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[ALICE3] Add causality checks for secondary tracks in cascade finding #17156

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jesgum merged 2 commits into from
Jul 21, 2026
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Merged

[ALICE3] Add causality checks for secondary tracks in cascade finding #17156

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5b1d6c0
Add causality checks for secondary tracks in cascade finding
jesgum Jul 21, 2026
3b1077f
remove unused
jesgum Jul 21, 2026
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88 changes: 75 additions & 13 deletions ALICE3/TableProducer/alice3strangenessFinder.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@

#include "PWGLF/DataModel/LFStrangenessTables.h"

#include "ALICE3/Core/GeometryContainer.h"
#include "ALICE3/Core/TrackUtilities.h"
#include "ALICE3/DataModel/OTFPIDTrk.h"
#include "ALICE3/DataModel/OTFRICH.h"
Expand All @@ -31,6 +32,7 @@
#include "Common/Core/trackUtilities.h"
#include "Common/DataModel/TrackSelectionTables.h"

#include <CCDB/BasicCCDBManager.h>
#include <CommonConstants/PhysicsConstants.h>
#include <DCAFitter/DCAFitterN.h>
#include <DetectorsBase/Propagator.h>
Expand All @@ -48,7 +50,7 @@
#include <ReconstructionDataFormats/TrackParametrization.h>

#include <TH1.h>
#include <TLorentzVector.h>

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[root/lorentz-vector] 

Do not use the TLorentzVector legacy class. Use std::array with RecoDecay methods or the ROOT::Math::LorentzVector template instead.
#include <TPDGCode.h>

#include <sys/types.h>
Expand All @@ -60,7 +62,6 @@
#include <vector>

using namespace o2;
// using namespace o2::analysis;
using namespace o2::framework;
using namespace o2::constants::physics;

Expand All @@ -73,6 +74,9 @@
SliceCache cache;

HistogramRegistry histos{"histos", {}, OutputObjHandlingPolicy::AnalysisObject};
Service<o2::ccdb::BasicCCDBManager> ccdb{};
o2::fastsim::GeometryContainer geoContainer;
std::vector<std::vector<float>> trackingLayers;

Produces<aod::V0CandidateIndices> v0CandidateIndices; // contains V0 candidate indices
Produces<aod::V0CandidateCores> v0CandidateCores; // contains V0 candidate core information
Expand Down Expand Up @@ -145,8 +149,9 @@
Configurable<bool> useOriginalTrackParams{"useOriginalTrackParams", false, "use original track parameters instead of the ones propagated to PCA (effective only if skipFitter is false) and for MC truth info"};

o2::vertexing::DCAFitterN<2> fitter;
Service<o2::framework::O2DatabasePDG> pdgDB;
Service<o2::framework::O2DatabasePDG> pdgDB{};
static constexpr float ToMicrons = 1e+4;
static constexpr int LutConfig = 0; // todo

// partitions for v0/casc dau tracks
Partition<Alice3TracksACTS> positiveSecondaryTracksACTS =
Expand Down Expand Up @@ -194,7 +199,7 @@
float dcaToPV{};
};

void init(InitContext&)
void init(InitContext& initContext)
{
// Initialization code here
fitter.setBz(magneticField);
Expand Down Expand Up @@ -275,6 +280,30 @@
histos.add("Generated/hGeneratedAntiOmega", "hGeneratedAntiOmega", kTH2D, {{axisPt}, {axisEta}});
}

if (doprocessFindV0CandidateOTF) {
ccdb->setURL("http://alice-ccdb.cern.ch");
ccdb->setTimestamp(-1);
geoContainer.setCcdbManager(ccdb.operator->());
geoContainer.init(initContext);
const int nGeometries = geoContainer.getNumberOfConfigurations();
trackingLayers.resize(nGeometries);

for (int icfg = 0; icfg < nGeometries; ++icfg) {
auto globalConfiguration = geoContainer.getConfigurations(icfg);

for (const auto& [outerKey, innerMap] : globalConfiguration) {
if (outerKey.empty() || outerKey[0] != 'B') {
continue;
}

auto it = innerMap.find("r");
if (it != innerMap.end()) {
trackingLayers[icfg].push_back(std::stof(it->second));
}
}
}
}

if (buildCascade) {
histos.add("CascadeBuilding/hDcaBetweenDaus", "hDcaBetweenDaus", kTH1D, {{axisDCA}});
histos.add("CascadeBuilding/hXiMass", "", kTH1D, {axisXiMass});
Expand Down Expand Up @@ -333,6 +362,20 @@
} // end association check
return returnValue;
}

template <typename TTrackType>
[[nodiscard]] float getFirstLayerHitRadius(const TTrackType& track, const std::vector<float>& layers)
{
const float trueRadius = std::hypot(track.x(), track.y());
for (const float layerRadius : layers) {

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[const-ref-in-for-loop] 

