The Joint COntrols Project Framework

The Framework is one of the subprojects of the Joint COntrols Project (JCOP), which is collaboration between the four LHC experiments and CERN. By sharing development, this will reduce the overall effort required to build and maintain the experiment control systems. As such, the main aim of the Framework is to deliver a common set of software components, tools and guidelines that can be used by the four LHC experiments to build their control systems. Although commercial components are used wherever possible, further added value is obtained by customisation for HEP-specific applications. The supervisory layer of the Framework is based on the SCADA tool PVSS, which was selected after a detailed evaluation. This is integrated with the front-end layer via both OPC (OLE for Process Control), an industrial standard, and the CERN-developed DIM (Distributed Information Management System) protocol. Several components are already in production and being used by running fixed-target experiments at CERN as well as for the LHC experiment test beams. The paper will give an overview of the key concepts behind the project as well as the state of the current development and future plans.Comment: Paper from the 2003 Computing in High Energy and Nuclear Physics (CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, PDF. PSN THGT00

Techniques for n-Particle Irreducible Effective Theories

In this paper we show that the skeleton diagrams in the m-Loop nPI effective action correspond to an infinite resummation of perturbative diagrams which is void of double counting at the m-Loop level. We also show that the variational equations of motion produced by the n-Loop nPI effective theory are equivalent to the Schwinger-Dyson equations, up to the order at which they are consistent with the underlying symmetries of the original theory. We use a diagrammatic technique to obtain the 5-Loop 5PI effective action for a scalar theory with cubic and quartic interactions, and verify that the result satisfies these two statements.Comment: 43 pages, 48 figures, add a paragraph in conclusions, Figs. 25,45,46 changed, typos corrected, final version to appear in PR

Universal self-similar scaling of spatial Wilson loops out of equilibrium

We investigate strongly correlated non-Abelian plasmas out of equilibrium. Based on numerical simulations, we establish a self-similar scaling property for the time evolution of spatial Wilson loops that characterizes a universal state of matter far from equilibrium. Most remarkably, it exhibits a generalized area law which holds for sufficiently large ratio of spatial area and fractional power of time. Performing calculations also for the perturbative regime at higher momenta, we are able to characterize the full nonthermal scaling properties of SU(2) and SU(3) symmetric plasmas from short to large distance scales in terms of two independent universal exponents and associated scaling functions.Comment: 5 pages, 4 figures, PRL version (minor text changes

Critical phenomena from the two-particle irreducible 1/N expansion

The 1/N expansion of the two-particle irreducible (2PI) effective action is employed to compute universal properties at the second-order phase transition of an O(N)-symmetric N-vector model directly in three dimensions. At next-to-leading order the approach cures the spurious small-N divergence of the standard (1PI) 1/N expansion for a computation of the critical anomalous dimension eta(N), and leads to improved estimates already for moderate values of N.Comment: 18 pages, 3 figure

The high-performance database archiver for the LHC experiments

Each of the Large Hadron Collider (LHC) experiments will be controlled by a large distributed system built with the Supervisory Control and Data Acquisition (SCADA) tool Prozeßvisualisierungs- und Steuerungsystem (PVSS). There will be in the order of 150 computers and one million input/output parameters per experiment. The values read from the hardware, the alarms generated and the user actions will be archived for the later physics analysis, the operation and the debugging of the control system itself. Although the original PVSS implementation of a database archiver was appropriate for standard industrial use, the performance was not sufficient for the experiments. A collaboration was setup between CERN and ETM, the company that develops PVSS. Changes in the architecture and several optimizations were made and tested in a system of a comparable size to the final ones. As a result, we have been able to improve the performance by more than one order of magnitude, and what is more important, we now have a scalable architecture based on the Oracle clustering technology (Real Application Cluster, RAC). This architecture can deal with the requirements for insertion rate, data querying and manageability of the high volume of data, e.g. an insertion rate of > 150,000 changes/s was achieved with a 6 node RAC cluster

QED Electrical Conductivity using the 2PI Effective Action

In this article we calculate the electrical conductivity in QED using the 2PI effective action. We use a modified version of the usual 2PI effective action which is defined with respect to self-consistent solutions of the 2-point functions. We show that the green functions obtained from this modified effective action satisfy ward identities and that the conductivity obtained from the kubo relation is gauge invariant. We work to 3-loop order in the modified 2PI effective action and show explicitly that the resulting expression for the conductivity contains the square of the amplitude that corresponds to all binary collision and production processes.Comment: 24 pages, 21 figure

Passive acoustic quantification of gas releases

The assessment of undersea gas leakages from anthropogenic and natural sources is becoming increasingly important. This includes the detection of gas leaks and the quantification of gas flux. This has applications within oceanography (e.g. natural methane seeps) and the oil and gas industry (e.g. leaks from undersea gas pipelines, carbon capture and storage facilities). Gas escaping underwater can result in the formation of gas bubbles, and this leads to specific acoustic pressure fluctuations (sound) which can be analysed using passive acoustic systems. Such a technique offers the advantage of lower electrical power requirements for long term monitoring. It is common practice for researchers to identify single bubble injection events from time histories or time frequency representations of hydrophone data, and infer bubble sizes from the centre frequency of the emission. Such a technique is well suited for gas releases that represent low flow rates, and involving solitary bubble release. However, for larger events, with the overlapping of bubble acoustic emissions, the inability to discriminate each individual bubble injection event makes this approach inappropriate. In this study, an inverse method to quantify such release is used. The model is first outlined and following this its accuracy at different flow rate regimes is tested against experimental data collected from tests which took place in a large water tank. The direct measurements are compared to estimates inferred from acoustics.<br/

Next-to-Leading Order Transport Coefficients from the Four-Particle Irreducible Effective Action

Transport coefficients can be obtained from 2-point correlators using the Kubo formulae. It has been shown that the full leading order result for electrical conductivity and (QCD) shear viscosity is contained in the re-summed 2-point function that is obtained from the 3-loop 3PI re-summed effective action. The theory produces all leading order contributions without the necessity for power counting, and in this sense it provides a natural framework for the calculation. In this article we study the 4-loop 4PI effective action for a scalar theory with cubic and quartic interactions in the presence of spontaneous symmetry breaking. We obtain a set of integral equations that determine the re-summed 2-point vertex function. A next-to-leading order contribution to the viscosity could be obtained from this set of coupled equations.Comment: 24 pages, 18 figures. Added references and minor rewordings: published versio