CERN Open Data Portal: LHC experiments open to the Public

The web-based CMS event display, accessible through the CERN Open Data Portal, shows a proton-collision event recorded by the CMS detector. 

Credit: CMS /Open Data Portal

CERN today launched its Open Data Portal where data from real collision events, produced by experiments at the Large Hadron Collider (LHC) will for the first time be made openly available to all.

It is expected that these data will be of high value for the research community, and also be used for education purposes.

"Launching the CERN Open Data Portal is an important step for our Organization. Data from the LHC programme are among the most precious assets of the LHC experiments, that today we start sharing openly with the world."

"We hope these open data will support and inspire the global research community, including students and citizen scientists," says CERN Director-General Rolf Heuer.

The principle of openness is enshrined in CERN's founding Convention, and all LHC publications have been published Open Access, free for all to read and re-use.

Widening the scope, the LHC collaborations recently approved Open Data policies and will release collision data over the coming years.

The first high-level and analysable collision data openly released come from the CMS experiment and were originally collected in 2010 during the first LHC run.

This data set is now publicly available on the CERN Open Data Portal. Open source software to read and analyse the data is also available, together with the corresponding documentation.

The CMS collaboration is committed to releasing its data three years after collection, after they have been thoroughly studied by the collaboration.

"This is all new and we are curious to see how the data will be re-used," says CMS data preservation coordinator Kati Lassila-Perini.

"We've prepared tools and examples of different levels of complexity from simplified analysis to ready-to-use online applications. We hope these examples will stimulate the creativity of external users."

In parallel, the CERN Open Data Portal gives access to additional event data sets from the ALICE, ATLAS, CMS and LHCb collaborations, which have been specifically prepared for educational purposes, such as the international masterclasses in particle physics benefiting over ten thousand high-school students every year. These resources are accompanied by visualisation tools.

"Our own data policy foresees data preservation and its sharing. We have seen that students are fascinated by being able to analyse LHC data in the past and so, we are very happy to take the first steps and make available some selected data for education" says Silvia Amerio, data preservation coordinator of the LHCb experiment.

"The development of this Open Data Portal represents a first milestone in our mission to serve our users in preserving and sharing their research materials. It will ensure that the data and tools can be accessed and used, now and in the future," says Tim Smith of the CERN IT Department.

All data on OpenData.cern.ch are shared under a Creative Commons CC0 public domain dedication; data and software are assigned unique DOI identifiers to make them citable in scientific articles; and software is released under open source licenses.

The CERN Open Data Portal is built on the open-source Invenio Digital Library software, which powers other CERN Open Science tools and initiatives.

ESA XMM-Newton: Inexplicable signal provides clue about dark matter

A sketch (not to scale) showing axions (blue) streaming out from the Sun, converting in the Earth's magnetic field (red) into X-rays (orange), which are then detected by the XMM-Newton observatory. 

Credit: University of Leicester

Cutting-edge paper by Professor George Fraser, who tragically died in March this year,and colleagues at the University of Leicester provides first potential indication of direct detection of Dark Matter, something that has been a mystery in physics for over 30 years.

Space scientists at the University of Leicester have detected a curious signal in the X-ray sky – one that provides a tantalising insight into the nature of mysterious Dark Matter.

The Leicester team has found what appears to be a signature of 'axions', predicted 'Dark Matter' particle candidates, something that has been a puzzle to science for years.

In a study being published on Monday 20 October in the Monthly Notices of the Royal Astronomical Society, the University of Leicester scientists describe their finding of a signal which has no conventional explanation.

As first author Professor George Fraser, who sadly died in March of this year, wrote: "The direct detection of dark matter has preoccupied physics for over thirty years."

Dark Matter, a kind of invisible mass of unknown origin, cannot be seen directly with telescopes, but is instead inferred from its gravitational effects on ordinary matter and on light.

Dark Matter is believed to make up 85% of the matter of the Universe.

"The X-ray background, the sky, after the bright X-ray sources are removed - appears to be unchanged whenever you look at it," explained Dr. Andy Read, also from the University of Leicester Department of Physics and Astronomy and now leading the paper.

"However, we have discovered a seasonal signal in this X-ray background, which has no conventional explanation, but is consistent with the discovery of axions."

This result was found through an extensive study of almost the entire archive of data from the European Space Agency's X-ray observatory, XMM-Newton, which will celebrate its 15th year in orbit this December.

Previous searches for axions, notably at CERN, and with other spacecraft in Earth orbit, have so far proved unsuccessful.

As Professor Fraser explains in the paper: "It appears plausible that axions, Dark Matter particle candidates, are indeed produced in the core of the Sun and do indeed convert to X-rays in the magnetic field of the Earth."

It is predicted that the X-ray signal due to axions will be greatest when looking through the sunward side of the magnetic field because this is where the field is strongest.

Dr. Read concludes: "These exciting discoveries, in George's final paper, could be truly ground-breaking, potentially opening a window to new physics, and could have huge implications, not only for our understanding of the true X-ray sky, but also for identifying the Dark Matter that dominates the mass content of the cosmos."

President of the Royal Astronomical Society Professor Martin Barstow, who is Pro-Vice-Chancellor, Head of the College of Science & Engineering and Professor of Astrophysics & Space Science at the University of Leicester said: "This is an amazing result. If confirmed, it will be first direct detection and identification of the elusive dark matter particles and will have a fundamental impact on our theories of the Universe."

