ar X iv : h ep - p h / 04 12 13 9 v 1 1 0 D ec 2 00 4 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 HEP-DATA database of HEP data and the innovative JetWeb data/Monte Carlo comparison facility, built on the HZ-TOOL 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. Particle physics experiments at high-energy accelerators provide a wealth of data on the final state in electron-positron, lepton-proton and proton-(anti)proton interactions. These data represent a triumph for the Standard Model, particularly in precision electroweak measurements and the verification of the QCD sector to an impressive degree of precision. Despite these successes, several aspects of high-energy collisions are still poorly understood, often due to technical difficulties in the calculation of non-perturbative or complex perturbative effects. Such lack of understanding can be a limiting factor in the accuracy of new measurements. Examples with particular relevance to the LHC include par-ton distribution functions (PDFs) in hadrons, hadronisa-tion in the final state, multijet production and " underlying events ". Fig. 1 illustrates some of these processes in a complex high energy event. All these processes are calculated and/or modelled in Monte Carlo simulation and calculation programs that employ fits to existing data. Consistent tuning of the free parameters of these models, and confirmation of the physics assumptions they contain, is a non-trivial matter since the measurements are made with a variety of colliding beams, in many different regions of phase space, and for many complex observables. Figure 1: The complexity of a collision process. A solution to the above problem will be provided by CEDAR, a project newly funded by the PPARC e-Science programme in the UK, …