Ten years ago, scientists announced the discovery of the Higgs boson, which helps explain why elementary particles (the smallest building blocks of nature) have mass. For particle physicists, it was the end of a decade-long and extremely difficult journey – and arguably the most important result in the history of the field. But this end also marked the beginning of a new era of experimental physics.
Over the past decade, measurements of the properties of the Higgs boson have confirmed predictions of the Standard Model of particle physics (our best theory for particles). But it has also raised questions about the limits of this model, such as whether there is a more fundamental theory of nature.
Physicist Peter Higgs predicted the Higgs boson in a series of papers between 1964 and 1966 as an inevitable consequence of the mechanism responsible for giving mass to elementary particles. This theory states that particle mass is the result of elementary particles interacting with a field, called the Higgs field.
And according to the same model, such a field should also give rise to the Higgs particle – meaning that if there was no Higgs boson, it would eventually falsify the whole theory.
But it soon became clear that discovering this particle would be challenging. When three theoretical physicists calculated the properties of the Higgs boson, they concluded with an apology: “We apologize to the experimentalists for not knowing what the mass of the Higgs boson is … and its coupling with other particles.” Not to be sure about … the reasons for these, we do not want to encourage major experimental discoveries for the Higgs boson.”
Discovery of the Higgs Boson
It took until 1989 for the first experiment with a serious chance to begin the search for the Higgs boson. The idea was to break up the particles with such high energy that the 27 km-long tunnel at CERN in Geneva, Switzerland, created a Higgs particle – the largest electron-positron (a positron is roughly the same as an electron but its Has opposite charge) Collider ever created. It lasted 11 years, but its maximum energy was just 5% less than that required to produce the Higgs boson.
Meanwhile, the most ambitious American collider in history, the Tevatron, had begun taking data at Fermilab close to Chicago. The Tevatron collided with protons (which, along with neutrons, make up the atomic nucleus) and antiprotons (almost the same as protons but with the opposite charge) with energies five times greater than that achieved in Geneva – to form the Higgs, of course. enough. But the proton-antiproton collision leaves a lot of debris, making it very difficult to extract the signal from the data. In 2011, the Tevatron ceased operation – the Higgs boson escaped detection again.
In 2010, the Large Hadron Collider began colliding with protons with an energy seven times greater than that of the Tevatron. Finally, on 4 July 2012, two independent experiments at CERN had gathered enough data to announce the discovery of the Higgs boson. The following year, Higgs and his colleague François Englert won the Nobel Prize “for the theoretical discovery of mechanisms contributing to our understanding of the origin of the mass of subatomic particles”.
It almost sells it for less. Without the Higgs boson, the entire theoretical framework describing particle physics at its smallest scales falls apart. The elementary particles would be massless, the universe would have no atoms, no humans, no solar system, and no structure.
trouble on the horizon
Yet this discovery has raised new, fundamental questions. CERN’s experiments continue to investigate the Higgs boson. Its properties determine not only the mass of elementary particles, but also how stable they are. As it stands, the results suggest that our universe is not in a completely stable state.
Instead, the universe may suddenly undergo a rapid “phase transition”, similar to ice at its melting point. But instead of going from a solid to a liquid, like the transition of ice to water, it would have to significantly change the masses—and the laws of nature—in the universe.
The fact that the universe nonetheless seems to be stationary suggests that something may be missing in the calculations – something we haven’t discovered yet.
After a three-year hiatus for maintenance and upgrades, collisions at the Large Hadron Collider are now about to resume at an unprecedented energy, nearly twice that of the Higgs boson detected. It could help find the missing particles that lead our universe away from the apparent knife-edge between undergoing a phase transition between stable and accelerating.
The experiment can also help answer other questions. Could the unique properties of the Higgs boson make it a portal to the search for dark matter, the invisible matter making up most of the matter in the universe? Dark matter does not charge. And the Higgs boson has a unique way of interacting with uncharged matter.
Those same unique properties have led physicists to question whether the Higgs boson might not be a fundamental particle. Could there be a new, unknown force beyond the other forces of nature – gravity, electromagnetism and the weak and strong nuclear forces? Perhaps a force that binds hitherto unknown particles into a composite object we call the Higgs boson?
Such a theory could help address controversial results of recent measurements that suggest that some particles do not behave exactly as the Standard Model suggests they should. The study of the Higgs boson is therefore important to find out whether there are physics to be discovered beyond the Standard Model.
Eventually, the Large Hadron Collider will face the same problems as the Tevatron did. Proton collisions are messy and the energy of its collision will only reach this far. Even though we have the full arsenal of modern particle physics – including sophisticated detectors, advanced detection methods and machine learning – at our disposal, there is a limit to what the Large Hadron Collider can achieve.
A future high-energy collider, designed specifically to produce the Higgs boson, will enable us to accurately measure its most important properties, including how the Higgs boson interacts with other Higgs bosons. . This in turn will determine how the Higgs boson interacts with its field. So studying this interaction can help us investigate the underlying process that gives particles mass. Any disagreement between theoretical prediction and future measurements would be a clear indication that we need to invent entirely new physics.
These measurements will have profound implications that reach far beyond collider physics, guiding or hindering our understanding of the origins of dark matter, the birth of our universe – and, perhaps, its eventual fate.
Martin Bauer is an associate professor of physics at Durham University. Stephen Jones is an assistant professor of physics at Durham University.
This article first appeared on The Conversation.