World's Largest Particle Research Articles

Enabling Large Scale Simulations for Particle Accelerators

International high-energy particle physics research centers, like CERN and Fermilab, require excessive studies and simulations to plan for the upcoming upgrades of the world's largest particle accelerators, and the design of future machines given the technological challenges and tight budgetary constraints. The Beam Longitudinal Dynamics (BLonD) simulator suite incorporates the most detailed and complex physics phenomena in the field of longitudinal beam dynamics, required for providing extremely accurate predictions. Modern challenges in beam dynamics dictate for longer, larger and numerous simulation studies to draw meaningful conclusions that will drive the baseline choices for the daily operation of current machines and the design choices of future projects. These studies are extremely time consuming, and would be impractical to perform without a High-Performance Computing oriented simulator framework. In this article, at first, we design and evaluate a highly-optimized distributed version of BLonD. We combine approximate computing techniques, and leverage a dynamic load-balancing scheme to relax synchronization and improve scalability. In addition, we employ GPUs to accelerate the distributed implementation. We evaluate the highly optimized distributed beam longitudinal dynamics simulator in a supercomputing system and demonstrate speedups of more than two orders of magnitude when run on 32 GPU platforms, w.r.t. the previous state-of-art. By driving a wide range of new studies, the proposed high performance beam longitudinal dynamics simulator forms an invaluable tool for accelerator physicists.

Tunnel Visions: The Rise and Fall of the Superconducting Super Collider

Tunnel Visions is a detailed and engaging account of the development of the superconducting supercollider, one of the largest scientific undertakings in the United States during its century of “big science,” from the origin of the supercollider in 1987 to its eventual abandonment in 1993. The initial goal was to build the world's largest particle accelerator to produce controlled, extraordinarily high-energy electron and proton collisions. Physicists anticipated these collisions would yield data on the nature of the Higgs boson elementary particle and other nuclear phenomena occurring only at high-energy levels. Such information was critical to complete the “standard model” of particle physics, which directed the field for much of the twentieth century. Tunnel Visions is such a valuable piece of scholarship because its authors have exhaustively mined archival data, consulted scientific publications, explored government documents, and conducted hundreds of interviews to produce a rich and multilayered depiction of the supercollider's history. One of this country's costliest scientific adventures, it was proposed by the particle physics community, arguing that its construction would enable the United States to reclaim leadership in the field. Capturing the attention of administrators in the Ronald Reagan White House, who were still obsessed with Cold War scientific adventures such as the Strategic Defense Initiative (also known as Star Wars), physicists convinced President Reagan of the project's utility; he urged its construction in 1987. The supercollider was projected to cost between $2.5 and $3 billion—a price that placed it among several billion-dollar scientific megaprojects favored by Reagan. Unfortunately, the American economy slowed dramatically, federal deficits emerged, and Congress reacted. Consequently, when costs escalated to $6 billion, then to $8 billion, and finally to an anticipated $10 billion, congressional leaders lost their enthusiasm for the project, and it was terminated in 1993. By then, $2 billion had been spent; another $640 million was budgeted to shut the project down.

Data Acquisition at CERN: A Future Challenge

How did the universe look in the first moments after the Big Bang? Why does matter dominate over antimatter? What are the fundamental particles that make up the world as we see it today? To find answers to those and similar questions, the European Organization for Nuclear Research (CERN) is operating the world's largest particle accelerator, the Large Hadron Collider (LHC). The LHC accelerates protons to a velocity close to the speed of light and makes hundreds of them collide. The circumstances shortly after those collisions are representative to the universe's conditions only moments after the Big Bang. By analyzing thousands of such collisions, a steps can be made toward answering the previous questions.

Iris ID completes installation at CERN physics lab

Iris ID, provider of iris biometric technology, has installed its iris recognition solution at CERN, the European research organisation operating the world's largest particle physics laboratory near Geneva, Switzerland. This comes as debate rages among researchers about the effect of the passage of time on the recognition of individuals based on the analysis of their iris characteristics after a NIST report found no evidence of iris ageing.

