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.

ATLAS, WHO ARE WE?

Fig. 1

WHAT IS PROJECT ORIGIN?

Fig.1 Project Origin, world’s largest par-ticle accelerator.

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.

PO 4

The Large Hadron Collider (LHC) is the world’s largest and highest-energy particle accelerator, intended to collide opposing particle beams of either pro-tons 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 high-energy 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 labo-ratories. September 2008, the proton beams were successfully circulated in the main ring of the LHC for the first time.

On 19 September 2008, the opera-tions were halted due to a serious fault between two superconducting bend-ing 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 mid-November 2009.

KNOWING ORIGIN 6

The LHC was built to help scientists to an-swer key unresolved questions in particle physics. The unprecedented energy it achieves may even reveal some unex-pected 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 interac-tions 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.

The LHC is the world’s largest and highest-energy 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 concrete-lined 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, ventila-tion 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 direc-tions 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 fo-cused, 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. Ap-proximately 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 tem-perature. Superconducting quadrupole electromagnets are used to direct the beams to four intersection points, where interactions between accelerated pro-tons will take place.

DESIGN

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 relativ-ity, where current theories and knowledge are unclear or break down altogether.

These issues include, at least:Is the Higgs mechanism for generat-ing 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 Poincaré 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 be-tween matter and antimatter?

WHY

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

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Fig. 2

PURPOSE

20th century physics has seen two major paradigm shifts in the way we understand Mother Nature. One is quantum mechan-ics, and the other is relativity. Between the two, called quantum field theory, conceived an enfant terrible, namely anti-matter. As a result, the number of elementary particles doubled. We believe that 21st century physics is aimed at yet another level of marriage, quantum me-chanics and general relativity, Einstein’s theory of gravity. The couple has not been getting along very well, resulting in mathematical inconsistencies, meaning-less infinities, and negative probabilities. The key to success may be in supersym-metry, which doubles the number of particles once more.

Why was anti-matter needed? One reason was to solve a crisis in the 19th century physics of classical electromag-netism. An electron is, to the best of our knowledge, a point particle. Namely, it has no size, yet an electric charge. A charged particle inevitably produces an electric potential around it, and it also feels the potential created by itself. This leads to an infinite “self-energy” of the electron. In other words, it takes substan-tial energy to “pack” all the charge of an electron into small size.

SUPERSYMMETRYOn the other hand, Einstein’s famous equation says that mass of a particle determines the energy of the particle at rest. For an electron, its rest energy is known to be 0.511 MeV. For this given amount of energy, it cannot afford to

“pack” itself into a size smaller than the size of a nucleus. Classical theory of elec-tromagnetism is not a consistent theory below this distance. However, it is known that the electron is at least ten thousand times smaller than that.

What saved the crisis was the existence of anti-matter, positron. In quantum me-chanics, it is possible to “borrow” energy within the time interval allowed by the uncertainty principle. Once there exists anti-matter, which can annihilate matter or be created with matter, what we con-sider to be an empty vacuum undergoes a fluctuation to produce a pair of elec-tron and positron together with photon, annihilating back to vacuum within the time interval allowed by the uncertainty principle. In addition to the effect of the electric potential on itself, the electron can annihilate with a positron in the fluctuation, leaving the electon originally in the fluctuation to materialize as a real 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 quan-tum 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 renor-malization of the Higgs mass and unless there is an accidental cancellation, the natural size of the Higgs mass is the high-est scale possible. This problem is known

as the hierarchy problem. Supersym-metry reduces the size of the quantum corrections by having automatic cancel-lations 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 explain-ing 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 exis-tence 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 re-spect the symmetry and supersymmetry is broken spontaneously. The supersym-metry break can not be done perma-nently by the particles of the MSSM as they currently appear. This means that there is a new sector of the theory that is responsible for the breaking. The only

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

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 me-chanics 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 po-

tential 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 de-duce 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 non-quantum statistical mechanics through the Fokker-Planck equation.

