diHadronCor.cxx

// 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 diHadronCor.cxx
/// \brief di-hadron correlation for O-O, Pb-Pb collisions
/// \author Zhiyong Lu (zhiyong.lu@cern.ch)
/// \since  May/03/2025

#include "PWGCF/Core/CorrelationContainer.h"
#include "PWGCF/Core/PairCuts.h"
#include "PWGCF/DataModel/CorrelationsDerived.h"
#include "PWGCF/GenericFramework/Core/GFW.h"
#include "PWGCF/GenericFramework/Core/GFWCumulant.h"
#include "PWGCF/GenericFramework/Core/GFWPowerArray.h"
#include "PWGCF/GenericFramework/Core/GFWWeights.h"

#include "Common/Core/RecoDecay.h"
#include "Common/DataModel/Centrality.h"
#include "Common/DataModel/CollisionAssociationTables.h"
#include "Common/DataModel/EventSelection.h"
#include "Common/DataModel/Multiplicity.h"
#include "Common/DataModel/PIDResponse.h"
#include "Common/DataModel/PIDResponseITS.h"
#include "Common/DataModel/TrackSelectionTables.h"

#include "CommonConstants/MathConstants.h"
#include "DataFormatsParameters/GRPMagField.h"
#include "DataFormatsParameters/GRPObject.h"
#include "Framework/ASoAHelpers.h"
#include "Framework/AnalysisDataModel.h"
#include "Framework/AnalysisTask.h"
#include "Framework/HistogramRegistry.h"
#include "Framework/RunningWorkflowInfo.h"
#include "Framework/StepTHn.h"
#include "Framework/runDataProcessing.h"
#include "ReconstructionDataFormats/PID.h"
#include "ReconstructionDataFormats/Track.h"
#include <CCDB/BasicCCDBManager.h>

#include "TF1.h"
#include "TRandom3.h"
#include <TPDGCode.h>

#include <string>
#include <vector>

using namespace o2;
using namespace o2::framework;
using namespace o2::framework::expressions;

// define the filtered collisions and tracks
#define O2_DEFINE_CONFIGURABLE(NAME, TYPE, DEFAULT, HELP) Configurable<TYPE> NAME{#NAME, DEFAULT, HELP};

struct DiHadronCor {
  Service<ccdb::BasicCCDBManager> ccdb;

  O2_DEFINE_CONFIGURABLE(cfgCutVtxZ, float, 10.0f, "Accepted z-vertex range")
  O2_DEFINE_CONFIGURABLE(cfgCutPtMin, float, 0.2f, "minimum accepted track pT")
  O2_DEFINE_CONFIGURABLE(cfgCutPtMax, float, 10.0f, "maximum accepted track pT")
  O2_DEFINE_CONFIGURABLE(cfgCutEta, float, 0.8f, "Eta cut")
  O2_DEFINE_CONFIGURABLE(cfgCutChi2prTPCcls, float, 2.5f, "max chi2 per TPC clusters")
  O2_DEFINE_CONFIGURABLE(cfgCutTPCclu, float, 50.0f, "minimum TPC clusters")
  O2_DEFINE_CONFIGURABLE(cfgCutTPCCrossedRows, float, 70.0f, "minimum TPC crossed rows")
  O2_DEFINE_CONFIGURABLE(cfgCutITSclu, float, 5.0f, "minimum ITS clusters")
  O2_DEFINE_CONFIGURABLE(cfgCutDCAz, float, 2.0f, "max DCA to vertex z")
  O2_DEFINE_CONFIGURABLE(cfgCutMerging, float, 0.0, "Merging cut on track merge")
  O2_DEFINE_CONFIGURABLE(cfgSelCollByNch, bool, true, "Select collisions by Nch or centrality")
  O2_DEFINE_CONFIGURABLE(cfgCutMultMin, int, 0, "Minimum multiplicity for collision")
  O2_DEFINE_CONFIGURABLE(cfgCutMultMax, int, 10, "Maximum multiplicity for collision")
  O2_DEFINE_CONFIGURABLE(cfgCutCentMin, float, 60.0f, "Minimum centrality for collision")
  O2_DEFINE_CONFIGURABLE(cfgCutCentMax, float, 80.0f, "Maximum centrality for collision")
  O2_DEFINE_CONFIGURABLE(cfgMixEventNumMin, int, 5, "Minimum number of events to mix")
  O2_DEFINE_CONFIGURABLE(cfgRadiusLow, float, 0.8, "Low radius for merging cut")
  O2_DEFINE_CONFIGURABLE(cfgRadiusHigh, float, 2.5, "High radius for merging cut")
  O2_DEFINE_CONFIGURABLE(cfgSampleSize, double, 10, "Sample size for mixed event")
  O2_DEFINE_CONFIGURABLE(cfgCentEstimator, int, 0, "0:FT0C; 1:FT0CVariant1; 2:FT0M; 3:FT0A")
  O2_DEFINE_CONFIGURABLE(cfgCentTableUnavailable, bool, false, "if a dataset does not provide centrality information")
  O2_DEFINE_CONFIGURABLE(cfgUseAdditionalEventCut, bool, false, "Use additional event cut on mult correlations")
  O2_DEFINE_CONFIGURABLE(cfgEvSelkNoSameBunchPileup, bool, false, "rejects collisions which are associated with the same found-by-T0 bunch crossing")
  O2_DEFINE_CONFIGURABLE(cfgEvSelkNoITSROFrameBorder, bool, false, "reject events at ITS ROF border")
  O2_DEFINE_CONFIGURABLE(cfgEvSelkNoTimeFrameBorder, bool, false, "reject events at TF border")
  O2_DEFINE_CONFIGURABLE(cfgEvSelkIsGoodZvtxFT0vsPV, bool, false, "removes collisions with large differences between z of PV by tracks and z of PV from FT0 A-C time difference, use this cut at low multiplicities with caution")
  O2_DEFINE_CONFIGURABLE(cfgEvSelkNoCollInTimeRangeStandard, bool, false, "no collisions in specified time range")
  O2_DEFINE_CONFIGURABLE(cfgEvSelkIsGoodITSLayersAll, bool, true, "cut time intervals with dead ITS staves")
  O2_DEFINE_CONFIGURABLE(cfgEvSelkNoCollInRofStandard, bool, false, "no other collisions in this Readout Frame with per-collision multiplicity above threshold")
  O2_DEFINE_CONFIGURABLE(cfgEvSelkNoHighMultCollInPrevRof, bool, false, "veto an event if FT0C amplitude in previous ITS ROF is above threshold")
  O2_DEFINE_CONFIGURABLE(cfgEvSelMultCorrelation, bool, true, "Multiplicity correlation cut")
  O2_DEFINE_CONFIGURABLE(cfgEvSelV0AT0ACut, bool, true, "V0A T0A 5 sigma cut")
  O2_DEFINE_CONFIGURABLE(cfgEvSelOccupancy, bool, true, "Occupancy cut")
  O2_DEFINE_CONFIGURABLE(cfgCutOccupancyHigh, int, 2000, "High cut on TPC occupancy")
  O2_DEFINE_CONFIGURABLE(cfgCutOccupancyLow, int, 0, "Low cut on TPC occupancy")
  O2_DEFINE_CONFIGURABLE(cfgEfficiency, std::string, "", "CCDB path to efficiency object")
  O2_DEFINE_CONFIGURABLE(cfgLocalEfficiency, bool, false, "Use local efficiency object")
  O2_DEFINE_CONFIGURABLE(cfgVerbosity, bool, false, "Verbose output")
  O2_DEFINE_CONFIGURABLE(cfgUseEventWeights, bool, false, "Use event weights for mixed event")
  O2_DEFINE_CONFIGURABLE(cfgUsePtOrder, bool, true, "enable trigger pT < associated pT cut")
  O2_DEFINE_CONFIGURABLE(cfgUsePtOrderInMixEvent, bool, true, "enable trigger pT < associated pT cut in mixed event")
  O2_DEFINE_CONFIGURABLE(cfgPIDUseITSPID, bool, true, "Use ITS PID for particle identification")
  O2_DEFINE_CONFIGURABLE(cfgPIDTofPtCut, float, 0.5f, "Minimum pt to use TOF N-sigma")
  O2_DEFINE_CONFIGURABLE(cfgPIDParticle, int, 0, "1 = pion, 2 = kaon, 3 = proton, 0 for no PID")

