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ISOLDE reports about the shape of mercury isotopes' nuclei

ISOLDE reports about a phenomenon unique to mercury isotopes where the shape of the atomic nuclei dramatically moves between a football and rugby ball. Isotopes with extreme neutron to proton ratios are typically very short-lived, making them difficult to produce and study in the laboratory. The experiment reproduced one of ISOLDE’s flagship results of 40 years ago. The result showed that although most of the isotopes with neutron numbers between 96 and 136 have spherical nuclei, those with 101, 103 and 105 neutrons have strongly elongated nuclei, the shape of rugby balls. Several theories had tried to describe what was happening, but none was able to provide a full explanation.

Using one of the world’s most powerful supercomputers, theorists in Japan performed the most ambitious nuclear shell model calculations to date. These calculations identified the microscopic components that drive the shape shifting; specifically, that four protons are excited beyond a level predicted by expectations of how other stable isotopes in the nuclear landscape behave. These four protons combine with eight neutrons and this drives the shift to the elongated nuclear shape. In fact, both nuclear shapes are possible for each mercury isotope, depending on whether it is in the ground or excited state, but most have a football shaped nucleus in their ground state. The surprise is that Nature chooses the elongated rugby ball shape as the ground state for three of the isotopes.

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ISOLDE

Esplanade des Particules: CERN’s new official address

CERN, the État de Genève and the Ville de Meyrin inaugurate the brand-new Esplanade des Particules, an open space firmly focused on welcoming visitors and the general public. This large public space, designed with pedestrians and sustainable transport in mind, enhances the integration of CERN into the local urban landscape and improves access to the Laboratory.  From today onwards, CERN’s official address will be 1 Esplanade des Particules.

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The history of CERN

AWAKE achieves the first acceleration of electrons using a wave generated by protons zipping through a plasma

The AWAKE collaboration at CERN reports in Nature the first ever successful acceleration of electrons using a wave generated by protons zipping through a plasma.

First proposed in the 1970s, the use of plasma waves (or so called wakefields) has the potential to drastically reduce the size of accelerators in the next several decades. AWAKE, which stands for “Advanced WAKEfield Experiment”, is a proof-of-principle compact accelerator project for accelerating electrons to very high energies over short distances.

Electrons injected into AWAKE at relatively low energies of around 19 MeV (million electronvolts), “rode” the plasma wave, and were accelerated by a factor of around 100, to an energy of almost 2 GeV (billion electronvolts) over a length of 10 metres. Accelerating particles to greater energies over shorter distances is crucial to achieving high-energy collisions that physicists use to probe the fundamental laws of nature, and may also prove to be important in a wide range of industrial and medical applications.

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CERN accelerators

ATLAS observes elusive Higgs boson decay to a pair of bottom quarks

The Higgs boson is observed decaying into a pair of bottom quarks for the first time. This elusive interaction is predicted to make up almost 60% of the Higgs boson decays and is thus primarily responsible for the Higgs natural width.

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The ATLAS experiment

IceCube reports first evidence of a source of high-energy cosmic neutrinos

Scientists at IceCube observatory and collaborators identify what deem to be a source of very high energy neutrinos and, thus, of cosmic rays. 

Blazar TXS 0506+056 was first singled out as the source. A blazar is a giant elliptical galaxy with a massive, rapidly spinning black hole at its core, which emits twin jets of light and elementary particles.

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Cosmic rays

ATLAS observes direct interaction of Higgs boson with top quark

ATLAS announces the observation of Higgs bosons produced together with a top-quark pair. This rare process is one of the most sensitive tests of the Higgs mechanism and its observation marked a significant milestone for the field of High-Energy Physics.

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The ATLAS experiment

New CERN facility can help medical research into cancer

The new CERN-MEDICIS (Medical Isotopes Collected from ISOLDE) facility produced radioisotopes for medical research for the first time. These radioisotopes are destined primarily for hospitals and research centres in Switzerland and across Europe. 

“Radioisotopes are used in precision medicine to diagnose cancers, as well as other diseases such as heart irregularities, and to deliver very small radiation doses exactly where they are needed to avoid destroying the surrounding healthy tissue,” said Thierry Stora, MEDICIS project coordinator. “With the start of MEDICIS, we can now produce unconventional isotopes and help to expand the range of applications.”

The first batch produced was Terbium 155, which is considered a promising radioisotope for diagnosing prostate cancer.

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ISOLDE

The BASE experiment breaks its own precision measurement record of antiproton’s magnetic moment

The BASE collaboration, publishes today in Nature new measurement of the magnetic moment of the antiproton, with a precision exceeding that of the proton. Thanks to a new method involving simultaneous measurements made on two separately-trapped antiprotons in two Penning traps, BASE succeeded in breaking its own record presented last January

The magnetic moment of the antiproton is found to be 2.792 847 344 1(42), to be compared to the figure of 2.792 847 350(9) that the same collaboration of researchers found for the proton in 2014, at the BASE companion experiment at Mainz, in Germany.

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The story of antimatter

First direct evidence of light-by-light scattering at high energy

ATLAS publishes the first direct evidence of high energy light-by-light scattering, a very rare process in which two photons – particles of light – interact and change direction. The result, published in Nature Physics, confirms one of the oldest predictions of quantum electrodynamics.

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The ATLAS experiment

The LHCb experiment is charmed to announce observation of a new particle with two heavy quarks

At the EPS Conference on High Energy Physics in Venice, the LHCb experiment reports the observation of Ξcc++  (Xicc++), a new particle containing two charm quarks and one up quark. The existence of this particle from the baryon family was expected by current theories, but physicists were looking for such baryons with two heavy quarks for many years. The mass of the newly identified particle is about 3621 MeV, which is almost four times heavier than the most familiar baryon, the proton, a property that arises from its doubly charmed quark content. It is the first time that such a particle has been unambiguously detected.

Nearly all the matter that we see around us is made of baryons, which are common particles composed of three quarks, the best-known being protons and neutrons. But there are six types of existing quarks, and theoretically many different potential combinations could form other kinds of baryons. Baryons so far observed are all made of, at most, one heavy quark.

Finding a doubly heavy-quark baryon is of great interest as it will provide a unique tool to further probe quantum chromodynamics, the theory that describes the strong interaction, one of the four fundamental forces,” said Giovanni Passaleva, Spokesperson of the LHCb collaboration. “Such particles will thus help us improve the predictive power of our theories.”

In contrast to other baryons, in which the three quarks perform an elaborate dance around each other, a doubly heavy baryon is expected to act like a planetary system, where the two heavy quarks play the role of heavy stars orbiting one around the other, with the lighter quark orbiting around this binary system,” added Guy Wilkinson, former Spokesperson of the collaboration.

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The Large Hadron Collider

Sighting the Higgs in its favourite decay

ATLAS sees the first LHC evidence of the Higgs boson decaying to a pair of b-quarks. Despite being the dominant Higgs decay, finding evidence in this channel was a major challenge. Following years of dedicated search, ATLAS was able to spot this elusive decay in 2017, with an observed significance of 3.6 σ (expectation 4.0 σ) when combining the Run 1 and Run 2 datasets.

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The ATLAS experiment

ALICE experiment results show novel phenomena in proton collisions

In a paper published in Nature Physics, the ALICE collaboration reports that proton collisions sometimes present similar patterns to those observed in the collisions of heavy nuclei. This behaviour was spotted through observation of so-called strange hadrons in certain proton collisions in which a large number of particles are created. Strange hadrons are well-known particles with names such as Kaon, Lambda, Xi and Omega, all containing at least one so-called strange quark. The observed ‘enhanced production of strange particles’ is a familiar feature of quark-gluon plasma, a very hot and dense state of matter that existed just a few millionths of a second after the Big Bang, and is commonly created in collisions of heavy nuclei. But it is the first time ever that such a phenomenon is unambiguously observed in the rare proton collisions in which many particles are created. 

“We are very excited about this discovery,” said Federico Antinori, Spokesperson of the ALICE collaboration. “We are again learning a lot about this primordial state of matter. Being able to isolate the quark-gluon-plasma-like phenomena in a smaller and simpler system, such as the collision between two protons, opens up an entirely new dimension for the study of the properties of the fundamental state that our universe emerged from.”

The study of the quark-gluon plasma provides a way to investigate the properties of strong interaction, one of the four known fundamental forces, while enhanced strangeness production is a manifestation of this state of matter. The quark-gluon plasma is produced at sufficiently high temperature and energy density, when ordinary matter undergoes a transition to a phase in which quarks and gluons become ‘free’ and are thus no longer confined within hadrons. These conditions can be obtained at the Large Hadron Collider by colliding heavy nuclei at high energy. Strange quarks are heavier than the quarks composing normal matter, and typically harder to produce. But this changes in presence of the high energy density of the quark-gluon plasma, which rebalances the creation of strange quarks relative to non-strange ones. This phenomenon may now have been observed within proton collisions as well.

In particular, the new results show that the production rate of these strange hadrons increases with the ‘multiplicity’ – the number of particles produced in a given collision – faster than that of other particles generated in the same collision. While the structure of the proton does not include strange quarks, data also show that the higher the number of strange quarks contained in the induced hadron, the stronger is the increase of its production rate. No dependence on the collision energy or the mass of the generated particles is observed, demonstrating that the observed phenomenon is related to the strange quark content of the particles produced. Strangeness production is in practice determined by counting the number of strange particles produced in a given collision, and calculating the ratio of strange to non-strange particles.

