/* $Id$ */
-///////////////////////////////////////////////////
-//
-// Tools
-// for
-// track
-// extrapolation
-// in
-// ALICE
-// dimuon
-// spectrometer
-//
-///////////////////////////////////////////////////
-
-#include <Riostream.h>
-#include <TMath.h>
-#include <TMatrixD.h>
+//-----------------------------------------------------------------------------
+// Class AliMUONTrackExtrap
+// ------------------------
+// Tools for track extrapolation in ALICE dimuon spectrometer
+// Author: Philippe Pillot
+//-----------------------------------------------------------------------------
#include "AliMUONTrackExtrap.h"
#include "AliMUONTrackParam.h"
#include "AliMUONConstants.h"
+#include "AliMUONReconstructor.h"
+
#include "AliMagF.h"
-#include "AliLog.h"
-#include "AliTracker.h"
+#include <TGeoGlobalMagField.h>
+#include <TGeoManager.h>
+#include <TMath.h>
+
+#include <Riostream.h>
+
+/// \cond CLASSIMP
ClassImp(AliMUONTrackExtrap) // Class implementation in ROOT context
+/// \endcond
-const AliMagF* AliMUONTrackExtrap::fgkField = 0x0;
+const Double_t AliMUONTrackExtrap::fgkSimpleBPosition = 0.5 * (AliMUONConstants::CoilZ() + AliMUONConstants::YokeZ());
+const Double_t AliMUONTrackExtrap::fgkSimpleBLength = 0.5 * (AliMUONConstants::CoilL() + AliMUONConstants::YokeL());
+ Double_t AliMUONTrackExtrap::fgSimpleBValue = 0.;
+ Bool_t AliMUONTrackExtrap::fgFieldON = kFALSE;
const Bool_t AliMUONTrackExtrap::fgkUseHelix = kFALSE;
const Int_t AliMUONTrackExtrap::fgkMaxStepNumber = 5000;
const Double_t AliMUONTrackExtrap::fgkHelixStepLength = 6.;
const Double_t AliMUONTrackExtrap::fgkRungeKuttaMaxResidue = 0.002;
- //__________________________________________________________________________
+//__________________________________________________________________________
+void AliMUONTrackExtrap::SetField()
+{
+ // set field on/off flag
+ // set field at the centre of the dipole
+ const Double_t x[3] = {50.,50.,fgkSimpleBPosition};
+ Double_t b[3] = {0.,0.,0.};
+ TGeoGlobalMagField::Instance()->Field(x,b);
+ fgSimpleBValue = b[0];
+ fgFieldON = fgSimpleBValue ? kTRUE : kFALSE;
+
+}
+
+//__________________________________________________________________________
Double_t AliMUONTrackExtrap::GetImpactParamFromBendingMomentum(Double_t bendingMomentum)
{
/// Returns impact parameter at vertex in bending plane (cm),
if (bendingMomentum == 0.) return 1.e10;
- Double_t simpleBPosition = 0.5 * (AliMUONConstants::CoilZ() + AliMUONConstants::YokeZ());
- Double_t simpleBLength = 0.5 * (AliMUONConstants::CoilL() + AliMUONConstants::YokeL());
- Float_t b[3], x[3] = {0.,0.,(Float_t) simpleBPosition};
- if (fgkField) fgkField->Field(x,b);
- else {
- cout<<"F-AliMUONTrackExtrap::GetField: fgkField = 0x0"<<endl;
- exit(-1);
- }
- Double_t simpleBValue = (Double_t) b[0];
+ const Double_t kCorrectionFactor = 0.9; // impact parameter is 10% overestimated
- return (-0.0003 * simpleBValue * simpleBLength * simpleBPosition / bendingMomentum);
+ return kCorrectionFactor * (-0.0003 * fgSimpleBValue * fgkSimpleBLength * fgkSimpleBPosition / bendingMomentum);
}
- //__________________________________________________________________________
-Double_t AliMUONTrackExtrap::GetBendingMomentumFromImpactParam(Double_t impactParam)
+//__________________________________________________________________________
+Double_t
+AliMUONTrackExtrap::GetBendingMomentumFromImpactParam(Double_t impactParam)
{
/// Returns signed bending momentum in bending plane (GeV/c),
/// the sign being the sign of the charge for particles moving forward in Z,
if (impactParam == 0.) return 1.e10;
- Double_t simpleBPosition = 0.5 * (AliMUONConstants::CoilZ() + AliMUONConstants::YokeZ());
- Double_t simpleBLength = 0.5 * (AliMUONConstants::CoilL() + AliMUONConstants::YokeL());
- Float_t b[3], x[3] = {0.,0.,(Float_t) simpleBPosition};
- if (fgkField) fgkField->Field(x,b);
- else {
- cout<<"F-AliMUONTrackExtrap::GetField: fgkField = 0x0"<<endl;
- exit(-1);
+ const Double_t kCorrectionFactor = 1.1; // bending momentum is 10% underestimated
+
+ if (fgFieldON)
+ {
+ return kCorrectionFactor * (-0.0003 * fgSimpleBValue * fgkSimpleBLength * fgkSimpleBPosition / impactParam);
+ }
+ else
+ {
+ return AliMUONConstants::GetMostProbBendingMomentum();
+ }
+}
+
+//__________________________________________________________________________
+void AliMUONTrackExtrap::LinearExtrapToZ(AliMUONTrackParam* trackParam, Double_t zEnd, Bool_t updatePropagator)
+{
+ /// Track parameters (and their covariances if any) linearly extrapolated to the plane at "zEnd".
+ /// On return, results from the extrapolation are updated in trackParam.
+
+ if (trackParam->GetZ() == zEnd) return; // nothing to be done if same z
+
+ // Compute track parameters
+ Double_t dZ = zEnd - trackParam->GetZ();
+ trackParam->SetNonBendingCoor(trackParam->GetNonBendingCoor() + trackParam->GetNonBendingSlope() * dZ);
+ trackParam->SetBendingCoor(trackParam->GetBendingCoor() + trackParam->GetBendingSlope() * dZ);
+ trackParam->SetZ(zEnd);
+
+ // Update track parameters covariances if any
+ if (trackParam->CovariancesExist()) {
+ TMatrixD paramCov(trackParam->GetCovariances());
+ paramCov(0,0) += dZ * dZ * paramCov(1,1) + 2. * dZ * paramCov(0,1);
+ paramCov(0,1) += dZ * paramCov(1,1);
+ paramCov(1,0) = paramCov(0,1);
+ paramCov(2,2) += dZ * dZ * paramCov(3,3) + 2. * dZ * paramCov(2,3);
+ paramCov(2,3) += dZ * paramCov(3,3);
+ paramCov(3,2) = paramCov(2,3);
+ trackParam->SetCovariances(paramCov);
+
+ // Update the propagator if required
+ if (updatePropagator) {
+ TMatrixD jacob(5,5);
+ jacob.UnitMatrix();
+ jacob(0,1) = dZ;
+ jacob(2,3) = dZ;
+ trackParam->UpdatePropagator(jacob);
+ }
+
}
- Double_t simpleBValue = (Double_t) b[0];
- return (-0.0003 * simpleBValue * simpleBLength * simpleBPosition / impactParam);
}
- //__________________________________________________________________________
+//__________________________________________________________________________
void AliMUONTrackExtrap::ExtrapToZ(AliMUONTrackParam* trackParam, Double_t zEnd)
{
/// Interface to track parameter extrapolation to the plane at "Z" using Helix or Rungekutta algorithm.
/// On return, the track parameters resulting from the extrapolation are updated in trackParam.
- if (fgkUseHelix) AliMUONTrackExtrap::ExtrapToZHelix(trackParam,zEnd);
+ if (!fgFieldON) AliMUONTrackExtrap::LinearExtrapToZ(trackParam,zEnd);
+ else if (fgkUseHelix) AliMUONTrackExtrap::ExtrapToZHelix(trackParam,zEnd);
else AliMUONTrackExtrap::ExtrapToZRungekutta(trackParam,zEnd);
}
- //__________________________________________________________________________
+//__________________________________________________________________________
void AliMUONTrackExtrap::ExtrapToZHelix(AliMUONTrackParam* trackParam, Double_t zEnd)
{
/// Track parameter extrapolation to the plane at "Z" using Helix algorithm.
stepNumber++;
ExtrapOneStepHelix(chargeExtrap, fgkHelixStepLength, v3, v3New);
if ((-forwardBackward * (v3New[2] - zEnd)) > 0.0) break; // one is beyond Z spectro. z<0
- // better use TArray ????
+ // better use TArray ????
for (i3 = 0; i3 < 7; i3++) {v3[i3] = v3New[i3];}
}
// check fgkMaxStepNumber ????
