Revised October 2017 by L. Garren, F. Krauss, C.-J. Lin, S. Navas, P. Richardson, and T. Sjostrand.
The Particle Data Group maintains this numbering scheme in cooperation with Monte Carlo authors and the StdHep
Monte Carlo Standardization project at Fermilab, as part of a system to facilitate translation between different Monte Carlo event generators and detector simulators. The StdHep lists contain a few specialized codes beginning with 99 which are needed for particular event generators, but which are not included in the list of PDG particle numbers.
Comments should be sent to: C.-J. Lin