[DPG] Add flag to reject particles from background events

DPG/Tasks/AOTTrack/qaEfficiency.cxx

@@ -201,6 +201,7 @@ struct QaEfficiency {
   Configurable<bool> numSameCollision{"numSameCollision", false, "Flag to ask that the numerator is in the same collision as the denominator"};
   Configurable<bool> noFakesHits{"noFakesHits", false, "Flag to reject tracks that have fake hits"};
   Configurable<bool> skipEventsWithoutTPCTracks{"skipEventsWithoutTPCTracks", false, "Flag to reject events that have no tracks reconstructed in the TPC"};
+  Configurable<bool> skipParticlesFromBackgroundEvents{"skipParticlesFromBackgroundEvents", false, "Flag to reject particles from background events (for embedded MC)"};
   Configurable<float> maxProdRadius{"maxProdRadius", 9999.f, "Maximum production radius of the particle under study"};
   Configurable<float> nsigmaTPCDe{"nsigmaTPCDe", 3.f, "Value of the Nsigma TPC cut for deuterons PID"};
   // Charge selection
@@ -1548,6 +1549,9 @@ struct QaEfficiency {
         histos.fill(countingHisto, trkCutIdxHasMcPart); // Tracks with particles (i.e. no fakes)
       }
       const auto mcParticle = track.mcParticle();
+      if (skipParticlesFromBackgroundEvents && mcParticle.fromBackgroundEvent()) {
+        return false;
+      }
       if (!isInAcceptance<true, doFillHisto>(mcParticle, countingHisto, trkCutIdxHasMcPart)) {
         // 3: pt cut 4: eta cut 5: phi cut 6: y cut
         return false;
@@ -1913,6 +1917,9 @@ struct QaEfficiency {
 
         /// only to fill denominator of ITS-TPC matched primary tracks only in MC events with at least 1 reco. vtx
         for (const auto& particle : groupedMcParticles) { // Particle loop
+          if (skipParticlesFromBackgroundEvents && particle.fromBackgroundEvent()) {
+            continue;
+          }
 
           /// require generated particle in acceptance
           if (!isInAcceptance<true, false>(particle, nullptr)) {
@@ -1968,6 +1975,9 @@ struct QaEfficiency {
       // Loop on particles to fill the denominator
       float dNdEta = 0; // Multiplicity
       for (const auto& mcParticle : groupedMcParticles) {
+        if (skipParticlesFromBackgroundEvents && mcParticle.fromBackgroundEvent()) {
+          continue;
+        }
         if (TMath::Abs(mcParticle.eta()) <= 2.f && !mcParticle.has_daughters()) {
           dNdEta += 1.f;
         }