RecoverTrackParam(v3, chargeExtrap * forwardBackward, trackParam);
}
- //__________________________________________________________________________
+//__________________________________________________________________________
void AliMUONTrackExtrap::ExtrapToZRungekutta(AliMUONTrackParam* trackParam, Double_t zEnd)
{
/// Track parameter extrapolation to the plane at "Z" using Rungekutta algorithm.
dZ = zEnd - trackParam->GetZ();
// step lenght assuming linear trajectory
step = dZ * TMath::Sqrt(1.0 + trackParam->GetBendingSlope()*trackParam->GetBendingSlope() +
- trackParam->GetNonBendingSlope()*trackParam->GetNonBendingSlope());
+ trackParam->GetNonBendingSlope()*trackParam->GetNonBendingSlope());
ConvertTrackParamForExtrap(trackParam, forwardBackward, v3);
do { // reduce step lenght while zEnd oversteped
if (stepNumber > fgkMaxStepNumber) {
trackParam->SetZ(zEnd);
}
- //__________________________________________________________________________
+//__________________________________________________________________________
void AliMUONTrackExtrap::ConvertTrackParamForExtrap(AliMUONTrackParam* trackParam, Double_t forwardBackward, Double_t *v3)
{
/// Set vector of Geant3 parameters pointed to by "v3" from track parameters in trackParam.
v3[4] = trackParam->GetBendingSlope() * v3[5]; // PY/PTOT
}
- //__________________________________________________________________________
+//__________________________________________________________________________
void AliMUONTrackExtrap::RecoverTrackParam(Double_t *v3, Double_t charge, AliMUONTrackParam* trackParam)
{
/// Set track parameters in trackParam from Geant3 parameters pointed to by "v3",
trackParam->SetNonBendingCoor(v3[0]); // X
trackParam->SetBendingCoor(v3[1]); // Y
trackParam->SetZ(v3[2]); // Z
- Double_t pYZ = v3[6] * TMath::Sqrt(1.0 - v3[3] * v3[3]);
+ Double_t pYZ = v3[6] * TMath::Sqrt((1.-v3[3])*(1.+v3[3]));
trackParam->SetInverseBendingMomentum(charge/pYZ);
trackParam->SetBendingSlope(v3[4]/v3[5]);
trackParam->SetNonBendingSlope(v3[3]/v3[5]);
}
- //__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapToZCov(AliMUONTrackParam* trackParam, Double_t zEnd)
+//__________________________________________________________________________
+void AliMUONTrackExtrap::ExtrapToZCov(AliMUONTrackParam* trackParam, Double_t zEnd, Bool_t updatePropagator)
{
/// Track parameters and their covariances extrapolated to the plane at "zEnd".
/// On return, results from the extrapolation are updated in trackParam.
if (trackParam->GetZ() == zEnd) return; // nothing to be done if same z
+ if (!fgFieldON) { // linear extrapolation if no magnetic field
+ AliMUONTrackExtrap::LinearExtrapToZ(trackParam,zEnd,updatePropagator);
+ return;
+ }
+
+ // No need to propagate the covariance matrix if it does not exist
+ if (!trackParam->CovariancesExist()) {
+ cout<<"W-AliMUONTrackExtrap::ExtrapToZCov: Covariance matrix does not exist"<<endl;
+ // Extrapolate track parameters to "zEnd"
+ ExtrapToZ(trackParam,zEnd);
+ return;
+ }
+
// Save the actual track parameters
AliMUONTrackParam trackParamSave(*trackParam);
- Double_t nonBendingCoor = trackParamSave.GetNonBendingCoor();
- Double_t nonBendingSlope = trackParamSave.GetNonBendingSlope();
- Double_t bendingCoor = trackParamSave.GetBendingCoor();
- Double_t bendingSlope = trackParamSave.GetBendingSlope();
- Double_t inverseBendingMomentum = trackParamSave.GetInverseBendingMomentum();
- Double_t zBegin = trackParamSave.GetZ();
+ TMatrixD paramSave(trackParamSave.GetParameters());
+ Double_t zBegin = trackParamSave.GetZ();
+ // Get reference to the parameter covariance matrix
+ const TMatrixD& kParamCov = trackParam->GetCovariances();
+
// Extrapolate track parameters to "zEnd"
ExtrapToZ(trackParam,zEnd);
- Double_t extrapNonBendingCoor = trackParam->GetNonBendingCoor();
- Double_t extrapNonBendingSlope = trackParam->GetNonBendingSlope();
- Double_t extrapBendingCoor = trackParam->GetBendingCoor();
- Double_t extrapBendingSlope = trackParam->GetBendingSlope();
- Double_t extrapInverseBendingMomentum = trackParam->GetInverseBendingMomentum();
- // Get the pointer to the parameter covariance matrix
- if (!trackParam->CovariancesExist()) {
- //cout<<"W-AliMUONTrackExtrap::ExtrapToZCov: track parameter covariance matrix does not exist"<<endl;
- //cout<<" -> nothing to extrapolate !!"<<endl;
- return;
- }
- TMatrixD* paramCov = trackParam->GetCovariances();
+ // Get reference to the extrapolated parameters
+ const TMatrixD& extrapParam = trackParam->GetParameters();
// Calculate the jacobian related to the track parameters extrapolation to "zEnd"
TMatrixD jacob(5,5);
- jacob = 0.;
- Double_t dParam[5];
+ jacob.Zero();
+ TMatrixD dParam(5,1);
for (Int_t i=0; i<5; i++) {
// Skip jacobian calculation for parameters with no associated error
- if ((*paramCov)(i,i) == 0.) continue;
+ if (kParamCov(i,i) <= 0.) continue;
+
// Small variation of parameter i only
for (Int_t j=0; j<5; j++) {
if (j==i) {
- dParam[j] = TMath::Sqrt((*paramCov)(i,i));
- if (j == 4) dParam[j] *= TMath::Sign(1.,-inverseBendingMomentum); // variation always in the same direction
- } else dParam[j] = 0.;
+ dParam(j,0) = TMath::Sqrt(kParamCov(i,i));
+ if (j == 4) dParam(j,0) *= TMath::Sign(1.,-paramSave(4,0)); // variation always in the same direction
+ } else dParam(j,0) = 0.;
}
+
// Set new parameters
- trackParamSave.SetNonBendingCoor (nonBendingCoor + dParam[0]);
- trackParamSave.SetNonBendingSlope (nonBendingSlope + dParam[1]);
- trackParamSave.SetBendingCoor (bendingCoor + dParam[2]);
- trackParamSave.SetBendingSlope (bendingSlope + dParam[3]);
- trackParamSave.SetInverseBendingMomentum(inverseBendingMomentum + dParam[4]);
- trackParamSave.SetZ (zBegin);
+ trackParamSave.SetParameters(paramSave);
+ trackParamSave.AddParameters(dParam);
+ trackParamSave.SetZ(zBegin);
+
// Extrapolate new track parameters to "zEnd"
ExtrapToZ(&trackParamSave,zEnd);
+
// Calculate the jacobian
- jacob(0,i) = (trackParamSave.GetNonBendingCoor() - extrapNonBendingCoor ) / dParam[i];
- jacob(1,i) = (trackParamSave.GetNonBendingSlope() - extrapNonBendingSlope ) / dParam[i];
- jacob(2,i) = (trackParamSave.GetBendingCoor() - extrapBendingCoor ) / dParam[i];
- jacob(3,i) = (trackParamSave.GetBendingSlope() - extrapBendingSlope ) / dParam[i];
- jacob(4,i) = (trackParamSave.GetInverseBendingMomentum() - extrapInverseBendingMomentum) / dParam[i];
+ TMatrixD jacobji(trackParamSave.GetParameters(),TMatrixD::kMinus,extrapParam);
+ jacobji *= 1. / dParam(i,0);
+ jacob.SetSub(0,i,jacobji);
}
// Extrapolate track parameter covariances to "zEnd"
- TMatrixD tmp((*paramCov),TMatrixD::kMultTranspose,jacob);
- (*paramCov) = TMatrixD(jacob,TMatrixD::kMult,tmp);
+ TMatrixD tmp(kParamCov,TMatrixD::kMultTranspose,jacob);
+ TMatrixD tmp2(jacob,TMatrixD::kMult,tmp);
+ trackParam->SetCovariances(tmp2);
+ // Update the propagator if required
+ if (updatePropagator) trackParam->UpdatePropagator(jacob);
}
- //__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapToStation(AliMUONTrackParam* trackParamIn, Int_t station, AliMUONTrackParam *trackParamOut)
+//__________________________________________________________________________
+void AliMUONTrackExtrap::AddMCSEffectInAbsorber(AliMUONTrackParam* param, Double_t pathLength, Double_t f0, Double_t f1, Double_t f2)
{
- /// Track parameters extrapolated from "trackParamIn" to both chambers of the station(0..) "station"
- /// are returned in the array (dimension 2) of track parameters pointed to by "TrackParamOut"
- /// (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
- // range of station to be checked ????
