From 811826d8a73b793e11febd62654f7cd05f448f36 Mon Sep 17 00:00:00 2001
From: morsch <morsch@f7af4fe6-9843-0410-8265-dc069ae4e863>
Date: Mon, 18 Sep 2000 10:41:35 +0000
Subject: [PATCH] Add possibility to use nuclear structure functions from PDF
 library V8.

---
 EVGEN/AliGenPythia.cxx | 20 +++++++++++++++++++-
 EVGEN/AliGenPythia.h   |  5 +++++
 EVGEN/AliPythia.cxx    | 25 +++++++++++++++++++++++++
 EVGEN/AliPythia.h      |  3 +++
 4 files changed, 52 insertions(+), 1 deletion(-)

diff --git a/EVGEN/AliGenPythia.cxx b/EVGEN/AliGenPythia.cxx
index 4f7480a372f..9bd8a6c3edf 100644
--- a/EVGEN/AliGenPythia.cxx
+++ b/EVGEN/AliGenPythia.cxx
@@ -15,6 +15,9 @@
 
 /*
 $Log$
+Revision 1.23  2000/09/14 14:05:40  morsch
+dito
+
 Revision 1.22  2000/09/14 14:02:22  morsch
 - Correct conversion from mm to cm when passing particle vertex to MC.
 - Correct handling of fForceDecay == all.
@@ -83,6 +86,8 @@ AliGenPythia::AliGenPythia(Int_t npart)
 // structure function GRVHO
 //
     fXsection  = 0.;
+    fNucA1=0;
+    fNucA2=0;
     fParentSelect.Set(5);
     fChildSelect.Set(5);
     for (Int_t i=0; i<5; i++) fParentSelect[i]=fChildSelect[i]=0;
@@ -123,6 +128,7 @@ void AliGenPythia::Init()
 
     fPythia->SetCKIN(3,fPtHardMin);
     fPythia->SetCKIN(4,fPtHardMax);    
+    if (fNucA1 > 0 && fNucA2 > 0) fPythia->SetNuclei(fNucA1, fNucA2);  
     fPythia->ProcInit(fProcess,fEnergyCMS,fStrucFunc);
 
     //    fPythia->Pylist(0);
@@ -344,6 +350,8 @@ void AliGenPythia::Generate()
 	    if (jev >= fNpart || fNpart == -1) {
 		fKineBias=Float_t(fNpart)/Float_t(fTrials);
 		printf("\n Trials: %i %i %i\n",fTrials, fNpart, jev);
+// Print x-section summary
+		fPythia->Pystat(1);
 		break;
 	    }
 	}
@@ -475,7 +483,16 @@ Int_t AliGenPythia::CheckPDGCode(Int_t pdgcode)
   //non diffractive state -- return code unchanged
   return pdgcode;
 }
-		  
+
+    
+void AliGenPythia::SetNuclei(Int_t a1, Int_t a2)
+{
+// Treat protons as inside nuclei with mass numbers a1 and a2  
+    fNucA1 = a1;
+    fNucA2 = a2;
+}
+	
+	  
 AliGenPythia& AliGenPythia::operator=(const  AliGenPythia& rhs)
 {
 // Assignment operator
@@ -483,6 +500,7 @@ AliGenPythia& AliGenPythia::operator=(const  AliGenPythia& rhs)
 }
 
 
+
 void AliGenPythia::Streamer(TBuffer &R__b)
 {
    // Stream an object of class AliGenPythia.
diff --git a/EVGEN/AliGenPythia.h b/EVGEN/AliGenPythia.h
index 588b8ae19df..31ce52a6019 100644
--- a/EVGEN/AliGenPythia.h
+++ b/EVGEN/AliGenPythia.h
@@ -34,6 +34,8 @@ class AliGenPythia : public AliGenerator
     virtual void    SetEnergyCMS(Float_t energy=5500) {fEnergyCMS=energy;}
     // force decay type
     virtual void    SetForceDecay(Decay_t decay=semimuonic) {fForceDecay=decay;}
+    // treat protons as inside nuclei
+    virtual void    SetNuclei(Int_t a1, Int_t a2);
     // get cross section of process
     virtual Float_t GetXsection() {return fXsection;}
     // Check PDG code
@@ -53,6 +55,9 @@ class AliGenPythia : public AliGenerator
     AliPythia   *fPythia;       // Pythia 
     Float_t     fPtHardMin;     // lower pT-hard cut 
     Float_t     fPtHardMax;     // higher pT-hard cut
+    Int_t       fNucA1;         // mass number nucleus side 1
+    Int_t       fNucA2;         // mass number nucleus side 2
+    
     AliDecayer  *fDecayer;
  private:
     // check if particle is selected as parent particle
diff --git a/EVGEN/AliPythia.cxx b/EVGEN/AliPythia.cxx
index 5e1626ef742..06db4c0b569 100644
--- a/EVGEN/AliPythia.cxx
+++ b/EVGEN/AliPythia.cxx
@@ -15,6 +15,10 @@
 
 /*
 $Log$
+Revision 1.8  2000/09/06 14:26:24  morsch
+Decayer functionality of AliPythia has been moved to AliDecayerPythia.
+Class is now a singleton.
+
 Revision 1.7  2000/06/09 20:34:50  morsch
 All coding rule violations except RS3 corrected
 
@@ -154,6 +158,27 @@ Int_t AliPythia::CheckedLuComp(Int_t kf)
     return kc;
 }
 
+void AliPythia::SetNuclei(Int_t a1, Int_t a2)
+{
+// Treat protons as inside nuclei with mass numbers a1 and a2  
+//    The MSTP array in the PYPARS common block is used to enable and 
+//    select the nuclear structure functions. 
+//    MSTP(52)  : (D=1) choice of proton and nuclear structure-function library
+//            =1: internal PYTHIA acording to MSTP(51) 
+//            =2: PDFLIB proton  s.f., with MSTP(51)  = 1000xNGROUP+NSET
+//            =3: PDFLIB proton  s.f. with nuclar correction:
+//                MSTP( 51)  = 1000xNPGROUP+NPSET
+//                MSTP(151)  = 1000xNAGROUP+NASET
+//    MSTP(192) : Mass number of nucleus side 1
+//    MSTP(193) : Mass number of nucleus side 2
+
+    SetMSTP(52,3);
+    SetMSTP(191, 1001);
+    SetMSTP(192, a1);
+    SetMSTP(193, a2);  
+}
+	
+
 AliPythia* AliPythia::Instance()
 {
     if (fgAliPythia) {
diff --git a/EVGEN/AliPythia.h b/EVGEN/AliPythia.h
index d1fca32e2d7..2a58e82c24e 100644
--- a/EVGEN/AliPythia.h
+++ b/EVGEN/AliPythia.h
@@ -17,6 +17,9 @@ class AliPythia:public TPythia6
     // Pythia initialisation for selected processes
     virtual void ProcInit
 	(Process_t process, Float_t energy, StrucFunc_t strucfunc);
+    // treat protons as inside nuclei
+    virtual void    SetNuclei(Int_t a1, Int_t a2);
+    // return instance of the singleton
     static  AliPythia* Instance();
 
  protected:
-- 
2.39.3