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Abstract:

© 2018, The Author(s). A search is performed in the invariant mass spectrum of the B c + π + π − system for the excited B c + states B c (2 1 S 0 ) + and B c (2 3 S 1 ) + using a data sample of pp collisions collected by the LHCb experiment at the centre-of-mass energy of s=8 TeV, corresponding to an integrated luminosity of 2 fb −1 . No evidence is seen for either state. Upper limits on the ratios of the production cross-sections of the B c (2 1 S 0 ) + and B c (2 3 S 1 ) + states times the branching fractions of B c (2 1 S 0 ) + → B c + π + π − and B c (2 3 S 1 ) + → B c * + π + π − over the production cross-section of the B c + state are given as a function of their masses. They are found to be between 0.02 and 0.14 at 95% confidence level for B c (2 1 S 0 ) + and B c (2 3 S 1 ) + in the mass ranges [6830, 6890] MeV/c 2 and [6795, 6890] MeV/c 2 , respectively.[Figure not available: see fulltext.].

Abstract:

A search for B + → D s + K + K − decays is performed using pp collision data corresponding to an integrated luminosity of 4.8 fb −1 , collected at centre-of-mass energies of 7, 8 and 13 TeV with the LHCb experiment. A significant signal is observed for the first time and the branching fraction is determined to be ℬ(B+→Ds+K+K−)=(7.1±0.5±0.6±0.7)×10−6,where the first uncertainty is statistical, the second systematic and the third due to the uncertainty on the branching fraction of the normalisation mode B+→Ds+D¯0. A search is also performed for the pure annihilation decay B + → D s + ϕ. No significant signal is observed and a limit of ℬ(B+→Ds+ϕ) < 4.9×10−7(4.2×10−7) is set on the branching fraction at 95% (90%) confidence level.[Figure not available: see fulltext.].

Abstract:

<p><strong>Abstract.</strong> It is hypothesized that more accurate prediction and warning of natural hazards, such as of the impacts of severe weather mediated through various components of the environment, require a more integrated Earth System approach to forecasting. This hypothesis can be explored using regional coupled prediction systems, in which the known interactions and feedbacks between different physical and biogeochemical components of the environment across sky, sea and land can be simulated. Such systems are becoming increasingly common research tools. This paper describes the development of the UKC2 regional coupled research system, which has been delivered under the UK Environmental Prediction Prototype project. This provides the first implementation of an atmosphere–land–ocean–wave modelling system focussed on the United Kingdom and surrounding seas at km-scale resolution. The UKC2 coupled system incorporates models of the atmosphere (Met Office Unified Model), land surface with river routing (JULES), shelf-sea ocean (NEMO) and ocean waves (WAVEWATCH III). These components are coupled, via OASIS3-MCT libraries, at unprecedentedly high resolution across the UK within a north-western European regional domain. A research framework has been established to explore the representation of feedback processes in coupled and uncoupled modes, providing a new research tool for UK environmental science. This paper documents the technical design and implementation of UKC2, along with the associated evaluation framework. An analysis of new results comparing the output of the coupled UKC2 system with relevant forced control simulations for six contrasting case studies of 5-day duration is presented. Results demonstrate that performance can be achieved with the UKC2 system that is at least comparable to its component control simulations. For some cases, improvements in air temperature, sea surface temperature, wind speed, significant wave height and mean wave period highlight the potential benefits of coupling between environmental model components. Results also illustrate that the coupling itself is not sufficient to address all known model issues. Priorities for future development of the UK Environmental Prediction framework and component systems are discussed.</p>