- z1 = AliMUONConstants::DefaultChamberZ(2 * station);
- z2 = AliMUONConstants::DefaultChamberZ(2 * station + 1);
- // First and second Z to extrapolate at
- if ((z1 > trackParamIn->GetZ()) && (z2 > trackParamIn->GetZ())) {i1 = 0; i2 = 1;}
- else if ((z1 < trackParamIn->GetZ()) && (z2 < trackParamIn->GetZ())) {i1 = 1; i2 = 0;}
- else {
- cout<<"E-AliMUONTrackExtrap::ExtrapToStation: Starting Z ("<<trackParamIn->GetZ()
- <<") in between z1 ("<<z1<<") and z2 ("<<z2<<") of station(0..)"<<station<<endl;
- exit(-1);
- }
- extZ[i1] = z1;
- extZ[i2] = z2;
- // copy of track parameters
- trackParamOut[i1] = *trackParamIn;
- // first extrapolation
- ExtrapToZ(&(trackParamOut[i1]),extZ[0]);
- trackParamOut[i2] = trackParamOut[i1];
- // second extrapolation
- ExtrapToZ(&(trackParamOut[i2]),extZ[1]);
- return;
+ /// Add to the track parameter covariances the effects of multiple Coulomb scattering
+ /// The absorber correction parameters are supposed to be calculated at the current track z-position
+
+ // absorber related covariance parameters
+ Double_t bendingSlope = param->GetBendingSlope();
+ Double_t nonBendingSlope = param->GetNonBendingSlope();
+ Double_t inverseBendingMomentum = param->GetInverseBendingMomentum();
+ Double_t alpha2 = 0.0136 * 0.0136 * inverseBendingMomentum * inverseBendingMomentum * (1.0 + bendingSlope * bendingSlope) /
+ (1.0 + bendingSlope *bendingSlope + nonBendingSlope * nonBendingSlope); // velocity = 1
+ Double_t varCoor = alpha2 * (pathLength * pathLength * f0 - 2. * pathLength * f1 + f2);
+ Double_t covCorrSlope = alpha2 * (pathLength * f0 - f1);
+ Double_t varSlop = alpha2 * f0;
+
+ // compute derivative d(q/Pxy) / dSlopeX and d(q/Pxy) / dSlopeX
+ Double_t dqPxydSlopeX = inverseBendingMomentum * nonBendingSlope / (1. + nonBendingSlope*nonBendingSlope + bendingSlope*bendingSlope);
+ Double_t dqPxydSlopeY = - inverseBendingMomentum * nonBendingSlope*nonBendingSlope * bendingSlope /
+ (1. + bendingSlope*bendingSlope) / (1. + nonBendingSlope*nonBendingSlope + bendingSlope*bendingSlope);
+
+ // Set MCS covariance matrix
+ TMatrixD newParamCov(param->GetCovariances());
+ // Non bending plane
+ newParamCov(0,0) += varCoor; newParamCov(0,1) += covCorrSlope;
+ newParamCov(1,0) += covCorrSlope; newParamCov(1,1) += varSlop;
+ // Bending plane
+ newParamCov(2,2) += varCoor; newParamCov(2,3) += covCorrSlope;
+ newParamCov(3,2) += covCorrSlope; newParamCov(3,3) += varSlop;
+ // Inverse bending momentum (due to dependences with bending and non bending slopes)
+ newParamCov(4,0) += dqPxydSlopeX * covCorrSlope; newParamCov(0,4) += dqPxydSlopeX * covCorrSlope;
+ newParamCov(4,1) += dqPxydSlopeX * varSlop; newParamCov(1,4) += dqPxydSlopeX * varSlop;
+ newParamCov(4,2) += dqPxydSlopeY * covCorrSlope; newParamCov(2,4) += dqPxydSlopeY * covCorrSlope;
+ newParamCov(4,3) += dqPxydSlopeY * varSlop; newParamCov(3,4) += dqPxydSlopeY * varSlop;
+ newParamCov(4,4) += (dqPxydSlopeX*dqPxydSlopeX + dqPxydSlopeY*dqPxydSlopeY) * varSlop;
+
+ // Set new covariances
+ param->SetCovariances(newParamCov);
}
- //__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapToVertexUncorrected(AliMUONTrackParam* trackParam, Double_t zVtx)
+//__________________________________________________________________________
+void AliMUONTrackExtrap::CorrectMCSEffectInAbsorber(AliMUONTrackParam* param,
+ Double_t xVtx, Double_t yVtx, Double_t zVtx,
+ Double_t errXVtx, Double_t errYVtx,
+ Double_t absZBeg, Double_t pathLength, Double_t f0, Double_t f1, Double_t f2)
{
- /// Extrapolation to the vertex (at the z position "zVtx") without Branson and Field correction.
- /// Returns the track parameters resulting from the extrapolation in the current TrackParam.
- /// Include multiple Coulomb scattering effects in trackParam covariances.
+ /// Correct parameters and corresponding covariances using Branson correction
+ /// - input param are parameters and covariances at the end of absorber
+ /// - output param are parameters and covariances at vertex
+ /// Absorber correction parameters are supposed to be calculated at the current track z-position
- if (trackParam->GetZ() > zVtx) { // spectro. (z<0)
- cout<<"W-AliMUONTrackExtrap::ExtrapToVertexUncorrected: Starting Z ("<<trackParam->GetZ()
- <<") upstream the vertex (zVtx = "<<zVtx<<")"<<endl;
- exit(-1);
- }
+ // Position of the Branson plane (spectro. (z<0))
+ Double_t zB = (f1>0.) ? absZBeg - f2/f1 : 0.;
- if (zVtx < AliMUONConstants::ZAbsorberEnd()) { // spectro. (z<0)
- cout<<"W-AliMUONTrackExtrap::ExtrapToVertexUncorrected: Ending Z ("<<zVtx
- <<") downstream the front absorber (zAbsorberEnd = "<<AliMUONConstants::ZAbsorberEnd()<<")"<<endl;
-
- ExtrapToZCov(trackParam,zVtx);
- return;
+ // Add MCS effects to current parameter covariances
+ AddMCSEffectInAbsorber(param, pathLength, f0, f1, f2);
+
+ // Get track parameters and covariances in the Branson plane corrected for magnetic field effect
+ ExtrapToZCov(param,zVtx);
+ LinearExtrapToZ(param,zB);
+
+ // compute track parameters at vertex
+ TMatrixD newParam(5,1);
+ newParam(0,0) = xVtx;
+ newParam(1,0) = (param->GetNonBendingCoor() - xVtx) / (zB - zVtx);
+ newParam(2,0) = yVtx;
+ newParam(3,0) = (param->GetBendingCoor() - yVtx) / (zB - zVtx);
+ newParam(4,0) = param->GetCharge() / param->P() *
+ TMath::Sqrt(1.0 + newParam(1,0)*newParam(1,0) + newParam(3,0)*newParam(3,0)) /
+ TMath::Sqrt(1.0 + newParam(3,0)*newParam(3,0));
+
+ // Get covariances in (X, SlopeX, Y, SlopeY, q*PTot) coordinate system
+ TMatrixD paramCovP(param->GetCovariances());
+ Cov2CovP(param->GetParameters(),paramCovP);
+
+ // Get the covariance matrix in the (XVtx, X, YVtx, Y, q*PTot) coordinate system
+ TMatrixD paramCovVtx(5,5);
+ paramCovVtx.Zero();
+ paramCovVtx(0,0) = errXVtx * errXVtx;
+ paramCovVtx(1,1) = paramCovP(0,0);
+ paramCovVtx(2,2) = errYVtx * errYVtx;
+ paramCovVtx(3,3) = paramCovP(2,2);
+ paramCovVtx(4,4) = paramCovP(4,4);
+ paramCovVtx(1,3) = paramCovP(0,2);
+ paramCovVtx(3,1) = paramCovP(2,0);
+ paramCovVtx(1,4) = paramCovP(0,4);
+ paramCovVtx(4,1) = paramCovP(4,0);
+ paramCovVtx(3,4) = paramCovP(2,4);
+ paramCovVtx(4,3) = paramCovP(4,2);
+
+ // Jacobian of the transformation (XVtx, X, YVtx, Y, q*PTot) -> (XVtx, SlopeXVtx, YVtx, SlopeYVtx, q*PTotVtx)
+ TMatrixD jacob(5,5);
+ jacob.UnitMatrix();
+ jacob(1,0) = - 1. / (zB - zVtx);
+ jacob(1,1) = 1. / (zB - zVtx);
+ jacob(3,2) = - 1. / (zB - zVtx);
+ jacob(3,3) = 1. / (zB - zVtx);
+
+ // Compute covariances at vertex in the (XVtx, SlopeXVtx, YVtx, SlopeYVtx, q*PTotVtx) coordinate system
+ TMatrixD tmp(paramCovVtx,TMatrixD::kMultTranspose,jacob);
+ TMatrixD newParamCov(jacob,TMatrixD::kMult,tmp);
+
+ // Compute covariances at vertex in the (XVtx, SlopeXVtx, YVtx, SlopeYVtx, q/PyzVtx) coordinate system
+ CovP2Cov(newParam,newParamCov);
+
+ // Set parameters and covariances at vertex
+ param->SetParameters(newParam);
+ param->SetZ(zVtx);
+ param->SetCovariances(newParamCov);
+}
+
+//__________________________________________________________________________
+void AliMUONTrackExtrap::CorrectELossEffectInAbsorber(AliMUONTrackParam* param, Double_t eLoss, Double_t sigmaELoss2)
+{
+ /// Correct parameters for energy loss and add energy loss fluctuation effect to covariances
+
+ // Get parameter covariances in (X, SlopeX, Y, SlopeY, q*PTot) coordinate system
+ TMatrixD newParamCov(param->GetCovariances());
+ Cov2CovP(param->GetParameters(),newParamCov);
