Pair generator

Markus Koehler

diff --git a/EVGEN/AliGenPairFlat.cxx b/EVGEN/AliGenPairFlat.cxx
new file mode 100644 (file)
index 0000000..ac801fd
--- /dev/null
+++ b/EVGEN/AliGenPairFlat.cxx
@@ -0,0 +1,245 @@
+/**************************************************************************
+ * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
+ *                                                                        *
+ * Author: The ALICE Off-line Project.                                    *
+ * Contributors are mentioned in the code where appropriate.              *
+ *                                                                        *
+ * Permission to use, copy, modify and distribute this software and its   *
+ * documentation strictly for non-commercial purposes is hereby granted   *
+ * without fee, provided that the above copyright notice appears in all   *
+ * copies and that both the copyright notice and this permission notice   *
+ * appear in the supporting documentation. The authors make no claims     *
+ * about the suitability of this software for any purpose. It is          *
+ * provided "as is" without express or implied warranty.                  *
+ **************************************************************************/
+
+
+// Generator for particle pairs in a preset
+// kinematic range 
+// ranges can be set for invariant mass, pair pT, pair rapidity
+// and pair azimuth
+
+//
+// Comments and suggestions: markus.konrad.kohler@cern.ch
+//
+
+#include "TPDGCode.h"
+#include <TDatabasePDG.h>
+#include "AliGenEventHeader.h"
+#include "TF1.h"
+
+#include "AliGenPairFlat.h"
+
+ClassImp(AliGenPairFlat)
+
+//_____________________________________________________________________________
+AliGenPairFlat::AliGenPairFlat()
+    :AliGenerator(), 
+     fPairNpart(10),
+     fPairYMin(-10.),
+     fPairYMax(10.),
+     fPairPhiMin(0.),
+     fPairPhiMax(TMath::TwoPi()),
+     fPairPtMin(0.001),
+     fPairPtMax(50.),
+     fPairMassMin(0.),
+     fPairMassMax(10.),
+     fLegPdg1(11),
+     fLegPdg2(-11),
+     fAlpha(0.),
+     fDebug(0)
+{
+  //
+  // Default constructor
+  //
+}
+
+//_____________________________________________________________________________
+void AliGenPairFlat::Generate()
+{
+  //
+  // Generate a random pair of particles
+  //
+  
+    Float_t polar[3]= {0,0,0};
+    Float_t origin[3];
+    Float_t time;
+
+    Float_t p[3];
+    Int_t i, j, nt;
+    Double_t phi, y, mass, mt, e, pt;
+    Float_t weight = 1.;
+    Double_t  pt1, pt2, y1, y2;
+
+    TLorentzVector mother, dau1, dau2;
+    Float_t random[6];
+
+//    TF1* fPol = new TF1("fPol","1.+[0]*x*x",-1.,1.);
+    TF1 fPol("fPol","1.+[0]*x*x",-1.,1.);
+    fPol.SetParameter(0,fAlpha);
+
+
+    for (j=0;j<3;j++) origin[j]=fOrigin[j];
+    time = fTimeOrigin;
+    if(fVertexSmear==kPerEvent) {
+       Vertex();
+       for (j=0;j<3;j++) origin[j]=fVertex[j];
+       time = fTime;
+     }
+
+       printf("\n\n------------------GENERATOR SETTINGS------------------\n\n");
+       printf("You choosed for the mother the Mass range %f - %f     \n",fPairMassMin,fPairMassMax);
+       printf("You choosed for the mother the transverse Momentum range %f - %f \n",fPairPtMin,fPairPtMax);
+       printf("You choosed for the mother the Phi range %f - %f \n",fPairPhiMin,fPairPhiMax);
+       printf("The Particle will decay in (pdg) %i and %i\n \n",fLegPdg1, fLegPdg2);
+       printf("The rest Mass of first daughter (%s) is %f \n",
+       TDatabasePDG::Instance()->GetParticle(TMath::Abs(fLegPdg1))->GetTitle(),
+       TDatabasePDG::Instance()->GetParticle(TMath::Abs(fLegPdg1))->Mass());
+       printf("The rest Mass of second daughter (%s) is %f \n",
+       TDatabasePDG::Instance()->GetParticle(TMath::Abs(fLegPdg2))->GetTitle(),
+       TDatabasePDG::Instance()->GetParticle(TMath::Abs(fLegPdg2))->Mass());
+       printf("polarization factor is alpha == %lf \n",fAlpha);
+       printf("vertex is at x == %f || y == %f || z == %f   \n",origin[0],origin[1],origin[2]);
+       printf("\n----------------------------------------------------------\n");
+
+
+    for(i=0;i<fPairNpart;i++) {
+
+       // mother properties
+       Rndm(random,4);
+       mass    = fPairMassMin+random[0]*(fPairMassMax-fPairMassMin);
+       pt      = fPairPtMin+random[1]*(fPairPtMax-fPairPtMin);
