#include "AliMUONTrackParam.h"
#include "AliMUONConstants.h"
#include "AliMUONReconstructor.h"
-#include "AliMUONRecoParam.h"
-#include "AliMagF.h"
+#include "AliMagF.h"
+#include "AliExternalTrackParam.h"
-#include <TMath.h>
+#include <TGeoGlobalMagField.h>
#include <TGeoManager.h>
+#include <TMath.h>
+#include <TDatabasePDG.h>
#include <Riostream.h>
+using std::endl;
+using std::cout;
/// \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 = (TMath::Abs(fgSimpleBValue) > 1.e-10) ? kTRUE : kFALSE;
+
+}
+
//__________________________________________________________________________
Double_t AliMUONTrackExtrap::GetImpactParamFromBendingMomentum(Double_t bendingMomentum)
{
if (bendingMomentum == 0.) return 1.e10;
- const Double_t kCorrectionFactor = 0.9; // impact parameter is 10% overestimated
- Double_t simpleBPosition = 0.5 * (AliMUONConstants::CoilZ() + AliMUONConstants::YokeZ());
- Double_t simpleBLength = 0.5 * (AliMUONConstants::CoilL() + AliMUONConstants::YokeL());
- Float_t b[3], x[3] = {50.,50.,(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 = 1.1; // impact parameter is 10% underestimated
- return kCorrectionFactor * (-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;
const Double_t kCorrectionFactor = 1.1; // bending momentum is 10% underestimated
- Double_t simpleBPosition = 0.5 * (AliMUONConstants::CoilZ() + AliMUONConstants::YokeZ());
- Double_t simpleBLength = 0.5 * (AliMUONConstants::CoilL() + AliMUONConstants::YokeL());
- Float_t b[3], x[3] = {50.,50.,(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];
- if (TMath::Abs(simpleBValue) > 0.01) return kCorrectionFactor * (-0.0003 * simpleBValue * simpleBLength * simpleBPosition / impactParam);
- else return AliMUONReconstructor::GetRecoParam()->GetMostProbBendingMomentum();
+ if (fgFieldON)
+ {
+ return kCorrectionFactor * (-0.0003 * fgSimpleBValue * fgkSimpleBLength * fgkSimpleBPosition / impactParam);
+ }
+ else
+ {
+ return AliMUONConstants::GetMostProbBendingMomentum();
+ }
}
//__________________________________________________________________________
void AliMUONTrackExtrap::LinearExtrapToZ(AliMUONTrackParam* trackParam, Double_t zEnd)
{
- /// Track parameters (and their covariances if any) linearly extrapolated to the plane at "zEnd".
+ /// Track parameters 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
trackParam->SetNonBendingCoor(trackParam->GetNonBendingCoor() + trackParam->GetNonBendingSlope() * dZ);
trackParam->SetBendingCoor(trackParam->GetBendingCoor() + trackParam->GetBendingSlope() * dZ);
trackParam->SetZ(zEnd);
+}
+
+//__________________________________________________________________________
+void AliMUONTrackExtrap::LinearExtrapToZCov(AliMUONTrackParam* trackParam, Double_t zEnd, Bool_t updatePropagator)
+{
+ /// Track parameters and their covariances 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
- // 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);
+ // No need to propagate the covariance matrix if it does not exist
+ if (!trackParam->CovariancesExist()) {
+ cout<<"W-AliMUONTrackExtrap::LinearExtrapToZCov: Covariance matrix does not exist"<<endl;
+ // Extrapolate linearly track parameters to "zEnd"
+ LinearExtrapToZ(trackParam,zEnd);
+ return;
}
+ // 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);
+
+ // Calculate the jacobian related to the track parameters linear extrapolation to "zEnd"
+ TMatrixD jacob(5,5);
+ jacob.UnitMatrix();
+ jacob(0,1) = dZ;
+ jacob(2,3) = dZ;
+
+ // Extrapolate track parameter covariances to "zEnd"
+ TMatrixD tmp(trackParam->GetCovariances(),TMatrixD::kMultTranspose,jacob);