THE BIG BANGThe 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 be-came 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 relativ-ity and on simplifying assumptions (such as homogeneity and isotropy of space). The governing equations had been for-mulated 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 very distant galaxies and clusters have

an apparent velocity directly away from our vantage point: the farther away, the higher the apparent velocity. If the dis-tance between galaxy clusters is increas-ing 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 confir-mation of the theory, but these accelera-tors 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 gen-eral 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 expand-ing and cooling first minutes of the Uni-verse, as quantitatively detailed accord-ing to Big Bang nucleosynthesis.

Fred Hoyle is credited with coining the term Big Bang during a 1949 radio broad-cast. 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 consider-ably 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 sce-nario must have occurred.

COMMON MISCONCEPTIONS

There are many misconceptions surround-ing 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 ex-pansion. Rather than imagining a balloon popping and releasing its contents, imag-ine a balloon expanding: an infinitesimally small balloon expanding to the size of our current universe. Another misconception is that we tend to image the singularity

According to the Big Bang model, the Universe expand-ed 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 FOR THE THEORY

What are the major evidences which sup-port the Big Bang theory? First of all, we are reasonably certain that the universe had a beginning. Second, galaxies appear to be moving away from us at speeds proportional to their distance. This is called “Hubble’s Law,” named after Edwin Hubble (1889-1953) who discovered this phenomenon in 1929. This observation supports the expansion of the universe and suggests that the universe was once compacted. Third, if the universe was initially very, very hot as the Big Bang suggests, we should be able to find some remnant of this heat. In 1965, Radio-astronomers Arno Penzias and Robert Wilson discovered a 2.725 degree Kelvin (-454.765 degree Fahrenheit, -270.425 degree Celsius) Cosmic Microwave Back-ground radiation (CMB) which pervades the observable universe. This is thought to be the remnant which scientists were looking for. Penzias and Wilson shared in the 1978 Nobel Prize for Physics for their discovery. Finally, the abundance of the

“light elements” Hydrogen and Helium found in the observable universe are thought to support the Big Bang model.

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 early ‘70s, when men first walked upon the moon, “three British astrophysicists, Steven Hawking, George Ellis, and Roger Penrose turned their attention to the Theory of Relativity and its implications regarding our notions of time. In 1968 and 1970, they published papers in which they extended Einstein’s Theory of General Relativity to include measurements of time and space. According to their calcu-lations, time and space had a finite begin-ning that corresponded to the origin of matter and energy.” The singularity didn’t appear in space; rather, space began inside of the singularity. Prior to the sin-gularity, nothing existed, not space, time, matter, or energy - nothing. So where and in what did the singularity appear if not in space? We don’t know. We don’t know where it came from, why it’s here, or even where it is. All we really know is that we are inside of it and at one time it didn’t exist and neither did the human race.

Artist rendition of the Big Bang Theory.

HIGGS BOSON AND THE GOD PARTICLE

PETER HIGGS

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 elemen-tary 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 ex-istence of a new particle, the Higgs boson (often described as “the most sought-after particle in modern physics”). Al-though 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 num-ber of awards in recognition of his work, including the 1997 Dirac Medal and Prize for outstanding contributions to theoreti-cal 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 CAREERHiggs 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 school-ing 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 Lon-don 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 Univer-sity, then held various posts at University College London and Imperial College London before becoming a temporary lecturer in Mathematics at University Col-lege 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 Ruther-ford 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 interact-ing with a theoretical field now known as the Higgs field. Higgs postulated that this field permeates space, giving all elemen-tary 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. In these, gluons that bind quarks together confer most of the particle mass.

Johannes Kepler was the first to give an ac-curate description of the orbits of the planets, and by doing so; he was the first to describe gravita-tional mass.

