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[PWGCF] Updated Nch calculation used in tracks counter #16475

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5a95273
Updated the Nch correction used in the track counter
Thorkj May 31, 2026
b8bb9aa
[PWGCF] Updated Nch correction in track counter
Thorkj May 31, 2026
541cae0
Fix to o2 linter error
Thorkj May 31, 2026
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159 changes: 126 additions & 33 deletions PWGCF/TwoParticleCorrelations/Tasks/corrFit.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -71,6 +71,12 @@ struct CorrFit {
O2_DEFINE_CONFIGURABLE(cfgUseTransverseMomentum, bool, false, "Use transverse momentum for correlation container")
O2_DEFINE_CONFIGURABLE(cfgQaCheck, bool, true, "Enable QA histograms for event selection")
O2_DEFINE_CONFIGURABLE(cfgStrictTrackCounter, bool, false, "Strict track counter for multiplicity correlation cut, counts only tracks that pass all cuts and are used in the correlation")
O2_DEFINE_CONFIGURABLE(cfgRefpTt, bool, false, "Apply upper pT cut on reference tracks")
O2_DEFINE_CONFIGURABLE(cfgRefpTMax, float, 3.0f, "maximum pT for reference tracks if cfgRefpTt is true")
O2_DEFINE_CONFIGURABLE(cfgMinMultForCorrelations, int, 0, "minimum multiplicity for correlations")
O2_DEFINE_CONFIGURABLE(cfgMaxMultForCorrelations, int, 20, "maximum multiplicity for correlations")
O2_DEFINE_CONFIGURABLE(cfgRefMultiplicity, bool, false, "Use multiplicity of reference tracks for multiplicity correlation cut instead of Nch")

struct : ConfigurableGroup{
O2_DEFINE_CONFIGURABLE(cfgPtCutMin, float, 0.2f, "minimum accepted track pT")
O2_DEFINE_CONFIGURABLE(cfgPtCutMax, float, 10.0f, "maximum accepted track pT")
Expand Down Expand Up @@ -116,8 +122,10 @@ struct CorrFit {
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(cfgEfficiency, std::string, "", "CCDB path to efficiency object")
O2_DEFINE_CONFIGURABLE(cfgEfficiencyNch, std::string, "", "CCDB path to multiplicity dependent efficiency object")
O2_DEFINE_CONFIGURABLE(cfgCentralityWeight, std::string, "", "CCDB path to centrality weight object")
O2_DEFINE_CONFIGURABLE(cfgLocalEfficiency, bool, false, "Use local efficiency object")
O2_DEFINE_CONFIGURABLE(cfgLocalEfficiencyNch, bool, false, "Use local multiplicity dependent efficiency object");
O2_DEFINE_CONFIGURABLE(cfgUseEventWeights, bool, false, "Use event weights for mixed event")

struct : ConfigurableGroup {
Expand Down Expand Up @@ -167,7 +175,7 @@ struct CorrFit {
ConfigurableAxis axisDeltaEtaTpcFt0a{"axisDeltaEtaTpcFt0a", {32, -5.8, -2.6}, "delta eta axis, -5.8~-2.6 for TPC-FT0A,"};
ConfigurableAxis axisDeltaEtaTpcFt0c{"axisDeltaEtaTpcFt0c", {32, 1.2, 4.2}, "delta eta axis, 1.2~4.2 for TPC-FT0C"};
ConfigurableAxis axisDeltaEtaFt0aFt0c{"axisDeltaEtaFt0aFt0c", {32, -1.5, 3.0}, "delta eta axis"};
ConfigurableAxis axisDeltaEtaTpcTpc{"axisDeltaEtaTpcTpc", {32, -0.8, 0.8}, "delta eta axis for TPC-TPC"};
ConfigurableAxis axisDeltaEtaTpcTpc{"axisDeltaEtaTpcTpc", {32, -1.6, 1.6}, "delta eta axis for TPC-TPC"};
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"};
Expand Down Expand Up @@ -200,6 +208,7 @@ struct CorrFit {

// Corrections
TH3D* mEfficiency = nullptr;
TH1D* mEfficiencyNch = nullptr;
TH1D* mCentralityWeight = nullptr;
bool correctionsLoaded = false;

