16-11-2009

For more than 20 years, solid niobium has had the monopoly on high-gradient applications of superconducting radio frequency (SRF) cavities for particle accelerators. But it will soon have reached its limits. It was only recently that A. Gurevich, a theoretician from Florida State University, put forward a theory explaining the reasons behind niobium's success and a way of breaking its monopoly. Until now, this theoretical model had never been experimentally demonstrated. This has now changed for a collaborative project between IRFU (Saclay) and INAC (Grenoble) has just made this vital step towards new acceleration technology.

16-11-2009

 

Work on a new clean room, begun in July 2007 at the Saclay accelerator platform, has just been completed. The new clean room will be officially opened on 24 November 2009 and will replace the chemical facilities and clean room of IRFU's Accelerators, Cryogenics and Magnetism Division (SACM) located at L'Orme, which could no longer undergo all the improvements required to keep pace with current development work. A hall in building 124 (previously the Saturne laboratory) has therefore been renovated to accommodate the future facilities and equipment compatible with future accelerator research requirements and collaborative projects with industrial partners interested in the control of superconducting cavity systems.

30-09-2009

The last coil of the Wendelstein W7X stellarator left CEA-Saclay last week, on Wednesday 9 September 2009 to be precise. The event marks the end of trials on the 70 coils of this fusion reactor and seals the success of a major project that began in 1998 and involved many teams from IRFU (formerly known as DAPNIA). The 70th coil has just been tested and validated at the W7x test station and has now gone to join the other 69 members of the family of superconducting coils currently being assembled on the Wendelstein 7-X stellarator, the research machine for the European programme on magnetic confinement thermonuclear fusion.

 

The tests, performed under a French-German collaboration agreement with the Max Planck Institute-IPP Greifswald, gave scientists from many countries an opportunity to work together and highlighted the CEA's major contribution to the fusion programme. So many thanks to all those who helped to make this project a success.

14-09-2009

 

 

Engineers and physicists from IRFU have successfully assembled and commissioned three large chambers designed to reconstruct charged particle tracks. The chambers will characterize the neutrino beam used in the T2K (Tokai to Kamiokande) experiment. They are the first large Time Projection Chambers (TPCs) to be equipped with micromesh gas detectors (Micromegas). The chambers have a very large sensitive area (nearly 9m²) and a correspondingly high number of electronic channels (124,000). IRFU built the entire detection system of the three TPCs, comprising 72 Micromegas detectors and all the front-end electronics. Engineers from SEDI, a department specialised in detector, electronics and information technology, specially designed a new chip called AFTER and two printed circuit boards for sending digitised signals to the acquisition system via an array of 72 gigabit optical links. The three chambers were tested with a particle beam at TRIUMF in Canada and have been installed in JPARC (Tokai, Japan) at the end of 2009.


The first beam and cosmic ray tests demonstrated that tracks could be reconstructed with the required degree of precision. This achievement represents a major step forward in the construction of a vital detector for the T2K experiment.

 

The TPC are now detecting tracks produced by neutrino interaction in the near detector of T2K and provide superior information to measure the momentum and to identify these particles. 


 

Contacts:

 

Alain DELBART

Marco ZITO

27-12-2009

Since the restart of the LHC on 20 November, CMS has taken advantage of the excellent operating performance of the collider to record a large amount of useful data. This is now being used to check its correct operation and calibration. During this period, CMS has demonstrated the stability of the detectors' working conditions as well as the efficiency of the data analysis system, which sends data from the detector to analysis teams around the world, and this in spite of very rapidly changing beam conditions.

 

23-12-2009

Monday, 23 November 2009, marked the first particle beam collision inside the large detectors of the LHC. ALICE saw its first collisions at an energy of 900 GeV, enabling it to check for correct operation of the 18 large detectors which comprise it. Since 27 November, with just a few days worth of data, the collaboration has even published an article confirming some existing measurements.

The group from the IRFU, who are responsible for the dimuon arms, had to await more stable beam conditions in order to see their detectors reacting to the data coming from the collisions and, on 6 December, all the gaseous detectors were able to be powered up. The traces from the first muons could be successfully reconstructed, to the great satisfaction to all the team. They are now eager to begin collecting more data after the planned restart in February 2010.

23-12-2009

Since the accident which occurred on the LHC accelerator several days after its commissioning in 2008, the ATLAS collaboration has been impatient to observe "true" events produced at the centre of the detector, and to make the equipment function under real conditions. On 23 November, following several days of tests with a single beam, Atlas recorded its first proton-proton collisions, at the injection energy into the LHC (450 GeV per beam, i.e. 900 GeV in the centre of mass reference frame of the collision). Analysis has then been able to reconstruct known unstable particles by detecting their disintegration products, demonstrating that the detectors and associated software are functioning correctly. The Atlas group, from the Particle Physics Department at IRFU, has also been able to check the behaviour of the muon detector sub-systems and the electromagnetic calorimetry, for which it is responsible. Collisions at 2.38 TeV (1.19 TeV per beam) were recorded before the LHC shutdown on 16 December, establishing a new world-record as of the most powerful particle accelerator in the world. The LHC will start up again in February 2010 after a short technical break aiming to produce collisions with higher energies and at higher intensity. Dark matter may be made of new particles, which could be produced in the high-energy proton-proton collisions at LHC. In this case Atlas would be able to discover them.

14-12-2009
Microquaser gamma emission observed for the first time

For the first time, the high-energy gamma rays emitted by a microquasar have been spotted with certainty, thanks to NASA's Fermi telescope. The observation of the microquasar Cygnus X-3 by a French team (CEA-IRFU, CNRS-INSU and IN2P3, University of Paris Diderot, Joseph Fourier University) teaches us more about how these particular sources function and how a compact object orbiting a star can hurl a mass equivalent to the Moon's through the interstellar medium at almost the speed of light. The study is published in Science Express on 26 November 2009.