The original basis of Higgs’ work came from the Japanese-born theorist and No-bel Prize winner Yoichiro Nambu, from the University of Chicago. Professor Nambu had proposed a theory known as Sponta-neous symmetry breaking based on what was known to happen in Superconductiv-ity 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 Euro-pean 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 phys-ics”). 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 con-tributions 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. Origi-nally Lederman intended to call it “the goddamn particle”,

NATURE OF BLACK HOLESA black hole is an object that is so compact (in other words, has enough mass in a small enough volume) that its gravi-tational 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 fa-vorite 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.

A black hole is born when an object becomes unable to withstand the com-pressing 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 su-permassive 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 gal-axy center. The black hole may also grow through mergers with other black holes that drift to the galactic center during collisions with other galaxies.

FORMATION OF BLACK HOLES

BIRTH OF BLACK HOLES

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 de-veloped 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 as-tronomers do not just study visible light. While visible light is the type of ‘electro-magnetic 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 dur-

Three physicists have reexamined the math

surrounding the creation of tiny black holes in the Switzerland-based LHC, and determined that they won’t simply evaporate in a millisecond as had previ-

ously been predicted.

Artist’s depiction of the accretion of a thick cosmic

dust ring turning into a supermassive black hole.

ing security screening. If the wavelength 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 mea-suring the visible light, X-rays and radio waves emitted by material in the immedi-ate environment of a black hole. For ex-ample, 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 be-cause 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 electro-magnetic radiation as well. Radiation that has even smaller wavelengths than X-rays 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 con-sists 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 col-liding and merging with other black holes.

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

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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 su-pernova 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.

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 larg-est 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 cen-ter, implying that is likely not a globular cluster at all, but a dwarf galaxy stripped of its outer stars.

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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 identi-cal, except for three characteristic prop-erties: 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 com-pletely 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. Ob-

servations 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 cre-ated. 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.

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TYPES OF BLACK HOLES

.

Bigger Galaxies

No Black Hole

One Million

Solar Masses

One Billion Solar

Masses

HOW BIG IS A BLACK 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 hori-zons 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 Schwar-zschild 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.

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.

Supermassive black holes have proper-ties which distinguish them from lower-mass 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 Schwar-zschild radius is directly proportional to mass, while density is inversely propor-tional 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 lin-early, the volume increases at a greater rate than mass. Thus, average density decreases for increasingly larger radii of black holes (due to volume increasing much faster than mass).

43 BLACK HOLES

44

WHAT HAPPENS WHEN BLACK HOLES COLLIDE?

It is possible for two black holes to collide. Once they come so close that they can-not 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 pow-erful computers, we cannot fully under-stand 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 gravita-tiona waves.

Nobody has witnessed a collision of black holes yet. However, there are many black holes in the Universe and it is not prepos-terous to assume that they might collide. In fact, we know of galaxies in which two supermassive black holes move danger-ously close to each other. Theoretical models predict that these black holes will spiral toward each other until they even-tually collide. Gravitational waves have never been directly observed. Although, they are a fundamental prediction of Einstein’s theory of general relativity. De-tecting 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 in-struments capable of detecting gravita-tional waves from outer space have been built in recent years. Even more powerful instruments have begun construction.

Two colliding black holes send ripples through the space-time fabric of the Universe that are called gravitational waves.

45

ATLASANNUALREPORT2009

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 thou-sands 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 syn-chronization with the radiofrequency, turn after turn.

A YEAR AT ATLAS AAR 12

PHYSICS AND EXPERIMENTS

ALICE, probing the quark–gluon plasma. ALICE is a heavy-ion experiment designed to study the physics of strongly interact-ing matter and the quark–gluon plasma in lead–lead collisions at the LHC. The AL-

ICE Collaboration currently includes more than 1000 physicists and senior engineers from both nuclear and high-energy phys-ics 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 respec-tive technical contributions.

