
956019b6	313	// with an eventual contribution from other detectors like START ????
04b5ea16	314	// Radiation lengths outer part theta > 3 degres
	315	static Double_t x01[9] = { 18.8, // C (cm)
	316	10.397, // Concrete (cm)
	317	0.56, // Plomb (cm)
	318	47.26, // Polyethylene (cm)
	319	0.56, // Plomb (cm)
	320	47.26, // Polyethylene (cm)
	321	0.56, // Plomb (cm)
	322	47.26, // Polyethylene (cm)
	323	0.56 }; // Plomb (cm)
	324	// inner part theta < 3 degres
	325	static Double_t x02[3] = { 18.8, // C (cm)
	326	10.397, // Concrete (cm)
	327	0.35 }; // W (cm)
	328	// z positions of the materials inside the absober outer part theta > 3 degres
	329	static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 };
	330	// inner part theta < 3 degres
	331	static Double_t z2[4] = { 90, 315, 467, 503 };
	332	static Bool_t first = kTRUE;
	333	static Double_t zBP1, zBP2, rLimit;
	334	// Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call)
	335	if (first) {
	336	first = kFALSE;
	337	Double_t aNBP = 0.0;
	338	Double_t aDBP = 0.0;
88962f0c	339	Int_t iBound;
	340
	341	for (iBound = 0; iBound < 9; iBound++) {
04b5ea16	342	aNBP = aNBP +
	343	(z1[iBound+1] * z1[iBound+1] * z1[iBound+1] -
	344	z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound];
	345	aDBP = aDBP +
	346	(z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound];
	347	}
	348	zBP1 = (2.0 * aNBP) / (3.0 * aDBP);
	349	aNBP = 0.0;
	350	aDBP = 0.0;
88962f0c	351	for (iBound = 0; iBound < 3; iBound++) {
04b5ea16	352	aNBP = aNBP +
	353	(z2[iBound+1] * z2[iBound+1] * z2[iBound+1] -
	354	z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound];
	355	aDBP = aDBP +
	356	(z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound];
	357	}
	358	zBP2 = (2.0 * aNBP) / (3.0 * aDBP);
	359	rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
	360	}
	361
	362	pYZ = TMath::Abs(1.0 / fInverseBendingMomentum);
	363	sign = 1;
	364	if (fInverseBendingMomentum < 0) sign = -1;
	365	pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope));
	366	pX = pZ * fNonBendingSlope;
	367	pY = pZ * fBendingSlope;
	368	pTotal = TMath::Sqrt(pYZ pYZ + pX pX);
	369	xEndAbsorber = fNonBendingCoor;
	370	yEndAbsorber = fBendingCoor;
	371	radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
	372
	373	if (radiusEndAbsorber2 > rLimit*rLimit) {
	374	zEndAbsorber = z1[9];
	375	zBP = zBP1;
	376	} else {
956019b6	377	zEndAbsorber = z2[3];
04b5ea16	378	zBP = zBP2;
	379	}
	380
	381	xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP);
	382	yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP);
	383
	384	// new parameters after Branson and energy loss corrections
	385	pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP);
	386	pX = pZ * xBP / zBP;
	387	pY = pZ * yBP / zBP;
	388	fBendingSlope = pY / pZ;
	389	fNonBendingSlope = pX / pZ;
	390
	391	pT = TMath::Sqrt(pX * pX + pY * pY);
	392	theta = TMath::ATan2(pT, pZ);
	393	pTotal =
	394	TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
	395
	396	fInverseBendingMomentum = (sign / pTotal) *
	397	TMath::Sqrt(1.0 +
	398	fBendingSlope * fBendingSlope +
	399	fNonBendingSlope * fNonBendingSlope) /
	400	TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope);
	401
	402	// vertex position at (0,0,0)
	403	// should be taken from vertex measurement ???
	404	fBendingCoor = 0.0;
	405	fNonBendingCoor = 0;
	406	fZ= 0;
	407	}
	408
	409	//__________________________________________________________________________
	410	Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t rLimit, Double_t pTotal, Double_t theta, Double_t xEndAbsorber, Double_t yEndAbsorber)
	411	{
	412	// Returns the total momentum corrected from energy loss in the front absorber
	413	Double_t deltaP, pTotalCorrected;
	414
	415	Double_t radiusEndAbsorber2 =
	416	xEndAbsorber xEndAbsorber + yEndAbsorber yEndAbsorber;
	417	// Parametrization to be redone according to change of absorber material ????
956019b6	418	// See remark in function BransonCorrection !!!!
04b5ea16	419	// The name is not so good, and there are many arguments !!!!
	420	if (radiusEndAbsorber2 < rLimit * rLimit) {
	421	if (pTotal < 15) {
	422	deltaP = 2.737 + 0.0494 * pTotal - 0.001123 * pTotal * pTotal;
	423	} else {
	424	deltaP = 3.0643 + 0.01346 *pTotal;
	425	}
	426	} else {
	427	if (pTotal < 15) {
	428	deltaP = 2.1380 + 0.0351 * pTotal - 0.000853 * pTotal * pTotal;
	429	} else {
	430	deltaP = 2.407 + 0.00702 * pTotal;
	431	}
	432	}
6372a28d	433	deltaP = 0.88 * deltaP; // !!!! changes in the absorber composition ????
04b5ea16	434	pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
	435	return pTotalCorrected;
	436	}
	437