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The Large Hadron Collider

First Technical Design Report released for ATLAS upgrade

ATLAS begins preparations for the Phase II upgrade of the experiment, which will be in place for the High-Luminosity LHC. This upgraded ATLAS experiment will begin data taking in 2026.

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The ATLAS experiment

ALPHA experiment observes the light spectrum of antimatter for the first time

The ALPHA collaboration reports in Nature the first ever measurement on the optical spectrum of an antimatter atom

When the electrons move from one orbit to another they absorb or emit light at specific wavelengths, forming the atom's spectrum. ALPHA result is the first observation of a spectral line in an antihydrogen atom, allowing the light spectrum of matter and antimatter to be compared for the first time. 

Within experimental limits
, the result shows no difference compared to the equivalent spectral line in hydrogen. This is consistent with the Standard Model of particle physics, the theory that best describes particles and the forces at work between them, which predicts that hydrogen and antihydrogen should have identical spectroscopic characteristicsMeasuring the antihydrogen spectrum with high-precision offers an extraordinary new tool to test whether matter behaves differently from antimatter and thus to further test the robustness of the Standard Model. 

The measurement was done by observing the so-called 1S-2S transition. The 2S state in atomic hydrogen is long-lived, leading to a narrow natural line width, so it is particularly suitable for precision measurement. 

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The story of antimatter

First measurement of the W boson mass at the LHC

ATLAS shows its strength for precision physics, taking a world-class measurement of the W boson mass. Precise measurements of the W boson mass are vital, as the parameter is related in the Standard Model to the masses of the top quark and the Higgs boson. Measuring the W mass can thus test the self-consistency of the Standard Model, since any deviation from the predicted relation would be a sign of new physics. This first ATLAS result is consistent and as precise as the best previous measurement of the W mass.

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ASACUSA experiment improves precision of antiproton mass measurement with new innovative cooling technique

The ASACUSA experiment at CERN reports in Science a new precision measurement of the mass of the antiproton relative to that of the electron. Such measurements provide a unique tool for comparing with high precision the mass of an antimatter particle with its matter counterpart. 

This result is based on spectroscopic measurements with about 2 billion antiprotonic helium atoms cooled to extremely cold temperatures of 1.5 to 1.7 degrees above absolute zero. In antiprotonic helium atoms an antiproton takes the place of one of the electrons that would normally be orbiting the nucleus. 

The measurement of the antiproton’s mass is done by spectroscopy
, by shining a laser beam onto the antiprotonic heliumASACUSA has now managed to cool down the antiprotonic helium atoms to temperatures close to absolute zero by suspending them in a very cold helium buffer-gas. In this way, the microscopic motion of the atoms is reduced, enhancing the precision of the frequency measurement. The measurement of the transition frequency has been improved by a factor of 1.4 to 10 compared with previous experiments. Experiments were conducted from 2010 to 2014, with about 2 billion atoms, corresponding to roughly 17 femtograms of antiprotonic helium. 

According to standard theories
, protons and antiprotons are expected to have exactly the same mass. The observation of even a minute breaking of CPT would call for a review of our assumptions about the nature and properties of space-time. 

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The LHC MoEDAL experiment publishes its first paper on its search for magnetic monopoles

In a paper published by the journal JHEP, the MoEDAL experiment at CERN narrows the window of where to search for a hypothetical particle, the magnetic monopole. Such particles were first predicted by physicist Paul Dirac in the 1930s, but have never been observed so far.

Just as electricity comes with two charges, positive and negative, so magnetism comes with two poles, North and South. The difference is that while it’s easy to isolate a positive or negative electric charge, nobody has ever seen a solitary magnetic charge, or monopole. If you take a bar magnet and cut it in half, you end up with two smaller bar magnets, each with a North and South pole. Yet theory suggests that magnetism could be a property of elementary particles. So just as electrons carry negative electric charge and protons carry positive charge, so magnetic monopoles could in theory carry a North or a South pole.

If monopoles exist, they are believed to be very massive. As the LHC produces collisions at unprecedented energy, physicists may be able to observe such particles if they are light enough to be in the LHC’s reach. For instance, high-energy photon–photon interactions could produce pairs of North and South monopoles. Monopoles could manifest their presence via their magnetic charge and through their very high ionizing power, estimated to be about 4700 times higher than that of the protons. The MoEDAL experiment at the LHC is designed specifically to look at these effects.

Although showing no evidence for trapped monopoles, the results have allowed the MoEDAL collaboration to place new mass limits, assuming a simple production mode of these hypothetical particles. 

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Romania joins

From CERN press release dated 17 July 2016:

On 17 July 2016, Romania became the twenty-second Member State of CERN.

Contacts between CERN and Romania began back in 1991, when a scientific and technical cooperation agreement was signed, establishing the legal framework for later developments.

Aspiring to become a full-fledged Member State and thus to contribute fully also to the governance of the Laboratory, Romania submitted its formal application to join the Organization in April 2008. The Agreement granting Romania the status of Candidate for Accession came into force on 12 November 2010.

Romania's scientific community at CERN has grown over the years and currently numbers around a hundred visiting scientists. Romania has particularly strong presence in the LHC experiments ATLAS, ALICE and LHCb. Romanian researchers and engineers also work at DIRAC and n_TOF at the Proton Synchrotron (PS), on the NA62 experiment at the Super Proton Synchrotron (SPS), and at the ISOLDE facility. Romania is also active in the Worldwide LHC Computing Grid.

Read the press release here.

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Member states

Combination of Higgs boson production and decay measurements of ATLAS and CMS

The ATLAS and CMS Experiments release combined measurements of the Higgs boson production and decay rates. Examining all data from the LHC Run-1, the result gives a snapshot of the world’s knowledge of the mysterious Higgs boson. In addition to setting constraints on Higgs couplings to vector bosons and fermions, the combination established the observation of Higgs to di-tau decay and weak-boson-fusion production.

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The ATLAS experiment

First radioactive isotope beam accelerated in HIE ISOLDE

CERN's nuclear physics facility, ISOLDE, began producing ion beams at higher energies. The first cryomodule of the new HIE-ISOLDE (High-Intensity and Energy ISOLDE) accelerator is up and running, increasing the beam energy from 3 to 4.3 MeV per nucleon. 

These first beams are the result of eight years of development and manufacturing. The assembly of this first cryomodule presented CERN’s teams with numerous technical challenges. It contains five accelerating cavities and a solenoid magnet that focuses the beam, all of which are superconducting. The cavities were particularly complex to build, and the cryomodule is made up of no fewer than 10 000 components! It was transported to the ISOLDE hall on 2 May and coupled to the existing accelerator. The commissioning began in the summer, culminating in the acceleration of the first radioactive beam on 22 October.

 

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The BASE experiment at CERN compares protons and antiprotons with high precision

Geneva, 12 August 2015. In a paper published today in Nature, the Baryon Antibaryon Symmetry Experiment (BASE1) at CERN2's Antiproton Decelerator (AD), reports the most precise comparison of the charge-to-mass ratio of the proton to that of its antimatter equivalent, the antiproton. 

The charge-to-mass ratio — an important property of particles — can be measured by observing the oscillation of a particle in a magnetic field. The new result shows no difference between the proton and the antiproton, with a four-fold improvement in the energy resolution compared with previous measurements.

To perform the experiment, the BASE collaboration used a Penning-trap system comparable to that developed by the TRAP collaboration in the late 1990s at CERN. However, the method used is faster than in previous experiments. This has allowed BASE to carry out about 13 000 measurements over a 35-day campaign, in which they compare a single antiproton to a negatively-charged hydrogen ion (H-). Consisting of a hydrogen atom with a single proton in its nucleus, together with an additional electron, the H- acts as a proxy for the proton.

“We found that the charge-to-mass ratio is identical to within 69 parts per thousand billion, supporting a fundamental symmetry between matter and antimatter,” said BASE spokesperson Stefan Ulmer.

While matter and antimatter particles can differ, for example, in the way they decay (a difference often referred to as violation of CP symmetry), other fundamental properties, such as the absolute value of their electric charges and masses, are predicted to be exactly equal. Any difference – however small — between the charge-to-mass ratio of protons and antiprotons would break a fundamental law known as CPT symmetry. This symmetry reflects well-established properties of space and time and of quantum mechanics, so such a difference would constitute a dramatic challenge not only to the Standard Model, but also to the basic theoretical framework of particle physics.

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Discovery of pentaquarks

Possible layout of the quarks in a pentaquark particle. The five quarks might be tightly bound (left). They might also be assembled into a meson (one quark and one antiquark) and a baryon (three quarks), weakly bound together (Image: Daniel Dominguez)

From the CERN website:

The LHCb experiment at CERN’s Large Hadron Collider has reported the discovery of a class of particles known as pentaquarks. The collaboration has submitted today a paper reporting these findings to the journal Physical Review Letters.

“The pentaquark is not just any new particle,” said LHCb spokesperson Guy Wilkinson. “It represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons, in a pattern that has never been observed before in over 50 years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we’re all made, is constituted.”