ALICE consists of a central part, which measures hadrons, eletrons, and pho-tons, and a forward spectrometer to measure muons. The central part is em-bedded 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 ar-rays 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 in-stalled, tested, and pre- commissioned in situ during 2007. Construction and as-sembly continued during 2008 for detec-tors added later to the design (TRD, PHOS,

and EMCAL). Thus, detector integration and commissioning were the main activi-ties 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 perfor-mance 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. Neverthe-less, 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 (TOB) in the clean-ing room.

14

ALICE, PROBING THE QUARK–GLUON PLASMA

extremely large effort in terms of man-power. Extrapolating from the experience with operation 24 hours per day, a nomi-nal year of data taking would require the collaboration to provide about 17 000 shifts, as each subsystem currently re-quires 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.

ATLAS is a general-purpose experiment for recording proton– proton collisions at the LHC. The detector design has been optimized to cover the largest pos-sible 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.

The detector has cylindrical symmetry around the beam pipe, with increas-ingly large layers of subdetectors placed around it and endcaps to ensure her-miticity. 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 calorim-eters and the hadronic scintillator-tile calorimeter are surrounded by the muon spectrometer, which defines the overall dimensions of the detector.

Installation in the cavern 90 m under-ground began in summer 2003 and cul-minated 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 consoli-dation 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 con-cerned the installation of over 50 000

LVPD15

LARGEST VOLUME PARTICLE DETECTOR

μ+μ-

e+

e-

, 0*

μ+

o

bb

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

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 suc-cessful bake-out of the beam pipe. The latter operation was particularly critical because it required the evaporative cool-ing system to be in full working order to protect the pixel layers from overheating. The evaporative cooling plant had suf-fered 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 run-ning 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 suc-cessfully recorded and reconstructed and were used very efficiently for initial timing adjustments. Following the LHC incident on Sept. 19th, the full detector has es-sentially 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, 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 as-sembled above ground concurrently with the excavation of the underground cav-ern. 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 detec-tors (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 ac-curate reconstruction of secondary verti-ces. The tracking system is placed inside the huge superconducting magnet, 13 m long and 6 m in diameter, which will oper-

CMSHWD17

CMS, HEAVY-WEIGHT DETECTOR

ate at 3.8 T. The magnet is used to deter-mine 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 cham-bers. 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 sole-noid 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. Measure-ments of the fringe fields in the cavern showed them to be higher than expected.

Size: 21 m long, 15 m wide and 15 m high.Weight: 12 500 tonnes Design: barrel plus end caps Location: Cessy, France.

LHCf,b

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 contain-ing 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 re-flected 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 pro-duced, is inside the VErtex LOcator (VELO) subdetector. With its 84 half-moon-shaped silicon sensors, each connected to electronics, the VELO can locate the posi-tion of B particles to within 10 m.

LHCf is an experiment dedicated to the measurement of neutral particles emitted in the very forward direction in LHC colli-sions. The physics motivation for LHCf is the calibration of the hadronic interac-tion models that are used in very high- energy 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 cali-bration 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 Janu-ary 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 con-trol 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 circu-lation in the LHC in September.

STUDYING HIGHENERGY COSMIC RAYS

TRACKING DOWN ANTIMATTER

Size: two detectors, each mea-sures 30 cm long, 80 cm high, 10 cm wide Weight: 40 kg each Location: Meyrin, Switzerland

22

ACCELERATORSIt 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 opera-tors attempt, for the first time, to get the protons to travel around the whole ring. Then, two bright spots of light sud-denly show up on the screen, and are greeted with thunderous applause. The most powerful accelerator has worked for the first time after years of prepara-tion, 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 on tv.

The last remaining machine parts were fitted at the start of 2008, with the in-stallation of the final components for the ‘warm’ parts of the accelerator. The LHC consists primarily of superconduct-ing 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 protec-tion, 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 col-limators were installed in December.

CLOSING THE RING

“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.

