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Particle Class Reference

The Particle class holds information of any particle used in Sartre. More...

 #include "Event.h"

Public Data Member

Detailed Description

The Particle class contains all information needed to describe any particle used in Sarte. The particles are stored in an internal list in the Event class. It is a lightweight class without any member functions and all data members are public. The data members hold information on the particle's status (stable/decayed), 4-momentum, parent particle(s), daughter particle(s). Each particle is uniquely identified by an index number.

Note that moment and energy (TLorentzVector p) for nuclei are always expressed as per-nucleon.

Data Member Documentation

int index

Index of the particle. The index starts at 0. index=0 is typically the incoming electron and index=1 the incoming hadron. The index identifies a particle unambiguously in the event.

int pdgId

The ID of the particle following the PDG scheme. Note that it also holds nuclei and heavy fragments. The PDG for nuclei is coded as 10LZZZAAAI, where L = number of strange quark (for hypernuclei), I = isomer level, with I = 0 corresponding to the ground state and I > 0 to excitations. For example the Au ion is decoded as 1000791970.

int status

We follow HepMC conventions (February 2009).
0 : an empty entry, with no meaningful information (not used in Sartre)
1 : a final-state particle, i.e. a particle that is not decayed further by the generator (may also include unstable particles that are to be decayed later)
2 : a decayed hadron or tau or mu lepton, or an intermediate virtual particle.
3 : a documentation entry (not used in Sartre)
4 : an incoming beam particle;
11 - 200 : an intermediate (decayed/branched/...) particle that does not fulfill the criteria of status code 2 (not used in Sartre)
At the moment Sartre only supports status codes 1,2, and 4.

TLorentzVector p

Four momentum vector of the particle. See ROOT documentation for details. The vector is defined with respect to the beam axis. The beam electron comes from the right, with a negative p_z, the hadron beam is coming from the left and has a positive p_z. Note that momenta and energy (TLorentzVector p) for nuclei are always expressed as per-nucleon.

vector<int> parents

Vector holding the index of each parent. In Sartre there are currently at most 2 parents.

vector<int> daughters

Vector holding the index of the daughter(s) of the particle.