Our understanding of the structure of matter was revolutionized in 1964 when American physicist Murray Gell-Mann  proposed that a category of particles known as baryons, which includes protons and neutrons, are comprised of three fractionally charged objects called quarks, and that another category, mesons, are formed of quark-antiquark pairs. Antiquarks are quarks of antimatter. Gell-Mann was awarded the Nobel Prize in physics for this work in 1969. This quark model also allows the existence of other quark composite states, such as pentaquarks composed of four quarks and an antiquark.

Earlier experiments that have searched for pentaquarks have proved inconclusive. Where the LHCb experiment differs is that it has been able to look for pentaquarks from many perspectives, with all pointing to the same conclusion. It’s as if the previous searches were looking for silhouettes in the dark, whereas LHCb conducted the search with the lights on, and from all angles. The next step in the analysis will be to study how the quarks are bound together within the pentaquarks.

Read the full Press Release.

Read the LHCb article.

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The history of CERN

LHC experiments back in business at record energy of 13 TeV

From an update on the CERN website: 

The Large Hadron Collider (LHC) started delivering physics data today for the first time in 27 months. After an almost two year shutdown and several months re-commissioning, the LHC is now providing collisions to all of its experiments at the unprecedented energy of 13 TeV, almost double the collision energy of its first run. This marks the start of season 2 at the LHC, opening the way to new discoveries. The LHC will now run round the clock for the next three years.

“With the LHC back in the collision-production mode, we celebrate the end of two months of beam commissioning,” said CERN Director of Accelerators and Technology Frédérick Bordry. “It is a great accomplishment and a rewarding moment for all of the teams involved in the work performed during the long shutdown of the LHC, in the powering tests and in the beam commissioning process. All these people have dedicated so much of their time to making this happen.”

Today at 10.40am, the LHC operators declared “stable beams”, the signal for the LHC experiments that they can start taking data. Beams are made of “trains” of proton bunches moving at almost the speed of light around the 27 kilometre ring of the LHC. These so-called bunch trains circulate in opposite directions, guided by powerful superconducting magnets. Today the LHC was filled with 6 bunches each containing around 100 billion protons. This rate will be progressively increased as the run goes on to 2808 bunches per beam, allowing the LHC to produce up to 1 billion collisions per second.

For more information see the live blog that covered events as they unfolded.

See a gallery of images from the day.

Added 5 June: 

Watch a recording of the webcast from the day

Webcast: Q & A session

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The Large Hadron Collider

ATLAS Begins Recording Physics Data at 13 TeV

ATLAS began recording physics data from 13 TeV proton collisions, which allow for precision studies of the Higgs boson and other Standard Model particles, as well as the search for new particles with higher masses.

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The ATLAS experiment

CMS and LHCb experiments reveal decay of the B0s particle into two muon particles

Published in Nature, the CMS and LHCb collaborations describe the first observation of the very rare decay of the B0s particle into two muon particles. The Standard Model, the theory that best describes the world of particles, predicts that this rare subatomic process happens about four times out of a billion decays, but it has never been seen before. These decays are studied as they could open a window to theories beyond the Standard Model, such as supersymmetry. The analysis is based on data taken at the Large Hadron Collider (LHC) in 2011 and 2012. These data also contain early hints of a similar, but even more rare decay into two muons of the B0, a cousin of the B0s.

The B0s and B0 are mesons, in other words, non-elementary unstable subatomic particles composed of a quark and an antiquark, bound together by the strong interaction. Such particles are produced only in high-energy collisions – at particle accelerators, or in nature, for example in cosmic-ray interactions.

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The Large Hadron Collider

ISOLDE capable of producing radioactive ion beams from 74 chemical elements

Radioactive ion beams from many chemical elements are produced at ISOLDE and more than 1000 Radioactive Ion Beams (RIBs) are available for the users.  With a Carbon nanotube target the element boron could be produced as a RIB for the first time and the isotope 8B (T1/2=770 ms) could be observed. With this addition to the palette of ISOLDE beams the Facility can now provide beams from 74 chemical elements to the user community.

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ISOLDE

First beams at 13 TeV in the LHC

The first beams at the energy of 13 TeV circulated in the Large Hadron Collider at XXXX this morning

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Long Shutdown 1

Testing the injection lines on the LHC

From the CERN website, posted 24 November 2014:

Over the weekend, proton beams came knocking on the Large Hadron Collider's (LHC) door. Shooting from the Super Proton Synchrotron (SPS) and into the two LHC injection lines, the proton beams were stopped just short of entering the accelerator. 

Although the actual physics run will not start until 2015, the LHC Operations team used these tests to check their control systems, beam instrumentation, transfer line alignment, perform the first optics measurements and to spot possible bottle necks in the beam trajectory. Furthermore, the ALICE and LHCb experiments could calibrate their detectors.

"These initial tests are a milestone for the whole accelerator chain," says Reyes Alemany Fernandez, the engineer in charge of the LHC. "Not only was this the first time the injection lines have seen beams in over a year, it was also our first opportunity to test the LHC's operation system. We successfully commissioned the LHC's injection and ejection magnets, all without beam in the machine itself."

Just before entering the LHC, the beams were stopped by 21.6 tonnes of graphite, aluminium and copper "beam dumps" that absorb the accelerated particles. Offshoot particles - primarily muons - generated during the dump were in turn used to calibrate ALICE and LHCb. "The experiments where given the precise timing of each beam dump, which allowed them to tune their detectors and trigger to the LHC clock," says Verena Kain, SPS supervisor. 

Following these successful extraction tests, the Operations team return to their preparations for the next run of the LHC. The first LHC tests with beams are scheduled for February 2015.

Read more: "The proton beam knocks at the LHC door– Update by the LHCb experiment collaboration

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Long Shutdown 1

First LHC sector up to full energy

From the CERN website, posted 9 December 2014: 

Target energy achieved ! On Tuesday 9 December at 2.18 p.m., a key milestone in the restart of the world’s largest and most powerful particle accelerator was passed. Sector 6-7 of the Large Hadron Collider has been commissioned to a beam energy of 6.5 TeV. The 154 superconducting dipole magnets which make up this sector – corresponding to one eighth of the accelerator – were powered to a current of around 11,000 amps! These currents (about a thousand times greater than in your average household appliance) are needed to generate sufficiently high magnetic fields to bend the trajectory of particles with an energy of 6.5 TeV. It’s at this unprecedented beam energy that the LHC will restart next spring with the aim of producing collisions with a total energy of 13 TeV.

From 2010 to 2013, the LHC ran at beam energies of up to 4 TeV. This first run produced a rich harvest of results in hitherto uncharted areas of physics and, in particular, led to the discovery of the famous Higgs boson. But the LHC was designed to operate at even higher energies and, to achieve this, the machine was shut down for almost two years for the main magnet circuits to be consolidated. This involved reinforcing 1,700 magnet interconnections, including more than 10,000 superconducting splices. So the commissioning of the modified sectors of the accelerator with the higher-intensity currents needed to reach 6.5 TeV beams is a key milestone in the restart process.

Like top athletes, the LHC magnets have to undergo a strenuous training programme to reach the required energy. The magnets are superconducting, which means that when they are cooled down current passes through them with zero electrical resistance. During training, the current is gradually increased and as it circulates inside the magnet coils the forces generated can cause tiny movements, which can in turn cause the magnets to “quench”,  i.e. suddenly return to a non-superconducting state. When this occurs, the circuit is switched off and its energy is absorbed by huge resistors.

The magnets in all the other sectors will undergo similar training before being ready for 6.5 TeV operation. Many other tests will follow before beams can circulate in the LHC once more, next spring.

 

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Cooling down: The LHC is filled with liquid helium at 4K

From the CERN website, posted 17 December 2014:

Last week the cryogenics team at CERN finished filling the arc sections of the Large Hadron Collider (LHC) with liquid helium. The helium, which is injected into magnetsthat steer particle beams around the 27-kilometre accelerator, cools the machine to below 4 degrees kelvin (-269.15°C).

The process of filling the LHC is an important milestone on the road to restarting theaccelerator at higher energy, though it will still take many weeks to cool the entire accelerator to its nominal operating temperature of 1.9 K (-271.3°C).

The electromagnets that steer particle beams around the LHC must be kept cold enough to operate in a superconducting state – the temperature at which electricity can pass through a material without losing energy to resistance. The niobium-titanium wires that form the coils of the LHC’s superconducting magnets are therefore maintained at 1.9 K by a closed liquid-helium circuit. This is colder than the average temperature – 2.7 K – in outer space.

Some 1232 dipole magnets will produce a magnetic field of 8.33 tesla to keep particle beams on course around the LHC's 27-kilometre ring. A current of 11,850 amps in the magnet coils is needed to reach magnetic fields of this amplitude. The use of superconducting materials has proved to be the best – and most cost-effective – way to avoid overheating the coils.

Find out more:

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Long Shutdown 1

CERN’s Large Hadron Collider gears up for run 2

Run 2 of the LHC follows a 2-year technical stop that prepared the machine for running at almost double the energy of the LHC’s first run, producing 13 TeV collisions, an energy never achieved by any accelerator in the past.

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The Large Hadron Collider

CERN celebrates its 60th birthday

On 29 September 1954, the CERN Convention entered into force, officially establishing the European Organization for Nuclear Research with 12 European member states. CERN celebrated “60 years of science for peace” with an official ceremony on 29 September and numerous public events taking place throughout the year.

Check out the website that contains a record of the activities that marked the Organization’s 60th Anniversary.

