The Tevatron CDF and D0 collaborations have just received the 2019 Prize for Particle and High Energy Physics awarded by the European Physical Society for the discovery of the top quark in 1995 and the detailed measurements of its properties from 1995 to the present. This prize thus rewards the physicists and engineers of the Irfu who contributed to the construction of the D0 detector, the discovery of the quark top, and conducted numerous studies on top quark physics.
The STEREO experiment releases new results based on the detection of about 65000 neutrinos at short distance from the research reactor of the ILL-Grenoble. The improved accuracy is rejecting the hypothesis of a 4th neutrino in a large fraction of the domain predicted from the reactor neutrino anomaly. Profiting from a good control of the detector response, STEREO now also releases its first absolute measurements of the neutrino rate and the spectrum shape.
It is possible to trace the shape of a drum from its vibration modes. Similarly, it is possible to measure the 3D structure of the proton and access its elementary components, quarks and gluons, from observables obtained using deeply virtual Compton scattering experiments off the proton. By studying this scattering process, we can access this geometric information. This research topic is very active and mobilizes a large international theoretical and experimental community. As part of the PARTONS (PARtonic Tomography Of Nucleon Software) project, physicists from Irfu and NCBJ in Warsaw successively performed two detailed analyses using all the measurements associated with this process published since the early 2000s. This represents nearly 2600 measurement points and 30 observables from 6 different experiments. This work, published in the European Physical Journal C [1, 2], is now the most advanced analysis of these experimental data. New data, combined with new analysis methods, will enrich the PARTONS library in the future; these observables (Compton form factors) will make it possible to go one step further in the reconstruction of the proton structure in 3D.
The series of Jefferson Laboratory (USA) experiments dedicated to the measurement of electron-proton elastic scattering showed that the extracted information on the proton structure did not agree when extracted from two kinds of experiments. To reconcile these results, it was suggested that, beyond the exchange of one photon, that is the dominant mechanism, the exchange of a second photon could become important. The presence of a second photon would bring serious consequences, casting doubts on the results of number of experiences. That’s why the search of such mechanism motivated three independent experiments, recently realized. We have analyzed all the obtained results and shown that two photon exchange is not enhanced. Other explanations are favored, as a precise calculation of radiative corrections. This study, performed by two researchers of IRFU and JINR-BLTP, Dubna (Russia) has been published in the Physical Review C.
Predicting properties of, e.g., molecules or atomic nuclei from first principles requires to solve the Schrödinger equation with high accuracy. The computing cost to find exact solutions of the Schrödinger equation scales exponentially with the number of particles constituting the system. Thus, with nuclei composed of tens or hundreds of nucleons, it necessitates accurate approximate methods of lower computing cost. However, such methods can be applied to a limited number of systems: the weakly correlated ones. Consequently, a universally applicable method is still missing. Employing a novel formalism recently developed at Irfu/DPhN , highly accurate solutions of the Schrödinger equation – in the context of the exactly solvable Richardson model - have been obtained, independently of the weakly- to strongly-correlated character of the system. This work has been performed in collaboration with ab initio quantum chemists from Rice University. This exciting new achievement, paving the way for precise ab initio computations of molecular or nuclear properties of a large number of systems, was recently published in Physical Review C  and highlighted as the Editor’s suggestion.
Pairing is ubiquitous in physics. From superconductivity to quantum shell structure, coupling particles into pairs is one of nature's preferred ways to lower the energy of a system. New results obtained at the Radioactive Isotope Beam Factory (RIBF, Japan) with the MINOS device, which was conceived and constructed at Irfu, show for the first time that pairing also plays an important role in single-proton removal reactions from neutron-rich nuclei. These results show that proton-removal cross sections can be used as a tool to investigate pairing correlations for very neutron rich nuclei not accessible via spectroscopy. Indeed, the latter are produced in too small quantities to consider spectroscopy, studying the gammas emitted during de-excitation for example. This study was recently published in Physical Review Letters .
An international collaboration led by the institutes of CEA-IRFU and of RIKEN (Japan) demonstrates, for the first time, the exceptional stability of the very-neutron rich nickel-78 nucleus and its doubly-magic character. The experiment at RIKEN was made possible by the unique combination of the MINOS device developed at CEA-Irfu and the very exotic beams produced by the RIBF facility of the Japanese accelerator.These results are published in Nature [Nat19].