  SliceCache cache;

  ConfigurableAxis axisVertex{"axisVertex", {10, -10, 10}, "vertex axis for histograms"};
  ConfigurableAxis axisMultiplicity{"axisMultiplicity", {VARIABLE_WIDTH, 0, 10, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260}, "multiplicity axis for histograms"};
  ConfigurableAxis axisCentrality{"axisCentrality", {VARIABLE_WIDTH, 0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100}, "centrality axis for histograms"};
  ConfigurableAxis axisPt{"axisPt", {VARIABLE_WIDTH, 0.2, 0.5, 1, 1.5, 2, 3, 4, 6, 10}, "pt axis for histograms"};
  ConfigurableAxis axisDeltaPhi{"axisDeltaPhi", {72, -PIHalf, PIHalf * 3}, "delta phi axis for histograms"};
  ConfigurableAxis axisDeltaEta{"axisDeltaEta", {48, -2.4, 2.4}, "delta eta axis for histograms"};
  ConfigurableAxis axisPtTrigger{"axisPtTrigger", {VARIABLE_WIDTH, 0.2, 0.5, 1, 1.5, 2, 3, 4, 6, 10}, "pt trigger axis for histograms"};
  ConfigurableAxis axisPtAssoc{"axisPtAssoc", {VARIABLE_WIDTH, 0.2, 0.5, 1, 1.5, 2, 3, 4, 6, 10}, "pt associated axis for histograms"};
  ConfigurableAxis axisVtxMix{"axisVtxMix", {VARIABLE_WIDTH, -10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10}, "vertex axis for mixed event histograms"};
  ConfigurableAxis axisMultMix{"axisMultMix", {VARIABLE_WIDTH, 0, 10, 20, 40, 60, 80, 100, 120, 140, 160, 180, 200, 220, 240, 260}, "multiplicity / centrality axis for mixed event histograms"};
  ConfigurableAxis axisSample{"axisSample", {cfgSampleSize, 0, cfgSampleSize}, "sample axis for histograms"};
  Configurable<std::vector<double>> pidTofNsigmaCut{"pidTofNsigmaCut", std::vector<double>{1.5, 1.5, 1.5, -1.5, -1.5, -1.5}, "TOF n-sigma cut for pions_posNsigma, kaons_posNsigma, protons_posNsigma, pions_negNsigma, kaons_negNsigma, protons_negNsigma"};
  Configurable<std::vector<double>> pidItsNsigmaCut{"pidItsNsigmaCut", std::vector<double>{3, 3, 3, -3, -3, -3}, "ITS n-sigma cut for pions_posNsigma, kaons_posNsigma, protons_posNsigma, pions_negNsigma, kaons_negNsigma, protons_negNsigma"};
  Configurable<std::vector<double>> pidTpcNsigmaCut{"pidTpcNsigmaCut", std::vector<double>{10, 10, 10, -10, -10, -10}, "TOF n-sigma cut for pions_posNsigma, kaons_posNsigma, protons_posNsigma, pions_negNsigma, kaons_negNsigma, protons_negNsigma"};

  ConfigurableAxis axisVertexEfficiency{"axisVertexEfficiency", {10, -10, 10}, "vertex axis for efficiency histograms"};
  ConfigurableAxis axisEtaEfficiency{"axisEtaEfficiency", {20, -1.0, 1.0}, "eta axis for efficiency histograms"};
  ConfigurableAxis axisPtEfficiency{"axisPtEfficiency", {VARIABLE_WIDTH, 0.2, 0.5, 1, 1.5, 2, 3, 4, 6, 10}, "pt axis for efficiency histograms"};

  // make the filters and cuts.
  Filter collisionFilter = (nabs(aod::collision::posZ) < cfgCutVtxZ);
  Filter trackFilter = (nabs(aod::track::eta) < cfgCutEta) && (aod::track::pt > cfgCutPtMin) && (aod::track::pt < cfgCutPtMax) && ((requireGlobalTrackInFilter()) || (aod::track::isGlobalTrackSDD == (uint8_t) true)) && (aod::track::tpcChi2NCl < cfgCutChi2prTPCcls) && (nabs(aod::track::dcaZ) < cfgCutDCAz);
  using FilteredCollisions = soa::Filtered<soa::Join<aod::Collisions, aod::EvSel, aod::CentFT0Cs, aod::CentFT0CVariant1s, aod::CentFT0Ms, aod::CentFV0As, aod::Mults>>;
  using FilteredTracks = soa::Filtered<soa::Join<aod::Tracks, aod::TrackSelection, aod::TracksExtra, aod::TracksDCA, aod::pidTPCFullPi, aod::pidTPCFullKa, aod::pidTPCFullPr, aod::pidTOFbeta, aod::pidTOFFullPi, aod::pidTOFFullKa, aod::pidTOFFullPr>>;
  using FilteredTracksWithMCLabels = soa::Filtered<soa::Join<aod::Tracks, aod::TrackSelection, aod::TracksExtra, aod::TracksDCA, aod::McTrackLabels>>;

  // Filter for MCParticle
  Filter particleFilter = (nabs(aod::mcparticle::eta) < cfgCutEta) && (aod::mcparticle::pt > cfgCutPtMin) && (aod::mcparticle::pt < cfgCutPtMax);
  using FilteredMcParticles = soa::Filtered<aod::McParticles>;

  // Filter for MCcollisions
  Filter mccollisionFilter = nabs(aod::mccollision::posZ) < cfgCutVtxZ;
  using FilteredMcCollisions = soa::Filtered<aod::McCollisions>;

  using SmallGroupMcCollisions = soa::SmallGroups<soa::Join<aod::McCollisionLabels, aod::Collisions, aod::EvSel, aod::CentFT0Cs, aod::CentFT0CVariant1s, aod::CentFT0Ms, aod::CentFV0As, aod::Mults>>;

  Preslice<aod::Tracks> perCollision = aod::track::collisionId;
  PresliceUnsorted<aod::McCollisionLabels> collisionPerMCCollision = aod::mccollisionlabel::mcCollisionId;

  // Corrections
  TH3D* mEfficiency = nullptr;
  bool correctionsLoaded = false;

  // Define the outputs
  OutputObj<CorrelationContainer> same{"sameEvent"};
  OutputObj<CorrelationContainer> mixed{"mixedEvent"};
  HistogramRegistry registry{"registry"};

  // define global variables
  TRandom3* gRandom = new TRandom3();
  enum CentEstimators {
    kCentFT0C = 0,
    kCentFT0CVariant1,
    kCentFT0M,
    kCentFV0A,
    // Count the total number of enum
    kCount_CentEstimators
  };
  enum EventType {
    SameEvent = 1,
    MixedEvent = 3
  };
  std::vector<double> tofNsigmaCut;
  std::vector<double> itsNsigmaCut;
  std::vector<double> tpcNsigmaCut;
  o2::aod::ITSResponse itsResponse;
  enum Particles {
    PIONS,
    KAONS,
    PROTONS
  };

  // persistent caches
  std::vector<float> efficiencyAssociatedCache;