+
+ // Add effects of energy loss fluctuation to covariances
+ newParamCov(4,4) += sigmaELoss2;
+
+ // Compute new parameters corrected for energy loss
+ Double_t nonBendingSlope = param->GetNonBendingSlope();
+ Double_t bendingSlope = param->GetBendingSlope();
+ param->SetInverseBendingMomentum(param->GetCharge() / (param->P() + eLoss) *
+ TMath::Sqrt(1.0 + nonBendingSlope*nonBendingSlope + bendingSlope*bendingSlope) /
+ TMath::Sqrt(1.0 + bendingSlope*bendingSlope));
+
+ // Get new parameter covariances in (X, SlopeX, Y, SlopeY, q/Pyz) coordinate system
+ CovP2Cov(param->GetParameters(),newParamCov);
+
+ // Set new parameter covariances
+ param->SetCovariances(newParamCov);
+}
+
+//__________________________________________________________________________
+Bool_t AliMUONTrackExtrap::GetAbsorberCorrectionParam(Double_t trackXYZIn[3], Double_t trackXYZOut[3], Double_t pTotal,
+ Double_t &pathLength, Double_t &f0, Double_t &f1, Double_t &f2,
+ Double_t &meanRho, Double_t &totalELoss, Double_t &sigmaELoss2)
+{
+ /// Parameters used to correct for Multiple Coulomb Scattering and energy loss in absorber
+ /// Calculated assuming a linear propagation from trackXYZIn to trackXYZOut (order is important)
+ // pathLength: path length between trackXYZIn and trackXYZOut (cm)
+ // f0: 0th moment of z calculated with the inverse radiation-length distribution
+ // f1: 1st moment of z calculated with the inverse radiation-length distribution
+ // f2: 2nd moment of z calculated with the inverse radiation-length distribution
+ // meanRho: average density of crossed material (g/cm3)
+ // totalELoss: total energy loss in absorber
+
+ // Reset absorber's parameters
+ pathLength = 0.;
+ f0 = 0.;
+ f1 = 0.;
+ f2 = 0.;
+ meanRho = 0.;
+ totalELoss = 0.;
+ sigmaELoss2 = 0.;
+
+ // Check whether the geometry is available
+ if (!gGeoManager) {
+ cout<<"E-AliMUONTrackExtrap::GetAbsorberCorrectionParam: no TGeo"<<endl;
+ return kFALSE;
}
- // First Extrapolates track parameters upstream to the "Z" end of the front absorber
- if (trackParam->GetZ() < AliMUONConstants::ZAbsorberEnd()) { // spectro. (z<0)
- ExtrapToZCov(trackParam,AliMUONConstants::ZAbsorberEnd());
- } else {
- cout<<"W-AliMUONTrackExtrap::ExtrapToVertexUncorrected: Starting Z ("<<trackParam->GetZ()
- <<") upstream or inside the front absorber (zAbsorberEnd = "<<AliMUONConstants::ZAbsorberEnd()<<")"<<endl;
+ // Initialize starting point and direction
+ pathLength = TMath::Sqrt((trackXYZOut[0] - trackXYZIn[0])*(trackXYZOut[0] - trackXYZIn[0])+
+ (trackXYZOut[1] - trackXYZIn[1])*(trackXYZOut[1] - trackXYZIn[1])+
+ (trackXYZOut[2] - trackXYZIn[2])*(trackXYZOut[2] - trackXYZIn[2]));
+ if (pathLength < TGeoShape::Tolerance()) return kFALSE;
+ Double_t b[3];
+ b[0] = (trackXYZOut[0] - trackXYZIn[0]) / pathLength;
+ b[1] = (trackXYZOut[1] - trackXYZIn[1]) / pathLength;
+ b[2] = (trackXYZOut[2] - trackXYZIn[2]) / pathLength;
+ TGeoNode *currentnode = gGeoManager->InitTrack(trackXYZIn, b);
+ if (!currentnode) {
+ cout<<"E-AliMUONTrackExtrap::GetAbsorberCorrectionParam: start point out of geometry"<<endl;
+ return kFALSE;
}
- // Then go through all the absorber layers
- Double_t tan3 = TMath::Tan(3./180.*TMath::Pi());
- Double_t r0Norm, x0, z, zElement, dZ, nonBendingCoor, bendingCoor;
- for (Int_t iElement=AliMUONConstants::NAbsorberElements()-1; iElement>=0; iElement--) {
- zElement = AliMUONConstants::ZAbsorberElement(iElement);
- z = trackParam->GetZ();
- if (z > zElement) continue; // spectro. (z<0)
- nonBendingCoor = trackParam->GetNonBendingCoor();
- bendingCoor = trackParam->GetBendingCoor();
- r0Norm = nonBendingCoor * nonBendingCoor + bendingCoor * bendingCoor;
- r0Norm = TMath::Sqrt(r0Norm) / TMath::Abs(trackParam->GetZ()) / tan3;
- if (r0Norm > 1.) x0 = AliMUONConstants::X0AbsorberOut(iElement); // outer part of the absorber
- else x0 = AliMUONConstants::X0AbsorberIn(iElement); // inner part of the absorber
+ // loop over absorber slices and calculate absorber's parameters
+ Double_t rho = 0.; // material density (g/cm3)
+ Double_t x0 = 0.; // radiation-length (cm-1)
+ Double_t atomicA = 0.; // A of material
+ Double_t atomicZ = 0.; // Z of material
+ Double_t localPathLength = 0;
+ Double_t remainingPathLength = pathLength;
+ Double_t zB = trackXYZIn[2];
+ Double_t zE, dzB, dzE;
+ do {
+ // Get material properties
+ TGeoMaterial *material = currentnode->GetVolume()->GetMedium()->GetMaterial();
+ rho = material->GetDensity();
+ x0 = material->GetRadLen();
+ if (!material->IsMixture()) x0 /= rho; // different normalization in the modeler for mixture
+ atomicA = material->GetA();
+ atomicZ = material->GetZ();
- if (zVtx > zElement) {
- ExtrapToZCov(trackParam,zElement); // extrapolate to absorber element "iElement"
- dZ = zElement - z;
- AddMCSEffectInTrackParamCov(trackParam,dZ,x0); // include MCS effect in covariances
- } else {
- ExtrapToZCov(trackParam,zVtx); // extrapolate to zVtx
- dZ = zVtx - z;
- AddMCSEffectInTrackParamCov(trackParam,dZ,x0); // include MCS effect in covariances
- break;
+ // Get path length within this material
+ gGeoManager->FindNextBoundary(remainingPathLength);
+ localPathLength = gGeoManager->GetStep() + 1.e-6;
+ // Check if boundary within remaining path length. If so, make sure to cross the boundary to prepare the next step
+ if (localPathLength >= remainingPathLength) localPathLength = remainingPathLength;
+ else {
+ currentnode = gGeoManager->Step();
+ if (!currentnode) {
+ cout<<"E-AliMUONTrackExtrap::GetAbsorberCorrectionParam: navigation failed"<<endl;
+ f0 = f1 = f2 = meanRho = totalELoss = sigmaELoss2 = 0.;
+ return kFALSE;
+ }
+ if (!gGeoManager->IsEntering()) {
+ // make another small step to try to enter in new absorber slice
+ gGeoManager->SetStep(0.001);
+ currentnode = gGeoManager->Step();
+ if (!gGeoManager->IsEntering() || !currentnode) {
+ cout<<"E-AliMUONTrackExtrap::GetAbsorberCorrectionParam: navigation failed"<<endl;
+ f0 = f1 = f2 = meanRho = totalELoss = sigmaELoss2 = 0.;
+ return kFALSE;
+ }
+ localPathLength += 0.001;
+ }
}
- }
+
+ // calculate absorber's parameters
+ zE = b[2] * localPathLength + zB;
+ dzB = zB - trackXYZIn[2];
+ dzE = zE - trackXYZIn[2];
+ f0 += localPathLength / x0;
+ f1 += (dzE*dzE - dzB*dzB) / b[2] / b[2] / x0 / 2.;
+ f2 += (dzE*dzE*dzE - dzB*dzB*dzB) / b[2] / b[2] / b[2] / x0 / 3.;
+ meanRho += localPathLength * rho;
+ totalELoss += BetheBloch(pTotal, localPathLength, rho, atomicA, atomicZ);
+ sigmaELoss2 += EnergyLossFluctuation2(pTotal, localPathLength, rho, atomicA, atomicZ);
+
+ // prepare next step
+ zB = zE;
+ remainingPathLength -= localPathLength;
+ } while (remainingPathLength > TGeoShape::Tolerance());
- // finally go to the vertex
- ExtrapToZCov(trackParam,zVtx);
+ meanRho /= pathLength;
+ return kTRUE;
}
- //__________________________________________________________________________
-void AliMUONTrackExtrap::AddMCSEffectInTrackParamCov(AliMUONTrackParam *param, Double_t dZ, Double_t x0)
+//__________________________________________________________________________
+Double_t AliMUONTrackExtrap::GetMCSAngle2(const AliMUONTrackParam& param, Double_t dZ, Double_t x0)
+{
+ /// Return the angular dispersion square due to multiple Coulomb scattering
+ /// through a material of thickness "dZ" and of radiation length "x0"
+ /// assuming linear propagation and using the small angle approximation.
