ParticleJetLabelCommon.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#include "ParticleJetTools/ParticleJetLabelCommon.h"
 
#include "TruthUtils/HepMCHelpers.h"
 
// private internal functions
namespace {
  // this returns a charm child if it exists, otherwise returns the
  // particle itself. If the truth record contains broken links return
  // a nullptr.
  const xAOD::TruthParticle* getCharmChild(const xAOD::TruthParticle* p) {
    for (unsigned int n = 0; n < p->nChildren(); n++) {
      const xAOD::TruthParticle* child = p->child(n);
      // nullptr would indicate a broken truth record, but the rest of
      // the code lets this pass silently so we'll do the same here.
      if (!child) return nullptr;
      if (MC::hasCharm(child->pdgId())) {
        return getCharmChild(child);
      }
    }
    return p;
  }
}
 
namespace ParticleJetTools {
 
  // the code below is taken from ParticleJetDeltaRLabelTool with
  // minimal modification
  // --------------------------------------------------------------
 
  inline bool isChild( const xAOD::TruthParticle* p, const xAOD::TruthParticle* c) {
 
    if ( HepMC::is_same_particle(p,c) ) { return false; }
 
    for (size_t iC = 0; iC < p->nChildren(); iC++) {
      const xAOD::TruthParticle* cc = p->child(iC);
      if (!cc) { continue; }
 
      if ( HepMC::is_same_particle(cc,c) ) { return true; }
 
      if (isChild(cc, c)) { return true; }
    }
 
    return false;
  }
 
  Amg::Vector3D p3(const xAOD::TruthVertex* p) {
    if (!p) return {NAN, NAN, NAN};
    return {p->x(), p->y(), p->z()};
  }
  Amg::Vector3D p3(const xAOD::Jet& j) {
    return {j.px(), j.py(), j.pz()};
  }
  Amg::Vector3D signalProcessP3(const xAOD::TruthEventContainer& events) {
    if (events.empty()) return {NAN, NAN, NAN};
    return p3(events.at(0)->signalProcessVertex());
  }
 
 
  void childrenRemoved
  ( const std::vector<const xAOD::TruthParticle*>& parents
    , std::vector<const xAOD::TruthParticle*>& children
    ) {
 
    if ( &parents == &children ) {
      // Same vector provided for both inputs. Extra care needed in
      // this case...
      const std::vector<const xAOD::TruthParticle*> copyParents = parents;
      childrenRemoved(copyParents, children);
      return;
    }
    // We can now safely assume that parents will not be modified
    // during this loop.
    for ( const xAOD::TruthParticle* p : parents ) {
      if (!p) continue;
      children.erase(std::remove_if(children.begin(),
                                    children.end(),
                                    [p](const xAOD::TruthParticle* c) { return (c && isChild(p, c)); }),
                     children.end());
      // auto erased = std::erase_if(children, [p](const xAOD::TruthParticle* c) { return (c && isChild(p, c)); }); // C++20
    }
    return;
  }
 
 
  // ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  // End of code copied from ParticleJetDeltaRLabelTool
 
  void LabelNames::check() {
    auto chk = [](const std::string& s, const std::string& varname) {
      if (s.empty()) throw std::runtime_error(
        "name for '" + varname + "' is not specified in particle jet tools"
        " configuration");
    };
#define CHECK(var) chk(var, #var)
    CHECK(singleint);
    CHECK(doubleint);
    CHECK(pt);
    CHECK(Lxy);
    CHECK(dr);
    CHECK(pdgId);
    CHECK(positionDPhi);
    CHECK(positionDEta);
    CHECK(uniqueID);
    CHECK(childLxy);
    CHECK(childPt);
    CHECK(childPdgId);
    CHECK(childPositionDPhi);
    CHECK(childPositionDEta);
#undef CHECK
  }
 
