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PWGHF: Update p-K0S finding in trackIndexSkimCreator (#7599)
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* PWGHF: Update p-K0S finding in trackIndexSkimCreator

* Build the V0 track only if needed

* Please consider the following formatting changes

---------

Co-authored-by: ALICE Action Bot <[email protected]>
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@fgrosa @alibuild
fgrosa and alibuild authored Sep 8, 2024
1 parent 60a7eee commit 933154d
Showing 1 changed file with 37 additions and 54 deletions.
91 changes: 37 additions & 54 deletions PWGHF/TableProducer/trackIndexSkimCreator.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -2971,24 +2971,15 @@ struct HfTrackIndexSkimCreatorCascades {
Configurable<double> minRelChi2Change{"minRelChi2Change", 0.9, "stop iterations if chi2/chi2old > this"};
Configurable<bool> useAbsDCA{"useAbsDCA", true, "Minimise abs. distance rather than chi2"};
Configurable<bool> useWeightedFinalPCA{"useWeightedFinalPCA", true, "Recalculate vertex position using track covariances, effective only if useAbsDCA is true"};
// quality cut
Configurable<bool> doCutQuality{"doCutQuality", true, "apply quality cuts"};
// track cuts for V0 daughters
Configurable<bool> tpcRefitV0Daugh{"tpcRefitV0Daugh", true, "request TPC refit V0 daughters"};
Configurable<int> nCrossedRowsMinV0Daugh{"nCrossedRowsMinV0Daugh", 50, "min crossed rows V0 daughters"};
Configurable<double> etaMinV0Daugh{"etaMinV0Daugh", -99999., "min. pseudorapidity V0 daughters"};
Configurable<double> etaMaxV0Daugh{"etaMaxV0Daugh", 1.1, "max. pseudorapidity V0 daughters"};
Configurable<double> ptMinV0Daugh{"ptMinV0Daugh", 0.05, "min. pT V0 daughters"};
// v0 cuts
Configurable<double> cpaV0Min{"cpaV0Min", .995, "min. cos PA V0"}; // as in the task that create the V0s
Configurable<double> dcaXYNegToPvMin{"dcaXYNegToPvMin", .1, "min. DCA_XY Neg To PV"}; // check: in HF Run 2, it was 0 at filtering
Configurable<double> dcaXYPosToPvMin{"dcaXYPosToPvMin", .1, "min. DCA_XY Pos To PV"}; // check: in HF Run 2, it was 0 at filtering
Configurable<double> cpaV0Min{"cpaV0Min", 0.95, "min. cos PA V0"}; // as in the task that create the V0s
Configurable<double> cutInvMassV0{"cutInvMassV0", 0.05, "V0 candidate invariant mass difference wrt PDG"};
// cascade cuts
Configurable<double> ptCascCandMin{"ptCascCandMin", -1., "min. pT of the cascade candidate"}; // PbPb 2018: use 1
Configurable<double> massPrK0sMin{"massPrK0sMin", 0.f, "Invariant mass lower limit for p K0S decay channel"};
Configurable<double> massPrK0sMax{"massPrK0sMax", 1000.f, "Invariant mass upper limit for p K0S decay channel"};

Configurable<double> cutInvMassCascLc{"cutInvMassCascLc", 1., "Lc candidate invariant mass difference wrt PDG"}; // for PbPb 2018: use 0.2
// Configurable<double> cutCascDCADaughters{"cutCascDCADaughters", .1, "DCA between V0 and bachelor in cascade"};
// proton PID
Expand All @@ -3006,7 +2997,8 @@ struct HfTrackIndexSkimCreatorCascades {
Service<o2::ccdb::BasicCCDBManager> ccdb;
o2::base::MatLayerCylSet* lut;
o2::base::Propagator::MatCorrType noMatCorr = o2::base::Propagator::MatCorrType::USEMatCorrNONE;
int runNumber;
o2::base::Propagator::MatCorrType matCorr = o2::base::Propagator::MatCorrType::USEMatCorrLUT;
int runNumber{0};

double massP{0.};
double massK0s{0.};
Expand Down Expand Up @@ -3052,7 +3044,6 @@ struct HfTrackIndexSkimCreatorCascades {
ccdb->setCaching(true);
ccdb->setLocalObjectValidityChecking();
lut = o2::base::MatLayerCylSet::rectifyPtrFromFile(ccdb->get<o2::base::MatLayerCylSet>(config.ccdbPathLut));
runNumber = 0;