 

- for more information : see the French version

11-12-2009
Edelweiss-ID: innovative detectors for tracking dark matter in the Milky Way

 

The new generation of detectors from the Edelweiss experiment, which is searching for dark matter, have just delivered their first results.  Remarkably reliable and robust, they have proved excellent at removing interference signals. Although only just installed and not yet perfected, these new detectors have improved the experiment's sensitivity by a factor of 10 in terms of its capacity to measure an interaction with a "wimp"1 , a weakly interacting massive particle, which is one of the candidates for dark matter. 

 

  

 

 

 Article submitted to Phys Lett. B (online)

  

 

 

In 2010 the usable mass of detectors will be tripled in order to improve their discovery potential still further.

 

 

  

 

This jump in sensitivity puts this experiment in amongst the leading group of experiments worldwide that are seeking to detect these new particles. These first results have just been submitted for publication in the journal Physics Letters B

26-11-2009
Do quasars give birth to galaxies?

Which came first - the black hole or the galaxy? Many large galaxies in the Universe have a supermassive black hole at their centre. But which came first? The black hole that is frantically consuming the matter around it or the vast galaxy that is its home?

A European team led by David Elbaz from CEA-IRFU's  Astrophysics Department has just discovered a spectacular interaction between a quasar and a galaxy from observations made with the VISIR camera. The camera was built at CEA-IRFU and installed on the European Southern Observatory's (ESO) Very Large Telescope in Chile. A jet from the quasar is responsible for star formation on a large scale in the galaxy (see animated view). From these observations, a new scenario seems to be emerging: black holes might "build" the galaxy that will become their home. This surprising discovery is published in the journal Astronomy & Astrophysics on 30 November 2009.

16-11-2009

 

Work on a new clean room, begun in July 2007 at the Saclay accelerator platform, has just been completed. The new clean room will be officially opened on 24 November 2009 and will replace the chemical facilities and clean room of IRFU's Accelerators, Cryogenics and Magnetism Division (SACM) located at L'Orme, which could no longer undergo all the improvements required to keep pace with current development work. A hall in building 124 (previously the Saturne laboratory) has therefore been renovated to accommodate the future facilities and equipment compatible with future accelerator research requirements and collaborative projects with industrial partners interested in the control of superconducting cavity systems.

16-11-2009

For more than 20 years, solid niobium has had the monopoly on high-gradient applications of superconducting radio frequency (SRF) cavities for particle accelerators. But it will soon have reached its limits. It was only recently that A. Gurevich, a theoretician from Florida State University, put forward a theory explaining the reasons behind niobium's success and a way of breaking its monopoly. Until now, this theoretical model had never been experimentally demonstrated. This has now changed for a collaborative project between IRFU (Saclay) and INAC (Grenoble) has just made this vital step towards new acceleration technology.

10-10-2009

The Baryon Oscillation Spectroscopic Survey - known as Boss - delivered its first data during the night of 14-15 September. This experiment, devoted to the search for baryon oscillations, heralds the start of a new era of research into dark energy and the evolution of the Universe. Several teams are involved in BOSS, in particular from IN2P3(1)/CNRS, INSU(2)/CNRS and CEA.

30-09-2009

The last coil of the Wendelstein W7X stellarator left CEA-Saclay last week, on Wednesday 9 September 2009 to be precise. The event marks the end of trials on the 70 coils of this fusion reactor and seals the success of a major project that began in 1998 and involved many teams from IRFU (formerly known as DAPNIA). The 70th coil has just been tested and validated at the W7x test station and has now gone to join the other 69 members of the family of superconducting coils currently being assembled on the Wendelstein 7-X stellarator, the research machine for the European programme on magnetic confinement thermonuclear fusion.

 

The tests, performed under a French-German collaboration agreement with the Max Planck Institute-IPP Greifswald, gave scientists from many countries an opportunity to work together and highlighted the CEA's major contribution to the fusion programme. So many thanks to all those who helped to make this project a success.

14-09-2009

 

 

Engineers and physicists from IRFU have successfully assembled and commissioned three large chambers designed to reconstruct charged particle tracks. The chambers will characterize the neutrino beam used in the T2K (Tokai to Kamiokande) experiment. They are the first large Time Projection Chambers (TPCs) to be equipped with micromesh gas detectors (Micromegas). The chambers have a very large sensitive area (nearly 9m²) and a correspondingly high number of electronic channels (124,000). IRFU built the entire detection system of the three TPCs, comprising 72 Micromegas detectors and all the front-end electronics. Engineers from SEDI, a department specialised in detector, electronics and information technology, specially designed a new chip called AFTER and two printed circuit boards for sending digitised signals to the acquisition system via an array of 72 gigabit optical links. The three chambers were tested with a particle beam at TRIUMF in Canada and have been installed in JPARC (Tokai, Japan) at the end of 2009.


The first beam and cosmic ray tests demonstrated that tracks could be reconstructed with the required degree of precision. This achievement represents a major step forward in the construction of a vital detector for the T2K experiment.

 

The TPC are now detecting tracks produced by neutrino interaction in the near detector of T2K and provide superior information to measure the momentum and to identify these particles. 


 

Contacts:

 

Alain DELBART

Marco ZITO

18-06-2009
A precious Chinese document brought back to light from the legendary Silk road

A spectacular document relating to the history of astronomy is brought back to light by a recent study from a group of scholars led by Jean-Marc Bonnet-Bidaud from the CEA Astrophysical Department [1]. The document, called the Dunhuang chart, now kept at the British Library in London, is a complete star atlas which was found among the 40 000 other manuscripts discovered  at the Buddhist Mogao cave complex, on the Chinese Silk road in 1900. Sealed in an hidden cave around the 11th century, these manuscripts, mostly religious Buddhist texts, were miraculously preserved thanks to a dry climate.
The first detailed scientific analysis of the star chart performed by these scientists reveals that it contains more than 1300 stars and was composed around the years +(649-684). Using precise mathematical projection methods, it preserves a remarkable  accuracy of 1.5 to 4° for the brightest stars. It is the oldest known star chart from any civilisation and the first pictorial representation of the classical Chinese constellations.
The chart is presented in the June 11th issue of the Nature magazine and the detailed historical and scientific study is reported in the Journal of Astronomical History and Heritage. The chart is also exceptionally on display at the British Library till 18 August 2009 to celebrate the International Year of Astronomy.

drapeau version française   drapeau english version  
05-06-2009

An IRAMIS team is fitting out a basement area for the purposes of a scientific programme to study laser electron acceleration. Electrons will be generated by the interaction of a laser beam with a helium gas jet. The team called on SENAC, an IRFU department concerned with decommissioning, clean-up and declassification of nuclear facilities, to conduct a biological shielding study with a view to limiting the impact of radiation in the vicinity of the experiment room while the laser is in operation. The study, which lasted two months, pinpointed radiation protection problems caused by the interaction of the laser electron beam with various items of equipment in the new experiment room. The aim was to find suitable solutions to permit the group to use its high-power laser, with the support of SPR, in full compliance with applicable radiation protection regulations concerning personnel.