  LabelDecorators::LabelDecorators(const LabelNames& n):
    singleint(n.singleint),
    doubleint(n.doubleint),
    pt(n.pt),
    Lxy(n.Lxy),
    dr(n.dr),
    pdgId(n.pdgId),
    positionDPhi(n.positionDPhi),
    positionDEta(n.positionDEta),
    uniqueID(n.uniqueID),
    childLxy(n.childLxy),
    childPt(n.childPt),
    childPdgId(n.childPdgId),
    childPositionDPhi(n.childPositionDPhi),
    childPositionDEta(n.childPositionDEta),
    // ATLASRECTS-8290: this is for backward compatability, remove eventually
    acc_uid(n.useBarcode ? "barcode" : "uid")
  {
  }
 
 
  // key might be added back if we figure out how to get the store
  // gate key from a read handle in analysis base
  IParticleLinker::IParticleLinker(
    const SG::ReadHandleKey<xAOD::TruthParticleContainer>& /* key */,
    const std::string& linkname):
    m_dec(linkname)
  {
  }
  void IParticleLinker::decorate(
    const xAOD::Jet& jet,
    const std::vector<const xAOD::TruthParticle*>& ipv) const
  {
    IPLV links;
    for (const xAOD::TruthParticle* ip: ipv) {
      // I copied this whole song and dance from setAssociatedObjects
      // in the jet edm. It would be much easier if we could store the
      // container hash in this object and use ElementLink(sgkey,
      // index) but that seems to break in AnalysisBase
      IPLV::value_type link;
      const auto* ipc = dynamic_cast<const xAOD::IParticleContainer*>(
        ip->container());
      link.toIndexedElement(*ipc, ip->index());
      links.push_back(link);
    }
    m_dec(jet) = links;
  }
 
  void setJetLabels(const xAOD::Jet& jet,
                    const Particles& particles,
                    const LabelDecorators& decs) {
 
    // we also want to save information about the maximum pt particle of the labeling partons
    auto getMaxPtPart = [](const auto& container) -> const xAOD::TruthParticle* {
      if (container.size() == 0) return nullptr;
      auto itr = std::max_element(container.begin(), container.end(),
                                  [](auto* p1, auto* p2) {
                                    return p1->pt() < p2->pt();
                                  });
      return *itr;
    };
 
    // set truth label for jets above pt threshold
    // hierarchy: b > c > tau > light
    int label = 0; // default: light
    const xAOD::TruthParticle* labelling_particle = nullptr;
    const xAOD::TruthParticle* child_particle = nullptr;
    if (particles.b.size()) {
      label = 5;
      labelling_particle = getMaxPtPart(particles.b);
      child_particle = getCharmChild(labelling_particle);
    } else if (particles.c.size()) {
      label = 4;
      labelling_particle = getMaxPtPart(particles.c);
    } else if (particles.tau.size()) {
      label = 15;
      labelling_particle = getMaxPtPart(particles.tau);
    }
 
    const Amg::Vector3D& origin = particles.origin;
 
    // decorate info about the labelling particle
    decs.singleint(jet) = label;
    if (label == 0) {
      decs.pt(jet) = NAN;
      decs.Lxy(jet) = NAN;
      decs.dr(jet) = NAN;
      decs.pdgId(jet) = 0;
      decs.positionDPhi(jet) = NAN;
      decs.positionDEta(jet) = NAN;
      decs.uniqueID(jet) = HepMC::INVALID_PARTICLE_ID;
      decs.childLxy(jet) = NAN;
      decs.childPt(jet) = NAN;
      decs.childPdgId(jet) = 0;
      decs.childPositionDPhi(jet) = NAN;
      decs.childPositionDEta(jet) = NAN;
    } else {
      decs.pt(jet) = partPt(labelling_particle);
      decs.Lxy(jet) = partLxy(labelling_particle, origin);
      decs.dr(jet) = partDR(labelling_particle, jet);
      decs.pdgId(jet) = partPdgId(labelling_particle);
      decs.positionDPhi(jet) = positionDPhi(labelling_particle, jet, origin);
      decs.positionDEta(jet) = positionDEta(labelling_particle, jet, origin);
      decs.uniqueID(jet) = labelling_particle ?
        // ATLASRECTS-8290: this should be replaced with ->uid()
        decs.acc_uid(*labelling_particle) : HepMC::INVALID_PARTICLE_ID;
      decs.childLxy(jet) = partLxy(child_particle, origin);
      decs.childPt(jet) = partPt(child_particle);
      decs.childPdgId(jet) = partPdgId(child_particle);
      decs.childPositionDPhi(jet) = positionDPhi(child_particle, jet, origin);
      decs.childPositionDEta(jet) = positionDEta(child_particle, jet, origin);
    }
 
