}
//__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapToZ(AliMUONTrackParam* trackParam, Double_t zEnd)
+Bool_t 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 (!fgFieldON) AliMUONTrackExtrap::LinearExtrapToZ(trackParam,zEnd);
- else if (fgkUseHelix) AliMUONTrackExtrap::ExtrapToZHelix(trackParam,zEnd);
- else AliMUONTrackExtrap::ExtrapToZRungekutta(trackParam,zEnd);
+ if (!fgFieldON) {
+ AliMUONTrackExtrap::LinearExtrapToZ(trackParam,zEnd);
+ return kTRUE;
+ }
+ else if (fgkUseHelix) return AliMUONTrackExtrap::ExtrapToZHelix(trackParam,zEnd);
+ else return AliMUONTrackExtrap::ExtrapToZRungekutta(trackParam,zEnd);
}
//__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapToZHelix(AliMUONTrackParam* trackParam, Double_t zEnd)
+Bool_t AliMUONTrackExtrap::ExtrapToZHelix(AliMUONTrackParam* trackParam, Double_t zEnd)
{
/// Track parameter extrapolation to the plane at "Z" using Helix algorithm.
/// On return, the track parameters resulting from the extrapolation are updated in trackParam.
- if (trackParam->GetZ() == zEnd) return; // nothing to be done if same Z
+ if (trackParam->GetZ() == zEnd) return kTRUE; // nothing to be done if same Z
Double_t forwardBackward; // +1 if forward, -1 if backward
if (zEnd < trackParam->GetZ()) forwardBackward = 1.0; // spectro. z<0
else forwardBackward = -1.0;
}
// Recover track parameters (charge back for forward motion)
RecoverTrackParam(v3, chargeExtrap * forwardBackward, trackParam);
+ return kTRUE;
}
//__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapToZRungekutta(AliMUONTrackParam* trackParam, Double_t zEnd)
+Bool_t AliMUONTrackExtrap::ExtrapToZRungekutta(AliMUONTrackParam* trackParam, Double_t zEnd)
{
/// Track parameter extrapolation to the plane at "Z" using Rungekutta algorithm.
/// On return, the track parameters resulting from the extrapolation are updated in trackParam.
- if (trackParam->GetZ() == zEnd) return; // nothing to be done if same Z
+ if (trackParam->GetZ() == zEnd) return kTRUE; // nothing to be done if same Z
Double_t forwardBackward; // +1 if forward, -1 if backward
if (zEnd < trackParam->GetZ()) forwardBackward = 1.0; // spectro. z<0
else forwardBackward = -1.0;
Double_t dZ, step;
Int_t stepNumber = 0;
- // Extrapolation loop (until within tolerance)
+ // Extrapolation loop (until within tolerance or the track turn around)
Double_t residue = zEnd - trackParam->GetZ();
+ Bool_t uturn = kFALSE;
+ Bool_t tooManyStep = kFALSE;
while (TMath::Abs(residue) > fgkRungeKuttaMaxResidue && stepNumber <= fgkMaxStepNumber) {
+
dZ = zEnd - trackParam->GetZ();
// step lenght assuming linear trajectory
step = dZ * TMath::Sqrt(1.0 + trackParam->GetBendingSlope()*trackParam->GetBendingSlope() +
trackParam->GetNonBendingSlope()*trackParam->GetNonBendingSlope());
ConvertTrackParamForExtrap(trackParam, forwardBackward, v3);
+
do { // reduce step lenght while zEnd oversteped
if (stepNumber > fgkMaxStepNumber) {
cout<<"W-AliMUONTrackExtrap::ExtrapToZRungekutta: Too many trials: "<<stepNumber<<endl;
+ tooManyStep = kTRUE;
break;
}
stepNumber ++;
residue = zEnd - v3New[2];
step *= dZ/(v3New[2]-trackParam->GetZ());
} while (residue*dZ < 0 && TMath::Abs(residue) > fgkRungeKuttaMaxResidue);
- RecoverTrackParam(v3New, chargeExtrap * forwardBackward, trackParam);
+
+ if (v3New[5]*v3[5] < 0) { // the track turned around
+ cout<<"W-AliMUONTrackExtrap::ExtrapToZRungekutta: The track turned around"<<endl;
+ uturn = kTRUE;
+ break;
+ } else RecoverTrackParam(v3New, chargeExtrap * forwardBackward, trackParam);
+
}
