SHiP::MCParticle Struct Reference

Monte Carlo particle — input to simulation. More...

#include <MCParticle.hpp>

Public Member Functions
bool	operator== (MCParticle const &) const =default

Public Attributes
std::int32_t	pdg_code {0}
std::array< double, 3 >	vertex {0, 0, 0}
	Production vertex [mm].
std::array< double, 3 >	momentum {0, 0, 0}
	Momentum (px, py, pz) [GeV/c].
double	energy {0}
	Total energy [GeV].
double	time {0}
	Production time [ns].
std::int32_t	mother_id {-1}
	First mother (-1 = none)
std::vector< std::int32_t >	mothers {}
	All mothers (see above)
std::int32_t	status {1}
	HepMC status (see above)

Detailed Description

Monte Carlo particle — input to simulation.

Mother indices refer to the same collection (this event's vector of MCParticle), not to the generator's own record: a producer that filters the record must remap them. -1 means "no mother".

An entry can have several mothers — a hadron from string fragmentation, the products of a hard 2 -> n process, two partons joined into one. mothers is the complete, resolved list: Pythia8's Particle::motherList() provides exactly it, derived from the raw mother1/mother2 pair and the native status, which is what distinguishes an inclusive range of mothers from two distinct ones. mother_id is its first element, or -1 when the entry has no mother.

An empty mothers means either that the entry has no mothers or that it was written before v0.5.0, when the field did not exist. mother_id stays the portable single-mother accessor across all versions.

Taken together, for every entry i of a collection of N particles:

• mother_id is -1 or in [0, N);
• every element of mothers is in [0, N) — the -1 sentinel belongs to mother_id alone and never appears in the list;
• a non-empty mothers starts with mother_id;
• the elements of mothers are distinct, and none of them is i. mothers_are_consistent() checks exactly this; mothers_are_populated() adds the requirement that current-schema data actually fill the list. Mothers are deliberately not required to precede their daughters: a producer that filters a generator record and remaps indices may reorder it.

status follows the HepMC convention — the codes Pythia8's statusHepMC() produces, the same set EDM4hep uses for generatorStatus:

• 0: an empty entry, to be skipped unconditionally
• 1: final state, i.e. not decayed by the generator; these are the entries a detector simulation tracks, and they may well be unstable
• 2: a decayed Standard Model hadron, tau or muon
• 3: a documentation entry
• 4: an incoming beam particle
• 11-200: an intermediate entry, generator-dependent classification

Member Function Documentation

operator==()

bool SHiP::MCParticle::operator== ( MCParticle const &  ) const

default

Member Data Documentation

energy

double SHiP::MCParticle::energy {0}

Total energy [GeV].

momentum

std::array<double, 3> SHiP::MCParticle::momentum {0, 0, 0}

Momentum (px, py, pz) [GeV/c].

mother_id

std::int32_t SHiP::MCParticle::mother_id {-1}

First mother (-1 = none)

mothers

std::vector<std::int32_t> SHiP::MCParticle::mothers {}

All mothers (see above)

pdg_code

std::int32_t SHiP::MCParticle::pdg_code {0}

status

std::int32_t SHiP::MCParticle::status {1}

HepMC status (see above)

time

double SHiP::MCParticle::time {0}

Production time [ns].

vertex

std::array<double, 3> SHiP::MCParticle::vertex {0, 0, 0}

Production vertex [mm].

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The documentation for this struct was generated from the following file:

• include/SHiP/MCParticle.hpp