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Particle.hh
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// -*- C++ -*-
#ifndef RIVET_Particle_HH
#define RIVET_Particle_HH
#include "Rivet/Particle.fhh"
#include "Rivet/ParticleBase.hh"
#include "Rivet/Config/RivetCommon.hh"
namespace Rivet {
/// Representation of particles from a HepMC::GenEvent.
class Particle : public ParticleBase {
public:
/// Default constructor.
/// @deprecated A particle without info is useless. This only exists to keep STL containers happy.
Particle()
: ParticleBase(),
_original(0), _id(0), _momentum()
{ }
/// Constructor without GenParticle.
Particle(PdgId pid, const FourMomentum& mom)
: ParticleBase(),
_original(0), _id(pid), _momentum(mom)
{ }
/// Constructor from a HepMC GenParticle.
Particle(const GenParticle& gp)
: ParticleBase(),
_original(&gp), _id(gp.pdg_id()),
_momentum(gp.momentum())
{ }
/// Constructor from a HepMC GenParticle pointer.
Particle(const GenParticle* gp)
: ParticleBase(),
_original(gp), _id(gp->pdg_id()),
_momentum(gp->momentum())
{ }
public:
/// @name Basic particle specific properties
//@{
/// Get a const reference to the original GenParticle.
const GenParticle* genParticle() const {
return _original;
}
/// Cast operator for conversion to GenParticle*
operator const GenParticle* () const { return genParticle(); }
/// The momentum.
const FourMomentum& momentum() const {
return _momentum;
}
/// Set the momentum.
Particle& setMomentum(const FourMomentum& momentum) {
_momentum = momentum;
return *this;
}
//@}
/// @name Particle ID code accessors
//@{
/// This Particle's PDG ID code.
PdgId pid() const { return _id; }
/// Absolute value of the PDG ID code.
PdgId abspid() const { return std::abs(_id); }
/// This Particle's PDG ID code (alias).
/// @deprecatedThe pid/abspid form is nicer (don't need to remember
/// lower/upper case, doesn't visually stick out in the code, etc. ...)
PdgId pdgId() const { return _id; }
//@}
/// @name Particle species properties
//@{
/// The charge of this Particle.
double charge() const {
return PID::charge(pdgId());
}
/// Three times the charge of this Particle (i.e. integer multiple of smallest quark charge).
int threeCharge() const {
return PID::threeCharge(pdgId());
}
/// Is this a hadron?
bool isHadron() const { return PID::isHadron(pdgId()); }
/// Is this a meson?
bool isMeson() const { return PID::isMeson(pdgId()); }
/// Is this a baryon?
bool isBaryon() const { return PID::isBaryon(pdgId()); }
/// Is this a lepton?
bool isLepton() const { return PID::isLepton(pdgId()); }
/// Is this a neutrino?
bool isNeutrino() const { return PID::isNeutrino(pdgId()); }
/// Does this (hadron) contain a b quark?
bool hasBottom() const { return PID::hasBottom(pdgId()); }
/// Does this (hadron) contain a c quark?
bool hasCharm() const { return PID::hasCharm(pdgId()); }
// /// Does this (hadron) contain an s quark?
// bool hasStrange() const { return PID::hasStrange(pdgId()); }
//@}
/// @name Ancestry properties
//@{
/// Check whether a given PID is found in the GenParticle's ancestor list
///
/// @note This question is valid in MC, but may not be answerable
/// experimentally -- use this function with care when replicating
/// experimental analyses!
bool hasAncestor(PdgId pdg_id) const;
/// @brief Determine whether the particle is from a hadron or tau decay
///
/// Specifically, walk up the ancestor chain until a status 2 hadron or
/// tau is found, if at all.
///
/// @note This question is valid in MC, but may not be perfectly answerable
/// experimentally -- use this function with care when replicating
/// experimental analyses!
bool fromDecay() const;
/// @brief Determine whether the particle is from a b-hadron decay
///
/// @note This question is valid in MC, but may not be perfectly answerable
/// experimentally -- use this function with care when replicating
/// experimental analyses!
bool fromBottom() const;
/// @brief Determine whether the particle is from a c-hadron decay
///
/// @note If a hadron contains b and c quarks it is considered a bottom
/// hadron and NOT a charm hadron.
///
/// @note This question is valid in MC, but may not be perfectly answerable
/// experimentally -- use this function with care when replicating
/// experimental analyses!
bool fromCharm() const;
// /// @brief Determine whether the particle is from a s-hadron decay
// ///
// /// @note If a hadron contains b or c quarks as well as strange it is
// /// considered a b or c hadron, but NOT a strange hadron.
