Sudakov Logarithm Resummation for Vector Boson Production at Hadron Colliders

A complete description of W and Z boson production at high-energy colliders requires the resummation of large Sudakov logarithms which dominate the production at small transverse momentum. Currently there are two techniques for performing this resummation: impact parameter space and transverse momentum space. We argue that the latter can be formulated in a way which retains the advantages of the former, while at the same time allowing a smooth transition to finite order dominance at high transverse momentum.Comment: 5 pages, LaTeX, 2 figures, epsfig, contribution to the proceedings of the UK Phenomenology Workshop on Collider Physics, 19-24 September 1999, Durham, to be published in J. Phys.

The CEDAR Project

We describe the plans and objectives of the CEDAR project (Combined e-Science Data Analysis Resource for High Energy Physics) newly funded by the PPARC e-Science programme in the UK. CEDAR will combine the strengths of the well established and widely used HEPDATA database of HEP data and the innovative JetWeb data/Monte Carlo comparison facility, built on the HZTOOL package, and will exploit developing grid technology. The current status and future plans of both of these individual sub-projects within the CEDAR framework are described, showing how they will cohesively provide (a) an extensive archive of Reaction Data, (b) validation and tuning of Monte Carlo programs against these reaction data sets, and (c) a validated code repository for a wide range of HEP code such as parton distribution functions and other calculation codes used by particle physicists. Once established it is envisaged CEDAR will become an important Grid tool used by LHC experimentalists in their analyses and may well serve as a model in other branches of science where there is a need to compare data and complex simulations.Comment: 4 pages, 4 postscript figures, uses CHEP2004.cls. Presented at Computing in High-Energy Physics (CHEP'04), Interlaken, Switzerland, 27th September - 1st October 200

HepForge: A lightweight development environment for HEP software

Setting up the infrastructure to manage a software project can become a task as significant writing the software itself. A variety of useful open source tools are available, such as Web-based viewers for version control systems, "wikis" for collaborative discussions and bug-tracking systems, but their use in high-energy physics, outside large collaborations, is insubstantial. Understandably, physicists would rather do physics than configure project management tools. We introduce the CEDAR HepForge system, which provides a lightweight development environment for HEP software. Services available as part of HepForge include the above-mentioned tools as well as mailing lists, shell accounts, archiving of releases and low-maintenance Web space. HepForge also exists to promote best-practice software development methods and to provide a central repository for re-usable HEP software and phenomenology codes.Comment: 3 pages, 0 figures. To be published in proceedings of CHEP06. Refers to the HepForge facility at http://hepforge.cedar.ac.u

HepData and JetWeb: HEP data archiving and model validation

The CEDAR collaboration is extending and combining the JetWeb and HepData systems to provide a single service for tuning and validating models of high-energy physics processes. The centrepiece of this activity is the fitting by JetWeb of observables computed from Monte Carlo event generator events against their experimentally determined distributions, as stored in HepData. Caching the results of the JetWeb simulation and comparison stages provides a single cumulative database of event generator tunings, fitted against a wide range of experimental quantities. An important feature of this integration is a family of XML data formats, called HepML.Comment: 4 pages, 0 figures. To be published in proceedings of CHEP0

Topology of Hadronic Flows for Higgs Production at Hadron Colliders

Hadronic radiation provides a tool to distinguish different topologies of colour flow in hard scattering processes. We study the structure of hadronic flow corresponding to Higgs production and decay in high-energy hadron-hadron collisions. In particular, the signal gg -> H -> b anti-b and background gg -> b anti-b processes are shown to have very different radiation patterns, and this may provide an useful additional method for distinguishing Higgs signal events from the QCD background.Comment: 24 pages, 13 figures, uses epsfig.sty. High resolution pictures may be obtained via email from [email protected]

Contrasts in stream water chemistry impact aquatic ecosystem functioning in an agricultural landscape

Given the importance of freshwater ecosystems to human health and wellbeing, the resilience of aquatic communities to pollution from a variety of sources is of increasing concern. Current indices concentrate on structural measures to define stream health. These include community assemblages, in-stream water chemistry, and hydrological impairment through physical modifications. However, ecosystem services provided by freshwater communities rely on the underlying biogeochemical cycles that are a function of metabolic processes. At present, these are not routinely used in assessments of ecological status. A paired sub-catchment approach was used to study the effects of different land management practices on in-stream water chemistry, and their consequences to aquatic functional integrity in an agricultural landscape. The study provided an opportunity to assess the potential for ecosystem functional measures to complement the structural measures that are used to define impact on aquatic communities. High resolution analysis of the nutrient chemistry within two study reaches underpinned comparisons of community aerobic respiration, greenhouse gas transfer across the sediment-water interface and macro-invertebrate mediated processing of organic matter. This programme of measures identified clear differences between the study sub-catchments. It revealed that the management of animal waste, and control on the delivery of fine sediments to a watercourse, were key influences on in-stream functional integrity. The delivery of inorganic nutrients as a result of fertiliser application was also evident. However, the significance of this signal was masked by the overriding effect of high loads of organically loaded fine sediments and low flow in the Priors Farm reach