What is ATLAS?

ATLAS is one of two general-purpose experiments (the other is CMS) designed to cover the largest possible range of LHC physics. The largest-volume detector ever constructed, ATLAS is 148 feet long, 82 feet wide and 82 feet high, and weighs about 7,700 tons.

ATLAS is designed to address some of the most basic and compelling questions of 21st-century physics:

  1. Are there undiscovered principles of nature?
  2. How can we solve the mystery of dark energy?
  3. Are there extra dimensions of space?
  4. What is dark matter?
  5. How did the universe come to be?

ATLAS detector
The ATLAS detector under construction in November 2005. Image © CERN

You can learn more about how ATLAS and CMS answer these questions by reading The Science of ATLAS and CMS.

The ATLAS detector contains a series of ever-larger concentric cylinders around the central interaction point where the LHC's proton beams collide. Its four complementary components include the inner detector, the calorimeters, the spectrometer and the magnet systems. Together, these specialized components provide detailed and comprehensive information about the particles emerging from proton-proton collisions. From the millions of collisions occurring each second, a sophisticated triggering system selects some hundreds of events for analysis by ATLAS scientists around the world.

The ATLAS collaboration comprises 2800 physicists including graduate students, from 169 universities and laboratories in 37 countries. In the US, the ATLAS collaboration consists of about 700 researchers at 40 universities and four national laboratories. The US groups have designed, built and delivered many ATLAS detector components, including muon detectors, charged particle tracking systems, calorimeters, and have contributed to the data acquisition and computing systems for the experiment.