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[ALICE3] Add xi kink reco #14991

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Merged
njacazio merged 4 commits into from
Feb 17, 2026
+147 −32
Merged

[ALICE3] Add xi kink reco #14991

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f3dd7b4
Add xi kink reco
jesgum Feb 16, 2026
b494a3a
Add fitter in reco and do appropriate handling in mcharm finder
jesgum Feb 16, 2026
e8d3795
formatting
jesgum Feb 16, 2026
2583973
fix unused
jesgum Feb 16, 2026
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131 changes: 109 additions & 22 deletions ALICE3/TableProducer/OTF/onTheFlyTracker.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,7 @@ struct OnTheFlyTracker {
struct : ConfigurableGroup {
std::string prefix = "fastTrackerSettings"; // JSON group name
Configurable<int> minSiliconHits{"minSiliconHits", 6, "minimum number of silicon hits to accept track"};
Configurable<int> minSiliconHitsForKinkReco{"minSiliconHitsForKinkReco", 4, "minimum number of silicon hits to accept track"};
Configurable<int> minSiliconHitsIfTPCUsed{"minSiliconHitsIfTPCUsed", 2, "minimum number of silicon hits to accept track in case TPC info is present"};
Configurable<int> minTPCClusters{"minTPCClusters", 70, "minimum number of TPC hits necessary to consider minSiliconHitsIfTPCUsed"};
Configurable<bool> applyZacceptance{"applyZacceptance", false, "apply z limits to detector layers or not"};
Expand All @@ -168,6 +169,7 @@ struct OnTheFlyTracker {
Configurable<bool> findXi{"findXi", false, "if decayXi on, find Xi and fill Tracks table also with Xi"};
Configurable<bool> trackXi{"trackXi", false, "if findXi on, attempt to track Xi"};
Configurable<bool> doXiQA{"doXiQA", false, "QA plots for when treating Xi"};
Configurable<int> doKinkReco{"doKinkReco", 0, "Flag for kink reco setting: 0 - disabled, 1 - complementary, 2 - only"};
} cascadeDecaySettings;

struct : ConfigurableGroup {
Expand Down Expand Up @@ -866,7 +868,10 @@ struct OnTheFlyTracker {
std::vector<int> nHits(kCascProngs); // total
std::vector<int> nSiliconHits(kCascProngs); // silicon type
std::vector<int> nTPCHits(kCascProngs); // TPC type

bool tryKinkReco = false;
if (cascadeDecaySettings.decayXi && mcParticle.pdgCode() == kXiMinus) {
bool reconstructedCascade = false;
if (cascadeDecaySettings.doXiQA) {
getHist(TH1, histPath + "hXiBuilding")->Fill(0.0f);
}
Expand Down Expand Up @@ -914,23 +919,18 @@ struct OnTheFlyTracker {
}
}

if (cascadeDecaySettings.doXiQA && mcParticle.pdgCode() == kXiMinus) {
if (isReco[0] && isReco[1] && isReco[2]) {
getHist(TH1, histPath + "hXiBuilding")->Fill(2.0f);
getHist(TH2, histPath + "hRecoXi")->Fill(xiDecayRadius2D, mcParticle.pt());
}
if (isReco[0])
getHist(TH2, histPath + "hRecoPiFromXi")->Fill(xiDecayRadius2D, cascadeDecayProducts[0].Pt());
if (isReco[1])
getHist(TH2, histPath + "hRecoPiFromLa")->Fill(laDecayRadius2D, cascadeDecayProducts[1].Pt());
if (isReco[2])
getHist(TH2, histPath + "hRecoPrFromLa")->Fill(laDecayRadius2D, cascadeDecayProducts[2].Pt());
if (!isReco[1] || !isReco[2]) {
tryKinkReco = true; // Lambda outside acceptance, set flag for kink reco to be used if mode 1
}

if (isReco[0] && isReco[1] && isReco[2]) {
reconstructedCascade = true;
}

// +-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+
// combine particles into actual Xi candidate
// cascade building starts here
if (cascadeDecaySettings.findXi && mcParticle.pdgCode() == kXiMinus && isReco[0] && isReco[1] && isReco[2]) {
if (cascadeDecaySettings.findXi && isReco[0] && isReco[1] && isReco[2] && cascadeDecaySettings.doKinkReco != 2) {
if (cascadeDecaySettings.doXiQA) {
getHist(TH1, histPath + "hXiBuilding")->Fill(3.0f);
}
Expand Down Expand Up @@ -1111,24 +1111,111 @@ struct OnTheFlyTracker {
thisCascade.cascadeTrackId = lastTrackIndex + tracksAlice3.size(); // this is the next index to be filled -> should be it
tracksAlice3.push_back(TrackAlice3{cascadeTrack, mcParticle.globalIndex(), time, timeResolutionUs, false, false, 1, thisCascade.foundClusters});

