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[PWGCF] Update in PID strategy and QA #16834

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wenyaCern merged 1 commit into from
Jun 26, 2026
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[PWGCF] Update in PID strategy and QA #16834

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139 changes: 43 additions & 96 deletions PWGCF/TwoParticleCorrelations/Tasks/nucleibalance.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -1711,6 +1711,7 @@ struct Lambdastarproxy {
Configurable<float> lstarCutNsigmaTPCDe{"lstarCutNsigmaTPCDe", float{NsigmaTPCDefault}, "|nSigma^{TPC}_{d}| cut"};
Configurable<float> lstarCutNsigmaTOFDe{"lstarCutNsigmaTOFDe", float{NsigmaTOFDefault}, "|nSigma^{TOF}_{d}| cut"};
Configurable<int> lstarEnableTOFNsigmaCutDe{"lstarEnableTOFNsigmaCutDe", 0, "Enable deuteron-only TOF nSigma cut in PID strategy 2"};
Configurable<int> lstarProxyUseProtonPIDAsDeuteron{"lstarProxyUseProtonPIDAsDeuteron", 0, "Closure/control test: keep proxy candidates that pass the normal deuteron selection and are also proton-like, then build p_proxy = p_track/2"};
// Optional deuteron-only TOF auxiliary selections.
// Defaults are OFF, so strategy 2 remains TPC nSigma only for deuterons.
Configurable<int> lstarEnableBetaCutDe{"lstarEnableBetaCutDe", 0, "Enable deuteron-only TOF beta cut using beta() > lstarBetaCutDe"};
Expand Down Expand Up @@ -1763,6 +1764,9 @@ struct Lambdastarproxy {
Configurable<int> lstarNoMixedEvents{"lstarNoMixedEvents", int{NoMixedEventsDefault}, "Number of previous events kept for mixed-event background"};
Configurable<float> lstarMixZvtxMax{"lstarMixZvtxMax", float{MixZvtxMaxDefault}, "Max |Δzvtx| (cm) for event mixing"};
Configurable<float> lstarMixMultMax{"lstarMixMultMax", float{MixMultMaxDefault}, "Max |Δmult| for event mixing"};
// Master switch for PID QA histogram filling.
// Inclusive PID-QA histograms are filled before final PID cuts, after event/track-quality cuts.
// Candidate-level nSigma/TOF/DCA histograms are filled after final PID cuts.
Configurable<int> lstarEnablePidQA{"lstarEnablePidQA", 0, "Enable PID QA histograms (dE/dx, TOF #beta, proxy invariant-mass QA, etc.): 1 = ON, 0 = OFF"};
Configurable<int> lstarEnableSparse{"lstarEnableSparse", 1, "Enable THnSparse invariant-mass histograms (#Lambda^{*} pK and proxy); 1 = ON, 0 = OFF"};
Configurable<float> lstarLambdaAbsYMax{"lstarLambdaAbsYMax", 0.5f, "Max |y_{pK}| (or y_{proxy K}) for #Lambda^{*} candidates"};
Expand Down Expand Up @@ -2104,6 +2108,7 @@ struct Lambdastarproxy {
"#Lambda^{*} proxy invariant mass from (d/2 + K);M_{p_{proxy}K} (GeV/c^{2});Counts",
HistType::kTH1F, {massAxis});

// Inclusive PID QA before final candidate PID cuts: after track-quality cuts only
// TPC dE/dx vs total momentum
histos.add("hTPCdEdxVsP",
"TPC dE/dx vs p;p (GeV/c);dE/dx (arb. units);Counts",
Expand All @@ -2114,7 +2119,8 @@ struct Lambdastarproxy {
"TOF #beta vs p;p (GeV/c);#beta_{TOF};Counts",
HistType::kTH2F, {pAxis, betaAxis});

