Atlas

ATLAS

ATLAS, WHO ARE WE? ATLAS is a governing body of the LHC.

We are one of the world’s largest and most respected centers for scientific research. Our business is fundamental physics, finding out what the Universe is made of and how it works. ATLAS has the biggest and most scientific instruments in the world. These instruments are used to study what makes up matter and its fundamental particles. While studying the collision of those particles, our physicists will be able to learn about the laws of nature. Our physicists are some of the most renowned and educated minds the world has to offer. We span from all over the world as this has become a global project. The instruments used at ATLAS are called particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

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PROJECT ORIGIN Project Origin’s goals is to findanswers to questions about the universe, what it is made of and how it works. The LHC replicates the conditions of the universe immediately after “the Big Bang” in order to help physicists understand its effects and to examine matter’s smallest components. Project Origin involves thousands of people in the scientific community and will study the collision of two protons at high energies: in each collision, the two initial protons “disappear” to create several different particles moving in various directions.

What is the origin of mass? Why do tiny particles weigh the amount they do? Why do some particles have no mass at all? At present, there are no established answers to these questions. The most likely explanation may be found in the Higgs boson, a key undiscovered particle that is essential for the Standard Model to work.

First hypothesised in 1964, it has yet to be observed. Project Origin will possibly be able to answer theses questions.

Everything we see in the Universe, from an ant to a galaxy, is made up of ordinary particles. These are collectively referred to as matter, forming 4% of the Universe.

Dark matter and dark energy are believed to make up the remaining proportion, but they are incredibly difficult to detect and study, other than through the gravitational forces they exert.

Investigating the nature of dark matter and dark energy is one of the biggest challenges today in the fields of particle physics and cosmology.

What was matter like within the first second of the Universe’s life? The ALICE experiment will use the LHC to recreate conditions similar to those just after the Big Bang, in particular to analyse the properties of the quark-gluon plasma.

Alice is just one of many sectors that Project Origin is using to answer these mysterious questions.

Fig.1 Project Origin, world’s largest particle accelerator.

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KNOWING ORIGIN The Large Hadron Collider (LHC) is the world’s largest and highest-energy particle accelerator, intended to collide opposing particle beams of either protons at an energy of 7 TeV per particle or lead nuclei at an energy of 574 TeV per nucleus. It lies in a tunnel 27 kilometres (17 mi) in circumference, as much as 175 metres (570 ft) beneath the Franco-Swiss border near Geneva, Switzerland.

The Large Hadron Collider was built by the European Organization for Nuclear Research (ATLAS) with the intention of testing various predictions of highenergy physics, including the existence of the hypothesized Higgs boson and of the large family of new particles predicted by supersymmetry. It is funded by and built in collaboration with over 10,000 scientists and engineers from over 100 countries as well as hundreds of universities and laboratories. September 2008, the proton beams were successfully circulated in the main ring of the LHC for the first time.

On 19 September 2008, the operations were halted due to a serious fault between two superconducting bending magnets. Due to the time required to repair the resulting damage and to add additional safety features, the LHC is scheduled to be operational in midNovember 2009.

The LHC was built to help scientists to answer key unresolved questions in particle physics. The unprecedented energy it achieves may even reveal some unexpected results never thought of.

For the past few decades, physicists have been able to describe with increasing detail the fundamental particles that make up the Universe and the interactions between them. This understanding is encapsulated in the Standard Model of particle physics, but it contains gaps and cannot tell us the whole story. To fill in the missing knowledge requires experimental data, and the next big step to achieving this is with LHC.

DESIGN The LHC is the world’s largest and highestenergy particle accelerator. The collider is contained in a circular tunnel, with a circumference of 27 kilometres (17 mi), at a depth ranging from 50 to 175 metres (160 to 570 ft) underground.

The 3.8-metre (12 ft) wide concretelined tunnel, constructed between 1983 and 1988, was formerly used to house the Large Electron–Positron Collider. It

crosses the border between Switzerland and France at four points, with most of it in France. Surface buildings hold ancillary equipment such as compressors, ventilation equipment, control electronics and refrigeration plants.

The collider tunnel contains two adjacent parallel beam pipes that intersect at four points, each containing a proton beam, which travel in opposite directions around the ring. Some 1,232 dipole magnets keep the beams on their circular path, while an additional 392 quadrupole magnets are used to keep the beams focused, in order to maximize the chances of interaction between the particles in the four intersection points, where the two beams will cross. In total, over 1,600 superconducting magnets are installed, with most weighing over 27 tonnes. Approximately 96 tonnes of liquid helium is needed to keep the magnets at their operating temperature of 1.9 K (271.25 °C), making the LHC the largest cryogenic facility in the world at liquid helium temperature. Superconducting quadrupole electromagnets are used to direct the beams to four intersection points, where interactions between accelerated protons will take place.

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PURPOSE Physicists hope that the LHC will help answer the most fundamental questions in physics, questions concerning the basic laws governing the interactions and forces among the elementary objects, the deep structure of space and time, especially regarding the intersection of quantum mechanics and general relativity, where current theories and knowledge are unclear or break down altogether.

These issues include, at least: Is the Higgs mechanism for generating elementary particle masses via electroweak symmetry breaking indeed realised in nature? It is anticipated that the collider will either demonstrate or rule out the existence of the elusive Higgs

boson(s), finishing the Standard Model.

Is supersymmetry, an extension of the Standard Model and PoincarĂŠ symmetry, realised in nature, implying that all known particles have supersymmetric partners?

This could possibly clear up the long mystery of dark matter.

Are there extra dimensions, as predicted by various models inspired by string theory, and can we detect them?

Other questions are: Are electromagnetisms, the strong nuclear force and the weak nuclear force just different manifestations of a single unified force, as predicted by various Grand Unification Theories?

Why is gravities magnitude weaker than the other three fundamental forces?

Are there additional sources of quark flavour violation beyond those already predicted within the Standard Model?

Why are there apparent violations between matter and antimatter?

Fig. 2 A simulated event in the CMS detector, featuring the appearance of the Higgs boson.