+
+ Double_t bendingSlope = param.GetBendingSlope();
+ Double_t nonBendingSlope = param.GetNonBendingSlope();
+ Double_t inverseTotalMomentum2 = param.GetInverseBendingMomentum() * param.GetInverseBendingMomentum() *
+ (1.0 + bendingSlope * bendingSlope) /
+ (1.0 + bendingSlope *bendingSlope + nonBendingSlope * nonBendingSlope);
+ // Path length in the material
+ Double_t pathLength = TMath::Abs(dZ) * TMath::Sqrt(1.0 + bendingSlope*bendingSlope + nonBendingSlope*nonBendingSlope);
+ // relativistic velocity
+ Double_t velo = 1.;
+ // Angular dispersion square of the track (variance) in a plane perpendicular to the trajectory
+ Double_t theta02 = 0.0136 / velo * (1 + 0.038 * TMath::Log(pathLength/x0));
+
+ return theta02 * theta02 * inverseTotalMomentum2 * pathLength / x0;
+}
+
+//__________________________________________________________________________
+void AliMUONTrackExtrap::AddMCSEffect(AliMUONTrackParam *param, Double_t dZ, Double_t x0)
{
/// Add to the track parameter covariances the effects of multiple Coulomb scattering
/// through a material of thickness "dZ" and of radiation length "x0"
Double_t bendingSlope = param->GetBendingSlope();
Double_t nonBendingSlope = param->GetNonBendingSlope();
- Double_t inverseTotalMomentum2 = param->GetInverseBendingMomentum() * param->GetInverseBendingMomentum() *
- (1.0 + bendingSlope * bendingSlope) /
- (1.0 + bendingSlope *bendingSlope + nonBendingSlope * nonBendingSlope);
+ Double_t inverseBendingMomentum = param->GetInverseBendingMomentum();
+ Double_t inverseTotalMomentum2 = inverseBendingMomentum * inverseBendingMomentum *
+ (1.0 + bendingSlope * bendingSlope) /
+ (1.0 + bendingSlope *bendingSlope + nonBendingSlope * nonBendingSlope);
// Path length in the material
Double_t pathLength = TMath::Abs(dZ) * TMath::Sqrt(1.0 + bendingSlope*bendingSlope + nonBendingSlope*nonBendingSlope);
Double_t pathLength2 = pathLength * pathLength;
Double_t theta02 = 0.0136 / velo * (1 + 0.038 * TMath::Log(pathLength/x0));
theta02 *= theta02 * inverseTotalMomentum2 * pathLength / x0;
- // Add effects of multiple Coulomb scattering in track parameter covariances
- TMatrixD* paramCov = param->GetCovariances();
Double_t varCoor = pathLength2 * theta02 / 3.;
Double_t varSlop = theta02;
Double_t covCorrSlope = pathLength * theta02 / 2.;
+
+ // compute derivative d(q/Pxy) / dSlopeX and d(q/Pxy) / dSlopeX
+ Double_t dqPxydSlopeX = inverseBendingMomentum * nonBendingSlope / (1. + nonBendingSlope*nonBendingSlope + bendingSlope*bendingSlope);
+ Double_t dqPxydSlopeY = - inverseBendingMomentum * nonBendingSlope*nonBendingSlope * bendingSlope /
+ (1. + bendingSlope*bendingSlope) / (1. + nonBendingSlope*nonBendingSlope + bendingSlope*bendingSlope);
+
+ // Set MCS covariance matrix
+ TMatrixD newParamCov(param->GetCovariances());
// Non bending plane
- (*paramCov)(0,0) += varCoor; (*paramCov)(0,1) += covCorrSlope;
- (*paramCov)(1,0) += covCorrSlope; (*paramCov)(1,1) += varSlop;
+ newParamCov(0,0) += varCoor; newParamCov(0,1) += covCorrSlope;
+ newParamCov(1,0) += covCorrSlope; newParamCov(1,1) += varSlop;
// Bending plane
- (*paramCov)(2,2) += varCoor; (*paramCov)(2,3) += covCorrSlope;
- (*paramCov)(3,2) += covCorrSlope; (*paramCov)(3,3) += varSlop;
+ newParamCov(2,2) += varCoor; newParamCov(2,3) += covCorrSlope;
+ newParamCov(3,2) += covCorrSlope; newParamCov(3,3) += varSlop;
+ // Inverse bending momentum (due to dependences with bending and non bending slopes)
+ newParamCov(4,0) += dqPxydSlopeX * covCorrSlope; newParamCov(0,4) += dqPxydSlopeX * covCorrSlope;
+ newParamCov(4,1) += dqPxydSlopeX * varSlop; newParamCov(1,4) += dqPxydSlopeX * varSlop;
+ newParamCov(4,2) += dqPxydSlopeY * covCorrSlope; newParamCov(2,4) += dqPxydSlopeY * covCorrSlope;
+ newParamCov(4,3) += dqPxydSlopeY * varSlop; newParamCov(3,4) += dqPxydSlopeY * varSlop;
+ newParamCov(4,4) += (dqPxydSlopeX*dqPxydSlopeX + dqPxydSlopeY*dqPxydSlopeY) * varSlop;
+ // Set new covariances
+ param->SetCovariances(newParamCov);
}
- //__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapToVertex(AliMUONTrackParam* trackParam, Double_t xVtx, Double_t yVtx, Double_t zVtx)
+//__________________________________________________________________________
+void AliMUONTrackExtrap::ExtrapToVertex(AliMUONTrackParam* trackParam,
+ Double_t xVtx, Double_t yVtx, Double_t zVtx,
+ Double_t errXVtx, Double_t errYVtx,
+ Bool_t correctForMCS, Bool_t correctForEnergyLoss)
{
- /// 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
-
- // Extrapolates track parameters upstream to the "Z" end of the front absorber
- ExtrapToZ(trackParam,AliMUONConstants::ZAbsorberEnd()); // !!!