// ///
// /// @note This question is valid in MC, but may not be perfectly answerable
// /// experimentally -- use this function with care when replicating
// /// experimental analyses!
// bool fromStrange() const;
/// @brief Determine whether the particle is from a tau decay
///
/// @note This question is valid in MC, but may not be perfectly answerable
/// experimentally -- use this function with care when replicating
/// experimental analyses!
bool fromTau() const;
//@}
/// @name Decay info
//@{
/// Whether this particle is stable according to the generator
bool isStable() const {
return genParticle() != NULL && genParticle()->status() == 1 && genParticle()->end_vertex() == NULL;
}
/// Get a list of the direct descendants from the current particle
vector<Particle> children() const {
vector<Particle> rtn;
if (isStable()) return rtn;
/// @todo Remove this const mess crap when HepMC doesn't suck
HepMC::GenVertex* gv = const_cast<HepMC::GenVertex*>( genParticle()->end_vertex() );
/// @todo Would like to do this, but the range objects are broken
// foreach (const GenParticle* gp, gv->particles(HepMC::children))
// rtn += Particle(gp);
for (GenVertex::particle_iterator it = gv->particles_begin(HepMC::children); it != gv->particles_end(HepMC::children); ++it)
rtn += Particle(*it);
return rtn;
}
/// Get a list of all the descendants (including duplication of parents and children) from the current particle
/// @todo Use recursion through replica-avoiding MCUtils functions to avoid bookkeeping duplicates
/// @todo Insist that the current particle is post-hadronization, otherwise throw an exception?
vector<Particle> allDescendants() const {
vector<Particle> rtn;
if (isStable()) return rtn;
/// @todo Remove this const mess crap when HepMC doesn't suck
HepMC::GenVertex* gv = const_cast<HepMC::GenVertex*>( genParticle()->end_vertex() );
/// @todo Would like to do this, but the range objects are broken
// foreach (const GenParticle* gp, gv->particles(HepMC::descendants))
// rtn += Particle(gp);
for (GenVertex::particle_iterator it = gv->particles_begin(HepMC::descendants); it != gv->particles_end(HepMC::descendants); ++it)
rtn += Particle(*it);
return rtn;
}
/// Get a list of all the stable descendants from the current particle
/// @todo Use recursion through replica-avoiding MCUtils functions to avoid bookkeeping duplicates
/// @todo Insist that the current particle is post-hadronization, otherwise throw an exception?
vector<Particle> stableDescendants() const {
vector<Particle> rtn;
if (isStable()) return rtn;
/// @todo Remove this const mess crap when HepMC doesn't suck
HepMC::GenVertex* gv = const_cast<HepMC::GenVertex*>( genParticle()->end_vertex() );
/// @todo Would like to do this, but the range objects are broken
// foreach (const GenParticle* gp, gv->particles(HepMC::descendants))
// if (gp->status() == 1 && gp->end_vertex() == NULL)
// rtn += Particle(gp);
for (GenVertex::particle_iterator it = gv->particles_begin(HepMC::descendants); it != gv->particles_end(HepMC::descendants); ++it)
if ((*it)->status() == 1 && (*it)->end_vertex() == NULL)
rtn += Particle(*it);
return rtn;
}
/// Flight length (divide by mm or cm to get the appropriate units)
double flightLength() const {
if (isStable()) return -1;
if (genParticle() == NULL) return 0;
if (genParticle()->production_vertex() == NULL) return 0;
const HepMC::FourVector v1 = genParticle()->production_vertex()->position();
const HepMC::FourVector v2 = genParticle()->end_vertex()->position();
return sqrt(sqr(v2.x()-v1.x()) + sqr(v2.y()-v1.y()) + sqr(v2.z()-v1.z()));
}
//@}
private:
/// A pointer to the original GenParticle from which this Particle is projected.
const GenParticle* _original;
/// The PDG ID code for this Particle.
PdgId _id;
/// The momentum of this projection of the Particle.
FourMomentum _momentum;
};
/// @name String representation
//@{
/// Print a ParticlePair as a string.
inline std::string to_str(const ParticlePair& pair) {
stringstream out;
out << "["
<< PID::toParticleName(pair.first.pdgId()) << " @ "
<< pair.first.momentum().E()/GeV << " GeV, "
<< PID::toParticleName(pair.second.pdgId()) << " @ "
<< pair.second.momentum().E()/GeV << " GeV]";
return out.str();
}
/// Allow ParticlePair to be passed to an ostream.
inline std::ostream& operator<<(std::ostream& os, const ParticlePair& pp) {
os << to_str(pp);
return os;
}
//@}
}
#endif

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