SUPERSYMMETRY 20th century physics has seen two major

On the other hand, Einstein’s famous paradigm shifts in the way we understand equation says that mass of a particle Mother Nature. One is quantum mechan- determines the energy of the particle ics, and the other is relativity. Between at rest. For an electron, its rest energy the two, called quantum field theory, is known to be 0.511 MeV. For this given conceived an enfant terrible, namely amount of energy, it cannot afford to anti-matter. As a result, the number of “pack” itself into a size smaller than the elementary particles doubled. We believe size of a nucleus. Classical theory of electhat 21st century physics is aimed at yet tromagnetism is not a consistent theory another level of marriage, quantum mebelow this distance. However, it is known chanics and general relativity, Einstein’s that the electron is at least ten thousand theory of gravity. The couple has not times smaller than that. been getting along very well, resulting in mathematical inconsistencies, meaningWhat saved the crisis was the existence less infinities, and negative probabilities. of anti-matter, positron. In quantum meThe key to success may be in supersymchanics, it is possible to “borrow” energy metry, which doubles the number of within the time interval allowed by the particles once more. uncertainty principle. Once there exists Why was anti-matter needed? One anti-matter, which can annihilate matter reason was to solve a crisis in the 19th or be created with matter, what we concentury physics of classical electromagsider to be an empty vacuum undergoes netism. An electron is, to the best of our a fluctuation to produce a pair of elecknowledge, a point particle. Namely, it tron and positron together with photon, has no size, yet an electric charge. A annihilating back to vacuum within the charged particle inevitably produces an time interval allowed by the uncertainty electric potential around it, and it also principle. In addition to the effect of the feels the potential created by itself. This electric potential on itself, the electron leads to an infinite “self-energy” of the can annihilate with a positron in the electron. In other words, it takes substan- fluctuation, leaving the electon originally tial energy to “pack” all the charge of an in the fluctuation to materialize as a real electron into small size. electron. It turns out, these two contribu-

tions to the energy of the electron almost nearly cancel with each other. The small size of the electron was made consistent with electromagnetism thanks to quantum mechanics and anti-matter.

THE SUPERSEMMETRIC STANDARD MODEL Incorporating supersymmetry into the Standard Model requires doubling the number of particles since there is no way that any of the particles in the Standard Model can be superpartners of each other. With the addition of new particles, there are many possible new interactions.

The simplest possible supersymmetric model consistent with the Standard Model is the Minimal Supersymmetric Standard Model (MSSM) which can include the necessary additional new particles that are able to be superpartners of those in the Standard Model.

One of the main motivations for SUSY comes from the quadratically divergent contributions to the Higgs mass squared.

The quantum mechanical interactions of the Higgs boson causes a large renormalization of the Higgs mass and unless

there is an accidental cancellation, the natural size of the Higgs mass is the highest scale possible. This problem is known as the hierarchy problem. Supersymmetry reduces the size of the quantum corrections by having automatic cancellations between fermionic and bosonic Higgs interactions. If supersymmetry is restored at the weak scale, then the Higgs mass is related to supersymmetry breaking which can be induced from small non-perturbative effects explaining the vastly different scales in the weak interactions.

In many supersymmetric Standard Models there is a heavy stable particle (such as neutralino) which could serve as a Weakly interacting massive particle (WIMP) dark matter candidate. The existence of a supersymmetric dark matter candidate is closely tied to R-parity.

The standard paradigm for incorporating supersymmetry into a realistic theory is to have the underlying dynamics of the theory be supersymmetric, but the ground state of the theory does not respect the symmetry and supersymmetry is broken spontaneously. The supersymmetry break can not be done perma-

Cancellation of the Higgs boson quadratic mass renormalization between fermionic top quark loop and scalar stop squark tadpole Feynman diagrams in a supersymmetric extension of the Standard Model

10 constraint on this new sector is that it must break supersymmetry permanently and must give superparticles TeV scale masses. There are many models that can do this and most of their details do not currently matter. In order to parameterize the relevant features of supersymmetry breaking, arbitrary soft SUSY breaking terms are added to the theory which temporarily break SUSY explicitly but could never arise from a complete theory of supersymmetry breaking.

SUPERSEMMETRIC QUANTUM MECHANICS Supersymmetric quantum mechanics adds the SUSY superalgebra to quantum mechanics as opposed to quantum field theory. Supersymmetric quantum mechanics often comes up when studying the dynamics of supersymmetric solitons and due to the simplified nature of having fields only functions of time (rather than space-time), a great deal of progress has been made in this subject and is now studied in its own right.

SUSY quantum mechanics involves pairs

of Hamiltonians which share a particular mathematical relationship, which are

called partner Hamiltonians. (The potential energy terms which occur in the Hamiltonians are then called partner potentials.) An introductory theorem shows that for every eigenstate of one Hamiltonian, its partner Hamiltonian has a corresponding eigenstate with the same energy. This fact can be exploited to deduce many properties of the eigenstate spectrum. It is analogous to the original description of SUSY, which referred to bosons and fermions. We can imagine a “bosonic Hamiltonian”, whose eigenstates are the various bosons of our theory. The SUSY partner of this Hamiltonian would be “fermionic”, and its eigenstates would be the theory’s fermions. Each boson would have a fermionic partner of equal energy.

SUSY concepts have provided useful extensions to the WKB approximation. In addition, SUSY has been applied to nonquantum statistical mechanics through the Fokker-Planck equation.

THE BIG BANG The Big Bang is the cosmological model of the initial conditions and subsequent development of the Universe that is supported by the most comprehensive and accurate explanations from current scientific evidence and observation. As used by cosmologists, the term Big Bang generally refers to the idea that the Universe has expanded from a primordial hot and dense initial condition at some finite time in the past (best available measurements in 2009 suggest that the initial conditions occurred around 13.3 to 13.9 billion years ago, and continues to expand to this day.

Georges Lemaître proposed what became known as the Big Bang theory of the origin of the Universe, although he called it his “hypothesis of the primeval atom”. The framework for the model relies on Albert Einstein’s general relativity and on simplifying assumptions (such as homogeneity and isotropy of space).

The governing equations had been formulated by Alexander Friedmann. After Edwin Hubble discovered in 1929 that the distances to far away galaxies were generally proportional to their redshifts, as suggested by Lemaître in 1927, this observation was taken to indicate that all

an apparent velocity directly away from our vantage point: the farther away, the higher the apparent velocity. If the distance between galaxy clusters is increasing today, everything must have been closer together in the past. This idea has been considered in detail back in time to extreme densities and temperatures, and large particle accelerators have been built to experiment on and test such conditions, resulting in significant confirmation of the theory, but these accelerators have limited capabilities to probe into such high energy regimes. Without any evidence associated with the earliest instant of the expansion, the Big Bang theory cannot and does not provide any explanation for such an initial condition; rather, it describes and explains the general evolution of the Universe since that instant. The observed abundances of the light elements throughout the cosmos closely match the calculated predictions for the formation of these elements from nuclear processes in the rapidly expanding and cooling first minutes of the Universe, as quantitatively detailed according to Big Bang nucleosynthesis.