  

The study was conducted under a new mutual assistance agreement between SPAM and SENAC for high-power laser projects.

 

 

02-06-2009

The second phase of the Double Chooz international experiment officially began on Wednesday 20 May. The Declaration of Intent signed by the four partners (CEA, CNRS, EDF, Champagne-Ardenne Region) is the first step in the plan to build a second detector devoted to neutrino research next to the Chooz nuclear power plant.

Prior to signing the DOI, the participants visited the site of the first detector, currently under construction. By the end of the year, the detector should pick up the first neutrinos emitted by the plant and attempt to measure the disappearance of primary flux neutrinos. The second detector, which will be operational two years from now, will provide precise measurements of the flux and spectrum of the neutrinos emitted and greatly enhance measurement control and precision.

 

 

 

 

Contact

 

Thierry LASSERRE

02-06-2009
A research team has just published the most precise measurement ever of the rate of gravitational collapse supernovae observed in the Universe 3.7 billion years ago

 

The Supernova Legacy Survey (SNLS) team at the Canada-France-Hawaii Telescope facility has just obtained the world's best measurement of the explosion rate of massive stars when the Universe was only 10 billion years old. A research team at IRFU's particle physics department at the CEA-Saclay centre worked on the first three years of SNLS data to obtain this result, which makes a crucial contribution to our understanding of the origins and evolution of chemical elements in the interstellar medium. The measurement seems to show that there are two to four times fewer supernovae today than 3.7 billion years ago. Could the Universe be burning out?

 

 

 

Contacts:

 

 

Nathalie PALANQUE-DELABROUILLE

James RICH

Vanina RUHLMAN-KLEIDER

 

05-05-2009

At the end of March 2009, the ALICE Muon Spectrometer took cosmic rays over a period of two weeks. The ALICE group at Saclay2 was closely involved in the design, development, construction and installation of a part of the chambers of this Spectrometer3. The purpose of the cosmic ray test was to check the performance of the entire system, from acquisition to reconstruction of the data. The acquisition system readout about a million channels and the data was recorded on the computing grid. Almost 15,000 tracks were reconstructed under conditions close to those of the real experiment. The cosmic test was a success, demonstrating the performance and the stability of the spectrometer chambers. It also revealed some weak points of the system. Tests are currently underway to correct the observed defaults.

Another cosmic test is planned for August, a few weeks before the first LHC beam injections, involving all ALICE detectors.

 

 

Contacts:

Alberto BALDISSERI

Hervé BOREL

22-04-2009

Since researchers have been confronting the standard model of particle physics with experimentation, nothing has been able to shake it. Of all particles it describes, only the Higgs Boson has not yet been discovered. But the standard model is probably not the ultimate theory: it does not cover gravitation and numerous experimental observations remain unexplained.

A new invariance, called supersymmetry, was suggested during the 1970s. It associates particles with different spins (integer spin bosons and half-integer spin fermions). It is possible to create supersymmetric extensions of the standard model, elegantly resolving the mathematical problems that emerge during calculation of the Higgs Boson mass.

 

D01 experiment accumulating data from Fermilab's Tevatron (United States) just published2 results relating to the Higgs Boson research needed for supersymmetric extensions to the standard model. All currently available data has been analysed, representing more than one and a half billion events.

 

Finding a supersymmetric light Higgs 

In the Tevatron, a high-energy proton-antiproton collider, large quantities of Higgs Bosons could be produced if they are sufficiently light. A useful channel for detecting them is their production associated with a bottom quark3 (b), H0b. In 90% of cases, supersymmetric light Higgs Bosons are supposed to disintegrate into two bottom quarks. That is why research in this area is based on identifying those events involving at least three jets4 resulting from bottom quarks in the final state.

 

 

 

21-04-2009

It has now been more than two years that Antares1, the underwater telescope installed in the depths of the abyssal plains 2500 m under the Mediterranean, is scanning the skies through the Earth in search of neutrinos. Over a thousand of them have already been observed until today, making it possible to establish the first views of the heavens to search for high-energy cosmic neutrinos, particles that may be able to teach us more about the most violent phenomena in the Universe.

 

 

Neutrinos are particles that interact very little with matter. Emitted by the most violent cataclysms of the Universe, they could prove that these phenomena are responsible for cosmic rays, mainly protons, which are constantly bombarding the Earth. These protons actually reach us after having been diverted from their paths by intergalactic magnetic fields, which prevents us from identifying their origin.

 

Their very weak interaction with matter makes neutrinos hard to detect. This problem can only be overcome by using enormous detectors, shielded against the cosmic rays. Antares, installed off the coast of Toulon, is protected against this radiation by a natural shield - 2000 m of water. Work on the detector took two years and its deployment was achieved in May 2008. Today 885 "eyes", together with the electronic equipment designed and built by CEA-IRFU (Institute of Research into the Fundamental Laws of the Universe) to read and process the data, are strung out in groups of threes along 12 flexible lines 450 m high. These lines are higher than the Eiffel Tower and are anchored to the seabed covering an area as large as four football fields.

06-04-2009

 

 

Until the advent of the LHC, the Tevatron at the Fermi National Accelerator Laboratory, Fermilab (close to Chicago, USA), will remain the world's most powerful collider and the only location where the top1 quark can be produced.