More information: "Potential solar axion signatures in X-ray observations with the XMM-Newton observatory," G. W. Fraser, A. M. Read, S. Sembay, J. A. Carter, E. Schyns, Accepted (08/09/14) for publication in Monthly Notices of the Royal Astronomical Society (mnras.oxfordjournals.org/), Paper can be found on arXiv : arxiv.org/abs/1403.2436.

HADES: Continues search for Dark Matter Beyond the Standard Model

HADES at the GSI in Darmstadt, Germany searches for dark matter candidates. 

Credit: 3-D Rendering: A. Schmah /HADES

Although Dark Energy and Dark Matter appear to constitute over 95 percent of the universe, nobody knows of which particles they are made up.

Astrophysicists now crossed one potential Dark Matter candidate, the Dark Photon or U boson, off the list in top position.

This is the result of recent HADES experiments, where researchers from the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) and from 17 other European institutes try to pin down the nature of Dark Matter.

These negative results, recently published in Physics Letters B, could even lead to challenges of the Standard Model of particle physics.

The interpretation of current astrophysical observations results in the striking mass-energy budget of matter in the universe: 75% Dark Energy and 20% Dark Matter. Only about 5% of the universe consists of "ordinary", baryonic matter.

Many attempts have been made to explain the nature of Dark Matter. Researchers believe that Dark Matter is comprised by hitherto unknown particles which do not fit into the Standard Model of particle physics.

The Standard Model is a theoretically sound quantum field theory with fundamental matter particles, such as quarks (bound in hadrons, e.g., baryons) and leptons (e.g., electrons and neutrinos), which interact via exchange of force-carrier quanta, called gauge bosons (e.g., photons).

Some of these species acquire their masses by the interaction with the Higgs boson.

While evidences for the Higgs boson were found recently at CERN, the Standard Model looks now complete when supplemented by some neutrino masses, and nothing else seems to be needed to understand the wealth of atomic, sub-nuclear and particle physics phenomena.

Nevertheless, Dark Matter appears not to be explained by any of the constituents of the Standard Model.

This status of the affair has initiated worldwide efforts to search for Dark Matter candidates.

Beyond the Standard Model
Searching a needle in the haystack is simpler: one knows both the wanted object (the needle) and the place (the haystack).

In the case of Dark Matter the object is unknown, and the localisation, e.g. in galactic halos, is also not constraining the loci of interest.

To specify the search goal one can envisage diverse hypothetical candidates, such as certain hypothetical particles beyond the Standard Model, which fulfill requirements qualifying them as constituents of Dark Matter.

Dark Energy drives the presently observed accelerated expansion of the universe. Dark Energy is homogeneously distributed and can be attributed to a cosmological constant or vacuum energy.

In extreme cases it may cause, in the future, such a sudden expansion that anything in the universe is disrupted, this would be the Big Rip.

Dark Matter, in contrast, is bumpy and is needed to explain the formation of the observed density distribution of visible matter in the evolving universe, evidenced by the hierarchy of structures from (super)clusters of galaxies, galaxies, stars, planets and other compact objects such as meteorites, etc.

Among the lists of candidates of Dark Matter is a hypothetical particle, often dubbed U boson or Dark Photon.

These nicknames refer to the underlying theory construction: a second unitary ("U") symmetry allows for quanta which are, in one respect, similar to photons, namely gauge bosons, but in another respect different from photons, namely attributing to these quanta a mass, making them to Dark Photons because of a very weak interaction with normal matter.

Very similar to photons the Dark Photons can decay into electron-positron pairs, if they have the proper virtuality.

Combining the chain of hypotheses one arrives at a scenario, where an "ordinary" virtual photon converts into a Dark Photon which decays afterwards into an electron-positron pair.

Background on HADES
HADES is an acronym of High-Acceptance Di-Electron Spectrometer.

It is an optimised detector system operated by a European collaboration of about hundred physicists at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt.

HADES is aimed at investigating virtual photon signals emitted as electron-positron pairs off compressed nuclear matter to understand the origin of the phenomenon "masses of hadrons" and test it in some detail.

The highly sophisticated apparatus HADES has the capability to select electron-positron pairs, which can be attributed to primary sources, out of a huge background of other particles .

Read the full article here

More information: G. Agakishiev et al. (HADES Collaboration), Phys. Lett. B 731, 265 (2014) dx.doi.org/10.1016/j.physletb.2014.02.035

CERN: World Record Current in Superconductor

The 20-metre long electrical transmission line containing the two 20 kA MgB2cables. 

Credit: CERN

In the framework of the High-Luminosity LHC project, experts from the CERN Superconductors team recently obtained a world-record current of 20 kA at 24 K in an electrical transmission line consisting of two 20-metre long cables made of magnesium diboride (MgB2) superconductor.

This result makes the technology a viable solution for long-distance power transportation.

"The test is an important step in the development of cold electrical power transmission systems based on the use of MgB2," says Amalia Ballarino, head of the Superconductors and Superconducting Devices section at CERN.

"The cables and associated technologies were designed, developed and tested at CERN."

"The superconducting wire is the result of a long R&D effort that started in 2008 between CERN and the manufacturer, Columbus Superconductors in Genova, Italy."

The result was achieved at a temperature of 24 K (about -249 ˚C) using a test station that was purpose-designed and assembled at CERN.

The temperature is kept homogeneous over the 20-metre length of the line by a forced flow of helium gas.

Following intense development, the full 2 x 20-metre long MgB2 superconducting line was successfully powered to the world-record current of 20 kA, showing that this technology has great potential for the transmission of electrical power.