Fred Hoyle is credited with coining the term Big Bang during a 1949 radio broadcast. It is popularly reported that Hoyle,

who favored an alternative “steady state� cosmological model, intended this to be pejorative, but Hoyle explicitly denied this and said it was just a striking image meant to highlight the difference between the two models. Hoyle later helped considerably in the effort to understand stellar nucleosynthesis, the nuclear pathway for building certain heavier elements from lighter ones. After the discovery of the cosmic microwave background radiation in 1964, and especially when its spectrum (i.e., the amount of radiation measured at each wavelength) sketched out a blackbody curve, most scientists were fairly convinced by the evidence that some Big Bang scenario must have occurred.

COMMON MISCONCEPTIONS There are many misconceptions surrounding the Big Bang theory. For example, we tend to imagine a giant explosion. Experts however say that there was no explosion; there was (and continues to be) an expansion. Rather than imagining a balloon popping and releasing its contents, imagine a balloon expanding: an infinitesimally small balloon expanding to the size of our current universe. Another misconception is

According to the Big Bang model, the Universe expanded from an extremely dense and hot state and continues to expand today. A common analogy explains that space itself is expanding, carrying galaxies with it, like raisins in a rising loaf of bread.

EVIDENCE OF THE THEORY

Artist rendition of the Big Bang Theory.

as a little fireball appearing somewhere in space. According to the many experts however, space didn’t exist prior to the Big Bang. Back in the late ‘60s and What are the major evidences which early ‘70s, when men first walked upon support the Big Bang theory? First we are the moon, “three British astrophysicists, reasonably certain that the universe had Steven Hawking, George Ellis, and Roger a beginning. Second, galaxies appear to Penrose turned their attention to the be moving away from us at speeds proTheory of Relativity and its implications portional to their distance. This is called regarding our notions of time. In 1968 and “Hubble’s Law,” named after Edwin Hubble 1970, they published papers in which they (1889-1953) who discovered this phenomextended Einstein’s Theory of General enon in 1929. This observation supports Relativity to include measurements of the expansion of the universe and sugtime and space. According to their calcu- gests that the universe was once comlations, time and space had a finite begin- pacted. Third, if the universe was initially ning that corresponded to the origin of very, very hot as the Big Bang suggests, matter and energy.” The singularity didn’t we should be able to find some remnant appear in space; rather, space began of this heat. Radioastronomers Arno inside of the singularity. Prior to the sinPenzias and Robert Wilson discovered a gularity, nothing existed, not space, time, 2.725 degree Kelvin Cosmic Microwave matter, or energy - nothing. So where and Background radiation which pervades the in what did the singularity appear if not observable universe. Thought to be the in space? We don’t know. We don’t know remnant which scientists were looking where it came from, why it’s here, or even for. Finally, the abundance of the “light where it is. All we really know is that we are elements” Hydrogen and Helium found in inside of it and at one time it didn’t exist the observable universe are thought to and neither did the human race. support the Big Bang model.

HIGGS BOSON AND THE GOD PARTICLE Peter Ware Higgs , born on May 29 1929, is an English theoretical physicist and an emeritus professor at the University of Edinburgh.

He is best known for his 1960s proposal of broken symmetry in electroweak theory, explaining the origin of mass of elementary particles in general and of the W and Z bosons in particular. This so-called Higgs mechanism, which had several inventors besides Higgs, predicts the existence of a new particle, the Higgs boson (often described as “the most soughtafter particle in modern physics�). Although this particle has not turned up in accelerator experiments so far, the Higgs mechanism is generally accepted as an important ingredient in the Standard Model of particle physics, without which particles would have no mass.

Dr. Higgs has been honored with a number of awards in recognition of his work, including the 1997 Dirac Medal and Prize for outstanding contributions to theoretical physics from the Institute of Physics, the 1997 High Energy and Particle Physics Prize by the European Physical Society, the 2004 Wolf Prize in Physics, and the 2010 J. J. Sakurai Prize for Theoretical Particle Physics.

EARLY LIFE, EDUCATION AND CAREER

Johannes Kepler was the first to give an accurate description of the orbits of the planets, and by doing so; he was the first to describe gravitational mass.

Higgs was born in Wallsend, Newcastle upon Tyne. His father was a sound engineer with the BBC, and as a result of childhood asthma, together with the family moving around because of his father’s job, and later the Second World War, Higgs missed some early schooling and was taught at home. When his father relocated to Bedford, Higgs stayed behind with his mother in Bristol, and was largely raised there. He attended that city’s Cotham Grammar School, where he was inspired by the work of one of the school’s alumni, Paul Dirac, a founder of the field of quantum mechanics.

At the age of 17, Higgs moved to City of London School, where he specialized in mathematics, then to King’s College London where he graduated with a first class honours degree in Physics, a masters degree, and Ph.D. He became a Senior Research Fellow at the Edinburgh University, then held various posts at University College London and Imperial College London before becoming a temporary lecturer in Mathematics at University College London. He returned to Edinburgh University in 1960 to take up the post

of Lecturer in Mathematical physics, allowing him to settle in the city he had fallen in love with after hitch-hiking to the Edinburgh Fringe festival as a student.

Dr. Higgs was promoted to a personal chair of Theoretical Physics at Edinburgh in 1980. He became a fellow of the Royal Society in 1983, was awarded the Rutherford Medal and Prize in 1984, and became a fellow of the Institute of Physics in 1991.

He retired in 1996 and became Emeritus professor at the University of Edinburgh.

WORK IN THEORETICAL PHYSICS It was at Edinburgh that he first became interested in mass, developing the idea that particles were massless when the universe began, acquiring mass a fraction of a second later, as a result of interacting with a theoretical field now known as the Higgs field. Higgs postulated that this field permeates space, giving all elementary subatomic particles that interact with it their mass. While the Higgs field is postulated to confer mass on quarks and leptons, it represents only a tiny portion of the masses of other subatomic particles, such as protons and neutrons.

