Please consider the following formatting changes to #17353

PWGMM/UE/Tasks/CMakeLists.txt

@@ -22,4 +22,9 @@ o2physics_add_dpl_workflow(ue-zdc-analysis
 o2physics_add_dpl_workflow(dedx-analysis
                     SOURCES dedxAnalysis.cxx
                     PUBLIC_LINK_LIBRARIES O2::Framework O2Physics::AnalysisCore
-                    COMPONENT_NAME Analysis)
+                    COMPONENT_NAME Analysis)
+
+o2physics_add_dpl_workflow(flattenicity-task
+                    SOURCES flattenicityTask.cxx
+                    PUBLIC_LINK_LIBRARIES O2::Framework O2Physics::AnalysisCore
+                    COMPONENT_NAME Analysis)

PWGMM/UE/Tasks/flattenicityTask.cxx

@@ -0,0 +1,321 @@
+// Copyright 2019-2020 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 flattenicityTask.cxx
+/// \brief Flattenicity analysis task for UE studies
+/// \author Eisha Rani
+/// \since August 2026
+
+#include "Common/Core/TrackSelection.h"
+#include "Common/Core/TrackSelectionDefaults.h"
+#include "Common/DataModel/EventSelection.h"
+#include "Common/DataModel/Multiplicity.h"
+#include "Common/DataModel/TrackSelectionTables.h"
+
+#include <Framework/ASoAHelpers.h>
+#include <Framework/AnalysisDataModel.h>
+#include <Framework/AnalysisTask.h>
+#include <Framework/Configurable.h>
+#include <Framework/Constants.h>
+#include <Framework/HistogramRegistry.h>
+#include <Framework/InitContext.h>
+#include <Framework/O2DatabasePDGPlugin.h>
+#include <Framework/runDataProcessing.h>
+#include <ReconstructionDataFormats/Track.h>
+
+#include <cmath>
+#include <vector>
+
+using namespace o2;
+using namespace o2::framework;
+using namespace o2::framework::expressions;
+
+struct FlattenicityTask {
+
+  // --- Flattenicity constants ---
+  static constexpr int NCH_A = 96;
+  static constexpr int NCH_C = 112;
+  static constexpr int NCELL = NCH_A + NCH_C;
+  static constexpr int NPHISECTORS = 8;
+  static constexpr int NETA_A = NCH_A / NPHISECTORS;
+  static constexpr int NETA_C = NCH_C / NPHISECTORS;
+
+  // FT0 acceptance
+  static constexpr float FT0A_ETA_MIN = 3.5f;
+  static constexpr float FT0A_ETA_MAX = 4.9f;
+  static constexpr float FT0C_ETA_MIN = -3.3f;
+  static constexpr float FT0C_ETA_MAX = -2.1f;
+
+  // --- Event selection constants ---
+  static constexpr float VERTEX_CUT = 10.0f;
+  static constexpr float FLAT_MIN = 0.0f;
+  static constexpr float INEL_ETA_CUT = 1.0f;
+  static constexpr float MIDRAP_ETA_CUT = 0.8f;
+
+  // --- Configurables ---
+  Configurable<float> cfgTrkEtaCut{"cfgTrkEtaCut", 0.8f, "Eta range for tracks"};
+  Configurable<float> cfgTrkLowPtCut{"cfgTrkLowPtCut", 0.15f, "Minimum pT"};
+
+  Configurable<bool> isRun3{"isRun3", true, "is Run3 dataset"};
+  Configurable<bool> timeEvsel{"timeEvsel", true, "TPC Time frame boundary cut"};
+  Configurable<bool> piluprejection{"piluprejection", true, "Pileup rejection"};
+  Configurable<bool> goodzvertex{"goodzvertex", true, "Good Z vertex"};
+
+  // --- Track selection ---
+  TrackSelection mySelectionPrim;
+
+  // --- Histograms ---
+  HistogramRegistry registry;
+
+  // --- Init ---
+  void init(InitContext const&) override
+  {
+    // Initialize track selection
+    mySelectionPrim = myTrackSelectionPrim();
+
+    // Define histograms
+    AxisSpec flatBins = {40, 0.0, 1.0, "#rho"};
+    AxisSpec nchBins = {100, -0.5, 99.5, "N_{ch}"};
+
+    registry.add("hFlattenicityTruth", "Truth flattenicity; 1-#rho; Events",
+                 HistType::kTH1D, {flatBins});
+    registry.add("hFlattenicityReco", "Reco flattenicity; 1-#rho; Events",
+                 HistType::kTH1D, {flatBins});
+    registry.add("hFlattenicityCorrelation", "Truth vs Reco; 1-#rho_{truth}; 1-#rho_{reco}",
+                 HistType::kTH2D, {flatBins, flatBins});