A method to simulate the observed surface properties of proton irradiated silicon strip sensors

During the scheduled high luminosity upgrade of the LHC, the world's largest particle physics accelerator at CERN, the position sensitive silicon detectors installed in the vertex and tracking part of the CMS experiment will face a more intense radiation environment than the present system was designed for. To upgrade the tracker to the required performance level, extensive measurements and simulation studies have already been carried out. A defect model for the bulk properties of proton irradiated silicon has been created with the Synopsys Sentaurus TCAD simulation package which produces simulated results that closely match the measured properties of silicon strip detectors. However, the expected behaviour due to increased surface damage is not so well predicted by the model. The solution requires an approach that does not affect the accurate bulk properties produced by the proton model, but only adds to it the required radiation induced properties close to the surface. These include the observed position dependence of the strip detector's charge collection efficiency (CCE). In this paper a procedure to find a defect model that reproduces the correct CCE loss, along with other surface properties of a strip detector up to a fluence 1.5×1015 1 MeV neq cm−2 (Φeq), will be presented. When applied to CCE loss measurements at different fluences, this method may provide a means for the parametrization of the accumulation of oxide charge at the SiO2/Si interface as a function of dose.

Charge collection efficiency simulations of irradiated silicon strip detectors

During the scheduled high luminosity upgrade of LHC, the world's largest particle physics accelerator at CERN, the position sensitive silicon detectors installed in the vertex and tracking part of the CMS experiment will face a more intense radiation environment than the present system was designed for. Thus, to upgrade the tracker to the required performance level, comprehensive measurements and simulation studies have already been carried out.Essential information of the performance of an irradiated silicon detector is obtained by monitoring its charge collection efficiency (CCE). From the evolution of CCE with fluence, it is possible to directly observe the effect of the radiation induced defects on the ability of thedetector to collect charge carriers generated by traversing minimum ionizing particles (MIPs).In this paper the numerically simulated CCE and CCE loss between the strips of irradiated silicon strip detectors are presented. The simulations based on the Synopsys Sentaurus TCAD framework were performed before and after irradiation for fluences up to 1.5 × 1015 neqcm−2 for n-on-p sensors. A two level defect model and non-uniform three level defect model were applied for the proton irradiation simulations, and a two levelmodel for neutrons. The results are presented together with the measurements of strip detectorsirradiated by different particles and fluences and show considerable agreement for both CCE and its position dependency.

The Nuclear Heart of Europe

CERN, the organisation that runs the world's largest particle physics laboratory, turned 60 last month. Its efforts to unravel the mysteries of the universe are well documented, but the pioneering role of the engineers and computer scientists supporting the physics is sometimes overlooked.

Track-based alignment of the ATLAS Inner Detector: implementation and performance

The Large Hadron Collider (LHC) at CERN is the world's largest particle accelerator. It collides proton beams at unprecedented centre-of-mass energies. ATLAS is a multipurpose experiment that records the products of the LHC collisions. In order to reconstruct the trajectories of charged particles produced in these collisions, ATLAS is equipped with a precision tracking system, the Inner Detector (ID). The ID alignment procedure ensures an accurate determination of the position and orientation of the detector's sensors, such that detector mis-alignments do not degrade the physics performance. An outline of the track-based alignment approaches, their implementation within the ATLAS software framework and the resulting performance is presented.

WatchMan project—A Python CASE framework for High Energy Physics data analysis in the LHC era

The world's largest particle collider LHC is taking data at CERN, in Geneva, providing a huge amount of data to be looked at, of the order of several Petabytes per year. Nowadays, Data Analysis in High Energy Physics (HEP) means handling billions of experimental data in custom software frameworks. Physicists have to access and select data interacting with the experiment using dedicated tools; they also have to apply filter functions and analysis algorithms to test hypotheses about the physics underlain. Modern HEP experiments rely on complex software frameworks, hence writing the analysis code is not always an easy task, and the learning curve is usually quite steep. Moreover each hypothesis requires a dedicated analysis, in order to have a better control on it and to be able to validate the results among different groups of researchers. And the writing of so many analyses can be error prone and time consuming.In order to ease the writing of such data analysis code, we built a software-generator: the idea is that the user inserts the settings of the physics analyses, and the final analysis code is automatically and dynamically generated, ready to be run on data. Python helped us to build such a package. Its high-level and dynamic nature, together with its flexibility and prototyping speed are the key features which made our choice.So we conceived and developed WatchMan, a Python CASE (Computer-Aided Software Engineering) framework to automatically generate reliable, easy to maintain and easy to validate HEP data analysis code.

Science Podcast

The show includes a planet orbiting two stars, the depths of Earth's carbon cycle, life at the world's largest particle accelerator, and more.

