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Today, 60 years ago, the visionary convention establishing the European Organization for Nuclear Research – better known with its French acronym, CERN – entered into force, marking the beginning of an extraordinary scientific adventure that has profoundly changed science, technology, and society, and that is still far from over.

With other pan-European institutions established in the late 1940s and early 1950s — like the Council of Europe and the European Coal and Steel Community — CERN shared the same founding goal: to coordinate the efforts of European countries after the devastating losses and large-scale destruction of World War II. Europe had in particular lost its scientific and intellectual leadership, and many scientists had fled to other countries. Time had come for European researchers to join forces towards creating of a world-leading laboratory for fundamental science.

Sixty years after its foundation, CERN is today the largest scientific laboratory in the world, with more than 2000 staff members and many more temporary visitors and fellows. It hosts the most powerful particle accelerator ever built. It also hosts exhibitions, lectures, shows, meetings, and debates, providing a forum of discussion where science meets industry and society.

What has happened in these six decades of scientific research? As a physicist, I should probably first mention the many ground-breaking discoveries in Particle Physics, such as the discovery of some of the most fundamental building block of matter, like the W and Z bosons in 1983; the measurement of the number of neutrino families at LEP in 1989; and of course the recent discovery of the Higgs boson in 2012, which prompted the Nobel Prize in Physics to Peter Higgs and Francois Englert in 2013.

But looking back at the glorious history of this laboratory, much more comes to mind: the development of technologies that found medical applications such as PET scans; computer science applications such as globally distributed computing, that finds application in many fields ranging from genetic mapping to economic modeling; and the World Wide Web, that was developed at CERN as a network to connect universities and research laboratories.

If you’ve ever asked yourself what such a laboratory may look like, especially if you plan to visit it in the future and expect to see building with a distinctive sleek, high-tech look, let me warn you that the first impression may be slightly disappointing. When I first visited CERN, I couldn’t help noticing the old buildings, dusty corridors, and the overall rather grimy look of the section hosting the theory institute. But it was when an elevator brought me down to visit the accelerator that I realized what was actually happening there, as I witnessed the colossal size of the detectors, and the incredible degree of sophistication of the technology used. ATLAS, for instance, is a 25 meters high, 25 meters wide and 45 meters long detector, and it weighs about 7,000 tons!

The 27-km long Large Hadron Collider is currently shut down for planned upgrades. When new beams of protons will be circulated in it at the end of 2014, it will be at almost twice the energy reached in the previous run. There will be about 2800 bunches of protons in its orbit, each containing several hundred billion protons, separated by – as in a car race, the distance between bunches can be expressed in units of time – 250 billionths of a second. The energy of each proton will be compared to that of a flying mosquito, but concentrated in a single elementary particle. And the energy of an entire bunch of protons will be comparable to that of a medium-sized car launched at highway speed.

Why these high energies? Einstein’s E=mc² tells us that energy can be converted to mass, so by colliding two protons with very high energy, we can in principle produce very heavy particles, possibly new particles that we have never before observed. You may wonder why we would expect that such new particles exist. After all we have already successfully created Higgs bosons through very high-energy collisions, what can we expect to find beyond that? Well, that’s where the story becomes exciting.

Some of the best motivated theories currently under scrutiny in the scientific community – such as Supersymmetry – predict that not only should new particles exist, but they could explain one of the greatest mysteries in Cosmology: the presence of large amounts of unseen matter in the Universe, which seem to dominate the dynamics of all structures in the Universe, including our own Milky Way galaxy — Dark Matter.

Identifying in our accelerators the substance that permeates the Universe and shapes its structure would represent an important step forward in our quest to understand the Cosmos, and our place in it. CERN, 60 years and still going strong, is rising up to challenge.

Headline image credit: An example of simulated data modeled for the CMS particle detector on the Large Hadron Collider (LHC) at CERN. Image by Lucas Taylor, CERN. CC BY-SA 3.0 via Wikimedia Commons.

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2014 marks not just the centenary of the start of World War I, and the 75^th anniversary of World War II, but on 29 September it is 60 years since the establishment of CERN, the European Centre for Nuclear Research or, in its modern form, Particle Physics. Less than a decade after European nations had been fighting one another in a terrible war, 12 of those nations had united in science. Today, CERN is a world laboratory, famed for having been the home of the world wide web, brainchild of then CERN scientist Tim Berners-Lee; of several Nobel Prizes for physics, although not (yet) for Peace; and most recently, for the discovery of the Higgs Boson. The origin of CERN, and its political significance, are perhaps no less remarkable than its justly celebrated status as the greatest laboratory of scientific endeavour in history.