    // extended flavour label
    int double_label = 0;
    if (particles.b.size()) {
      if (particles.b.size() >= 2)
        double_label = 55;
 
      else if (particles.c.size())
        double_label = 54;
 
      else
        double_label = 5;
 
    } else if (particles.c.size()) {
      if (particles.c.size() >= 2)
        double_label = 44;
 
      else
        double_label = 4;
 
    } else if (particles.tau.size()){
 
      bool hasElectrondecay = false;
      bool hasMuondecay = false;
      bool hasHadronicdecay = false;
      for (auto itau: particles.tau){
        for (size_t i = 0; i< itau->nChildren(); i++){ // tau children loop
          if (itau->child(i)->absPdgId() == 12 || itau->child(i)->absPdgId() == 14 || itau->child(i)->absPdgId() == 16) continue; 
          if (MC::isMuon(itau->child(i))) hasMuondecay = true;
          else if (MC::isElectron(itau->child(i))) hasElectrondecay = true;
          else hasHadronicdecay = true;
        }
      }
 
      if (particles.tau.size() >= 2){
        // check if we have at least one hadronic tau
        if (hasHadronicdecay){
          // check if we have also tau->mu decay 
          if (hasMuondecay) double_label = 151513;
          // check if we have also tau->el decay 
          else if (hasElectrondecay) double_label = 151511;
          // otherwise fully hadronic di-tau decay 
          else double_label = 1515;
    }
      } else { 
        // only consider hadronic tau decay
        if (hasHadronicdecay) double_label = 15;
      }
      
    }
 
    decs.doubleint(jet) = double_label;
 
  }
 
  void setJetLabels(const xAOD::Jet& jet,
                    const Particles& particles,
                    const LabelNames& names) {
    setJetLabels(jet, particles, LabelDecorators(names));
  }
 
  float partPt(const xAOD::TruthParticle* part) {
    if (!part) return NAN;
    return part->pt();
  }
  float partLxy(const xAOD::TruthParticle* part, const Amg::Vector3D& origin) {
    if (!part) return NAN;
    if (const auto* vx = part->decayVtx() ) return (p3(vx) - origin).perp();
    return INFINITY;
  }
  float partDR(const xAOD::TruthParticle* part, const xAOD::Jet& jet) {
    if (!part) return NAN;
    return part->p4().DeltaR(jet.p4());
  }
  int partPdgId(const xAOD::TruthParticle* part) {
    if (!part) return 0;
    return part->pdgId();
  }
  float positionDPhi(const xAOD::TruthParticle* part,
                     const xAOD::Jet& jet,
                     const Amg::Vector3D& origin) {
    if (!part) return NAN;
    if (const auto* vx = part->decayVtx() ) {
      Amg::Vector3D displacement = p3(vx) - origin;
      return p3(jet).deltaPhi(displacement);
    }
    return INFINITY;
  }
  float positionDEta(const xAOD::TruthParticle* part,
                     const xAOD::Jet& jet,
                     const Amg::Vector3D& origin) {
    if (!part) return NAN;
    if (const auto* vx = part->decayVtx() ) {
      Amg::Vector3D displacement = p3(vx) - origin;
      return displacement.eta() - jet.eta();
    }
    return INFINITY;
  }
 
}