+       y       = fPairYMin+random[2]*(fPairYMax-fPairYMin);
+       phi     = fPairPhiMin+random[3]*(fPairPhiMax-fPairPhiMin);
+
+        mt     = TMath::Sqrt(pt*pt + mass*mass);
+       p[0]    = pt*TMath::Cos(phi);
+       p[1]    = pt*TMath::Sin(phi);
+       p[2]    = mt*TMath::SinH(y);
+       e       = mt*TMath::CosH(y);
+
+       mother.SetPxPyPzE(p[0],p[1],p[2],e); 
+       
+
+         if (fDebug == 2)    printf("p = (%+11.4e,%+11.4e,%+11.4e) GeV || pt = %+11.4e || y =  %+11.4e || weight=%+11.4e || E= %+11.4e\n",p[0],p[1],p[2],pt, y,weight,e);
+
+       //decay procedure
+       if(!Decay(mother,dau1,dau2,fPol))continue;
+
+       pt1 = dau1.Pt();
+       pt2 = dau2.Pt();
+       y1 = dau1.Rapidity();
+       y2 = dau2.Rapidity();
+
+       //first daughter
+       p[0] = dau1.Px();
+       p[1] = dau1.Py();
+       p[2] = dau1.Pz();
+       e = dau1.E();
+
+       if(fVertexSmear==kPerTrack) {
+           Rndm(random,6);
+           for (j=0;j<3;j++) {
+               origin[j]=fOrigin[j]+fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
+                   TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
+           }
+
+           Rndm(random,2);
+           time = fTimeOrigin + fOsigma[2]/TMath::Ccgs()*
+             TMath::Cos(2*random[0]*TMath::Pi())*
+             TMath::Sqrt(-2*TMath::Log(random[1]));
+       }
+
+       PushTrack(fTrackIt,-1,fLegPdg1,p,origin,polar,time,kPPrimary,nt, weight);
+       if (fDebug == 2) printf("dau1-->id=%+3d, p = (%+11.4e,%+11.4e,%+11.4e) GeV || pt = %+11.4e || weight=%+11.4e || E= %+11.4e\n",fLegPdg1,p[0],p[1],p[2],pt1,weight,e);
+
+       //second daughter
+       p[0] = dau2.Px();
+       p[1] = dau2.Py();
+       p[2] = dau2.Pz();
+       e = dau2.E();
+
+       if(fVertexSmear==kPerTrack) {
+           Rndm(random,6);
+           for (j=0;j<3;j++) {
+               origin[j]=fOrigin[j]+fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
+                   TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
+           }
+
+           Rndm(random,2);
+           time = fTimeOrigin + fOsigma[2]/TMath::Ccgs()*
+             TMath::Cos(2*random[0]*TMath::Pi())*
+             TMath::Sqrt(-2*TMath::Log(random[1]));
+       }
+
+       PushTrack(fTrackIt,-1,fLegPdg2,p,origin,polar,time,kPPrimary,nt,weight);
+      if (fDebug == 2) printf("dau2-->id=%+3d, p = (%+11.4e,%+11.4e,%+11.4e) GeV || pt = %+11.4e || weight=%+11.4e || E= %+11.4e\n",fLegPdg2,p[0],p[1],p[2],pt2, weight,e);
+
+    }//particle loop
+
+}
+
+//_____________________________________________________________________________
+
+void AliGenPairFlat::Init()
+{
+       //
+       // Init
+       //
+
+       printf("AliGenPairFlat::Init() not implemented!!!\n");
+
+}
+
+
+//_____________________________________________________________________________
+
+
+Bool_t AliGenPairFlat::Decay(TLorentzVector mother, TLorentzVector &dau1, TLorentzVector &dau2, TF1 polfactor)
+{
+       //
+       // decay procedure
+       //
+
+       Double_t mp, md1, md2, ed1, ed2, pd1, pd2;
+       Double_t costheta, sintheta, phi;
+
+       mp = mother.M();
+       md1 = TDatabasePDG::Instance()->GetParticle(TMath::Abs(fLegPdg1))->Mass();
+       md2 = TDatabasePDG::Instance()->GetParticle(TMath::Abs(fLegPdg2))->Mass();
+
+       if(mp < md1+md2){
+       printf("Daughters are heavier than Mother!! Check Kinematics!! \n");
+       return 0;
+       }
+
+  ed1 = (mp*mp + md1*md1 - md2*md2)/(2.*mp);
+  ed2 = mp-ed1;
+  pd1 = TMath::Sqrt((ed1+md1)*(ed1-md1));
+  pd2 = TMath::Sqrt((mp*mp-(md1+md2)*(md1+md2))*(mp*mp -(md1-md2)*(md1-md2)))/(2.*mp);
+
+  costheta = polfactor.GetRandom(); //polarization
+  sintheta = TMath::Sqrt((1.+costheta)*(1.-costheta));
+  phi      = 2.0*TMath::Pi()*gRandom->Rndm();
+
+       dau1.SetPxPyPzE(pd1*sintheta*TMath::Cos(phi), 
+                       pd1*sintheta*TMath::Sin(phi), 
+                       pd1*costheta,
+                       ed1); 
+
+       dau2.SetPxPyPzE((-1.)*pd1*sintheta*TMath::Cos(phi),
+                       (-1.)*pd1*sintheta*TMath::Sin(phi), 
+                       (-1.)*pd1*costheta,
+                       ed2);
+
+       TVector3 boost = mother.BoostVector();
+
+       dau1.Boost(boost);
+       dau2.Boost(boost);
+
+  return 1;
+
+}
+
+
+