if (cascadeDecaySettings.doXiQA) {
getHist(TH1, histPath + "hXiBuilding")->Fill(6.0f);
getHist(TH2, histPath + "h2dDeltaPtVsPt")->Fill(trackParCov.getPt(), cascadeTrack.getPt() - trackParCov.getPt());
getHist(TH2, histPath + "h2dDeltaEtaVsPt")->Fill(trackParCov.getPt(), cascadeTrack.getEta() - trackParCov.getEta());

getHist(TH1, histPath + "hMassLambda")->Fill(thisCascade.mLambda);
getHist(TH1, histPath + "hMassXi")->Fill(thisCascade.mXi);
getHist(TH2, histPath + "hFoundVsFindable")->Fill(thisCascade.findableClusters, thisCascade.foundClusters);
}

// add this cascade to vector (will fill cursor later with collision ID)
cascadesAlice3.push_back(thisCascade);
}
}
} // end cascade building

if (isReco[0] && ((cascadeDecaySettings.doKinkReco == 1 && tryKinkReco) || cascadeDecaySettings.doKinkReco == 2)) { // mode 1 or 2
o2::track::TrackParCov prefectCascadeTrack, trackedCasc;
const o2::track::TrackParCov& trackedBach = xiDaughterTrackParCovsTracked[0];
o2::upgrade::convertMCParticleToO2Track(mcParticle, prefectCascadeTrack, pdgDB);

// back track is already smeared
int nCascHits = fastTracker[icfg]->FastTrack(prefectCascadeTrack, trackedCasc, dNdEta);
reconstructedCascade = (fastTrackerSettings.minSiliconHitsForKinkReco < nCascHits) ? false : true;

if (reconstructedCascade) {
std::array<float, 3> pCasc;
std::array<float, 3> pBach;
std::array<float, 3> pV0;
trackedCasc.getPxPyPzGlo(pCasc);
trackedBach.getPxPyPzGlo(pBach);
for (size_t i = 0; i < pCasc.size(); ++i) {
pV0[i] = pCasc[i] - pBach[i];
}

if (isReco[1] && !isReco[2]) {
thisCascade.negativeId = lastTrackIndex + tracksAlice3.size() - 1;
thisCascade.positiveId = -1;
} else if (!isReco[1] && isReco[2]) {
thisCascade.negativeId = -1;
thisCascade.positiveId = lastTrackIndex + tracksAlice3.size() - 1;
} else if (isReco[1] && isReco[2]) {
thisCascade.positiveId = lastTrackIndex + tracksAlice3.size() - 1;
thisCascade.negativeId = lastTrackIndex + tracksAlice3.size() - 2;
} else {
thisCascade.positiveId = -1;
thisCascade.negativeId = -1;
}

int nCand = 0;
bool kinkFitterOK = true;
try {
nCand = fitter.process(trackedCasc, trackedBach);
} catch (...) {
kinkFitterOK = false;
}

if (nCand == 0) {
kinkFitterOK = false;
}

if (kinkFitterOK) {
if (cascadeDecaySettings.doXiQA) {
getHist(TH1, histPath + "hXiBuilding")->Fill(6.0f);
}
}

std::array<float, 3> kinkVtx = {-999, -999, -999};
kinkVtx = fitter.getPCACandidatePos();

thisCascade.bachelorId = lastTrackIndex + tracksAlice3.size() - isReco.size();
thisCascade.cascadeTrackId = lastTrackIndex + tracksAlice3.size(); // this should be ok
thisCascade.dcaV0dau = -1.f; // unknown
thisCascade.v0radius = -1.f; // unknown
thisCascade.dcacascdau = std::sqrt(fitter.getChi2AtPCACandidate());
thisCascade.cascradius = std::hypot(kinkVtx[0], kinkVtx[1]);
thisCascade.cascradiusMC = xiDecayRadius2D;
thisCascade.mLambda = o2::constants::physics::MassLambda;
thisCascade.findableClusters = nCascHits;
thisCascade.foundClusters = nCascHits;
thisCascade.mXi = RecoDecay::m(std::array{std::array{pBach[0], pBach[1], pBach[2]},
std::array{pV0[0], pV0[1], pV0[2]}},
std::array{o2::constants::physics::MassPionCharged, o2::constants::physics::MassLambda});

tracksAlice3.push_back(TrackAlice3{trackedCasc, mcParticle.globalIndex(), time, timeResolutionUs, false, false, 1, thisCascade.foundClusters});

// add this cascade to vector (will fill cursor later with collision ID)
cascadesAlice3.push_back(thisCascade);
}
} // end cascade kink building