  // Additional Event selection cuts - Copy from flowGenericFramework.cxx
  TF1* fMultPVCutLow = nullptr;
  TF1* fMultPVCutHigh = nullptr;
  TF1* fMultCutLow = nullptr;
  TF1* fMultCutHigh = nullptr;
  TF1* fMultMultPVCut = nullptr;
  TF1* fT0AV0AMean = nullptr;
  TF1* fT0AV0ASigma = nullptr;

  void init(InitContext&)
  {
    if (cfgCentTableUnavailable && !cfgSelCollByNch) {
      LOGF(fatal, "Centrality table is unavailable, cannot select collisions by centrality");
    }
    const AxisSpec axisPhi{72, 0.0, constants::math::TwoPI, "#varphi"};
    const AxisSpec axisEta{40, -1., 1., "#eta"};

    ccdb->setURL("http://alice-ccdb.cern.ch");
    ccdb->setCaching(true);
    auto now = std::chrono::duration_cast<std::chrono::milliseconds>(std::chrono::system_clock::now().time_since_epoch()).count();
    ccdb->setCreatedNotAfter(now);

    LOGF(info, "Starting init");

    // Event Counter
    if (doprocessSame && cfgUseAdditionalEventCut) {
      registry.add("hEventCountSpecific", "Number of Event;; Count", {HistType::kTH1D, {{12, 0, 12}}});
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(1, "after sel8");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(2, "kNoSameBunchPileup");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(3, "kNoITSROFrameBorder");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(4, "kNoTimeFrameBorder");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(5, "kIsGoodZvtxFT0vsPV");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(6, "kNoCollInTimeRangeStandard");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(7, "kIsGoodITSLayersAll");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(8, "kNoCollInRofStandard");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(9, "kNoHighMultCollInPrevRof");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(10, "occupancy");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(11, "MultCorrelation");
      registry.get<TH1>(HIST("hEventCountSpecific"))->GetXaxis()->SetBinLabel(12, "cfgEvSelV0AT0ACut");
    }

    if (cfgUseAdditionalEventCut) {
      fMultPVCutLow = new TF1("fMultPVCutLow", "[0]+[1]*x+[2]*x*x+[3]*x*x*x+[4]*x*x*x*x - 3.5*([5]+[6]*x+[7]*x*x+[8]*x*x*x+[9]*x*x*x*x)", 0, 100);
      fMultPVCutLow->SetParameters(3257.29, -121.848, 1.98492, -0.0172128, 6.47528e-05, 154.756, -1.86072, -0.0274713, 0.000633499, -3.37757e-06);
      fMultPVCutHigh = new TF1("fMultPVCutHigh", "[0]+[1]*x+[2]*x*x+[3]*x*x*x+[4]*x*x*x*x + 3.5*([5]+[6]*x+[7]*x*x+[8]*x*x*x+[9]*x*x*x*x)", 0, 100);
      fMultPVCutHigh->SetParameters(3257.29, -121.848, 1.98492, -0.0172128, 6.47528e-05, 154.756, -1.86072, -0.0274713, 0.000633499, -3.37757e-06);

      fMultCutLow = new TF1("fMultCutLow", "[0]+[1]*x+[2]*x*x+[3]*x*x*x - 2.*([4]+[5]*x+[6]*x*x+[7]*x*x*x+[8]*x*x*x*x)", 0, 100);
      fMultCutLow->SetParameters(1654.46, -47.2379, 0.449833, -0.0014125, 150.773, -3.67334, 0.0530503, -0.000614061, 3.15956e-06);
      fMultCutHigh = new TF1("fMultCutHigh", "[0]+[1]*x+[2]*x*x+[3]*x*x*x + 3.*([4]+[5]*x+[6]*x*x+[7]*x*x*x+[8]*x*x*x*x)", 0, 100);
      fMultCutHigh->SetParameters(1654.46, -47.2379, 0.449833, -0.0014125, 150.773, -3.67334, 0.0530503, -0.000614061, 3.15956e-06);

      fT0AV0AMean = new TF1("fT0AV0AMean", "[0]+[1]*x", 0, 200000);
      fT0AV0AMean->SetParameters(-1601.0581, 9.417652e-01);
      fT0AV0ASigma = new TF1("fT0AV0ASigma", "[0]+[1]*x+[2]*x*x+[3]*x*x*x+[4]*x*x*x*x", 0, 200000);
      fT0AV0ASigma->SetParameters(463.4144, 6.796509e-02, -9.097136e-07, 7.971088e-12, -2.600581e-17);
    }

    std::string hCentTitle = "Centrality distribution, Estimator " + std::to_string(cfgCentEstimator);
    // Make histograms to check the distributions after cuts
    if (doprocessSame) {
      registry.add("deltaEta_deltaPhi_same", "", {HistType::kTH2D, {axisDeltaPhi, axisDeltaEta}}); // check to see the delta eta and delta phi distribution
      registry.add("deltaEta_deltaPhi_mixed", "", {HistType::kTH2D, {axisDeltaPhi, axisDeltaEta}});
      registry.add("Phi", "Phi", {HistType::kTH1D, {axisPhi}});
      registry.add("Eta", "Eta", {HistType::kTH1D, {axisEta}});
      registry.add("EtaCorrected", "EtaCorrected", {HistType::kTH1D, {axisEta}});
      registry.add("pT", "pT", {HistType::kTH1D, {axisPtTrigger}});
      registry.add("pTCorrected", "pTCorrected", {HistType::kTH1D, {axisPtTrigger}});
      registry.add("Nch", "N_{ch}", {HistType::kTH1D, {axisMultiplicity}});
      registry.add("Nch_used", "N_{ch}", {HistType::kTH1D, {axisMultiplicity}}); // histogram to see how many events are in the same and mixed event
      registry.add("Centrality", hCentTitle.c_str(), {HistType::kTH1D, {axisCentrality}});
      registry.add("Centrality_used", hCentTitle.c_str(), {HistType::kTH1D, {axisCentrality}}); // histogram to see how many events are in the same and mixed event
      registry.add("zVtx", "zVtx", {HistType::kTH1D, {axisVertex}});
      registry.add("zVtx_used", "zVtx_used", {HistType::kTH1D, {axisVertex}});
      registry.add("Trig_hist", "", {HistType::kTHnSparseF, {{axisSample, axisVertex, axisPtTrigger}}});
    }

    registry.add("eventcount", "bin", {HistType::kTH1F, {{4, 0, 4, "bin"}}}); // histogram to see how many events are in the same and mixed event
    if (doprocessMCSame && doprocessOntheflySame) {
      LOGF(fatal, "Full simulation and on-the-fly processing of same event not supported");
    }
    if (doprocessMCMixed && doprocessOntheflyMixed) {
      LOGF(fatal, "Full simulation and on-the-fly processing of mixed event not supported");
    }
    if (doprocessMCSame || doprocessOntheflySame) {
      registry.add("MCTrue/MCeventcount", "MCeventcount", {HistType::kTH1F, {{5, 0, 5, "bin"}}}); // histogram to see how many events are in the same and mixed event
      registry.get<TH1>(HIST("MCTrue/MCeventcount"))->GetXaxis()->SetBinLabel(2, "same all");
      registry.get<TH1>(HIST("MCTrue/MCeventcount"))->GetXaxis()->SetBinLabel(3, "same reco");
      registry.get<TH1>(HIST("MCTrue/MCeventcount"))->GetXaxis()->SetBinLabel(4, "mixed all");
      registry.get<TH1>(HIST("MCTrue/MCeventcount"))->GetXaxis()->SetBinLabel(5, "mixed reco");
      registry.add("MCTrue/MCCentrality", hCentTitle.c_str(), {HistType::kTH1D, {axisCentrality}});
      registry.add("MCTrue/MCNch", "N_{ch}", {HistType::kTH1D, {axisMultiplicity}});
      registry.add("MCTrue/MCzVtx", "MCzVtx", {HistType::kTH1D, {axisVertex}});
      registry.add("MCTrue/MCPhi", "MCPhi", {HistType::kTH1D, {axisPhi}});
      registry.add("MCTrue/MCEta", "MCEta", {HistType::kTH1D, {axisEta}});
      registry.add("MCTrue/MCpT", "MCpT", {HistType::kTH1D, {axisPtTrigger}});
      registry.add("MCTrue/MCTrig_hist", "", {HistType::kTHnSparseF, {{axisSample, axisVertex, axisPtTrigger}}});
      registry.add("MCTrue/MCdeltaEta_deltaPhi_same", "", {HistType::kTH2D, {axisDeltaPhi, axisDeltaEta}}); // check to see the delta eta and delta phi distribution
      registry.add("MCTrue/MCdeltaEta_deltaPhi_mixed", "", {HistType::kTH2D, {axisDeltaPhi, axisDeltaEta}});
    }
    if (doprocessMCEfficiency) {
      registry.add("MCEffeventcount", "bin", {HistType::kTH1F, {{5, 0, 5, "bin"}}});
      registry.get<TH1>(HIST("MCEffeventcount"))->GetXaxis()->SetBinLabel(1, "All");
      registry.get<TH1>(HIST("MCEffeventcount"))->GetXaxis()->SetBinLabel(2, "MC");
      registry.get<TH1>(HIST("MCEffeventcount"))->GetXaxis()->SetBinLabel(3, "Reco Primary");
      registry.get<TH1>(HIST("MCEffeventcount"))->GetXaxis()->SetBinLabel(4, "Reco All");
      registry.get<TH1>(HIST("MCEffeventcount"))->GetXaxis()->SetBinLabel(5, "Fake");
    }

