ATLAS detector

ATLAS detector. It is one of the two general-purpose particle detectors at the Large Hadron Collider at CERN. The detector is designed to explore a wide range of fundamental physics, from the search for the Higgs boson to investigations of dark matter and extra dimensions. Its immense size and complexity allow it to record the outcomes of proton-proton collisions at unprecedented energies.

Overview

The ATLAS detector is a monumental apparatus situated 100 meters underground at Point 1 of the Large Hadron Collider ring near Meyrin. As a central component of the ATLAS experiment, it is a collaboration involving thousands of scientists from hundreds of institutions worldwide, including University of Oxford, Lawrence Berkeley National Laboratory, and the Weizmann Institute of Science. Its primary function is to detect and measure the myriad particles produced in high-energy collisions, providing data to test predictions of the Standard Model and probe for new physics beyond it. The detector's cylindrical design, weighing approximately 7,000 tonnes, surrounds the collision point to capture particles flying in all directions.

Design and construction

The design phase of the detector began in the early 1990s, following the approval of the Large Hadron Collider project by the CERN Council. Key design challenges included creating a detector capable of withstanding intense radiation, managing enormous data rates, and achieving precise measurement across a vast volume. The construction was a global effort, with components built by institutes across the United States, Japan, Russia, and European Union member states before being assembled in the cavern. Innovative engineering solutions were required, such as the enormous barrel toroid magnet system, one of the largest superconducting magnets ever built. Final assembly and commissioning were completed in 2008, just before the Large Hadron Collider started operations.

Subdetector systems

The detector employs a layered, onion-like structure of specialized subdetectors, each tasked with identifying different particle properties. The innermost layer is the Inner Detector, which tracks charged particle trajectories within a 2 tesla magnetic field provided by a solenoid magnet. It comprises silicon-based technologies like the Pixel Detector and the Semiconductor Tracker. Surrounding this is the calorimeter system, which includes the Liquid Argon Calorimeter for precise electromagnetic measurements and a Tile Calorimeter for measuring hadronic energy. The outermost muon system, incorporating Monitored Drift Tubes and Resistive Plate Chambers, identifies muons, which penetrate the inner layers. This integrated system allows for the reconstruction of collision events with high fidelity.

Physics goals and discoveries

The overarching physics program is to explore the fundamental forces and constituents of the universe. A primary goal was the discovery of the Higgs boson, the particle associated with the Brout-Englert-Higgs mechanism, which was achieved jointly with the CMS experiment in 2012, leading to the Nobel Prize in Physics for François Englert and Peter Higgs. Ongoing searches include those for candidates of dark matter, such as Weakly Interacting Massive Particles, and for signs of supersymmetry. The detector also studies the properties of the top quark, investigates quark-gluon plasma in heavy-ion collisions, and searches for evidence of leptoquarks or grand unification theory.

Operation and upgrades

Since the start of Large Hadron Collider operations, the detector has collected data during its Run 1, Run 2, and the ongoing Run 3, with periods of shutdown for maintenance and upgrades. A major upgrade program, the High-Luminosity Large Hadron Collider project, is underway to prepare the detector for an increased collision rate, or luminosity, expected in the 2030s. This involves replacing the entire Inner Detector with a new all-silicon tracker, upgrading the trigger system, and enhancing the calorimeter and muon spectrometer readout electronics. These improvements, developed by the global ATLAS Collaboration, aim to maintain physics performance in a much harsher radiation environment and ensure the detector's leading role in particle physics for decades.

Category:Particle detectors Category:Experiments at CERN Category:Large Hadron Collider