The European Organization for Nuclear Research – known by its French acronym, CERN – is the largest particle physics laboratory in the world. Located just outside Geneva, Switzerland, as one of Europe’s first post-war joint ventures, with the express purpose of stopping the ‘brain drain’ of talented scientists leaving the continent for America.
Today, more than 10,000 scientists from more than 100 countries come to CERN each year to use its facilities, which include some of the largest and most complex scientific instruments ever created. Their goal: to understand what the Universe is made of and the laws of physics that dictate its behavior.
Highlights include the 1983 discovery of a pair of elementary particles called the W and Z bosons, which went on to be awarded the Nobel Prize in Physics. British computer scientist Tim Berners-Lee helped invent the World Wide Web at CERN in 1989 by developing a way for computers to communicate with each other, called Hypertext Transfer Protocol (HTTP).
In 1995, scientists at CERN were the first to create atoms of the antimatter homologous to hydrogen, antihydrogen. In 2000, they discovered a new state of matter: a hot, dense soup of particles called quark-gluon plasma. And the Higgs boson was first observed in 2012 at CERN’s Large Hadron Collider (LHC), earning its discoverers a Nobel Prize.
This track is an example of simulated data modeled for the CMS detector on the Large Hadron Collider (LHC) at CERN. The Higgs boson is produced when two protons collide at 14 TeV and rapidly decays into four muons, a type of heavy electron that is not absorbed by the detector. The traces of the other products of the collision are represented by lines and the energy deposited in the detector is represented in blue. © Lucas Taylor/CERN
Particle collisions recreate, for a fraction of a second, the conditions that existed moments after the Big Bang, when the Universe was born. By studying the debris from these collisions, physicists try to solve mysteries such as the composition of matter and how particles get their mass.
The LHC, which was completed in 2008, was built primarily to test the Standard Model of particle physics. This wildly successful theory from the 1970s describes the interactions between 17 elementary particles and three of the four fundamental forces of the Universe: electromagnetism, the strong nuclear force and the weak nuclear force (gravity is the fourth).
An engineer works on the Compact Muon Solenoid (CMS) detector assembly in a tunnel of the Large Hadron Collider (LHC) at CERN during maintenance work
The standard model has long predicted the existence of an unprecedented elementary particle called the Higgs boson. After four decades of searching, in July 2012 physicists finally found it thanks to the LHC. The discovery was a big win for Standard Model fans, but the theory is incomplete. It leaves many open questions, such as: what is dark matter? Why does the Universe contain more matter than antimatter? The LHC can help answer these questions.
The machine is buried deep under the Franco-Swiss border near Geneva, in a circular tunnel almost 27 kilometers long. It uses over 1,000 35-ton superconducting dipole magnets (cooled to -271.3°C – colder than outer space!), to guide two beams of particles (usually protons) into opposite directions around the ring. The protons travel around the 27 kilometer ring at nearly the speed of light, spinning more than 11,000 revolutions per second.
At four points around the ring, the two opposite beams are directed so that they intersect. Where the beams cross, the protons they contain collide and break into smaller particles. Most of the particles produced in collisions are very unstable and almost instantaneously decay into more stable forms.
Seven huge detectors – think of it like cathedral-sized digital cameras – are built around the four collision zones to capture data on these incredibly rare particles as they briefly flare up.
The Large Hadron Collider (LHC) is the largest and most powerful particle accelerator in the world. It consists of a 27 kilometer ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way.
The LHC was initially commissioned in September 2008, with an operating plan for at least two decades. The European Organization plan includes a handful of long shutdowns where the machine is turned off so that scientists can access the equipment, carry out repairs and make upgrades that allow it to operate at higher energy levels, which which means more potential discoveries, in the next race.
The Last Long Shutdown (LS2) began in 2019, and on April 22, 2022, the LHC restarted the European Organization after three years of maintenance work and upgrades, allowing a new proton collision.
We spoke to Dr. Monica Dunford, the physicist responsible for coordinating Standard Model research at the ATLAS experiment (one of two international collaborations credited with the discovery of the Higgs).
“With this next race, we expect to get about twice the total brightness of the European organization that we had at the end of race 2,” says Dunford. Luminosity is how physicists describe the intensity of particle beams. Doubling the brightness doubles the probability of particles colliding, ATLAS announced the first-ever observation of three W bosons produced simultaneously, from a data set taken between 2015 and 2018. Compared to the creation of a Higgs boson, the production of “triple W” is about 60 times less likely to occur in proton collisions.
“This is such a rare process that it makes us confident that maybe even in run 3 we could eventually measure Higgs self-coupling,” Dunford says. A Higgs paired with two others – a “trilinear Higgs” – is about 2,000 times less likely than a normal Higgs.
Things could really start to get exciting after the next long stop, currently the European Organization scheduled for 2026-2028. During this period, the LHC will be so modernized that it deserves a new name: the High-Luminosity LHC (HL-LHC). In more than 20 years of operation, the machine will run until it generates luminosities nearly 30 times greater than those produced to date, allowing physicists to push the Standard Model to its limits.
And the search for new physics does not stop there. A proposed new collider – the Future Circular Collider (FCC) – would dwarf the LHC. “It’s really just a concept at the moment, but ultimately it would be an even more powerful collider that would be 100 kilometers away,” says Dunford. “The LHC ring would in fact only be the FCC booster ring!”
Source: This news was originally published by sciencefocus