    LOGF(info, "Initializing correlation container");
    std::vector<AxisSpec> corrAxis = {{axisSample, "Sample"},
                                      {axisVertex, "z-vtx (cm)"},
                                      {axisPtTrigger, "p_{T} (GeV/c)"},
                                      {axisPtAssoc, "p_{T} (GeV/c)"},
                                      {axisDeltaPhi, "#Delta#varphi (rad)"},
                                      {axisDeltaEta, "#Delta#eta"}};
    std::vector<AxisSpec> effAxis = {
      {axisEtaEfficiency, "#eta"},
      {axisPtEfficiency, "p_{T} (GeV/c)"},
      {axisVertexEfficiency, "z-vtx (cm)"},
    };
    std::vector<AxisSpec> userAxis;

    same.setObject(new CorrelationContainer("sameEvent", "sameEvent", corrAxis, effAxis, userAxis));
    mixed.setObject(new CorrelationContainer("mixedEvent", "mixedEvent", corrAxis, effAxis, userAxis));

    tofNsigmaCut = pidTofNsigmaCut;
    itsNsigmaCut = pidItsNsigmaCut;
    tpcNsigmaCut = pidTpcNsigmaCut;

    LOGF(info, "End of init");
  }

  int getMagneticField(uint64_t timestamp)
  {
    // Get the magnetic field
    static o2::parameters::GRPMagField* grpo = nullptr;
    if (grpo == nullptr) {
      grpo = ccdb->getForTimeStamp<o2::parameters::GRPMagField>("/GLO/Config/GRPMagField", timestamp);
      if (grpo == nullptr) {
        LOGF(fatal, "GRP object not found for timestamp %llu", timestamp);
        return 0;
      }
      LOGF(info, "Retrieved GRP for timestamp %llu with magnetic field of %d kG", timestamp, grpo->getNominalL3Field());
    }
    return grpo->getNominalL3Field();
  }

  template <typename TCollision>
  float getCentrality(TCollision const& collision)
  {
    float cent;
    switch (cfgCentEstimator) {
      case kCentFT0C:
        cent = collision.centFT0C();
        break;
      case kCentFT0CVariant1:
        cent = collision.centFT0CVariant1();
        break;
      case kCentFT0M:
        cent = collision.centFT0M();
        break;
      case kCentFV0A:
        cent = collision.centFV0A();
        break;
      default:
        cent = collision.centFT0C();
    }
    return cent;
  }

  template <typename TTrack>
  bool trackSelected(TTrack track)
  {
    if (cfgPIDParticle && getNsigmaPID(track) != cfgPIDParticle) {
      return false;
    }
    return ((track.tpcNClsFound() >= cfgCutTPCclu) && (track.tpcNClsCrossedRows() >= cfgCutTPCCrossedRows) && (track.itsNCls() >= cfgCutITSclu));
  }

  template <typename TTrack>
  bool genTrackSelected(TTrack track)
  {
    if (!track.isPhysicalPrimary()) {
      return false;
    }
    if (!track.producedByGenerator()) {
      return false;
    }
    if (std::abs(track.eta()) > cfgCutEta) {
      return false;
    }
    if (std::abs(track.pt()) < cfgCutPtMin || std::abs(track.pt()) > cfgCutPtMax) {
      return false;
    }
    return true;
  }

  void loadEfficiency(uint64_t timestamp)
  {
    if (correctionsLoaded) {
      return;
    }
    if (cfgEfficiency.value.empty() == false) {
      if (cfgLocalEfficiency > 0) {
        TFile* fEfficiencyTrigger = TFile::Open(cfgEfficiency.value.c_str(), "READ");
        mEfficiency = reinterpret_cast<TH3D*>(fEfficiencyTrigger->Get("ccdb_object"));
      } else {
        mEfficiency = ccdb->getForTimeStamp<TH3D>(cfgEfficiency, timestamp);
      }
      if (mEfficiency == nullptr) {
        LOGF(fatal, "Could not load efficiency histogram for trigger particles from %s", cfgEfficiency.value.c_str());
      }
      LOGF(info, "Loaded efficiency histogram from %s (%p)", cfgEfficiency.value.c_str(), (void*)mEfficiency);
    }
    correctionsLoaded = true;
  }

  bool getEfficiencyCorrection(float& weight_nue, float eta, float pt, float posZ)
  {
    float eff = 1.;
    if (mEfficiency) {
      int etaBin = mEfficiency->GetXaxis()->FindBin(eta);
      int ptBin = mEfficiency->GetYaxis()->FindBin(pt);
      int zBin = mEfficiency->GetZaxis()->FindBin(posZ);
      eff = mEfficiency->GetBinContent(etaBin, ptBin, zBin);
    } else {
      eff = 1.0;
    }
    if (eff == 0)
      return false;
    weight_nue = 1. / eff;
    return true;
  }

  // fill multiple histograms
  template <typename TCollision, typename TTracks>
  void fillYield(TCollision collision, TTracks tracks) // function to fill the yield and etaphi histograms.
  {
    float weff1 = 1;
    float vtxz = collision.posZ();
    for (auto const& track1 : tracks) {
      if (!trackSelected(track1))
        continue;
      if (!getEfficiencyCorrection(weff1, track1.eta(), track1.pt(), vtxz))
        continue;
      registry.fill(HIST("Phi"), RecoDecay::constrainAngle(track1.phi(), 0.0));
      registry.fill(HIST("Eta"), track1.eta());
      registry.fill(HIST("EtaCorrected"), track1.eta(), weff1);
      registry.fill(HIST("pT"), track1.pt());
      registry.fill(HIST("pTCorrected"), track1.pt(), weff1);
    }
  }

  template <typename TTrack, typename TTrackAssoc>
  float getDPhiStar(TTrack const& track1, TTrackAssoc const& track2, float radius, int magField)
  {
    float charge1 = track1.sign();
    float charge2 = track2.sign();

    float phi1 = track1.phi();
    float phi2 = track2.phi();

    float pt1 = track1.pt();
    float pt2 = track2.pt();

    int fbSign = (magField > 0) ? 1 : -1;

    float dPhiStar = phi1 - phi2 - charge1 * fbSign * std::asin(0.075 * radius / pt1) + charge2 * fbSign * std::asin(0.075 * radius / pt2);

    if (dPhiStar > constants::math::PI)
      dPhiStar = constants::math::TwoPI - dPhiStar;
    if (dPhiStar < -constants::math::PI)
      dPhiStar = -constants::math::TwoPI - dPhiStar;