The superconducting properties of this relatively cheap material were discovered in 2001, but conductor technology only existed in the form of tape.

Round wire, which is more appropriate for assembling into high-current cables, was not available when the CERN project started.

"First, it was necessary to develop quality round wires adapted for use in this project, with high current density and uniform superconducting properties," says Ballarino.

"This work was done through a close collaboration between CERN and Columbus Superconductors, which manufactured different generations of wires with different architectures and with improved properties. In parallel, we at CERN developed the high-current cables and the electrical transmission line."

CERN LHC: Team announces beginning of restart

The team of scientists working at CERN's Large Hadron Collider (LHC) facility has reported to the press that the process of restarting the massive experimental mechanism has begun—though it won't finish until sometime next year. 

The world's most complicated system of machines will have to be restarted in pieces to ensure that each is operating properly before the next can be brought online.

Though proving the existence of the Higgs boson was a major goal, and achieving it garnered a lot of headlines, the facility at CERN has made progress in other areas as well, the creation of quark, gluon plasma back in 2011, is but one example.

Now the facility is in the process of an upgrade, which has been in the planning stages for several years and will include upgrades to several pieces and parts of the facility that support the LHC as well as the main accelerator itself.

The team recognized that the facility had begun to suffer from diminishing returns and that many parts could be improved due to the development of new technology and improvements on old ways of doing things.

Thus, this past February the LHC, along with other parts and accelerators that feed it, was shut down.

The retooling has been forecast to total approximately $4.4 billion dollars.

Thus far, the team has successfully restarted the part they call the source—the piece of equipment responsible for stripping electrons off of hydrogen atoms for use in producing protons.

Next up the team plans to fire up Linac2, an accelerator whose job it is to give protons their initial push.

After that a booster will be started that will be used to push the protons even faster.

For the LHC to be used in its proper context, it must receive protons that are already moving exceedingly fast.

Team members have made much of the complete upgrade to the control system for the LHC, the part that integrates all of the systems and which of course will be central to a successful reboot.

They should know early on if there are any problems. In addition to swapping out parts for new and improved technology, technicians will also be replacing worn cables or other minor but necessary components.

If all goes well, the LHC should be ready and back in business sometime early next year. Projects in the pipeline include: ALICE, CMS, ATLAS and LHCb.

ESA and CERN sign cooperation agreement

ESA, the European Space Agency, and CERN, the European Organisation for Nuclear Research, signed a cooperation agreement on 28 March to foster future collaborations on research themes of common interest.

This year, CERN is celebrating its 60th anniversary as ESA is celebrating 50 years of European space activities.

Mauro Dell'Ambrogio

Mauro Dell'Ambrogio, the State Secretary for Education, Research and Innovation of Switzerland, highlighted how the two institutions complement each other as examples of successful European collaboration and worldwide excellence in science and technology: "CERN and ESA are two examples that attest to the approach of European collaboration for global benefit."

Genevieve Fioraso

Genevieve Fioraso, Minister for Higher Education and Research of France, stated that, "This cooperation agreement brings concrete expression to the long shared history of two international organisations that are emblematic of the strength of European science: CERN and ESA.

"This joining together in the exploration of the infinite, from the infinitely large that is the focus of the sciences of the Universe to the infinitely small in high energy physics, opens up new avenues for science and technology, bringing progress and strengthening European industry."

"ESA and CERN are the daughters of visionaries like Edoardo Amaldi, testimony that, when we share the same challenging objectives and join forces, Europe is at the leading edge of progress, innovation and growth," said Jean-Jacques Dordain, ESA's Director General.

Large Hadron Collider's CMS Tracker: Cool running required

The CMS Tracker Outer Barrel (TOB) shown in a clean room before its installation into the detector in 2008. 

Credit: Maximilien Brice/CERN 

By successfully passing a recent 'Master Cold Test', the CMS experiment Tracker has proved it can run at temperatures colder than ever before. 

It is now in shape to operate until 2025.

This Tracker, the closest subdetector to the collision point of Large Hadron Collider (LHC) particle beams, must face an onslaught of billions of particles flying through it each second of operation.

If the Tracker was operated at room temperatures, damage from this onslaught would soon render it inoperable.

So during the LHC's first run from 2010 to 2013, the Tracker operated at +4 °C, but with higher LHC beam intensities from 2015 onwards, the Tracker must operate at much colder temperatures, posing a monumental challenge to the Tracker community.

However, after two years of planning and one year of work, they have succeeded.

To achieve lower temperatures, many projects ran in parallel. The CMS cooling plant was refurbished and the fluorocarbon cooling system completely overhauled.

New methods for vapour-sealing and insulation helped suppress humidity inside the Tracker and several hundred high-precision sensors have improved humidity and temperature monitoring.

A new dry-gas plant now provides eight times as much dry gas (air or nitrogen) than before to help keep humidity away from the delicate electronics, and allows fine-grained regulation of the flow.

In addition, all cooling bundles outside the Tracker were equipped with heater wires and temperature sensors to guarantee safe operation in the future.

As a result, in early 2014 the Tracker successfully passed the important 'Master Cold Test' milestone, running the Strip Tracker at temperatures down to −20 °C with the Pixel Tracker lines going to −25 °C.

The subdetector was monitored continuously and performed as expected, without affecting the temperature of surrounding layers of the Electromagnetic Calorimeter, which operate at +18 °C.

Environmental conditions allow operation at −25 °C and the detector has been successfully operated at −20 °C.