Lisa Bugnet is one of 35 young women researchers who won the L'Oréal-Unesco Fellowships for Women in Science in 2019. As an asteroseismologist at the Dynamic Laboratory of Stars, (Exo)planets and their Environment of the DAP/Irfu, she uses seismic waves emitted by stars to probe their heart and understand their evolution from birth to the end of their life.
A study conducted by astrophysicists of the Department of Astrophysics-AIM Laboratory of CEA-Irfu has revealed a large number of galaxies as massive as the Milky Way in the distant universe, thanks to the large interferometer ALMA (Atacama Large Millimeter/submillimeter Array) in Chile. These galaxies have hitherto remained invisible due to the attenuation of their brightness by interstellar dust. They are 10 to 100 times more numerous than all those detected so far, at distances where the universe was only two billion years old. This great abundance of massive galaxies in the young universe is in contradiction with current theoretical models of galaxy formation and represents a new challenge for our understanding of the early ages of the universe. These results are published in the journal Nature on August 7, 2019.
The installation of DESI, the Dark Energy Spectroscopic Instrument at the Kitt Peak Observatory in Arizona, has just passed an important milestone: with 6 operational spectrographs on site, the minimum configuration required to meet the scientific objectives of the project has been reached. At the end, DESI will have 10 spectrographs and will commit itself from 2020 to the spectroscopic survey of 35 million galaxies and quasars, to study the dark component of the Universe. Irfu, responsible for the cryogenic part of the spectrographs, has made a major contribution to the success of this installation and is currently finalizing the qualification of the cameras of the last spectrograph in Saclay. In parallel, other essential milestones for the construction of the instrument are achieved.
Thanks to the X-ray satellites Chandra and XMM-Newton, an international team including the Department of Astrophysics of CEA-Irfu has just discovered the existence of two bubbles of hot gas escaping to distances of about 500 light-years, on both sides of the massive black hole environment, in the center of our galaxy. Like the messages of Native Americans transmitted by smoke bubbles visible from afar, these "hot gas chimneys" tell us today about the intense past activity of the black hole and the central regions of our Galaxy. These results are published in the journal Nature of March 21, 2019.
An international team, led by researchers from the Department of Astrophysics/AIM Laboratory of CEA-Irfu has just highlighted a new population of very remote galaxies, which had so far escaped the deepest observations of the Universe. During the summer of 2016, at more than 5000 meters of altitude on the Chilean highlands, the antennas of the large interferometer ALMA (Atacama Large Millimeter/submillimeter Array) scrutinized for more than 20 hours one of the best studied regions of the sky. These observations revealed galaxies still unknown, very massive but opaque, emitting only a very small amont of visible light due to a large quantity of dust. These "dark" galaxies, very far away, which could be the progenitors of the most massive galaxies in the universe, reveal that the importance of star formation, during the first billion years of cosmic history, could have been largely underestimated so far. These results have just been published in the journal Astronomy & Astrophysics.
An international collaboration, involving the Astrophysics Department-Laboratory AIM of CEA irfu, participated in the study of an exoplanetary system, Kepler-107 and revealed an amazing distribution of its 4 planets of which two seem potentially resulting from a giant impact. Thanks to asteroseismology (the study of star vibrations) and the modeling of planetary transits, researchers have been able to determine the mass and radius of the central star and its planets with great precision. and highlighted the unusual density of one of the planets. This anomaly can be explained by a giant collision between planets, probably similar to the one that affected the Earth in the past to form the Moon. These results are published in the journal Nature Astronomy of Februrary 4th, 2019.
On November 29, 2018, the first version of the ECU software for the ECLAIRs instrument was delivered.
This computer, called Gamma Camera Management and Scientific Processing Unit, will be set on the Franco-Chinese SVOM satellite, designed to study gamma-ray bursts. It will allow the management of the ECLAIRs instrument and the detection of gamma-ray bursts by the SVOM mission in real time on board. This software, under the scientific responsibility of the DAp, is produced in strong collaboration between the DAp and the DEDIP within the IRFU.