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Archive of important events in CERN's history for press

AMS experiment unveils new territories in the flux of cosmic rays

The Alpha Magnetic Spectrometer (AMS) collaboration presents new insights into the nature of the mysterious excess of positrons observed in the flux of cosmic rays. These are based on the analysis of 41 billion particles, among which 10 million have been identified as electrons and positrons, detected with the space-based AMS detector aboard the International Space Station. 

Since antimatter is extremely rare in the universe, any significant excess of antimatter particles recorded in the flux of energetic cosmic rays indicates the existence of a new source of positrons. 

The distribution of these events in the energy range of 0.5 to 500 GeV shows a well-measured increase of positrons from 8 GeV with no preferred incoming direction in space. The energy at which the positron fraction ceases to increase has been measured to be 275±32 GeV. This rate of decrease after the “cut-off energy” is very important to physicists as it could be an indicator that the excess of positrons is the signature of dark matter particles annihilating into pairs of electrons and positrons.

Although the current measurements could be explained by objects such as pulsars, they are also tantalizingly consistent with dark matter particles with mass of the order of 1 TeV. Therefore, results at higher energies will be of crucial importance in the near future to evaluate if the signal is from dark matter or from a cosmic source.

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Cosmic rays

Restart of the Proton Synchrotron

Content to come

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Long Shutdown 1

CERN’s ALPHA experiment measures charge of antihydrogen

In a paper published in the journal Nature Communications today, the ALPHA experiment at CERN's Antiproton Decelerator (AD) reports a measurement of the electric charge of antihydrogen atoms, finding it to be compatible with zero to eight decimal places. Although this result comes as no surprise, since hydrogen atoms are electrically neutral, it is the first time that the charge of an antiatom has been measured to high precision.

Antiparticles should be identical to matter particles except for the sign of their electric charge. So while the hydrogen atom is made up of a proton with charge +1 and an electron with charge -1, the antihydrogen atom consists of a charge -1 antiproton and a charge +1 positron. We know, however, that matter and antimatter are not exact opposites – nature seems to have a one-part in 10 billion preference for matter over antimatter, so it is important to measure the properties of antimatter to great precision: the principal goal of CERN’s AD experiments. ALPHA achieves this by using a complex system of particle traps that allow antihydrogen atoms to be produced and stored for long enough periods to study in detail. Understanding matter antimatter asymmetry is one of the greatest challenges in physics today. Any detectable difference between matter and antimatter could help solve the mystery and open a window to new physics.

To measure the charge of antihydrogen, the ALPHA experiment studied the trajectories of antihydrogen atoms released from the trap in the presence of an electric field. If the antihydrogen atoms had an electric charge, the field would deflect them, whereas neutral atoms would be undeflected. The result, based on 386 recorded events, gives a value of the antihydrogen electric charge as (-1.3±1.1±0.4) × 10-8, the plus or minus numbers representing statistical and systematic uncertainties on the measurement.

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The story of antimatter

Restart of the Proton Synchrotron Booster

Content to come

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Long Shutdown 1

ATLAS finds evidence for the rare electroweak W±W± production

ATLAS publishes first evidence for electroweak production of W bosons with the same charge. This channel receives contributions from quartic interactions between W bosons. This rare process gives physicists a new way to study electroweak symmetry breaking and to indirectly probe the properties of the Higgs boson.

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The ATLAS experiment

IceCube measures 5σ significance level for the observation of extraterrestrial neutrinos

Inspired by the 1PeV events, IceCube began a follow up search with combined two powerful techniques. The first was to distinguish neutrino interactions that originated inside the detector from events which originate outside it. The second technique capitalized on the fact that downgoing atmospheric neutrinos should be accompanied by a cosmic-ray air shower depositing one or more muons inside IceCube whereas cosmic neutrinos should be unaccompanied. Consequently, a very high energy isolated downgoing neutrino is likely to be cosmic.

This search found 26 additional events and produced evidence for cosmic neutrinos at the 4σ significance level. The search was continued for an extra year in order to push the significance up to 5σ. One of the new events had an energy of above 2 PeV, making it the most energetic neutrino ever seen. Many explanations have been proposed for the IceCube observations, ranging from the relativistic particle jets emitted by active galactic nuclei to gamma ray busts, to galaxies to magnetars. Overall the solution is clear: More data is needed. 

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Cosmic rays

27,000th electrical shunt in place on the LHC

From the CERN website, posted 5 May 2014:

Since April last year, the Superconducting Magnets And Circuits Consolidation (SMACC) team has been strengthening the electrical connections of the superconducting circuits on the Large Hadron Collider (LHC). Last week they installed the last of 27,000 electrical shunts to consolidate "splices" – connections between superconducting magnets – on the accelerator.

Each of the LHC's 10,000 splices carries a hefty 13,000 amps. A shunt is a low-resistance connection that provides an alternative path for a portion of the current in the event that a splice loses its superconducting state.

On 19 September 2008, during powering tests on the LHC, a fault occurred in one of the splices, resulting in mechanical damage and release of helium from the magnet cold mass into the tunnel. Proper safety procedures were in force, the safety systems performed as expected, and no-one was put at risk. But the fault did delay operation of the accelerator by six months. The new shunts make such a fault unlikely to happen again.

To install a shunt the SMACC team first has to open the area around the interconnection they want to work on. They slide the custom-built metallic bellows out of the way and remove the thermal shielding inside, revealing a series of metallic pipes linking the magnets to each other. One set of these pipes – the "M-lines" – must then be cut open to access the splices between the superconducting cables. The team opened up the last of the M lines in February and has been at work ever since adding the shunts.

Check out some more of the main LHC consolidations

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Long Shutdown 1

CERN celebrates 60 years of science for peace

CERN announces its anniversary of 60 years of science for peace, with events at the Organization’s Geneva laboratory and in its Members States. 

CERN celebrated twice: first on 1 July 2014 at UNESCO Headquarters in Paris, where the Organization’s 12 founding members established the CERN Convention on 1 July 1953. And the second celebration of the 60th birthday was in Geneva on 29 September, the date on which the Convention was ratified 60 years ago and the Organization formally came into existence. 

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The history of CERN

Israel joins

From CERN press release dated 15 January 2014: 

 

At a ceremony today at CERN, the Israeli flag was hoisted for the first time to join the other 20 flags of the organization’s Member States, after UNESCO officially recorded Israel's accession as a new CERN Member State on 6 January 2014.

Following the ceremony, Mr Avigdor Liberman, Deputy Prime Minister and Minister of Foreign Affairs of the State of Israel, visited the LHC tunnel and the ATLAS experiment, accompanied by a delegation of officials and representatives of the Israeli scientific community.

"In my visit in CERN today, I have witnessed the frontiers of science. I have realized the scope of collaboration between Israel and CERN. Israeli scientists and their CERN colleagues share a dedication to scientific excellence, technological development and education. Israel and CERN share ideals and goals and therefore have a wide prospect for cooperation," said Mr Avigdor Liberman.

"I am very honoured as Director-General to welcome Israel as a new Member State. CERN and Israel have already a long history of mutual collaboration, and this day will undoubtedly be memorable, promising increasingly fruitful scientific cooperation between CERN and the Israeli physics community," said CERN’s Director-General Rolf Heuer.

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Member states

Data-taking to continue until 2035

The LHC will be upgraded to 14 TeV collision energy. The first major upgrade is Phase I, scheduled for 2018, and Phase 2 in 2022. The experiments will continue taking data until 2035. By then ATLAS expects to have collected 100 times more data than they had at the beginning of Long Shutdown 1.

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The ATLAS experiment

François Englert and Peter W. Higgs awarded 2013 Nobel Prize in Physics

François Englert (left) and Peter Higgs at CERN on 4 July 2012, on the occasion of the announcement of the discovery of a Higgs boson by the ATLAS and CMS experiments (Image: Maximilien Brice/CERN)

 

On 8 October 2013, CERN congratulates François Englert and Peter W. Higgs on the award of the Nobel Prize in physics “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider.”

The Brout-Englert-Higgs (BEH) mechanism was first proposed in 1964 in two independently published papers: the first by Belgian physicists Robert Brout and François Englert, and the second by British physicist Peter Higgs. It explains how the force responsible for beta decay is much weaker than electromagnetism, but is better known as the mechanism that endows fundamental particles with mass. A third paper, published by Americans Gerald Guralnik and Carl Hagen with their British colleague Tom Kibble further contributed to the development of the new idea, which now forms an essential part of the Standard Model of particle physics. As was pointed out by Higgs, a key prediction of the idea is the existence of a massive boson of a new type, which was discovered by the ATLAS and CMS experiments at CERN in 2012.

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The Large Hadron Collider

Nobel Prize for the Higgs discovery

The 2013 Nobel Prize in physics is awarded to Professors François Englert and Peter Higgs "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider". ATLAS and CMS physicists cheered the announcement.

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The ATLAS experiment

The ISOLTRAP collaboration measures the mass of exotic calcium nuclei

The ISOLTRAP collaboration publishes in the journal Nature the mass of exotic calcium nuclei using a new instrument installed at the ISOLDE facility. The results cast light on how nuclei can be described in terms of the fundamental strong force.

The ISOLTRAP team used the ISOLDE facility to make exotic isotopes of calcium, which has the magic number of 20 protons in a closed shell. Their goal was to find out how the shell structure evolves with increasing numbers of neutrons. Standard calcium with 20 neutrons is doubly magic, and a rare long-lived isotope has 28 neutrons – another magic number.

