ATLAS experiment

ATLAS experiment
Arpad Horvath · CC BY-SA 2.5 · source
Name	ATLAS experiment
Location	CERN
Established	1992
Type	Particle physics detector

ATLAS experiment

The ATLAS experiment is a general-purpose particle detector installed on the Large Hadron Collider ring at CERN, designed to investigate proton–proton collisions and explore phenomena predicted by the Standard Model (particle physics) and theories beyond it such as supersymmetry, extra dimensions and dark matter. The project involves an international collaboration of physicists and engineers from institutions including University of Oxford, Massachusetts Institute of Technology, University of Tokyo, INFN, and DESY, and operates alongside other detectors like CMS experiment, LHCb experiment and ALICE experiment. ATLAS has played a central role in discoveries linked to the Higgs boson and precision measurements that test frameworks such as Quantum Chromodynamics and electroweak theory as formulated by Glashow–Weinberg–Salam model.

Overview

ATLAS was proposed during the 1990s in the context of the Large Electron–Positron Collider shutdown and the construction of the Large Hadron Collider, with conceptual contributions from groups at Brookhaven National Laboratory, CERN, Fermilab, SLAC National Accelerator Laboratory and universities such as University of Cambridge and University of California, Berkeley. The detector is situated in the ATLAS cavern near Meyrin and was assembled using components produced at facilities including Rutherford Appleton Laboratory, KEK, Paul Scherrer Institute and TRIUMF. ATLAS records collision events delivered by the LHC and provides data used in analyses by collaborations affiliated with agencies like European Research Council, National Science Foundation, Science and Technology Facilities Council and national funding bodies in dozens of countries.

Detector design and subsystems

The ATLAS detector is a layered system comprising an inner tracking system, calorimeters, muon spectrometer and magnet systems developed with contributions from BNL, ENEA, CINECA and universities such as University of Manchester, University of Glasgow and Imperial College London. The inner detector combines pixel detectors and silicon microstrip trackers with a transition radiation tracker, integrating technologies advanced at CERN and KEK and employing sensors similar to those used at HERA and Tevatron. Electromagnetic calorimetry uses liquid-argon technology developed at laboratories like CEA Saclay and LAL (Laboratoire de l'Accélérateur Linéaire), while hadronic calorimetry incorporates tile calorimeters with production at University of Liverpool and Max Planck Institute for Physics. The muon spectrometer relies on precision chambers such as monitored drift tubes and resistive plate chambers produced by consortia including NIKHEF, CERN and University of Melbourne, all immersed in air-core toroidal magnets engineered with industrial partners and institute teams from Czech Technical University and Politecnico di Milano.

Data acquisition and computing

ATLAS employs a multi-tiered trigger system and data-acquisition chain designed to reduce event rates from the LHC bunch-crossing frequency to manageable storage volumes, with trigger development conducted by groups at University of Chicago, Princeton University, ETH Zurich and Uppsala University. The collaboration uses a worldwide distributed computing model coordinated through the Worldwide LHC Computing Grid with tiered centers including CERN Tier-0, national centers at TRIUMF, DESY Grid Computing Centre and regional facilities supported by NSF and European Grid Infrastructure. Software frameworks such as Athena, developed by teams from University of Oxford, LAL and INFN, integrate simulation tools like GEANT4 and reconstruction algorithms validated against test-beam campaigns at facilities such as CERN Proton Synchrotron and SPS (Super Proton Synchrotron). Data preservation and analysis pipelines involve collaborations with archives and initiatives including REANA and institutions such as Harvard University and University of Melbourne.

Physics program and key results

ATLAS’s physics program spans Higgs boson searches, measurements of top-quark properties, electroweak processes, searches for supersymmetric particles, exotic resonances and dark-matter signatures, with major results reported in conjunction with experiments like CMS experiment and theory groups at Institute for Advanced Study, CERN Theory Department and Perimeter Institute. The 2012 observation of a Higgs-like boson followed joint analyses and announcements involving CERN, Fabiola Gianotti as spokesperson and teams from University of Edinburgh and University of California, Santa Barbara, leading to precision studies of Higgs couplings, spin-parity and decay modes. ATLAS has published measurements of top quark pair production cross sections, rare processes such as Bs→μ+μ− in complement with LHCb experiment results, and limits on models including minimal supersymmetric standard model and Randall–Sundrum model (RS model), while contributing to searches for magnetic monopole signatures and long-lived particles. Results have been presented at forums such as the International Conference on High Energy Physics, Moriond, EPS-HEP and published in journals like Physical Review Letters and Journal of High Energy Physics.

Collaboration and organization

The ATLAS Collaboration comprises thousands of scientists, engineers and students from hundreds of institutions across Europe, the Americas, Asia and Oceania, coordinated through an organizational structure with an elected spokesperson, management board, collaboration board and working groups tied to detector subsystems and physics analysis, drawing on governance models similar to CMS experiment and other large-scale projects like International Thermonuclear Experimental Reactor consortia. Training and outreach include partnerships with universities such as University of Oxford, University of Tokyo, University of Melbourne and national laboratories like Fermilab and Brookhaven National Laboratory, while awards and recognition for collaboration members have involved prizes such as the Breakthrough Prize and honors associated with CERN and national academies. The collaboration plans upgrades for High-Luminosity Large Hadron Collider operation with technical coordination across institutions including KEK, INFN, CERN and industrial partners to extend sensitivity to rare processes and new physics.

Category:Particle physics experiments