Introducing a new CorrectForMeanMaterial function with a different meaning of the...

diff --git a/STEER/AliExternalTrackParam.cxx b/STEER/AliExternalTrackParam.cxx
index addbe0be95bf11053b065fa3638cc81c3ae42258..79a27dfaabbe43270f93912dea5a1689bc6c3ca1 100644 (file)
--- a/STEER/AliExternalTrackParam.cxx
+++ b/STEER/AliExternalTrackParam.cxx
@@ -181,9 +181,63 @@ Double_t AliExternalTrackParam::GetLinearD(Double_t xv,Double_t yv) const {
   return -d;
 }
 
+Bool_t AliExternalTrackParam::CorrectForMeanMaterial
+(Double_t xOverX0,  Double_t xTimesRho, Double_t mass, 
+Double_t (*Bethe)(Double_t)) {
+  //------------------------------------------------------------------
+  // This function corrects the track parameters for the crossed material.
+  // "xOverX0"   - X/X0, the thickness in units of the radiation length.
+  // "xTimesRho" - is the product length*density (g/cm^2). 
+  // "mass" - the mass of this particle (GeV/c^2).
+  //------------------------------------------------------------------
+  Double_t &fP2=fP[2];
+  Double_t &fP3=fP[3];
+  Double_t &fP4=fP[4];
+
+  Double_t &fC22=fC[5];
+  Double_t &fC33=fC[9];
+  Double_t &fC43=fC[13];
+  Double_t &fC44=fC[14];
+
+  Double_t p=GetP();
+  Double_t p2=p*p;
+  Double_t beta2=p2/(p2 + mass*mass);
+  xOverX0*=TMath::Sqrt((1.+ fP3*fP3)/(1.- fP2*fP2));
+
+  //Multiple scattering******************
+  if (xOverX0 != 0) {
+     Double_t theta2=14.1*14.1/(beta2*p2*1e6)*TMath::Abs(xOverX0);
+     //Double_t theta2=1.0259e-6*14*14/28/(beta2*p2)*TMath::Abs(d)*9.36*2.33;
+     fC22 += theta2*(1.- fP2*fP2)*(1. + fP3*fP3);
+     fC33 += theta2*(1. + fP3*fP3)*(1. + fP3*fP3);
+     fC43 += theta2*fP3*fP4*(1. + fP3*fP3);
+     fC44 += theta2*fP3*fP4*fP3*fP4;
+  }
+
+  //Energy losses************************
+  if ((xTimesRho != 0.) && (beta2 < 1.)) {
+     Double_t dE=Bethe(beta2)*xTimesRho;
+     Double_t e=TMath::Sqrt(p2 + mass*mass);
+     if ( TMath::Abs(dE) > 0.3*e ) return kFALSE; //30% energy loss is too much!
+     fP4*=(1.- e/p2*dE);
+
+     // Approximate energy loss fluctuation (M.Ivanov)
+     const Double_t knst=0.07; // To be tuned.  
+     Double_t sigmadE=knst*TMath::Sqrt(TMath::Abs(dE)); 
+     fC44+=((sigmadE*e/p2*fP4)*(sigmadE*e/p2*fP4)); 
+ 
+  }
+
+  return kTRUE;
+}
+
+
 Bool_t AliExternalTrackParam::CorrectForMaterial
 (Double_t d,  Double_t x0, Double_t mass, Double_t (*Bethe)(Double_t)) {
   //------------------------------------------------------------------
+  //                    Deprecated function !   
+  //       Better use CorrectForMeanMaterial instead of it.
+  //
   // This function corrects the track parameters for the crossed material
   // "d"    - the thickness (fraction of the radiation length)
   // "x0"   - the radiation length (g/cm^2) 

diff --git a/STEER/AliExternalTrackParam.h b/STEER/AliExternalTrackParam.h
index e287b9882f1bfc9fca507bf8a0a12cd8e21e5516..eb7650deaa044444039b78f1a88e5c8944739450 100644 (file)
--- a/STEER/AliExternalTrackParam.h
+++ b/STEER/AliExternalTrackParam.h
@@ -87,8 +87,8 @@ class AliExternalTrackParam: public TObject {
   void GetDZ(Double_t x,Double_t y,Double_t z,Double_t b,Float_t dz[2]) const; 
   Double_t GetD(Double_t xv, Double_t yv, Double_t b) const; 
   Double_t GetLinearD(Double_t xv, Double_t yv) const; 
-  Bool_t CorrectForMaterial(Double_t d, Double_t x0, Double_t mass,
-                           Double_t (*f)(Double_t)=ApproximateBetheBloch);
+  Bool_t CorrectForMeanMaterial(Double_t xOverX0, Double_t xTimesRho, 
+        Double_t mass, Double_t (*f)(Double_t)=ApproximateBetheBloch);
   Double_t GetPredictedChi2(Double_t p[2],Double_t cov[3]) const;
 
   Double_t 
@@ -124,6 +124,10 @@ class AliExternalTrackParam: public TObject {
   void Print(Option_t* option = "") const;
   Double_t GetSnpAt(Double_t x,Double_t b) const;
 
+  //Deprecated
+  Bool_t CorrectForMaterial(Double_t d, Double_t x0, Double_t mass,
+                           Double_t (*f)(Double_t)=ApproximateBetheBloch);
+
 protected:
   Double_t &Par(Int_t i) {return fP[i];}
   Double_t &Cov(Int_t i) {return fC[i];}