Higgs boson12/25/2022 ![]() ![]() Quantum field theory tells us that this hypothetical region is not really empty: particle–antiparticle pairs associated with different quantum fields pop into existence briefly before annihilating, transforming into energy. Imagine an empty region of space, a perfect vacuum, without any matter present in it. The Higgs field is peculiar in two particular ways. The mathematical puzzle had been solved decades ago but whether the maths described physical reality remained to be tested. “To accommodate the mass of the W and Z bosons, we don’t need the same Higgs field to give mass to any other particles such as electrons or quarks,” remarks Kerstin Tackmann, a co-convener of the Higgs group on ATLAS. ![]() Originally conceived to explain the masses of the W and Z bosons only, scientists soon found they could extend the Brout-Englert-Higgs mechanism to account for the mass of all massive elementary particles. “It is exactly this mechanism,” Cerutti adds, “that creates all the complexity of the Standard Model.” ![]() Only particles that interact with the Higgs field acquire mass. The Brout-Englert-Higgs mechanism introduced a new quantum field that today we call the Higgs field, whose quantum manifestation is the Higgs boson. In 1964, two papers – one by Robert Brout and François Englert, the other by Peter Higgs – purported to have a solution: a new mechanism that would break the electroweak symmetry. “The photon, which carries electromagnetism, we knew was massless the W and Z bosons, carriers of the weak force, could not be.” Although the W and Z had not been directly observed at the time, physicists knew that if they were to have no mass, processes such as beta decay would have occurred at infinite rates – a physical impossibility – while other processes would have probabilities greater than one at high energies. The force which is thus unified is dubbed the electroweak force.īut these very symmetries presented a glaring problem: “The symmetries explained the electroweak force but in order to keep the symmetries valid, they forbid its force-carrying particles from having mass,” explains Fabio Cerutti, who co-led Higgs groups at ATLAS on two separate occasions. Using this notion, physicists can provide a unified set of equations for both electromagnetism (electricity, magnetism, light) and the weak nuclear force (radioactivity). The Standard Model is based on the notion of symmetries in nature, that the physical properties they describe remain unchanged under some transformation, such as a rotation in space. The Standard Model of particle physics represented in a single equation (Image: CERN) Today we call this elegant description the Standard Model of particle physics. In quantum field theory, both matter particles ( fermions such as electrons, or the quarks inside protons) and the force carriers ( bosons such as the photon, or the gluons that bind quarks) are manifestations of underlying, fundamental quantum fields. ![]() “In the 1960s, theoretical physicists were working on an elegant way of describing the fundamental laws of nature in terms of quantum field theory,” says Pier Monni, of CERN’s Theory department. Easy for a physicist, perhaps…Īt the subatomic scale, the universe is a complex choreography of elementary particles interacting with one another through fundamental forces, which can be explained using a term that physicists of all persuasions turn to: elegance. “ Easy! It is the first and only elementary scalar particle we have observed,” grins Rebeca Gonzalez Suarez, who, as a doctoral student, was involved in the CMS search for the Higgs boson. So what exactly is so special about this particle? 4 July 2012: A packed auditorium at CERN listens keenly to the announcement from CMS and ATLAS (Image: Maximilien Brice/CERN) Applause reverberated in Geneva from as far away as Melbourne, Australia, where delegates of the International Conference on High Energy Physics were connected via video-conference. Heuer spoke in the Laboratory’s main auditorium on 4 July 2012, moments after the CMS and ATLAS collaborations at the Large Hadron Collider announced the discovery of a new elementary particle, which we now know is a Higgs boson. “ It” was the Higgs boson, the almost-mythical entity that had put particle physics in the global spotlight, and the man proclaiming to be a mere layman was none other than CERN’s Director-General, Rolf Heuer. As a layman I would now say… I think we have it. ![]()
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