The DØ experiment recently published2 results on the measurement of the rate of production of top-antitop quark pairs. This quantity, which is dependent on the value taken for the mass of the top quark, enables a prediction to be made for that mass using the standard model3. The top quark, which was discovered at Fermilab in 1995, remains the subject of very active research. Methods of analysis and the quantity of data are forever improving, which is resulting in subsequent improvements in the accuracy of the measurement of the top quark mass.  The precise measurement of this value, combined with results from other precision measurements, enables the most probable mass of the Higgs Boson to be estimated. Hence improved measurements of the mass of the top quark is tightening the vice in the search for the Higgs boson.

 

07-03-2009

The Nobel Prize for Physics 2008 rewarded Makoto Kobayashi and Toshihide Maskawa for having realised that the weak interaction does not affect particles and antiparticles in the same way1. In this theory, it was expected that the strong interaction would exhibit the same type of asymmetry between quarks and antiquarks.

However the asymmetry is not there! A problem! To explain this anomaly of the strong interaction, theoreticians have postulated the existence of a new particle known as the "axion", named after a detergent because it will help to clean up the problem. Expected to be both neutral and light, this particle will be analogous to a photon, with which it could be coupled. On the other hand it will only interact slightly with matter, so slightly that, to date, it has never been observed.

CAST2 is an experiment designed to detect this hypothetical particle which may be produced abundantly by the sun. The collaboration recently published their results ("Journal of Cosmology and Astroparticle Physics") which have enabled the limits of the predicted mass of the axion to be reduced. 

The search for axions continues, thanks to improvement in the performance of the CAST Micromegas detectors, enabling the level of noise to be reduced to an extremely low level, in the  low energy regime between 1 and 10 keV, and so to further reduce the lower limit for detection of these hypothetical particles.


 

 

Why are we interested in axions?

 

 

 

Axions are particles which were introduced by theoreticians to explain the apparent symmetry between matter and antimatter in the strong interaction. These axions, neutral and of very low mass, are also candidates to make up the dark matter in our universe. Theoretical models and astrophysical observations limit the mass of the axion to being in the range between several µeV/c2 and several eV/c2.

The absence of observation of axions in the CAST experiment has enabled an experimental upper limit to be established for the axion-photon coupling constant, for masses less than 0.4 eV/c2 (figure 1). For the first time this limit has reached the yellow band favoured by the theoretical models.  

 

 

 

18-02-2009
The FERMI observatory has discovered the most energetic gamma-ray burst ever detected

The Fermi gamma-ray space telescope  [1] has detected the most violent gamma-ray burst ever recorded; a gigantic explosion marking the death of a massive star. Light from this explosion, captured by the Fermi observatory on September 16th 2008, had taken 12.2 billion years to reach Earth. Hence, it must have been produced at a time when the Universe was just 1.5 billion years old.  The total amount of energy released makes this the most violent explosion observed in the Universe since the Big Bang. Observed by the Fermi on scales covering more than six decades in energy, this gamma-ray burst demonstrated exceptional properties. Clouds of charged particles were catapulted out during the explosion, at a speed equal to 99.9% of the speed of light! This work, the result of the international Fermi collaboration, with partners from CEA-Irfu, was published on February 19th 2009 in the journal Science express.

18-06-2009
A precious Chinese document brought back to light from the legendary Silk road

A spectacular document relating to the history of astronomy is brought back to light by a recent study from a group of scholars led by Jean-Marc Bonnet-Bidaud from the CEA Astrophysical Department [1]. The document, called the Dunhuang chart, now kept at the British Library in London, is a complete star atlas which was found among the 40 000 other manuscripts discovered  at the Buddhist Mogao cave complex, on the Chinese Silk road in 1900. Sealed in an hidden cave around the 11th century, these manuscripts, mostly religious Buddhist texts, were miraculously preserved thanks to a dry climate.
The first detailed scientific analysis of the star chart performed by these scientists reveals that it contains more than 1300 stars and was composed around the years +(649-684). Using precise mathematical projection methods, it preserves a remarkable  accuracy of 1.5 to 4° for the brightest stars. It is the oldest known star chart from any civilisation and the first pictorial representation of the classical Chinese constellations.
The chart is presented in the June 11th issue of the Nature magazine and the detailed historical and scientific study is reported in the Journal of Astronomical History and Heritage. The chart is also exceptionally on display at the British Library till 18 August 2009 to celebrate the International Year of Astronomy.

drapeau version française   drapeau english version  
18-02-2009
The FERMI observatory has discovered the most energetic gamma-ray burst ever detected

The Fermi gamma-ray space telescope  [1] has detected the most violent gamma-ray burst ever recorded; a gigantic explosion marking the death of a massive star. Light from this explosion, captured by the Fermi observatory on September 16th 2008, had taken 12.2 billion years to reach Earth. Hence, it must have been produced at a time when the Universe was just 1.5 billion years old.  The total amount of energy released makes this the most violent explosion observed in the Universe since the Big Bang. Observed by the Fermi on scales covering more than six decades in energy, this gamma-ray burst demonstrated exceptional properties. Clouds of charged particles were catapulted out during the explosion, at a speed equal to 99.9% of the speed of light! This work, the result of the international Fermi collaboration, with partners from CEA-Irfu, was published on February 19th 2009 in the journal Science express.

11-12-2009
Edelweiss-ID: innovative detectors for tracking dark matter in the Milky Way

 

The new generation of detectors from the Edelweiss experiment, which is searching for dark matter, have just delivered their first results.  Remarkably reliable and robust, they have proved excellent at removing interference signals. Although only just installed and not yet perfected, these new detectors have improved the experiment's sensitivity by a factor of 10 in terms of its capacity to measure an interaction with a "wimp"1 , a weakly interacting massive particle, which is one of the candidates for dark matter. 

 

  

 

 

 Article submitted to Phys Lett. B (online)

  

 

 

In 2010 the usable mass of detectors will be tripled in order to improve their discovery potential still further.