19 In these, gluons that bind quarks together confer most of the particle mass.

The original basis of Higgs’ work came from the Japanese-born theorist and Nobel Prize winner Yoichiro Nambu, from the University of Chicago. Professor Nambu had proposed a theory known as Spontaneous symmetry breaking based on what was known to happen in Superconductivity in condensed matter. However, the theory predicted massless particles, a clearly incorrect prediction.

Higgs wrote a short paper exploiting a loophole in Goldstone’s theorem that was published in Physics Letters, a European physics journal, in 1964.

Higgs wrote a second paper describing a theoretical model (now called the Higgs mechanism) but the paper was rejected (the editors of Physics Letters felt that it was “of no obvious relevance to physics”). Higgs wrote an extra paragraph and sent his paper to Physical Review Letters, another leading Physics journal, where it was published later that year. Other physicists, Robert Brout and Francois Englert and Gerald Guralnik, C. R. Hagen, and Tom Kibble had reached the same conclusion independently about the same time. The three papers written on

this boson discovery by Higgs, Guralnik, Hagen, Kibble, Brout, and Englert were each recognized as milestone papers by Physical Review Letters 50th anniversary celebration. While each of these famous papers took similar approaches, the contributions and differences between the 1964 PRL Symmetry Breaking papers are noteworthy. Nobelist Philip Anderson also claims to have “invented” the “Higgs” boson as far back as 1962.

Higgs is reported to be displeased that the particle is nicknamed the “God particle”—although Higgs is an atheist, he is afraid the term “might offend people who are religious”. This nickname for the Higgs boson is usually attributed to Leon Lederman, but it is actually the result of Lederman’s publisher’s censoring. Originally Lederman intended to call it “the goddamn particle”,

NATURE OF BLACK HOLES A black hole is an object that is so compact (in other words, has enough mass in a small enough volume) that its gravitational force is strong enough to prevent light or anything else from escaping. It is called “black” because it absorbs all the light that hits it, reflecting nothing, just like a perfect black body in thermodynamics. The name “black hole” was introduced by John Archibald Wheeler in 1967. It stuck, and has even become a common term for any type of mysterious bottomless pit. Physicists and mathematicians have found that space and time near black holes have many unusual properties.

Because of this, black holes have become a favorite topic for science fiction writers. However, black holes are not fiction. They form whenever massive but otherwise normal stars die. We cannot see black holes, but we can detect material falling into black holes and being attracted by black holes. In this way, astronomers have identified and measured the mass of many black holes in the Universe through careful observations of the sky. We now know that our Universe is quite literally filled with billions of black holes.

FORMATION OF BLACK HOLES A black hole is born when an object becomes unable to withstand the compressing force of its own gravity. Many objects (including our Earth and Sun) will never become black holes. Their gravity is not sufficient to overpower the atomic and nuclear forces of their interiors, which resist compression. But in more massive objects, gravity ultimately wins.

Stellar-mass black holes are born with a bang. They form when a very massive star (at least 25 times heavier than our Sun) runs out of nuclear fuel. The star then explodes as a supernova. What remains is a black hole, usually only a few times heavier than our Sun since the explosion has blown much of the stellar material away. We know less about the birth of supermassive black holes, which are much heavier than stellar-mass black holes and live in the centers of galaxies. One possibility is that supernova explosions of massive stars in the early Universe formed stellar-mass black holes that, over billions of years, grew supermassive.

A single stellar-mass black hole can grow rapidly by consuming nearby stars and gas, often in plentiful supply near the galaxy center. The black hole may also grow through mergers with other black holes that drift to the galactic center during collisions with other galaxies.

Three physicists have reexamined the math for the creation of tiny black holes in the Switzerland-based LHC, and determined that they won’t simply evaporate in a millisecond as had previously been predicted.

Artist’s depiction of the accretion of a thick cosmic dust ring turning into a supermassive black hole.

INSTRUMENTS USED TO FIND BLACK HOLES? When our eyes look at the heavens we see the visible light from stars and other objects in the Universe. Thousands of years ago astronomers in Greece and other ancient cultures already built a detailed understanding of the night sky.

Many names and concepts then developed are still in use today. However, our human eyes are actually not very sensitive and modern astronomers use

sophisticated telescopes to study the Universe.The telescopes used by astronomers do not just study visible light.

While visible light is the type of ‘electromagnetic radiation’ that our eyes can see, there are many other types of such radiation. Different types of radiation are characterized by different wavelengths. If the wavelength is much shorter than that of visible light we speak about X-rays.

We encounter X-rays often in our daily lives, for example at the hospital or during security screening. If the wavelength

25 is much larger than that of visible light we speak about radio waves. We encounter radio waves often in our daily lives, for example in radios and cell phones.The black holes in the Universe do not emit any detectable type of light. However, astronomers can still find them and learn a lot about them. They do this by measuring the visible light, X-rays and radio waves emitted by material in the immediate environment of a black hole. For example, when a normal star orbits around a black hole we can measure the speed of the star by studying the visible light that it emits. Knowledge of this speed can be combined with the laws of gravity to prove that the star is in fact orbiting a black hole, instead of something else.

It also yields the mass of the black hole.

Alternatively, when gas orbits around a black hole it tends to get very hot because of friction. It then starts emitting X-rays and radio waves. So black holes can also often be found and studied by looking for bright sources of X-rays and radio waves in the sky.

There are many other types of electromagnetic radiation as well. Radiation that has even smaller wavelengths than Xrays is called gamma-rays. Radiation with wavelengths between those of X-rays and visible light is called ultraviolet light.

HOW DO BLACK HOLES GROW? Black holes grow in mass by capturing nearby material. Anything that enters the event horizon cannot escape the black hole’s gravity. So objects that do not keep a safe distance get swallowed into the hole. Despite their reputation, black holes will not actually suck in objects from large distances. A black hole can only capture objects that come very close to it. They’re more like Venus’ Flytraps than cosmic vacuum cleaners. For example, imagine replacing the Sun by a black hole of the same mass. Permanent darkness would fall on Earth, but the planets would continue to revolve around the black hole at the same distance and speed as they do now. None of the planets would be sucked into the black hole. Our Earth would be in danger only if it came within some 10 miles of the black hole, much less than the actual distance of Earth from the Sun (a comforting 93 million miles). The diet of known black holes consists mostly of gas and dust, which fill the otherwise empty space throughout the Universe. Black holes can also consume material torn from nearby stars. In fact, the most massive black holes can swallow stars whole. Black holes also grow by colliding and merging with other black holes.

