* provided "as is" without express or implied warranty. *
**************************************************************************/
-/*
-$Log$
-Revision 1.10 2001/04/25 14:50:42 gosset
-Corrections to violations of coding conventions
-
-Revision 1.9 2000/10/16 15:30:40 gosset
-TotalMomentumEnergyLoss:
-correction for change in the absorber composition (JP Cussonneau)
-
-Revision 1.8 2000/10/02 21:28:09 fca
-Removal of useless dependecies via forward declarations
-
-Revision 1.7 2000/10/02 16:58:29 egangler
-Cleaning of the code :
--> coding conventions
--> void Streamers
--> some useless includes removed or replaced by "class" statement
-
-Revision 1.6 2000/09/19 09:49:50 gosset
-AliMUONEventReconstructor package
-* track extrapolation independent from reco_muon.F, use of AliMagF...
-* possibility to use new magnetic field (automatic from generated root file)
-
-Revision 1.5 2000/07/18 16:04:06 gosset
-AliMUONEventReconstructor package:
-* a few minor modifications and more comments
-* a few corrections
- * right sign for Z of raw clusters
- * right loop over chambers inside station
- * symmetrized covariance matrix for measurements (TrackChi2MCS)
- * right sign of charge in extrapolation (ExtrapToZ)
- * right zEndAbsorber for Branson correction below 3 degrees
-* use of TVirtualFitter instead of TMinuit for AliMUONTrack::Fit
-* no parameter for AliMUONTrack::Fit() but more fit parameters in Track object
-
-Revision 1.4 2000/07/03 07:53:31 morsch
-Double declaration problem on HP solved.
-
-Revision 1.3 2000/06/30 10:15:48 gosset
-Changes to EventReconstructor...:
-precision fit with multiple Coulomb scattering;
-extrapolation to vertex with Branson correction in absorber (JPC)
-
-Revision 1.2 2000/06/15 07:58:49 morsch
-Code from MUON-dev joined
-
-Revision 1.1.2.3 2000/06/09 21:03:09 morsch
-Make includes consistent with new file structure.
-
-Revision 1.1.2.2 2000/06/09 12:58:05 gosset
-Removed comment beginnings in Log sections of .cxx files
-Suppressed most violations of coding rules
-
-Revision 1.1.2.1 2000/06/07 14:44:53 gosset
-Addition of files for track reconstruction in C++
-*/
+/* $Id$ */
///////////////////////////////////////////////////
//
//
///////////////////////////////////////////////////
-#include <iostream.h>
+#include <Riostream.h>
#include "AliCallf77.h"
#include "AliMUON.h"
Double_t zAbsorber = 503.0; // to be coherent with the Geant absorber geometry !!!!
// Extrapolates track parameters upstream to the "Z" end of the front absorber
- ExtrapToZ(zAbsorber);
+ ExtrapToZ(zAbsorber); // !!!