Its life has spanned a remarkable period in scientific culture. The paradigm shifts in our understanding of the fundamental particles and the forces that control the cosmos, which have occurred since 1950, are in no small measure thanks to CERN.

In 1954, the hoped for simplicity in matter, where the electron and neutrino partner a neutron and proton, had been lost. Novel relatives of the proton were proliferating. Then, exactly 50 years ago, the theoretical concept of the quark was born, which explains the multitude as bound states of groups of quarks. By 1970 the existence of this new layer of reality had been confirmed, by experiments at Stanford, California, and at CERN.

During the 1970s our understanding of quarks and the strong force developed. On the one hand this was thanks to theory, but also due to experiments at CERN’s Intersecting Storage Rings: the ISR. Head on collisions between counter-rotating beams of protons produced sprays of particles, which instead of flying in all directions, tended to emerge in sharp jets. The properties of these jets confirmed the predictions of quantum chromodynamics – QCD – the theory that the strong force arises from the interactions among the fundamental quarks and gluons.

CERN had begun in 1954 with a proton synchrotron, a circular accelerator with a circumference of about 600 metres, which was vast at the time, although trifling by modern standards. This was superseded by a super-proton synchrotron, or SPS, some 7 kilometres in circumference. This fired beams of protons and other particles at static targets, its precision measurements building confidence in the QCD theory and also in the theory of the weak force – QFD, quantum flavourdynamics.

QFD brought the electromagnetic and weak forces into a single framework. This first step towards a possible unification of all forces implied the existence of W and Z bosons, analogues of the photon. Unlike the massless photon, however, the W and Z were predicted to be very massive, some 80 to 90 times more than a proton or neutron, and hence beyond reach of experiments at that time. This changed when the SPS was converted into a collider of protons and anti-protons. By 1984 experiments at the novel accelerator had discovered the W and Z bosons, in line with what QFD predicted. This led to Nobel Prizes for Carlo Rubbia and Simon van der Meer, in 1984.

The confirmation of QCD and QFD led to a marked change in particle physics. Where hitherto it had sought the basic templates of matter, from the 1980s it turned increasingly to understanding how matter emerged from the Big Bang. For CERN’s very high-energy experiments replicate conditions that were prevalent in the hot early universe, and theory implies that the behaviour of the forces and particles in such circumstances is less complex than at the relatively cool conditions of daily experience. Thus began a period of high-energy particle physics as experimental cosmology.

This raced ahead during the 1990s with LEP – the Large Electron Positron collider, a 27 kilometre ring of magnets underground, which looped from CERN towards Lake Geneva, beneath the airport and back to CERN, via the foothills of the Jura Mountains. Initially designed to produce tens of millions of Z bosons, in order to test QFD and QCD to high precision, by 2000 its performance was able to produce pairs of W bosons. The precision was such that small deviations were found between these measurements and what theory implied for the properties of these particles.

The explanation involved two particles, whose subsequent discoveries have closed a chapter in physics. These are the top quark, and the Higgs Boson.

As gaps in Mendeleev’s periodic table of the elements in the 19^th century had identified new elements, so at the end of the 20^th century a gap in the emerging pattern of particles was discerned. To complete the menu required a top quark.

The precision measurements at LEP could be explained if the top quark exists, too massive for LEP to produce directly, but nonetheless able to disturb the measurements of other quantities at LEP courtesy of quantum theory. Theory and data would agree if the top quark mass were nearly two hundred times that of a proton. The top quark was discovered at Fermilab in the USA in 1995, its mass as required by the LEP data from CERN.

As the 21^st century dawned, all the pieces of the “Standard Model” of particles and forces were in place, but one. The theories worked well, but we had no explanation of why the various particles have their menu of masses, or even why they have mass at all. Adding mass into the equations by hand is like a band-aid, capable of allowing computations that agree with data to remarkable precision. However, we can imagine circumstances, where particles collide at energies far beyond those accessible today, where the theories would predict nonsense — infinity as the answer for quantities that are finite, for example. A mathematical solution to this impasse had been discovered fifty years ago, and implied that there is a further massive particle, known as the Higgs Boson, after Peter Higgs who, alone of the independent discoveries of the concept, drew attention to some crucial experimental implications of the boson.