- // Makes Branson correction (multiple scattering + energy loss)
- BransonCorrection(trackParam,xVtx,yVtx,zVtx);
- // Makes a simple magnetic field correction through the absorber
- FieldCorrection(trackParam,AliMUONConstants::ZAbsorberEnd());
+ /// Main method for extrapolation to the vertex:
+ /// Returns the track parameters and covariances resulting from the extrapolation of the current trackParam
+ /// Changes parameters and covariances according to multiple scattering and energy loss corrections:
+ /// if correctForMCS=kTRUE: compute parameters using Branson correction and add correction resolution to covariances
+ /// if correctForMCS=kFALSE: add parameter dispersion due to MCS in parameter covariances
+ /// if correctForEnergyLoss=kTRUE: correct parameters for energy loss and add energy loss fluctuation to covariances
+ /// if correctForEnergyLoss=kFALSE: do nothing about energy loss
+
+ if (trackParam->GetZ() == zVtx) return; // nothing to be done if already at vertex
+
+ if (trackParam->GetZ() > zVtx) { // spectro. (z<0)
+ cout<<"E-AliMUONTrackExtrap::ExtrapToVertex: Starting Z ("<<trackParam->GetZ()
+ <<") upstream the vertex (zVtx = "<<zVtx<<")"<<endl;
+ return;
+ }
+
+ // Check the vertex position relatively to the absorber
+ if (zVtx < AliMUONConstants::AbsZBeg() && zVtx > AliMUONConstants::AbsZEnd()) { // spectro. (z<0)
+ cout<<"W-AliMUONTrackExtrap::ExtrapToVertex: Ending Z ("<<zVtx
+ <<") inside the front absorber ("<<AliMUONConstants::AbsZBeg()<<","<<AliMUONConstants::AbsZEnd()<<")"<<endl;
+ } else if (zVtx < AliMUONConstants::AbsZEnd() ) { // spectro. (z<0)
+ cout<<"W-AliMUONTrackExtrap::ExtrapToVertex: Ending Z ("<<zVtx
+ <<") downstream the front absorber (zAbsorberEnd = "<<AliMUONConstants::AbsZEnd()<<")"<<endl;
+ if (trackParam->CovariancesExist()) ExtrapToZCov(trackParam,zVtx);
+ else ExtrapToZ(trackParam,zVtx);
+ return;
+ }
+
+ // Check the track position relatively to the absorber and extrapolate track parameters to the end of the absorber if needed
+ if (trackParam->GetZ() > AliMUONConstants::AbsZBeg()) { // spectro. (z<0)
+ cout<<"W-AliMUONTrackExtrap::ExtrapToVertex: Starting Z ("<<trackParam->GetZ()
+ <<") upstream the front absorber (zAbsorberBegin = "<<AliMUONConstants::AbsZBeg()<<")"<<endl;
+ if (trackParam->CovariancesExist()) ExtrapToZCov(trackParam,zVtx);
+ else ExtrapToZ(trackParam,zVtx);
+ return;
+ } else if (trackParam->GetZ() > AliMUONConstants::AbsZEnd()) { // spectro. (z<0)
+ cout<<"W-AliMUONTrackExtrap::ExtrapToVertex: Starting Z ("<<trackParam->GetZ()
+ <<") inside the front absorber ("<<AliMUONConstants::AbsZBeg()<<","<<AliMUONConstants::AbsZEnd()<<")"<<endl;
+ } else {
+ if (trackParam->CovariancesExist()) ExtrapToZCov(trackParam,AliMUONConstants::AbsZEnd());
+ else ExtrapToZ(trackParam,AliMUONConstants::AbsZEnd());
+ }
+
+ // Get absorber correction parameters assuming linear propagation in absorber
+ Double_t trackXYZOut[3];
+ trackXYZOut[0] = trackParam->GetNonBendingCoor();
+ trackXYZOut[1] = trackParam->GetBendingCoor();
+ trackXYZOut[2] = trackParam->GetZ();
+ Double_t trackXYZIn[3];
+ if (correctForMCS) { // assume linear propagation until the vertex
+ trackXYZIn[2] = TMath::Min(zVtx, AliMUONConstants::AbsZBeg()); // spectro. (z<0)
+ trackXYZIn[0] = trackXYZOut[0] + (xVtx - trackXYZOut[0]) / (zVtx - trackXYZOut[2]) * (trackXYZIn[2] - trackXYZOut[2]);
+ trackXYZIn[1] = trackXYZOut[1] + (yVtx - trackXYZOut[1]) / (zVtx - trackXYZOut[2]) * (trackXYZIn[2] - trackXYZOut[2]);
+ } else {
+ AliMUONTrackParam trackParamIn(*trackParam);
+ ExtrapToZ(&trackParamIn, TMath::Min(zVtx, AliMUONConstants::AbsZBeg()));
+ trackXYZIn[0] = trackParamIn.GetNonBendingCoor();
+ trackXYZIn[1] = trackParamIn.GetBendingCoor();
+ trackXYZIn[2] = trackParamIn.GetZ();
+ }
+ Double_t pTot = trackParam->P();
+ Double_t pathLength, f0, f1, f2, meanRho, deltaP, sigmaDeltaP2;
+ if (!GetAbsorberCorrectionParam(trackXYZIn,trackXYZOut,pTot,pathLength,f0,f1,f2,meanRho,deltaP,sigmaDeltaP2)) {
+ cout<<"E-AliMUONTrackExtrap::ExtrapToVertex: Unable to take into account the absorber effects"<<endl;
+ if (trackParam->CovariancesExist()) ExtrapToZCov(trackParam,zVtx);
+ else ExtrapToZ(trackParam,zVtx);
+ return;
+ }
+
+ // Compute track parameters and covariances at vertex according to correctForMCS and correctForEnergyLoss flags
+ if (correctForMCS) {
+
+ if (correctForEnergyLoss) {
+
+ // Correct for multiple scattering and energy loss
+ CorrectELossEffectInAbsorber(trackParam, 0.5*deltaP, 0.5*sigmaDeltaP2);
+ CorrectMCSEffectInAbsorber(trackParam, xVtx, yVtx, zVtx, errXVtx, errYVtx,
+ trackXYZIn[2], pathLength, f0, f1, f2);
+ CorrectELossEffectInAbsorber(trackParam, 0.5*deltaP, 0.5*sigmaDeltaP2);
+
+ } else {
+
+ // Correct for multiple scattering
+ CorrectMCSEffectInAbsorber(trackParam, xVtx, yVtx, zVtx, errXVtx, errYVtx,
+ trackXYZIn[2], pathLength, f0, f1, f2);
+ }
+
+ } else {
+
+ if (correctForEnergyLoss) {
+
+ // Correct for energy loss add multiple scattering dispersion in covariance matrix
+ CorrectELossEffectInAbsorber(trackParam, 0.5*deltaP, 0.5*sigmaDeltaP2);
+ AddMCSEffectInAbsorber(trackParam, pathLength, f0, f1, f2);
+ ExtrapToZCov(trackParam, trackXYZIn[2]);
+ CorrectELossEffectInAbsorber(trackParam, 0.5*deltaP, 0.5*sigmaDeltaP2);
+ ExtrapToZCov(trackParam, zVtx);
+
+ } else {
+
+ // add multiple scattering dispersion in covariance matrix
+ AddMCSEffectInAbsorber(trackParam, pathLength, f0, f1, f2);
+ ExtrapToZCov(trackParam, zVtx);
+
+ }
+
+ }
+
}
-
-// Keep this version for future developments
- //__________________________________________________________________________
-// void AliMUONTrackExtrap::BransonCorrection(AliMUONTrackParam* trackParam)
-// {
-// /// 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 / trackParam->GetInverseBendingMomentum());
-// sign = 1;
-// if (trackParam->GetInverseBendingMomentum() < 0) sign = -1;
-// pZ = pYZ / (TMath::Sqrt(1.0 + trackParam->GetBendingSlope() * trackParam->GetBendingSlope()));
-// pX = pZ * trackParam->GetNonBendingSlope();
-// pY = pZ * trackParam->GetBendingSlope();
-// pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX);
-// xEndAbsorber = trackParam->GetNonBendingCoor();
-// yEndAbsorber = trackParam->GetBendingCoor();
-// 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;
-// trackParam->SetBendingSlope(pY/pZ);
-// trackParam->SetNonBendingSlope(pX/pZ);
-//
-// pT = TMath::Sqrt(pX * pX + pY * pY);
-// theta = TMath::ATan2(pT, pZ);
-// pTotal = TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
-//
-// trackParam->SetInverseBendingMomentum((sign / pTotal) *
-// TMath::Sqrt(1.0 +
-// trackParam->GetBendingSlope() * trackParam->GetBendingSlope() +
-// trackParam->GetNonBendingSlope() * trackParam->GetNonBendingSlope()) /
-// TMath::Sqrt(1.0 + trackParam->GetBendingSlope() * trackParam->GetBendingSlope()));
-//
-// // vertex position at (0,0,0)
-// // should be taken from vertex measurement ???
-// trackParam->SetBendingCoor(0.);
-// trackParam->SetNonBendingCoor(0.);
-// trackParam->SetZ(0.);
-// }
-
-void AliMUONTrackExtrap::BransonCorrection(AliMUONTrackParam* trackParam, Double_t xVtx, Double_t yVtx, Double_t zVtx)
+//__________________________________________________________________________
+void AliMUONTrackExtrap::ExtrapToVertex(AliMUONTrackParam* trackParam,
+ Double_t xVtx, Double_t yVtx, Double_t zVtx,
+ Double_t errXVtx, Double_t errYVtx)
{
- /// Branson correction of track parameters
- // the entry parameters have to be calculated at the end of the absorber
- // simplified version: the z positions of Branson's planes are no longer calculated
- // but are given as inputs. One can use the macros MUONTestAbso.C and DrawTestAbso.C
- // to test this correction.
- // 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 ????
- // change to take into account the vertex postition (real, reconstruct,....)