Now, the ISOLTRAP team has determined the masses of calcium isotopes all the way to calcium-54, which has 34 neutrons in addition to the 20 protons. The measurements not only reveal a new magic number, 32, but also pin down nuclear interactions in exotic neutron-rich nuclei.

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ISOLDE

ISOLDE success culminates in three Nature publications

In the middle of 2013 the success of combined technical and physical efforts was demonstrated in three papers published in Nature within the space of one month.

  1. The acceleration of the hitherto heaviest post-accelerated beams, 220Rn and 224Rn and detection of gamma rays from Coulomb excitation in the MINIBALL Germanium detector array showed octupole deformed (pear-like) shapes of the nuclei (Nature 497 (2013) 199).
  2. With the very successful mass spectrometer ISOLTRAP the mass of the exotic nuclide 54Ca was determined. The mass systematics confirmed the existence of a new magic number N=32 and provides a validation of three-body forces using chiral perturbation theory (Nature 498 (2013) 346).
  3. In a high-precision study via Rydberg states with the laser ion-source (RILIS), the ionisation potential for the element Astatine, the least abundant chemical element on earth, was determined (Nature Communications 4 (2013) 1835).
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ISOLDE

First observations of short-lived pear-shaped atomic nuclei

An international team at the ISOLDE facility showed that some atomic nuclei can assume asymmetric, "pear" shapes. The observations contradict some existing nuclear theories and will require others to be amended. Published in the journal Nature, a technique pioneered at ISOLDE was used successfully to study the shape of the short-lived isotopes Radon 220 and Radium 224.

Most nuclei have the shape of a rugby ball. While state-of-the-art theories are able to predict this behaviour, the same theories have predicted that for some particular combinations of protons and neutrons, nuclei can also assume asymmetric shapes, like a pear.  In this case there is more mass at one end of the nucleus than the other.

In contradiction with some nuclear theories, Radium 224 is pear-shaped, Radon 220 does not assume the fixed shape of a pear but rather vibrates about this shape.  

Such exotic atoms with pear-shaped nuclei could help with the searches for electric dipole moments (EDMs), that is the separation of positive and negative charges within the atom. 

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ISOLDE

ALPHA first direct analysis on how antimatter is affected by gravity

The ALPHA collaboration at CERN1 has published a paper in Nature Communications describing the first direct analysis of how antimatter is affected by gravity.

ALPHA was the first experiment to trap atoms of antihydrogen — neutral antimatter atoms held in place with a strong magnetic field for up to 1000 seconds. The original goal of the experiment was not to study gravity, but the researchers realised that the data they had already collected might be sensitive to gravitational effects.

Current theoretical arguments predict that hydrogen and antihydrogen atoms have the same mass and should interact with gravity in the same way. If an atom is released, it should experience a downward force whether it’s made of matter or antimatter. The ALPHA scientists have retroactively analysed how their antihydrogen atoms moved when released; this has allowed them to put a limit on anomalous gravitational effects.

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The story of antimatter

LHCb experiment observes new matter-antimatter difference

The LHCb collaboration at CERN publishes a paper in Physical Review Letters on the first observation of matter-antimatter asymmetry in the decays of the particle known as the B0s. It has a significance of more than 5 sigma, and is only the fourth subatomic particle known to exhibit such behaviour. 

By studying subtle differences in the behaviour of particle and antiparticles, experiments at the LHC are seeking to cast light on this dominance of matter over antimatter.

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The story of antimatter

ATRAP experiment makes world’s most precise measurement of antiproton magnetic moment

In Physical Review Letters, the Antihydrogen TRAP (ATRAP) experiment at CERN's Antiproton Decelerator (AD) reports a new measurement of the antiproton magnetic moment made with an unprecedented uncertainty of 4.4 parts per million (ppm). This result is 680 times more precise than previous measurements. The unusual increase in precision is due to the experiment’s ability to trap individual protons and antiprotons, and to use a huge magnetic gradient to gain sensitivity to the tiny magnetic moment. ATRAP’s new result is partly an attempt to understand the matter-antimatter imbalance of the universe, one of the great mysteries of modern physics.

Using a device called a Penning trap, a sort of electromagnetic cage, the antiproton is suspended at the centre of an iron ring electrode sandwiched between copper electrodes. Thermal contact with liquid helium keeps the electrodes at 4.2 K, providing a nearly perfect vacuum that eliminates the stray matter atoms that could otherwise annihilate the antiproton. Static and oscillating voltages applied to the electrodes allow the antiproton to be manipulated and its properties to be measured.

The ATRAP team found that the magnetic moments of the antiproton and proton are "exactly opposite": equal in strength but opposite in direction with respect to the particle spins, consistent with the prediction of the Standard Model and its CPT theorem to 5 parts per million. However, the potential for much greater measurement precision puts ATRAP in position to eventually test the Standard Model prediction much more stringently.

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The story of antimatter

End of LHC Run 1: First shutdown begins

On Saturday 16 February at 8.25am the shift crew in the CERN Control Centre extract the beams from the Large Hadron Collider (LHC) for the last time before the machine's first Long Shutdown. The following message marks the event on LHC Page 1: "No beam for a while. Access required: Time estimate ~2 years."

January's proton-lead run was followed last week by four days of proton-proton collisions at 1.38 TeV. Final proton collisions in the LHC took place on Thursday at 7.24am, but beams were kept in the machine for 48 hours for "quench tests" on the magnets. A quench is when a superconducting magnet fails to maintain a superconducting state, and therefore stops operating correctly. This can happen if a tiny amount of the beam is off orbit and deposits energy in the magnets. The tests aim to establish what beam loss is actually required to quench the magnets.

The LHC’s first run saw major advances in physics, including the discovery of a new particle that looks increasingly like the long–sought Higgs boson, announced on 4 July 2012. And during the last weeks of the run, the remarkable figure of 100 petabytes of data stored in the CERN mass-storage systems was surpassed. This data volume is roughly equivalent to 700 years of full HD-quality movies.

The LHC now enters its two-year shutdown, which will see a hive of maintenance activity on all of CERN's accelerators. Work on the LHC will include the consolidation of more than 10,000 interconnections between magnets. The entire ventilation system for the 628-metre circumference Proton Synchrotron will be replaced, as will over 100 kilometres of cables on the Super Proton Synchrotron. The LHC is scheduled to resume in 2015.

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The Large Hadron Collider

LHC shuts down: 2-year maintenance period begins

The news on the CERN website posted 18 February 2013:

On Saturday at 8.25am the shift crew in the CERN Control Centre extracted the beams from the Large Hadron Collider (LHC) for the last time before the machine's first Long Shutdown. The following message marked the event on LHC Page 1: "No beam for a while. Access required: Time estimate ~2 years."

January's proton-lead run was followed last week by four days of proton-proton collisions at 1.38 TeV. Final proton collisions in the LHC took place on Thursday at 7.24am, but beams were kept in the machine for 48 hours for "quench tests" on the magnets.

A quench is when a superconducting magnet fails to maintain a superconducting state, and therefore stops operating correctly. This can happen if a tiny amount of the beam is off orbit and deposits energy in the magnets. The tests aimed to establish what beam loss is actually required to quench the magnets.

The LHC now enters its two-year shutdown, which will see a hive of maintenance activity on all of CERN's accelerators. Work on the LHC will include the consolidation of more than 10,000 interconnections between magnets. The entire ventilation system for the 628-metre circumference Proton Synchrotron will be replaced, as will over 100 kilometres of cables on the Super Proton Synchrotron.

It's going to be a busy shutdown.

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Long Shutdown 1

Toward 14 Tev: preparing for increase in total energy

In February 2013, the LHC and the ATLAS Experiment begin the first Long Shutdown. This maintenance period would see the first upgrades to the ATLAS Experiment installed, in preparation for higher luminosity operations.

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The ATLAS experiment

Approval of the CERN-MEDICIS project

(Image: Groundbreaking for the CERN-MEDICIS building. From left - R. Meuli, Chef du Département de Radiologie Médicale, CHUV, D. Hanahan, Director, Swiss Institute for Experimental Cancer Research R. Heuer, Directeur général, CERN Y. Grandjean Secrétaire général, HUG P. Piet Van Duppen, Nuclear Spectroscopy Group, Katholieke Universiteit Leuven. Credit: Maximillien Brice/ CERN)

CERN-MEDICIS will use the primary proton beam at ISOLDE to produce radioisotopes for medical research. A second target will be placed after the one at ISOLDE as the high energy proton beam only deposits 10% of its intensity and energy when traversing the standard type of ISOLDE target and thus the protons passing through the target can still be used. An automated conveyor will then carry this second target to the CERN-MEDICIS infrastructure, where the radioisotopes will be extracted.

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ISOLDE

ATLAS and CMS submit Higgs-search papers

The ATLAS and CMS collaborations submitted papers to the journal Physics Letters B outlining the latest on their searches for the Higgs boson. The teams reported even stronger evidence for the presence of a new Higgs-like particle than they announced the month before.

On 4 July the experiments reported indications for the presence of a new particle, which could be the Higgs boson, in the mass region around 126 gigaelectronvolts (GeV). Both ATLAS and CMS gave the level of significance of the result as 5 sigma. On the scale that particle physicists use to describe the certainty of a discovery, one sigma means the results could be random fluctuations in the data, 3 sigma counts as evidence and a 5-sigma result is a discovery.