Use constant references for non-modified iterators in range-based for loops.
if (layerRadius >= trueRadius) {
return layerRadius;
}
}
static constexpr float OutsideALICE3 = 100.f;
return OutsideALICE3;
}

template <typename TTrackType>
bool buildDecayCandidateTwoBody(TTrackType const& t0, TTrackType const& t1, std::array<float, 3> vtx, Candidate& thisCandidate)
{
Expand Down Expand Up @@ -373,8 +416,8 @@
t0.getPxPyPzGlo(thisCandidate.pDau0);
t1.getPxPyPzGlo(thisCandidate.pDau1);
}
histos.fill(HIST("hPtNegDauAfterV0Finding"), std::sqrt(thisCandidate.pDau1[0] * thisCandidate.pDau1[0] + thisCandidate.pDau1[1] + thisCandidate.pDau1[1]), t1.getPt());
histos.fill(HIST("hPtPosDauAfterV0Finding"), std::sqrt(thisCandidate.pDau0[0] * thisCandidate.pDau0[0] + thisCandidate.pDau0[1] + thisCandidate.pDau0[1]), t0.getPt());
histos.fill(HIST("hPtNegDauAfterV0Finding"), std::hypot(thisCandidate.pDau1[0], thisCandidate.pDau1[1]), t1.getPt());
histos.fill(HIST("hPtPosDauAfterV0Finding"), std::hypot(thisCandidate.pDau0[0], thisCandidate.pDau0[1]), t0.getPt());

thisCandidate.dcaDau = std::sqrt(fitter.getChi2AtPCACandidate());
thisCandidate.p[0] = thisCandidate.pDau0[0] + thisCandidate.pDau1[0];
Expand Down Expand Up @@ -416,8 +459,6 @@
thisCandidate.dcaToPV = calculateDCAStraightToPV(thisCandidate.posSV[0], thisCandidate.posSV[1], thisCandidate.posSV[2],
thisCandidate.p[0], thisCandidate.p[1], thisCandidate.p[2],
vtx[0], vtx[1], vtx[2]);

return true;
} else {
t0.getPxPyPzGlo(thisCandidate.pDau0);
t1.getPxPyPzGlo(thisCandidate.pDau1);
Expand All @@ -434,8 +475,8 @@
thisCandidate.dcaToPV = calculateDCAStraightToPV(thisCandidate.posSV[0], thisCandidate.posSV[1], thisCandidate.posSV[2],
thisCandidate.p[0], thisCandidate.p[1], thisCandidate.p[2],
vtx[0], vtx[1], vtx[2]);
return true;
}
return true;
}

void processGenerated(aod::McParticles const&)
Expand Down Expand Up @@ -603,8 +644,26 @@
continue; // candidate outside of acceptance
}

if (std::hypot(v0Cand.posSV[0], v0Cand.posSV[1]) < std::hypot(cascCand.posSV[0], cascCand.posSV[1])) {
continue; // causality
const float radiusV0 = std::hypot(v0Cand.posSV[0], v0Cand.posSV[1]);
const float radiusCasc = std::hypot(cascCand.posSV[0], cascCand.posSV[1]);
const float posCausalityRadius = getFirstLayerHitRadius(posTrack, trackingLayers[LutConfig]);
const float negCausalityRadius = getFirstLayerHitRadius(negTrack, trackingLayers[LutConfig]);
const float bachCausalityRadius = getFirstLayerHitRadius(bachTrack, trackingLayers[LutConfig]);

if (posCausalityRadius < radiusV0) {
continue; // positive track hit a layer before v0 decayed
}

if (negCausalityRadius < radiusV0) {
continue; // negative track hit a layer before v0 decayed
}

if (radiusV0 < radiusCasc) {
continue; // v0 decayed before cascade
}

if (bachCausalityRadius < radiusCasc) {
continue; // bachelor track hit a layer before v0 decayed
}

const float massXi = RecoDecay::m(std::array{std::array{cascCand.pDau0[0], cascCand.pDau0[1], cascCand.pDau0[2]},
Expand Down Expand Up @@ -685,23 +744,26 @@
isLambda = (posParticle.pdgCode() == kProton && negParticle.pdgCode() == kPiMinus);
isAntiLambda = (posParticle.pdgCode() == kPiPlus && negParticle.pdgCode() == kProtonBar);
if (isK0s || isLambda || isAntiLambda) {
if (!isK0s && isK0Gun)
if (!isK0s && isK0Gun) {
continue;
if (!isLambda && isLambdaGun)
}
if (!isLambda && isLambdaGun) {
continue;
}
Candidate v0cand;
std::vector<double> v0DecayVertex;
v0DecayVertex.push_back(negParticle.vx());
v0DecayVertex.push_back(negParticle.vy());
v0DecayVertex.push_back(negParticle.vz());
TLorentzVector posLorVector = {posParticle.px(), posParticle.py(), posParticle.pz(), posParticle.e()};

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[root/lorentz-vector] 

Do not use the TLorentzVector legacy class. Use std::array with RecoDecay methods or the ROOT::Math::LorentzVector template instead.
TLorentzVector negLorVector = {negParticle.px(), negParticle.py(), negParticle.pz(), negParticle.e()};

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[root/lorentz-vector] 

Do not use the TLorentzVector legacy class. Use std::array with RecoDecay methods or the ROOT::Math::LorentzVector template instead.
o2::track::TrackParCov posParCov;
o2::track::TrackParCov negParCov;
o2::upgrade::convertTLorentzVectorToO2Track(1, posLorVector, v0DecayVertex, posParCov);

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[root/lorentz-vector] 

Do not use the TLorentzVector legacy class. Use std::array with RecoDecay methods or the ROOT::Math::LorentzVector template instead.
o2::upgrade::convertTLorentzVectorToO2Track(-1, negLorVector, v0DecayVertex, negParCov);

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[root/lorentz-vector] 

Do not use the TLorentzVector legacy class. Use std::array with RecoDecay methods or the ROOT::Math::LorentzVector template instead.
if (!buildDecayCandidateTwoBody(posParCov, negParCov, vtx, v0cand))
if (!buildDecayCandidateTwoBody(posParCov, negParCov, vtx, v0cand)) {
continue;
}
v0CandidateIndices(collision.globalIndex(),
posParticle.globalIndex(),
negParticle.globalIndex(),
Expand Down
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