1 #ifndef ALIMUONTRACKEXTRAP_H
2 #define ALIMUONTRACKEXTRAP_H
3 /* Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
4 * See cxx source for full Copyright notice */
7 // Revision of includes 07/05/2004
10 /// \class AliMUONTrackExtrap
11 /// \brief Track parameters in ALICE dimuon spectrometer
13 //////////////////////////////////////////////////////////////
14 /// Tools for track extrapolation in ALICE dimuon spectrometer
15 //////////////////////////////////////////////////////////////
21 class AliMUONTrackParam;
23 class AliMUONTrackExtrap : public TObject
27 AliMUONTrackExtrap() : TObject(){};
29 virtual ~AliMUONTrackExtrap(){};
31 static void SetField();
33 /// return kTRUE if the field is switched ON
34 static Bool_t IsFieldON() {return fgFieldON;}
36 static Double_t GetImpactParamFromBendingMomentum(Double_t bendingMomentum);
37 static Double_t GetBendingMomentumFromImpactParam(Double_t impactParam);
39 // Linearly extrapolate track parameters and covariances
40 static void LinearExtrapToZ(AliMUONTrackParam* trackParam, Double_t zEnd, Bool_t updatePropagator = kFALSE);
42 // Extrapolate track parameters in magnetic field
43 static void ExtrapToZ(AliMUONTrackParam *trackParam, Double_t zEnd);
45 // Extrapolate track parameters and covariances in magnetic field
46 static void ExtrapToZCov(AliMUONTrackParam* trackParam, Double_t zEnd, Bool_t updatePropagator = kFALSE);
48 // Extrapolate track parameters to vertex, corrected for multiple scattering and energy loss effects
49 // Add branson correction resolution and energy loss fluctuation to parameter covariances
50 static void ExtrapToVertex(AliMUONTrackParam* trackParam,
51 Double_t xVtx, Double_t yVtx, Double_t zVtx,
52 Double_t errXVtx, Double_t errYVtx);
54 // Extrapolate track parameters to vertex, corrected for multiple scattering effects only
55 // Add branson correction resolution to parameter covariances
56 static void ExtrapToVertexWithoutELoss(AliMUONTrackParam* trackParam,
57 Double_t xVtx, Double_t yVtx, Double_t zVtx,
58 Double_t errXVtx, Double_t errYVtx);
60 // Extrapolate track parameters to vertex, corrected for energy loss effects only
61 // Add dispersion due to multiple scattering and energy loss fluctuation to parameter covariances
62 static void ExtrapToVertexWithoutBranson(AliMUONTrackParam* trackParam, Double_t zVtx);
64 // Extrapolate track parameters to vertex without multiple scattering and energy loss corrections
65 // Add dispersion due to multiple scattering to parameter covariances
66 static void ExtrapToVertexUncorrected(AliMUONTrackParam* trackParam, Double_t zVtx);
68 static Double_t TotalMomentumEnergyLoss(AliMUONTrackParam* trackParam, Double_t xVtx, Double_t yVtx, Double_t zVtx);
70 static Double_t GetMCSAngle2(const AliMUONTrackParam& param, Double_t dZ, Double_t x0);
71 static void AddMCSEffect(AliMUONTrackParam *param, Double_t dZ, Double_t x0);
73 static void ExtrapOneStepRungekutta(Double_t charge, Double_t step, Double_t* vect, Double_t* vout);
77 static const Double_t fgkSimpleBPosition; //!< position of the dipole
78 static const Double_t fgkSimpleBLength; //!< length of the dipole
79 static Double_t fgSimpleBValue; //!< magnetic field value at the centre
80 static Bool_t fgFieldON; //!< kTRUE if the field is switched ON
81 static const Bool_t fgkUseHelix; //!< Tell whether to use Helix or not (default is Runge-Kutta)
82 static const Int_t fgkMaxStepNumber; //!< Maximum number of steps for track extrapolation
83 static const Double_t fgkHelixStepLength; //!< Step lenght for track extrapolation (used in Helix)
84 static const Double_t fgkRungeKuttaMaxResidue;//!< Maximal distance (in Z) to destination to stop the track extrapolation (used in Runge-Kutta)
89 AliMUONTrackExtrap(const AliMUONTrackExtrap& trackExtrap);
91 AliMUONTrackExtrap& operator=(const AliMUONTrackExtrap& trackExtrap);
93 static void ExtrapToZHelix(AliMUONTrackParam *trackParam, Double_t Z);
94 static void ExtrapToZRungekutta(AliMUONTrackParam *trackParam, Double_t Z);
96 static void ConvertTrackParamForExtrap(AliMUONTrackParam* trackParam, Double_t forwardBackward, Double_t *v3);
97 static void RecoverTrackParam(Double_t *v3, Double_t Charge, AliMUONTrackParam* trackParam);
99 static void ExtrapToVertex(AliMUONTrackParam* trackParam,
100 Double_t xVtx, Double_t yVtx, Double_t zVtx,
101 Double_t errXVtx, Double_t errYVtx,
102 Bool_t correctForMCS, Bool_t correctForEnergyLoss);
104 static void AddMCSEffectInAbsorber(AliMUONTrackParam* trackParam, Double_t pathLength, Double_t f0, Double_t f1, Double_t f2);
105 static void CorrectMCSEffectInAbsorber(AliMUONTrackParam* param,
106 Double_t xVtx, Double_t yVtx, Double_t zVtx,
107 Double_t errXVtx, Double_t errYVtx,
108 Double_t absZBeg, Double_t pathLength, Double_t f0, Double_t f1, Double_t f2);
109 static void CorrectELossEffectInAbsorber(AliMUONTrackParam* param, Double_t eLoss, Double_t sigmaELoss2);
110 static Bool_t GetAbsorberCorrectionParam(Double_t trackXYZIn[3], Double_t trackXYZOut[3], Double_t pTotal,
111 Double_t &pathLength, Double_t &f0, Double_t &f1, Double_t &f2,
112 Double_t &meanRho, Double_t &totalELoss, Double_t &sigmaELoss2);
114 static Double_t BetheBloch(Double_t pTotal, Double_t pathLength, Double_t rho, Double_t atomicA, Double_t atomicZ);
115 static Double_t EnergyLossFluctuation2(Double_t pTotal, Double_t pathLength, Double_t rho, Double_t atomicA, Double_t atomicZ);
117 static void Cov2CovP(const TMatrixD ¶m, TMatrixD &cov);
118 static void CovP2Cov(const TMatrixD ¶m, TMatrixD &cov);
120 static void ExtrapOneStepHelix(Double_t charge, Double_t step, Double_t *vect, Double_t *vout);
121 static void ExtrapOneStepHelix3(Double_t field, Double_t step, Double_t *vect, Double_t *vout);
123 ClassDef(AliMUONTrackExtrap, 0) // Tools for track extrapolation in ALICE dimuon spectrometer