New parameterization of the dE/dx in the ITS standalone tracks (Leonardo)

diff --git a/STEER/STEERBase/AliITSPIDResponse.cxx b/STEER/STEERBase/AliITSPIDResponse.cxx
index bcbe2d27e39117726b5cc2ba31a7796170f6692a..e3828fbcb8c984f16e3c4556796e9e79478f69ae 100644 (file)
--- a/STEER/STEERBase/AliITSPIDResponse.cxx
+++ b/STEER/STEERBase/AliITSPIDResponse.cxx
@@ -42,12 +42,21 @@ AliITSPIDResponse::AliITSPIDResponse(Bool_t isMC):
     fBBtpcits[2]=0.905;
     fBBtpcits[3]=1.2;
     fBBtpcits[4]=6.6;
-    fBBsa[0]=2.73198E7;
+    fBBsa[0]=2.73198E7; //pure PHOBOS parameterization
     fBBsa[1]=6.92389;
     fBBsa[2]=1.90088E-6;
     fBBsa[3]=1.90088E-6;
     fBBsa[4]=3.40644E-7;
-    fBBsaElectron[0]=4.05799E6;
+    fBBsaHybrid[0]=1.43505E7;  //PHOBOS+Polinomial parameterization
+    fBBsaHybrid[1]=49.3402;
+    fBBsaHybrid[2]=1.77741E-7;
+    fBBsaHybrid[3]=1.77741E-7;
+    fBBsaHybrid[4]=1.01311E-7;
+    fBBsaHybrid[5]=77.2777;
+    fBBsaHybrid[6]=33.4099;
+    fBBsaHybrid[7]=46.0089;
+    fBBsaHybrid[8]=-2.26583;
+    fBBsaElectron[0]=4.05799E6;  //electrons in the ITS
     fBBsaElectron[1]=38.5713;
     fBBsaElectron[2]=1.46462E-7;
     fBBsaElectron[3]=1.46462E-7;
@@ -64,12 +73,21 @@ AliITSPIDResponse::AliITSPIDResponse(Bool_t isMC):
     fBBtpcits[2]=1.00;
     fBBtpcits[3]=0.964;
     fBBtpcits[4]=2.59;
-    fBBsa[0]=2.02078E7;
+    fBBsa[0]=2.02078E7; //pure PHOBOS parameterization
     fBBsa[1]=14.0724;
     fBBsa[2]=3.84454E-7;
     fBBsa[3]=3.84454E-7;
     fBBsa[4]=2.43913E-7;
-    fBBsaElectron[0]=2.26807E6;
+    fBBsaHybrid[0]=1.05381E7; //PHOBOS+Polinomial parameterization
+    fBBsaHybrid[1]=89.3933;
+    fBBsaHybrid[2]=2.4831E-7;
+    fBBsaHybrid[3]=2.4831E-7;
+    fBBsaHybrid[4]=7.80591E-8;
+    fBBsaHybrid[5]=62.9214;
+    fBBsaHybrid[6]=32.347;
+    fBBsaHybrid[7]=58.7661;
+    fBBsaHybrid[8]=-3.39869;
+    fBBsaElectron[0]=2.26807E6; //electrons in the ITS
     fBBsaElectron[1]=99.985;
     fBBsaElectron[2]=0.000714841;
     fBBsaElectron[3]=0.000259585;
@@ -127,6 +145,8 @@ Double_t AliITSPIDResponse::Bethe(Double_t p, Double_t mass, Bool_t isSA) const
   Double_t bg=p/mass;
   Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
   Double_t gamma=bg/beta;
+  Double_t bb=1.;
+  
   Double_t par[5];
   if(isSA){
     if(mass>0.0005 && mass<0.00052){
@@ -145,13 +165,48 @@ Double_t AliITSPIDResponse::Bethe(Double_t p, Double_t mass, Bool_t isSA) const
   else
     eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
   
-  Double_t bb=0.;
   if(gamma>=0. && beta>0.){
     bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff;
   }
   return bb;
 }
 
