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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 This was superseded by a super-proton synchrotron, or SPS, some 7 kilometres in circumference.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’?”, and “Is the particle recently discovered at CERN’s LHC the Higgs boson?”

By Jim Baggott

Through thousands of years of speculative philosophy and hundreds of years of hard empirical science, we have tended to think of mass as an innate property (a ‘primary quality’) of material substance. We figured that, whatever they might be, the basic building blocks of matter would surely consist of microscopic lumps of some kind of ‘stuff’.

But this is not quite how it has worked out. There was a clue in the title of one of Albert Einstein’s most famous research papers, published in 1905: ‘Does the inertia of a body depend on its energy content?’ This was the paper in which Einstein suggested that there was a deep connection between mass and energy, through what would subsequently become the world’s most famous equation, E = mc².

We experience the mass of an object as inertia (the object’s resistance to acceleration) and Einstein was suggesting that the latter is determined not by mass as a primary quality, but rather by the energy that the object contains.

So, when an otherwise massless particle travelling at the speed of light interacts with the Higgs field, it is slowed down. The field ‘drags’ on it, as though the particle were moving through molasses. In other words, the energy of the interaction is manifested as a resistance to acceleration. The particle acquires inertia, and we think of this inertia in terms of the particle’s ‘mass’.

In the Higgs mechanism, mass loses its status as a primary quality. It becomes secondary — the result of massless particles interacting with the Higgs field.

So, does the Higgs mechanism explain all mass? Including the mass of me, you, and all the objects in the visible universe? No, it doesn’t. To see why, let’s just take a quick look at the origin of the mass of the heavy paperweight that sits on my desk in front of me.

The paperweight is made of glass. It has a complex molecular structure consisting primarily of a network of silicon and oxygen atoms bonded together. Obviously, we can trace its mass to the protons and neutrons which account for 99% of the mass of every silicon and oxygen atom in this structure.

According to the standard model, protons and neutrons are made of quarks. So, we might be tempted to conclude that the mass of the paperweight resides in the masses of the quarks from which the protons and neutrons are composed. But we’d be wrong again. Although it’s quite difficult to determine precisely the masses of the quarks, they are substantially smaller and lighter than the protons and neutrons that they comprise. We would estimate that the masses of the quarks, derived through their interaction with the Higgs field, account for only about 1% of the mass of a proton, for example.

But if 99% of the mass of a proton is not to be found in its constituent quarks, then where is it? The answer is that the rest of the proton’s mass resides in the energy of the massless gluons — the carriers of the strong nuclear force — that pass between the quarks and bind them together inside the proton.

What the standard model of particle physics tells us is quite bizarre. There appear to be ultimate building blocks which do have characteristic physical properties, but mass isn’t really one of them. Instead of mass we have interactions between elementary particles that would otherwise be massless and the Higgs field. These interactions slow the particles down, giving rise to inertia which we interpret as mass. As these elementary particles combine, the energy of the massless force particles passing between them builds, adding greatly to the impression of solidity and substance.

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’?”, and “Is the particle recently discovered at CERN’s LHC the Higgs boson?”

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By Frank Close To readers of Neutrino, rest assured: there is no need yet for a rewrite based on news that neutrinos might travel faster than light. I have already advertised my caution in The Observer, and a month later nothing has changed. If anything, concerns about the result have increased.