Feb 12, 2024

With more than 5,000 scientists, engineers, technicians, administrators and students, CMS is one of the largest scientific collaborations in the world. With members from more than 240 institutes and universities in nearly 50 countries around the world, the collaboration exploits the data provided by the CMS experiment, one of the two giant general-purpose detectors installed along the circumference of the LHC, CERN's Large Hadron Collider.

Gautier Hamel de Monchenault, a physicist in the particle physics department at CEA-IRFU, was elected on Monday 12 February 2024 as the spokesperson for the CMS collaboration at CERN. He will hold this prestigious position from 1 September 2024 to 31 August 2026. He will be the 10th spokesperson for the CMS collaboration and the second French spokesperson to lead one of the four LHC experiments.

These intense years will see the end of the third data-taking period of the LHC as we know it, and the start of the installation of detector upgrades in preparation for the high-luminosity HL-LHC data, as well as the update of the European particle physics strategy.

Jan 22, 2024
A comprehensive revision of the summation method lays new and solid foundations for the calculation of antineutrino spectra emitted by a nuclear reactor. This major advance sheds new light on the origin of the reactor antineutrino anomalies, and will be

Supported by CEA's "digital simulation" cross-disciplinary program, Irfu, the Laboratoire National Henri Becquerel of DRT and the Service d'Étude des Réacteurs et de Mathématiques Appliquées of DES teamed up to carry out a thorough review of calculations of antineutrino spectra from nuclear reactors. A complete revision of the summation method lays a new and solid foundations for these calculations, and was featured as the Physical Review C  journal editor’s suggestion [1] on November 27, 2023. This revision incorporates numerous improvements in the beta decay modeling of the thousands of branches making up a reactor antineutrino spectrum, and in the use of nuclear evaluated data. It also quantifies all the systematic effects known to influence the calculations, providing for the first time a complete uncertainty model. This major advance now makes the summation model, long criticized for being approximate and incomplete, a robust tool for predicting reactor antineutrino spectra and for interpreting current and future experimental measurements. This work will likely stimulate targeted research to check and improve the experimental inputs, with potentially wide-ranging impact, from weak-interaction physics to many aspects of nuclear reactor science and technology. It also sheds interesting light on the origin of reactor antineutrino anomalies [2,3].

Feb 08, 2024
Exotic, very neutron-rich nuclei: a laboratory for nuclear interactions

For the first time, an experiment has provided key observations on the spectroscopy of the neutron-rich unbound oxygen nuclei (proton number Z = 8), oxygen 28 (N = 20) and its neighboring isotope at N = 19, oxygen 27.  They were produced in high-energy reactions and observed by direct detection of their decay products, 24O and three or four neutrons. The study shows that it is possible to constrain the parameters of ab initio interactions from the energy differences of the observed states with respect to the last bound isotope - 24O (N = 16). These groundbreaking results were published in the journal Nature [Nat23].

Given the complexity of studying unbound nuclei, an exceptional detection system was implemented at the world's most powerful radioactive ion beam facility: RIBF in Japan. The data were obtained by an international collaboration (Samurai21) of around a hundred physicists (from 36 laboratories), including a team* of physicists from Irfu who were responsible for operating a key detector for the measurements, Minos. The experiment, carried out on the Samurai area of the RIBF (Radioactive Ion Beam Factory) facility at RIKEN in Japan, was piloted by groups of physicists from Titech (Tokyo Institute of Technology) and by the RIKEN-RIBF teams.
 

Jan 25, 2024
ESA's Scientific Program Committee has adopted the LISA mission, giving the go-ahead for construction of the instrument and satellites. For the first time, LISA will observe the Universe through gravitational waves from space.

ISA (Laser Interferometer Space Antenna), the European Space Agency's large-scale mission to explore the Universe by observing the many sources of gravitational waves, was adopted on Thursday January 25 by ESA's Scientific Programs Committee, meaning that the concept and technology are recognized as sufficiently advanced for construction of the instrument and satellites to begin. Launch is scheduled for 2035.

This mission will revolutionize astrophysics, cosmology and fundamental physics, with 3 satellites orbiting the Sun in a 2.5 million km triangle to detect gravitational waves emitting in the millihertz band, such as supermassive black hole binaries. These 3 satellites exchange laser beams to interferometrically detect distance variations of the order of ten picometers induced by gravitational waves. Irfu is heavily involved in the LISA project, contributing to the instrument, data analysis and source science. It is in charge of the reference mass simulator and the stable structure for testing the interferometric core, the analysis of alerts, a contribution to the global analysis and co-leading of the project for France. It is also preparing the scientific exploitation and in particular the tests associated with fundamental physics, the study of the primordial Universe and the study of magnetic fields in white dwarf binary systems.

Jan 22, 2024

The James Webb Space Telescope has produced a new portrait of the atmosphere of exoplanet WASP-39b, a "hot Saturn" some 700 light-years away. After the first near-infrared observations in 2022, which revealed for the first time the presence of sulfur dioxide (SO2) in the atmosphere of an exoplanet, it was observed again in 2023, but this time in the far infrared, using the MIRI spectrometer. This new observation enabled the international research team, including Saclay's Astrophysics Department, to confirm the presence of this molecule in the atmosphere of WASP-39b and to constrain its abundance. This recent study demonstrates that photochemistry shapes the atmosphere of WASP-39b over a wide range of wavelengths.

The study was published in the prestigious journal Nature.

Jan 17, 2024

To unravel this mystery, several teams with diverse skills from the Astrophysics Department had to come together, as the architecture that unites the star to its planet is highly complex. They had to combine a detailed understanding of stellar and planetary physics, exploring their interactions, with a thorough knowledge of the observations made by NASA's Kepler satellite to be able to decipher the data.

The study shows that the observed rarity seems to derive not from observational bias, but rather from physical causes. Tidal effects and magnetism are sufficient to explain qualitatively and quantitatively the migration of nearby planets around fast-rotating stars. Moreover, this migration appears to be dependent on the spectral type (fundamentally linked to mass) of the star. While these results are promising, it is nevertheless necessary to expand the sample size to better constrain scarcity and better understand the mechanisms at play. In particular, this study highlights the importance of considering the spectral type of stars (their masses) if we are to correctly model star-planet interactions.

This work is published in Astronomy & Astrophysics.

Jan 22, 2024
A comprehensive revision of the summation method lays new and solid foundations for the calculation of antineutrino spectra emitted by a nuclear reactor. This major advance sheds new light on the origin of the reactor antineutrino anomalies, and will be

Supported by CEA's "digital simulation" cross-disciplinary program, Irfu, the Laboratoire National Henri Becquerel of DRT and the Service d'Étude des Réacteurs et de Mathématiques Appliquées of DES teamed up to carry out a thorough review of calculations of antineutrino spectra from nuclear reactors. A complete revision of the summation method lays a new and solid foundations for these calculations, and was featured as the Physical Review C  journal editor’s suggestion [1] on November 27, 2023. This revision incorporates numerous improvements in the beta decay modeling of the thousands of branches making up a reactor antineutrino spectrum, and in the use of nuclear evaluated data. It also quantifies all the systematic effects known to influence the calculations, providing for the first time a complete uncertainty model. This major advance now makes the summation model, long criticized for being approximate and incomplete, a robust tool for predicting reactor antineutrino spectra and for interpreting current and future experimental measurements. This work will likely stimulate targeted research to check and improve the experimental inputs, with potentially wide-ranging impact, from weak-interaction physics to many aspects of nuclear reactor science and technology. It also sheds interesting light on the origin of reactor antineutrino anomalies [2,3].

 

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