![]() ![]() This development came well before the discovery of the W bosons decades later. To overcome this problem, physicists modified Fermi's theory by introducing “by hand" two massive spin-one (“vector”) charged particles propagating the interaction between neutrinos and electrons, dubbed “intermediate vector bosons". In other words, predictions become unphysical at a high enough energy. This continuous growth, however, leads to the violation of a limit derived from the conservation of probability in a scattering process. Indeed, Fermi's theory predicts that the production rate of some processes caused by the weak force – such as the elastic scattering of neutrinos on electrons – increases linearly with the neutrino energy. However it was soon realised that its predictions at high energy, a regime not yet experimentally accessible at that time, were bound to fail. This formulation successfully described the known experimental observations, including the radioactive β decay for which it was developed. (Image: ATLAS Collaboration/CERN)Įnrico Fermi originally formulated a mathematical description of the weak force in 1933 as a “contact interaction” between particles, occurring at a single point without a carrier particle propagating the force. The outgoing quarks undergo a process called hadronization and manifest as a spray of particles called a “jet”. These W bosons interact and each of the resulting W bosons decays to a muon (μ) and a neutrino (ν), where the neutrinos leave the ATLAS detector undetected. ![]() Within a very short period of time, too short to be resolved, two W bosons are emitted independently by the incoming quarks (q) from each of the LHC proton beams. They collide at approximately the centre of the detector. Protons (p) from the LHC beam travel from left to right and from right to left in this view. The insert depicts a schematic view of the candidate physics process. To appreciate the importance of this discovery, it is instructive to follow the history of how and why the W + and W – bosons were introduced it illustrates nicely how the interplay between experimental information, theoretical models and mathematical principles drives progress in physics.įigure 2: Simplified view of a proton–proton collision event recorded with the ATLAS detector that was selected as a candidate for vector-boson-scattering production. Though the weak force is not directly experienced in everyday life, it is nevertheless important as it is responsible for radioactive β decay, which plays a role in the fusion of hydrogen into helium that powers the Sun's thermonuclear process. They have integer spin (characteristic of bosons) and are carriers of the weak force. The W + and W – bosons are unstable particles, which decay (transform) into a lepton and an antilepton or a quark and an antiquark with a mean lifetime of only a few 10 -25 seconds. Another missing piece of the big puzzle had been found – the puzzle that is the mathematical description of the microscopic world (see Figure 1). The observation of vector boson scattering didn't receive as much attention from the media as the Higgs discovery in 2012, even though it was an important event for the particle physics community. It results in the production of two W particles with the same electric charge as well as two collimated sprays of particles called “jets" (see Figure 2). ![]() In 2017, the ATLAS and CMS Collaborations announced the detection of a process in high-energy proton–proton collisions that had not been observed before: the vector boson scattering. From the Mesopotamians’ cuneiform script to the mathematical formalism behind the discovery of the Higgs boson, the sculpture narrates the story of how knowledge is passed through the generations and illustrates the aesthetic nature of the mathematics behind physics. Figure 1: "Wandering the immeasurable", a sculpture designed by Gayle Hermick welcomes the CERN visitors. ![]()
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