// Makes Branson correction (multiple scattering + energy loss)
BransonCorrection();
+ // Makes a simple magnetic field correction through the absorber
+ FieldCorrection(zAbsorber);
}
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, zEndAbsorber;
+ static Double_t zBP1, zBP2, rLimit, thetaLimit, zEndAbsorber;
// zBP1 for outer part and zBP2 for inner part (only at the first call)
if (first) {
first = kFALSE;
zEndAbsorber = 503;
- rLimit = zEndAbsorber * TMath::Tan(3.0 * (TMath::Pi()) / 180.);
- zBP1 = 450;
+ thetaLimit = 3.0 * (TMath::Pi()) / 180.;
+ rLimit = zEndAbsorber * TMath::Tan(thetaLimit);
+ zBP1 = 450; // values close to those calculated with EvalAbso.C
zBP2 = 480;
}
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;
+// Float_t zSmear = zBP - gRandom->Gaus(0.,2.); // !!! possible smearing of Z vertex position
+ Float_t zSmear = zBP;
+
+ pZ = pTotal * zSmear / TMath::Sqrt(xBP * xBP + yBP * yBP + zSmear * zSmear);
+ pX = pZ * xBP / zSmear;
+ pY = pZ * yBP / zSmear;
fBendingSlope = pY / pZ;
fNonBendingSlope = pX / pZ;
pT = TMath::Sqrt(pX * pX + pY * pY);
theta = TMath::ATan2(pT, pZ);
- pTotal =
- TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber);
+ pTotal = TotalMomentumEnergyLoss(thetaLimit, pTotal, theta);
fInverseBendingMomentum = (sign / pTotal) *
TMath::Sqrt(1.0 +
fNonBendingCoor = 0;
fZ= 0;
}
+
//__________________________________________________________________________
-Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t rLimit, Double_t pTotal, Double_t theta, Double_t xEndAbsorber, Double_t yEndAbsorber)
+Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t thetaLimit, Double_t pTotal, Double_t theta)
{
// 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;
- Double_t radiusEndAbsorber2 =
- xEndAbsorber *xEndAbsorber + yEndAbsorber * yEndAbsorber;
- // Parametrization to be redone according to change of absorber material ????
+ // Parametrization to be redone according to change of absorber material ????
// See remark in function BransonCorrection !!!!
// The name is not so good, and there are many arguments !!!!
- if (radiusEndAbsorber2 < rLimit * rLimit) {
- if (pTotal < 15) {
- deltaP = 2.737 + 0.0494 * pTotal - 0.001123 * pTotal * pTotal;
+ if (theta < thetaLimit ) {
+ if (pTotal < 20) {
+ deltaP = 2.5938 + 0.0570 * pTotal - 0.001151 * pTotal * pTotal;
} else {
- deltaP = 3.0643 + 0.01346 *pTotal;
+ deltaP = 3.0714 + 0.011767 *pTotal;
}
- deltaP = 0.63 * deltaP; // !!!! changes in the absorber composition ????
} else {
- if (pTotal < 15) {
- deltaP = 2.1380 + 0.0351 * pTotal - 0.000853 * pTotal * pTotal;
+ if (pTotal < 20) {
+ deltaP = 2.1207 + 0.05478 * pTotal - 0.00145079 * pTotal * pTotal;
} else {
- deltaP = 2.407 + 0.00702 * pTotal;
+ deltaP = 2.6069 + 0.0051705 * pTotal;
}
- deltaP = 0.67 * deltaP; // !!!! changes in the absorber composition ????
}
pTotalCorrected = pTotal + deltaP / TMath::Cos(theta);
return pTotalCorrected;
}
+ //__________________________________________________________________________
+void AliMUONTrackParam::FieldCorrection(Double_t Z)
+{
+ //
+ // 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 / fInverseBendingMomentum);
+ c = TMath::Sign(1.0,fInverseBendingMomentum); // particle charge
+
+ pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope));
+ pX = pZ * fNonBendingSlope;
+ pY = pZ * fBendingSlope;
+ pT = TMath::Sqrt(pX*pX+pY*pY);
+
+ if (pZ <= 0) return;
+ x[2] = Z/2;
+ x[0] = x[2]*fNonBendingSlope;
+ x[1] = x[2]*fBendingSlope;
+
+ // Take magn. field value at position x.
+ gAlice->Field()->Field(x, b);
+ 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*Z/pZ;
+
+ // Rotate momentum around Z axis.
+ pXNew = pX*TMath::Cos(phiShift) - pY*TMath::Sin(phiShift);
+ pYNew = pX*TMath::Sin(phiShift) + pY*TMath::Cos(phiShift);
+
+ fBendingSlope = pYNew / pZ;
+ fNonBendingSlope = pXNew / pZ;
+
+ fInverseBendingMomentum = c / TMath::Sqrt(pYNew*pYNew+pZ*pZ);
+
+}
git://git.uio.no / u / mrichter / AliRoot.git / blobdiff