We Descended into CERN's Hadron Collider: Klix.ba at the Heart of Experimental Physics, 100 Metres Underground

The Klix.ba portal was given exclusive access to one of the largest laboratories in the world: CMS, a particle detector that is part of the Large Hadron Collider, lying 100 metres underground on the border between Switzerland and France.

The Hadron Collider (LHC) is 27 kilometres long and forms an irregular ring that is part of CERN, the European Council for Nuclear Research near Geneva. The word "hadron" refers to a group of particles, such as neutrons and protons, which together with electrons make up atoms.

The collider is the central element of all the work done by physicists at CERN and is used for a number of experiments, such as ATLAS, ALICE, LHCb and CMS.

Our reporter descended into the last of these, CMS, together with 20 mathematics and physics teachers from Bosnia and Herzegovina who visited CERN as part of the First Bosnian-Herzegovinian CERN Teacher Programme.

We were taken down into the CMS shaft by a large lift housed in a building that in no way betrays the fact that it hides one of the most important experiments in physics today. Numerous warning signs have been put up for visitors and engineers alike, among them an amusing but by no means unimportant one: no holding selfie sticks over the railing.

For context, the railing is located at the edge of the shaft, so any object that fell in could seriously injure the workers.

At the level where CMS sits, concrete corridors lead visitors to a platform at the height of the centre of the detector's cross-section. Since visits are generally only possible while the accelerator and detector are being upgraded or repaired, CMS had been "taken apart" into segments that revealed its interior.

The teachers from BiH were given details of how the detector works along with its technical specifications, only some of which may be clear to a wider audience. So let us take it step by step.

What is CMS, anyway?

CMS, or the Compact Muon Solenoid, is designed to confirm and search for the wide spectrum of particles that make up our universe, including the most important ones it is intensively searching for – dark matter particles and those that would prove, for example, the existence of extra spatial dimensions.

CMS is also known as one of the two detectors (the other being ATLAS) that in 2012 observed the Higgs boson, or "God particle", the carrier of the Higgs field responsible for giving mass to the tiniest known building blocks of reality.

Put simply, it is a large, layered, sophisticated cylindrical magnet, 21 metres long and 15 metres high. CMS weighs more than 14,000 tonnes and its magnets are 100,000 times stronger than the Earth's magnetic field.

How does CMS work?

At its centre, protons – the particles that together with neutrons form the nucleus of the atom – collide after first being accelerated in the 27-kilometre-long LHC. Physicists observe the debris of the collisions, which CMS "captures" and then sends to the data processing centre at a rate of one terabyte per second.

Unfortunately, most of the data has to be deleted and only the most useful segments are kept, because there is still no system in the world that could store such a quantity of information.

CMS is also interesting because, despite its weight, it was built at ground level and then gradually lowered into a "hole" 100 metres deep, often with the help of ship cranes. Bear in mind that CMS is located in France, some 300 kilometres from the nearest coastline.

This detector is powered by power plants in France, which is not surprising, since it is located on French soil. But other parts of CERN that are in Switzerland are also often powered by the French, because electricity in Switzerland is extremely expensive.

What do the experts at CMS want?

In cooperation with ATLAS, which is both partner and counterweight in the discovery of potential new laws and particles, the physicists at CMS, besides constantly confirming what we already know, actually dream of discoveries that will build on or even overturn our current understanding of the universe at the particle level.

The Standard Model is currently the best theory explaining what our reality is made of. However, things such as dark matter, which is itself an unknown, cannot find their place in the Standard Model.

This is why most physicists believe it is incomplete or even wrong, although there is still no evidence for this today. In this consensus – the knowledge that we do not know everything – lie the foundations of future Nobel Prizes.

Source: klix.ba