The reaction of physicist Peter Higgs was only lukewarm when it came to the most important theoretical work of his lifetime, the discovery of the Higgs Boson particle on July 4, 2012, which was done with the help of the Large Hadron Collider.
The particle had garnered much limelight within the scientific community and was aptly named as the god-particle. This was the only particle in the Standard Model of Particle Physics that needed to be experimentally graphed and analyzed.
The key motivation behind building the Large Hadron Collider was to discover the Higgs-Boson particle, and this has set the course which will define the course of further research in physics. The discovery of the particle played a pivotal role in confirming the predictions about fundamental forces and particles that govern the laws of the universe.
Finding the Higgs particle during Peter Higgs’s lifetime was far from guaranteed. The theoretical framework suggesting the boson’s existence did not specify its mass, leaving physicists to search across an extensive range.
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It took scientists 48 years to pinpoint the elusive particle after Higgs and his colleagues first proposed its existence. No other fundamental particle has taken so long to discover.
Reina Camacho Toro, an experimental particle physicist at Paris Cité University and CERN, says, the decade-spanning story of the prediction and detection of the Higgs highlights “the importance of working together, [as well as] the communication between the theory community and experimental community.”
Higgs was born in Newcastle-upon-Tyne, he secured his PhD from Kings College London and then further pursued his research at the University of Edinburgh, and it was during this time his most famous paper was published in 1964. This was a time when the standard model of physics was not yet conceptualized.
Physicists were still grappling with the multitude of particles known as hadrons, which were being uncovered in early accelerator and cosmic-ray experiments. At that time, they hadn’t yet realized that these particles were actually combinations of a smaller set of fundamental particles called quarks, held together by a strong force.
The strong force was something the physicists knew about, it’s the force holding the particles together which encompasses the nuclei and atoms. Weak force was also understood which could be observed through its role in radioactive delay. The recently conceptualized theory of quantum electrodynamics sufficiently described the relation between electricity and magnetism and how they both interacted when combined into electromagnetic interaction.
Physicists attempted to develop a unified field theory that could combine the strong and weak forces, but they were unable to succeed. The challenge lay with the particles that mediate the weak force, known as W and Z bosons. Unlike other force-carrying particles, which are massless, W and Z bosons have mass. Physicists were still trying to figure out why the W and Z bosons were different, and why these were the only force-carrying particles.
In 1964, Peter Higgs published a paper explaining how symmetry might have been broken in the universe. To simplify his explanation: Imagine the early universe filled with a symmetrical but unstable field that provides particle masses. Over time, this field settled into a more stable state. This transformation could have preserved the mathematical symmetry of the equations describing different forces, but instead, it resulted in observable differences between the particles carrying those forces. This briefly unstable field, now known as the Higgs field, allowed for the existence of massive W and Z bosons.
Higgs elaborated on his groundbreaking ideas in a subsequent paper, detailing what would become known as “the Higgs model.” Initially, the journal Physics Letters rejected this paper, deeming it not urgent enough to publish. Undeterred, Higgs revised his work, highlighting a crucial aspect: the potential association of this field with a massive boson, a concept also mentioned by theorists Francois Englert and Robert Brout. This new boson would be unlike any other, possessing a unique spin-zero property, unlike the other particles, which all had spin. Higgs had provided physicists with a clear path to validate his theory: discover this new boson.
Even though the paper got accepted it took years for the research community to gain interest in it. This delay is a continuing source of inspiration. Dave Sutherland, a theoretical particle physicist at the University of Glasgow, says, “As a theorist, you are hugely buoyed by [this story]… the whole history of particle physics is littered with these successes.”
The discovery of Higgs Boson had been the major game for particle physics for almost all of the latter half of the twentieth century it has occupied the research right now as well. With its discovery of many more only a small piece in the cosmic puzzle has been placed and further research still is still required.
Basic aspects of the Higgs particle remain uncertain, including whether it is a fundamental particle or possesses an internal structure. Sutherland points out that “every theorist is focused on the Higgs trilinear coupling,” a measurement essential for understanding how Higgs bosons are generated in pairs within the Standard Model.
Enormous amounts of data were collected during the second run of the LHC. This has allowed the ATLAS and CMS experiments at CERN to concisely formulate how the Higgs couples with fundamental particles such as the bottom and top quarks and tau lepton, yet there is much to discover. As Camacho Toro points out, “There are other couplings that we have not observed yet, like for example the couplings to [charm] quarks or the couplings even to electrons or to muons.”
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