    return dPhiStar;
  }

  template <CorrelationContainer::CFStep step, typename TTracks, typename TTracksAssoc>
  void fillCorrelations(TTracks tracks1, TTracksAssoc tracks2, float posZ, int system, int magneticField, float cent, float eventWeight) // function to fill the Output functions (sparse) and the delta eta and delta phi histograms
  {
    // Cache efficiency for particles (too many FindBin lookups)
    if (mEfficiency) {
      efficiencyAssociatedCache.clear();
      efficiencyAssociatedCache.reserve(tracks2.size());
      for (const auto& track2 : tracks2) {
        float weff = 1.;
        getEfficiencyCorrection(weff, track2.eta(), track2.pt(), posZ);
        efficiencyAssociatedCache.push_back(weff);
      }
    }

    if (system == SameEvent) {
      if (!cfgCentTableUnavailable)
        registry.fill(HIST("Centrality_used"), cent);
      registry.fill(HIST("Nch_used"), tracks1.size());
    }

    int fSampleIndex = gRandom->Uniform(0, cfgSampleSize);

    float triggerWeight = 1.0f;
    float associatedWeight = 1.0f;
    // loop over all tracks
    for (auto const& track1 : tracks1) {

      if (!trackSelected(track1))
        continue;
      if (!getEfficiencyCorrection(triggerWeight, track1.eta(), track1.pt(), posZ))
        continue;
      if (system == SameEvent) {
        registry.fill(HIST("Trig_hist"), fSampleIndex, posZ, track1.pt(), eventWeight * triggerWeight);
      }

      for (auto const& track2 : tracks2) {

        if (!trackSelected(track2))
          continue;
        if (mEfficiency) {
          associatedWeight = efficiencyAssociatedCache[track2.filteredIndex()];
        }

        if (!cfgUsePtOrder && track1.globalIndex() == track2.globalIndex())
          continue; // For pt-differential correlations, skip if the trigger and associate are the same track
        if (cfgUsePtOrder && system == SameEvent && track1.pt() <= track2.pt())
          continue; // Without pt-differential correlations, skip if the trigger pt is less than the associate pt
        if (cfgUsePtOrder && system == MixedEvent && cfgUsePtOrderInMixEvent && track1.pt() <= track2.pt())
          continue; // For pt-differential correlations in mixed events, skip if the trigger pt is less than the associate pt

        float deltaPhi = RecoDecay::constrainAngle(track1.phi() - track2.phi(), -PIHalf);
        float deltaEta = track1.eta() - track2.eta();

        if (std::abs(deltaEta) < cfgCutMerging) {

          double dPhiStarHigh = getDPhiStar(track1, track2, cfgRadiusHigh, magneticField);
          double dPhiStarLow = getDPhiStar(track1, track2, cfgRadiusLow, magneticField);

          const double kLimit = 3.0 * cfgCutMerging;

          bool bIsBelow = false;

          if (std::abs(dPhiStarLow) < kLimit || std::abs(dPhiStarHigh) < kLimit || dPhiStarLow * dPhiStarHigh < 0) {
            for (double rad(cfgRadiusLow); rad < cfgRadiusHigh; rad += 0.01) {
              double dPhiStar = getDPhiStar(track1, track2, rad, magneticField);
              if (std::abs(dPhiStar) < kLimit) {
                bIsBelow = true;
                break;
              }
            }
            if (bIsBelow)
              continue;
          }
        }

        // fill the right sparse and histograms
        if (system == SameEvent) {

          same->getPairHist()->Fill(step, fSampleIndex, posZ, track1.pt(), track2.pt(), deltaPhi, deltaEta, eventWeight * triggerWeight * associatedWeight);
          registry.fill(HIST("deltaEta_deltaPhi_same"), deltaPhi, deltaEta, eventWeight * triggerWeight * associatedWeight);
        } else if (system == MixedEvent) {

          mixed->getPairHist()->Fill(step, fSampleIndex, posZ, track1.pt(), track2.pt(), deltaPhi, deltaEta, eventWeight * triggerWeight * associatedWeight);
          registry.fill(HIST("deltaEta_deltaPhi_mixed"), deltaPhi, deltaEta, eventWeight * triggerWeight * associatedWeight);
        }
      }
    }
  }
  template <CorrelationContainer::CFStep step, typename TTracks, typename TTracksAssoc>
  void fillMCCorrelations(TTracks tracks1, TTracksAssoc tracks2, float posZ, int system, float eventWeight) // function to fill the Output functions (sparse) and the delta eta and delta phi histograms
  {
    int fSampleIndex = gRandom->Uniform(0, cfgSampleSize);

    float triggerWeight = 1.0f;
    float associatedWeight = 1.0f;
    // loop over all tracks
    for (auto const& track1 : tracks1) {
      if (step >= CorrelationContainer::kCFStepTrackedOnlyPrim && !track1.isPhysicalPrimary())
        continue;
      if (doprocessOntheflySame && !genTrackSelected(track1))
        continue;

      if (system == SameEvent && (doprocessMCSame || doprocessOntheflySame))
        registry.fill(HIST("MCTrue/MCTrig_hist"), fSampleIndex, posZ, track1.pt(), eventWeight * triggerWeight);

      for (auto const& track2 : tracks2) {

        if (step >= CorrelationContainer::kCFStepTrackedOnlyPrim && !track2.isPhysicalPrimary())
          continue;
        if (doprocessOntheflyMixed && !genTrackSelected(track2))
          continue;

        if (!cfgUsePtOrder && track1.globalIndex() == track2.globalIndex())
          continue; // For pt-differential correlations, skip if the trigger and associate are the same track
        if (cfgUsePtOrder && system == SameEvent && track1.pt() <= track2.pt())
          continue; // Without pt-differential correlations, skip if the trigger pt is less than the associate pt
        if (cfgUsePtOrder && system == MixedEvent && cfgUsePtOrderInMixEvent && track1.pt() <= track2.pt())
          continue; // For pt-differential correlations in mixed events, skip if the trigger pt is less than the associate pt

        float deltaPhi = RecoDecay::constrainAngle(track1.phi() - track2.phi(), -PIHalf);
        float deltaEta = track1.eta() - track2.eta();

        // fill the right sparse and histograms
        if (system == SameEvent) {
          same->getPairHist()->Fill(step, fSampleIndex, posZ, track1.pt(), track2.pt(), deltaPhi, deltaEta, eventWeight * triggerWeight * associatedWeight);
          if (doprocessMCSame || doprocessOntheflySame)
            registry.fill(HIST("MCTrue/MCdeltaEta_deltaPhi_same"), deltaPhi, deltaEta, eventWeight * triggerWeight * associatedWeight);
        } else if (system == MixedEvent) {
          mixed->getPairHist()->Fill(step, fSampleIndex, posZ, track1.pt(), track2.pt(), deltaPhi, deltaEta, eventWeight * triggerWeight * associatedWeight);
          if (doprocessMCMixed || doprocessOntheflyMixed)
            registry.fill(HIST("MCTrue/MCdeltaEta_deltaPhi_mixed"), deltaPhi, deltaEta, eventWeight * triggerWeight * associatedWeight);
        }
      }
    }
  }

