he Pierre Auger Observatory, located on a vast, high plain in western\ud Argentina, is the world's largest cosmic ray observatory. The objectives\ud of the Observatory are to probe the origin and characteristics of cosmic\ud rays above 10(17) eV and to study the interactions of these, the most\ud energetic particles observed in nature. The Auger design features an\ud array of 1660 water Cherenkov particle detector stations spread over\ud 3000 km(2) overlooked by 24 air fluorescence telescopes. In addition,\ud three high elevation fluorescence telescopes overlook a 23.5 km(2),\ud 61-detector infilled array with 750 in spacing. The Observatory has been\ud in successful operation since completion in 2008 and has recorded data\ud from an exposure exceeding 40,000 km(2) sr yr. This paper describes the\ud design and performance of the detectors, related subsystems and\ud infrastructure that make up the Observatory

a b s t r a c tThe Pierre Auger Observatory is a hybrid detector for ultra-high energy cosmic rays. It combines a surface array to measure secondary particles at ground level together with a fluorescence detector to measure the development of air showers in the atmosphere above the array. The fluorescence detector comprises 24 large telescopes specialized for measuring the nitrogen fluorescence caused by charged particles of cosmic ray air showers. In this paper we describe the components of the fluorescence detector including its optical system, the design of the camera, the electronics, and the systems for relative and absolute calibration. We also discuss the operation and the monitoring of the detector. Finally, we evaluate the detector performance and precision of shower reconstructions.

An angular analysis of the B 0 → K Ã0 ð→ K þ π − Þμ þ μ − decay is presented using a dataset corresponding to an integrated luminosity of 4.7 fb −1 of pp collision data collected with the LHCb experiment. The full set of CP-averaged observables are determined in bins of the invariant mass squared of the dimuon system. Contamination from decays with the K þ π − system in an S-wave configuration is taken into account. The tension seen between the previous LHCb results and the standard model predictions persists with the new data. The precise value of the significance of this tension depends on the choice of theory nuisance parameters.

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Searches are performed for a low-mass dimuon resonance, X, produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using a data sample corresponding to an integrated luminosity of 5.1 fb−1 and collected with the LHCb detector. The X bosons can either decay promptly or displaced from the proton-proton collision, where in both cases the requirements placed on the event and the assumptions made about the production mechanisms are kept as minimal as possible. The searches for promptly decaying X bosons explore the mass range from near the dimuon threshold up to 60 GeV, with nonnegligible X widths considered above 20 GeV. The searches for displaced X → μ+μ− decays consider masses up to 3 GeV. None of the searches finds evidence for a signal and 90% confidence-level exclusion limits are placed on the X → μ+μ− cross sections, each with minimal model dependence. In addition, these results are used to place world-leading constraints on GeV-scale bosons in the two-Higgs-doublet and hidden-valley scenarios.