To minimise thermal stress, researchers are discussing operating the Strip Tracker at −15 °C and the Pixel Tracker at −20 °C for the coming years.

With this milestone, the Tracker project has completed the bulk of its work for Long Shutdown 1 of the LHC.

The detector can now be operated cold with a sufficient safety margin. The team are now ready to track particles until Long Shutdown 3.

CERN Future Circular Collider (FCC): Europe's new giant particle collider

Europe's physics lab CERN said Thursday it was eyeing plans for a circular particle collider that would be seven times more powerful than the facility which discovered the famous "God particle."

"The time has come to look even further ahead," the European Organisation for Nuclear Research (CERN) announced.

In 2012, CERN's Large Hadron Collider (LHC)—a giant lab housed in a 27-kilometre (17-mile) tunnel straddling the French-Swiss border—identified what is believed to be the Higgs boson, the long-sought maker of mass theorised in the 1960s.

The facility flushed out the so-called God particle by crashing proton beams at velocities near the speed of light. It went offline a year ago for an 18-month overhaul.

The LHC, completed in 2008, has "at least 20 more years" of life in it, the agency said.

However, the long time needed to build its successor—the LHC took a quarter of a century—means that planning should start now.

It will launch a feasibility study next week for a so-called Future Circular Collider (FCC) with a circumference of 80 to 100 kilometres (50 to 60 miles).

The FCC would probably be located in the same area and may incorporate the LHC tunnel in its infrastructure, CERN said in a statement.

The LHC after its overhaul will see collision energies reach 14 teraelectron volts (TeV) but the FCC should be capable of reaching unprecedented smashups of around 100 TeV, CERN said.

The FCC study will run in parallel with an ongoing probe into an alternative design—an 80-kilometre (50-mile) straight collider dubbed the Compact Linear Collider (CLIC).

The two studies will examine the feasibility and costs and produce conceptual designs by 2018/2019, when the European-wide strategy on particle physics research is set to be updated.

The winner will be "a worthy successor to the LHC," CERN said.

"Such an accelerator would allow particle physics to push back the boundaries of knowledge even further," it claimed.

Targets could include supersymmetry, the notion that there are novel particles which mirror each known particle.

It could also help shed light on dark matter, which comprises most of the cosmos and whose existence is inferred from their impact on ordinary matter.

Some 300 scientists will meet at the University of Geneva from February 12-15 to kick off the five-year feasibility study for the FCC.

Lawrence Livermore to build US$45m Super Laser for ELI facility in Czech Republic

Representatives for Lawrence Livermore National Laboratory (LLNL) have announced that researchers and engineers there have been hard at work constructing a "High Repetition-Rate Advanced Petawatt Laser System" (HAPLS) —a laser unlike anything else ever built.

The new laser once finished will be transported to Dolní Břežany near Prague, site of the European Union's Extreme Light Infrastructure (ELI), ELI Beamlines

ELI Beamlines is a project similar to CERN, in that its development is the result of International cooperation and investment—though both remain firmly European based.

ELI Beamlines is to become for lasers what CERN has been for particle accelerators—a facility for the world's best scientists to conduct leading edge experiments—it will house some of the most powerful and advanced lasers ever built.

A CAD image of the ELI-HAPLS laser.

Among that collection will be HAPLS, a laser that produces rapidly flickering (10 per second) beams, each just 30 femtoseconds in duration at 30 joules a shot—100 times more powerful than LLNL's most powerful laser to date—with peak power greater than 1 petawatt.

In so doing it will be capable of generating secondary sources of radiation and speeding up charged particles.

That will make it ideally suited for an enormous variety of research applications—from biology to physics and medicine—even to materials science.

Scientists also envision a whole host of industrial research applications as well.

Scientists around the world are expected to be drawn to ELI Beamlines to use the lasers to test theories regarding the cosmos—to emulate what happens with pulsars, for example or to gain more understanding of how matter behaves inside of different stars—all possible because the energy from the short bursts of laser light will be on par with such massive energy producers, if only for a very short period of time.

HAPLS is also considered as a possible blueprint for the construction of nuclear fusion facilities some time in the distant future.

ELI Beamlines is projected to come online in 2017 and to go into full operation the year after, offering scientists unprecedented access to extraordinarily powerful lasers—what they learn as a result could have far reaching implications well into the future.

More information: www.llnl.gov/news/newsreleases/2013/

CERN ASACUSA experiment produces first beam of antihydrogen atoms for hyperfine study

A photograph of multiple ring electrodes installed in the cusp magnet. 

Antihydrogen atoms are synthesised inside the left cylinders and are analysed at the right electrodes by the field ionisation technique. 

Credit: N. Kuroda

The ASACUSA experiment at CERN has succeeded for the first time in producing a beam of antihydrogen atoms.

In a paper published today in Nature Communications, the ASACUSA collaboration reports the unambiguous detection of 80 antihydrogen atoms 2.7 metres downstream of their production, where the perturbing influence of the magnetic fields used initially to produce the antiatoms is small.

This result is a significant step towards precise hyperfine spectroscopy of antihydrogen atoms.

Primordial antimatter has so far never been observed in the Universe, and its absence remains a major scientific enigma.


Nevertheless, it is possible to produce significant amounts of antihydrogen in experiments at CERN by mixing antielectrons (positrons) and low energy antiprotons produced by the Antiproton Decelerator.

The spectra of hydrogen and antihydrogen are predicted to be identical, so any tiny difference between them would immediately open a window to new physics, and could help in solving the antimatter mystery.