 

 

  

 

This jump in sensitivity puts this experiment in amongst the leading group of experiments worldwide that are seeking to detect these new particles. These first results have just been submitted for publication in the journal Physics Letters B

14-09-2009

 

 

Engineers and physicists from IRFU have successfully assembled and commissioned three large chambers designed to reconstruct charged particle tracks. The chambers will characterize the neutrino beam used in the T2K (Tokai to Kamiokande) experiment. They are the first large Time Projection Chambers (TPCs) to be equipped with micromesh gas detectors (Micromegas). The chambers have a very large sensitive area (nearly 9m²) and a correspondingly high number of electronic channels (124,000). IRFU built the entire detection system of the three TPCs, comprising 72 Micromegas detectors and all the front-end electronics. Engineers from SEDI, a department specialised in detector, electronics and information technology, specially designed a new chip called AFTER and two printed circuit boards for sending digitised signals to the acquisition system via an array of 72 gigabit optical links. The three chambers were tested with a particle beam at TRIUMF in Canada and have been installed in JPARC (Tokai, Japan) at the end of 2009.


The first beam and cosmic ray tests demonstrated that tracks could be reconstructed with the required degree of precision. This achievement represents a major step forward in the construction of a vital detector for the T2K experiment.

 

The TPC are now detecting tracks produced by neutrino interaction in the near detector of T2K and provide superior information to measure the momentum and to identify these particles. 


 

Contacts:

 

Alain DELBART

Marco ZITO

02-06-2009

The second phase of the Double Chooz international experiment officially began on Wednesday 20 May. The Declaration of Intent signed by the four partners (CEA, CNRS, EDF, Champagne-Ardenne Region) is the first step in the plan to build a second detector devoted to neutrino research next to the Chooz nuclear power plant.

Prior to signing the DOI, the participants visited the site of the first detector, currently under construction. By the end of the year, the detector should pick up the first neutrinos emitted by the plant and attempt to measure the disappearance of primary flux neutrinos. The second detector, which will be operational two years from now, will provide precise measurements of the flux and spectrum of the neutrinos emitted and greatly enhance measurement control and precision.

 

 

 

 

Contact

 

Thierry LASSERRE

02-06-2009
A research team has just published the most precise measurement ever of the rate of gravitational collapse supernovae observed in the Universe 3.7 billion years ago

 

The Supernova Legacy Survey (SNLS) team at the Canada-France-Hawaii Telescope facility has just obtained the world's best measurement of the explosion rate of massive stars when the Universe was only 10 billion years old. A research team at IRFU's particle physics department at the CEA-Saclay centre worked on the first three years of SNLS data to obtain this result, which makes a crucial contribution to our understanding of the origins and evolution of chemical elements in the interstellar medium. The measurement seems to show that there are two to four times fewer supernovae today than 3.7 billion years ago. Could the Universe be burning out?

 

 

 

Contacts:

 

 

Nathalie PALANQUE-DELABROUILLE

James RICH

Vanina RUHLMAN-KLEIDER

 

05-05-2009

At the end of March 2009, the ALICE Muon Spectrometer took cosmic rays over a period of two weeks. The ALICE group at Saclay2 was closely involved in the design, development, construction and installation of a part of the chambers of this Spectrometer3. The purpose of the cosmic ray test was to check the performance of the entire system, from acquisition to reconstruction of the data. The acquisition system readout about a million channels and the data was recorded on the computing grid. Almost 15,000 tracks were reconstructed under conditions close to those of the real experiment. The cosmic test was a success, demonstrating the performance and the stability of the spectrometer chambers. It also revealed some weak points of the system. Tests are currently underway to correct the observed defaults.

Another cosmic test is planned for August, a few weeks before the first LHC beam injections, involving all ALICE detectors.

 

 

Contacts:

Alberto BALDISSERI

Hervé BOREL

22-04-2009

Since researchers have been confronting the standard model of particle physics with experimentation, nothing has been able to shake it. Of all particles it describes, only the Higgs Boson has not yet been discovered. But the standard model is probably not the ultimate theory: it does not cover gravitation and numerous experimental observations remain unexplained.

A new invariance, called supersymmetry, was suggested during the 1970s. It associates particles with different spins (integer spin bosons and half-integer spin fermions). It is possible to create supersymmetric extensions of the standard model, elegantly resolving the mathematical problems that emerge during calculation of the Higgs Boson mass.

 

D01 experiment accumulating data from Fermilab's Tevatron (United States) just published2 results relating to the Higgs Boson research needed for supersymmetric extensions to the standard model. All currently available data has been analysed, representing more than one and a half billion events.

 

Finding a supersymmetric light Higgs 

In the Tevatron, a high-energy proton-antiproton collider, large quantities of Higgs Bosons could be produced if they are sufficiently light. A useful channel for detecting them is their production associated with a bottom quark3 (b), H0b. In 90% of cases, supersymmetric light Higgs Bosons are supposed to disintegrate into two bottom quarks. That is why research in this area is based on identifying those events involving at least three jets4 resulting from bottom quarks in the final state.

 

 

 

21-04-2009

It has now been more than two years that Antares1, the underwater telescope installed in the depths of the abyssal plains 2500 m under the Mediterranean, is scanning the skies through the Earth in search of neutrinos. Over a thousand of them have already been observed until today, making it possible to establish the first views of the heavens to search for high-energy cosmic neutrinos, particles that may be able to teach us more about the most violent phenomena in the Universe.

 

 

Neutrinos are particles that interact very little with matter. Emitted by the most violent cataclysms of the Universe, they could prove that these phenomena are responsible for cosmic rays, mainly protons, which are constantly bombarding the Earth. These protons actually reach us after having been diverted from their paths by intergalactic magnetic fields, which prevents us from identifying their origin.

 

Their very weak interaction with matter makes neutrinos hard to detect. This problem can only be overcome by using enormous detectors, shielded against the cosmic rays. Antares, installed off the coast of Toulon, is protected against this radiation by a natural shield - 2000 m of water. Work on the detector took two years and its deployment was achieved in May 2008. Today 885 "eyes", together with the electronic equipment designed and built by CEA-IRFU (Institute of Research into the Fundamental Laws of the Universe) to read and process the data, are strung out in groups of threes along 12 flexible lines 450 m high. These lines are higher than the Eiffel Tower and are anchored to the seabed covering an area as large as four football fields.