diff --git a/EVGEN/AliGenPairFlat.h b/EVGEN/AliGenPairFlat.h
new file mode 100644 (file)
index 0000000..2bd9abe
--- /dev/null
+++ b/EVGEN/AliGenPairFlat.h
@@ -0,0 +1,61 @@
+#ifndef ALIGENPAIRFLAT_H
+#define ALIGENPAIRFLAT_H
+
+
+// Generator for particle pairs in a preset
+// kinematic range 
+// ranges can be set for invariant mass, pair pT, pair rapidity
+// and pair azimuth
+
+// Comments and suggestions: markus.konrad.kohler@cern.ch
+
+
+#include "AliGenerator.h"
+
+class TF1;
+
+class AliGenPairFlat : public AliGenerator
+{
+ public:
+  AliGenPairFlat();
+  virtual ~AliGenPairFlat(){ }
+  virtual void Generate();
+  virtual void Init();
+
+  virtual void SetPairNPart(Int_t npart) {fPairNpart=npart;}
+  virtual void SetPairYRange(Float_t Ymin, Float_t Ymax)
+      {fPairYMin = Ymin; fPairYMax = Ymax;}
+  virtual void SetPairPhiRange(Float_t phimin, Float_t phimax)
+      {fPairPhiMin = phimin; fPairPhiMax = phimax;}
+  virtual void SetPairPtRange(Float_t ptmin, Float_t ptmax)
+      {fPairPtMin = ptmin; fPairPtMax = ptmax;}
+  virtual void SetPairMassRange(Float_t massmin, Float_t massmax)
+      {fPairMassMin = massmin; fPairMassMax = massmax;}
+  virtual void SetLegPdg(Int_t pdg1, Int_t pdg2)
+      {fLegPdg1 = pdg1; fLegPdg2 = pdg2;}
+  virtual void SetPolarization(Float_t Alpha)
+      {fAlpha = Alpha;}
+  void SetDebug(Int_t debug) {fDebug=debug;}
+
+protected:
+
+  Int_t   fPairNpart;                  //Number of generated pairs
+  Float_t fPairYMin;           // Minimum eta 
+  Float_t fPairYMax;           // Maximum eta
+  Float_t fPairPhiMin;         // Minimum phi 
+  Float_t fPairPhiMax;         // Maximum phi
+  Float_t fPairPtMin;                  // Minimum pt 
+  Float_t fPairPtMax;                  // Maximum pt
+  Float_t fPairMassMin;                // Minimum mass 
+  Float_t fPairMassMax;        // Maximum mass
+  Int_t   fLegPdg1;            // pdg code of first daughter
+  Int_t   fLegPdg2;            // pdg code of second daughter
+  Float_t fAlpha;              // Polarization factor
+  Int_t   fDebug;              // debug level
+
+  Bool_t Decay(TLorentzVector mother, TLorentzVector &dau1, TLorentzVector &dau2 , TF1 fPol);
+
+  ClassDef(AliGenPairFlat,1) // Flat random pair generator
+};
+
+#endif

diff --git a/EVGEN/CMakelibEVGEN.pkg b/EVGEN/CMakelibEVGEN.pkg
index c0604f0c3647dd9fbe66aea0221a999bb19c503b..5a96cb56d40408adb67607a1bf46d467ba99dcb2 100644 (file)
--- a/EVGEN/CMakelibEVGEN.pkg
+++ b/EVGEN/CMakelibEVGEN.pkg
@@ -33,6 +33,7 @@ set ( SRCS
   AliGenFixed.cxx 
   AliGenCocktail.cxx 
   AliGenCocktailAfterBurner.cxx 
+  AliGenPairFlat.cxx
   AliGenLib.cxx 
   AliGenMUONlib.cxx 
   AliGenHMPIDlib.cxx 

diff --git a/EVGEN/EVGENLinkDef.h b/EVGEN/EVGENLinkDef.h
index 8b0400d994f737552554444bdcad932e821e9119..573e81ae5c8083b6f7419386177544f8eb030703 100644 (file)
--- a/EVGEN/EVGENLinkDef.h
+++ b/EVGEN/EVGENLinkDef.h
@@ -19,6 +19,7 @@
 #pragma link C++ class  AliGenThetaSlice+;
 #pragma link C++ class  AliGenParam+;
 #pragma link C++ class  AliGenCocktail+;
+#pragma link C++ class  AliGenPairFlat+;
 #pragma link C++ class  AliGenMUONCocktail+;
 #pragma link C++ class  AliGenMUONCocktailpp+;
 #pragma link C++ class  AliGenEMCocktail+;