The Higgs boson is the fundamental force-carrying particle of the Higgs field, which is responsible for imparting mass to other particles. This field was first proposed in the mid-1960s by Peter Higgs – after whom the particle is named and his colleagues.
The particle was finally discovered on July 4, 2012, by researchers at the Large Hadron Collider (LHC) — the world’s most powerful particle accelerator — at the European Particle Physics Laboratory CERN, Switzerland.
The LHC confirmed the existence of the Higgs field and the mechanism that gives rise to mass, thus completing the Standard Model of particle physics – the best description we have of the subatomic world.
As scientists approached the late 20th century, advances in particle physics had answered many questions surrounding nature’s fundamental building blocks. But while physicists steadily populated the particle zoo with electrons, protons, bosons and all flavors of quarks, some pressing questions remained stubbornly unanswered. Why have some particles below this mass?
The story of the Higgs boson is prompted by this question.
What is the Higgs boson?
The Higgs boson has a mass of 125 billion electron volts (opens in new tab) – meaning it is 130 times more massive than a proton, according to CERN (opens in new tab)† It is also chargeless with no spin – a quantum mechanical equivalent of angular momentum. The Higgs boson is the only elementary particle with no spin.
A boson is a “force carrier” particle that comes into play when particles interact with each other, exchanging a boson during this interaction. For example, when two electrons interact, they exchange a photon – the force-carrying particle of electromagnetic fields.
Because quantum field theory describes the microscopic world and the quantum fields that fill it the universe with wave mechanics, a boson can also be described as a wave in a field.
So a photon is a particle and a wave that arises from an excited electromagnetic field and the Higgs boson is the particle or “quantized manifestation” that arises from the Higgs field when excited. That field generates mass through its interaction with other particles and the mechanism supported by the Higgs boson, the Brout-Englert-Higgs mechanism.
Why is the Higgs boson called the ‘God particle’?
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The moniker of the Higgs boson “the God Particle” was solidified upon its discovery, namely as a result of the popular media. The origin of this is often associated with Nobel Prize-winning physicist Leon Lederman who called the Higgs boson the “damned particle,” out of frustration at how difficult it was to detect.
Business Insider (opens in new tab) says that when Lederman wrote a book about the Higgs boson in the 1990s, it was entitled “The Goddamn Particle,” but the publishers changed it to “The God Particle” and made a tricky connection to religion, one that physicists this day bothers.
Yet it is difficult to overestimate the importance of the Higgs boson and the Higgs field in general, because without this aspect of nature no particles would have mass. That means no starsno planets and no we — something that might help justify its hyperbolic moniker.
Why is the Higgs boson important?
In 1964, researchers began to use quantum field theory to weak nuclear force (opens in new tab) – which determines the atomic decay of elements by transforming protons into neutrons – and its power carriers are the W and Z bosons.
The weak force carriers would have to be massless, and if they weren’t, this risked a violation of a principle of nature called symmetry, which – just as the symmetry of a shape makes it look the same when twisted or flipped – ensures that the laws of nature are the same no matter how they are viewed. Randomly placing mass on particles also caused certain predictions to go towards infinity.
Still, researchers knew that because the weak force is so strong over short-range interactions — much more powerful than gravity– but very weak over longer interactions, the bosons must have mass.
The solution proposed in 1964 by Peter Higgs François Englert and Robert Brout was a new field and a way to “deceive” nature into spontaneously breaking symmetry.
An article from CERN (opens in new tab) likens this to a pencil on its tip – a symmetrical system – that suddenly tilts to point in a desired direction, destroying its symmetry. Higgs and his fellow physicist proposed that when the universe was born, it was filled with the Higgs field in a symmetrical, but unstable state — like the dangerously balanced pencil.
The field quickly finds a stable configuration in just fractions of a second, but this breaks its symmetry. This gives rise to the Brout-Englert-Higgs mechanism that imparts mass to the W and Z bosons.
What was later discovered about the Higgs field was that it would not only give mass to the W and Z bosons, but also give mass to many other fundamental particles. Without the Higgs field and the Brout-Englert-Higgs mechanism, all fundamental particles around the universe would race on the speed of light † This theory explains not only why particles have mass, but also why they have different masses.
