LARGE HADRON COLLIDER
WHAT IS LARGE HADRON COLLIDER (LHC)?
- The Large Hadron Collider is the world’s largest and highest-energy particle collider.
- It was built by the European Organization for Nuclear Research between 1998 and 2008 in collaboration with over 10,000 scientists and hundreds of universities and laboratories, as well as more than 100 countries.
FUNCTIONING OF LHC
- Inside the accelerator, two high-energy particle beams travel at close to the speed of light before they are made to collide.
- The beams travel in opposite directions in separate beam pipes – two tubes kept at ultrahigh vacuum.
- They are guided around the accelerator ring by a strong magnetic field maintained by superconducting electromagnets.
- The electromagnets are built from coils of special electric cable that operates in a superconducting state, efficiently conducting electricity without resistance or loss of energy.
- This requires chilling the magnets to ‑271.3°C – a temperature colder than outer space.
- For this reason, much of the accelerator is connected to a distribution system of liquid helium, which cools the magnets, as well as to other supply services.
- Thousands of magnets of different varieties and sizes are used to direct the beams around the accelerator.
- These include 1232 dipole magnets, 15 metres in length, which bend the beams, and 392 quadrupole magnets, each 5–7 metres long, which focus the beams.
- Just prior to collision, another type of magnet is used to “squeeze” the particles closer together to increase the chances of collisions.
- The particles are so tiny that the task of making them collide is akin to firing two needles 10 kilometres apart with such precision that they meet halfway.
- All the controls for the accelerator, its services and technical infrastructure are housed under one roof at the CERN Control Centre.
- From here, the beams inside the LHC are made to collide at four locations around the accelerator ring, corresponding to the positions of four particle detectors – ATLAS, CMS, ALICE and LHCb.
EFFECTS OF COLLISION
- When two antiparallel beams of energised particles collide head on, the energy at the point of collision is equal to the sum of the energy carried by the two beams.
- Thus far, the highest centre of mass collision energy the LHC has achieved is 13.6 TeV (teraelectronvolts).
- This is less energy than what would be produced if you clapped your hands once.
- The feat is that the energy is packed into a volume of space the size of a proton, which makes the energy density very high.
- At the moment of collision, there is chaos.
- There is a lot of energy available, and parts of it coalesce into different subatomic particles under the guidance of the fundamental forces of nature.
- Which particle takes shape depends on the amount and flavour of energy available and which other particles are being created or destroyed around it.
- Some particles are created very rarely. If, say, a particle is created with a probability of 0.00001%, there will need to be at least 10 million collisions to observe it.
- Some particles are quite massive and need a lot of the right kind of energy to be created (this was one of the challenges of discovering the Higgs boson).
- Some particles are extremely short lived, and the detectors studying them need to record them in a similar timeframe or be alert to proxy effects.
- The LHC’s various components are built such that scientists can tweak all these parameters to study different particle interactions.
FINDINGS OF LARGE HADRON COLLIDER
- The LHC consists of nine detectors.
- Located over different points on the beam pipe, they study particle interactions in different ways.
- Every year, the detectors generate 30,000 TB of data worth storing, an even more overall.
- Physicists pore through this data with the help of computers to identify and analyse specific patterns.
- This is how the ATLAS and CMS detectors helped discover the Higgs boson in 2012 and confirmed their findings in 2013.
- The LHC specialises in accelerating a beam of hadronic particles to certain specifications and delivering it.
- Scientists can choose to do different things with the beam. For example, they have used the LHC to energise and collide lead ions with each other and protons with lead ions.
Using the data from all these collisions, they have tested:
- The predictions of the Standard Model of particle physics,
- The reigning theory of subatomic particles;
- Observed exotic particles like pentaquarks and tetraquarks and checked if their properties are in line with theoretical expectations
- And pieced together information about extreme natural conditions, like those that existed right after the Big Bang.
WAY FORWARD
- The LHC has tested some of the predictions of theories that try to explain what the Standard Model can’t, and caught them short. This has left the physics community in a bind.
- Efforts should be directed to build a bigger version of the LHC, based on the hypothesis that such a machine will be able to find ‘new physics’ at even higher energies.
SYLLABUS: MAINS, GS-3, SCIENCE AND TEHNOLOGY
SOURCE: THE HINDU