// +-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+-~-+
if (cascadeDecaySettings.doXiQA) {
if (reconstructedCascade) {
getHist(TH2, histPath + "hRecoXi")->Fill(xiDecayRadius2D, mcParticle.pt());
getHist(TH1, histPath + "hMassLambda")->Fill(thisCascade.mLambda);
getHist(TH1, histPath + "hMassXi")->Fill(thisCascade.mXi);
// getHist(TH2, histPath + "h2dDeltaPtVsPt")->Fill(trackParCov.getPt(), cascadeTrack.getPt() - trackParCov.getPt());
// getHist(TH2, histPath + "h2dDeltaEtaVsPt")->Fill(trackParCov.getPt(), cascadeTrack.getEta() - trackParCov.getEta());
getHist(TH2, histPath + "hFoundVsFindable")->Fill(thisCascade.findableClusters, thisCascade.foundClusters);
}
if (isReco[0]) {
getHist(TH2, histPath + "hRecoPiFromXi")->Fill(xiDecayRadius2D, cascadeDecayProducts[0].Pt());
}
if (isReco[1]) {
getHist(TH2, histPath + "hRecoPiFromLa")->Fill(laDecayRadius2D, cascadeDecayProducts[1].Pt());
}
if (isReco[2]) {
getHist(TH2, histPath + "hRecoPrFromLa")->Fill(laDecayRadius2D, cascadeDecayProducts[2].Pt());
}
}

continue; // Cascade handling done, should not be considered anymore
}

// V0 handling
std::vector<o2::track::TrackParCov> v0DaughterTrackParCovsPerfect(2);
std::vector<o2::track::TrackParCov> v0DaughterTrackParCovsTracked(2);
Expand Down
48 changes: 38 additions & 10 deletions ALICE3/TableProducer/alice3MulticharmFinder.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -200,6 +200,13 @@ struct Alice3MulticharmFinder {
int nTPCHitsPiCC;
} thisXiCCcandidate;

struct ProngInfo {
float pt = 1e+10;
float eta = 1e+10;
float dcaXY = 1e+10;
float dcaZ = 1e+10;
};

template <typename TTrackType>
bool buildDecayCandidateTwoBody(TTrackType const& t0, TTrackType const& t1, float mass0, float mass1)
{
Expand Down Expand Up @@ -557,10 +564,6 @@ struct Alice3MulticharmFinder {
}

uint32_t nCombinationsC = 0;
auto bach = xiCand.bachTrack_as<Alice3Tracks>(); // de-reference bach track
auto neg = xiCand.negTrack_as<Alice3Tracks>(); // de-reference neg track
auto pos = xiCand.posTrack_as<Alice3Tracks>(); // de-reference pos track

if (!BIT_CHECK(xi.decayMap(), kTrueXiFromXiC)) {
continue;
}
Expand Down Expand Up @@ -822,13 +825,38 @@ struct Alice3MulticharmFinder {
picc.hasSigPi(), picc.nSigmaPionRich(),
getPdgCodeForTrack(picc));

ProngInfo bachelor, positive, negative;
if (xiCand.has_bachTrack()) {
auto bach = xiCand.bachTrack_as<Alice3Tracks>(); // de-reference bach track
bachelor.pt = bach.pt();
bachelor.eta = bach.eta();
bachelor.dcaXY = bach.dcaXY();
bachelor.dcaZ = bach.dcaZ();
}

if (xiCand.has_negTrack()) {
auto neg = xiCand.negTrack_as<Alice3Tracks>(); // de-reference neg track
negative.pt = neg.pt();
negative.eta = neg.eta();
negative.dcaXY = neg.dcaXY();
negative.dcaZ = neg.dcaZ();
}

if (xiCand.has_posTrack()) {
auto pos = xiCand.posTrack_as<Alice3Tracks>(); // de-reference pos track
positive.pt = pos.pt();
positive.eta = pos.eta();
positive.dcaXY = pos.dcaXY();
positive.dcaZ = pos.dcaZ();
}

multiCharmExtra(
bach.pt(), bach.eta(),
bach.dcaXY(), bach.dcaZ(),
pos.pt(), pos.eta(),
pos.dcaXY(), pos.dcaZ(),
neg.pt(), neg.eta(),
neg.dcaXY(), neg.dcaZ(),
bachelor.pt, bachelor.eta,
bachelor.dcaXY, bachelor.dcaZ,
positive.pt, positive.eta,
positive.dcaXY, positive.dcaZ,
negative.pt, negative.eta,
negative.dcaXY, negative.dcaZ,
pi1c.eta(), pi2c.eta(), picc.eta());
}
}
Expand Down
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