Particles that interact more strongly – or “couple” – with the Higgs field, gain greater masses. Even the Higgs boson itself gets its mass through its own interaction with the Higgs field. This has been confirmed by looking at how Higgs boson particles decay.
A particle that has not been given mass by the Higgs field is the basic particle of light – the photon. This is because spontaneous symmetry breaking does not happen for photons, but for its fellow force-carrying particles, the W and Z bosons.
This mass-granting phenomenon also only applies to fundamental particles such as electrons and quarks. Particles such as protons – made up of quarks – get most of their mass from the binding energy that holds their components together.
While this is all in good agreement with theory, the next step was to discover evidence of the Higgs field by detecting the force-carrying particle. This would not be an easy task, in fact it would require the largest experiment and the most advanced machine in human history.
In this way, the search for the Higgs boson itself has pushed both particle accelerator and detector technology to their limits – the ultimate expression of which is the Large Hadron Collider (LHC).
Higgs Boson Discovery and the Standard Model
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Detecting the Higgs boson is not just a matter of setting up a detector and waiting for one to pass. These particles only existed in the high-energy conditions of the early universe.
That means that before this particle can be detected, these high-energy conditions must be replicated and Higgs bosons must be created. The LHC does this by accelerating protons to near-light speed and breaking them together.
This creates a cascade of particles that quickly decay into lighter particles. The Higgs boson decays too fast to be noticed and was instead identified by detecting particle decay that indicated a particle with no spin and matched theoretical predictions for this missing boson.
The particle was detected by both the LHC ATLAS detector and the Compact Muon Solenoid (CMS) detector.
The announcement of the detection of the Higgs boson was made at CERN in Geneva on July 12, 2012. It took until March of the following year to confirm that the particle detected was indeed the Higgs boson.
By revealing this particle, predicted by the Standard Model, the discovery of the Higgs boson completed this picture of the subatomic world. There are still mysteries beyond this theory, such as the nature of dark matterwhich could help solve the Higgs boson due to its unique properties.
The Higgs boson after 2012
The year after the discovery of the Higgs boson, Peter Higgs and François Englert were awarded the 2013 Nobel Prize in Physics for their Higgs field theory.
The Nobel Committee (opens in new tab) wrote of the award: “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of the mass of subatomic particles, and which was recently confirmed by the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron collider.”
The discovery of the Higgs boson may have completed the Standard Model, but it wasn’t the end of research into this elusive particle. One of the most significant discoveries made since 2012 concerns the confirmation of the Higgs’ decline.
And the research on this elusive particle will deepen during run 3 of the LHC and especially when the particle accelerator’s high brightness upgrade is on. completed in 2029 (opens in new tab)†
This allows the LHC to perform more collisions, giving researchers more opportunities to discover exotic physics, including phenomena beyond the Standard Model.
CERN estimates that after the upgrade, the accelerator will create 15 million of these particles each year. This is compared to 3 million Higgs bosons created by the LHC in 2017. This may be the key to detecting other “flavors” of the Higgs boson.
Theories beyond the Standard Model of particle physics also predict as many as five different types of Higgs bosons that may be produced less frequently than the primary Higgs boson. Even before the upgrades, scientists have provided us with tantalizing evidence of a “magnetic Higgs boson†
The discovery of the Higgs boson completed what is known as the Standard Model of particle physics. CERN explains: (opens in new tab) what this framework tells us about the subatomic world. Learn more about the Higgs boson with this article from the US Department of Energy (opens in new tab)† Explore what Frequently Asked Questions (opens in new tab) about the Higgs boson with CERN.
The Higgs boson, CERN, https://home.cern/science/physics/higgs-boson (opens in new tab)
The Higgs Boson, the Department of Energy, https://www.energy.gov/science/doe-explainsthe-higgs-boson (opens in new tab)
What is so special about the Higgs boson?, CERN, https://home.cern/science/physics/higgs-boson/what
higgs. P., BROKEN SYMMETRIES AND THE MASSES OF METERBOSONS, physical assessment letters, † [https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.13.508 (opens in new tab)]
Peter W. Higgs, the Nobel Prize, https://www.nobelprize.org/prizes/physics/2013/higgs/facts/ (opens in new tab)
High luminosity LHC, CERN, https://home.cern/science/accelerators/high-luminosity-lhc (opens in new tab)