Modified MC Rec matching function to work with partly reconstructed decays for resonance workflow (AliceO2Group#7905)

Author: Luca610

Common/Core/RecoDecay.h

@@ -662,6 +662,7 @@ struct RecoDecay {
 
   /// Checks whether the reconstructed decay candidate is the expected decay.
   /// \param checkProcess  switch to accept only decay daughters by checking the production process of MC particles
+  /// \param acceptIncompleteReco  switch to accept candidates with only part of the daughters reconstructed
   /// \param particlesMC  table with MC particles
   /// \param arrDaughters  array of candidate daughters
   /// \param PDGMother  expected mother PDG code
@@ -670,7 +671,7 @@ struct RecoDecay {
   /// \param sign  antiparticle indicator of the found mother w.r.t. PDGMother; 1 if particle, -1 if antiparticle, 0 if mother not found
   /// \param depthMax  maximum decay tree level to check; Daughters up to this level will be considered. If -1, all levels are considered.
   /// \return index of the mother particle if the mother and daughters are correct, -1 otherwise
-  template <bool acceptFlavourOscillation = false, bool checkProcess = false, std::size_t N, typename T, typename U>
+  template <bool acceptFlavourOscillation = false, bool checkProcess = false, bool acceptIncompleteReco = false, std::size_t N, typename T, typename U>
   static int getMatchedMCRec(const T& particlesMC,
                              const std::array<U, N>& arrDaughters,
                              int PDGMother,
@@ -726,7 +727,7 @@ struct RecoDecay {
           return -1;
         }
         // Check that the number of direct daughters is not larger than the number of expected final daughters.
-        if constexpr (!checkProcess) {
+        if constexpr (!acceptIncompleteReco && !checkProcess) {
           if (particleMother.daughtersIds().back() - particleMother.daughtersIds().front() + 1 > static_cast<int>(N)) {
             // Printf("MC Rec: Rejected: too many direct daughters: %d (expected %ld final)", particleMother.daughtersIds().back() - particleMother.daughtersIds().front() + 1, N);
             return -1;
@@ -740,7 +741,7 @@ struct RecoDecay {
         // }
         // printf("\n");
         //  Check whether the number of actual final daughters is equal to the number of expected final daughters (i.e. the number of provided prongs).
-        if (arrAllDaughtersIndex.size() != N) {
+        if (!acceptIncompleteReco && arrAllDaughtersIndex.size() != N) {
           // Printf("MC Rec: Rejected: incorrect number of final daughters: %ld (expected %ld)", arrAllDaughtersIndex.size(), N);
           return -1;
         }