With its single proton accompanied by just one electron, hydrogen is the simplest existing atom, and one of the most precisely investigated and best understood systems in modern physics.

Thus comparisons of hydrogen and antihydrogen atoms constitute one of the best ways to perform highly precise tests of matter/antimatter symmetry.

Matter and antimatter annihilate immediately when they meet, so aside from creating antihydrogen, one of the key challenges for physicists is to keep antiatoms away from ordinary matter.

To do so, experiments take advantage of antihydrogen's magnetic properties (which are similar to hydrogen's) and use very strong non-uniform magnetic fields to trap antiatoms long enough to study them.

However, the strong magnetic field gradients degrade the spectroscopic properties of the (anti)atoms.

To allow for clean high-resolution spectroscopy, the ASACUSA collaboration developed an innovative set-up to transfer antihydrogen atoms to a region where they can be studied in flight, far from the strong magnetic field.

The ASACUSA CUSP apparatuses in the CERN Antiproton Decelerator. 

Credit: N. Kuroda

"Antihydrogen atoms having no charge, it was a big challenge to transport them from their trap."

"Our results are very promising for high-precision studies of antihydrogen atoms, particularly the hyperfine structure, one of the two best known spectroscopic properties of hydrogen."

Yasunori Yamazaki

"Its measurement in antihydrogen will allow the most sensitive test of matter/antimatter symmetry. We are looking forward to restarting this summer with an even more improved set-up," said Yasunori Yamazaki of RIKEN, Japan, a team leader of the ASACUSA collaboration.

The next step for the ASACUSA experiment will be to optimize the intensity and kinetic energy of antihydrogen beams, and to understand better their quantum state.

Experimental concept of the planned in-flight antihydrogen hyperfine spectroscopy. 

Antihydrogen atoms are synthesised in the cusp trap (shown with magnetic field lines in the left).

Some of them flow out towards the downstream (right) direction and are detected at the end. 

Credit: E. Widmann and N. Kuroda

Progress with antimatter experiments at CERN has been accelerating in recent years.

In 2011, the ALPHA experiment announced trapping of antihydrogen atoms for 1000 seconds and reported observation of hyperfine transitions of trapped antiatoms in 2012.

In 2013, the ATRAP experiment announced the first direct measurement of the antiproton's magnetic moment with a fractional precision of 4.4 parts in a million.

More information: Paper: dx.doi.org/10.1038/ncomms4089

CERN ATLAS experiment: Higgs boson decays to two tau particles

The ATLAS detector, open during a recent technical stop. 

Credit: Maximilien Brice /CERN

The ATLAS experiment at CERN has released preliminary results that show evidence that the Higgs boson decays to two tau particles.

Taus belong to a group of subatomic particles called the fermions, which make up matter.

This result – measured at 4.1 sigma on the 5-point scale particle physicists use to determine the certainty of a result – is the first evidence for a Higgs decay to fermions.

On 4 July 2012, the ATLAS and CMS experiments at CERN announced the discovery of a new particle, which was later confirmed to be a Higgs boson.

For physicists, the discovery meant the beginning of a quest to find out what the new particle was, if it fit in the Standard Model, our current model of nature in particle physics, or if its properties could point to new physics beyond that model.

An important property of the Higgs boson that ATLAS physicists are trying to measure is how it decays.

The Higgs boson lives only for a short time and disintegrates into other particles. The various possibilities of the final states are called decay modes.

So far, ATLAS physicists had found evidence that the Higgs boson decays into different types of gauge bosons - the kind of elementary particles that carry forces.

The other family of fundamental particles, the fermions, make up matter. The tau is a fermion and behaves like a very massive electron.

Graphical representation of a Higgs boson decaying to two tau particles in the ATLAS detector. 

The taus decay into an electron (blue line) and a muon (red line) 

Credit: ATLAS

The Brout-Englert-Higgs mechanism was first proposed to describe how gauge bosons acquire mass but the Standard Model predicts that fermions also acquire mass in this manner, so the Higgs boson could decay directly to either bosons or fermions.

The new preliminary result from ATLAS shows clear evidence that the Higgs boson indeed does decay to fermions, consistent with the rate predicted by the Standard Model.

This important finding was made possible through careful analysis of data produced by the LHC during its first run.

Only with new data will physicists be able to determine if the compatibility remains or if other new models become viable.

Fortunately, the next LHC run, which begins in 2015, is expected to produce several times the existing data sample. In addition, the proton collisions will be at higher energies, producing Higgs bosons at higher rates.

CERN: LHC celebrates five years of not destroying the world

Universe’s secrets are revealed in a dark corner in Switzerland. Credit: timtom.ch

Five years ago, at breakfast time, the world waited anxiously for news from CERN, the European Organization for Nuclear Research.

The first nervy bunch of protons were due to be fired around the European lab's latest and biggest particle accelerator, the Large Hadron Collider (LHC), as it kicked into action.

Some "mercifully deluded people" – as Jeremy Paxman put it – feared the LHC would do no end of mischief.

There was talk of planet-swallowing black holes, the transformation of the Earth into a new state of "strange" matter, and even the prospect of the obliteration of the entire universe.

But for those of more sensible dispositions, the LHC's first beam was an occasion for great excitement.

As the protons sped all the way round the 27km tunnel under the countryside between Lake Geneva and the Jura Mountains, thousands of physicists and engineers celebrated decades of hard work, incredible ingenuity and sheer ambition.

Lyn Evans

Together they had created the largest-ever scientific experiment. After the LHC was switched on, project leader Lyn Evans said, "We can now look forward to a new era of understanding about the origins and evolution of the universe."

