We report the observation of Higgs boson decays to WW Ã based on an excess over background of 6.1 standard deviations in the dilepton final state, where the Standard Model expectation is 5.8 standard deviations. Evidence for the vector-boson fusion (VBF) production process is obtained with a significance of 3.2 standard deviations. The results are obtained from a data sample corresponding to an integrated luminosity of 25 fb −1 from ffiffi ffi s p ¼ 7 and 8 TeV pp collisions recorded by the ATLAS detector at the LHC. For a Higgs boson mass of 125.36 GeV, the ratio of the measured value to the expected value of the total production cross section times branching fraction is 1.09 þ0.

The Versatile Link is a bi-directional digital optical data link operating at rates up to 4.8 Gbit/s and featuring radiation-resistant low-power and low-mass front-end components. The system is being developed in multimode or singlemode versions operating at 850 nm or 1310 nm wavelength respectively. It has serial data interfaces and is protocol-agnostic, but is targeted to operate in tandem with the GigaBit Transceiver (GBT) serializer/deserializer chip being designed at CERN. This paper gives an overview of the project status three and a half years after its launch. It describes the challenges encountered and highlights the solutions proposed at the system as well as the component level. It concludes with a positive feasibility assesment and an outlook for future project development directions.

A proton pencil beam is associated with a surrounding low-dose envelope, originating from nuclear interactions. It is important for treatment planning systems to accurately model this envelope when performing dose calculations for pencil beam scanning treatments, and Monte Carlo (MC) codes are commonly used for this purpose. This work aims to validate the nuclear models employed by the Geant4 MC code, by comparing the simulated absolute dose distribution to a recent experiment of a 177 MeV proton pencil beam stopping in water. Striking agreement is observed over five orders of magnitude, with both the shape and normalisation well modelled. The normalisations of two depth dose curves are lower than experiment, though this could be explained by an experimental positioning error. The Geant4 neutron production model is also verified in the distal region. The entrance dose is poorly modelled, suggesting an unaccounted upstream source of low-energy protons. Recommendations are given for a follow-up experiment which could resolve these issues.

The radiation induced attenuation of optical fibres below −20°C exposed to lifetime HL-LHC doses at a dose rate of 700 Gy(Si)/hrTo cite this article: D Hall et al 2012 JINST 7 C01047 View the article online for updates and enhancements. Related contentThe radiation hardness of specific multimode and single-mode optical fibres at -25°C beyond a full SLHC dose to a dose of 500 kGy(Si) B T Huffman, C Issever, N C Ryder et al. -The radiation tolerance of MTP and LC optical fibre connectors to 500 kGy(Si) of gamma radiation D C Hall, P Hamilton, B T Huffman et al. ABSTRACT: The LHC luminosity upgrade, known as the HL-LHC, will require high-speed optical links to read out data from the detectors. Such links must be capable of withstanding high doses whilst being kept at low temperatures. Two single-mode and two multi-mode fibres were exposed to 200 kGy(Si) at a dose rate of about 700 Gy(Si)/hr, whilst being kept at about -25 • C. The radiation induced attenuation of these fibres was measured as the fibres accumulated dose. A conservative estimate has been made of the total attenuation expected for a realistic fibre route through the ATLAS detector after a lifetime dose at the HL-LHC. With safety factors, the maximum dose extrapolated to was 375 kGy(Si). All four fibres performed extremely well and were qualified for use at HL-LHC detectors.