+    registry.add("hNch", "Reco Nch distribution; N_{ch}; Events",
+                 HistType::kTH1D, {nchBins});
+    registry.add("hNchTruth", "Truth Nch distribution; N_{ch}; Events",
+                 HistType::kTH1D, {nchBins});
+  }
+
+  // --- Track selection function ---
+  TrackSelection myTrackSelectionPrim()
+  {
+    TrackSelection selectedTracks;
+    selectedTracks.SetPtRange(0.1f, 1e10f);
+    selectedTracks.SetEtaRange(-0.8f, 0.8f);
+    selectedTracks.SetRequireITSRefit(true);
+    selectedTracks.SetRequireTPCRefit(true);
+    selectedTracks.SetMinNCrossedRowsTPC(70);
+    selectedTracks.SetMinNCrossedRowsOverFindableClustersTPC(0.4f);
+    selectedTracks.SetMaxChi2PerClusterTPC(4.0f);
+    selectedTracks.SetRequireHitsInITSLayers(1, {0, 1});
+    selectedTracks.SetMaxChi2PerClusterITS(36.0f);
+    selectedTracks.SetMaxDcaXYPtDep([](float pt) { return 0.0105f + 0.0350f / std::pow(pt, 1.1f); });
+    selectedTracks.SetMaxDcaZ(2.0f);
+    return selectedTracks;
+  }
+
+  // --- Helper: Get cell ID for a particle in FT0 acceptance ---
+  int getCellId(float eta, float phi)
+  {
+    // Check if in FT0-A acceptance
+    if (eta > FT0A_ETA_MIN && eta < FT0A_ETA_MAX) {
+      int phiBin = static_cast<int>(std::floor(phi / (2.0f * o2::constants::math::PI / static_cast<float>(NPHISECTORS))));
+      phiBin = std::clamp(phiBin, 0, NPHISECTORS - 1);
+      int etaBin = static_cast<int>(std::floor((eta - FT0A_ETA_MIN) / ((FT0A_ETA_MAX - FT0A_ETA_MIN) / static_cast<float>(NETA_A))));
+      etaBin = std::clamp(etaBin, 0, NETA_A - 1);
+      return etaBin * NPHISECTORS + phiBin;
+    }
+
+    // Check if in FT0-C acceptance
+    if (eta > FT0C_ETA_MIN && eta < FT0C_ETA_MAX) {
+      int phiBin = static_cast<int>(std::floor(phi / (2.0f * o2::constants::math::PI / static_cast<float>(NPHISECTORS))));
+      phiBin = std::clamp(phiBin, 0, NPHISECTORS - 1);
+      int etaBin = static_cast<int>(std::floor((eta - FT0C_ETA_MIN) / ((FT0C_ETA_MAX - FT0C_ETA_MIN) / static_cast<float>(NETA_C))));
+      etaBin = std::clamp(etaBin, 0, NETA_C - 1);
+      return NCH_A + etaBin * NPHISECTORS + phiBin;
+    }
+
+    return -1; // Not in FT0 acceptance
+  }
+
+  // --- Flattenicity calculation ---
+  float calculateFlattenicity(const std::vector<float>& counts)
+  {
+    if (counts.size() != static_cast<size_t>(NCELL)) {
+      return -1.0f;
+    }
+
+    float total = 0.0f;
+    for (const auto& c : counts) {
+      total += c;
+    }
+    if (total <= 0.0f) {
+      return -1.0f;
+    }
+
+    float mean = total / static_cast<float>(NCELL);
+    if (mean <= 0.0f) {
+      return -1.0f;
+    }
+
+    float sumSq = 0.0f;
+    for (const auto& c : counts) {
+      sumSq += (c - mean) * (c - mean);
+    }
+
+    float rho = std::sqrt(sumSq / (static_cast<float>(NCELL) * static_cast<float>(NCELL))) / mean;
+    return 1.0f - rho;
+  }
+
+  // --- Process Data ---
+  void processData(aod::Collision const& collision,
+                   soa::Filtered<aod::Tracks> const& tracks,
+                   aod::FT0s const& ft0s)
+  {
+    // Event selection (Paola/Jesus)
+    if (!collision.sel8()) {
+      return;
+    }
+    if (std::abs(collision.posZ()) >= VERTEX_CUT) {
+      return;
+    }
+
+    // Track loop for Nch
+    int nch = 0;
+    for (const auto& track : tracks) {
+      if (!mySelectionPrim.IsSelected(track)) {
+        continue;
+      }
+      nch++;
+    }
+    registry.fill(HIST("hNch"), nch);
+
+    // FT0 flattenicity
+    auto ft0 = collision.ft0();
+    if (ft0.hasAmplitudeA() && ft0.hasAmplitudeC()) {
+      auto ampA = ft0.amplitudeA();
+      auto ampC = ft0.amplitudeC();
+
+      std::vector<float> counts(NCELL, 0.0f);