-
- Double_t zBP, xBP, yBP;
- Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta;
- Int_t sign;
- static Bool_t first = kTRUE;
- static Double_t zBP1, zBP2, rLimit, thetaLimit;
- // zBP1 for outer part and zBP2 for inner part (only at the first call)
- if (first) {
- first = kFALSE;
-
- thetaLimit = 3.0 * (TMath::Pi()) / 180.;
- rLimit = TMath::Abs(AliMUONConstants::ZAbsorberEnd()) * TMath::Tan(thetaLimit);
- zBP1 = -450; // values close to those calculated with EvalAbso.C
- zBP2 = -480;
- }
+ /// Extrapolate track parameters to vertex, corrected for multiple scattering and energy loss effects
+ /// Add branson correction resolution and energy loss fluctuation to parameter covariances
+ ExtrapToVertex(trackParam, xVtx, yVtx, zVtx, errXVtx, errYVtx, kTRUE, kTRUE);
+}
- pYZ = TMath::Abs(1.0 / trackParam->GetInverseBendingMomentum());
- sign = 1;
- if (trackParam->GetInverseBendingMomentum() < 0) sign = -1;
- pZ = trackParam->Pz();
- pX = trackParam->Px();
- pY = trackParam->Py();
- pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX);
- xEndAbsorber = trackParam->GetNonBendingCoor();
- yEndAbsorber = trackParam->GetBendingCoor();
- radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber;
-
- if (radiusEndAbsorber2 > rLimit*rLimit) {
- zBP = zBP1;
- } else {
- zBP = zBP2;
- }
+//__________________________________________________________________________
+void AliMUONTrackExtrap::ExtrapToVertexWithoutELoss(AliMUONTrackParam* trackParam,
+ Double_t xVtx, Double_t yVtx, Double_t zVtx,
+ Double_t errXVtx, Double_t errYVtx)
+{
+ /// Extrapolate track parameters to vertex, corrected for multiple scattering effects only
+ /// Add branson correction resolution to parameter covariances
+ ExtrapToVertex(trackParam, xVtx, yVtx, zVtx, errXVtx, errYVtx, kTRUE, kFALSE);
+}
- xBP = xEndAbsorber - (pX / pZ) * (AliMUONConstants::ZAbsorberEnd() - zBP);
- yBP = yEndAbsorber - (pY / pZ) * (AliMUONConstants::ZAbsorberEnd() - zBP);
+//__________________________________________________________________________
+void AliMUONTrackExtrap::ExtrapToVertexWithoutBranson(AliMUONTrackParam* trackParam, Double_t zVtx)
+{
+ /// Extrapolate track parameters to vertex, corrected for energy loss effects only
+ /// Add dispersion due to multiple scattering and energy loss fluctuation to parameter covariances
+ ExtrapToVertex(trackParam, 0., 0., zVtx, 0., 0., kFALSE, kTRUE);
+}
- // new parameters after Branson and energy loss corrections
-// Float_t zSmear = zBP - gRandom->Gaus(0.,2.); // !!! possible smearing of Z vertex position
+//__________________________________________________________________________
+void AliMUONTrackExtrap::ExtrapToVertexUncorrected(AliMUONTrackParam* trackParam, Double_t zVtx)
+{
+ /// Extrapolate track parameters to vertex without multiple scattering and energy loss corrections
+ /// Add dispersion due to multiple scattering to parameter covariances
+ ExtrapToVertex(trackParam, 0., 0., zVtx, 0., 0., kFALSE, kFALSE);
+}
- Float_t zSmear = zBP ;
+//__________________________________________________________________________
+Double_t AliMUONTrackExtrap::TotalMomentumEnergyLoss(AliMUONTrackParam* trackParam, Double_t xVtx, Double_t yVtx, Double_t zVtx)
+{
+ /// Calculate the total momentum energy loss in-between the track position and the vertex assuming a linear propagation
- pZ = pTotal * (zSmear-zVtx) / TMath::Sqrt((xBP-xVtx) * (xBP-xVtx) + (yBP-yVtx) * (yBP-yVtx) +( zSmear-zVtx) * (zSmear-zVtx) );
- pX = pZ * (xBP - xVtx)/ (zSmear-zVtx);
- pY = pZ * (yBP - yVtx) / (zSmear-zVtx);
- trackParam->SetBendingSlope(pY/pZ);
- trackParam->SetNonBendingSlope(pX/pZ);
-
+ if (trackParam->GetZ() == zVtx) return 0.; // nothing to be done if already at vertex
- pT = TMath::Sqrt(pX * pX + pY * pY);
- theta = TMath::ATan2(pT, TMath::Abs(pZ));
- pTotal = TotalMomentumEnergyLoss(thetaLimit, pTotal, theta);
-
- trackParam->SetInverseBendingMomentum((sign / pTotal) *
- TMath::Sqrt(1.0 +
- trackParam->GetBendingSlope() * trackParam->GetBendingSlope() +
- trackParam->GetNonBendingSlope() * trackParam->GetNonBendingSlope()) /
- TMath::Sqrt(1.0 + trackParam->GetBendingSlope() * trackParam->GetBendingSlope()));
-
- // vertex position at (0,0,0)
- // should be taken from vertex measurement ???
+ // Check whether the geometry is available
+ if (!gGeoManager) {
+ cout<<"E-AliMUONTrackExtrap::TotalMomentumEnergyLoss: no TGeo"<<endl;
+ return 0.;
+ }
+
+ // Get encountered material correction parameters assuming linear propagation from vertex to the track position
+ Double_t trackXYZOut[3];
+ trackXYZOut[0] = trackParam->GetNonBendingCoor();
+ trackXYZOut[1] = trackParam->GetBendingCoor();
+ trackXYZOut[2] = trackParam->GetZ();
+ Double_t trackXYZIn[3];
+ trackXYZIn[0] = xVtx;
+ trackXYZIn[1] = yVtx;
+ trackXYZIn[2] = zVtx;
+ Double_t pTot = trackParam->P();
+ Double_t pathLength, f0, f1, f2, meanRho, totalELoss, sigmaELoss2;
+ GetAbsorberCorrectionParam(trackXYZIn,trackXYZOut,pTot,pathLength,f0,f1,f2,meanRho,totalELoss,sigmaELoss2);
+
+ return totalELoss;
+}
- trackParam->SetBendingCoor(xVtx);
- trackParam->SetNonBendingCoor(yVtx);
- trackParam->SetZ(zVtx);
+//__________________________________________________________________________
+Double_t AliMUONTrackExtrap::BetheBloch(Double_t pTotal, Double_t pathLength, Double_t rho, Double_t atomicA, Double_t atomicZ)
+{
+ /// Returns the mean total momentum energy loss of muon with total momentum='pTotal'
+ /// in the absorber layer of lenght='pathLength', density='rho', A='atomicA' and Z='atomicZ'
+ Double_t muMass = 0.105658369; // GeV
+ Double_t eMass = 0.510998918e-3; // GeV
+ Double_t k = 0.307075e-3; // GeV.g^-1.cm^2
+ Double_t i = 9.5e-9; // mean exitation energy per atomic Z (GeV)
+ Double_t p2=pTotal*pTotal;
+ Double_t beta2=p2/(p2 + muMass*muMass);
+
+ Double_t w = k * rho * pathLength * atomicZ / atomicA / beta2;
+
+ if (beta2/(1-beta2)>3.5*3.5)
+ return w * (log(2.*eMass*3.5/(i*atomicZ)) + 0.5*log(beta2/(1-beta2)) - beta2);
+
+ return w * (log(2.*eMass*beta2/(1-beta2)/(i*atomicZ)) - beta2);
+}
+//__________________________________________________________________________
+Double_t AliMUONTrackExtrap::EnergyLossFluctuation2(Double_t pTotal, Double_t pathLength, Double_t rho, Double_t atomicA, Double_t atomicZ)
+{
+ /// Returns the total momentum energy loss fluctuation of muon with total momentum='pTotal'
+ /// in the absorber layer of lenght='pathLength', density='rho', A='atomicA' and Z='atomicZ'
+ Double_t muMass = 0.105658369; // GeV
+ //Double_t eMass = 0.510998918e-3; // GeV
+ Double_t k = 0.307075e-3; // GeV.g^-1.cm^2
+ Double_t p2=pTotal*pTotal;
+ Double_t beta2=p2/(p2 + muMass*muMass);
+
+ Double_t fwhm = 2. * k * rho * pathLength * atomicZ / atomicA / beta2; // FWHM of the energy loss Landau distribution
+ Double_t sigma2 = fwhm * fwhm / (8.*log(2.)); // gaussian: fwmh = 2 * srqt(2*ln(2)) * sigma (i.e. fwmh = 2.35 * sigma)
+
+ //sigma2 = k * rho * pathLength * atomicZ / atomicA * eMass; // sigma2 of the energy loss gaussian distribution
+
+ return sigma2;
}
- //__________________________________________________________________________
-Double_t AliMUONTrackExtrap::TotalMomentumEnergyLoss(Double_t thetaLimit, Double_t pTotal, Double_t theta)
+//__________________________________________________________________________
+void AliMUONTrackExtrap::Cov2CovP(const TMatrixD ¶m, TMatrixD &cov)
{
- /// Returns the total momentum corrected from energy loss in the front absorber
- // One can use the macros MUONTestAbso.C and DrawTestAbso.C
- // to test this correction.
