[PWGHF] Fix tagging of gen D0 mesons in candidateCreatorDstar (#10837)

Author: fgrosa

PWGHF/TableProducer/candidateCreatorDstar.cxx

@@ -725,19 +725,30 @@ struct HfCandidateCreatorDstarExpressions {
         }
 
         // D*± → D0(bar) π±
-        if (RecoDecay::isMatchedMCGen(mcParticles, particle, Pdg::kDStar, std::array{+kPiPlus, +kPiPlus, -kKPlus}, true, &signDstar, 2)) {
-          flagDstar = signDstar * (BIT(aod::hf_cand_dstar::DecayType::DstarToD0Pi));
-        } else if (RecoDecay::isMatchedMCGen(mcParticles, particle, Pdg::kDStar, std::array{+kPiPlus, +kPiPlus, -kKPlus, +kPi0}, false, &signDstar, 2) || RecoDecay::isMatchedMCGen(mcParticles, particle, Pdg::kDStar, std::array{-kPiPlus, -kPiPlus, +kKPlus, +kPi0}, false, &signDstar, 2)) {
-          flagDstar = signDstar * (BIT(aod::hf_cand_dstar::DecayType::DstarToD0PiPi0));
-        }
+        std::vector<int> listIndexDaughters{};
+        bool isDstarToDzeroPi = RecoDecay::isMatchedMCGen(mcParticles, particle, Pdg::kDStar, std::array{+Pdg::kD0, +kPiPlus}, true, &signDstar, 1, &listIndexDaughters);
+
         // D0(bar) → π± K∓
-        if (RecoDecay::isMatchedMCGen(mcParticles, particle, Pdg::kD0, std::array{+kPiPlus, -kKPlus}, true, &signD0)) {
-          flagD0 = signD0 * (BIT(aod::hf_cand_dstar::DecayType::D0ToPiK));
-        } else if (RecoDecay::isMatchedMCGen(mcParticles, particle, Pdg::kD0, std::array{+kPiPlus, -kKPlus, +kPi0}, false, &signD0) || RecoDecay::isMatchedMCGen(mcParticles, particle, Pdg::kD0, std::array{-kPiPlus, +kKPlus, +kPi0}, false, &signD0)) {
-          flagD0 = signD0 * (BIT(aod::hf_cand_dstar::DecayType::D0ToPiKPi0));
+        if (isDstarToDzeroPi) {
+          aod::McParticles::iterator particleD0;
+          for (const auto& dauIdx : listIndexDaughters) {
+            if (dauIdx >= 0) {
+              particleD0 = mcParticles.rawIteratorAt(dauIdx);
+              if (std::abs(particleD0.pdgCode()) == Pdg::kD0) {
+                break;
+              }
+            }
+          }
+          if (RecoDecay::isMatchedMCGen(mcParticles, particleD0, Pdg::kD0, std::array{+kPiPlus, -kKPlus}, true, &signD0)) {
+            flagDstar = signDstar * (BIT(aod::hf_cand_dstar::DecayType::DstarToD0Pi));
+            flagD0 = signD0 * (BIT(aod::hf_cand_dstar::DecayType::D0ToPiK));
+          } else if (RecoDecay::isMatchedMCGen(mcParticles, particleD0, Pdg::kD0, std::array{+kPiPlus, -kKPlus, +kPi0}, false, &signD0) || RecoDecay::isMatchedMCGen(mcParticles, particleD0, -Pdg::kD0, std::array{-kPiPlus, +kKPlus, +kPi0}, false, &signD0)) {
+            flagDstar = signDstar * (BIT(aod::hf_cand_dstar::DecayType::DstarToD0PiPi0));
+            flagD0 = signD0 * (BIT(aod::hf_cand_dstar::DecayType::D0ToPiKPi0));
+          }
         }
 
-        // check wether the particle is non-promt (from a B0 hadron)
+        // check wether the particle is non-prompt (from a B0 hadron)
         if (flagDstar != 0) {
           originDstar = RecoDecay::getCharmHadronOrigin(mcParticles, particle, false, &idxBhadMothers);
         }