Major Physics Experiments Research Articles

DIRC: Internally reflecting imaging Cherenkov detectors

In this article we review a distinctive type of Cherenkov ring imaging device generically called a DIRC detector. DIRC is an acronym for “Detection of Internally Reflected Cherenkov (Light)”. We briefly discuss how these devices were first motivated and conceived, describe their basic operating principles, their early prototypes, and fabrication R&D. We then describe the BaBar DIRC at SLAC, as the first full scale implementation of this detector type for a major physics experiment. Further R&D at SLAC that was motivated to enable operations at the very high rates of SuperB factories led to the Focusing DIRC concept and prototype that will next be described. We then review a wide range of further developments now underway using variants on the DIRC theme, including the TOP counter at Belle-II; a number of FDIRC designs for GLUEX, PANDA barrel and endcap; and the LHCb TORCH.

The upgrade programme of the major experiments at the Large Hadron Collider

After a successful data taking period at the CERN LHC by the major physics experiments (ALICE, ATLAS, CMS and LHCb) since 2009, a long-term plan is already envisaged to fully exploit the vast physics potential of the Large Hadron Collider (LHC) within the next two decades. The CERN accelerator complex will undergo a series of upgrades leading ultimately to increase both the collision energy and the luminosity, thus maximizing the amount of data delivered to all experiments. As a consequence, the experiments have also to cope with very high detector occupancies and operate in the hard radiation environment caused by a huge multiplicity of particles produced in each beam crossing. In parallel to the accelerator upgrades, the LHC experiments are planning various upgrades to their detector, trigger, and data acquisition systems. The main motivation for the upgrades is to extend and to improve their physics programme also in the increasingly challenging LHC environment. In this paper a general overview of the upgrade programme of the major experiments at LHC will be given, with some additional details concerning specifications and physics programme of new detector subsystems.

Resource-Aware Distributed Scheduling Strategies for Large-Scale Computational Cluster/Grid Systems

In this paper, we propose distributed algorithms referred to as resource-aware dynamic incremental scheduling (RADIS) strategies. Our strategies are specifically designed to handle large volumes of computationally intensive arbitrarily divisible loads submitted for processing at cluster/grid systems involving multiple sources and sinks (processing nodes). We consider a real-life scenario, wherein the buffer space (memory) available at the sinks (required for holding and processing the loads) varies over time, and the loads have deadlines and propose efficient "pull-based" scheduling strategies with an admission control policy that ensures that the admitted loads are processed, satisfying their deadline requirements. The design of our proposed strategies adopts the divisible load paradigm, referred to as the divisible load theory (DLT), which is shown to be efficient in handling large volume loads. We demonstrate detailed workings of the proposed algorithms via a simulation study by using real-life parameters obtained from a major physics experiment.

High-energy physics as a career springboard

As well as being crucibles of research, today's big physics experiments are alsofactories for students - in more than a decade almost 700 have graduated fromthe Delphi experiment (see appendix A for a description of the experiment and alist of the collaborating institutes) at CERN's LEP electron-positron collider.Personal skills are a valuable form of technology transfer. The expertiseacquired in the large international collaborations running today's major physicsexperiments is diverse - computing, electronics, project management and so on.In addition are the interpersonal skills acquired by being a member of a largeinternational team working on a complex problem. Today's physics students aremuch in demand. To see how this happens we have analysed the careers of thestudents involved in the experiment since its beginnings in 1982.The education systems are very diverse in the various countries. It has beentried to broadly group the degrees into two main types: doctoral studies andlower-ranking degrees (diploma like and master like). Some countries do not havea master programme, some like France have essentially only doctoral programmesfor physics studies and possibly lower level education for engineers. Othercountries like Italy or Germany have degrees such as the `Laurea' or `Diploma'that can comprise thesis work of widely different levels and depth.The reach of this study is limited given that, typically, it is possible tofollow up people employment only for the first job after the completion of auniversity degree. In particular, it gives only a lower limit estimate on thenumber of people who end up having a career in the private sector as in manycases a doctoral student gets a temporary (typically for two years)post-doctoral grant as first employment. For a subset of students it has beenpossible to follow up past the first temporary research employment: this limitedstatistic will be used to estimate the number of people who will eventually endup in the private sector after their research post-doctoral experience.We have examined the general trends for all the students independent of the typeof degree obtained and we have also looked in detail into the careers ofdoctoral students.We have analysed separately the trends for women.

Large and small data acquisition systems at JET

Both large and small data acquisition systems have applications in a major physics experiment such as JET. This paper describes the central acquisition and trigger system (CATS) which provides co-ordinated high speed data acquisition for many diagnostics, and also describes the integration into the JET infrastructure of much smaller systems which use commercial PC based acquisition hardware and software. Such PC systems benefit from lower cost and shorter development time compared to embedded bus-based systems.