  template <typename TCollision>
  bool eventSelected(TCollision collision, const int multTrk, const float centrality, const bool fillCounter)
  {
    registry.fill(HIST("hEventCountSpecific"), 0.5);
    if (cfgEvSelkNoSameBunchPileup && !collision.selection_bit(o2::aod::evsel::kNoSameBunchPileup)) {
      // rejects collisions which are associated with the same "found-by-T0" bunch crossing
      // https://indico.cern.ch/event/1396220/#1-event-selection-with-its-rof
      return 0;
    }
    if (fillCounter && cfgEvSelkNoSameBunchPileup)
      registry.fill(HIST("hEventCountSpecific"), 1.5);
    if (cfgEvSelkNoITSROFrameBorder && !collision.selection_bit(o2::aod::evsel::kNoITSROFrameBorder)) {
      return 0;
    }
    if (fillCounter && cfgEvSelkNoITSROFrameBorder)
      registry.fill(HIST("hEventCountSpecific"), 2.5);
    if (cfgEvSelkNoTimeFrameBorder && !collision.selection_bit(o2::aod::evsel::kNoTimeFrameBorder)) {
      return 0;
    }
    if (fillCounter && cfgEvSelkNoTimeFrameBorder)
      registry.fill(HIST("hEventCountSpecific"), 3.5);
    if (cfgEvSelkIsGoodZvtxFT0vsPV && !collision.selection_bit(o2::aod::evsel::kIsGoodZvtxFT0vsPV)) {
      // removes collisions with large differences between z of PV by tracks and z of PV from FT0 A-C time difference
      // use this cut at low multiplicities with caution
      return 0;
    }
    if (fillCounter && cfgEvSelkIsGoodZvtxFT0vsPV)
      registry.fill(HIST("hEventCountSpecific"), 4.5);
    if (cfgEvSelkNoCollInTimeRangeStandard && !collision.selection_bit(o2::aod::evsel::kNoCollInTimeRangeStandard)) {
      // no collisions in specified time range
      return 0;
    }
    if (fillCounter && cfgEvSelkNoCollInTimeRangeStandard)
      registry.fill(HIST("hEventCountSpecific"), 5.5);
    if (cfgEvSelkIsGoodITSLayersAll && !collision.selection_bit(o2::aod::evsel::kIsGoodITSLayersAll)) {
      // from Jan 9 2025 AOT meeting
      // cut time intervals with dead ITS staves
      return 0;
    }
    if (fillCounter && cfgEvSelkIsGoodITSLayersAll)
      registry.fill(HIST("hEventCountSpecific"), 6.5);
    if (cfgEvSelkNoCollInRofStandard && !collision.selection_bit(o2::aod::evsel::kNoCollInRofStandard)) {
      // no other collisions in this Readout Frame with per-collision multiplicity above threshold
      return 0;
    }
    if (fillCounter && cfgEvSelkNoCollInRofStandard)
      registry.fill(HIST("hEventCountSpecific"), 7.5);
    if (cfgEvSelkNoHighMultCollInPrevRof && !collision.selection_bit(o2::aod::evsel::kNoHighMultCollInPrevRof)) {
      // veto an event if FT0C amplitude in previous ITS ROF is above threshold
      return 0;
    }
    if (fillCounter && cfgEvSelkNoHighMultCollInPrevRof)
      registry.fill(HIST("hEventCountSpecific"), 8.5);
    auto occupancy = collision.trackOccupancyInTimeRange();
    if (cfgEvSelOccupancy && (occupancy < cfgCutOccupancyLow || occupancy > cfgCutOccupancyHigh))
      return 0;
    if (fillCounter && cfgEvSelOccupancy)
      registry.fill(HIST("hEventCountSpecific"), 9.5);

    auto multNTracksPV = collision.multNTracksPV();
    if (cfgEvSelMultCorrelation) {
      if (multNTracksPV < fMultPVCutLow->Eval(centrality))
        return 0;
      if (multNTracksPV > fMultPVCutHigh->Eval(centrality))
        return 0;
      if (multTrk < fMultCutLow->Eval(centrality))
        return 0;
      if (multTrk > fMultCutHigh->Eval(centrality))
        return 0;
    }
    if (fillCounter && cfgEvSelMultCorrelation)
      registry.fill(HIST("hEventCountSpecific"), 10.5);

    // V0A T0A 5 sigma cut
    float sigma = 5.0;
    if (cfgEvSelV0AT0ACut && (std::fabs(collision.multFV0A() - fT0AV0AMean->Eval(collision.multFT0A())) > sigma * fT0AV0ASigma->Eval(collision.multFT0A())))
      return 0;
    if (fillCounter && cfgEvSelV0AT0ACut)
      registry.fill(HIST("hEventCountSpecific"), 11.5);

    return 1;
  }

  void processSame(FilteredCollisions::iterator const& collision, FilteredTracks const& tracks, aod::BCsWithTimestamps const&)
  {
    if (!collision.sel8())
      return;
    auto bc = collision.bc_as<aod::BCsWithTimestamps>();
    float cent = -1.;
    if (!cfgCentTableUnavailable)
      cent = getCentrality(collision);
    if (cfgUseAdditionalEventCut && !eventSelected(collision, tracks.size(), cent, true))
      return;

    if (!cfgCentTableUnavailable)
      registry.fill(HIST("Centrality"), cent);
    registry.fill(HIST("Nch"), tracks.size());
    registry.fill(HIST("zVtx"), collision.posZ());

    if (cfgSelCollByNch && (tracks.size() < cfgCutMultMin || tracks.size() >= cfgCutMultMax)) {
      return;
    }
    if (!cfgSelCollByNch && !cfgCentTableUnavailable && (cent < cfgCutCentMin || cent >= cfgCutCentMax)) {
      return;
    }

    loadEfficiency(bc.timestamp());
    registry.fill(HIST("eventcount"), SameEvent); // because its same event i put it in the 1 bin
    fillYield(collision, tracks);

    same->fillEvent(tracks.size(), CorrelationContainer::kCFStepReconstructed);
    fillCorrelations<CorrelationContainer::kCFStepReconstructed>(tracks, tracks, collision.posZ(), SameEvent, getMagneticField(bc.timestamp()), cent, 1.0f);
  }
  PROCESS_SWITCH(DiHadronCor, processSame, "Process same event", true);

  // the process for filling the mixed events
  void processMixed(FilteredCollisions const& collisions, FilteredTracks const& tracks, aod::BCsWithTimestamps const&)
  {

    auto getTracksSize = [&tracks, this](FilteredCollisions::iterator const& collision) {
      auto associatedTracks = tracks.sliceByCached(o2::aod::track::collisionId, collision.globalIndex(), this->cache);
      auto mult = associatedTracks.size();
      return mult;
    };

    using MixedBinning = FlexibleBinningPolicy<std::tuple<decltype(getTracksSize)>, aod::collision::PosZ, decltype(getTracksSize)>;

    MixedBinning binningOnVtxAndMult{{getTracksSize}, {axisVtxMix, axisMultMix}, true};

    auto tracksTuple = std::make_tuple(tracks, tracks);
    Pair<FilteredCollisions, FilteredTracks, FilteredTracks, MixedBinning> pairs{binningOnVtxAndMult, cfgMixEventNumMin, -1, collisions, tracksTuple, &cache}; // -1 is the number of the bin to skip
    for (auto it = pairs.begin(); it != pairs.end(); it++) {
      auto& [collision1, tracks1, collision2, tracks2] = *it;
      if (!collision1.sel8() || !collision2.sel8())
        continue;

      if (cfgSelCollByNch && (tracks1.size() < cfgCutMultMin || tracks1.size() >= cfgCutMultMax))
        continue;

      if (cfgSelCollByNch && (tracks2.size() < cfgCutMultMin || tracks2.size() >= cfgCutMultMax))
        continue;

      float cent1 = -1;
      float cent2 = -1;
      if (!cfgCentTableUnavailable) {
        cent1 = getCentrality(collision1);
        cent2 = getCentrality(collision2);
      }
      if (cfgUseAdditionalEventCut && !eventSelected(collision1, tracks1.size(), cent1, false))
        continue;
      if (cfgUseAdditionalEventCut && !eventSelected(collision2, tracks2.size(), cent2, false))
        continue;

      if (!cfgSelCollByNch && !cfgCentTableUnavailable && (cent1 < cfgCutCentMin || cent1 >= cfgCutCentMax))
        continue;

      if (!cfgSelCollByNch && !cfgCentTableUnavailable && (cent2 < cfgCutCentMin || cent2 >= cfgCutCentMax))
        continue;

      registry.fill(HIST("eventcount"), MixedEvent); // fill the mixed event in the 3 bin
      auto bc = collision1.bc_as<aod::BCsWithTimestamps>();
      loadEfficiency(bc.timestamp());
      float eventWeight = 1.0f;
      if (cfgUseEventWeights) {
        eventWeight = 1.0f / it.currentWindowNeighbours();
      }

      fillCorrelations<CorrelationContainer::kCFStepReconstructed>(tracks1, tracks2, collision1.posZ(), MixedEvent, getMagneticField(bc.timestamp()), cent1, eventWeight);
    }
  }