06-04-2009

 

 

Until the advent of the LHC, the Tevatron at the Fermi National Accelerator Laboratory, Fermilab (close to Chicago, USA), will remain the world's most powerful collider and the only location where the top1 quark can be produced.

The DØ experiment recently published2 results on the measurement of the rate of production of top-antitop quark pairs. This quantity, which is dependent on the value taken for the mass of the top quark, enables a prediction to be made for that mass using the standard model3. The top quark, which was discovered at Fermilab in 1995, remains the subject of very active research. Methods of analysis and the quantity of data are forever improving, which is resulting in subsequent improvements in the accuracy of the measurement of the top quark mass.  The precise measurement of this value, combined with results from other precision measurements, enables the most probable mass of the Higgs Boson to be estimated. Hence improved measurements of the mass of the top quark is tightening the vice in the search for the Higgs boson.

 

07-03-2009

The Nobel Prize for Physics 2008 rewarded Makoto Kobayashi and Toshihide Maskawa for having realised that the weak interaction does not affect particles and antiparticles in the same way1. In this theory, it was expected that the strong interaction would exhibit the same type of asymmetry between quarks and antiquarks.

However the asymmetry is not there! A problem! To explain this anomaly of the strong interaction, theoreticians have postulated the existence of a new particle known as the "axion", named after a detergent because it will help to clean up the problem. Expected to be both neutral and light, this particle will be analogous to a photon, with which it could be coupled. On the other hand it will only interact slightly with matter, so slightly that, to date, it has never been observed.

CAST2 is an experiment designed to detect this hypothetical particle which may be produced abundantly by the sun. The collaboration recently published their results ("Journal of Cosmology and Astroparticle Physics") which have enabled the limits of the predicted mass of the axion to be reduced. 

The search for axions continues, thanks to improvement in the performance of the CAST Micromegas detectors, enabling the level of noise to be reduced to an extremely low level, in the  low energy regime between 1 and 10 keV, and so to further reduce the lower limit for detection of these hypothetical particles.


 

 

Why are we interested in axions?

 

 

 

Axions are particles which were introduced by theoreticians to explain the apparent symmetry between matter and antimatter in the strong interaction. These axions, neutral and of very low mass, are also candidates to make up the dark matter in our universe. Theoretical models and astrophysical observations limit the mass of the axion to being in the range between several µeV/c2 and several eV/c2.

The absence of observation of axions in the CAST experiment has enabled an experimental upper limit to be established for the axion-photon coupling constant, for masses less than 0.4 eV/c2 (figure 1). For the first time this limit has reached the yellow band favoured by the theoretical models.  

 

 

 

23-12-2009

Monday, 23 November 2009, marked the first particle beam collision inside the large detectors of the LHC. ALICE saw its first collisions at an energy of 900 GeV, enabling it to check for correct operation of the 18 large detectors which comprise it. Since 27 November, with just a few days worth of data, the collaboration has even published an article confirming some existing measurements.

The group from the IRFU, who are responsible for the dimuon arms, had to await more stable beam conditions in order to see their detectors reacting to the data coming from the collisions and, on 6 December, all the gaseous detectors were able to be powered up. The traces from the first muons could be successfully reconstructed, to the great satisfaction to all the team. They are now eager to begin collecting more data after the planned restart in February 2010.

27-12-2009

Since the restart of the LHC on 20 November, CMS has taken advantage of the excellent operating performance of the collider to record a large amount of useful data. This is now being used to check its correct operation and calibration. During this period, CMS has demonstrated the stability of the detectors' working conditions as well as the efficiency of the data analysis system, which sends data from the detector to analysis teams around the world, and this in spite of very rapidly changing beam conditions.

 

23-12-2009

Monday, 23 November 2009, marked the first particle beam collision inside the large detectors of the LHC. ALICE saw its first collisions at an energy of 900 GeV, enabling it to check for correct operation of the 18 large detectors which comprise it. Since 27 November, with just a few days worth of data, the collaboration has even published an article confirming some existing measurements.

The group from the IRFU, who are responsible for the dimuon arms, had to await more stable beam conditions in order to see their detectors reacting to the data coming from the collisions and, on 6 December, all the gaseous detectors were able to be powered up. The traces from the first muons could be successfully reconstructed, to the great satisfaction to all the team. They are now eager to begin collecting more data after the planned restart in February 2010.

23-12-2009

Since the accident which occurred on the LHC accelerator several days after its commissioning in 2008, the ATLAS collaboration has been impatient to observe "true" events produced at the centre of the detector, and to make the equipment function under real conditions. On 23 November, following several days of tests with a single beam, Atlas recorded its first proton-proton collisions, at the injection energy into the LHC (450 GeV per beam, i.e. 900 GeV in the centre of mass reference frame of the collision). Analysis has then been able to reconstruct known unstable particles by detecting their disintegration products, demonstrating that the detectors and associated software are functioning correctly. The Atlas group, from the Particle Physics Department at IRFU, has also been able to check the behaviour of the muon detector sub-systems and the electromagnetic calorimetry, for which it is responsible. Collisions at 2.38 TeV (1.19 TeV per beam) were recorded before the LHC shutdown on 16 December, establishing a new world-record as of the most powerful particle accelerator in the world. The LHC will start up again in February 2010 after a short technical break aiming to produce collisions with higher energies and at higher intensity. Dark matter may be made of new particles, which could be produced in the high-energy proton-proton collisions at LHC. In this case Atlas would be able to discover them.

11-12-2009
Edelweiss-ID: innovative detectors for tracking dark matter in the Milky Way

 

The new generation of detectors from the Edelweiss experiment, which is searching for dark matter, have just delivered their first results.  Remarkably reliable and robust, they have proved excellent at removing interference signals. Although only just installed and not yet perfected, these new detectors have improved the experiment's sensitivity by a factor of 10 in terms of its capacity to measure an interaction with a "wimp"1 , a weakly interacting massive particle, which is one of the candidates for dark matter. 