Operating a massive particle accelerator requires much more than flicking a switch – thousands of individual elements have to all come together, synchronised in time to less than a billionth of a second.

University College London's physicist Jon Butterworth recalls a "particularly bizarre memory" from that day.

Relaxing in a Westminster pub after an exhausting LHC event in London, Butterworth found he could follow live updates from his own ATLAS experiment on the pub's TV.

Particle physics continued to make news. The following fortnight's joy turned to dismay as an accident involving six tonnes of liquid helium erupting violently in the tunnel – euphemistically referred to as "the incident" – damaged around half a mile of the collider, closing the LHC for a year.

Post Higgs breakthrough, CERN readies for next cosmic quest

A view of the detector in the 12,500-ton Compact Muon Solenoid experiment (CMS). Image courtesy of CERN

A year ago, the world's largest particle collider made one of the greatest discoveries in the history of science, identifying what is believed to be the Higgs Boson—the long-sought maker of mass.

Today, its computer screens are dark, the control desks unstaffed and the giant, supercooled tunnel empty of the crashing proton beams whose snapshots of the Big Bang helped flush out the elusive particle.

But the silence is an illusion.

Behind the scenes, work is pushing ahead to give the vast machine a mighty upgrade, enabling it to advance the frontiers of knowledge even farther.

The 27-kilometre (17-mile) circular lab, straddling the French-Swiss border 100 metres (325 feet) underground, went offline in February for an 18-month overhaul.

When experiments resume in 2015, scientists at the European Organisation for Nuclear Research (CERN) will use its enhanced power to probe dark matter, dark energy and supersymmetry—ideas considered as wild as the Higgs Boson was, half a century ago.

As engineers focus on the technical mission, physicists are sifting through the mountains of data that the Large Hadron Collider (LHC) has churned out since 2010, for there could be more nuggets to find.

"The things that are easy to spot have already been exploited, and now we're taking another look," said Tiziano Camporesi of CERN, noting wryly that dealing with the unknown was, well, unknowable.

"We always say that astronomers have an easier task, because they can actually see what they're looking for!"

The LHC's particle collisions transform energy into mass, the goal being to find fundamental particles in the sub-atomic debris that help us to understand the Universe. At peak capacity, the "old" LHC managed a mind-boggling 550 million collisions per second.

"We give the guys as many collisions as we can," said Mike Lamont, head of its operating team. "That's our bread and butter."

"Most of that stuff is not very interesting, so there are real challenges sorting out and throwing most of that away, and picking out the interesting stuff," he explained in the tunnel, which mixes installations fit for a starship with the low-tech practicality of bicycles for inspection tours.

CERN LHC: New results indicate that Higgs boson particle is discovered

Event display of a H -> 4mu candidate event with m(4l) = 124.1 (125.1) GeV without (with) Z mass constraint. 

The masses of the lepton pairs are 86.3 GeV and 31.6 GeV. 

The event was recorded by ATLAS on 10-Jun-2012, 13:24:31 CEST in run number 204769 as event number 71902630.

Zoom into the tracking detector. Muon tracks are coloured red. 

Credit: ATLAS Experiment © 2012 CERN

At the Moriond Conference today, the ATLAS and CMS collaborations at CERN's Large Hadron Collider (LHC) presented preliminary new results that further elucidate the particle discovered last year.

Having analysed two and a half times more data than was available for the discovery announcement in July, they find that the new particle is looking more and more like a Higgs boson, the particle linked to the mechanism that gives mass to elementary particles.

It remains an open question, however, whether this is the Higgs boson of the Standard Model of particle physics, or possibly the lightest of several bosons predicted in some theories that go beyond the Standard Model. Finding the answer to this question will take time.

Whether or not it is a Higgs boson is demonstrated by how it interacts with other particles, and its quantum properties. For example, a Higgs boson is postulated to have no spin, and in the Standard Model its parity -- a measure of how its mirror image behaves -- should be positive.

CMS and ATLAS have compared a number of options for the spin-parity of this particle, and these all prefer no spin and positive parity. This, coupled with the measured interactions of the new particle with other particles, strongly indicates that it is a Higgs boson.

"The preliminary results with the full 2012 data set are magnificent and to me it is clear that we are dealing with a Higgs boson though we still have a long way to go to know what kind of Higgs boson it is." said CMS spokesperson Joe Incandela.

"The beautiful new results represent a huge effort by many dedicated people. They point to the new particle having the spin-parity of a Higgs boson as in the Standard Model. We are now well started on the measurement programme in the Higgs sector," said ATLAS spokesperson Dave Charlton.

To determine if this is the Standard Model Higgs boson, the collaborations have, for example, to measure precisely the rate at which the boson decays into other particles and compare the results to the predictions.

The detection of the boson is a very rare event -- it takes around 1 trillion (1012) proton-proton collisions for each observed event. To characterize all of the decay modes will require much more data from the LHC.

The above story is reprinted from materials provided by CERN, the European Organization for Nuclear Research.

Higgs Particle Discovery: CERN LHC prepares for data pile-up

The world’s largest particle accelerator is roaring along at an unprecedented pace, delivering torrents of data to its physicist handlers. But the hundreds of millions of collisions happening inside the machine every second are now growing into a thick fog that, paradoxically, threatens to obscure a fabled quarry: the Higgs boson.

The problem is known as pile-up, and it promises to be one of the greatest challenges this year for scientists working on the Large Hadron Collider (LHC) at CERN, Europe’s main high-energy physics laboratory near Geneva, Switzerland.