if (config.fillHistograms) {
registry.add("hVtx2ProngX", "2-prong candidates;#it{x}_{sec. vtx.} (cm);entries", {HistType::kTH1D, {{1000, -2., 2.}}});
Expand All @@ -3069,21 +3060,23 @@ struct HfTrackIndexSkimCreatorCascades {
PROCESS_SWITCH(HfTrackIndexSkimCreatorCascades, processNoCascades, "Do not skim HF -> V0 cascades", true);

void processCascades(SelectedCollisions const& collisions,
aod::V0Datas const& v0s,
soa::Join<aod::V0Datas, aod::V0Covs> const& v0s,
FilteredTrackAssocSel const& trackIndices,
aod::TracksWCovDcaExtra const&,
aod::BCsWithTimestamps const&)
{
// set the magnetic field from CCDB
for (const auto& collision : collisions) {
auto bc = collision.bc_as<o2::aod::BCsWithTimestamps>();
initCCDB(bc, runNumber, ccdb, config.isRun2 ? config.ccdbPathGrp : config.ccdbPathGrpMag, lut, config.isRun2);
if (config.useDCAFitter) {
auto bc = collision.bc_as<o2::aod::BCsWithTimestamps>();
initCCDB(bc, runNumber, ccdb, config.isRun2 ? config.ccdbPathGrp : config.ccdbPathGrpMag, lut, config.isRun2);
df2.setBz(o2::base::Propagator::Instance()->getNominalBz());
df2.setMatCorrType(matCorr);
}

const auto thisCollId = collision.globalIndex();
auto groupedBachTrackIndices = trackIndices.sliceBy(trackIndicesPerCollision, thisCollId);
auto groupedV0s = v0s.sliceBy(v0sPerCollision, thisCollId);

// fist we loop over the bachelor candidate
for (const auto& bachIdx : groupedBachTrackIndices) {
Expand All @@ -3097,40 +3090,31 @@ struct HfTrackIndexSkimCreatorCascades {
getPxPyPz(trackBach, pVecBach);
}

auto groupedV0s = v0s.sliceBy(v0sPerCollision, thisCollId);
// now we loop over the V0s
for (const auto& v0 : groupedV0s) {
// selections on the V0 daughters
const auto& trackV0DaughPos = v0.posTrack_as<aod::TracksWCovDcaExtra>();
const auto& trackV0DaughNeg = v0.negTrack_as<aod::TracksWCovDcaExtra>();
const auto& trackV0DaughPos = v0.posTrack_as<aod::TracksWCovDcaExtra>(); // only used for indices and track cuts (TPC clusters, TPC refit)
const auto& trackV0DaughNeg = v0.negTrack_as<aod::TracksWCovDcaExtra>(); // only used for indices and track cuts (TPC clusters, TPC refit)

// check not to take the same track twice (as bachelor and V0 daughter)
if (trackV0DaughPos.globalIndex() == bach.globalIndex() || trackV0DaughNeg.globalIndex() == bach.globalIndex()) {
continue;
}

if (config.tpcRefitV0Daugh) {
if (!(trackV0DaughPos.trackType() & o2::aod::track::TPCrefit) ||
!(trackV0DaughNeg.trackType() & o2::aod::track::TPCrefit)) {
continue;
}
}
if (trackV0DaughPos.tpcNClsCrossedRows() < config.nCrossedRowsMinV0Daugh ||
trackV0DaughNeg.tpcNClsCrossedRows() < config.nCrossedRowsMinV0Daugh) {
continue;
}
//
// if (trackV0DaughPos.dcaXY() < dcaXYPosToPvMin || // to the filters?
// trackV0DaughNeg.dcaXY() < dcaXYNegToPvMin) {
// continue;
// }
//
if (trackV0DaughPos.pt() < config.ptMinV0Daugh || // to the filters? I can't for now, it is not in the tables
trackV0DaughNeg.pt() < config.ptMinV0Daugh) {
std::array<float, 3> pVecPos = {v0.pxpos(), v0.pypos(), v0.pzpos()};
std::array<float, 3> pVecNeg = {v0.pxneg(), v0.pyneg(), v0.pzneg()};