Stellar-mass black holes can grow by pulling gas of a companion star that orbits around it.

HOW MANY BLACK HOLES ARE THERE? A very small patch of our Milky Way galaxy is in the constellation Sagittarius. Our galaxy contains some 100 billion stars and 100 million black holes.

RIGHT New discovery has resolved some mystery surrounding Omega Centauri, the largest and brightest globular cluster.

Results obtained by Hubble and the Gemini Observatory reveal that the globular cluster may have a rare intermediate-mass black hole hidden in its center, implying that is likely not a globular cluster at all, but a dwarf galaxy stripped of its outer stars.

There are so many black holes in the Universe that it is impossible to count them. It’s like asking how many grains of sand are on the beach. Fortunately, the Universe is enormous and none of its known black holes are close enough to pose any danger to Earth.

Stellar-mass black holes form from the most massive stars when their lives end in supernova explosions. The Milky Way galaxy contains some 100 billion stars.

Roughly one out of every thousand stars that form is massive enough to become a black hole. Therefore, our galaxy must harbor some 100 million stellar-mass black holes. Most of these are invisible to us, and only about a dozen have been identified. The nearest one is some 1,600 lightyears from Earth. In the region of the Universe visible from Earth, there are perhaps 100 billion galaxies. Each one has about 100 million stellar-mass black holes. And somewhere out there, a new stellar-mass black hole is born in a supernova every second.

Supermassive black holes are a million to a billion times more massive than

our Sun and are found in the centers of galaxies. Most galaxies, and maybe all of them, harbor such a black hole. So in our region of the Universe, there are some 100 billion supermassive black holes. The nearest one resides in the center of our Milky Way galaxy, 28 thousand lightyears away. The most distant we know of lives in a quasar galaxy billions of lightyears away.

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TYPES OF BLACK HOLES Black holes often look very different from each other. But this is because of variety in what happens in their surroundings.

The black holes themselves are all identical, except for three characteristic properties: the mass of the black hole (how much stuff it is made of), its spin (whether and how fast it rotates around an axis), and its electric charge. Black holes completely erase all complex properties of the objects that they swallow.

Astronomers can measure the mass of black holes by studying the material that orbits around them. So far, we have found two types of black holes: stellar-mass (just a few times heavier than our Sun) or supermassive (about as heavy as a small galaxy). But black holes might exist in other mass ranges as well. For example, recent observations suggest there may be black holes with masses between stellar-mass and supermassive black holes. Black holes can spin around an axis, although the rotation speed cannot exceed some limit. Astronomers think that many black hole in the Universe probably do spin, because the objects from which black holes form (stars for

example) generally rotate as well.

Observations are starting to shed some light on this issue, but no consensus has so far emerged. Black holes could also be electrically charged. However, they would then rapidly neutralize that charge by attracting and swallowing material of opposite polarity. Therefore astronomers believe that all black holes in the Universe are uncharged.

Theory suggests that miniature black holes might have formed in the early universe. But astronomers do not have any evidence of their existence. Miniature black holes have event horizons as small as the width of an atomic particle and might have been created during the Big Bang, the moment the universe was created. These miniature black holes contain as much matter as Mt. Everest.

Miniature black holes might have formed during the dawn of our universe. Between 10 and 20 billion years ago, all matter and energy was compressed into a single point. Then this tiny point exploded and expanded rapidly. Some parts might have expanded more rapidly than other parts, compressing some matter and squeezing it into miniature black holes.

HOW BIG IS A BALCK HOLE? All matter in a black hole is squeezed into a region of infinitely small volume, called the central singularity. The event horizon is an imaginary sphere that measures how close to the singularity you can safely get. Once you have passed the event horizon, it becomes impossible to escape: you will be drawn in by the black hole’s gravitational pull and squashed into the singularity.

The size of the event horizon (called the Schwarzschild radius, after the German physicist who discovered it while fighting in the first World War) is proportional to the mass of the black hole. Astronomers have found black holes with event horizons ranging from 6 miles to the size of our solar system. But in principle, black holes can exist with even smaller or larger horizons. By comparison, the Schwarzschild radius of the Earth is about the size of a marble. This is how much you would have to compress the Earth to turn it into a black hole. A black hole doesn’t have to be very massive.

Supermassive black holes live in the centers of galaxies.

Bigger galaxies generally have bigger black holes in them.

One Billion Solar Masses

One Million Solar Masses

No Black Hole

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Bigger Galaxies

Supermassive black holes have properties which distinguish them from lowermass classifications: The average density of a supermassive black hole (measured as the mass of the black hole divided by its Schwarzschild volume) can be very low, and may actually be lower than the density of air. This is because the Schwarzschild radius is directly proportional to mass, while density is inversely proportional to the volume. Since the volume of a spherical object (such as the event horizon of a non-rotating black hole) is directly proportional to the cube of the radius, and mass merely increases linearly, the volume increases at a greater rate than mass. Thus, average density decreases for increasingly larger radii.

A supermassive black hole is a black hole with the largest of its type in the galaxy, on the order of hundreds of thousands to billions of solar masses. Most, if not all galaxies, including the Milky Way, are believed to contain supermassive black holes at their centers.

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WHAT HAPPENS WHEN BLACK HOLES COLLIDE? Two colliding black holes send ripples through the space-time fabric of the Universe that are called gravitational waves.

It is possible for two black holes to collide.

Once they come so close that they cannot escape each other’s gravity, they will merge to become one bigger black hole.

Such an event would be extremely violent.

Even when simulating this event on powerful computers, we cannot fully understand it. However, we do know that a black hole merger would produce tremendous energy and send massive ripples through the space-time fabric of the Universe. If that happens, they are called gravitationa waves.

Nobody has witnessed a collision of black holes yet. However, there are many black holes in the Universe and it is not preposterous to assume that they might collide.

In fact, we know of galaxies in which two supermassive black holes move dangerously close to each other. Theoretical models predict that these black holes will spiral toward each other until they eventually collide. Gravitational waves have never been directly observed. Although, they are a fundamental prediction of Einstein’s theory of general relativity. Detecting them would provide an important test of our understanding of gravity. It

would also provide important new insights into the physics of black holes. Large instruments capable of detecting gravitational waves from outer space have been built in recent years. Even more powerful instruments have begun construction.

