A search for the Standard Model Higgs boson in proton–proton collisions with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities of approximately 4.8 fb−1 collected at √s=7 TeV in 2011 and 5.8 fb−1 at √s=8 TeV in 2012. Individual searches in the channels H→ZZ(⁎)→4ℓ, H→γγ and H→WW(⁎)→eνμν in the 8 TeV data are combined with previously published results of searches for H→ZZ(⁎), WW(⁎), bb and τ+τ− in the 7 TeV data and results from improved analyses of the H→ZZ(⁎)→4ℓ and H→γγ channels in the 7 TeV data. Clear evidence for the production of a neutral boson with a measured mass of 126.0±0.4(stat)±0.4(sys) GeV is presented. This observation, which has a significance of 5.9 standard deviations, corresponding to a background fluctuation probability of 1.7×10−9, is compatible with the production and decay of the Standard Model Higgs boson

The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 3,324 new measurements from 878 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 High Energy Soft QCD and Diffraction and one on the Determination of CKM Angles from B Hadrons. The Review is divided into two volumes. Volume 1 includes the Summary Tables and 98 review articles. Volume 2 consists of the Particle Listings and contains also 22 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 and as a web version optimized for use on phones as well as an Android app.

The ATLAS experiment is preparing for data taking at 14 TeV collision energy. A rich discovery physics program is being prepared in addition to the detailed study of Standard Model processes which will be produced in abundance. The ATLAS multi-level trigger system is designed to accept one event in 2 • 10B to enable the selection of rare and unusual physics events. The ATLAS calorimeter system is a precise instrument, which includes liquid Argon electromagnetic and hadronic components as well as a scintillator-tile hadronic calorimeter. All these components are used in the various levels of the trigger system. A wide physics coverage is ensured by inclusively selecting events with candidate electrons, photons, taus, jets or those with large missing transverse energy. The commissioning of the trigger system is being performed with cosmic ray events and by replaying simulated Monte Carlo events through the trigger and data acquisition system.

This paper reports world averages of measurements of b-hadron, c-hadron, and τ -lepton properties obtained by the Heavy Flavour Averaging Group using results available before April 2021. In rare cases, significant results obtained several months later are also used. For the averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters, CP violation parameters, parameters of semileptonic decays, and Cabibbo-Kobayashi-Maskawa matrix elements. Selected world averages -continued from previous page. ∆Γ d /Γ d 0.001 ± 0.010 |q d /p d | 1.0010 ± 0.0008 ∆m s 17.765 ± 0.006 ps −1 ∆Γ s +0.084 ± 0.005 ps −1 |q s /p s | 1.0003 ± 0.0014 φ ccs s −0.049 ± 0.019 rad Unitarity-Triangle angle parameters sin2β ≡ sin2φ 1 0.699 ± 0.017 β ≡ φ 1 (22.2 ± 0.7) • −ηS φK 0 S 0.74 +0.11 −0.13 −ηS η K 0 0.63 ± 0.06 −ηS K 0 S K 0 S K 0 S 0.83 ± 0.17 φ s (φφ) −0.073 ± 0.115 ± 0.027 rad S B 0 s →K + K − , C B 0 s →K + K − (0.14 ± 0.03, 0.17 ± 0.03) −ηS J/ψ π 0 0.86 ± 0.14 −ηS D + D − 0.84 ± 0.12 −ηS J/ψ ρ 0 0.66 +0.13 −0.12 +0.09 −0.03(0.343 ± 0.002)% τ parameters, lepton universality, and |V us | g τ /g µ 1.0009 ± 0.0014 g τ /g e 1.0027 ± 0.0014 g µ /g e 1.0019 ± 0.0014* )0 s B ( * )0 s ) = (87.0 ± 1.7)% [34] measured as described in Ref. [35]. The proportions of the various production channels for non-strange B mesons have also been measured [22]. 4.3 b-hadron production fractions at high energy At high energy, all species of weakly decaying b hadrons may be produced, either directly or in strong and electromagnetic decays of excited b hadrons. Before 2010, it was assumed that the fractions of different species in unbiased samples of high-p T b-hadron jets where independent of whether they originated from Z decays, pp collisions at the Tevatron, or pp collisions at the LHC. This hypothesis was plausible under the condition Q 2 Λ 2 QCD , namely, that the square of the momentum transfer to the produced b quarks is large compared with the square of the hadronization energy scale. This hypothesis is correct in the limit p T → ∞, in which the production mechanism of a b hadron is completely described by the fragmentation of the b quark. For finite p T , however, there are interference effects of the production mechanism of the b quark and its hadronization. While formally suppressed by inverse powers of p T , these effects may be sizable, especially when the fragmentation probabilities are small as, e.g., in the case of b baryons. In fact, the available data show that the fractions depend on the kinematics of the produced b hadron. Both CDF and LHCb reported a p T dependence of the fractions, with the fraction of Λ 0 b baryons observed at low p T being enhanced with respect to that seen at LEP at higher p T . In our previous publication [1], we presented two sets of averages, one including only measurements performed at LEP, and another including only measurements performed ...

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.