+ TMatrixD tmp2(jacob,TMatrixD::kMult,tmp);
+ trackParam->SetCovariances(tmp2);
+
+ // Update the propagator if required
+ if (updatePropagator) trackParam->UpdatePropagator(jacob);
}
//__________________________________________________________________________
-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 (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 trackingFailed = 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 ++;
step = TMath::Abs(step);
- AliMUONTrackExtrap::ExtrapOneStepRungekutta(chargeExtrap,step,v3,v3New);
+ if (!AliMUONTrackExtrap::ExtrapOneStepRungekutta(chargeExtrap,step,v3,v3New)) {
+ trackingFailed = kTRUE;
+ break;
+ }
residue = zEnd - v3New[2];
step *= dZ/(v3New[2]-trackParam->GetZ());
} while (residue*dZ < 0 && TMath::Abs(residue) > fgkRungeKuttaMaxResidue);
- RecoverTrackParam(v3New, chargeExtrap * forwardBackward, trackParam);
+
+ if (trackingFailed) break;
+ else 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 (trackingFailed || 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;
+
+ }
+
}
//__________________________________________________________________________
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, 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 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);
+ Double_t direction[5] = {-1.,-1.,1.,1.,-1.};
for (Int_t i=0; i<5; i++) {
// Skip jacobian calculation for parameters with no associated error
if (kParamCov(i,i) <= 0.) continue;
for (Int_t j=0; j<5; j++) {
if (j==i) {
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
+ dParam(j,0) *= TMath::Sign(1.,direction[j]*paramSave(j,0)); // variation always in the same direction
} else dParam(j,0) = 0.;
}
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;
- // 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
// 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 momentum related covariances if B!=0
+ if (fgFieldON) {
+ // compute derivative d(q/Pxy) / dSlopeX and d(q/Pxy) / dSlopeY
+ 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);
+ // 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);
// 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);
- LinearExtrapToZ(param,zB);
+ LinearExtrapToZCov(param,zB);
// compute track parameters at vertex
TMatrixD newParam(5,1);
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 muMass = TDatabasePDG::Instance()->GetParticle("mu-")->Mass(); // GeV
+ Double_t p = param->P();
+ Double_t e = TMath::Sqrt(p*p + muMass*muMass);
+ Double_t eCorr = e + eLoss;
+ Double_t pCorr = TMath::Sqrt(eCorr*eCorr - muMass*muMass);
Double_t nonBendingSlope = param->GetNonBendingSlope();
Double_t bendingSlope = param->GetBendingSlope();
- param->SetInverseBendingMomentum(param->GetCharge() / (param->P() + eLoss) *
+ param->SetInverseBendingMomentum(param->GetCharge() / pCorr *
TMath::Sqrt(1.0 + nonBendingSlope*nonBendingSlope + bendingSlope*bendingSlope) /
TMath::Sqrt(1.0 + bendingSlope*bendingSlope));
+ // Add effects of energy loss fluctuation to covariances
+ newParamCov(4,4) += eCorr * eCorr / pCorr / pCorr * sigmaELoss2;
+
// Get new parameter covariances in (X, SlopeX, Y, SlopeY, q/Pyz) coordinate system
CovP2Cov(param->GetParameters(),newParamCov);
Double_t x0 = 0.; // radiation-length (cm-1)
Double_t atomicA = 0.; // A of material
Double_t atomicZ = 0.; // Z of material
+ Double_t atomicZoverA = 0.; // Z/A of material
Double_t localPathLength = 0;
Double_t remainingPathLength = pathLength;
+ Double_t sigmaELoss = 0.;
Double_t zB = trackXYZIn[2];
Double_t zE, dzB, dzE;
do {
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(material->IsMixture()){
