We’re celebrating the release of Higgs: The Invention and Discovery of the ‘God Particle’ with a series of posts by science writer Jim Baggott over the week to explain some of the mysteries of the Higgs boson. Read the previous posts: “What is the Higgs boson?” and “Why is the Higgs boson called the ‘god particle’?”
By Jim Baggott
Experimental physicists are by nature very cautious people, often reluctant to speculate beyond the boundaries defined by the evidence at hand.
Although the Higgs mechanism is responsible for the acquisition of mass, the theory does not give a precise prediction for the mass of the Higgs boson itself. The search for the Higgs boson, both at Fermilab’s Tevatron collider and CERN’s Large Hadron Collider (LHC), has therefore involved elaborate calculations of all the different ways a Higgs boson might be created in high-energy particle collisions, and all the different ways it may decay into other elementary particles.
At CERN, the attentions of physicists working in the two main detector collaborations, ATLAS and CMS, have been drawn to Higgs decay pathways involving the production of two photons (which we write as H → γγ), a pathway leading to two Z bosons and thence four leptons (particles such as electrons and positrons, written H → ZZ → ι+ι-ι+ι-) and a pathway leading to two W particles and thence to two leptons and two neutrinos (H → W+W- → ι+υ ι-υ).
Finding the Higgs boson is then a matter of looking for its decay products — in this case the photons and leptons that result — at all the different masses that the Higgs may in theory possess. Just to make life more difficult, at the particle collision energies available at the LHC, there are lots of other processes that can produce photons and leptons, and this background must be calculated and subtracted from the observed decay events. Any events above background that produce two photons, four leptons or two leptons (and ‘missing’ energy, as neutrinos cannot be detected) then contribute to the evidence for the Higgs boson.
What the CERN scientists announced on 4 July was a statistically significant excess of decay events consistent with a Higgs boson with a mass between 125-126 billion electron volts, about 134 times the mass of a proton. This is definitely a new boson, one that decays very much like a Higgs boson is expected to decay. But, until the scientists can gather more data on its physical properties, they can’t say for sure precisely what kind of boson it is.
It’s also important to note that although the Higgs boson is predicted by the standard model of particle physics, there are theories that also predict the existence of a Higgs boson (actually, they predict many Higgs bosons). Until the scientists gather more data, they can’t be sure the new particle is precisely the particle predicted by the standard model.
We just need to be patient and stay tuned.
Jim Baggott is author of Higgs: The Invention and Discovery of the ‘God Particle’ and a freelance science writer. He was a lecturer in chemistry at the University of Reading but left to pursue a business career, where he first worked with Shell International Petroleum Company and then as an independent business consultant and trainer. His many books include Atomic: The First War of Physics (Icon, 2009), Beyond Measure: Modern Physics, Philosophy and the Meaning of Quantum Theory (OUP, 2003), A Beginner’s Guide to Reality (Penguin, 2005), and A Quantum Story: A History in 40 Moments (OUP, 2010). Read his previous blog posts.
On 4 July 2012, scientists at CERN’s Large Hadron Collider (LHC) facility in Geneva announced the discovery of a new elementary particle they believe is consistent with the long-sought Higgs boson, or ‘god particle’. Our understanding of the fundamental nature of matter — everything in our visible universe and everything we are — is about to take a giant leap forward. So, what is the Higgs boson and why is it so important? What role does it play in the structure of material substance? We’re celebrating the release of Higgs: The Invention and Discovery of the ‘God Particle’ with a series of posts by science writer Jim Baggott over the week to explain some of the mysteries of the Higgs. Read the previous posts: “What is the Higgs boson?” and “Why is the Higgs boson called the ‘god particle’?”
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We’re celebrating the release of Higgs: The Invention and Discovery of the ‘God Particle’ with a series of posts by science writer Jim Baggott over the next week to explain some of the mysteries of the Higgs boson. Read the previous post: “What is the Higgs boson?”
By Jim Baggott
The Higgs field was invented to explain how otherwise massless force particles could acquire mass, and was used by Weinberg and Salam to develop a theory of the combined ‘electro-weak’ force and predict the masses of the W and Z bosons. However, it soon became apparent that something very similar is responsible for the masses of the matter particles, too.
The way the Higgs field interacts with otherwise massless boson fields and the way it interacts with massless fermion fields is not the same (the latter is called a Yukawa interaction, named for Japanese physicist Hideki Yukawa). Nevertheless, the Higgs field clearly has a fundamentally important role to play. Without it, both matter and force particles would have no mass. Mass could not be constructed and nothing in our visible universe could be.
In his popular book The God Particle: If the Universe is the Answer, What is the Question?, first published in 1993, American physicist Leon Lederman (writing with Dick Teresi) explained why he’d chosen this title:
This boson is so central to the state of physics today, so crucial to our final understanding of the structure of matter, yet so elusive, that I have given it a nickname: the God Particle. Why God Particle? Two reasons. One, the publisher wouldn’t let us call it the Goddamn Particle, though that might be a more appropriate title, given its villainous nature and the expense it is causing. And two, there is a connection, of sorts, to another book, a much older one…
Lederman went on to quote a passage from the Book of Genesis.