Expand Down Expand Up @@ -288,6 +297,9 @@ struct CorrFit {
registry.add("FT0Amp", "", {HistType::kTH2F, {axisChID, axisFit}});
registry.add("FT0AmpCorrect", "", {HistType::kTH2F, {axisChID, axisFit}});
}
if (cfgQaCheck) {
registry.add("Nch_corrected", "N_{ch} corrected", {HistType::kTH1D, {axisMult}});
}
}

if (doprocessSameTpcFt0a) {
Expand Down Expand Up @@ -353,7 +365,7 @@ struct CorrFit {
{axisPtTrigger, "p_{T} (GeV/c)"},
{axisMult, "N_{ch}"},
{axisDeltaPhi, "#Delta#varphi (rad)"},
{axisDeltaEtaTpcFt0a, "#Delta#eta"}}; // use the same delta eta axis for TPC-TPC correlation
{axisDeltaEtaTpcTpc, "#Delta#eta"}}; // use the same delta eta axis for TPC-TPC correlation

if (doprocessSameTpcFt0a) {
sameTpcFt0a.setObject(new CorrelationContainer("sameEvent_TPC_FT0A", "sameEvent_TPC_FT0A", corrAxisTpcFt0a, effAxis, userAxis));
Expand Down Expand Up @@ -673,9 +685,10 @@ struct CorrFit {
return;
}
if (cfgEfficiency.value.empty() == false) {
if (cfgLocalEfficiency > 0) {
if (cfgLocalEfficiency) {
TFile* fEfficiencyTrigger = TFile::Open(cfgEfficiency.value.c_str(), "READ");
mEfficiency = reinterpret_cast<TH3D*>(fEfficiencyTrigger->Get("ccdb_object"));

} else {
mEfficiency = ccdb->getForTimeStamp<TH3D>(cfgEfficiency, timestamp);
}
Expand All @@ -684,6 +697,19 @@ struct CorrFit {
}
LOGF(info, "Loaded efficiency histogram from %s (%p)", cfgEfficiency.value.c_str(), (void*)mEfficiency);
}
if (cfgEfficiencyNch.value.empty() == false) {
if (cfgLocalEfficiencyNch) {
TFile* fEfficiencyTrigger = TFile::Open(cfgEfficiencyNch.value.c_str(), "READ");
mEfficiencyNch = reinterpret_cast<TH1D*>(fEfficiencyTrigger->Get("ccdb_object"));

} else {
mEfficiencyNch = ccdb->getForTimeStamp<TH1D>(cfgEfficiencyNch, timestamp);
}
if (!mEfficiencyNch) {
LOGF(fatal, "Could not load efficiency histogram for trigger particles from %s", cfgEfficiencyNch.value.c_str());
}
LOGF(info, "Loaded efficiency histogram from %s (%p)", cfgEfficiencyNch.value.c_str(), (void*)mEfficiencyNch);
}
if (cfgCentralityWeight.value.empty() == false) {
mCentralityWeight = ccdb->getForTimeStamp<TH1D>(cfgCentralityWeight, timestamp);
if (mCentralityWeight == nullptr) {
Expand All @@ -694,20 +720,39 @@ struct CorrFit {
correctionsLoaded = true;
}

bool getEfficiencyCorrection(float& weight_nue, float eta, float pt, float posZ)
bool getEfficiencyCorrection_Nch(float& weight_Nch, float pt)
{
float eff_Nch = 1.;
if (mEfficiencyNch) {

int ptBin = mEfficiencyNch->FindBin(pt);
eff_Nch = mEfficiencyNch->GetBinContent(ptBin);

} else {
eff_Nch = 1.0;
}
if (eff_Nch == 0)
return false;
weight_Nch = 1. / eff_Nch;
return true;
}

bool getEfficiencyCorrection(float& weight, float pt, float eta, float vertex)
{
float eff = 1.;
if (mEfficiency) {
int etaBin = mEfficiency->GetXaxis()->FindBin(eta);

int etaBin = mEfficiency->GetXaxis()->FindBin(eta); // use the eta bin corresponding to eta=0 for the trigger particle efficiency
int ptBin = mEfficiency->GetYaxis()->FindBin(pt);
int zBin = mEfficiency->GetZaxis()->FindBin(posZ);
eff = mEfficiency->GetBinContent(etaBin, ptBin, zBin);
int vertexBin = mEfficiency->GetZaxis()->FindBin(vertex); // use the vertex bin corresponding to z=0 for the trigger particle efficiency
eff = mEfficiency->GetBinContent(etaBin, ptBin, vertexBin);

} else {
eff = 1.0;
}
if (eff == 0)
return false;
weight_nue = 1. / eff;
weight = 1. / eff;
return true;
}

