2.2.7 Collaborative Efforts in Particle Physics

• The field of particle physics is constantly changing and as time goes on, our knowledge and understanding of the nature of particles changes too
• Particles physics experiments are used to study existing particles or to find new ones
• First, a new theory is developed; some physicists may hypothesise the existence of a new particle and its properties
  • For example, the existence of the neutrino was hypothesised to account for energy conservation in beta decay

• Experiments are then carried out to find this new particle
• Different experiments are combined to suggest a new discovery
• If the new discovery is confirmed, usually by repeat experiments which reduce experimental uncertainty, the theory is then validated
• If a theory is validated, this means the scientific community will start to accept it, as the theory is more likely to be correct

Particle Accelerators

• Particle physics experiments are incredibly different from everyday physics experiments
  • They involve complex machines called particle accelerators

• Such machines are used to collide particles at very high speeds in order to:
  • Produce new particles
  • Reveal the inner structure of particles

• The particles need to collide at very high energies meaning they travel close to the speed of light
• Particle accelerators can be linear or circular
• Circular particle accelerators require extremely powerful superconducting magnets to keep the high speed particles in a circular orbit
• The expensive and complicated pieces of equipment required to make a particle accelerator and conduct experiments requires large groups of scientists and engineers from all over the world to collaborate with each other
  • This collaboration provides the funding and expertise need to design, construct and operate experiments successfully

The Large Hadron Collider

• The Large Hadron Collider (LHC) is the world’s largest and highest-energy particle collider and the largest machine in the world. It is based at CERN in Geneva, on the France and Switzerland border. Around 2500 scientists work there, comprising of 110 nationalities!

The LHC is made up of four main detectors that experiment upon a wide range of physics

• Two protons beams are accelerated in opposite directions and made to collide at 4 main detectors:
  • ATLAS
  • CMS
  • ALICE
  • LHCb

• Each detector works in its own area of physics; ATLAS and CMS are the largest detectors researching fundamental particles, dark matter and extra dimensions(!)
• The ATLAS and CMS detector both detected the Higgs Boson
  • This is an example of the validation of a theory only after it can be repeated by other experiments