+ TGeoMixture * mixture = (TGeoMixture*)material;
+ atomicZoverA = 0.;
+ Double_t sum = 0.;
+ for (Int_t iel=0;iel<mixture->GetNelements();iel++){
+ sum += mixture->GetWmixt()[iel];
+ atomicZoverA += mixture->GetZmixt()[iel]*mixture->GetWmixt()[iel]/mixture->GetAmixt()[iel];
+ }
+ atomicZoverA/=sum;
+ }
+ else atomicZoverA = atomicZ/atomicA;
// Get path length within this material
gGeoManager->FindNextBoundary(remainingPathLength);
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);
+ totalELoss += BetheBloch(pTotal, localPathLength, rho, atomicZ, atomicZoverA);
+ sigmaELoss += EnergyLossFluctuation(pTotal, localPathLength, rho, atomicZoverA);
// prepare next step
zB = zE;
} while (remainingPathLength > TGeoShape::Tolerance());
meanRho /= pathLength;
+ sigmaELoss2 = sigmaELoss*sigmaELoss;
return kTRUE;
}
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.;
-
- // 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);
+ Double_t covCorrSlope = (x0 > 0.) ? signedPathLength * theta02 / 2. : 0.;
// Set MCS covariance matrix
TMatrixD newParamCov(param->GetCovariances());
// 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 momentum related covariances if B!=0
+ if (fgFieldON) {
+ // compute derivative d(q/Pxy) / dSlopeX and d(q/Pxy) / dSlopeY
+ 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);
+ // 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);
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)) {
+ Double_t pathLength, f0, f1, f2, meanRho, totalELoss, sigmaELoss2;
+ if (!GetAbsorberCorrectionParam(trackXYZIn,trackXYZOut,pTot,pathLength,f0,f1,f2,meanRho,totalELoss,sigmaELoss2)) {
cout<<"E-AliMUONTrackExtrap::ExtrapToVertex: Unable to take into account the absorber effects"<<endl;
if (trackParam->CovariancesExist()) ExtrapToZCov(trackParam,zVtx);
else ExtrapToZ(trackParam,zVtx);
if (correctForEnergyLoss) {
// Correct for multiple scattering and energy loss
- CorrectELossEffectInAbsorber(trackParam, 0.5*deltaP, 0.5*sigmaDeltaP2);
+ CorrectELossEffectInAbsorber(trackParam, 0.5*totalELoss, 0.5*sigmaELoss2);
CorrectMCSEffectInAbsorber(trackParam, xVtx, yVtx, zVtx, errXVtx, errYVtx,
trackXYZIn[2], pathLength, f0, f1, f2);
- CorrectELossEffectInAbsorber(trackParam, 0.5*deltaP, 0.5*sigmaDeltaP2);
+ CorrectELossEffectInAbsorber(trackParam, 0.5*totalELoss, 0.5*sigmaELoss2);
} 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);
+ CorrectELossEffectInAbsorber(trackParam, 0.5*totalELoss, 0.5*sigmaELoss2);
+ AddMCSEffectInAbsorber(trackParam, -pathLength, f0, f1, f2); // (spectro. (z<0))
ExtrapToZCov(trackParam, trackXYZIn[2]);
- CorrectELossEffectInAbsorber(trackParam, 0.5*deltaP, 0.5*sigmaDeltaP2);
+ 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);
}
Double_t pathLength, f0, f1, f2, meanRho, totalELoss, sigmaELoss2;
GetAbsorberCorrectionParam(trackXYZIn,trackXYZOut,pTot,pathLength,f0,f1,f2,meanRho,totalELoss,sigmaELoss2);
- return totalELoss;
+ // total momentum corrected for energy loss
+ Double_t muMass = TDatabasePDG::Instance()->GetParticle("mu-")->Mass(); // GeV
+ Double_t e = TMath::Sqrt(pTot*pTot + muMass*muMass);
+ Double_t eCorr = e + totalELoss;
+ Double_t pTotCorr = TMath::Sqrt(eCorr*eCorr - muMass*muMass);
+
+ return pTotCorr - pTot;
}
//__________________________________________________________________________
-Double_t AliMUONTrackExtrap::BetheBloch(Double_t pTotal, Double_t pathLength, Double_t rho, Double_t atomicA, Double_t atomicZ)
+Double_t AliMUONTrackExtrap::BetheBloch(Double_t pTotal, Double_t pathLength, Double_t rho, Double_t atomicZ, Double_t atomicZoverA)
{
