Add BoxGen function to implement flat pT generation for Non-HFE efficiency studies (#2334)

* Update GeneratorHF_Non_Hfe.json

Flat pion and eta distributions are added to enhance statistics at high transverse momentum.

* Update pythia8_NonHfe.cfg

Remove CR mode2

* Update GeneratorHF_Non_Hfe.json

* Remove number parameter

* Update GeneratorHF_Non_Hfe.json

* implement flat pT generation for pi0 and eta

* implement flat pT generation for pi0 and eta

* implement flat pT generation for pi0 and eta

* Update GeneratorHF_Non_Hfe.ini

* Update GeneratorHF_Non_Hfe.ini

* Update GeneratorHF_Non_Hfe.C

* Rename MC/config/PWGHF/trigger/selectNonHfe.C to MC/config/PWGHF/external/generator/selectNonHfe.C

* Update GeneratorHF_Non_Hfe.ini

* Update GeneratorHF_Non_Hfe.C

Author: rashigupt

MC/config/PWGHF/external/generator/selectNonHfe.C

@@ -0,0 +1,96 @@
+/// Select π⁰ and η within a given rapidity window for enhancement
+/// pdgPartForAccCut: PDG of the particle to select (111=π⁰, 221=η)
+/// minNb: minimum number of such particles per event for enhancement
+
+////  authors: Rashi Gupta (rashi.gupta@cern.ch)
+///  authors: Ravindra Singh (ravindra.singh@cern.ch)
+
+
+#if !defined(__CLING__) || defined(__ROOTCLING__)
+#include "FairGenerator.h"
+#include "FairPrimaryGenerator.h"
+#include "Generators/GeneratorPythia8.h"
+#include "TRandom3.h"
+#include "TParticlePDG.h"
+#include "TDatabasePDG.h"
+#include "TMath.h"
+#include <cmath>
+#include <vector>
+#endif
+
+#include "Pythia8/Pythia.h"
+using namespace Pythia8;
+
+class GeneratorPythia8Box : public o2::eventgen::GeneratorPythia8
+{
+public:
+  
+  GeneratorPythia8Box(std::vector<int> pdgList, int nInject = 3, float ptMin = 0.1, float ptMax = 50.0, float etaMin = -0.8, float etaMax = 0.8) 
+    : mPdgList(pdgList), nParticles(nInject), genMinPt(ptMin), genMaxPt(ptMax), genMinEta(etaMin), genMaxEta(etaMax)
+  {
+  }
+
+  ~GeneratorPythia8Box() = default;
+
+Bool_t generateEvent() override
+{
+  bool hasElectron = false; 
+
+  while (!hasElectron) {
+    mPythia.event.reset();
+
+    for (int i{0}; i < nParticles; ++i)
+    {
+      int currentPdg = mPdgList[gRandom->Integer(mPdgList.size())];
+      double mass = TDatabasePDG::Instance()->GetParticle(currentPdg)->Mass();
+
+      const double pt = gRandom->Uniform(genMinPt, genMaxPt);
+      const double eta = gRandom->Uniform(genMinEta, genMaxEta);
+      const double phi = gRandom->Uniform(0, TMath::TwoPi());
+
+      const double px{pt * std::cos(phi)};
+      const double py{pt * std::sin(phi)};
+      const double pz{pt * std::sinh(eta)};
+      const double et{std::hypot(std::hypot(pt, pz), mass)};
+
+    
+      mPythia.event.append(currentPdg, 11, 0, 0, px, py, pz, et, mass);
+    }
+
+   
+    if (!mPythia.next()) continue;
+
+  
+    for (int i = 0; i < mPythia.event.size(); ++i) {
+      if (std::abs(mPythia.event[i].id()) == 11) {
+        
+      
+        double childPt = mPythia.event[i].pT();
+        double childEta = mPythia.event[i].eta();
+
+        if (childPt > 0.1 && std::abs(childEta) < 1.2) {
+          hasElectron = true; // Mil gaya!
+          break; 
+        }
+      }
+    }
+  
+  }
+
+  return true; 
+}
+
+private:
+  std::vector<int> mPdgList;
+  double genMinPt, genMaxPt;
+  double genMinEta, genMaxEta;
+  int nParticles;
+};
+
+
+FairGenerator *generatePythia8Box(float ptMin = 0.1, float ptMax = 50.0)
+{
+
+  std::vector<int> pdgList = {111, 221};
+  return new GeneratorPythia8Box(pdgList, 3, ptMin, ptMax, -0.8, 0.8);
+}

MC/config/PWGHF/ini/GeneratorHF_Non_Hfe.ini

@@ -1,4 +1,7 @@
-#### This configuration uses the Hybrid external generator to trigger π⁰/η production within the specified rapidity window
-
-[GeneratorHybrid]
-configFile = ${O2DPG_MC_CONFIG_ROOT}/MC/config/PWGHF/hybrid/GeneratorHF_Non_Hfe.json
+#### This configuration uses the Box generator to trigger π⁰/η production within the specified rapidity window
+[GeneratorExternal]
+fileName=${O2DPG_MC_CONFIG_ROOT}/MC/config/PWGHF/external/generator/selectNonHfe.C
+funcName = generatePythia8Box(0.1, 50.0)
+[GeneratorPythia8]
+config=${O2DPG_MC_CONFIG_ROOT}/MC/config/PWGHF/pythia8/generator/pythia8_NonHfe.cfg
+includePartonEvent=true

MC/config/PWGHF/ini/tests/GeneratorHF_Non_Hfe.C

@@ -1,4 +1,4 @@
-int Hybrid() {
+int External() {
     std::string path{"o2sim_Kine.root"};
 
     const int pdgPi0 = 111;

MC/config/PWGHF/pythia8/generator/pythia8_NonHfe.cfg

@@ -8,11 +8,14 @@ Beams:idB 2212 			# proton
 Beams:eCM 13600. 		# GeV
 
 ### processes
-SoftQCD:inelastic on		# all inelastic processes
+
+ProcessLevel:all = off     
 
 ### decays
 ParticleDecays:limitTau0 on	
 ParticleDecays:tau0Max 10.
+### processes
+
 
 ### switch off all decay channels
 111:onMode = off