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[PWGEM/PhotonMeson] Include check for gamma gamma contamination in Dalitz decays #16338

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jokonig merged 1 commit into from
May 22, 2026
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[PWGEM/PhotonMeson] Include check for gamma gamma contamination in Dalitz decays #16338

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33 changes: 31 additions & 2 deletions PWGEM/PhotonMeson/Core/Pi0EtaToGammaGammaMC.h
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,7 @@
#include <Math/Vector4Dfwd.h>
#include <TF1.h>
#include <TH2.h>
#include <TPDGCode.h>
#include <TString.h>

#include <cmath>
Expand All @@ -74,17 +75,17 @@

template <o2::aod::pwgem::photonmeson::photonpair::PairType pairtype, o2::soa::is_table... Types>
struct Pi0EtaToGammaGammaMC {
o2::framework::Configurable<std::string> ccdburl{"ccdb-url", "http://alice-ccdb.cern.ch", "url of the ccdb repository"};

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[name/configurable] 

Use lowerCamelCase for names of configurables and use the same name for the struct member as for the JSON string. (Declare the type and names on the same line.)
o2::framework::Configurable<std::string> grpPath{"grpPath", "GLO/GRP/GRP", "Path of the grp file"};
o2::framework::Configurable<std::string> grpmagPath{"grpmagPath", "GLO/Config/GRPMagField", "CCDB path of the GRPMagField object"};
o2::framework::Configurable<bool> skipGRPOquery{"skipGRPOquery", true, "skip grpo query"};
o2::framework::Configurable<float> d_bz_input{"d_bz_input", -999, "bz field in kG, -999 is automatic"};

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[name/configurable] 

Use lowerCamelCase for names of configurables and use the same name for the struct member as for the JSON string. (Declare the type and names on the same line.)

o2::framework::Configurable<int> cfgQvecEstimator{"cfgQvecEstimator", 0, "FT0M:0, FT0A:1, FT0C:2"};
o2::framework::Configurable<int> cfgCentEstimator{"cfgCentEstimator", 2, "FT0M:0, FT0A:1, FT0C:2"};
o2::framework::Configurable<float> cfgCentMin{"cfgCentMin", -1, "min. centrality"};
o2::framework::Configurable<float> cfgCentMax{"cfgCentMax", 999, "max. centrality"};
o2::framework::Configurable<float> maxY_rec{"maxY_rec", 0.9, "maximum rapidity for reconstructed particles"};

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[name/configurable] 

Use lowerCamelCase for names of configurables and use the same name for the struct member as for the JSON string. (Declare the type and names on the same line.)
o2::framework::Configurable<std::string> fd_k0s_to_pi0{"fd_k0s_pi0", "1.0", "feed down correction to pi0"};
o2::framework::Configurable<bool> cfgRequireTrueAssociation{"cfgRequireTrueAssociation", false, "flag to require true mc collision association"};

Expand All @@ -92,6 +93,7 @@
o2::framework::Configurable<float> cfgAlphaMeson{"cfgAlphaMeson", 0.65, "photon energy asymmetry distribution parameter for specific value cut"};
o2::framework::Configurable<float> cfgAlphaMesonA{"cfgAlphaMesonA", 0.65, "photon energy asymmetry distribution parameter A for pT dependent cut (A * tanh(B*pT))"};
o2::framework::Configurable<float> cfgAlphaMesonB{"cfgAlphaMesonB", 1.2, "photon energy asymmetry distribution parameter B for pT dependent cut (A * tanh(B*pT))"};
o2::framework::Configurable<bool> cfgGGContaCheck{"cfgGGContaCheck", false, "check gamma gamma contamination of dalitz"};