// --- Per-species PID QA (tagged) ---
// --- Per-species inclusive PID QA before final candidate PID cuts ---
// Species tagging here uses classifyPidSpecies() and is meant only for QA.
histos.add("hTPCdEdxVsP_Pi",
"TPC dE/dx vs p (tagged #pi);p (GeV/c);dE/dx (arb. units);Counts",
HistType::kTH2F, {pAxis, dEdxAxis});
Expand Down Expand Up @@ -2204,7 +2210,7 @@ struct Lambdastarproxy {
"TOF n#sigma_{K} vs p; p (GeV/c); n#sigma^{TOF}_{K};Counts",
HistType::kTH2F, {pAxis, nsAxis});

// --- Additional pT-based PID QA for the final selected K/p/d candidates ---
// --- Candidate PID QA after final selected K/p/d PID cuts ---
// These histograms are needed for PID studies in the same pT intervals used by the analysis.
histos.add("hTOFBetaVsPt_K",
"TOF #beta vs p_{T} for selected K;p_{T} (GeV/c);#beta_{TOF};Counts",
Expand Down Expand Up @@ -2451,16 +2457,15 @@ struct Lambdastarproxy {
}

if (lstarPidStrategy.value == PidStrategyNucleiDeuteronTPC) {
// For deuterons, follow the default idea of the official nuclei task:
// use TPC nσ as the main hard PID selection.
// For deuterons, use TPC nσ as the main hard PID selection.
// If the optional deuteron TOF nσ cut is enabled, apply it only when
// the track has a valid TOF match. Tracks without TOF are kept with
// the TPC-only decision, avoiding an additional TOF-matching efficiency loss.
if (isDeuteron) {
if (std::abs(nsTPC) >= tpcCut) {
return false;
}
if (lstarEnableTOFNsigmaCutDe.value != 0) {
if (!hasTof) {
return false;
}
if (lstarEnableTOFNsigmaCutDe.value != 0 && hasTof) {
return std::abs(nsTOF) < tofCut;
}
return true;
Expand Down Expand Up @@ -2580,87 +2585,6 @@ struct Lambdastarproxy {
constexpr double MassProton = o2::constants::physics::MassProton;
constexpr double MassKaonCharged = o2::constants::physics::MassKaonCharged;

// --- Inclusive PID QA: keep #pi/K/p/d bands in TPC dE/dx and TOF beta plots ---
if (lstarEnablePidQA.value != 0) {
for (auto const& trk : tracks) {
if (trk.pt() < lstarCutPtMin.value || std::abs(trk.eta()) > lstarCutEtaMax.value) {
continue;
}
if (!passTrackQuality(trk)) {
continue;
}
if (trk.sign() == 0) {
continue;
}
// Inclusive PID QA
fillTPCdEdxVsPIfAvailable(trk);
fillTOFBetaVsPIfAvailable(trk);

// Per-species PID-QA (tagged) histograms
const int sp = classifyPidSpecies(trk);
switch (sp) {
case 0: { // pion
if constexpr (requires { trk.tpcSignal(); }) {
histos.fill(HIST("hTPCdEdxVsP_Pi"), trk.p(), trk.tpcSignal());
}
if constexpr (requires { trk.beta(); }) {
const bool hasTof = hasTOFMatch(trk);
const float beta = trk.beta();
if (hasTof && beta > TofBetaMin && beta < TofBetaMax) {
histos.fill(HIST("hTOFBetaVsP_Pi"), trk.p(), beta);
}
}
break;
}

case 1: { // kaon
if constexpr (requires { trk.tpcSignal(); }) {
histos.fill(HIST("hTPCdEdxVsP_K"), trk.p(), trk.tpcSignal());
}
if constexpr (requires { trk.beta(); }) {
const bool hasTof = hasTOFMatch(trk);
const float beta = trk.beta();
if (hasTof && beta > TofBetaMin && beta < TofBetaMax) {
histos.fill(HIST("hTOFBetaVsP_K"), trk.p(), beta);
}
}
break;
}

case 2: { // proton
if constexpr (requires { trk.tpcSignal(); }) {
histos.fill(HIST("hTPCdEdxVsP_P"), trk.p(), trk.tpcSignal());
}
if constexpr (requires { trk.beta(); }) {
const bool hasTof = hasTOFMatch(trk);
const float beta = trk.beta();
if (hasTof && beta > TofBetaMin && beta < TofBetaMax) {
histos.fill(HIST("hTOFBetaVsP_P"), trk.p(), beta);
}
}
break;
}