First results of the LHC longitudinal density monitor

Abstract The Large Hadron Collider (LHC) at CERN is the world's largest particle accelerator. It is designed to accelerate and collide protons or heavy ions up to the center-of-mass energies of 14 TeV. Knowledge of the longitudinal distribution of particles is important for various aspects of accelerator operation, in particular to check the injection quality and to measure the proportion of charge outside the nominally filled bunches during the physics periods. In order to study this so-called ghost charge at levels very much smaller than the main bunches, a longitudinal profile measurement with a very high dynamic range is needed. A new detector, the LHC Longitudinal Density Monitor (LDM) is a single-photon counting system measuring synchrotron light by means of an avalanche photodiode detector. The unprecedented energies reached in the LHC allow synchrotron light diagnostics to be used with both protons and heavy ions. A prototype was installed during the 2010 LHC run and was able to longitudinally profile the whole ring with a resolution close to the target of 50 ps. On-line correction for the effects of the detector deadtime, pile-up and afterpulsing allow a dynamic range of 10 5 to be achieved. First measurements with the LDM are presented here along with an analysis of its performance and an outlook for future upgrades.

Particle physics: Inside the collider

Joseph Silk enjoys an eloquent take on the Higgs boson, supersymmetry and the world's largest particle smasher.

Alignment of the ATLAS inner detector tracking system

The Large Hadron Collider (LHC) at CERN is the world's largest particle accelerator. ATLAS is one of the two general purpose experiments. The inner tracking system of ATLAS, the Inner Detector, is built on two technologies: silicon detectors and drift tube based detectors. The required precision for the alignment of the most sensitive coordinates of the Silicon sensors is just a few microns. Therefore the alignment of the ATLAS Inner Detector is performed using complex algorithms requiring extensive CPU and memory usage. The proposed alignment algorithms were exercised on several applications. This proceedings present the outline of the alignment approach and results from Cosmic Ray runs and large scale computing simulation of physics samples mimicking the ATLAS operation during real data-taking. The full alignment chain was tested using these samples and alignment constants were produced and validated within 24 hours. Early alignment of the ATLAS Inner Detector is provided even before the LHC start up by analysing Cosmic Ray data.

LHC sees particles circulate once more

Proton beams are zipping around the world's largest particle collider after more than a year of repairs.

AD—A Laboratory for Low Energy Antiproton Physics

The Anti-proton Decelerator AD is embedded in the accelerator complex of CERN, the international scientific organization established for the purpose of collaborative research founded in 1952 as: Conseil Européen pour la Recherche Nucléaire (CERN) and operated since 1954 as: European Organization for Nuclear Research (Organisation Européenne pour la Recherche Nucléaire). CERN is located near Geneva and hosts the world's largest particle physics laboratory. Besides the main research focus of experiments at the large hadron collider LHC, a variety of other topics are covered, like low energy anti-proton physics.

LHC students face data drought

Computer simulations are the only option when the world's largest particle accelerator isn't working.

An Extreme Processor for an Extreme Experiment

Particle physics experiments stretch processing requirements to the limit, requiring the selection of extremely rare events at tens of terabytes per second. A network of 283,392 mixed-signal MIMD processors operating in parallel at 17 tbytes/s help physicists interpret data from the world's largest particle accelerator. Particle physics and heavy-ion experiments demand greater integration and fast on-detector signal processing. We believe TRD is the first system to implement complete signal digitizing, filtering, intelligent trigger processing and readout in a single on-detector chip that avoids system noise. TRD uses multiport memories as register file inputs, multiported GRFs, and a global multiport data memory. These components support high-end multiprocessing requirements under tight latency conditions. Multi-ported memories, in particular, make it possible to couple independent data streams' very efficiently. So far, the requirements for this detector have remained largely stable. The main change was to add digital filters relatively late in the design. Of course, the first weeks of measuring actual collisions at unprecedented LHC energies are the true test of our design

Precision robot welding for world's largest particle physics apparatus

Precision robot welding for world's largest particle physics apparatus

Contextualized magnetism in secondary school: learning from the LHC (CERN)

Physics teachers in secondary schools usually mention the world's largest particle physics laboratory—CERN (European Organization for Nuclear Research)—only because of the enormous size of the accelerators and detectors used there, the number of scientists involved in their activities and also the necessary international scientific collaboration. Impressive pictures of the accelerators and detectors are also shown. This is correct but clearly incomplete since there are other didactic possibilities to explore while talking about one of the most important scientific institutions in the world. The aim of this article is to introduce a few simple physical calculations about some magnetic phenomena that took place in old accelerators and will be present when the LHC (Large Hadron Collider) starts working in 2007. They can be used in the classroom in order to stimulate the curiosity of students, to help them to understand those physical concepts, and as an example of the relationship between the 'cold equations' of physics on the blackboard and the exciting work in scientific research.

Precision robot welding for world's largest particle physics apparatus

Precision robot welding for world's largest particle physics apparatus