Add multiplicity distribution task

Analysis/Tasks/PWGCF/correlations.cxx

@@ -153,6 +153,9 @@ struct CorrelationTask {
 
     same->fillEvent(centrality, CorrelationContainer::kCFStepAll);
 
+    if (!collision.alias()[kINT7]) {
+      return;
+    }
     if (!collision.sel7()) {
       return;
     }

Analysis/Tasks/PWGCF/filterCF.cxx

@@ -50,6 +50,9 @@ struct FilterCF {
   {
     LOGF(info, "Tracks for collision: %d | Vertex: %.1f | INT7: %d | V0M: %.1f", tracks.size(), collision.posZ(), collision.sel7(), collision.centV0M());
 
+    if (!collision.alias()[kINT7]) {
+      return;
+    }
     if (!collision.sel7()) {
       return;
     }

Analysis/Tutorials/CMakeLists.txt

@@ -172,3 +172,8 @@ o2_add_dpl_workflow(compatible-bcs
                   SOURCES src/compatibleBCs.cxx
                   PUBLIC_LINK_LIBRARIES O2::Framework O2::AnalysisCore O2::AnalysisDataModel
                   COMPONENT_NAME AnalysisTutorial)
+
+o2_add_dpl_workflow(multiplicity-event-track-selection
+                  SOURCES src/multiplicityEventTrackSelection.cxx
+                  PUBLIC_LINK_LIBRARIES O2::Framework O2::AnalysisCore O2::AnalysisDataModel
+                  COMPONENT_NAME AnalysisTutorial)

Analysis/Tutorials/src/multiplicityEventTrackSelection.cxx

@@ -0,0 +1,57 @@
+// Copyright CERN and copyright holders of ALICE O2. This software is
+// distributed under the terms of the GNU General Public License v3 (GPL
+// Version 3), copied verbatim in the file "COPYING".
+//
+// See http://alice-o2.web.cern.ch/license for full licensing information.
+//
+// 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.
+
+#include "Framework/AnalysisDataModel.h"
+#include "Framework/AnalysisTask.h"
+#include "Framework/runDataProcessing.h"
+#include <TH1F.h>
+
+#include "AnalysisDataModel/EventSelection.h"
+#include "AnalysisDataModel/TrackSelectionTables.h"
+
+using namespace o2;
+using namespace o2::framework;
+using namespace o2::framework::expressions;
+
+// Example task generating a multiplicity distribution of
+// collision which pass the INT7 selection and
+// tracks which pass the "isGlobalTrack" selection
+//
+// Needs to run with event and track selection:
+// o2-analysis-timestamp | o2-analysis-event-selection | o2-analysis-trackextension | o2-analysis-trackselection | o2-analysistutorial-multiplicity-event-track-selection
+
+struct MultiplicityEventTrackSelection {
+
+  OutputObj<TH1F> multiplicity{TH1F("multiplicity", "multiplicity", 5000, -0.5, 4999.5)};
+
+  Filter collisionZFilter = nabs(aod::collision::posZ) < 10.0f;
+  Filter trackFilter = (nabs(aod::track::eta) < 0.8f) && (aod::track::pt > 0.15f) && (aod::track::isGlobalTrack == (uint8_t) true);
+
+  void process(soa::Filtered<soa::Join<aod::Collisions, aod::EvSels>>::iterator const& collision,
+               soa::Filtered<soa::Join<aod::Tracks, aod::TrackSelection>> const& tracks)
+  {
+    if (!collision.alias()[kINT7]) {
+      return;
+    }
+    if (!collision.sel7()) {
+      return;
+    }
+
+    LOGP(INFO, "Collision with {} tracks", tracks.size());
+    multiplicity->Fill(tracks.size());
+  }
+};
+
+// Workflow definition
+WorkflowSpec defineDataProcessing(ConfigContext const&)
+{
+  return WorkflowSpec{
+    adaptAnalysisTask<MultiplicityEventTrackSelection>("multiplicity-event-track-selection")};
+}