The CMS results reported today reach a significance of 5.0 sigma, and the ATLAS team's results reach 5.9 sigma. The value corresponds to a one-in-550 million chance that in the absence of a Higgs such a signal would be recorded.

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The search for the Higgs boson

ATLAS and CMS observe a particle consistent with the Higgs boson

On 4 July 2012, as a curtain raiser to the year’s major particle physics conference, ICHEP 2012 in Melbourne, the ATLAS and CMS experiments present their latest preliminary results in the search for the long-sought Higgs particle. Both experiments have observed a new particle in the mass region around 125-126 GeV. 

The next step is to determine the precise nature of the particle and its significance for our understanding of the universe. Are its properties as expected for the long-sought Higgs boson, the final missing ingredient in the Standard Model of particle physics? Or is it something more exotic? The Standard Model describes the fundamental particles from which we, and every visible thing in the universe, are made, and the forces acting between them. All the matter that we can see, however, appears to be no more than about 4% of the total. A more exotic version of the Higgs particle could be a bridge to understanding the 96% of the universe that remains obscure.

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The ATLAS experiment, The Large Hadron Collider, The history of CERN, The search for the Higgs boson, Archive of important events in CERN's history for press

CERN signs contract for a remote data centre in Budapest

CERN today signed a contract with the Wigner Research Centre for Physics in Budapest for an extension to the CERN data centre. Under the new agreement, the Wigner Centre will host CERN equipment that will substantially extend the capabilities of the LHC Computing Grid Tier-0 activities. This contract is initially until 31 December 2015, with the possibility of up to four one-year extensions thereafter.

“Installing computing capacity at the Wigner Centre allows us to power additional equipment as well as secure our operations due to the remote nature of the resources” said Frédéric Hemmer, Head of CERN’s IT Department. “For example, should we suffer a prolonged power cut at CERN, we will be able to transfer critical functions to the Wigner Centre, mitigating the risk of having all of Tier-0 in one location."

Read the press release

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Computing at CERN

Record collision energy of 8TeV

(image: event recorded with the CMS detector in 2012 at a proton-proton centre of mass energy of 8TeV)

On 5 April 2012, LHC physics data taking gets underway at a new record collision energy of 8TeV. The LHC declares "stable beams" as two 4 TeV proton beams are brought into collision at the LHC’s four interaction points. This signals the start of physics data taking by the LHC experiments for 2012.  The collision energy of 8 TeV is a new world record, and increases the machine’s discovery potential considerably.

“The experience of two good years of running at 3.5 TeV per beam gave us the confidence to increase the energy for this year without any significant risk to the machine,” says CERN’s Director for Accelerators and Technology, Steve Myers. “Now it’s over to the experiments to make the best of the increased discovery potential we’re delivering them!”

Although the increase in collision energy is relatively modest, it translates to an increased discovery potential that can be several times higher for certain hypothetical particles. Some such particles, for example those predicted by supersymmetry, would be produced much more copiously at the higher energy. Supersymmetry is a theory in particle physics that goes beyond the current Standard Model, and could account for the dark matter of the universe.

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The Large Hadron Collider

Tantalising hints of the Higgs

In a seminar today the ATLAS and CMS experiments present the status of their searches for the Standard Model Higgs boson. Their results are based on the analysis of considerably more data than those presented at the summer conferences, enough to make significant progress in the search for the Higgs boson, but not enough to make any conclusive statement on the existence or non-existence of the elusive Higgs. The main conclusion is that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS. Tantalising hints were seen by both experiments in this mass region, but they were not yet strong enough to claim a discovery.

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The search for the Higgs boson, The history of CERN, The Large Hadron Collider

LHC proton run for 2011 reaches successful conclusion

On 18 October 2011, the grand total of data delivered by the LHC during the year reaches almost six inverse femtobarns. At the beginning of the year’s run, the objective for the LHC was to deliver a quantity of data known to physicists as one inverse femtobarn – approximately 100 trillion (102) proton-proton collisions - during the course of 2011. The first inverse femtobarn came on 17 June, setting the experiments up well for the major physics conferences of the summer and requiring the 2011 data objective to be revised upwards to five inverse femtobarns. This milestone is passed on 18 October.

“At the end of this year’s proton running, the LHC is reaching cruising speed,” says CERN’s Director for Accelerators and Technology, Steve Myers. “To put things in context, the present data production rate is a factor of 4 million higher than in the first run in 2010 and a factor of 30 higher than at the beginning of 2011.”

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The Large Hadron Collider

CERN sets course for extra-low-energy antiprotons

The kick-off meeting for ELENA, the Extra Low Energy Antiproton Ring, starts today at CERN, bringing together scientists from Canada, Denmark, France, Germany, Japan, Sweden, the UK and the USA. 

 

ELENA will consist of a small new decelerator ring that will be installed in same building that houses CERN’s existing Antiproton Decelerator (AD). It will slow antiprotons down to under a fiftieth of the current AD energy, bringing an improvement of a factor of 10-100 in antiproton trapping efficiency. At the AD, antiprotons have to be slowed down by passing them through a series of foils, a process that results in the loss of some 99.9% of the antiprotons extracted from the AD before they reach the experiments.

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The story of antimatter

IceCube presents the 1 PeV event

In 2013 IceCube presented two events at around 1 PeV, the first recorded on 9 August 2011, the second on 3 January 2012. Both of these events were part of the search for ultra high energy cosmogenic neutrinos  and were completely unexpected. These were the highest neutrino energies to be observed with an equivalent mass energy of over 1 million protons or about 250 times the energy of one of the protons accelerated at the LHC. The neutrinos detected may have originated from Galactic or extragalactic sources of cosmic rays. The 1 PeV events were spectacular but the energies were too low to be produced by cosmic rays interacting with cosmic microwave background photons.  

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Cosmic rays

ASACUSA weighs antimatter to one part in a billion

In a paper published today in the journal Nature, the Japanese-European ASACUSA experiment at CERN reported a new measurement of the antiproton’s mass accurate to about one part in a billion. Precision measurements of the antiproton mass provide an important way to investigate nature’s apparent preference for matter over antimatter.

To make these measurements antiprotons are first trapped inside helium atoms, where they can be ‘tickled’ with a laser beam. The laser frequency is then tuned until it causes the antiprotons to make a quantum jump within the atoms, and from this frequency the antiproton mass can be calculated. However, an important source of imprecision comes from the fact that the atoms jiggle around, so that those moving towards and away from the beam experience slightly different frequencies. A similar effect is what causes the siren of an approaching ambulance to apparently change pitch as it passes you in the street. In their previous measurement in 2006, the ASACUSA team used just one laser beam, and the achievable accuracy was dominated by this effect. This time they used two beams moving in opposite directions, with the result that the jiggle for the two beams partly cancelled out, resulting in a four times better accuracy.

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The story of antimatter

ALPHA traps antimatter atoms for 1000 seconds

The ALPHA experiment at CERN reported today that it succeeded in trapping antimatter atoms for over 16 minutes: long enough to begin to study their properties in detail. ALPHA is part of a broad programme at CERN’s antiproton decelerator investigating the mysteries of one of nature’s most elusive substances.

ALPAH studied 300 trapped antiatoms. Trapping antiatoms will allow antihydrogen to be mapped precisely using laser or microwave spectroscopy so that it can be compared to the hydrogen atom, which is among the best-known systems in physics. Any difference between matter and antimatter should become apparent under careful scrutiny.

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The story of antimatter, The history of CERN

Launch of the Alphamagnetic Spectrometer (AMS)

AMS during tests at the University of Geneva, Switzerland, in 1999 (Image: Laurent Guiraud)

On 16 May 2011, the space shuttle Endeavor delivered the Alphamagnetic Spectrometer (AMS) to the International Space station. This took place as part of the space shuttle mission STS-134. AMS is a particle physics detector which looks for dark matter, antimatter and missing matter from a module attached to the outside of the International space station. AMS also performs precision measurements of cosmic rays. Data are received by NASA in Houston and is then relayed to the AMS Payload Operations Control Centre at CERN for analysis. The detector measures 64 cubic metres and weighs 8.5 tonnes. By the 19 May 2012, after a year of operating, about 17 billion cosmic-ray events had been collected. 

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Cosmic rays

IceCube construction completed

On 18 December 2010, the expanded version of AMANDA, IceCube was completed. IceCube works in the same way as AMANDA but on a larger scale. AMANDA was incorporated into IceCube after operating for nine years. IceCube took seven years to complete and measures Cherenkov light emitted by charged particles produced in neutrino interactions in a cubic kilometer of transparent ice – the water equivalent of one million swimming pools.

IceCube detects 275 million cosmic rays each day and approximately 100,000 neutrinos per year. Approximately a terabyte of unfiltered data is collected daily and about 100 gigabytes are sent over satellite for analysis. 

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Cosmic rays

First ATLAS observation and rate measurement of top quark pairs

The ATLAS Experiment observes the production of top quark pairs – a major milestone of the early LHC physics programme. As the heaviest known elementary particle with a strong coupling to the Higgs boson, the top quark is key to understanding physics at the energy frontier. As the LHC generates hundreds of millions of top quarks, the ATLAS Experiment is able to study the particle’s properties in great detail.

