GenParticlesHelper.cc

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#include "PhysicsTools/HepMCCandAlgos/interface/GenParticlesHelper.h"
#include "DataFormats/HepMCCandidate/interface/GenParticle.h"

using namespace reco;

namespace GenParticlesHelper {

  void findParticles(const reco::GenParticleCollection& sourceParticles,
                     reco::GenParticleRefVector& particleRefs,
                     int pdgId,
                     int status) {
    unsigned index = 0;
    for (IG ig = sourceParticles.begin(); ig != sourceParticles.end(); ++ig, ++index) {
      const GenParticle& gen = *ig;

      // status has been specified, and this one does not have the correct
      // status
      if (status && gen.status() != status)
        continue;

      if (std::abs(gen.pdgId()) == pdgId) {
        GenParticleRef genref(&sourceParticles, index);
        particleRefs.push_back(genref);
      }
    }
  }

  void findDescendents(const reco::GenParticleRef& base,
                       reco::GenParticleRefVector& descendents,
                       int status,
                       int pdgId) {
    const GenParticleRefVector& daughterRefs = base->daughterRefVector();

    for (IGR idr = daughterRefs.begin(); idr != daughterRefs.end(); ++idr) {
      if ((*idr)->status() == status && (!pdgId || std::abs((*idr)->pdgId()) == pdgId)) {
        // cout<<"adding "<<(*idr)<<endl;
        descendents.push_back(*idr);
      } else
        findDescendents(*idr, descendents, status, pdgId);
    }
  }

  void findSisters(const reco::GenParticleRef& baseSister, GenParticleRefVector& sisterRefs) {
    assert(baseSister->numberOfMothers() > 0);

    // get first mother
    const GenParticleRefVector& mothers = baseSister->motherRefVector();

    // get sisters
    const GenParticleRefVector allRefs = mothers[0]->daughterRefVector();

    typedef GenParticleRefVector::const_iterator IT;
    for (IT id = allRefs.begin(); id != allRefs.end(); ++id) {
      if (*id == baseSister) {
        continue;  // this is myself
      } else
        sisterRefs.push_back(*id);
    }
  }

  bool isDirect(const reco::GenParticleRef& particle) {
    assert((particle->status() != 0) && (particle->status() < 4));
    if (particle->status() == 3)
      return true;
    else {
      assert(particle->numberOfMothers() > 0);

      // get first mother
      const GenParticleRefVector& mothers = particle->motherRefVector();
      if (mothers[0]->status() == 3)
        return true;
      else
        return false;
    }
  }

  bool hasAncestor(const reco::GenParticle* particle, int pdgId, int status) {
    if (particle->pdgId() == pdgId && particle->status() == status)
      return true;

    const GenParticleRefVector& mothers = particle->motherRefVector();

    for (IGR im = mothers.begin(); im != mothers.end(); ++im) {
      const GenParticle& part = **im;
      if (hasAncestor(&part, pdgId, status))
        return true;
    }

    return false;
  }

  std::ostream& operator<<(std::ostream& out, const reco::GenParticleRef& genRef) {
    if (!out)
      return out;

    out << genRef.key() << " " << genRef->pt();

    return out;
  }

}  // namespace GenParticlesHelper