EMPhotonEventCut fEMEventCut;
struct : o2::framework::ConfigurableGroup {
Expand Down Expand Up @@ -252,6 +254,12 @@
f1fd_k0s_to_pi0 = new TF1("f1fd_k0s_to_pi0", TString(fd_k0s_to_pi0), 0.f, 100.f);

fRegistry.add("Event/hNrecPerMCCollision", "Nrec per mc collision;N_{rec} collisions per MC collision", o2::framework::HistType::kTH1F, {{21, -0.5f, 20.5f}}, false);
if (cfgGGContaCheck) {
fRegistry.add("Event/hNGGContamEta", "Number of Eta from etaToGammaGamma; p_{T, #eta} (GeV/#it{c}); N", o2::framework::HistType::kTH1F, {{40, -0.5f, 20.5f}}, false);
fRegistry.add("Event/hNGGContamPion", "Number of Pion from etaToGammaGamma; p_{T, #pi} (GeV/#it{c}); N", o2::framework::HistType::kTH1F, {{40, -0.5f, 20.5f}}, false);
}
fRegistry.add("Event/hNDalitzEtaPt", "Number of DalitzEta; p_{T, #eta} (GeV/#it{c}); N", o2::framework::HistType::kTH1F, {{40, -0.5f, 20.5f}}, false);
fRegistry.add("Event/hNDalitzPionPt", "Number of DalitzPion; p_{T, #pi} (GeV/#it{c}) ; N", o2::framework::HistType::kTH1F, {{40, -0.5f, 20.5f}}, false);

mRunNumber = 0;
d_bz = 0;
Expand All @@ -270,10 +278,10 @@
}

// In case override, don't proceed, please - no CCDB access required
if (d_bz_input > -990) {

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[magic-number] 

Avoid magic numbers in expressions. Assign the value to a clearly named variable or constant.
d_bz = d_bz_input;
o2::parameters::GRPMagField grpmag;
if (std::fabs(d_bz) > 1e-5) {

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[magic-number] 

Avoid magic numbers in expressions. Assign the value to a clearly named variable or constant.
grpmag.setL3Current(30000.f / (d_bz / 5.0f));
}
mRunNumber = collision.runNumber();
Expand Down Expand Up @@ -572,7 +580,7 @@
TMCCollisions const& mccollisions, TMCParticles const& mcparticles,
TLegs const& /*legs*/ = nullptr, TMatchedTracks const& matchedTracks = nullptr, TMatchedSecondaries const& matchedSecondaries = nullptr)
{
for (auto& collision : collisions) {

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[const-ref-in-for-loop] 

Use constant references for non-modified iterators in range-based for loops.
initCCDB(collision);
if ((pairtype == o2::aod::pwgem::photonmeson::photonpair::PairType::kPHOSPHOS || pairtype == o2::aod::pwgem::photonmeson::photonpair::PairType::kPCMPHOS) && !collision.alias_bit(triggerAliases::kTVXinPHOS)) {
continue;
Expand All @@ -583,7 +591,7 @@
weight = collision.weight();
}

if (eventcuts.onlyKeepWeightedEvents && std::fabs(weight - 1.0) < 1e-10) {

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[magic-number] 

Avoid magic numbers in expressions. Assign the value to a clearly named variable or constant.
continue;
}

Expand Down Expand Up @@ -720,9 +728,9 @@
}

if (g1mc.globalIndex() == g2mc.globalIndex()) {
if (o2::aod::pwgem::dilepton::utils::mcutil::getMotherPDGCode(g1mc, mcparticles) == 111)
if (o2::aod::pwgem::dilepton::utils::mcutil::getMotherPDGCode(g1mc, mcparticles) == PDG_t::kPi0)
fRegistry.fill(HIST("Pair/Pi0/hs_FromSameGamma"), v12.M(), v12.Pt(), wpair);
else if (o2::aod::pwgem::dilepton::utils::mcutil::getMotherPDGCode(g1mc, mcparticles) == 221)
else if (o2::aod::pwgem::dilepton::utils::mcutil::getMotherPDGCode(g1mc, mcparticles) == o2::constants::physics::Pdg::kEta)
fRegistry.fill(HIST("Pair/Eta/hs_FromSameGamma"), v12.M(), v12.Pt(), wpair);
continue;
}
Expand Down Expand Up @@ -792,6 +800,25 @@