case 3: { // deuteron
if constexpr (requires { trk.tpcSignal(); }) {
histos.fill(HIST("hTPCdEdxVsP_D"), trk.p(), trk.tpcSignal());
}
if constexpr (requires { trk.beta(); }) {
const bool hasTof = hasTOFMatch(trk);
const float beta = trk.beta();
if (hasTof && beta > TofBetaMin && beta < TofBetaMax) {
histos.fill(HIST("hTOFBetaVsP_D"), trk.p(), beta);
}
}
break;
}

default:
break;
}
}
}

std::vector<KaonCand> kaonCands;
std::vector<ProxyCand> proxyCands;
std::vector<ProtonCand> protonCands;
Expand All @@ -2670,7 +2594,9 @@ struct Lambdastarproxy {

float eventMultFallback = 0.f; // fallback mixing variable: number of selected charged tracks (after quality cuts)

// Inclusive PID QA loop: count all selected charged tracks for fallback multiplicity
// Inclusive track loop before final candidate PID cuts.
// It counts selected charged tracks for fallback multiplicity and when enabled,
// fills inclusive PID QA after track-quality cuts but before final K/p/d PID cuts.
for (auto const& trk : tracks) {
if (trk.pt() < lstarCutPtMin.value || std::abs(trk.eta()) > lstarCutEtaMax.value) {
continue;
Expand Down Expand Up @@ -2769,23 +2695,44 @@ struct Lambdastarproxy {
const float etaD = trkD.eta();
const float phiD = trkD.phi();

// PID for deuteron candidates
// PID for proxy candidates.
// Normal mode: use the standard deuteron PID and build p_proxy = p_d / 2.
// Closure/control mode: select the subset of standard deuteron-proxy candidates
// that are also proton-like. This tests proton contamination inside the deuteron
// selection, not all proton candidates.
const bool useProtonAsProxy = (lstarProxyUseProtonPIDAsDeuteron.value != 0);

const float nsTPCDe = trkD.tpcNSigmaDe();
const float nsTOFDe = trkD.tofNSigmaDe();
const bool hasTofDe = hasTOFMatch(trkD);

if (!passOptionalDeuteronTOFExtras(trkD)) {
continue;
}
const bool isDeuteron = passFinalCandidatePID(trkD.pt(), trkD.tpcNSigmaDe(), nsTOFDe, hasTofDe,
lstarCutNsigmaTPCDe.value, lstarCutNsigmaTOFDe.value,
lstarPidCircularCutDe.value, lstarPidPtRefDe.value, true);
if (!isDeuteron) {

const bool passesDeuteronSelection = passFinalCandidatePID(ptD, nsTPCDe, nsTOFDe, hasTofDe,
lstarCutNsigmaTPCDe.value, lstarCutNsigmaTOFDe.value,
lstarPidCircularCutDe.value, lstarPidPtRefDe.value,
true);
if (!passesDeuteronSelection) {
continue;
}

if (useProtonAsProxy) {
const float nsTPCPrAsProxy = trkD.tpcNSigmaPr();
const float nsTOFPrAsProxy = trkD.tofNSigmaPr();
const bool passesProtonSelection = passFinalCandidatePID(ptD, nsTPCPrAsProxy, nsTOFPrAsProxy, hasTofDe,
lstarCutNsigmaTPCPr.value, lstarCutNsigmaTOFPr.value,
lstarPidCircularCutPr.value, lstarPidPtRefPr.value,
false);
if (!passesProtonSelection) {
continue;
}
}

const double pD = static_cast<double>(ptD) * std::cosh(static_cast<double>(etaD));

// QA histos for deuteron PID and kinematics
// Candidate QA after final deuteron PID cut
if (lstarEnablePidQA.value != 0) {
histos.fill(HIST("hDeuteronProxyPt"), ptD);
histos.fill(HIST("hDeuteronProxyEta"), etaD);
Expand Down
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