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[PWGLF] Correcting the invariant mass calulation of generated Delta particles and adding the mass axis in histograms for generated particles. #17126

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[PWGLF] Correcting the invariant mass calulation of generated Delta particles and adding the mass axis in histograms for generated particles. #17126

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4b741a3
corrected the calculation of mass of generated delta particle
bhattdurgesh921-sys Jul 20, 2026
7b8c7da
COrrected the invariant mass calculation of the generated delta parti…
bhattdurgesh921-sys Jul 20, 2026
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34 changes: 21 additions & 13 deletions PWGLF/Tasks/Resonances/deltaAnalysis.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -319,10 +319,11 @@ struct DeltaAnalysis {
histos.add("THnSparse/hAntiDeltaPlusPlusMC", "THnSparse #bar{#Delta}^{++} MC reconstructed", kTHnSparseF, {massAxis, ptAxis, centAxis, rapAxis});
histos.add("THnSparse/hDeltaZeroMC", "THnSparse #Delta^{0} MC reconstructed", kTHnSparseF, {massAxis, ptAxis, centAxis, rapAxis});
histos.add("THnSparse/hAntiDeltaZeroMC", "THnSparse #bar{#Delta}^{0} MC reconstructed", kTHnSparseF, {massAxis, ptAxis, centAxis, rapAxis});
histos.add("THnSparse/hDeltaPlusPlusGen", "THnSparse #Delta^{++} generated", kTHnSparseF, {ptAxis, centAxis, rapAxis});
histos.add("THnSparse/hAntiDeltaPlusPlusGen", "THnSparse #bar{#Delta}^{++} generated", kTHnSparseF, {ptAxis, centAxis, rapAxis});
histos.add("THnSparse/hDeltaZeroGen", "THnSparse #Delta^{0} generated", kTHnSparseF, {ptAxis, centAxis, rapAxis});
histos.add("THnSparse/hAntiDeltaZeroGen", "THnSparse #bar{#Delta}^{0} generated", kTHnSparseF, {ptAxis, centAxis, rapAxis});
// CHANGED: generated-particle THnSparse now carries mass at axis 0, followed by pt, cent, rap
histos.add("THnSparse/hDeltaPlusPlusGen", "THnSparse #Delta^{++} generated", kTHnSparseF, {massAxis, ptAxis, centAxis, rapAxis});
histos.add("THnSparse/hAntiDeltaPlusPlusGen", "THnSparse #bar{#Delta}^{++} generated", kTHnSparseF, {massAxis, ptAxis, centAxis, rapAxis});
histos.add("THnSparse/hDeltaZeroGen", "THnSparse #Delta^{0} generated", kTHnSparseF, {massAxis, ptAxis, centAxis, rapAxis});
histos.add("THnSparse/hAntiDeltaZeroGen", "THnSparse #bar{#Delta}^{0} generated", kTHnSparseF, {massAxis, ptAxis, centAxis, rapAxis});

histos.add("Analysis/hDeltaPlusPlusInvMassMC", "#Delta^{++} invariant mass (MC truth-matched)", kTH2F, {ptAxis, massAxis});
histos.add("Analysis/hAntiDeltaPlusPlusInvMassMC", "#bar{#Delta}^{++} invariant mass (MC truth-matched)", kTH2F, {ptAxis, massAxis});
Expand Down Expand Up @@ -1250,44 +1251,51 @@ struct DeltaAnalysis {
if (mcParticle.y() < cfgMinY || mcParticle.y() > cfgMaxY)
continue;
const auto daughters = mcParticle.daughters_as<aod::McParticles>();
// CHANGED: daughter loop is now used only for decay-channel validation / QA
// (hasPr, hasPi, ptPr, ptPi). It no longer accumulates daughter energy for
// the mass calculation.
bool hasPr = false, hasPi = false;
float ptPr = -999.f, ptPi = -999.f;
double eTotal = 0.;
for (const auto& d : daughters) {
if (std::abs(d.pdgCode()) == delta_analysis::PdgProton) {
hasPr = true;
ptPr = d.pt();
eTotal += d.e();
} else if (std::abs(d.pdgCode()) == delta_analysis::PdgPion) {
hasPi = true;
ptPi = d.pt();
eTotal += d.e();
}
}
if (!hasPr || !hasPi)
continue;
const float pSq = mcParticle.p() * mcParticle.p();
const float genMass = std::sqrt(std::max(0., eTotal * eTotal - static_cast<double>(pSq)));
// CHANGED: genMass is now computed directly from the mother particle's own four-momentum (E, px, py, pz)
const float eMother = mcParticle.e();
const float pxMother = mcParticle.px();
const float pyMother = mcParticle.py();
const float pzMother = mcParticle.pz();
const float mass2 = eMother * eMother - pxMother * pxMother - pyMother * pyMother - pzMother * pzMother;
const float genMass = std::sqrt(std::max(0.f, mass2));
const float genPt = mcParticle.pt();
const float genY = mcParticle.y();
if (pdg == delta_analysis::PdgDeltaPlusPlus) {
histos.fill(HIST("Analysis/hDeltaPlusPlusInvMassGen"), genPt, genMass);
histos.fill(HIST("THnSparse/hDeltaPlusPlusGen"), genPt, kGenCentrality, genY);
// CHANGED: THnSparse Gen fill now carries genMass as the first argument,
// matching the new {massAxis, ptAxis, centAxis, rapAxis} axis order.
histos.fill(HIST("THnSparse/hDeltaPlusPlusGen"), genMass, genPt, kGenCentrality, genY);
histos.fill(HIST("QAChecks/hGenProtonDeltaPlusPlus"), ptPr);
histos.fill(HIST("QAChecks/hGenPionDeltaPlusPlus"), ptPi);
} else if (pdg == -delta_analysis::PdgDeltaPlusPlus) {
histos.fill(HIST("Analysis/hAntiDeltaPlusPlusInvMassGen"), genPt, genMass);
histos.fill(HIST("THnSparse/hAntiDeltaPlusPlusGen"), genPt, kGenCentrality, genY);
histos.fill(HIST("THnSparse/hAntiDeltaPlusPlusGen"), genMass, genPt, kGenCentrality, genY);
histos.fill(HIST("QAChecks/hGenProtonAntiDeltaPlusPlus"), ptPr);
histos.fill(HIST("QAChecks/hGenPionAntiDeltaPlusPlus"), ptPi);
} else if (pdg == delta_analysis::PdgDeltaZero) {
histos.fill(HIST("Analysis/hDeltaZeroInvMassGen"), genPt, genMass);
histos.fill(HIST("THnSparse/hDeltaZeroGen"), genPt, kGenCentrality, genY);
histos.fill(HIST("THnSparse/hDeltaZeroGen"), genMass, genPt, kGenCentrality, genY);
histos.fill(HIST("QAChecks/hGenProtonDeltaZero"), ptPr);
histos.fill(HIST("QAChecks/hGenPionDeltaZero"), ptPi);
} else if (pdg == -delta_analysis::PdgDeltaZero) {
histos.fill(HIST("Analysis/hAntiDeltaZeroInvMassGen"), genPt, genMass);
histos.fill(HIST("THnSparse/hAntiDeltaZeroGen"), genPt, kGenCentrality, genY);
histos.fill(HIST("THnSparse/hAntiDeltaZeroGen"), genMass, genPt, kGenCentrality, genY);
histos.fill(HIST("QAChecks/hGenProtonAntiDeltaZero"), ptPr);
histos.fill(HIST("QAChecks/hGenPionAntiDeltaZero"), ptPi);
}
Expand Down
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