+//_________________________________________________________________________
+Double_t AliITSPIDResponse::BetheITSsaHybrid(Double_t p, Double_t mass) const {
+  //
+  // returns AliExternalTrackParam::BetheBloch normalized to 
+  // fgMIP at the minimum. The PHOBOS parameterization is used for beta*gamma>0.76. 
+  // For beta*gamma<0.76 a polinomial function is used
+  
+  Double_t bg=p/mass;
+  Double_t beta = bg/TMath::Sqrt(1.+ bg*bg);
+  Double_t gamma=bg/beta;
+  Double_t bb=1.;
+  
+  Double_t par[9];
+  //parameters for pi, K, p
+  for(Int_t ip=0; ip<9;ip++) par[ip]=fBBsaHybrid[ip];
+  //if it is an electron the PHOBOS part of the parameterization is tuned for e
+  //in the range used for identification beta*gamma is >0.76 for electrons
+  //To be used only between 100 and 160 MeV/c
+  if(mass>0.0005 && mass<0.00052)for(Int_t ip=0; ip<5;ip++) par[ip]=fBBsaElectron[ip]; 
+  
+  if(gamma>=0. && beta>0. && bg>0.1){
+    if(bg>0.76){//PHOBOS
+      Double_t eff=1.0;
+      if(bg<par[2])
+       eff=(bg-par[3])*(bg-par[3])+par[4];
+      else
+       eff=(par[2]-par[3])*(par[2]-par[3])+par[4];
+      
+      bb=(par[1]+2.0*TMath::Log(gamma)-beta*beta)*(par[0]/(beta*beta))*eff;
+    }else{//Polinomial
+      bb=par[5] + par[6]/bg + par[7]/(bg*bg) + par[8]/(bg*bg*bg);
+    }
+  }
+  return bb; 
+}
+
 //_________________________________________________________________________
 Double_t AliITSPIDResponse::GetResolution(Double_t bethe, 
                                          Int_t nPtsForPid, 

diff --git a/STEER/STEERBase/AliITSPIDResponse.h b/STEER/STEERBase/AliITSPIDResponse.h
index 3556220b59715483598f154348207fe4e36049ed..325ee66c8a5006a47276a78f2dbe8818c181dc45 100644 (file)
--- a/STEER/STEERBase/AliITSPIDResponse.h
+++ b/STEER/STEERBase/AliITSPIDResponse.h
@@ -27,12 +27,17 @@ public:
  void SetBetheBlochParamsITSsa(Double_t* param){
    for(Int_t iPar=0; iPar<5; iPar++) fBBsa[iPar]=param[iPar];
  }
+ 
+ void SetBetheBlochHybridParamsITSsa(Double_t* param){
+   for(Int_t iPar=0; iPar<9; iPar++) fBBsaHybrid[iPar]=param[iPar];
+ }
  void SetElectronBetheBlochParamsITSsa(Double_t* param){
    for(Int_t iPar=0; iPar<5; iPar++) fBBsaElectron[iPar]=param[iPar];
  }
 
  Double_t BetheAleph(Double_t p,Double_t mass) const;
  Double_t Bethe(Double_t p, Double_t mass, Bool_t iSA=kFALSE) const;
+ Double_t BetheITSsaHybrid(Double_t p, Double_t mass) const;
  Double_t GetResolution(Double_t bethe, Int_t nPtsForPid=4, Bool_t isSA=kFALSE) const;
  void GetITSProbabilities(Float_t mom, Double_t qclu[4], Double_t condprobfun[AliPID::kSPECIES],Bool_t isMC=kFALSE) const;
  Float_t GetNumberOfSigmas(Float_t mom, Float_t signal, AliPID::EParticleType type, Int_t nPtsForPid=4, Bool_t isSA=kFALSE) const {
@@ -52,13 +57,14 @@ private:
   Double_t fKp3;             // ALEPH BB param 3
   Double_t fKp4;             // ALEPH BB param 4
   Double_t fKp5;             // ALEPH BB param 
-  Double_t  fBBsa[5];         // parameters of BB for SA tracks
-  Double_t  fBBsaElectron[5];         // parameters of BB for SA tracks
+  Double_t  fBBsa[5];        // parameters of BB for SA tracks
+  Double_t  fBBsaHybrid[9];  // parameters of Hybrid BB for SA tracks, PHOB + Polinomial al low beta*gamma
+  Double_t  fBBsaElectron[5];// parameters of electron BB for SA tracks
   Double_t  fBBtpcits[5];     // parameters of BB for TPC+ITS tracks
   Float_t  fResolSA[5];      // resolutions vs. n. of SDD/SSD points
   Float_t  fResolTPCITS[5];  // resolutions vs. n. of SDD/SSD points
 
-  ClassDef(AliITSPIDResponse,3)   // ITS PID class
+  ClassDef(AliITSPIDResponse,4)   // ITS PID class
 };
 
 #endif