  PROCESS_SWITCH(DiHadronCor, processMixed, "Process mixed events", true);

  int getSpecies(int pdgCode)
  {
    switch (std::abs(pdgCode)) {
      case PDG_t::kPiPlus: // pion
        return 0;
      case PDG_t::kKPlus: // Kaon
        return 1;
      case PDG_t::kProton: // proton
        return 2;
      default: // NOTE. The efficiency histogram is hardcoded to contain 4 species. Anything special will have the last slot.
        return 3;
    }
  }

  void processMCEfficiency(FilteredMcCollisions::iterator const& mcCollision, soa::SmallGroups<soa::Join<aod::McCollisionLabels, aod::Collisions>> const& collisions, FilteredMcParticles const& mcParticles, FilteredTracksWithMCLabels const& tracks)
  {
    registry.fill(HIST("MCEffeventcount"), 0.5);
    if (cfgSelCollByNch && (mcParticles.size() < cfgCutMultMin || mcParticles.size() >= cfgCutMultMax)) {
      return;
    }
    // Primaries
    for (const auto& mcParticle : mcParticles) {
      if (mcParticle.isPhysicalPrimary()) {
        registry.fill(HIST("MCEffeventcount"), 1.5);
        same->getTrackHistEfficiency()->Fill(CorrelationContainer::MC, mcParticle.eta(), mcParticle.pt(), getSpecies(mcParticle.pdgCode()), 0., mcCollision.posZ());
      }
    }
    for (const auto& collision : collisions) {
      auto groupedTracks = tracks.sliceBy(perCollision, collision.globalIndex());
      if (cfgVerbosity) {
        LOGF(info, "  Reconstructed collision at vtx-z = %f", collision.posZ());
        LOGF(info, "  which has %d tracks", groupedTracks.size());
      }

      for (const auto& track : groupedTracks) {
        if (track.has_mcParticle()) {
          auto mcParticle = track.mcParticle();
          if (mcParticle.isPhysicalPrimary()) {
            registry.fill(HIST("MCEffeventcount"), 2.5);
            same->getTrackHistEfficiency()->Fill(CorrelationContainer::RecoPrimaries, mcParticle.eta(), mcParticle.pt(), getSpecies(mcParticle.pdgCode()), 0., mcCollision.posZ());
          }
          registry.fill(HIST("MCEffeventcount"), 3.5);
          same->getTrackHistEfficiency()->Fill(CorrelationContainer::RecoAll, mcParticle.eta(), mcParticle.pt(), getSpecies(mcParticle.pdgCode()), 0., mcCollision.posZ());
        } else {
          // fake track
          registry.fill(HIST("MCEffeventcount"), 4.5);
          same->getTrackHistEfficiency()->Fill(CorrelationContainer::Fake, track.eta(), track.pt(), 0, 0., mcCollision.posZ());
        }
      }
    }
  }
  PROCESS_SWITCH(DiHadronCor, processMCEfficiency, "MC: Extract efficiencies", false);

  void processMCSame(FilteredMcCollisions::iterator const& mcCollision, FilteredMcParticles const& mcParticles, SmallGroupMcCollisions const& collisions)
  {
    if (cfgVerbosity) {
      LOGF(info, "processMCSame. MC collision: %d, particles: %d, collisions: %d", mcCollision.globalIndex(), mcParticles.size(), collisions.size());
    }

    float cent = -1;
    if (!cfgCentTableUnavailable) {
      for (const auto& collision : collisions) {
        cent = getCentrality(collision);
      }
    }

    if (cfgSelCollByNch && (mcParticles.size() < cfgCutMultMin || mcParticles.size() >= cfgCutMultMax)) {
      return;
    }
    if (!cfgSelCollByNch && !cfgCentTableUnavailable && (cent < cfgCutCentMin || cent >= cfgCutCentMax)) {
      return;
    }

    registry.fill(HIST("MCTrue/MCeventcount"), SameEvent); // because its same event i put it in the 1 bin
    if (!cfgCentTableUnavailable)
      registry.fill(HIST("MCTrue/MCCentrality"), cent);
    registry.fill(HIST("MCTrue/MCNch"), mcParticles.size());
    registry.fill(HIST("MCTrue/MCzVtx"), mcCollision.posZ());
    for (const auto& mcParticle : mcParticles) {
      if (mcParticle.isPhysicalPrimary()) {
        registry.fill(HIST("MCTrue/MCPhi"), mcParticle.phi());
        registry.fill(HIST("MCTrue/MCEta"), mcParticle.eta());
        registry.fill(HIST("MCTrue/MCpT"), mcParticle.pt());
      }
    }

    same->fillEvent(mcParticles.size(), CorrelationContainer::kCFStepAll);
    fillMCCorrelations<CorrelationContainer::kCFStepAll>(mcParticles, mcParticles, mcCollision.posZ(), SameEvent, 1.0f);

    if (collisions.size() == 0) {
      return;
    }

    registry.fill(HIST("MCTrue/MCeventcount"), 2.5);
    same->fillEvent(mcParticles.size(), CorrelationContainer::kCFStepTrackedOnlyPrim);
    fillMCCorrelations<CorrelationContainer::kCFStepTrackedOnlyPrim>(mcParticles, mcParticles, mcCollision.posZ(), SameEvent, 1.0f);
  }
  PROCESS_SWITCH(DiHadronCor, processMCSame, "Process MC same event", false);

  void processMCMixed(FilteredMcCollisions const& mcCollisions, FilteredMcParticles const& mcParticles, SmallGroupMcCollisions const& collisions)
  {
    auto getTracksSize = [&mcParticles, this](FilteredMcCollisions::iterator const& mcCollision) {
      auto associatedTracks = mcParticles.sliceByCached(o2::aod::mcparticle::mcCollisionId, mcCollision.globalIndex(), this->cache);
      auto mult = associatedTracks.size();
      return mult;
    };

    using MixedBinning = FlexibleBinningPolicy<std::tuple<decltype(getTracksSize)>, o2::aod::mccollision::PosZ, decltype(getTracksSize)>;

    MixedBinning binningOnVtxAndMult{{getTracksSize}, {axisVtxMix, axisMultMix}, true};

    auto tracksTuple = std::make_tuple(mcParticles, mcParticles);
    Pair<FilteredMcCollisions, FilteredMcParticles, FilteredMcParticles, MixedBinning> pairs{binningOnVtxAndMult, cfgMixEventNumMin, -1, mcCollisions, tracksTuple, &cache}; // -1 is the number of the bin to skip
    for (auto it = pairs.begin(); it != pairs.end(); it++) {
      auto& [collision1, tracks1, collision2, tracks2] = *it;

      if (cfgSelCollByNch && (tracks1.size() < cfgCutMultMin || tracks1.size() >= cfgCutMultMax))
        continue;

      if (cfgSelCollByNch && (tracks2.size() < cfgCutMultMin || tracks2.size() >= cfgCutMultMax))
        continue;

      auto groupedCollisions = collisions.sliceBy(collisionPerMCCollision, collision1.globalIndex());
      if (cfgVerbosity > 0) {
        LOGF(info, "Found %d related collisions", groupedCollisions.size());
      }
      float cent = -1;
      if (!cfgCentTableUnavailable) {
        for (const auto& collision : groupedCollisions) {
          cent = getCentrality(collision);
        }
      }

      if (!cfgSelCollByNch && !cfgCentTableUnavailable && groupedCollisions.size() != 0 && (cent < cfgCutCentMin || cent >= cfgCutCentMax))
        continue;

      registry.fill(HIST("MCTrue/MCeventcount"), MixedEvent); // fill the mixed event in the 3 bin
      float eventWeight = 1.0f;
      if (cfgUseEventWeights) {
        eventWeight = 1.0f / it.currentWindowNeighbours();
      }

