What is CMS?

The CMS (Compact Muon Solenoid) experiment is located some 330 feet underground in Cessy, France, just across the border from Switzerland. CMS is one of two general-purpose LHC experiments (ATLAS is the other) designed to explore the physics of the Terascale, the energy region where physicists believe they will find answers to the central questions at the heart of 21st-century particle 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?

CMS detector
Lowering of the first large slice of the CMS detector. Image © CERN

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

The main volume of the CMS detector is a multilayered cylinder, some 70 feet long and 52 feet in diameter, weighing more than 13,000 tons. The innermost layer is a silicon-based particle tracker, surrounded by electromagnetic and hadronic calorimeters for measuring particle energies. They fit inside a central superconducting solenoid magnet, 43 feet long and 20 feet in diameter, that measures the momenta of charged particles. Outer muon detectors surround the central magnet.

The CMS collaboration comprises over 2500 scientists, including about 600 students, from more than 183 scientific institutes, including some 430 US Ph.D. physicists from 49 universities and laboratories, the largest single national group. The US groups have contributed major components to the CMS detector, including muon detectors, calorimeters, charged particle tracking devices, and parts of the trigger and the data acquisition systems.