Huge amounts of computing power, cunning software and technical tricks are helping scientists to stay ahead of the problem. But researchers may still need to scale back the collisions to find the long-sought Higgs, the manifestation of a field that is believed to confer mass on other particles.

If it exists, the Higgs will appear fleetingly inside the machine before decaying into lighter particles. Last year, the two biggest detectors at the LHC saw hints of a Higgs with a mass of about 125 gigaelectronvolts (energy and mass are interchangeable in particle physics). This year, researchers want to collect more data to see whether that signal grows into a certainty, or withers back to nothing.

Since it began its latest science run last month, the LHC has been squeezing trillions of protons into ever-smaller bunches, and smashing those bunches together tens of millions of times per second.

The resultant data are measured in inverse femtobarns (fb⁻¹), a unit roughly equivalent to 100 trillion collisions. In the past month alone, the LHC recorded 1 fb⁻¹ worth of collisions. By the end of the year it aims have captured at least 15 fb⁻¹ (see ‘Smashing!’).

The Trouble With Neutrinos That Outpaced Einstein’s Theory

The British astrophysicist Arthur S. Eddington once wrote, “No experiment should be believed until it has been confirmed by theory.”

So when a group of physicists going by the acronym Opera announced in September that a batch of the strange subatomic particles known as neutrinos had traveled faster than the speed of light in a 457-mile trip through the earth, the first response among many physicists was to wonder what had gone wrong with the experiment. 

After all, Albert Einstein’s theory of relativity, which proclaimed the speed of light as the cosmic speed limit, is the foundation of modern science and has been shown to work to exquisite precision zillions of times. 

Knock it down and you potentially open the door to all kinds of things, like the ability to go back in time and kill your grandfather.

That, of course, did not stop the rest of us in the physics bleachers from dragging the old guru of space-time by his frizzy coronal hair into the media version of the public square and crowing that, perhaps this time at last, Einstein was finally going to be proved wrong. 

Neutrino jokes proliferated on the Internet, as well as this rousing song by the Corrigan Brothers and Pete Creighton: 

Tooraloo, tooraloo, tooraloo, tooralino,

Is light now slower than a neutrino?

Now it seems that Einstein’s six-month nightmare may be over.

Last week another team of physicists whose apparatus lives right next door to the Opera group — under Gran Sasso mountain in Italy — reported that they had clocked neutrinos, produced in an accelerator at CERN, outside Geneva, racing over the same path to Gran Sasso at the speed of light and not a whit faster. 

Which is exactly how fast scientists had always thought the enigmatic particles, with barely zilch for mass, should go.

The second group, which goes by the acronym Icarus, was led by Carlo Rubbia, a former director of CERN and a Nobel-winning physicist, who called the results “very convincing.”

Physicists swung into line with great sighs of relief.

“The evidence is beginning to point toward the Opera result being an artifact of the measurement,” said CERN’s research director, Sergio Bertolucci.

Cue the famous picture of Einstein sticking out his tongue. As it happened, the Icarus result was announced on March 16, two days after his 133rd birthday — almost in time for the cake.

Adding to the sense of finality was the simple fact — as Eddington might have pointed out — that faster-than-light neutrinos had never been confirmed by theory. Or as John G. Learned, a neutrino physicist at the University of Hawaii, put it in an e-mail, “An interesting result of all this fracas is that no new model I have seen (or heard of from my friends) really is credible to explain the faster-than-light neutrinos.”

During a panel discussion recently at the American Museum of Natural History, Sheldon L. Glashow, a physics professor and Nobel laureate from Boston University, said the best theory he had heard was that the neutrinos had behaved lawfully in Switzerland and speeded up when they crossed the border into Italy.

Eddington’s dictum is not as radical as it might sound. He made it after early measurements of the rate of expansion of the universe made it appear that our planet was older than the cosmos in which it resides — an untenable notion.

“It means that science is not just a book of facts, it is understanding as well,” explained Michael S. Turner, a cosmologist at the University of Chicago, who says the Eddington saying is one of his favourites. 

If a “fact” cannot be understood, fitted into a conceptual framework that we have reason to believe in, or confirmed independently some other way, it risks becoming what journalists like to call a “permanent exclusive” wrong. 

Read more of this article: The Trouble With Neutrinos - NYTimes.com

CERN: OPERA Feb 2012 Update on Neutrinos

The OPERA collaboration has informed its funding agencies and host laboratories that it has identified two possible effects that could have an influence on its neutrino timing measurement. These both require further tests with a short pulsed beam.

If confirmed, one would increase the size of the measured effect, the other would diminish it. The first possible effect concerns an oscillator used to provide the time stamps for GPS synchronizations.

It could have led to an overestimate of the neutrino's time of flight. The second concerns the optical fibre connector that brings the external GPS signal to the OPERA master clock, which may not have been functioning correctly when the measurements were taken.

If this is the case, it could have led to an underestimate of the time of flight of the neutrinos. The potential extent of these two effects is being studied by the OPERA collaboration.

New measurements with short pulsed beams are scheduled for May.

CERN LHC: Particle collider to get energy boost

European particle physicists say the Large Hadron Collider in Switzerland will be run at higher energies in 2012 than in previous years

The higher energy 4 Tev level, 0.5 higher than levels used in 2010 and 2011, will allow the LHC to deliver the maximum possible amount of data this year before it goes into a long shutdown to prepare for even higher-energy running, a release from CERN headquarters in Geneva said Tuesday.