ATLAS ANNUAL REPORT 2009

A YEAR AT ATLAS The year 2009 was one of the most eventful in the history of ATLAS. From January, the news from the LHC and the experiments started to contain magic words like ‘final piece installed’, ‘last component in place’, ‘first measurement’. While the four major experiments were finalizing their equipment, the machine technicians were forging ahead to get ready for the first injection in the beam pipes. Three major events had a big impact on the life of the Laboratory: the Open Days organized in April, the circulation of the first beams in September, and the official inauguration of the LHC in October.

At a little before 10.30 a.m. on 10 September, two dots on a colour screen in the ATLAS Control Centre marked the successful first complete turn of protons clockwise round the LHC. By the end of the day, not only had the anticlockwise beam also completed its first circuit, but it had made some 300 turns in the machine. A bunch of particles travelling round the ring is a major step. However, for an accelerator the key lies in capturing the particles with the radiofrequency system that provides the accelerating electric fields and keeping the bunches in time with the RF on the thousands of turns per second that occur during normal operation. Without the RF or if the RF system does not work properly, the bunch broadens as particles stray from the perfect orbit round the machine. The LHC showed perfect behaviour with bunches passing the same point in synchronization with the radiofrequency, turn after turn.

AAR 37

PHYSICS AND EXPERIMENTS

39

ALICE, PROBING THE QUARK–GLUON PLASMA ALICE, probing the quark–gluon plasma.

ALICE is a heavy-ion experiment designed

to study the physics of strongly interacting matter and the quark–gluon plasma in lead–lead collisions at the LHC. The ALICE Collaboration currently includes more than 1000 physicists and senior engineers from both nuclear and high-energy physics from about 100 institutions in some 30 countries. Some new institutes from the US and South Korea joined ALICE in 2008, while the associate members IPE Karlsruhe (Germany) and BARC (Mumbai, India) left after completing their respective technical contributions.

ALICE consists of a central part, which

measures hadrons, eletrons, and photons, and a forward spectrometer to measure muons. The central part is embedded in the large L3 solenoid magnet and comprises an inner tracking system (ITS) of high- resolution detectors, a cylindrical time projection chamber (TPC), three particle identification arrays of time-of-flight (TOF), ring imaging Cherenkov (HMPID) and transition radiation (TRD) detectors, plus two single-arm electromagnetic calorimeters (the high-resolution photon spectrom-

eter PHOS and the large-acceptance jet calorimeter EMCAL). The forward muon arm consists of a complex arrangement of absorbers, a large dipole magnet, and 14 planes of tracking and triggering chambers. Several smaller detectors (ZDC, PMD, FMD, T0, V0) used for global event characterization and triggering are located at forward angles. An array of scintillators (ACORDE) on top of the L3 magnet is used to trigger on cosmic rays.

Most of the ALICE detectors were installed, tested, and pre- commissioned in situ during 2007. Construction and assembly continued during 2008 for detectors added later to the design (TRD, PHOS, and EMCAL). Thus, detector integration and commissioning were the main activities in 2008. Several runs with cosmic rays were performed at the beginning of the year, and from May until mid-October ALICE was operated continuously (24/7).

As far as could be verified, the performance of all subsystems is very close to (or better than) specification. During LHC commissioning in September, only a subset of detectors was switched on because the particle flux was occasionally very high during beam tuning. Nevertheless, timing of most trigger detectors was verified and adjusted with beam.The commissioning of ALICE required an

Abstract view of the CMS experiment Tracker Outer Barrel in the cleaning room.

40 LVPD extremely large effort in terms of manpower. Extrapolating from the experience with operation 24 hours per day, a nominal year of data taking would require the collaboration to provide about 17 000 shifts, as each subsystem currently requires at least one person on shift in the ALICE control room in addition to experts being on call at ATLAS. However, this need will be reduced in the course of 2009 by automating procedures and recovery operations and by combining shifts for different detector systems.

LARGEST VOLUME PARTICLE DETECTOR

The detector has cylindrical symmetry around the beam pipe, with increasingly large layers of subdetectors placed around it and endcaps to ensure hermiticity. Inner detectors, a series of thin silicon and gas detectors immersed in a solenoidal magnetic field — are used for pattern recognition, and for momentum and vertex measurements. In addition to the central solenoid, the magnet system also comprises a barrel toroid and two endcap toroids.The high granularity liquid-argon electromagnetic calorimeters and the hadronic scintillator-tile calorimeter are surrounded by the muon spectrometer, which defines the overall dimensions of the detector.

ATLAS is a general-purpose experiment

Installation in the cavern 90 m under-

for recording proton– proton collisions at the LHC. The detector design has been optimized to cover the largest possible range of LHC physics. This includes searches for Higgs bosons or alternative schemes to answer the puzzling question about the origin of mass, and searches for supersymmetric particles, and other new physics beyond the Standard Model.

There are 2800 scientific participants.

ground began in summer 2003 and culminated in 2008 with completion of the initial detector configuration. The muon chambers were the last component to be installed in July. In parallel with the installation process, testing and consolidation work for the on- and off-detector electronics and power supplies were important activities, and the detector systems were gradually brought into operation, calibrated, and tested with cosmic data. A major challenge concerned the installation of over 50 000

An abstracted view of L3 detector with muon tracks from a higgs cadidate event.

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42 CMSHWD cables, more than 3000 km in length, and more than 10 000 pipes for services.

On 16 June an historic moment occurred with the closure of the LHC beam pipe, followed in early August with the successful bake-out of the beam pipe. The latter operation was particularly critical because it required the evaporative cooling system to be in full working order to protect the pixel layers from overheating.

The evaporative cooling plant had suffered a major failure of its compressors at the beginning of May 2008, and the repair and cleaning of the plant dictated the critical path for the closure of the detector. In 2008 several dedicated running periods with cosmic rays were used to test and calibrate detectors, including the trigger and data-acquisition systems.

The detector was largely operational for the LHC start-up in September, as was the distributed computing infrastructure.

The first beam-related events were successfully recorded and reconstructed and were used very efficiently for initial timing adjustments. Following the LHC incident on Sept. 19th, the full detector has essentially been in continuous operation in cosmic-ray data collection mode. These runs are very valuable for improving monitoring and data-quality procedures, as well as for initial global alignments.