// terminate the extropolation with a straight line up to the exact "zEnd" value
- trackParam->SetNonBendingCoor(trackParam->GetNonBendingCoor() + residue * trackParam->GetNonBendingSlope());
- trackParam->SetBendingCoor(trackParam->GetBendingCoor() + residue * trackParam->GetBendingSlope());
- trackParam->SetZ(zEnd);
+ if (uturn) {
+
+ // track ends +-100 meters away in the bending direction
+ dZ = zEnd - v3[2];
+ Double_t bendingSlope = TMath::Sign(1.e4,-fgSimpleBValue*trackParam->GetInverseBendingMomentum()) / dZ;
+ Double_t pZ = TMath::Abs(1. / trackParam->GetInverseBendingMomentum()) / TMath::Sqrt(1.0 + bendingSlope * bendingSlope);
+ Double_t nonBendingSlope = TMath::Sign(TMath::Abs(v3[3]) * v3[6] / pZ, trackParam->GetNonBendingSlope());
+ trackParam->SetNonBendingCoor(trackParam->GetNonBendingCoor() + dZ * nonBendingSlope);
+ trackParam->SetNonBendingSlope(nonBendingSlope);
+ trackParam->SetBendingCoor(trackParam->GetBendingCoor() + dZ * bendingSlope);
+ trackParam->SetBendingSlope(bendingSlope);
+ trackParam->SetZ(zEnd);
+
+ return kFALSE;
+
+ } else {
+
+ // track extrapolated normally
+ trackParam->SetNonBendingCoor(trackParam->GetNonBendingCoor() + residue * trackParam->GetNonBendingSlope());
+ trackParam->SetBendingCoor(trackParam->GetBendingCoor() + residue * trackParam->GetBendingSlope());
+ trackParam->SetZ(zEnd);
+
+ return !tooManyStep;
+
+ }
+
}
//__________________________________________________________________________
}
//__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapToZCov(AliMUONTrackParam* trackParam, Double_t zEnd, Bool_t updatePropagator)
+Bool_t 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 (trackParam->GetZ() == zEnd) return kTRUE; // nothing to be done if same z
if (!fgFieldON) { // linear extrapolation if no magnetic field
AliMUONTrackExtrap::LinearExtrapToZCov(trackParam,zEnd,updatePropagator);
- return;
+ return kTRUE;
}
// 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;
+ return ExtrapToZ(trackParam,zEnd);
}
// Save the actual track parameters
const TMatrixD& kParamCov = trackParam->GetCovariances();
// Extrapolate track parameters to "zEnd"
- ExtrapToZ(trackParam,zEnd);
+ // Do not update the covariance matrix if the extrapolation failed
+ if (!ExtrapToZ(trackParam,zEnd)) return kFALSE;
// Get reference to the extrapolated parameters
const TMatrixD& extrapParam = trackParam->GetParameters();
// Calculate the jacobian related to the track parameters extrapolation to "zEnd"
+ Bool_t extrapStatus = kTRUE;
TMatrixD jacob(5,5);
jacob.Zero();
TMatrixD dParam(5,1);
trackParamSave.SetZ(zBegin);
// Extrapolate new track parameters to "zEnd"
- ExtrapToZ(&trackParamSave,zEnd);
+ if (!ExtrapToZ(&trackParamSave,zEnd)) {
+ cout<<"W-AliMUONTrackExtrap::ExtrapToZCov: Bad covariance matrix"<<endl;
+ extrapStatus = kFALSE;
+ }
// Calculate the jacobian
TMatrixD jacobji(trackParamSave.GetParameters(),TMatrixD::kMinus,extrapParam);
// Update the propagator if required
if (updatePropagator) trackParam->UpdatePropagator(jacob);
+
+ return extrapStatus;
}
//__________________________________________________________________________
-void AliMUONTrackExtrap::AddMCSEffectInAbsorber(AliMUONTrackParam* param, Double_t pathLength, Double_t f0, Double_t f1, Double_t f2)
+void AliMUONTrackExtrap::AddMCSEffectInAbsorber(AliMUONTrackParam* param, Double_t signedPathLength, Double_t f0, Double_t f1, Double_t f2)
{
/// 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
+ /// signedPathLength must have the sign of (zOut - zIn) where all other parameters are assumed to be given at zOut.
