The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,143 new measurements from 709 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 120 reviews are many that are new or heavily revised, including a new review on Machine Learning, and one on Spectroscopy of Light Meson Resonances. The Review is divided into two volumes. Volume 1 includes the Summary Tables and 97 review articles. Volume 2 consists of the Particle Listings and contains also 23 reviews that address specific aspects of the data presented in the Listings. The complete Review (both volumes) is published online on the website of the Particle Data Group (pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print, as a web version optimized for use on phones, and as an Android app.

We present an up-to-date profile of the Cabibbo-Kobayashi-Maskawa matrix with emphasis on the interpretation of recent CP -violation results from the B factories. For this purpose, we review all relevant experimental and theoretical inputs from the contributing domains of electroweak interaction. We give the "standard" determination of the apex of the Unitarity Triangle, namely the Wolfenstein parameters ρ and η, by means of a global CKM fit. The fit is dominated by the precision measurement of sin 2β by the B factories. A detailed numerical and graphical study of the impact of the results is presented. We propose to include sin 2α from the recent measurement of the time-dependent CP -violating asymmetries in B 0 → ρ + ρ − , using isospin relations to discriminate the penguin contribution. The constraint from ε ′ /ε is discussed. We study the impact from the branching fraction measurement of the rare kaon decay K + → π + νν, and give an outlook into the reach of a future measurement of K 0 L → π 0 νν. The B system is investigated in detail. We display the constraint on 2β + γ and γ from B 0 → D ( * )± π ∓ and B + → D ( * )0 K + decays, respectively. A significant part of this paper is dedicated to the understanding of the dynamics of B decays into ππ, Kπ, ρπ, ρρ and modes related to these by flavor symmetry. Various phenomenological approaches and theoretical frameworks are discussed. We find a remarkable agreement of the ππ and Kπ data with the other constraints in the unitarity plane when the hadronic matrix elements are calculated within QCD Factorization, where we apply a conservative treatment of the theoretical uncertainties. A global fit of QCD Factorization to all ππ and Kπ data leads to precise predictions of the related observables. However sizable phenomenological power corrections are preferred. Using an isospin-based phenomenological parameterization, we analyze separately the B → Kπ decays, and the impact of electroweak penguins in response to recent discussions. We find that the present data are not sufficiently precise to constrain either electroweak parameters or hadronic amplitude ratios. We do not observe any unambiguous sign of New Physics, whereas there is some evidence for potentially large non-perturbative rescattering effects. Finally we use a model-independent description of a large class of New Physics effects in both B 0 B 0 mixing and B decays, namely in the b → d and b → s gluonic penguin amplitudes, to perform a new numerical analysis. Significant non-standard corrections cannot be excluded yet, however Standard Model solutions are favored in most cases. In the appendix to this paper we propose a frequentist method to extract a confidence level on ∆m s from the experimental information on B 0 s B 0 s oscillation. In addition we describe a novel approach to combine potentially inconsistent measurements. All results reported in this paper have been obtained with the numerical analysis package CKMfitter, featuring the frequentist statistical approach Rfit.

The BABAR Collaboration BABAR, the detector for the SLAC PEP-II asymmetric e + e − B Factory operating at the Υ (4S) resonance, was designed to allow comprehensive studies of CP -violation in B-meson decays. Charged particle tracks are measured in a multi-layer silicon vertex tracker surrounded by a cylindrical wire drift chamber. Electromagnetic showers from electrons and photons are detected in an array of CsI crystals located just inside the solenoidal coil of a superconducting magnet. Muons and neutral hadrons are identified by arrays of resistive plate chambers inserted into gaps in the steel flux return of the magnet. Charged hadrons are identified by dE/dx measurements in the tracking detectors and in a ring-imaging Cherenkov detector surrounding the drift chamber. The trigger, data acquisition and data-monitoring systems , VME-and network-based, are controlled by custom-designed online software. Details of the layout and performance of the detector components and their associated electronics and software are presented.

Hadronic τ decays provide a clean laboratory for the precise study of quantum chromodynamics (QCD). Observables based on the spectral functions of hadronic τ decays can be related to QCD quark-level calculations to determine fundamental quantities like the strong coupling constant, parameters of the chiral Lagrangian, |Vus|, the mass of the strange quark, and to simultaneously test the concept of quark-hadron duality. Using the best available measurements and a revisited analysis of the theoretical framework, the value αS(m 2 τ ) = 0.345 ± 0.004exp ± 0.009 th is obtained. Taken together with the determination of αS(M 2 Z ) from the global electroweak fit, this result leads to the most accurate test of asymptotic freedom: the value of the logarithmic slope of α −1 s (s) is found to agree with QCD at a precision of 4%. The τ spectral functions can also be used to determine hadronic quantities that, due to the nonperturbative nature of long-distance QCD, cannot be computed from first principles. An example for this is the contribution from hadronic vacuum polarization to loop-dominated processes like the anomalous magnetic moment of the muon. This article reviews the measurements of nonstrange and strange τ spectral functions and their phenomenological applications.