Add helper function for KPi pair mass.

Author: Mattia Faggin

PWGHF/Core/HfHelper.h

@@ -358,6 +358,18 @@ class HfHelper
     return candidate.m(std::array{o2::constants::physics::MassPiPlus, o2::constants::physics::MassKPlus, o2::constants::physics::MassProton});
   }
 
+  template <typename T>
+  auto invMassKPiPairLcToPKPi(const T& candidate)
+  {
+    return RecoDecay::m(std::array{candidate.pVectorProng1(), candidate.pVectorProng2()}, std::array{o2::constants::physics::MassKPlus, o2::constants::physics::MassPiPlus});
+  }
+
+  template <typename T>
+  auto invMassKPiPairLcToPiKP(const T& candidate)
+  {
+    return RecoDecay::m(std::array{candidate.pVectorProng1(), candidate.pVectorProng0()}, std::array{o2::constants::physics::MassKPlus, o2::constants::physics::MassPiPlus});
+  }
+
   // Ξc± → p± K∓ π±
 
   template <typename T>

PWGHF/D2H/Tasks/taskCharmPolarisation.cxx

@@ -815,7 +815,7 @@ struct TaskPolarisationCharmHadrons {
             }
           }
           // invariant mass of the KPi pair
-          invMassKPiLc = RecoDecay::m(std::array{candidate.pVectorProng1(), candidate.pVectorProng2()}, std::array{massKaon, massPi});
+          invMassKPiLc = hfHelper.invMassKPiPairLcToPKPi(candidate);
         } else if (iMass == charm_polarisation::MassHyposLcToPKPi::PiKP && candidate.isSelLcToPiKP() >= selectionFlagLcToPKPi) {
           // reconstructed as piKp
           pxDau = candidate.pxProng2();
@@ -841,7 +841,7 @@ struct TaskPolarisationCharmHadrons {
             }
           }
           // invariant mass of the KPi pair
-          invMassKPiLc = RecoDecay::m(std::array{candidate.pVectorProng1(), candidate.pVectorProng0()}, std::array{massKaon, massPi});
+          invMassKPiLc = hfHelper.invMassKPiPairLcToPiKP(candidate);
         } else {
           // NB: no need to check cases in which candidate.isSelLcToPKPi() and candidate.isSelLcToPiKP() are both false, because they are rejected already by the Filter
           // ... but we need to put this protections here!

PWGHF/TableProducer/candidateSelectorLc.cxx

@@ -241,8 +241,18 @@ struct HfCandidateSelectorLc {
     /// cut on the Kpi pair invariant mass, to study Lc->pK*(->Kpi)
     const double cutMassKPi = cuts->get(pTBin, "mass (Kpi)");
     if (cutMassKPi > 0) {
-      if (std::abs(RecoDecay::m(std::array{trackKaon.pVector(), trackPion.pVector()}, std::array{o2::constants::physics::MassKaonCharged, o2::constants::physics::MassPiPlus}) - massK0Star892) > cutMassKPi) {
-        return false;
+      if (trackProton.globalIndex() == candidate.prong0Id()) {
+        // inspecting the pKpi hypothesis
+        // K: prong1, pi: prong 2
+        if (std::abs(hfHelper.invMassKPiPairLcToPKPi(candidate) - massK0Star892) > cutMassKPi) {
+          return false;
+        }
+      } else {
+        // inspecting the piKp hypothesis
+        // K: prong1, pi: prong 0
+        if (std::abs(hfHelper.invMassKPiPairLcToPiKP(candidate) - massK0Star892) > cutMassKPi) {
+          return false;
+        }
       }
     }
 

PWGHF/TableProducer/treeCreatorLcToPKPi.cxx

@@ -493,8 +493,8 @@ struct HfTreeCreatorLcToPKPi {
         }
       };
 
-      fillTable(0, candidate.isSelLcToPKPi(), hfHelper.invMassLcToPKPi(candidate), hfHelper.ctLc(candidate), hfHelper.yLc(candidate), hfHelper.eLc(candidate), RecoDecay::m(std::array{trackNeg.pVector(), trackPos2.pVector()}, std::array{o2::constants::physics::MassKaonCharged, o2::constants::physics::MassPiPlus}));
-      fillTable(1, candidate.isSelLcToPiKP(), hfHelper.invMassLcToPiKP(candidate), hfHelper.ctLc(candidate), hfHelper.yLc(candidate), hfHelper.eLc(candidate), RecoDecay::m(std::array{trackNeg.pVector(), trackPos1.pVector()}, std::array{o2::constants::physics::MassKaonCharged, o2::constants::physics::MassPiPlus}));
+      fillTable(0, candidate.isSelLcToPKPi(), hfHelper.invMassLcToPKPi(candidate), hfHelper.ctLc(candidate), hfHelper.yLc(candidate), hfHelper.eLc(candidate), hfHelper.invMassKPiPairLcToPKPi(candidate));
+      fillTable(1, candidate.isSelLcToPiKP(), hfHelper.invMassLcToPiKP(candidate), hfHelper.ctLc(candidate), hfHelper.yLc(candidate), hfHelper.eLc(candidate), hfHelper.invMassKPiPairLcToPiKP(candidate));
     }
 
     // Filling particle properties
@@ -752,8 +752,8 @@ struct HfTreeCreatorLcToPKPi {
         }
       };
 
-      fillTable(0, candidate.isSelLcToPKPi(), hfHelper.invMassLcToPKPi(candidate), hfHelper.ctLc(candidate), hfHelper.yLc(candidate), hfHelper.eLc(candidate), RecoDecay::m(std::array{trackNeg.pVector(), trackPos2.pVector()}, std::array{o2::constants::physics::MassKaonCharged, o2::constants::physics::MassPiPlus}));
-      fillTable(1, candidate.isSelLcToPiKP(), hfHelper.invMassLcToPiKP(candidate), hfHelper.ctLc(candidate), hfHelper.yLc(candidate), hfHelper.eLc(candidate), RecoDecay::m(std::array{trackNeg.pVector(), trackPos1.pVector()}, std::array{o2::constants::physics::MassKaonCharged, o2::constants::physics::MassPiPlus}));
+      fillTable(0, candidate.isSelLcToPKPi(), hfHelper.invMassLcToPKPi(candidate), hfHelper.ctLc(candidate), hfHelper.yLc(candidate), hfHelper.eLc(candidate), hfHelper.invMassKPiPairLcToPKPi(candidate));
+      fillTable(1, candidate.isSelLcToPiKP(), hfHelper.invMassLcToPiKP(candidate), hfHelper.ctLc(candidate), hfHelper.yLc(candidate), hfHelper.eLc(candidate), hfHelper.invMassKPiPairLcToPiKP(candidate));
     }
   }