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The ATLAS experiment

ATLAS observes striking imbalance of jet energies in heavy ion collisions

Only 3 weeks into its first LHC heavy-ion run, ATLAS observed an unexpectedly large imbalance of energy in pairs of jets created in lead-ion collisions at the LHC. This striking effect, which is not seen in proton–proton collisions, could be a sign of strong interactions between jets and a hot, dense medium (quark-gluon plasma) formed by the colliding ions. Details studies of the effect followed this first observation.

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The ATLAS experiment

First LHC collisions at 7 TeV

ATLAS records collisions at 7 TeV centre-of-mass energy for the first time.

Particle physicists around the world anticipate a rich harvest of new physics as the LHC begins its first long run at an energy three and a half times higher than previously achieved at a particle accelerator.

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The ATLAS experiment, The Large Hadron Collider, Archive of important events in CERN's history for press

The LHC starts again after a short technical stop

After a short technical stop, beams circulate again on 28 February 2010. On 19 March 2010, two 3.5 TeV proton beams successfully circulate in the Large Hadron Collider for the first time. This is the highest energy yet achieved in a particle accelerator and an important step on the way to the start of the LHC research programme. 

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The Large Hadron Collider

The LHC is put into standby mode

On 16 December 2009, the LHC ends its first full period of operation. Collisions at 2.36 TeV set a new world record and bring to a close a successful first run for the world’s most powerful particle accelerator. The LHC is put into standby mode for a short technical stop to prepare for higher energy collisions and the start of the main research programme. Over the 2009 run, each of the LHC’s four major experiments, ALICE, ATLAS, CMS and LHCb have recorded over one million particle collisions, which are distributed for analysis around the world on the LHC computing grid. 

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The Large Hadron Collider

ATLAS records first collisions

The start of a fantastic era of physics! ATLAS records first collisions at 0.9 TeV.

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The ATLAS experiment

Beams back in the LHC

From a CERN press release, dated 20 November 2009: 

Particle beams are once again circulating in the world’s most powerful particle accelerator, CERN’s Large Hadron Collider (LHC). This news comes after the machine was handed over for operation on Wednesday morning. A clockwise circulating beam was established at ten o'clock this evening. This is an important milestone on the road towards first physics at the LHC, expected in 2010.

“It’s great to see beam circulating in the LHC again,” said CERN Director General Rolf Heuer. “We’ve still got some way to go before physics can begin, but with this milestone we’re well on the way.”

The LHC circulated its first beams on 10 September 2008, but suffered a serious malfunction nine days later. A failure in an electrical connection led to serious damage, and CERN has spent over a year repairing and consolidating the machine to ensure that such an incident cannot happen again.

“The LHC is a far better understood machine than it was a year ago,” said CERN’s Director for Accelerators, Steve Myers. “We’ve learned from our experience, and engineered the technology that allows us to move on. That’s how progress is made.”

Recommissioning the LHC began in the summer, and successive milestones have regularly been passed since then. The LHC reached its operating temperature of 1.9 Kelvin, or about -271 Celsius, on 8 October. Particles were injected on 23 October, but not circulated. A beam was steered through three octants of the machine on 7 November, and circulating beams have now been re-established. The next important milestone will be low-energy collisions, expected in about a week from now. These will give the experimental collaborations their first collision data, enabling important calibration work to be carried out. This is significant, since up to now, all the data they have recorded comes from cosmic rays. Ramping the beams to high energy will follow in preparation for collisions at 7 TeV (3.5 TeV per beam) next year.

Particle physics is a global endeavour, and CERN has received support from around the world in getting the LHC up and running again.

“It’s been a herculean effort to get to where we are today,” said Myers. “I’d like to thank all those who have taken part, from CERN and from our partner institutions around the world.”

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The Large Hadron Collider

HIE-ISOLDE project approved

(Image: The ISOLDE beamline, equipped with the first HIE-ISOLDE cryomodule in its light grey cryostat)

The HIE-ISOLDE project is a major staged upgrade of the existing ISOLDE facility. It includes an energy increase of the REX post-accelerator up to 5.5 MeV/u with a future option of going to 10 MeV/u, as well as an upgrade of the REX low energy stage capacity. The beam quality will be improved e.g. with the installation of a RFQ cooler and a new Resonant Laser Ionization System. The driver intensity will be increased from the new Linac-4 and upgrades in the intensity and energy of the PS Booster. 

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ISOLDE

Final magnet goes underground after LHC repair

The 53rd and final replacement magnet for the Large Hadron Collider (LHC) is lowered into the accelerator tunnel, marking the end of repair work above ground following the incident in September the year before that brought LHC operations to a halt.

The final magnet, a quadrupole designed to focus the beam, is lowered in the afternoon and starts its journey to Sector 3-4, the scene of the September incident. In total 53 magnets were removed from Sector 3-4 after the incident. Sixteen that sustained minimal damage were refurbished and put back into the tunnel. The remaining 37 were replaced and will be refurbished to provide spares for the future.

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The history of CERN, The Large Hadron Collider

WWW@20

On 13 March 2009, Web inventor Tim Berners-Lee returned to the birthplace of his invention, 20 years after submitting his paper ‘Information Management: A Proposal’ to his boss Mike Sendall. By writing the words ‘Vague, but exciting’ on the document’s cover, and giving Berners-Lee the go-ahead to continue, Sendall was signing into existence the information revolution of our times: the World Wide Web. In September of the following year, Berners-Lee took delivery of a computer called a NeXT cube, and by December the Web was up and running, albeit between just a couple of computers at CERN.

A celebration was held in the Globe on the afternoon of the 13th March to bring together those who created the web at CERN.

Explore the resources prepared for press on the occasion of the WWW@20 event.

Timelines
Archive of important events in CERN's history for press

"Angels and Demons" promotion at CERN

CERN today hosted a visit from actors Tom Hanks and Ayelet Zurer and director Ron Howard as they unveiled exclusively some select footage from their new film adaptation of Dan Brown’s novel Angels & Demons, set for worldwide release by Sony Pictures on 15 May 2009.

Read the full Press Release.

In Angels & Demons Tom Hanks plays Harvard academic Robert Langdon, who discovers evidence of the resurgence of an ancient secret brotherhood called the Illuminati - the most powerful underground organization in history.

When Langdon finds evidence that the Illuminati have stolen antimatter from a secret laboratory at CERN, which they plan to use as a devastating weapon to destroy the Vatican, he and CERN scientist Vittoria Vetra begin a race against time to recover the antimatter and prevent catastrophe.

But what is antimatter? Is it real? Is it dangerous? What is CERN? Find the answers to those questions and much more here.

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Archive of important events in CERN's history for press

Inauguration of the LHC

In line with Japanese tradition, this Daruma doll was painted with one eye to mark the start of the LHC project. The Japanese Vice Minister of Education, Culture, Sports, Science and Technology T. Yamauchi adds the second eye to mark the completion of the project. 

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The Large Hadron Collider

End of ATLAS construction

To celebrate the end of the ATLAS construction phase, the Collaboration hosts a party at CERN's magnet testing facility (SM18). This was the largest ATLAS celebration yet, with collaboration members travelling from around the world to mark this milestone.

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The ATLAS experiment

Incident at the LHC

On 19 September 2008, during powering tests of the main dipole circuit in Sector 3-4 of the LHC, a fault occurs in the electrical bus connection in the region between a dipole and a quadrupole, resulting in mechanical damage and release of helium from the magnet cold mass into the tunnel. Proper safety procedures are in force, the safety systems perform as expected, and no-one is put at risk.

More about the incident: 

A full technical analysis of the incident is available here

Or read an analysis of the LHC incident on CERN's press office website

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The history of CERN, The Large Hadron Collider

The LHC starts up

At 10.28am on 10 September 2008 a beam of protons is successfully steered around the 27-kilometre Large Hadron Collider (LHC) for the first time. The machine is ready to embark on a new era of discovery at the high-energy frontier.

LHC experiments address questions such as what gives matter its mass, what the invisible 96% of the universe is made of, why nature prefers matter to antimatter and how matter evolved from the first instants of the universe’s existence.

Explore the resources prepared for press.

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The history of CERN, CERN accelerators, The Large Hadron Collider, The search for the Higgs boson, Archive of important events in CERN's history for press

Final large detector piece lowered into CMS cavern

The pixel detector barrel is the last large piece of the CMS detector to be lowered into the cavern. 

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The Large Hadron Collider

Final large detector piece lowered into ATLAS cavern

A component known as a small wheel is the last large piece of the ATLAS detector to be lowered into the cavern. The ATLAS detector has the largest volume of any detector ever constructed.

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The Large Hadron Collider

Pierre Auger Observatory discovers extragalactic origin of highest-energy cosmic rays

In November 2007, the Auger project published results showing that the direction of origin of the 27 highest energy events were strongly correlated with the location of active galactic nuclei (AGN). An active galactic nucleus is a compact region at the centre of a galaxy that has a much higher than normal luminosity over at least some portion, and possibly all, of the electromagnetic spectrum. These results supported the theory that at the centre of each AGN is a large black hole exerting a magnetic field strong enough to accelerate a bare proton to energies of 1020 eV and higher.

The Auger observatory is the world’s largest and most accurate observatory for studying cosmic rays. It consists of 1600 surface detectors and 27 fluorescent telescopes and covers an area of 3000 km2. The Pierre Auger collaboration has made many low-energy incidents, which do not require physical analysis, available on the Public Event Display website. 