Expand All @@ -727,16 +772,24 @@ struct CorrFit {
}

template <typename TTracks>
void trackCounter(TTracks tracks, int& multiplicity) // function to count the number of tracks in the event and fill the histogram
void trackCounter(TTracks tracks, double& multiplicity) // function to count the number of tracks in the event and fill the histogram
{
int mult = 0;
double nTracksCorrected = 0;
float weight_Nch = 1.0f;
for (auto const& track : tracks) {

if (!trackSelected(track))
if (cfgRefMultiplicity) {
if (track.pt() > cfgRefpTMax)
continue;
}

if (!getEfficiencyCorrection_Nch(weight_Nch, track.pt())) {
continue;
mult++;
}

nTracksCorrected += weight_Nch;
}
multiplicity = mult;
multiplicity = nTracksCorrected;
}

template <CorrelationContainer::CFStep step, typename TTracks, typename TFT0s>
Expand All @@ -757,7 +810,7 @@ struct CorrFit {
continue;
}

if (!getEfficiencyCorrection(triggerWeight, track1.eta(), track1.pt(), posZ))
if (!getEfficiencyCorrection(triggerWeight, track1.pt(), track1.eta(), posZ))
continue;

if (system == SameEvent) {
Expand Down Expand Up @@ -828,13 +881,15 @@ struct CorrFit {

float weff1 = 1.0;
float zvtx = collision.posZ();
registry.fill(HIST("zVtx"), zvtx);
registry.fill(HIST("Nch"), tracks.size());

for (auto const& track1 : tracks) {

if (!trackSelected(track1)) {
continue;
}
if (!getEfficiencyCorrection(weff1, track1.eta(), track1.pt(), zvtx)) {
if (!getEfficiencyCorrection_Nch(weff1, track1.pt())) {
continue;
}

Expand Down Expand Up @@ -903,18 +958,15 @@ struct CorrFit {

float triggerWeight = 1.0f;

float associateWeight = 1.0f;

// loop over all tracks
for (auto const& track1 : tracks1) {

if (!trackSelected(track1))
continue;

if (cfgSystematics.cfgSystematicsVariation) {
if (!trackSelectedSystematics(track1))
continue;
}

if (!getEfficiencyCorrection(triggerWeight, track1.eta(), track1.pt(), posZ))
if (!getEfficiencyCorrection_Nch(triggerWeight, track1.pt()))
continue;

if (system == SameEvent) {
Expand All @@ -926,6 +978,14 @@ struct CorrFit {
if (!trackSelected(track2))
continue;

if (!getEfficiencyCorrection_Nch(associateWeight, track2.pt()))
continue;

if (cfgRefpTt) {
if (track2.pt() > cfgRefpTMax) {
continue;
}
}
if (track1.pt() <= track2.pt())
continue; // skip if the trigger pt is less than the associate pt

Expand Down Expand Up @@ -957,16 +1017,16 @@ struct CorrFit {
// fill the right sparse and histograms
if (system == SameEvent) {

sameTPC->getPairHist()->Fill(step, fSampleIndex, posZ, track1.pt(), multiplicity, deltaPhi, deltaEta);
sameTPC->getPairHist()->Fill(step, fSampleIndex, posZ, track1.pt(), multiplicity, deltaPhi, deltaEta, triggerWeight * associateWeight);
if (cfgQaCheck) {
registry.fill(HIST("deltaEta_deltaPhi_same_TPC"), deltaPhi, deltaEta);
registry.fill(HIST("deltaEta_deltaPhi_same_TPC"), deltaPhi, deltaEta, triggerWeight * associateWeight);
}
} else if (system == MixedEvent) {

mixedTPC->getPairHist()->Fill(step, fSampleIndex, posZ, track1.pt(), multiplicity, deltaPhi, deltaEta);
mixedTPC->getPairHist()->Fill(step, fSampleIndex, posZ, track1.pt(), multiplicity, deltaPhi, deltaEta, triggerWeight * associateWeight);

if (cfgQaCheck) {
registry.fill(HIST("deltaEta_deltaPhi_mixed_TPC"), deltaPhi, deltaEta);
registry.fill(HIST("deltaEta_deltaPhi_mixed_TPC"), deltaPhi, deltaEta, triggerWeight * associateWeight);
}
}
}
Expand Down Expand Up @@ -1004,12 +1064,20 @@ struct CorrFit {

fillYield(collision, tracks);

int multiplicity = tracks.size();
double multiplicity = tracks.size();

if (cfgStrictTrackCounter) {
trackCounter(tracks, multiplicity);
}

if (cfgQaCheck) {
registry.fill(HIST("Nch_corrected"), multiplicity);
}

if (multiplicity > cfgMaxMultForCorrelations || multiplicity < cfgMinMultForCorrelations) {
return;
}

const auto& ft0 = collision.foundFT0();
fillCorrelationsTPCFT0<CorrelationContainer::kCFStepReconstructed>(tracks, ft0, collision.posZ(), SameEvent, multiplicity, kFT0A, eventWeight);
}
Expand Down Expand Up @@ -1054,12 +1122,16 @@ struct CorrFit {
loadCorrection(bc.timestamp());
float eventWeight = 1.0f;