 

  

 

 

 Article submitted to Phys Lett. B (online)

  

 

 

In 2010 the usable mass of detectors will be tripled in order to improve their discovery potential still further.

 

 

  

 

This jump in sensitivity puts this experiment in amongst the leading group of experiments worldwide that are seeking to detect these new particles. These first results have just been submitted for publication in the journal Physics Letters B

10-10-2009

The Baryon Oscillation Spectroscopic Survey - known as Boss - delivered its first data during the night of 14-15 September. This experiment, devoted to the search for baryon oscillations, heralds the start of a new era of research into dark energy and the evolution of the Universe. Several teams are involved in BOSS, in particular from IN2P3(1)/CNRS, INSU(2)/CNRS and CEA.

30-09-2009

The last coil of the Wendelstein W7X stellarator left CEA-Saclay last week, on Wednesday 9 September 2009 to be precise. The event marks the end of trials on the 70 coils of this fusion reactor and seals the success of a major project that began in 1998 and involved many teams from IRFU (formerly known as DAPNIA). The 70th coil has just been tested and validated at the W7x test station and has now gone to join the other 69 members of the family of superconducting coils currently being assembled on the Wendelstein 7-X stellarator, the research machine for the European programme on magnetic confinement thermonuclear fusion.

 

The tests, performed under a French-German collaboration agreement with the Max Planck Institute-IPP Greifswald, gave scientists from many countries an opportunity to work together and highlighted the CEA's major contribution to the fusion programme. So many thanks to all those who helped to make this project a success.

14-09-2009

 

 

Engineers and physicists from IRFU have successfully assembled and commissioned three large chambers designed to reconstruct charged particle tracks. The chambers will characterize the neutrino beam used in the T2K (Tokai to Kamiokande) experiment. They are the first large Time Projection Chambers (TPCs) to be equipped with micromesh gas detectors (Micromegas). The chambers have a very large sensitive area (nearly 9m²) and a correspondingly high number of electronic channels (124,000). IRFU built the entire detection system of the three TPCs, comprising 72 Micromegas detectors and all the front-end electronics. Engineers from SEDI, a department specialised in detector, electronics and information technology, specially designed a new chip called AFTER and two printed circuit boards for sending digitised signals to the acquisition system via an array of 72 gigabit optical links. The three chambers were tested with a particle beam at TRIUMF in Canada and have been installed in JPARC (Tokai, Japan) at the end of 2009.


The first beam and cosmic ray tests demonstrated that tracks could be reconstructed with the required degree of precision. This achievement represents a major step forward in the construction of a vital detector for the T2K experiment.

 

The TPC are now detecting tracks produced by neutrino interaction in the near detector of T2K and provide superior information to measure the momentum and to identify these particles. 


 

Contacts:

 

Alain DELBART

Marco ZITO

02-06-2009

The second phase of the Double Chooz international experiment officially began on Wednesday 20 May. The Declaration of Intent signed by the four partners (CEA, CNRS, EDF, Champagne-Ardenne Region) is the first step in the plan to build a second detector devoted to neutrino research next to the Chooz nuclear power plant.

Prior to signing the DOI, the participants visited the site of the first detector, currently under construction. By the end of the year, the detector should pick up the first neutrinos emitted by the plant and attempt to measure the disappearance of primary flux neutrinos. The second detector, which will be operational two years from now, will provide precise measurements of the flux and spectrum of the neutrinos emitted and greatly enhance measurement control and precision.

 

 

 

 

Contact

 

Thierry LASSERRE

02-06-2009
A research team has just published the most precise measurement ever of the rate of gravitational collapse supernovae observed in the Universe 3.7 billion years ago

 

The Supernova Legacy Survey (SNLS) team at the Canada-France-Hawaii Telescope facility has just obtained the world's best measurement of the explosion rate of massive stars when the Universe was only 10 billion years old. A research team at IRFU's particle physics department at the CEA-Saclay centre worked on the first three years of SNLS data to obtain this result, which makes a crucial contribution to our understanding of the origins and evolution of chemical elements in the interstellar medium. The measurement seems to show that there are two to four times fewer supernovae today than 3.7 billion years ago. Could the Universe be burning out?

 

 

 

Contacts:

 

 

Nathalie PALANQUE-DELABROUILLE

James RICH

Vanina RUHLMAN-KLEIDER

 

05-05-2009

At the end of March 2009, the ALICE Muon Spectrometer took cosmic rays over a period of two weeks. The ALICE group at Saclay2 was closely involved in the design, development, construction and installation of a part of the chambers of this Spectrometer3. The purpose of the cosmic ray test was to check the performance of the entire system, from acquisition to reconstruction of the data. The acquisition system readout about a million channels and the data was recorded on the computing grid. Almost 15,000 tracks were reconstructed under conditions close to those of the real experiment. The cosmic test was a success, demonstrating the performance and the stability of the spectrometer chambers. It also revealed some weak points of the system. Tests are currently underway to correct the observed defaults.

Another cosmic test is planned for August, a few weeks before the first LHC beam injections, involving all ALICE detectors.

 

 

Contacts:

Alberto BALDISSERI

Hervé BOREL

22-04-2009

Since researchers have been confronting the standard model of particle physics with experimentation, nothing has been able to shake it. Of all particles it describes, only the Higgs Boson has not yet been discovered. But the standard model is probably not the ultimate theory: it does not cover gravitation and numerous experimental observations remain unexplained.

A new invariance, called supersymmetry, was suggested during the 1970s. It associates particles with different spins (integer spin bosons and half-integer spin fermions). It is possible to create supersymmetric extensions of the standard model, elegantly resolving the mathematical problems that emerge during calculation of the Higgs Boson mass.

 

D01 experiment accumulating data from Fermilab's Tevatron (United States) just published2 results relating to the Higgs Boson research needed for supersymmetric extensions to the standard model. All currently available data has been analysed, representing more than one and a half billion events.