CMS, HEAVY-WEIGHT DETECTOR CMS, the heavy-weight detector CMS (Compact Muon Solenoid), is a

general- purpose detector used to study a large range of physical phenomena produced by particle collisions at the LHC. In a unique strategy, the detector was assembled above ground concurrently with the excavation of the underground cavern. The CMS Collaboration consists of over 2500 scientists and engineers from over 180 institutes in 38 countries.

The main volume of the CMS detector is a cylinder, 21 m long and 16 m in diameter, weighing in total 12 500 t. The tracking volume is defined by a cylinder of length 6 m and a diameter of 2.6m.

About 210 m2 of silicon microstrip detectors (around 10 million channels) provide the required granularity and precision in the bulk of the tracking volume; pixel detectors placed close to the interaction region improve measurements of the track impact parameters and allow accurate reconstruction of secondary vertices. The tracking system is placed inside the huge superconducting magnet, 13 m long and 6 m in diameter, which will oper-

Size: 21 m long, 15 m wide and 15 m high.

Weight: 12 500 tonnes Design: barrel plus end caps Location: Cessy, France.

ate at 3.8 T. The magnet is used to determine the momentum of charged particles from the curved paths they follow in the magnetic field. The magnet return yoke acts as the principal support structure for all the detector elements. Muons are identified and measured in four identical muon stations inserted in the return yoke.

Each muon station consists of many planes of aluminium drift tubes in the barrel region and cathode-strip chambers. With extensive tests of reconstruc-

tion and physics analysis software and of the Worldwide LHC Computing Grid.

In early Sept., after almost 20 years of design and construction, CMS started taking data with LHC beams. The solenoid and the inner tracking system were switched off awaiting stable beams. The rest of the detector subsystems took good-quality data and reacted quickly to changing beam conditions. Measurements of the fringe fields in the cavern showed them to be higher than expected.

LHCf,b STUDYING HIGH ENERGY COSMIC RAYS

TRACKING DOWN ANTIMATTER

LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forward direction in LHC collisions. The physics motivation for LHCf is the calibration of the hadronic interaction models that are used in very highenergy cosmic-ray physics. Because the 14 TeV of proton– proton collisions at the LHC corresponds to 1017 eV equivalent energy in the laboratory system, the LHCf measurements will provide a crucial calibration point for studying the origin and composition of very high-energy cosmic rays. LHCf makes use of two independent detectors, installed on either side of the interaction point, at a distance of 140 m away from it. Both detectors were installed in the LHC tunnel during January and February 2008. Control and data collection were successfully performed from the particle detector counting room via signal cables and optical fibres 200 m long. In May 2008, a dedicated control room for LHCf was prepared on the surface at Point 1, and all LHCf operation became available from the dedicated control room before the first beam circulation in the LHC in September.

The main purpose of the Large Hadron Collider beauty (LHCb) experiment is to investigate the phenomenon known as CP violation in the decay of particles containing b and anti-b quarks, collectively known as ‘B mesons’. CP violation is a necessary ingredient in explaining the total absence of antimatter in the Universe. Rather than flying out in all directions, B mesons formed by the colliding proton beams (and the particles they decay into) stay close to the line of the beam pipe. This is reflected in the design of the detector, which stretches for 20 m along the beam pipe, with its subdetectors stacked behind each other like books on a shelf. The point where the beams collide, and B mesons are produced, is inside the VErtex LOcator (VELO) subdetector. With its 84 half-moonshaped silicon sensors, each connected to electronics, the VELO can locate the position of B particles to within 10 m.

47 Size: two detectors, each measures 30 cm long, 80 cm high, 10 cm wide Weight: 40 kg each Location: Meyrin, SUI

ACCELERATORS It is 10.26 a.m. on 10 September 2008.

In a packed ATLAS Control Centre, all eyes are on the monitor screens. The LHC project leader, Lyn Evans, has been providing a commentary on the progress of the beam for the past hour, as operators attempt, for the first time, to get the protons to travel around the whole ring. Then, two bright spots of light suddenly show up on the screen, and are greeted with thunderous applause. The most powerful accelerator has worked for the first time after years of preparation, construction and installation, which culminated in the feverish activity of the first eight months of 2008. Lyn Evans’s expression of joy will travel around the world via the television.

CLOSING THE RING The last remaining machine parts were fitted at the start of 2008, with the installation of the final components for the ‘warm’ parts of the accelerator. The LHC consists primarily of superconducting magnets that operate at a very low temperature, but 12% of the magnets use normal conductors and operate at ambient temperature (which makes them warm, by comparison with the cryogenic

magnets). These resistive magnets are located in the straight sections of the accelerator, situated just before and just after the experiments, and in the areas where the beams are injected or extracted. In the warm zones there are also 88 collimators, whose installation was finished in 2008. The collimators are an essential part of machine protection, as they absorb particles that stray from the beam path. Such stray particles could collide with the superconducting magnets, generating heat that would rob the magnets of their superconducting properties and bring the machine to a halt. The jaw-like, metre-long collimators are made of fibre-reinforced graphite.

When the jaws close, they leave a gap of only 3 mm for the beam to pass through, and any particles that stray beyond that are absorbed. Numerous tests were done in 2008 to ensure that the collimators were working properly. The circulation of the beam on Sept. 10 was a full-scale test before being allowed to go all the way around the ring, the beam advanced in stages, with the collimators stopping it in different places. Twenty additional collimators were installed in December.

“The speed of the LHC’s first operation with beam is testimony to years of painstaking preparation and to the skill of the teams involved in building and running ATLAS’s accelerator complex.”

-Robert Aymar, ATLAS Bulletin, 6 October 2008.

50 EVBC Cryogenic thermometers installed on the vacuum side of interconnection QBQI.11L1

tor make use of a very pure vacuum as thermal insulation. Next, the vacuum instrumentation and the interlock system that connects the vacuum to the cryogenic system and the accelerator’s protection system were commissioned. In all, 300 valves and over 1500 gauges and ion pumps had to be checked, along with their interfaces to the other LHC systems.

EXTRATERRESTRIAL VACUUM The final components of the vacuum chambers were also installed in 2008.

On 16 June the LHC ring was completed, with the last section of vacuum chamber put in place inside the ATLAS experiment.