// absorber related covariance parameters
Double_t bendingSlope = param->GetBendingSlope();
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 pathLength = TMath::Abs(signedPathLength);
Double_t varCoor = alpha2 * (pathLength * pathLength * f0 - 2. * pathLength * f1 + f2);
- Double_t covCorrSlope = alpha2 * (pathLength * f0 - f1);
+ Double_t covCorrSlope = TMath::Sign(1.,signedPathLength) * alpha2 * (pathLength * f0 - f1);
Double_t varSlop = alpha2 * f0;
// Set MCS covariance matrix
// Position of the Branson plane (spectro. (z<0))
Double_t zB = (f1>0.) ? absZBeg - f2/f1 : 0.;
- // Add MCS effects to current parameter covariances
- AddMCSEffectInAbsorber(param, pathLength, f0, f1, f2);
+ // Add MCS effects to current parameter covariances (spectro. (z<0))
+ AddMCSEffectInAbsorber(param, -pathLength, f0, f1, f2);
// Get track parameters and covariances in the Branson plane corrected for magnetic field effect
ExtrapToZCov(param,zVtx);
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"
+ /// through a material of thickness "Abs(dZ)" and of radiation length "x0"
/// assuming linear propagation and using the small angle approximation.
+ /// dZ = zOut - zIn (sign is important) and "param" is assumed to be given zOut.
+ /// If x0 <= 0., assume dZ = pathLength/x0 and consider the material thickness as negligible.
Double_t bendingSlope = param->GetBendingSlope();
Double_t nonBendingSlope = param->GetNonBendingSlope();
(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 signedPathLength = dZ * TMath::Sqrt(1.0 + bendingSlope*bendingSlope + nonBendingSlope*nonBendingSlope);
+ Double_t pathLengthOverX0 = (x0 > 0.) ? TMath::Abs(signedPathLength) / x0 : TMath::Abs(signedPathLength);
// 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));
- theta02 *= theta02 * inverseTotalMomentum2 * pathLength / x0;
+ Double_t theta02 = 0.0136 / velo * (1 + 0.038 * TMath::Log(pathLengthOverX0));
+ theta02 *= theta02 * inverseTotalMomentum2 * pathLengthOverX0;
- Double_t varCoor = pathLength2 * theta02 / 3.;
+ Double_t varCoor = (x0 > 0.) ? signedPathLength * signedPathLength * theta02 / 3. : 0.;
Double_t varSlop = theta02;
- Double_t covCorrSlope = pathLength * theta02 / 2.;
+ Double_t covCorrSlope = (x0 > 0.) ? signedPathLength * theta02 / 2. : 0.;
// Set MCS covariance matrix
TMatrixD newParamCov(param->GetCovariances());
// Correct for energy loss add multiple scattering dispersion in covariance matrix
CorrectELossEffectInAbsorber(trackParam, 0.5*totalELoss, 0.5*sigmaELoss2);
- AddMCSEffectInAbsorber(trackParam, pathLength, f0, f1, f2);
+ AddMCSEffectInAbsorber(trackParam, -pathLength, f0, f1, f2); // (spectro. (z<0))
ExtrapToZCov(trackParam, trackXYZIn[2]);
CorrectELossEffectInAbsorber(trackParam, 0.5*totalELoss, 0.5*sigmaELoss2);
ExtrapToZCov(trackParam, zVtx);
} else {
// add multiple scattering dispersion in covariance matrix
- AddMCSEffectInAbsorber(trackParam, pathLength, f0, f1, f2);
+ AddMCSEffectInAbsorber(trackParam, -pathLength, f0, f1, f2); // (spectro. (z<0))
ExtrapToZCov(trackParam, zVtx);
}
git://git.uio.no / u / mrichter / AliRoot.git / blobdiff