[PWGEM/PhotonMeson] Add task for on-the-fly MC generator studies (#11217)

Co-authored-by: Nicolas Strangmann <nicolas.strangmann@.cern.ch>

Author: nstrangm

PWGEM/PhotonMeson/Tasks/CMakeLists.txt

@@ -29,6 +29,11 @@ o2physics_add_dpl_workflow(emc-bc-wise-pi0
                     PUBLIC_LINK_LIBRARIES O2::Framework O2::EMCALBase O2::EMCALCalib O2Physics::AnalysisCore
                     COMPONENT_NAME Analysis)
 
+o2physics_add_dpl_workflow(mc-generator-studies
+                    SOURCES mcGeneratorStudies.cxx
+                    PUBLIC_LINK_LIBRARIES O2::Framework O2Physics::AnalysisCore
+                    COMPONENT_NAME Analysis)
+
 o2physics_add_dpl_workflow(pcm-qc
                     SOURCES pcmQC.cxx
                     PUBLIC_LINK_LIBRARIES O2::Framework O2::DetectorsBase O2Physics::AnalysisCore O2Physics::PWGEMPhotonMesonCore

PWGEM/PhotonMeson/Tasks/mcGeneratorStudies.cxx

@@ -0,0 +1,48 @@
+// Copyright 2019-2024 CERN and copyright holders of ALICE O2.
+// See https://alice-o2.web.cern.ch/copyright for details of the copyright holders.
+// All rights not expressly granted are reserved.
+//
+// This software is distributed under the terms of the GNU General Public
+// License v3 (GPL Version 3), copied verbatim in the file "COPYING".
+//
+// In applying this license CERN does not waive the privileges and immunities
+// granted to it by virtue of its status as an Intergovernmental Organization
+// or submit itself to any jurisdiction.
+///
+/// \file mcGeneratorStudies.cxx
+///
+/// \brief Task that produces the generated pT spectrum of a given particle for MC studies based on on the fly MC simulations
+///
+/// \author Nicolas Strangmann (nicolas.strangmann@cern.ch) - Goethe University Frankfurt
+///
+
+#include "Framework/runDataProcessing.h"
+#include "Framework/AnalysisTask.h"
+#include "Framework/AnalysisDataModel.h"
+#include "Framework/ASoA.h"
+#include "Framework/HistogramRegistry.h"
+
+#include "TDatabasePDG.h"
+
+using namespace o2;
+using namespace o2::framework;
+
+struct MCGeneratorStudies {
+  HistogramRegistry mHistManager{"MCGeneratorStudyHistograms"};
+  Configurable<int> cfgSelectedParticleCode{"cfgSelectedParticleCode", 111, "PDG code of the particle to be investigated"};
+  Configurable<float> cfgMaxZVertex{"cfgMaxZVertex", 10, "Maximum absolute z-vertex distance (cm)"};
+  expressions::Filter zVertexFilter = aod::mccollision::posZ < cfgMaxZVertex && aod::mccollision::posZ > -cfgMaxZVertex;
+
+  void init(InitContext const&) { mHistManager.add("YieldVsNParticles", "pT of selected particles in all MC collisions vs number of all generated particles in event;#bf{#it{p}_{T} (GeV/#it{c})};#bf{#it{N} (Multiplicity)};#bf{#it{N}}", HistType::kTH2F, {{200, 0, 20}, {1000, 0, 10000}}); }
+
+  void process(soa::Filtered<aod::McCollisions>::iterator const&, aod::McParticles const& mcParticles)
+  {
+    int nParticles = mcParticles.size();
+    for (auto& mcParticle : mcParticles) {
+      if (mcParticle.pdgCode() == cfgSelectedParticleCode && std::abs(mcParticle.y()) < 0.8f)
+        mHistManager.fill(HIST("YieldVsNParticles"), mcParticle.pt(), nParticles);
+    }
+  }
+};
+
+WorkflowSpec defineDataProcessing(ConfigContext const& cfgc) { return WorkflowSpec{adaptAnalysisTask<MCGeneratorStudies>(cfgc, TaskName{"mc-generator-studies"})}; }