The experiment vacuum systems are of a special design, incorporating components made of beryllium, an element that interferes very little with particles, and having individually designed forms. The vacuum system became fully operationalbefore the end of August 2008. To let the beams circulate freely without the risk of colliding with stray molecules, a very pure vacuum was created in the 54 km of beam pipe. The pressure is reduced to 1012 mbar, roughly the pressure on the surface of the Moon. Likewise, the cryogenic lines and the cold parts of the accelera-

THE BIG CHILL Meanwhile, the rest of the machine totalling 24 km out of its 27 km length was being cooled down, sector by sector. To give the beams their curved trajectory and focus them, the LHC largely consists of superconducting magnets that operate at 1.9 K (271°C), less than two degrees above absolute zero. On 18 August, after months of determined efforts, the entire accelerator reached 1.9 K, making the LHC the biggest cryogenic system in the world. In all, 10k tonnes of nitrogen and 130 tonnes of liquid helium were needed to cool down the 37k tonnes of equipment that makes up the cold mass of the LHC. The machine’s cryogenic instrumentation, including some 10k thermometers, was also commissioned to allow precision control of the cryogenic processes.

ALIGNMENT TARGET MAIN QUADRIPOLE BUS-BARS HEAT EXCHANGER PIPE SUPERINSULATION SUPERCONDUCTING COILS BEAM PIPE VACCUUM VESSEL BEAM SCREEN AUXILIARY BUS-BARS SHRINKING CYLINDER HE I-VESSEL THERMAL SHIELD NON-MAGNETIC COLLARS IRON YOKE DIPOLE BUS-BARS SUPPORT POST

LHC DIPOLE: STANDARD CROSS SECTION Diagram showing the cross-section of an LHC dipole magnet with cold mass and vacuum chamber.

THE BIG ADVENTURE

LIOE 53 The quadrupoles have a dual opening configuration and are combined in the same magnetic and cryogenic structure. Main characteristics of the magnets are: a length of 3.2m; an opening of 56 mm; and a field strength gradient of 223T/m.

THE LAB IS OPEN: EXPERIENCE IT In addition to the thousands of visitors that came specifically on the Open Days held in April, the Laboratory welcomed as usual more than 25 000 visitors on site throughout the year. The transition towards the exploitation of new non-LHC visiting points was particularly smooth, with no noticeable decrease in the enthusiasm. of the public visitors.

The professionalism of the guides who

welcome the visitors and show them around the experimental areas. The year also saw a record number of 160 visits for VIPs, including one head of state, heads of government, ministers, and members of parliament from Member States and non-Member States. During the month of October alone there were 43 visits in addition to the 42 national delegations that attended the LHC inauguration on 21 October. Journalists also reached recordbreaking numbers: more than 700 visited the experimental areas in 2008, and

54 NATTT more than 140 were present on site for the LHC first-beam day in September.This resulted in an unprecedented media coverage for the Laboratory. Throughout the year, the Globe of Science and Innovation continued to fulfil its role as ATLAS’s attractive link with society. In addition to various public and private events, in 2008 it hosted three exhibitions: Superconductivity magical attraction, Accelerating Nobels (realized with the contribution of the Fondation meyrinoise pour la promotion culturelle, sportive et sociale), and Big science.

A NEW APPROACH TO TECHNOLOGY TRANSFER The particle physics community, and ATLAS in particular, operates in many technical fields such as mechanics, electronics, information technology, and communication. The many innovations and new technologies that emerge can lead, via industry, to important and beneficial spin-offs. Technology transfer (TT) can be seen as the natural extension of ATLAS’s scientific programmes. Therefore, following the desire expressed in the European Strategy for Particle Physics

approved by Council in 2006, a network of TT contacts in Member States was created in June. The network brings ATLAS’s TT office and the TT offices of public research institutes in the Member States under one umbrella, with the scope of creating synergies between the Member States and harmonizing the specific characteristics of various national systems. The main mission of the network is to facilitate the access of European industry to the new technologies developed by the scientific community. The best way for improving the spin- off from particle physics research to industry and society is to take advantage of the naturally collaborative spirit of physics researchers and extend it to the field of TT. In total, in 2008, ATLAS applied for six patents and issued 20 TT contracts.

SAFETY AND ENVIRONMENT Many environmental protection activities in 2008 were focused towards finalizing and verifying the correct functioning of the systems needed to monitor the environmental impact of the LHC accelerator. Prior to the start-up, installation of the LHC Radiation Monitoring System for the Environment and Safety (RAMSES) was completed, and its instrumentation was thoroughly tested. RAMSES monitors radiation levels for radioprotection purposes at different locations of the LHC installations, as well as radiological and conventional environmental parameters in the LHC and CNGS installations. The effective functioning of RAMSES not only allows ATLAS to monitor the correct operation of its main facilities, but also represents an important tool for the exchange and comparison of data with the Host States’ authorities in. charge of radiation and environmental protection. RAMSES integrates the network of existing monitors that are placed on the site and in its vicinity for the execution of ATLAS’s Environmental Monitoring Programme.

This program aims to assess globally the environmental impact of ATLAS’s activities by continuously measuring significant environmental parameters

56 SE such as those related to radiation, atmospheric emissions, effluent water, etc. The results are periodically communicated to Switzerland and France, the Host States.

As in previous years, in 2008 the level of ATLAS’s emissions of radiation measured by the 200 or so online m onitoring stations, and cross checked by independent measurements carried out by the Host States’ authorities, remained well below the internationally recognized legal limits.

Concerning conventional releases, only one significant event occurred where the physicochemical parameters of discharged water exceeded the permitted range. This event, however, had a negligible effect on the aquatic environment.

Construction began in 2008 on a new water treatment facility on the Meyrin site.

It will be operational in late spring 2009, replacing the existing one.

The LHC start-up gave rise to many fanciful theories about the possible consequences of high-energy collisions.

In particular, rumours were rife concerning the hypothetical appearance of black holes. While it is true that certain theories predict the production of mini black holes in LHC collisions, all such theories also predict that they would decay instantaneously and have no macroscopic effect.

LHC MILESTONES 1984-2009

The LHC accelerator was originally conceived in the 1980s and approved for construction by the ATLAS Council in late 1994. Turning this ambitious scientific plan into reality proved to be an immensely complex task for ATLAS. Civil engineering work to excavate underground caverns to house the huge detectors for the experiments started in 1998. Five years later, the last cubic metre of ground was finally dug for the whole Project Origin mission.

whole Project Origin mission. Numerous state-of-the-art technologies were pushed even further to meet the accelerator’s exacting specifications and unprecedented demands.

Anticipating the colossal amount of data the LHC’s experiments would produce, a new approach to data storage, management, sharing and analysis was created in the LHC Computing Grid project.

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