int multiplicity = tracks1.size();
double multiplicity = tracks1.size();

if (cfgStrictTrackCounter) {
trackCounter(tracks1, multiplicity);
}

if (cfgQaCheck) {
registry.fill(HIST("Nch_corrected"), multiplicity);
}

const auto& ft0 = collision2.foundFT0();
fillCorrelationsTPCFT0<CorrelationContainer::kCFStepReconstructed>(tracks1, ft0, collision1.posZ(), MixedEvent, multiplicity, kFT0A, eventWeight);
}
Expand Down Expand Up @@ -1095,12 +1167,16 @@ struct CorrFit {

const auto& ft0 = collision.foundFT0();

int multiplicity = tracks.size();
double multiplicity = tracks.size();

if (cfgStrictTrackCounter) {
trackCounter(tracks, multiplicity);
}

if (cfgQaCheck) {
registry.fill(HIST("Nch_corrected"), multiplicity);
}

fillCorrelationsTPCFT0<CorrelationContainer::kCFStepReconstructed>(tracks, ft0, collision.posZ(), SameEvent, multiplicity, kFT0C, 1.0f);
}
PROCESS_SWITCH(CorrFit, processSameTpcFt0c, "Process same event for TPC-FT0C correlation", false);
Expand Down Expand Up @@ -1144,12 +1220,16 @@ struct CorrFit {
float eventWeight = 1.0f;

const auto& ft0 = collision2.foundFT0();
int multiplicity = tracks1.size();
double multiplicity = tracks1.size();

if (cfgStrictTrackCounter) {
trackCounter(tracks, multiplicity);
}

if (cfgQaCheck) {
registry.fill(HIST("Nch_corrected"), multiplicity);
}

fillCorrelationsTPCFT0<CorrelationContainer::kCFStepReconstructed>(tracks1, ft0, collision1.posZ(), MixedEvent, multiplicity, kFT0C, eventWeight);
}
}
Expand Down Expand Up @@ -1187,12 +1267,16 @@ struct CorrFit {

registry.fill(HIST("eventcount"), SameEvent); // because its same event i put it in the 1 bin

int multiplicity = tracks.size();
double multiplicity = tracks.size();

if (cfgStrictTrackCounter) {
trackCounter(tracks, multiplicity);
}

if (cfgQaCheck) {
registry.fill(HIST("Nch_corrected"), multiplicity);
}

fillCorrelationsFT0AFT0C<CorrelationContainer::kCFStepReconstructed>(ft0, ft0, collision.posZ(), SameEvent, multiplicity, eventWeight);
}
PROCESS_SWITCH(CorrFit, processSameFt0aFt0c, "Process same event for FT0A-FT0C correlation", true);
Expand Down Expand Up @@ -1238,12 +1322,15 @@ struct CorrFit {
const auto& ft0Col1 = collision1.foundFT0();
const auto& ft0Col2 = collision2.foundFT0();

int multiplicity = tracks1.size();
double multiplicity = tracks1.size();

if (cfgStrictTrackCounter) {
trackCounter(tracks1, multiplicity);
}

if (cfgQaCheck) {
registry.fill(HIST("Nch_corrected"), multiplicity);
}
registry.fill(HIST("eventcount"), MixedEvent); // fill the mixed event in the 3 bin

fillCorrelationsFT0AFT0C<CorrelationContainer::kCFStepReconstructed>(ft0Col1, ft0Col2, collision1.posZ(), MixedEvent, multiplicity, eventWeight);
Expand All @@ -1269,15 +1356,20 @@ struct CorrFit {
return;

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

fillYield(collision, tracks);

int multiplicity = tracks.size();
double multiplicity = tracks.size();

if (cfgStrictTrackCounter) {
trackCounter(tracks, multiplicity);
}

if (cfgQaCheck) {
registry.fill(HIST("Nch_corrected"), multiplicity);
}

fillCorrelations<CorrelationContainer::kCFStepReconstructed>(tracks, tracks, collision.posZ(), SameEvent, multiplicity, getMagneticField(bc.timestamp()));
}
PROCESS_SWITCH(CorrFit, processSameTPC, "Process same event for TPC-TPC correlation", false);
Expand Down Expand Up @@ -1312,8 +1404,9 @@ struct CorrFit {
continue;

registry.fill(HIST("eventcount"), MixedEvent); // fill the mixed event in the 3 bin
loadCorrection(collision1.bc_as<aod::BCsWithTimestamps>().timestamp());

int multiplicity = tracks1.size();
double multiplicity = tracks1.size();

if (cfgStrictTrackCounter) {
trackCounter(tracks1, multiplicity);
Expand Down
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