Discovery of the Higgs Boson at CERN in 2012 following the conversion of LEP into the LHC – Large Hadron Collider – is the climax of CERN’s first 60 years. It led to the Nobel Prize for Higgs and Francois Englert, theorists whose ideas initiated the quest. Many wondered whether the Nobel Foundation would break new ground and award the physics prize to a laboratory, CERN, for enabling the experimental discovery, but this did not happen.

CERN has been associated with other Nobel Prizes in Physics, such as to Georges Charpak, for his innovative work developing methods of detecting radiation and particles, which are used not just at CERN but in industry and hospitals. CERN’s reach has been remarkable. From a vision that helped unite Europe, through science, we have seen it breach the Cold War, with collaborations in the 1960s onwards with JINR, the Warsaw Pact’s scientific analogue, and today CERN has become truly a physics laboratory for the world.

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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 week to explain some of the mysteries of the Higgs boson. Read the previous posts: “What is the Higgs boson?”, “Why is the Higgs boson called the ‘god particle’?”, “Is the particle recently discovered at CERN’s LHC the Higgs boson?”, and “How does the Higgs mechanism create mass?”

By Jim Baggott

The 4 July discovery announcement makes it clear that the new particle is consistent with the long-sought Higgs boson. The next step is therefore reasonably obvious. Physicists involved in the ATLAS and CMS detector collaborations at the LHC will be keen to push ahead and fully characterize the new particle. They will want to know if this is indeed the Higgs boson.

How can they tell?

I mentioned in the third post in this series that the physicists at Fermilab’s Tevatron and CERN’s LHC have been searching for the Higgs boson by looking for the tell-tale products of its different predicted decay pathways. The current standard model of particle physics is used to predict the rates of production of the Higgs boson in high-energy particle collisions and the rates of its various decay modes. After subtracting the ‘background’ that arises from all the other ways in which the decay products can be produced, the physicists are left with an excess of events that can be ascribed to Higgs boson decays.

Now that we know the new particle has a mass of between 125-126 billion electron-volts (equivalent to the mass of about 134 protons), both the calculations and the experiments can be focused tightly on this specific mass value.

So far, excess events have been observed for three important decay pathways. These involve the decay of the Higgs boson to two photons ( H → γγ), two Z bosons (H → ZZ → ι⁺ι^-ι⁺ι^-) and two W particles (H → W⁺W^- → ι⁺υ ι^-υ). You will notice that these pathways all involve the production of bosons. This should come as no real surprise, as the Higgs field is responsible for breaking the symmetry between the weak and electromagnetic forces, giving mass to the W and Z particles and leaving the photon massless.

The decay rates to these three pathways are broadly as predicted by the standard model. There is an observed enhancement in the rate of decay to two photons compared to predictions, but this may be the result of statistical fluctuations. Further data on this pathway will determine whether or not there’s a problem (or maybe a clue to some new physics) in this channel.

But the Higgs field is also involved in giving mass to fermions (matter particles, such as electrons and quarks). The Higgs boson is therefore also predicted to decay into fermions, specifically very large massive fermions such as bottom and anti-bottom quarks, and tau and anti-tau leptons. Bottom quarks and tau leptons (heavy versions of the electron) are third-generation matter particles with masses respectively of about 4.2 billion electron volts (about 4 and a half proton masses) and 1.8 billion electron volts (about 1.9 proton masses).

These decay pathways are a little more problematic. The backgrounds from other processes are more significant and considerably more data are required to discriminate the background from genuine Higgs decay events. The decay to bottom and anti-bottom quarks was studied at the Tevatron before it was shut down earlier this year. But the collider had insufficient collision energy and luminosity (a measure of the number of collisions that the particle beams can produce) to enable independent discovery of the Higgs boson.

ATLAS physicist Jon Butterworth, who writes a blog for the British newspaper The Guardian, recently gave his assessment:

If and when we see the Higgs decaying in these two [fermion] channels at roughly the predicted rates, I will probably start calling this new boson the Higgs rather than a Higgs. It won’t prove it is exactly the Standard Model Higgs boson of course, and looking for subtle differences will be very interesting. But it will be close enough to justify [calling it] the definite article.

When will this happen? This is hard to judge, but perhaps we will have an answer by the end of this year.

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?”,“Why is the Higgs boson called the ‘god particle’?”, “Is the particle recently discovered at CERN’s LHC the Higgs boson?”, and “How does the Higgs mechanism create mass?”

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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 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’?”

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  

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.”

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