      fillMCCorrelations<CorrelationContainer::kCFStepAll>(tracks1, tracks2, collision1.posZ(), MixedEvent, eventWeight);

      if (groupedCollisions.size() == 0) {
        continue;
      }

      registry.fill(HIST("MCTrue/MCeventcount"), 4.5);
      fillMCCorrelations<CorrelationContainer::kCFStepTrackedOnlyPrim>(tracks1, tracks2, collision1.posZ(), MixedEvent, eventWeight);
    }
  }
  PROCESS_SWITCH(DiHadronCor, processMCMixed, "Process MC mixed events", false);

  void processOntheflySame(aod::McCollisions::iterator const& mcCollision, aod::McParticles const& mcParticles)
  {
    if (cfgVerbosity) {
      LOGF(info, "processOntheflySame. MC collision: %d, particles: %d", mcCollision.globalIndex(), mcParticles.size());
    }

    if (cfgSelCollByNch && (mcParticles.size() < cfgCutMultMin || mcParticles.size() >= cfgCutMultMax)) {
      return;
    }

    registry.fill(HIST("MCTrue/MCeventcount"), SameEvent); // because its same event i put it in the 1 bin
    registry.fill(HIST("MCTrue/MCNch"), mcParticles.size());
    registry.fill(HIST("MCTrue/MCzVtx"), mcCollision.posZ());
    for (const auto& mcParticle : mcParticles) {
      if (mcParticle.isPhysicalPrimary()) {
        registry.fill(HIST("MCTrue/MCPhi"), mcParticle.phi());
        registry.fill(HIST("MCTrue/MCEta"), mcParticle.eta());
        registry.fill(HIST("MCTrue/MCpT"), mcParticle.pt());
      }
    }

    same->fillEvent(mcParticles.size(), CorrelationContainer::kCFStepAll);
    fillMCCorrelations<CorrelationContainer::kCFStepAll>(mcParticles, mcParticles, mcCollision.posZ(), SameEvent, 1.0f);

    same->fillEvent(mcParticles.size(), CorrelationContainer::kCFStepTrackedOnlyPrim);
    fillMCCorrelations<CorrelationContainer::kCFStepTrackedOnlyPrim>(mcParticles, mcParticles, mcCollision.posZ(), SameEvent, 1.0f);
  }
  PROCESS_SWITCH(DiHadronCor, processOntheflySame, "Process on-the-fly same event", false);

  void processOntheflyMixed(aod::McCollisions const& mcCollisions, aod::McParticles const& mcParticles)
  {
    auto getTracksSize = [&mcParticles, this](aod::McCollisions::iterator const& mcCollision) {
      auto associatedTracks = mcParticles.sliceByCached(o2::aod::mcparticle::mcCollisionId, mcCollision.globalIndex(), this->cache);
      auto mult = associatedTracks.size();
      return mult;
    };

    using MixedBinning = FlexibleBinningPolicy<std::tuple<decltype(getTracksSize)>, o2::aod::mccollision::PosZ, decltype(getTracksSize)>;

    MixedBinning binningOnVtxAndMult{{getTracksSize}, {axisVtxMix, axisMultMix}, true};

    auto tracksTuple = std::make_tuple(mcParticles, mcParticles);
    Pair<aod::McCollisions, aod::McParticles, aod::McParticles, MixedBinning> pairs{binningOnVtxAndMult, cfgMixEventNumMin, -1, mcCollisions, tracksTuple, &cache}; // -1 is the number of the bin to skip
    for (auto it = pairs.begin(); it != pairs.end(); it++) {
      auto& [collision1, tracks1, collision2, tracks2] = *it;

      if (cfgSelCollByNch && (tracks1.size() < cfgCutMultMin || tracks1.size() >= cfgCutMultMax))
        continue;

      if (cfgSelCollByNch && (tracks2.size() < cfgCutMultMin || tracks2.size() >= cfgCutMultMax))
        continue;

      registry.fill(HIST("MCTrue/MCeventcount"), MixedEvent); // fill the mixed event in the 3 bin
      float eventWeight = 1.0f;
      if (cfgUseEventWeights) {
        eventWeight = 1.0f / it.currentWindowNeighbours();
      }

      fillMCCorrelations<CorrelationContainer::kCFStepAll>(tracks1, tracks2, collision1.posZ(), MixedEvent, eventWeight);

      fillMCCorrelations<CorrelationContainer::kCFStepTrackedOnlyPrim>(tracks1, tracks2, collision1.posZ(), MixedEvent, eventWeight);
    }
  }
  PROCESS_SWITCH(DiHadronCor, processOntheflyMixed, "Process on-the-fly mixed events", false);

  template <typename TTrack>
  int getNsigmaPID(TTrack track)
  {
    // Computing Nsigma arrays for pion, kaon, and protons
    std::array<float, 3> nSigmaTPC = {track.tpcNSigmaPi(), track.tpcNSigmaKa(), track.tpcNSigmaPr()};
    std::array<float, 3> nSigmaTOF = {track.tofNSigmaPi(), track.tofNSigmaKa(), track.tofNSigmaPr()};
    std::array<float, 3> nSigmaITS = {itsResponse.nSigmaITS<o2::track::PID::Pion>(track), itsResponse.nSigmaITS<o2::track::PID::Kaon>(track), itsResponse.nSigmaITS<o2::track::PID::Proton>(track)};
    int pid = -1;

    std::array<float, 3> nSigmaToUse = cfgPIDUseITSPID ? nSigmaITS : nSigmaTPC;            // Choose which nSigma to use: TPC or ITS
    std::vector<double> detectorNsigmaCut = cfgPIDUseITSPID ? itsNsigmaCut : tpcNsigmaCut; // Choose which nSigma to use: TPC or ITS

    bool isPion, isKaon, isProton;
    bool isDetectedPion = nSigmaToUse[0] < detectorNsigmaCut[0] && nSigmaToUse[0] > detectorNsigmaCut[0 + 3];
    bool isDetectedKaon = nSigmaToUse[1] < detectorNsigmaCut[1] && nSigmaToUse[1] > detectorNsigmaCut[1 + 3];
    bool isDetectedProton = nSigmaToUse[2] < detectorNsigmaCut[2] && nSigmaToUse[2] > detectorNsigmaCut[2 + 3];

    bool isTofPion = nSigmaTOF[0] < tofNsigmaCut[0] && nSigmaTOF[0] > tofNsigmaCut[0 + 3];
    bool isTofKaon = nSigmaTOF[1] < tofNsigmaCut[1] && nSigmaTOF[1] > tofNsigmaCut[1 + 3];
    bool isTofProton = nSigmaTOF[2] < tofNsigmaCut[2] && nSigmaTOF[2] > tofNsigmaCut[2 + 3];

    if (track.pt() > cfgPIDTofPtCut && !track.hasTOF()) {
      return 0;
    } else if (track.pt() > cfgPIDTofPtCut && track.hasTOF()) {
      isPion = isTofPion && isDetectedPion;
      isKaon = isTofKaon && isDetectedKaon;
      isProton = isTofProton && isDetectedProton;
    } else {
      isPion = isDetectedPion;
      isKaon = isDetectedKaon;
      isProton = isDetectedProton;
    }

    if ((isPion && isKaon) || (isPion && isProton) || (isKaon && isProton)) {
      return 0; // more than one particle satisfy the criteria
    }

    if (isPion) {
      pid = PIONS;
    } else if (isKaon) {
      pid = KAONS;
    } else if (isProton) {
      pid = PROTONS;
    } else {
      return 0; // no particle satisfies the criteria
    }

    return pid + 1; // shift the pid by 1, 1 = pion, 2 = kaon, 3 = proton
  }
};

WorkflowSpec defineDataProcessing(ConfigContext const& cfgc)
{
  return WorkflowSpec{
    adaptAnalysisTask<DiHadronCor>(cfgc),
  };
}