[PWGLF/Tasks/Resonances] kstar892LightIon.cxx: Added another process function to get the MC template

PWGLF/Tasks/Resonances/kstar892LightIon.cxx

@@ -468,6 +468,14 @@ struct Kstar892LightIon {
       hMC.add("CorrelatedBG/hK2_1770", "Wrong pair distribution for K*(1410)", kTH3F, {ptAxis, centralityAxis, invmassAxis});
       hMC.add("CorrelatedBG/hK2_1820", "Wrong pair distribution for K*(1410)", kTH3F, {ptAxis, centralityAxis, invmassAxis});
     }
+    if (doprocessTemplateMC) {
+      hMC.add("Template/hSignal", "True K*0 signal", kTH3F, {ptAxis, centralityAxis, invmassAxis});
+      hMC.add("Template/hKstarReflection", "K*0 signal due to mis-identification", kTH3F, {ptAxis, centralityAxis, invmassAxis});
+      hMC.add("Template/hSameMotherOther", "Kpi pair from same mother other than K*0", kTH3F, {ptAxis, centralityAxis, invmassAxis});
+      hMC.add("Template/hDifferentMother", "Kpi pair from different mothers", kTH3F, {ptAxis, centralityAxis, invmassAxis});
+      hMC.add("Template/hPrimaryResonance", "Kpi pair one primary another from decay", kTH3F, {ptAxis, centralityAxis, invmassAxis});
+      hMC.add("Template/hPrimaryPrimary", "Primary Kpi pair", kTH3F, {ptAxis, centralityAxis, invmassAxis});
+    }
 
     if (doprocessRecKinematics) {
       hMC.add("Kinematics/h1RecCent", "centrality reconstructed", kTH1F, {centralityAxis});
@@ -2583,6 +2591,121 @@ struct Kstar892LightIon {
 
   PROCESS_SWITCH(Kstar892LightIon, processRecCorrelatedBackground, "Process correlated background", false);
 
+  void processTemplateMC(EventCandidatesMC::iterator const& collision, TrackCandidatesMC const& tracks, aod::McParticles const&, EventMCGenerated const&)
+  {
+    if (!collision.has_mcCollision())
+      return;
+
+    if (!selectionEvent(collision, false))
+      return;
+
+    centrality = -1.f;
+    if (selectCentEstimator == kFT0M) {
+      centrality = collision.centFT0M();
+    } else if (selectCentEstimator == kFT0A) {
+      centrality = collision.centFT0A();
+    } else if (selectCentEstimator == kFT0C) {
+      centrality = collision.centFT0C();
+    } else if (selectCentEstimator == kFV0A) {
+      centrality = collision.centFV0A();
+    } else {
+      centrality = collision.centFT0M();
+    }
+
+    auto classifyOrigin = [](const aod::McParticle& part, int64_t& motherIdx) -> int {
+      motherIdx = -1;
+      if (!part.has_mothers())
+        return 0;
+      for (const auto& mom : part.mothers_as<aod::McParticles>()) {
+        if (!mom.producedByGenerator())
+          continue;
+        motherIdx = mom.globalIndex();
+        if (std::abs(mom.pdgCode()) == o2::constants::physics::kK0Star892)
+          return 1;
+        return 2;
+      }
+      return 0;
+    };
+
+    for (const auto& [track1, track2] : combinations(CombinationsFullIndexPolicy(tracks, tracks))) {
+
+      if (!selectionTrack(track1) || !selectionTrack(track2))
+        continue;
+
+      if (track1.globalIndex() == track2.globalIndex())
+        continue;
+
+      if (!selectionPair(track1, track2))
+        continue;
+
+      if (!selectionPID(track1, PIDParticle::kKaon))
+        continue;
+      if (!selectionPID(track2, PIDParticle::kPion))
+        continue;
+
+      if (isMisidentified(track1, PIDParticle::kKaon))
+        continue;
+      if (isMisidentified(track2, PIDParticle::kPion))
+        continue;
+
+      if (selectionConfig.isApplyFakeTrack && (isFakeTrack(track1, PIDParticle::kKaon) || isFakeTrack(track2, PIDParticle::kPion)))
+        continue;
+
+      if (!track1.has_mcParticle() || !track2.has_mcParticle())
+        continue;
+
+      daughter1 = ROOT::Math::PxPyPzMVector(track1.px(), track1.py(), track1.pz(), massKa);
+      daughter2 = ROOT::Math::PxPyPzMVector(track2.px(), track2.py(), track2.pz(), massPi);
+      mother = daughter1 + daughter2;
+
+      if (mother.Rapidity() < selectionConfig.motherRapidityMin ||
+          mother.Rapidity() > selectionConfig.motherRapidityMax)
+        continue;
+
+      const float recMass = mother.M();
+      const float recPt = mother.Pt();
+
+      const auto mcKa = track1.mcParticle();
+      const auto mcPi = track2.mcParticle();
+
+      if (selectionConfig.isPrimaryTrack && (!mcKa.isPhysicalPrimary() || !mcPi.isPhysicalPrimary()))
+        continue;
+
+      int64_t kaMotherIdx = -1;
+      int64_t piMotherIdx = -1;
+      const int kaOrigin = classifyOrigin(mcKa, kaMotherIdx);
+      const int piOrigin = classifyOrigin(mcPi, piMotherIdx);
+
+      const bool kaIsKstar = (kaOrigin == 1);
+      const bool piIsKstar = (piOrigin == 1);
+      const bool kaHasParent = (kaOrigin != 0);
+      const bool piHasParent = (piOrigin != 0);
+      const bool sameMother = (kaMotherIdx >= 0) && (piMotherIdx >= 0) && (kaMotherIdx == piMotherIdx);
+
+      if (kaIsKstar && piIsKstar && sameMother) {
+        const bool correctAssignment = (std::abs(mcKa.pdgCode()) == PDG_t::kKPlus) && (std::abs(mcPi.pdgCode()) == PDG_t::kPiPlus);
+        if (correctAssignment) {
+          hMC.fill(HIST("Template/hSignal"), recPt, centrality, recMass);
+        } else {
+          hMC.fill(HIST("Template/hKstarReflection"), recPt, centrality, recMass);
+        }
+
+      } else if (sameMother && kaHasParent && piHasParent) {
+        hMC.fill(HIST("Template/hSameMotherOther"), recPt, centrality, recMass);
+
+      } else if (!sameMother && kaHasParent && piHasParent) {
+        hMC.fill(HIST("Template/hDifferentMother"), recPt, centrality, recMass);
+
+      } else if (kaHasParent != piHasParent) {
+        hMC.fill(HIST("Template/hPrimaryResonance"), recPt, centrality, recMass);
+
+      } else {
+        hMC.fill(HIST("Template/hPrimaryPrimary"), recPt, centrality, recMass);
+      }
+    }
+  }
+  PROCESS_SWITCH(Kstar892LightIon, processTemplateMC, "Process MC Template Background", false);
+
   void processRecKinematics(EventCandidatesMC::iterator const& collision, TrackCandidatesMC const& tracks, aod::McParticles const&, EventMCGenerated const&)
   {
     if (!collision.has_mcCollision()) {