auto pos2mc = mcparticles.iteratorAt(pos2.emmcparticleId());
auto ele2mc = mcparticles.iteratorAt(ele2.emmcparticleId());
if (cfgGGContaCheck) {
photonid2 = o2::aod::pwgem::dilepton::utils::mcutil::FindCommonMotherFrom2Prongs(pos2mc, ele2mc, -11, 11, 22, mcparticles); // check possible contamination
if (photonid2 > 0) {
auto photon2 = mcparticles.iteratorAt(photonid2);
int photon2pdg = photon2.pdgCode();
int photon2mothid = photon2.mothersIds()[0];
auto photon2moth = mcparticles.iteratorAt(photon2mothid);
if (photon2pdg == PDG_t::kGamma && (o2::aod::pwgem::photonmeson::utils::mcutil::isGammaGammaDecay(photon2moth, mcparticles))) {
int mothID = o2::aod::pwgem::dilepton::utils::mcutil::getMotherPDGCode(photon2, mcparticles);
if (mothID == o2::constants::physics::Pdg::kEta) {
fRegistry.fill(HIST("Event/hNGGContamEta"), photon2moth.pt());
}
if (mothID == PDG_t::kPi0) {
fRegistry.fill(HIST("Event/hNGGContamPion"), photon2moth.pt());
}
}
}
}

pi0id = o2::aod::pwgem::dilepton::utils::mcutil::FindCommonMotherFrom3Prongs(g1mc, pos2mc, ele2mc, 22, -11, 11, 111, mcparticles);
etaid = o2::aod::pwgem::dilepton::utils::mcutil::FindCommonMotherFrom3Prongs(g1mc, pos2mc, ele2mc, 22, -11, 11, 221, mcparticles);
if (pi0id < 0 && etaid < 0) {
Expand All @@ -805,12 +832,14 @@
}
if (pi0id > 0) {
auto pi0mc = mcparticles.iteratorAt(pi0id);
fRegistry.fill(HIST("Event/hNDalitzPionPt"), pi0mc.pt());
if (cfgRequireTrueAssociation && (pi0mc.emmceventId() != collision.emmceventId())) {
continue;
}
o2::aod::pwgem::photonmeson::utils::nmhistogram::fillTruePairInfo(&fRegistry, veeg, pi0mc, mcparticles, mccollisions, f1fd_k0s_to_pi0, weight);
} else if (etaid > 0) {
auto etamc = mcparticles.iteratorAt(etaid);
fRegistry.fill(HIST("Event/hNDalitzEtaPt"), etamc.pt());
if (cfgRequireTrueAssociation && (etamc.emmceventId() != collision.emmceventId())) {
continue;
}
Expand Down Expand Up @@ -900,13 +929,13 @@
// loop over mc stack and fill histograms for pure MC truth signals
// all MC tracks which belong to the MC event corresponding to the current reconstructed event

for (auto& mccollision : mccollisions) {

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[const-ref-in-for-loop] 

Use constant references for non-modified iterators in range-based for loops.
auto collision_per_mccoll = collisions.sliceBy(rec_perMcCollision, mccollision.globalIndex());
int nrec_per_mc = collision_per_mccoll.size();
fRegistry.fill(HIST("Event/hNrecPerMCCollision"), nrec_per_mc);
}

for (auto& collision : collisions) {

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[const-ref-in-for-loop] 

Use constant references for non-modified iterators in range-based for loops.
if ((pairtype == o2::aod::pwgem::photonmeson::photonpair::kPHOSPHOS || pairtype == o2::aod::pwgem::photonmeson::photonpair::kPCMPHOS) && !collision.alias_bit(triggerAliases::kTVXinPHOS)) {
continue; // I don't know why this is necessary in simulation.
}
Expand All @@ -916,7 +945,7 @@
weight = collision.weight();
}

if (eventcuts.onlyKeepWeightedEvents && std::fabs(weight - 1.0) < 1e-10) {

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[magic-number] 

Avoid magic numbers in expressions. Assign the value to a clearly named variable or constant.
continue;
}

Expand Down
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