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Cosmic rays

ISCOOL, the RFQ Cooler and Buncher

(Image: ISCOOL, an ion cooler and buncher installed at ISOLDE)

An ion cooler and buncher, ISCOOL, is installed in the HRS section of ISOLDE. Beams with strongly reduced emittances and energy spreads are now available for all experiments downstream the beam line.

Using its bunching capabilities, ISCOOL permits an increase in the sensitivity for experiments such as those devotde to collinear laser spectroscopy. The first physics run with this device took place in July 2008 where the isotope 77Ga (T1/2=13 s) was studied with the COLLAPS laser spectroscopy setup.

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ISOLDE

Last LHC dipole magnet goes underground

The last superconducting magnet is lowered down an access shaft to the LHC. The 15-metre dipoles, each weighing 35 tonnes, are the most complex components of the machine. In total, 1232 dipoles were lowered to 50 metres below the surface via a special oval shaft. They were then taken through a transfer tunnel to their final destination in the LHC tunnel, carried by a specially designed vehicle travelling at 3 kilometres per hour.

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The Large Hadron Collider

World's largest superconducting magnet switches on

The ATLAS Barrel Toroid, then the largest superconducting magnet ever built, was switched on for the first time at CERN on 20 November 2006. The magnet is called the Barrel Toroid because of its barrel-like shape.

It provides a powerful magnetic field for ATLAS, one of the major particle detectors taking data at the Large Hadron Collider (LHC). The magnet consists of eight superconducting coils, each in the shape of a round-cornered rectangle, 5 metres wide, 25m long and weighing 100 tonnes, all aligned to millimetre precision.

The ATLAS Barrel Toroid was cooled down over a six-week period from July to August 2006 to reach –269°C . It was then powered up step-by-step to higher and higher currents, reaching 21 thousand amps for the first time during the night of 9 November. Afterwards, the current was switched off and the stored magnetic energy of 1.1 GigaJoules, the equivalent of about 10,000 cars travelling at 70 kilometres per hour, was safely dissipated, raising the cold mass of the magnet to –218°C.

Read the press release

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The history of CERN

World’s largest superconducting magnet turns on

The ATLAS Barrel Toroid, a characteristic component of the detector, then the largest superconducting magnet ever built, is switched on for the first time. It works together with the two Endcap Toroids and a central Solenoid magnet to bend the paths of charged particles produced in collisions at the LHC, enabling important properties to be measured.

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The ATLAS experiment

New experiment to investigate the effect of galactic cosmic rays on clouds and climate

The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment begins taking its first data today with a prototype detector in a particle beam at CERN, the world's largest laboratory for particle physics. The goal of the experiment is to investigate the possible influence of galactic cosmic rays on Earth's clouds and climate. This represents the first time a high energy physics accelerator has been used for atmospheric and climate science.

Studies suggest that cosmic rays may influence the amount of cloud cover through the formation of new aerosols (tiny particles suspended in the air that seed cloud droplets). Clouds exert a strong influence on the Earth's energy balance, and changes of only a few per cent have an important effect on the climate. The CLOUD prototype experiment aims to investigate the effect of cosmic rays on the formation of new aerosols.

Understanding the microphysics in controlled laboratory conditions is a key to unravelling the connection between cosmic rays and clouds. CLOUD will reproduce these interactions for the first time by sending a beam of particles – the "cosmic rays" - from CERN's Proton Synchrotron into a reaction chamber. The effect of the beam on aerosol production will be recorded and analysed.

The collaboration comprises an interdisciplinary team from 18 institutes and 9 countries in Europe, the United States and Russia. It brings together atmospheric physicists, solar physicists, and cosmic ray and particle physicists to address a key question in the understanding of clouds and climate change. 

 

Explore resources for the media.

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Cosmic rays

CMS cavern inaugurated

After six and a half years of work, CERN leaders and dignitaries celebrate the completion of a second detector cavern. The CMS cavern is 53 x 27 x 24 metres. To make space for the enormous detector, 250,000 cubic metres of soil have been removed from the detector cavern and a second space that houses technical components.

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The Large Hadron Collider

CERN celebrates its 50th birthday

CERN celebrated its 50th anniversary in style, with the inauguration of the Globe of Science and Innovation (pictured, under construction) on 19 October. A gift from the Swiss Confederation, the Globe is an iconic wooden structure first used for the Swiss national exhibition in 2002 as a pavilion dedicated to the theme of sustainable development. It was designed by architects Thomas Büchi and Hervé Dessimoz of Geneva. The Globe is being developed into a new visitor and networking centre for the Laboratory — a focal point for CERN’s interaction with society.

The inauguration of the Globe in 2004 coincided with the official celebration of CERN’s anniversary, attended by representatives of the Organization’s 20 member states including the heads of state of France, Spain and Switzerland.

Check out the website that contains a record of the activities that marked the Organization’s 50th Anniversary.

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The history of CERN, Archive of important events in CERN's history for press

Radioactive laboratory of class A at ISOLDE

(Image: A 3-D drawing of the Class A Lab with a photo inset)

The new Class A building at ISOLDE is built to enable UCx target material to be produced and irradiated targets to be handled safely. The Class A laboratory is equipped with fume cupboards, full protective measures and aerosol monitoring. It can handle 150 g UO2 per day, corresponding to two target containers.

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ISOLDE

EU DataGrid project passes final review

The aim of the European Datagrid project was to produce a "production quality" computing Grid, in anticipation of the construction of the Worldwide LHC Computing Grid. According to the project's website:

The objective is to build the next generation computing infrastructure providing intensive computation and analysis of shared large-scale databases, from hundreds of terabytes to petabytes, across widely distributed scientific communities

The project passed its third and final review at CERN on 19 February 2004. 

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Computing at CERN

LHCf submits letter of intent

The LHC forward collaboration proposes to build two small calorimeters near the ATLAS detector for high-energy cosmic ray research.

Read the LHCf letter of intent

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The Large Hadron Collider

Pierre Auger Observatory completes its 100th detector

Upon completing its 100th surface detector, the Pierre Auger Observatory became the largest cosmic-ray air shower array in the world. The Pierre Auger Observatory is a hybrid detector that uses two independent methods of detecting and studying cosmic rays. The observatory detects high-energy particles through their interaction with water placed in the surface detector tanks. The other method of detection is through tracking the development of air showers through observing the ultraviolet light emitted high in the earth’s atmosphere. 

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Cosmic rays

LHC Computing Grid phase 1 launched

The following is an extract from: "The LHC computing grid project at CERN" (Lamanna, 2004)

The first service of the LHC Computing Grid, called LCG-1 was opened on September 15th, 2003, with 25 sites worldwide. In this phase, the goal was to allow the experiments to try out the system and test their software on it. Although incomplete in functionality, in particular, due to some limitation in the data management interface to tertiary storage, LCG-1 is demonstrating very good stability and serving as a basis for the users to prepare for the 2004 data challenges.

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Computing at CERN

AMANDA sees first neutrinos in ice

The photomultiplier tubes within these basketball-sized glass orbs are at the heart of the AMANDA neutrino telescope, a novel telescope being built at the South Pole to detect cosmic neutrinos (Image: Jeff Miller)


The Antarctic Muon and Neutrino Detector Array (AMANDA) telescope - which lies buried under kilometer of ice - aims to detect high-energy cosmic neutrinos from our own or nearby galaxies. Neutrinos are mysterious particles associated with radioactive phenomena. They have little mass, no electric charge and can travel straight through the earth as they interact only very weakly with other matter. Neutrinos are numerous in the cosmos at large so have a significant influence on the events of the universe. They are present in the universe as leftovers of creation and are emitted by processes that fuel the sun. Neutrinos spill out in huge numbers from colossal stellar explosions.

The idea behind the AMANDA telescope is that neutrinos interacting with ice emit a brief flash of blue light which can be detected if the ice is clear enough. Since neutrinos are so weakly interacting, a cubic kilometer of ice is required to detect them. In the Antarctic, the ice at this depth below is as clear as a diamond because the pressure from the snow above squeezes out all the air bubbles. Consequently, the ice is clear enough that the blue light flashes caused by the interaction of neutrinos can travel undimmed for more than 100 metres to be detected by photomultipliers. Photomultipliers convert the faint light to an electric current which travels to the surface to record the interaction. When star explodes as a supernova in the galaxy, bursts of neutrinos will burst through the earth and send flashes of blue light through the Antarctic ice. After nine years of operation, AMANDA was incorporated into the full size detector, IceCube. 

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Cosmic rays

ATLAS cavern inaugurated

After three years of work, the ATLAS detector cavern (35 x 55 x 40 metres) is fully excavated and completed. CERN officials and dignitaries celebrate the first new LHC cavern on 4 June 2003, complete with an alpinhorn player.

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The Large Hadron Collider

ATLAS cavern inaugurated

After five years of innovative and ingenious civil engineering, the ATLAS detector cavern (35 x 55 x 40 metres) was fully excavated. ATLAS, CERN officials, and political authorities, including the President of the Swiss Confederation Pascal Couchepin, celebrated the inauguration of the first cavern on the Large Hadron Collider on 4 June 2003. Installation of the detector in the cavern began soon after.

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The ATLAS experiment