Particle Physics Division

Tilepy is a cutting-edge platform designed to optimize and facilitate the scheduling of follow-up observations of multi-messenger events[1]. Developed over the last eight years by a dedicated team of researchers at IRFU, led by Fabian Schussler, the team includes former PhD students Monica Seglar-Arroyo and Halim Ashkar, who began their contributions during their doctoral studies, as well as postdoc Mathieu de Bony de Lavergne. Tilepy, now publicly accessible, offers innovative and easy to use solutions for scheduling follow-up observations of events like gravitational waves (GW), gamma-ray bursts (GRB), and high-energy neutrinos. Tilepy has already been adopted by the international H.E.S.S. and CTA/LST-1 observatories as the default scheduling tool for multi-messenger studies.

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.

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].