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 compo-nents made of beryllium, an element that interferes very little with particles, and having individually designed forms. The vacuum system became fully operation-albefore 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 10-12 mbar, roughly the pressure on the surface of the Moon. Likewise, the cryogenic lines and the cold parts of

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

Meanwhile, the rest of the machine total-ling 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 oper-ate 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 equip-ment that makes up the cold mass of the LHC. The machine’s cryogenic instrumen-tation, including some 10k thermometers, was also commissioned to allow precision control of the cryogenic processes.

EVBC

Cryogenic thermometers installed on the vacuum side of intercon-nection QBQI.11L1

25

EXTRATERRESTRIAL VACUUM THE BIG CHILL

ALIGNMENT TARGET

MAIN QUADRIPOLE BUS-BARS

HEAT EXCHANGER PIPE

SUPERINSULATION

SUPERCONDUCTING COILS

BEAM PIPE

VACCUUM VESSEL

BEAM SCREEN

AUXILIARY BUS-BARS

SHRINKING CYLINDERHE I-VESSEL

THERMAL SHIELD

NON-MAGNETIC COLLARS

IRON YOKE

DIPOLE BUS-BARS

SUPPORT POST

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

THE BIG ADVENTURE

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 transi-tion 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 record-breaking numbers: more than 700 visited the experimental areas in 2008, and

LIOE

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

28

more than 140 were present on site for the LHC first-beam day in September.This resulted in an unprecedented media cov-erage for the Laboratory. Throughout the year, the Globe of Science and Innova-tion 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: Super-conductivity magical attraction, Acceler-ating Nobels (realized with the contribu-tion of the Fondation meyrinoise pour la promotion culturelle, sportive et sociale), and Big science.

The particle physics community, and ATLAS in particular, operates in many technical fields such as mechanics, elec-tronics, information technology, and communication. The many innovations and new technologies that emerge can lead, via industry, to important and ben-eficial 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 AT-

LAS’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 sys-tems. The main mission of the network is to facilitate the access of European industry to the new technologies devel-oped 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.

NATTT29

A NEW APPROACH TO TECHNOLOGY TRANSFER

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 accel-erator. 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 moni-tors 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 oper-ation of its main facilities, but also repre-sents 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 moni-tors 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 activi-ties by continuously measuring signifi-cant environmental parameters

PROTECTING THE ENVIRONMENT

such as those related to radiation, atmo-spheric 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 monitoring sta-tions, 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 negli-gible effect on the aquatic environment. Construction began in 2008 on a new wa-ter 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 concern-ing 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 instanta-neously and have no macroscopic effect.

SE31

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 im-mensely 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.

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 (nearly 1% of the world’s information production rate), a new approach to data storage, management, sharing and analysis was created in the LHC Comput-ing Grid project.

For more than a decade, building the LHC had been a dream for many who have worked hard to bring it to comple-tion. Finally we can retell the story of this adventure, from a dream to a reality…

LHC MILESTONES1984-2009

1984

Official starting point for work o

n the LHC

1985

First e

mbyonic collaborations began

1992

M

arked beginning for the LHC experiments

1994

ATLAS approves construction

1995

LHC te

chnical design report is published19

96 H

iggs Boson discovery approved

1997

Stu

dy to find state of matter that existed in the first m

oments o

f the Universe approved

1998

Firs

t pro

totype magnet tested successfully

1999

Components of th

e LHC detectors start to arrive

2000

LEP is

dismantled to make room for the LHC

2001

Firs

t phase

of LHC Computing Grid Project is approved

2002

CM

S magnet is

entirely built

2003

The

end of e

xcacavation work for the new accelerator

200

4 LH

C m

agnet test fa

cility is complete

200

5 Cr

yogenics u

nit cools to 1.8

kelvin (-271.4 degrees celsius) for first time

200

6 CM

S st

arts its

cosmic challenge test

200

7 Th

e la

st su

perconducting magnet is lowered underground

200

8 Th

e la

st e

lement t

o be installed for Project Origin is set in place

200

9 Fa

ulty

connectio

n delays LHC production. In early November the LHC was back up and running.