This biennial Review summarizes much of particle physics. Using data from previous editions, plus 2658 new measurements from 644 papers, we list, evaluate, and average measured properties of gauge bosons, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as Higgs bosons, heavy neutrinos, and supersymmetric particles. All the particle properties and search limits are listed in Summary Tables. We also give numerous tables, figures, formulae, and reviews of topics such as the Standard Model, particle detectors, probability, and statistics. Among the 112 reviews are many that are new or heavily revised including those on Heavy-Quark and Soft-Collinear Effective Theory, Neutrino Cross Section Measurements, Monte Carlo Event Generators, Lattice QCD, Heavy Quarkonium Spectroscopy, Top Quark, Dark Matter, V-cb & V-ub, Quantum Chromodynamics, High-Energy Collider Parameters, Astrophysical Constants, Cosmological Parameters, and Dark Matter. A booklet is available containing the Summary Tables and abbreviated versions of some of the other sections of this full Review. All tables, listings, and reviews (and errata) are also available on the Particle Data Group website: http://pdg.lbl.gov

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This paper documents an update of the PHOTOS algorithm, by E. Barberio, B. van Eijk and Z. Was, for the Monte Carlo simulation of QED photon radiative corrections in decays. The algorithm is implemented as an independent package written in FORTRAN 77. The program is universal, i.e. it allows for easy interface with \any" program generating decays of \any" particle. The program can be used to estimate the size of the QED bremsstrahlung in the leading-logarithmic (collinear) approximation, but it provides nal states with their full topology, including kinematical e ects due to massive particles. The proper soft photon behaviour is also reproduced. The algorithm is designed in such a w a y that the inclusion (if necessary) of the exact, process-dependent, matrix element subgenerator is possible and straightforward. This update of PHOTOS provides new options to improve the performances of the program in some speci c cases: the interference for two-body particle-antiparticle decays, the double bremsstrahlung, and re nements important for the decays into massive non-relativistic decay products. leptons, resonances, particle decays, Monte Carlo simulation, quantum electrodynamics, leading-log approximations. Nature of physical problem: Most of the decay modes of particles or resonances are accompanied by the QED real photon corrections. The presence of (a) hard photon(s) may a ect the shape of the measured distributions, detection e ciencies and/or experimental selection criteria. Method of solution: The Monte Carlo simulation is best suited for studying the combined process of production and decay of unstable particles, including QED corrections and detector e ciencies. Restrictions on the complexity of the problem: The QED O( ) and O( 2 ) corrections are implemented in the leading-logarithm approximation with the proper soft photon behaviour. Emission of non-collinear hard photons is simulated, but the validity of distribution may be restricted.Typical running time: 500 events/sec (VAX station 4000-90) for the Z ! + decay mode.