We present cosmological parameter constraints from a tomographic weak gravitational lensing analysis of ∼450 deg² of imaging data from the Kilo Degree Survey (KiDS). For a flat Λ cold dark matter (ΛCDM) cosmology with a prior on H₀ that encompasses the most recent direct measurements, we find |$S_8\equiv \sigma _8\sqrt{\Omega _{\rm m}/0.3}=0.745\pm 0.039$|⁠. This result is in good agreement with other low-redshift probes of large-scale structure, including recent cosmic shear results, along with pre-Planck cosmic microwave background constraints. A 2.3σ tension in S₈ and ‘substantial discordance’ in the full parameter space is found with respect to the Planck 2015 results. We use shear measurements for nearly 15 million galaxies, determined with a new improved ‘self-calibrating’ version of lensfit validated using an extensive suite of image simulations. Four-band ugri photometric redshifts are calibrated directly with deep spectroscopic surveys. The redshift calibration is confirmed using two independent techniques based on angular cross-correlations and the properties of the photometric redshift probability distributions. Our covariance matrix is determined using an analytical approach, verified numerically with large mock galaxy catalogues. We account for uncertainties in the modelling of intrinsic galaxy alignments and the impact of baryon feedback on the shape of the non-linear matter power spectrum, in addition to the small residual uncertainties in the shear and redshift calibration. The cosmology analysis was performed blind. Our high-level data products, including shear correlation functions, covariance matrices, redshift distributions, and Monte Carlo Markov chains are available at http://kids.strw.leidenuniv.nl.

The current standard model of cosmology successfully describes a variety of measurements, but the nature of its main ingredients, dark matter and dark energy, remains unknown. Euclid is a medium-class mission in the Cosmic Vision 2015–2025 programme of the European Space Agency (ESA) that will provide high-resolution optical imaging, as well as near-infrared imaging and spectroscopy, over about 14 000 deg² of extragalactic sky. In addition to accurate weak lensing and clustering measurements that probe structure formation over half of the age of the Universe, its primary probes for cosmology, these exquisite data will enable a wide range of science. This paper provides a high-level overview of the mission, summarising the survey characteristics, the various data-processing steps, and data products. We also highlight the main science objectives and expected performance.

We present the results of a search for dark matter weakly interacting massive particles (WIMPs) in the mass range below $20\mathrm{GeV}/c^2$ using a target of low-radioactivity argon with a 6786.0 kg d exposure. The data were obtained using the DarkSide-50 apparatus at Laboratori Nazionali del Gran Sasso. The analysis is based on the ionization signal, for which the DarkSide-50 time projection chamber is fully efficient at $0.1\mathrm{keV}\text{ee}$. The observed rate in the detector at $0.5\mathrm{keV}\text{ee}$ is about $1.5\mathrm{event}/\mathrm{keV}\text{ee}/\mathrm{kg}/\mathrm{d}$ and is almost entirely accounted for by known background sources. We obtain a 90% C.L. exclusion limit above $1.8\mathrm{GeV}/c^2$ for the spin-independent cross section of dark matter WIMPs on nucleons, extending the exclusion region for dark matter below previous limits in the range $1.8–6\mathrm{GeV}/c^2$.

We present new constraints on sub-GeV dark-matter particles scattering off electrons based on 6780.0 kg d of data collected with the DarkSide-50 dual-phase argon time projection chamber. This analysis uses electroluminescence signals due to ionized electrons extracted from the liquid argon target. The detector has a very high trigger probability for these signals, allowing for an analysis threshold of three extracted electrons, or approximately 0.05 keVee. We calculate the expected recoil spectra for dark matter-electron scattering in argon and, under the assumption of momentum-independent scattering, improve upon existing limits from XENON10 for dark-matter particles with masses between 30 and $100\mathrm{MeV}/c^2$.

The DarkSide-50 direct-detection dark matter experiment is a dual-phase argon time projection chamber operating at Laboratori Nazionali del Gran Sasso. This paper reports on the blind analysis of a $(16660\pm 270)\mathrm{kg}\mathrm{d}$ exposure using a target of low-radioactivity argon extracted from underground sources. We find no events in the dark matter selection box and set a 90% C.L. upper limit on the dark matter–nucleon spin-independent cross section of $1.14\times {10}^{-44}{\mathrm{cm}}^2$ ($3.78\times {10}^{-44}{\mathrm{cm}}^2$, $3.43\times {10}^{-43}{\mathrm{cm}}^2$) for a WIMP mass of $100\mathrm{GeV}/c^2$ ($1\mathrm{TeV}/c^2$, $10\mathrm{TeV}/c^2$).