float ptPos = RecoDecay::pt(pVecPos);
float ptNeg = RecoDecay::pt(pVecNeg);
if (ptPos < config.ptMinV0Daugh || // to the filters? I can't for now, it is not in the tables
ptNeg < config.ptMinV0Daugh) {
continue;
}
if ((trackV0DaughPos.eta() > config.etaMaxV0Daugh || trackV0DaughPos.eta() < config.etaMinV0Daugh) || // to the filters? I can't for now, it is not in the tables
(trackV0DaughNeg.eta() > config.etaMaxV0Daugh || trackV0DaughNeg.eta() < config.etaMinV0Daugh)) {

float etaPos = RecoDecay::eta(pVecPos);
float etaNeg = RecoDecay::eta(pVecNeg);
if ((etaPos > config.etaMaxV0Daugh || etaPos < config.etaMinV0Daugh) || // to the filters? I can't for now, it is not in the tables
(etaNeg > config.etaMaxV0Daugh || etaNeg < config.etaMinV0Daugh)) {
continue;
}

Expand All @@ -3144,27 +3128,30 @@ struct HfTrackIndexSkimCreatorCascades {
continue;
}

const std::array<float, 3> momentumV0 = {v0.px(), v0.py(), v0.pz()};
std::array<float, 3> pVecV0 = {v0.px(), v0.py(), v0.pz()};

// invariant-mass cut: we do it here, before updating the momenta of bach and V0 during the fitting to save CPU
// TODO: but one should better check that the value here and after the fitter do not change significantly!!!
double mass2K0sP = RecoDecay::m(std::array{bach.pVector(), momentumV0}, std::array{massP, massK0s});
double mass2K0sP = RecoDecay::m(std::array{pVecBach, pVecV0}, std::array{massP, massK0s});
if ((config.cutInvMassCascLc >= 0.) && (std::abs(mass2K0sP - massLc) > config.cutInvMassCascLc)) {
continue;
}

auto trackParCovV0DaughPos = getTrackParCov(trackV0DaughPos);
trackParCovV0DaughPos.propagateTo(v0.posX(), o2::base::Propagator::Instance()->getNominalBz()); // propagate the track to the X closest to the V0 vertex
auto trackParCovV0DaughNeg = getTrackParCov(trackV0DaughNeg);
trackParCovV0DaughNeg.propagateTo(v0.negX(), o2::base::Propagator::Instance()->getNominalBz()); // propagate the track to the X closest to the V0 vertex
std::array<float, 3> pVecV0 = {v0.px(), v0.py(), v0.pz()};

const std::array<float, 3> vertexV0 = {v0.x(), v0.y(), v0.z()};
// we build the neutral track to then build the cascade
auto trackV0 = o2::dataformats::V0(vertexV0, momentumV0, {0, 0, 0, 0, 0, 0}, trackParCovV0DaughPos, trackParCovV0DaughNeg); // build the V0 track

// now we find the DCA between the V0 and the bachelor, for the cascade
if (config.useDCAFitter) {

const std::array<float, 3> vertexV0 = {v0.x(), v0.y(), v0.z()};
// we build the neutral track to then build the cascade
std::array<float, 21> covV = {0.};
constexpr int MomInd[6] = {9, 13, 14, 18, 19, 20}; // cov matrix elements for momentum component
for (int i = 0; i < 6; i++) {
covV[MomInd[i]] = v0.momentumCovMat()[i];
covV[i] = v0.positionCovMat()[i];
}
auto trackV0 = o2::track::TrackParCov(vertexV0, pVecV0, covV, 0, true);
trackV0.setAbsCharge(0);
trackV0.setPID(o2::track::PID::K0);

int nCand2 = 0;
try {
nCand2 = df2.process(trackV0, trackBach);
Expand All @@ -3189,10 +3176,6 @@ struct HfTrackIndexSkimCreatorCascades {
// invariant mass
// re-calculate invariant masses with updated momenta, to fill the histogram
mass2K0sP = RecoDecay::m(std::array{pVecBach, pVecV0}, std::array{massP, massK0s});
if (mass2K0sP < config.massPrK0sMin || mass2K0sP > config.massPrK0sMax) {
continue;
}

std::array<float, 3> posCasc = {0., 0., 0.};
if (config.useDCAFitter) {
const auto& cascVtx = df2.getPCACandidate();
Expand Down

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