[PWGDQ]Adding generator and ini files to trigger on like-sign dimuons in pp

MC/config/PWGDQ/external/generator/generator_likeSignDimuon_gaptriggered.C

@@ -0,0 +1,130 @@
+#include "FairGenerator.h"
+#include "Generators/GeneratorPythia8.h"
+#include "Pythia8/Pythia.h"
+#include "TRandom.h"
+
+#include <string>
+#include <vector>
+
+using namespace o2::eventgen;
+
+namespace o2
+{
+namespace eventgen
+{
+
+class GeneratorLikeSignDimuonGapTriggered : public o2::eventgen::GeneratorPythia8 {
+public:
+
+  /// constructor
+  GeneratorLikeSignDimuonGapTriggered(int inputTriggerRatio = 3)
+  {
+    mGeneratedEvents = 0;
+    mInverseTriggerRatio = inputTriggerRatio;
+    mRequiredMuonMultiplicity = 2;
+    mMuonRapidityMin = -4.3;
+    mMuonRapidityMax = -2.2;
+    mVerbose = false;
+
+    // minimum-bias Pythia8 instance
+    auto seed = (gRandom->TRandom::GetSeed() % 900000000);
+    TString pathconfigMB = gSystem->ExpandPathName("$O2DPG_MC_CONFIG_ROOT/MC/config/PWGDQ/pythia8/generator/pythia8_inel_cr2.cfg");
+    pythiaMBgen.readFile(pathconfigMB.Data());
+    pythiaMBgen.readString("Random:setSeed on");
+    pythiaMBgen.readString("Random:seed " + std::to_string(seed));
+  }
+  /// Destructor
+  ~GeneratorLikeSignDimuonGapTriggered() = default;
+
+  void setMuonMultiplicity(int n) { mRequiredMuonMultiplicity = n; }
+  void setMuonRapidity(double yMin, double yMax)
+  {
+    mMuonRapidityMin = yMin;
+    mMuonRapidityMax = yMax;
+  }
+  void setVerbose(bool v) { mVerbose = v; }
+
+  protected:
+
+  Bool_t generateEvent() override
+  {
+    if (mGeneratedEvents % mInverseTriggerRatio == 0) {
+      // signal event: keep generating until like-sign dimuon found
+      bool genOk = false;
+      while (!genOk) {
+        mPythia.event.reset();
+        genOk = GeneratorPythia8::generateEvent();
+        if (genOk) genOk = selectLikeSignDimuon(mPythia.event);
+      }
+    } else {
+      // minimum-bias event from the independent generator
+      bool genOk = false;
+      pythiaMBgen.event.reset();
+      while (!genOk) genOk = pythiaMBgen.next();
+      mPythia.event = pythiaMBgen.event;
+    }
+    mGeneratedEvents++;
+    if (mVerbose) mOutputEvent.list();
+    return true;
+  }
+
+  Bool_t Init() override
+  {
+    GeneratorPythia8::Init();
+    pythiaMBgen.init();
+    return true;
+  }
+
+  // Accept the event if at least mRequiredMuonMultiplicity muons fall in the rapidity window AND at least one same-sign pair exists among them.
+  bool selectLikeSignDimuon(Pythia8::Event& event)
+  {
+    std::vector<const Pythia8::Particle*> muonsInWindow;
+    for (int ipa = 0; ipa < event.size(); ++ipa) {
+      if (std::abs(event[ipa].id()) != 13) continue;
+      float rap = event[ipa].y();
+      if (rap > mMuonRapidityMin && rap < mMuonRapidityMax) {
+        muonsInWindow.push_back(&event[ipa]);
+      }
+    }
+    if ((int)muonsInWindow.size() < mRequiredMuonMultiplicity) return false;
+    for (size_t i = 0; i < muonsInWindow.size(); ++i) {
+      for (size_t j = i + 1; j < muonsInWindow.size(); ++j) {
+        if (muonsInWindow[i]->id() * muonsInWindow[j]->id() > 0) return true;
+      }
+    }
+    return false;
+  }
+
+  private:
+  Pythia8::Event mOutputEvent;
+
+  unsigned long long mGeneratedEvents;
+  int mInverseTriggerRatio;
+  Pythia8::Pythia pythiaMBgen;
+
+  int mRequiredMuonMultiplicity;
+  double mMuonRapidityMin;
+  double mMuonRapidityMax;
+  bool mVerbose;
+};
+
+} // namespace eventgen
+} // namespace o2
+
+FairGenerator* GeneratorLikeSignDimuonGapTriggered_dq(double rapidityMin = -4.3, double rapidityMax = -2.2, int requiredMuons = 2, int inputTriggerRatio = 3, bool verbose = false)
+{
+  auto gen = new o2::eventgen::GeneratorLikeSignDimuonGapTriggered(inputTriggerRatio);
+  gen->setMuonMultiplicity(requiredMuons);
+  gen->setMuonRapidity(rapidityMin, rapidityMax);
+  gen->setVerbose(verbose);
+
+  // random seed
+  gen->readString("Random:setSeed on");
+  uint random_seed;
+  unsigned long long int random_value = 0;
+  std::ifstream urandom("/dev/urandom", std::ios::in | std::ios::binary);
+  urandom.read(reinterpret_cast<char*>(&random_value), sizeof(random_seed));
+  gen->readString(Form("Random:seed = %d", random_value % 900000001));
+
+  return gen;
+}

MC/config/PWGDQ/ini/Generator_likeSignDimuon_TriggerGap.ini

@@ -0,0 +1,7 @@
+### The external generator derives from GeneratorPythia8.
+[GeneratorExternal]
+fileName=${O2DPG_MC_CONFIG_ROOT}/MC/config/PWGDQ/external/generator/generator_likeSignDimuon_gaptriggered.C
+funcName=GeneratorLikeSignDimuonGapTriggered_dq(-4.3, -2.2, 2, 3)
+
+[GeneratorPythia8]
+includePartonEvent=true