 

Finding a supersymmetric light Higgs 

In the Tevatron, a high-energy proton-antiproton collider, large quantities of Higgs Bosons could be produced if they are sufficiently light. A useful channel for detecting them is their production associated with a bottom quark3 (b), H0b. In 90% of cases, supersymmetric light Higgs Bosons are supposed to disintegrate into two bottom quarks. That is why research in this area is based on identifying those events involving at least three jets4 resulting from bottom quarks in the final state.

 

 

 

21-04-2009

It has now been more than two years that Antares1, the underwater telescope installed in the depths of the abyssal plains 2500 m under the Mediterranean, is scanning the skies through the Earth in search of neutrinos. Over a thousand of them have already been observed until today, making it possible to establish the first views of the heavens to search for high-energy cosmic neutrinos, particles that may be able to teach us more about the most violent phenomena in the Universe.

 

 

Neutrinos are particles that interact very little with matter. Emitted by the most violent cataclysms of the Universe, they could prove that these phenomena are responsible for cosmic rays, mainly protons, which are constantly bombarding the Earth. These protons actually reach us after having been diverted from their paths by intergalactic magnetic fields, which prevents us from identifying their origin.

 

Their very weak interaction with matter makes neutrinos hard to detect. This problem can only be overcome by using enormous detectors, shielded against the cosmic rays. Antares, installed off the coast of Toulon, is protected against this radiation by a natural shield - 2000 m of water. Work on the detector took two years and its deployment was achieved in May 2008. Today 885 "eyes", together with the electronic equipment designed and built by CEA-IRFU (Institute of Research into the Fundamental Laws of the Universe) to read and process the data, are strung out in groups of threes along 12 flexible lines 450 m high. These lines are higher than the Eiffel Tower and are anchored to the seabed covering an area as large as four football fields.

06-04-2009

 

 

Until the advent of the LHC, the Tevatron at the Fermi National Accelerator Laboratory, Fermilab (close to Chicago, USA), will remain the world's most powerful collider and the only location where the top1 quark can be produced.

The DØ experiment recently published2 results on the measurement of the rate of production of top-antitop quark pairs. This quantity, which is dependent on the value taken for the mass of the top quark, enables a prediction to be made for that mass using the standard model3. The top quark, which was discovered at Fermilab in 1995, remains the subject of very active research. Methods of analysis and the quantity of data are forever improving, which is resulting in subsequent improvements in the accuracy of the measurement of the top quark mass.  The precise measurement of this value, combined with results from other precision measurements, enables the most probable mass of the Higgs Boson to be estimated. Hence improved measurements of the mass of the top quark is tightening the vice in the search for the Higgs boson.

 

14-09-2009

 

 

Engineers and physicists from IRFU have successfully assembled and commissioned three large chambers designed to reconstruct charged particle tracks. The chambers will characterize the neutrino beam used in the T2K (Tokai to Kamiokande) experiment. They are the first large Time Projection Chambers (TPCs) to be equipped with micromesh gas detectors (Micromegas). The chambers have a very large sensitive area (nearly 9m²) and a correspondingly high number of electronic channels (124,000). IRFU built the entire detection system of the three TPCs, comprising 72 Micromegas detectors and all the front-end electronics. Engineers from SEDI, a department specialised in detector, electronics and information technology, specially designed a new chip called AFTER and two printed circuit boards for sending digitised signals to the acquisition system via an array of 72 gigabit optical links. The three chambers were tested with a particle beam at TRIUMF in Canada and have been installed in JPARC (Tokai, Japan) at the end of 2009.


The first beam and cosmic ray tests demonstrated that tracks could be reconstructed with the required degree of precision. This achievement represents a major step forward in the construction of a vital detector for the T2K experiment.

 

The TPC are now detecting tracks produced by neutrino interaction in the near detector of T2K and provide superior information to measure the momentum and to identify these particles. 


 

Contacts:

 

Alain DELBART

Marco ZITO

05-05-2009

At the end of March 2009, the ALICE Muon Spectrometer took cosmic rays over a period of two weeks. The ALICE group at Saclay2 was closely involved in the design, development, construction and installation of a part of the chambers of this Spectrometer3. The purpose of the cosmic ray test was to check the performance of the entire system, from acquisition to reconstruction of the data. The acquisition system readout about a million channels and the data was recorded on the computing grid. Almost 15,000 tracks were reconstructed under conditions close to those of the real experiment. The cosmic test was a success, demonstrating the performance and the stability of the spectrometer chambers. It also revealed some weak points of the system. Tests are currently underway to correct the observed defaults.

Another cosmic test is planned for August, a few weeks before the first LHC beam injections, involving all ALICE detectors.

 

 

Contacts:

Alberto BALDISSERI

Hervé BOREL

21-04-2009

It has now been more than two years that Antares1, the underwater telescope installed in the depths of the abyssal plains 2500 m under the Mediterranean, is scanning the skies through the Earth in search of neutrinos. Over a thousand of them have already been observed until today, making it possible to establish the first views of the heavens to search for high-energy cosmic neutrinos, particles that may be able to teach us more about the most violent phenomena in the Universe.

 

 

Neutrinos are particles that interact very little with matter. Emitted by the most violent cataclysms of the Universe, they could prove that these phenomena are responsible for cosmic rays, mainly protons, which are constantly bombarding the Earth. These protons actually reach us after having been diverted from their paths by intergalactic magnetic fields, which prevents us from identifying their origin.

 

Their very weak interaction with matter makes neutrinos hard to detect. This problem can only be overcome by using enormous detectors, shielded against the cosmic rays. Antares, installed off the coast of Toulon, is protected against this radiation by a natural shield - 2000 m of water. Work on the detector took two years and its deployment was achieved in May 2008. Today 885 "eyes", together with the electronic equipment designed and built by CEA-IRFU (Institute of Research into the Fundamental Laws of the Universe) to read and process the data, are strung out in groups of threes along 12 flexible lines 450 m high. These lines are higher than the Eiffel Tower and are anchored to the seabed covering an area as large as four football fields.

 

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