+      for (int i = 0; i < static_cast<int>(ampA.size()) && i < NCH_A; ++i) {
+        counts[i] = ampA[i];
+      }
+      for (int i = 0; i < static_cast<int>(ampC.size()) && i < NCH_C; ++i) {
+        counts[NCH_A + i] = ampC[i];
+      }
+
+      float flat = calculateFlattenicity(counts);
+      if (flat >= FLAT_MIN) {
+        registry.fill(HIST("hFlattenicityReco"), flat);
+      }
+    }
+  }
+  PROCESS_SWITCH(FlattenicityTask, processData, "Process data", true);
+
+  // --- Process MC ---
+  void processMC(aod::McCollision const& mcCollision,
+                 aod::McParticles const& particles,
+                 soa::SmallGroups<soa::Join<aod::McCollisionLabels, aod::Collisions>> const& collisions,
+                 aod::FT0s const& ft0s,
+                 aod::BCs const& /*bcs*/)
+  {
+    // ---- Truth-level processing ----
+    bool inel = false;
+    int nchTruth = 0;
+    std::vector<float> truthCounts(NCELL, 0.0f);
+
+    for (const auto& particle : particles) {
+      // Check if physical primary
+      if (!particle.isPhysicalPrimary()) {
+        continue;
+      }
+
+      // Check if charged
+      if (std::abs(particle.pdgCode()) == 0) {
+        continue;
+      }
+
+      // Check pT > 0
+      if (particle.pt() <= 0.0f) {
+        continue;
+      }
+
+      // INEL>0 check: primary charged with |eta| < INEL_ETA_CUT
+      if (std::abs(particle.eta()) < INEL_ETA_CUT) {
+        inel = true;
+      }
+
+      // Nch at midrapidity: |eta| < MIDRAP_ETA_CUT, pT > cfgTrkLowPtCut
+      if (std::abs(particle.eta()) < MIDRAP_ETA_CUT && particle.pt() > cfgTrkLowPtCut) {
+        nchTruth++;
+      }
+
+      // Flattenicity: particles in FT0 acceptance
+      int cellId = getCellId(particle.eta(), particle.phi());
+      if (cellId >= 0 && cellId < NCELL) {
+        truthCounts[cellId] += 1.0f;
+      }
+    }
+
+    // Apply truth-level event selection (Paola/Jesus)
+    if (!inel) {
+      return;
+    }
+    if (std::abs(mcCollision.posZ()) >= VERTEX_CUT) {
+      return;
+    }
+
+    // Fill truth multiplicity
+    registry.fill(HIST("hNchTruth"), nchTruth);
+    registry.fill(HIST("hNch"), nchTruth);
+
+    // Calculate truth flattenicity
+    float truthFlat = calculateFlattenicity(truthCounts);
+    if (truthFlat >= FLAT_MIN) {
+      registry.fill(HIST("hFlattenicityTruth"), truthFlat);
+    }
+
+    // ---- Reconstructed-level processing for matched collisions ----
+    for (const auto& collision : collisions) {
+      // Apply reconstruction-level event selection
+      if (!collision.sel8()) {
+        continue;
+      }
+      if (std::abs(collision.posZ()) >= VERTEX_CUT) {
+        continue;
+      }
+
+      // Get FT0 flattenicity for this collision
+      auto ft0 = collision.ft0();
+      if (!ft0.hasAmplitudeA() || !ft0.hasAmplitudeC()) {
+        continue;
+      }
+
+      auto ampA = ft0.amplitudeA();
+      auto ampC = ft0.amplitudeC();
+
+      std::vector<float> recoCounts(NCELL, 0.0f);
+      for (int i = 0; i < static_cast<int>(ampA.size()) && i < NCH_A; ++i) {
+        recoCounts[i] = ampA[i];
+      }
+      for (int i = 0; i < static_cast<int>(ampC.size()) && i < NCH_C; ++i) {
+        recoCounts[NCH_A + i] = ampC[i];
+      }
+
+      float recoFlat = calculateFlattenicity(recoCounts);
+      if (recoFlat >= FLAT_MIN && truthFlat >= FLAT_MIN) {
+        registry.fill(HIST("hFlattenicityReco"), recoFlat);
+        registry.fill(HIST("hFlattenicityCorrelation"), truthFlat, recoFlat);
+      }
+    }
+  }
+  PROCESS_SWITCH(FlattenicityTask, processMC, "Process MC", true);
+};
+
+WorkflowSpec defineDataProcessing(ConfigContext const& cfgc)
+{
+  WorkflowSpec workflow{};
+  workflow.push_back(adaptAnalysisTask<FlattenicityTask>(cfgc));
+  return workflow;
+}