A number of constexpr particle constants to avoid hardcoding them directly in various places.
constexpr double muonMassInMeV
the mass of the muon (in MeV)
constexpr double chargedKaonMassInMeV
the mass of the charged kaon (in MeV)
constexpr double protonMassInMeV
the mass of the proton (in MeV)
constexpr double chargedPionMassInMeV
the mass of the charged pion (in MeV)
constexpr double electronMassInMeV
the mass of the electron (in MeV)
constexpr double photonMassInMeV
various mass-less particles
std::array< double, 6 > mass
constexpr TrigParticleMasses()=default