This is a nickname that has stuck. Most physicists seem to dislike it, as they believe it exaggerates the importance of the Higgs boson. Higgs himself doesn’t seem to mind.
Jim Baggott is author of Higgs: The Invention and Discovery of the ‘God Particle’ and a freelance science writer. He was a lecturer in chemistry at the University of Reading but left to pursue a business career, where he first worked with Shell International Petroleum Company and then as an independent business consultant and trainer. His many books include Atomic: The First War of Physics (Icon, 2009), Beyond Measure: Modern Physics, Philosophy and the Meaning of Quantum Theory (OUP, 2003), A Beginner’s Guide to Reality (Penguin, 2005), and A Quantum Story: A History in 40 Moments (OUP, 2010). Read his previous blog post “Putting the Higgs particle in perspective.”
On 4 July 2012, scientists at CERN’s Large Hadron Collider (LHC) facility in Geneva announced the discovery of a new elementary particle they believe is consistent with the long-sought Higgs boson, or ‘god particle’. Our understanding of the fundamental nature of matter — everything in our visible universe and everything we are — is about to take a giant leap forward. So, what is the Higgs boson and why is it so important? What role does it play in the structure of material substance? We’re celebrating the release of Higgs: The Invention and Discovery of the ‘God Particle’ with a series of posts by science writer Jim Baggott over the next week to explain some of the mysteries of the Higgs. Read the previous post: “What is the Higgs boson?”
Subscribe to the OUPblog via email or RSS.
Subscribe to only physics and chemistry articles on the OUPblog via email or RSS.
View more about this book on the
On 4 July 2012, scientists at CERN’s Large Hadron Collider (LHC) facility in Geneva announced the discovery of a new elementary particle they believe is consistent with the long-sought Higgs boson, or ‘god particle’. Our understanding of the fundamental nature of matter — everything in our visible universe and everything we are — is about to take a giant leap forward. So, what is the Higgs boson and why is it so important? What role does it play in the structure of material substance? We’re celebrating the release of Higgs: The Invention and Discovery of the ‘God Particle’ with a series of posts by science writer Jim Baggott over the next week to explain some of the mysteries of the Higgs.
By Jim Baggott
We know that the physical universe is constructed from elementary matter particles (such as electrons and quarks) and the particles that transmit forces between them (such as photons). Matter particles have physical characteristics that we classify as fermions. Force particles are bosons.
In quantum field theory, these particles are represented in terms of invisible energy ‘fields’ that extend through space. Think of your childhood experiences playing with magnets. As you push the north poles of two bar magnets together, you feel the resistance between them grow in strength. This is the result of the interaction of two invisible, but nevertheless very real, magnetic fields. The force of resistance you experience as you push the magnets together is carried by invisible (or ‘virtual’) photons passing between them.
Matter and force particles are then interpreted as fundamental disturbances of these different kinds of fields. We say that these disturbances are the ‘quanta’ of the fields. The electron is the quantum of the electron field. The photon is the quantum of the electromagnetic field, and so on.
In the mid-1960s, quantum field theories were relatively unpopular among theorists. These theories seemed to suggest that force carriers should all be massless particles. This made little sense. Such a conclusion is fine for the photon, which carries the force of electromagnetism and is indeed massless. But it was believed that the carriers of the weak nuclear force, responsible for certain kinds of radioactivity, had to be large, massive particles. Where then did the mass of these particles come from?
In 1964, four research papers appeared proposing a solution. What if, these papers suggested, the universe is pervaded by a different kind of energy field, one that points (it imposes a direction in space) but doesn’t push or pull? Certain kinds of force particle might then interact with this field, thereby gaining mass. Photons would zip through the field, unaffected.
One of these papers, by English theorist Peter Higgs, included a footnote suggesting that such a field could also be expected to have a fundamental disturbance — a quantum of the field. In 1967 Steven Weinberg (and subsequently Abdus Salam) used this mechanism to devise a theory which combined the electromagnetic and weak nuclear forces. Weinberg was able to predict the masses of the carriers of the weak nuclear force: the W and Z bosons. These particles were found at CERN about 16 years later, with masses very close to Weinberg’s original predictions.
By about 1972, the new field was being referred to by most physicists as the Higgs field, and its field quantum was called the Higgs boson. The ‘Higgs mechanism’ became a key ingredient in what was to become known as the standard model of particle physics.
Jim Baggott is author of Higgs: The Invention and Discovery of the ‘God Particle’ and a freelance science writer. He was a lecturer in chemistry at the University of Reading but left to pursue a business career, where he first worked with Shell International Petroleum Company and then as an independent business consultant and trainer. His many books include Atomic: The First War of Physics (Icon, 2009), Beyond Measure: Modern Physics, Philosophy and the Meaning of Quantum Theory (OUP, 2003), A Beginner’s Guide to Reality (Penguin, 2005), and A Quantum Story: A History in 40 Moments (OUP, 2010). Read his previous blog post “Putting the Higgs particle in perspective.”
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Subscribe to only physics and chemistry articles on the OUPblog via email or RSS.
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