"When we started operating the LHC for physics in 2010, we chose the lowest safe beam energy consistent with the physics we wanted to do," Steve Myers, CERN's director for accelerators and technology, said.

"Two good years of operational experience with beam and many additional measurements made during 2011 give us the confidence to safely move up a notch, and thereby extend the physics reach of the experiments before we go into the LHC's first long shutdown."

In the last two years, the LHC has concentrated on narrowing the search for the Higgs boson, considered the foundation particle of particle physics.

However, to confirm its discovery or to rule out the Standard Model Higgs particle altogether will require one more year's worth of data, researchers said.

"By the time the LHC goes into its first long stop at the end of this year, we will either know that a Higgs particle exists or have ruled out the existence of a Standard Model Higgs," CERN's research director, Sergio Bertolucci, said.

"Either would be a major advance in our exploration of nature, bringing us closer to understanding how the fundamental particles acquire their mass, and marking the beginning of a new chapter in particle physics."

CERN SUSY: Higgs-Boson result means elegant universe is back on agenda

After a short spell on the rocks, a mathematically elegant view of the universe is back in vogue. 

Recent hints of the Higgs boson at the Large Hadron Collider help explain why we have not seen evidence for the beautiful theory of supersymmetry yet - and point to fresh ways to focus the search.

Supersymmetry, or SUSY, is an extension to the standard model of how particles and forces interact. Via elegant equations, it posits that every fundamental particle - including quarks, electrons, photons and neutrinos - has a heavier, as yet unseen "superpartner" with slightly different properties (see diagram). 

This smooths some embarrassing wrinkles in the standard model. However, not one superpartner has yet shown up at the LHC, the particle smasher at CERN near Geneva, Switzerland, prompting fears that, despite its beauty, SUSY could be wrong.

That changed on 13 December, when LHC physicists reported that they might have found traces of the Higgs boson, the standard-model particle that is thought to give all others mass. The data suggested a mass for the Higgs close to 125 gigaelectronvolts, 133 times that of the proton and too light for a Higgs to survive without a heavier companion particle, which could be a superpartner.

"This is very good news for people who believe in supersymmetry," says Howard Baer of the University of Oklahoma in Norman. 

He's one of several researchers who have calculated what the suspected Higgs mass could mean for SUSY particle, or sparticle, detections at the LHC.

Baer reckons it can explain why sparticles have not yet been seen. Particles get their masses by interacting with the Higgs field; the stronger the interaction, the heavier the particle.

So if the Higgs is confirmed at 125 GeV, which is heavy for SUSY models, many superpartners must be on the heavy side too. 

Baer and colleagues calculated that in several different versions of SUSY, a 125-GeV Higgs means squarks (the SUSY version of quarks) and sleptons (SUSY versions of electrons and neutrinos) must weigh 10,000 GeV or more, far too heavy for the LHC's detectors to find (arxiv.org/abs/1112.3017).

"Even last summer, people thought that squarks might be quite light and around the corner," Baer says. 

"This makes it look like the LHC will have a little bit more difficulty trying to pull out a SUSY signal."

That's not to say the LHC won't find any sparticles, though.

Given the new estimated mass of the Higgs, Baer calculates that the gluino - superpartner to the gluon, which carries the force that holds atomic nuclei together - could be as light as 500 to 1000 GeV.

The LHC is already probing this range, albeit not for gluinos specifically. Light gluinos won't be detected directly, but by the particles they decay into.

Another possible super-quarry is the stop, the superpartner of the top quark. In some models of supersymmetry, there are two stops, one monstrously heavy and another relatively light. 

According to Marcela Carena at Fermilab in Batavia, Illinois, and colleagues, a 125-GeV Higgs could put the light stop between 100 and 130 GeV, easily visible at the LHC (arxiv.org/abs/1112.3336).

Of course, all this assumes that the Higgs signals recur in further experiments. Right now, they do not have the statistical significance to count as a discovery. "I very much hope that what we have seen so far finally ends up being the real Higgs," says Carena.

'Supersymmetry' Could Be The Next Next Big Thing In Physics

Physicists said the next big thing in the world of particle physics will be the extension of the standard model of particle physics known as supersymmetry or SUSY.

According to a team of researchers, the better understanding of the universe will lead to the outgrowth of the discovery of the Higgs boson, and will lead to the discovery of its extension, the SUSY.

University of Oklahoma researchers said SUSY predict new matter states or super partners for each matter particle already accounted for in the standard model.

Physicists Howard Baer, Homer L. Dodge Professor of High Energy Physics in the OU Department of Physics and Astronomy, and his colleagues were the first in the world to show what SUSY matter might look like at colliding beam experiments.

Earlier reports said the Large Hadron Collider has not been successful so far in finding SUSY, while Atlas and CMS experiments is expected to provide new analysis on SUSY in March 2012.

The LHC will reportedly double the energy required to prove the SUSY theory.

Baer, who has studied SUSY for 25 years, said the discovery of the Higgs boson will open the door to a whole new world of super particles. "Finding the Higgs boson is like looking for a needle in a haystack, but the Higgs boson is only the tip of the iceberg of SUSY matter," Baer said.

"With SUSY, we are talking about the next level of the laws of physics. If there is SUSY, then we will find super partners, which will provide a new perspective for the origin and evolution of the universe. At that point, we can say we are on the road to a much deeper comprehension of nature, " Baer added.

The researchers said SUSY may be the next big step in understanding cosmology and the origin of dark matter, the so-called invisible particles that dominate the matter density of the universe