/// 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 muMass = TDatabasePDG::Instance()->GetParticle("mu-")->Mass(); // GeV
- Double_t w = k * rho * pathLength * atomicZ / atomicA / beta2;
+ // mean exitation energy (GeV)
+ Double_t i;
+ if (atomicZ < 13) i = (12. * atomicZ + 7.) * 1.e-9;
+ else i = (9.76 * atomicZ + 58.8 * TMath::Power(atomicZ,-0.19)) * 1.e-9;
- 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);
+ return pathLength * rho * AliExternalTrackParam::BetheBlochGeant(pTotal/muMass, rho, 0.20, 3.00, i, atomicZoverA);
}
//__________________________________________________________________________
-Double_t AliMUONTrackExtrap::EnergyLossFluctuation2(Double_t pTotal, Double_t pathLength, Double_t rho, Double_t atomicA, Double_t atomicZ)
+Double_t AliMUONTrackExtrap::EnergyLossFluctuation(Double_t pTotal, Double_t pathLength, Double_t rho, Double_t atomicZoverA)
{
/// 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 muMass = TDatabasePDG::Instance()->GetParticle("mu-")->Mass(); // 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)
+ Double_t fwhm = 2. * k * rho * pathLength * atomicZoverA / beta2; // FWHM of the energy loss Landau distribution
+ Double_t sigma = fwhm / TMath::Sqrt(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;
+ return sigma;
}
//__________________________________________________________________________
}
//__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapOneStepHelix(Double_t charge, Double_t step, Double_t *vect, Double_t *vout)
+void AliMUONTrackExtrap::ExtrapOneStepHelix(Double_t charge, Double_t step, const Double_t *vect, Double_t *vout)
{
/// <pre>
/// ******************************************************************
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)
+void AliMUONTrackExtrap::ExtrapOneStepHelix3(Double_t field, Double_t step, const Double_t *vect, Double_t *vout)
{
/// <pre>
/// ******************************************************************
}
//__________________________________________________________________________
-void AliMUONTrackExtrap::ExtrapOneStepRungekutta(Double_t charge, Double_t step, Double_t* vect, Double_t* vout)
+Bool_t AliMUONTrackExtrap::ExtrapOneStepRungekutta(Double_t charge, Double_t step, const Double_t* vect, Double_t* vout)
{
/// <pre>
/// ******************************************************************
/// </pre>
Double_t h2, h4, f[4];
- Double_t xyzt[3], a, b, c, ph,ph2;
+ Double_t xyzt[3] = {FLT_MAX, FLT_MAX, FLT_MAX};
+ Double_t a, b, c, ph,ph2;
Double_t secxs[4],secys[4],seczs[4],hxp[3];
Double_t g1, g2, g3, g4, g5, g6, ang2, dxt, dyt, dzt;
Double_t est, at, bt, ct, cba;
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;
vout[5] = cba*c;
rest = step - tl;
if (step < 0.) rest = -rest;
- if (rest < 1.e-5*TMath::Abs(step)) return;
+ if (rest < 1.e-5*TMath::Abs(step)) return kTRUE;
} while(1);
// angle too big, use helix
+ cout<<"W-AliMUONTrackExtrap::ExtrapOneStepRungekutta: Ruge-Kutta failed: switch to helix"<<endl;
f1 = f[0];
f2 = f[1];
f3 = f[2];
f4 = TMath::Sqrt(f1*f1+f2*f2+f3*f3);
+ if (f4 < 1.e-10) {
+ cout<<"E-AliMUONTrackExtrap::ExtrapOneStepRungekutta: magnetic field at (";
+ cout<<xyzt[0]<<", "<<xyzt[1]<<", "<<xyzt[2]<<") = "<<f4<<": giving up"<<endl;
+ return kFALSE;
+ }
rho = -f4*pinv;
tet = rho * step;
vout[kipy] = vect[kipy] + g4*vect[kipy] + g5*hxp[1] + g6*f2;
vout[kipz] = vect[kipz] + g4*vect[kipz] + g5*hxp[2] + g6*f3;
- return;
+ return kTRUE;
}
-//___________________________________________________________
-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;
-}
git://git.uio.no / u / mrichter / AliRoot.git / blobdiff