- // Momentum energy loss behaviour evaluated with the simulation of single muons (april 2002)
- Double_t deltaP, pTotalCorrected;
-
- // 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 (theta < thetaLimit ) {
- if (pTotal < 20) {
- deltaP = 2.5938 + 0.0570 * pTotal - 0.001151 * pTotal * pTotal;
- } else {
- deltaP = 3.0714 + 0.011767 *pTotal;
- }
- deltaP *= 0.75; // AZ
- } else {
- if (pTotal < 20) {
- deltaP = 2.1207 + 0.05478 * pTotal - 0.00145079 * pTotal * pTotal;
- } else {
- deltaP = 2.6069 + 0.0051705 * pTotal;
- }
- deltaP *= 0.9; // AZ
- }
- pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
- return pTotalCorrected;
+ /// change coordinate system: (X, SlopeX, Y, SlopeY, q/Pyz) -> (X, SlopeX, Y, SlopeY, q*PTot)
+ /// parameters (param) are given in the (X, SlopeX, Y, SlopeY, q/Pyz) coordinate system
+
+ // charge * total momentum
+ Double_t qPTot = TMath::Sqrt(1. + param(1,0)*param(1,0) + param(3,0)*param(3,0)) /
+ TMath::Sqrt(1. + param(3,0)*param(3,0)) / param(4,0);
+
+ // Jacobian of the opposite transformation
+ TMatrixD jacob(5,5);
+ jacob.UnitMatrix();
+ jacob(4,1) = qPTot * param(1,0) / (1. + param(1,0)*param(1,0) + param(3,0)*param(3,0));
+ jacob(4,3) = - qPTot * param(1,0) * param(1,0) * param(3,0) /
+ (1. + param(3,0)*param(3,0)) / (1. + param(1,0)*param(1,0) + param(3,0)*param(3,0));
+ jacob(4,4) = - qPTot / param(4,0);
+
+ // compute covariances in new coordinate system
+ TMatrixD tmp(cov,TMatrixD::kMultTranspose,jacob);
+ cov.Mult(jacob,tmp);
}
- //__________________________________________________________________________
-void AliMUONTrackExtrap::FieldCorrection(AliMUONTrackParam *trackParam, Double_t zEnd)
+//__________________________________________________________________________
+void AliMUONTrackExtrap::CovP2Cov(const TMatrixD ¶m, TMatrixD &covP)
{
- /// Correction of the effect of the magnetic field in the absorber
- // Assume a constant field along Z axis.
- Float_t b[3],x[3];
- Double_t bZ;
- Double_t pYZ,pX,pY,pZ,pT;
- Double_t pXNew,pYNew;
- Double_t c;
-
- pYZ = TMath::Abs(1.0 / trackParam->GetInverseBendingMomentum());
- c = TMath::Sign(1.0,trackParam->GetInverseBendingMomentum()); // particle charge
-
- pZ = trackParam->Pz();
- pX = trackParam->Px();
- pY = trackParam->Py();
- pT = TMath::Sqrt(pX*pX+pY*pY);
-
- if (TMath::Abs(pZ) <= 0) return;
- x[2] = zEnd/2;
- x[0] = x[2]*trackParam->GetNonBendingSlope();
- x[1] = x[2]*trackParam->GetBendingSlope();
-
- // Take magn. field value at position x.
- if (fgkField) fgkField->Field(x,b);
- else {
- cout<<"F-AliMUONTrackExtrap::FieldCorrection: fgkField = 0x0"<<endl;
- exit(-1);
- }
- bZ = b[2];
-
- // Transverse momentum rotation
- // Parameterized with the study of DeltaPhi = phiReco - phiGen as a function of pZ.
- Double_t phiShift = c*0.436*0.0003*bZ*zEnd/pZ;
- // Rotate momentum around Z axis.
- pXNew = pX*TMath::Cos(phiShift) - pY*TMath::Sin(phiShift);
- pYNew = pX*TMath::Sin(phiShift) + pY*TMath::Cos(phiShift);
-
- trackParam->SetBendingSlope(pYNew/pZ);
- trackParam->SetNonBendingSlope(pXNew/pZ);
+ /// change coordinate system: (X, SlopeX, Y, SlopeY, q*PTot) -> (X, SlopeX, Y, SlopeY, q/Pyz)
+ /// parameters (param) are given in the (X, SlopeX, Y, SlopeY, q/Pyz) coordinate system
- trackParam->SetInverseBendingMomentum(c/TMath::Sqrt(pYNew*pYNew+pZ*pZ));
-
+ // charge * total momentum
+ Double_t qPTot = TMath::Sqrt(1. + param(1,0)*param(1,0) + param(3,0)*param(3,0)) /
+ TMath::Sqrt(1. + param(3,0)*param(3,0)) / param(4,0);
+
+ // Jacobian of the transformation
+ TMatrixD jacob(5,5);
+ jacob.UnitMatrix();
+ jacob(4,1) = param(4,0) * param(1,0) / (1. + param(1,0)*param(1,0) + param(3,0)*param(3,0));
+ jacob(4,3) = - param(4,0) * param(1,0) * param(1,0) * param(3,0) /
+ (1. + param(3,0)*param(3,0)) / (1. + param(1,0)*param(1,0) + param(3,0)*param(3,0));
+ jacob(4,4) = - param(4,0) / qPTot;
+
+ // compute covariances in new coordinate system
+ TMatrixD tmp(covP,TMatrixD::kMultTranspose,jacob);
+ covP.Mult(jacob,tmp);
}
//__________________________________________________________________________
void AliMUONTrackExtrap::ExtrapOneStepHelix(Double_t charge, Double_t step, Double_t *vect, Double_t *vout)
{
+/// <pre>
/// ******************************************************************
/// * *
/// * Performs the tracking of one step in a magnetic field *
/// * output *
/// * VOUT = same as VECT after completion of the step *
/// * *
-/// * ==>Called by : <USER>, GUSWIM *
+/// * ==>Called by : USER, GUSWIM *
/// * Author m.hansroul ********* *
/// * modified s.egli, s.v.levonian *
/// * modified v.perevoztchikov
/// * *
/// ******************************************************************
+/// </pre>
// modif: everything in double precision
xyz[2] = vect[kiz] + 0.5 * step * vect[kipz];
//cmodif: call gufld (xyz, h) changed into:
- GetField (xyz, h);
+ TGeoGlobalMagField::Instance()->Field(xyz,h);
h2xy = h[0]*h[0] + h[1]*h[1];
h[3] = h[2]*h[2]+ h2xy;
//__________________________________________________________________________
void AliMUONTrackExtrap::ExtrapOneStepHelix3(Double_t field, Double_t step, Double_t *vect, Double_t *vout)
{
+/// <pre>
/// ******************************************************************
/// * *
/// * Tracking routine in a constant field oriented *
/// * Tracking is performed with a conventional *
/// * helix step method *
/// * *
-/// * ==>Called by : <USER>, GUSWIM *
+/// * ==>Called by : USER, GUSWIM *
/// * Authors R.Brun, M.Hansroul ********* *
/// * Rewritten V.Perevoztchikov
/// * *
/// ******************************************************************
+/// </pre>
Double_t hxp[3];
Double_t h4, hp, rho, tet;
return;
}
+
//__________________________________________________________________________
void AliMUONTrackExtrap::ExtrapOneStepRungekutta(Double_t charge, Double_t step, Double_t* vect, Double_t* vout)
{
+/// <pre>
/// ******************************************************************
/// * *
/// * Runge-Kutta method for tracking a particle through a magnetic *
/// * User routine called *
/// * CALL GUFLD(X,F) *
/// * *
-/// * ==>Called by : <USER>, GUSWIM *
+/// * ==>Called by : USER, GUSWIM *
/// * Authors R.Brun, M.Hansroul ********* *
/// * V.Perevoztchikov (CUT STEP implementation) *
/// * *
/// * *
/// ******************************************************************
+/// </pre>
Double_t h2, h4, f[4];
Double_t xyzt[3], a, b, c, ph,ph2;
rest = step - tl;
if (TMath::Abs(h) > TMath::Abs(rest)) h = rest;
//cmodif: call gufld(vout,f) changed into:
-
- GetField(vout,f);
+ TGeoGlobalMagField::Instance()->Field(vout,f);
// *
// * start of integration
xyzt[2] = zt;
//cmodif: call gufld(xyzt,f) changed into:
- GetField(xyzt,f);
+ TGeoGlobalMagField::Instance()->Field(xyzt,f);
at = a + secxs[0];
bt = b + secys[0];
xyzt[2] = zt;
//cmodif: call gufld(xyzt,f) changed into:
- GetField(xyzt,f);
+ TGeoGlobalMagField::Instance()->Field(xyzt,f);
z = z + (c + (seczs[0] + seczs[1] + seczs[2]) * kthird) * h;
y = y + (b + (secys[0] + secys[1] + secys[2]) * kthird) * h;
return;
}
-//___________________________________________________________
- void AliMUONTrackExtrap::GetField(Double_t *Position, Double_t *Field)
-{
- /// interface for arguments in double precision (Why ? ChF)
- Float_t x[3], b[3];
-
- x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2];
-
- if (fgkField) fgkField->Field(x,b);
- else {
- cout<<"F-AliMUONTrackExtrap::GetField: fgkField = 0x0"<<endl;
- exit(-1);
- }
-
- Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2];
-
- return;
-}