The international CUPID-Mo experiment conducted by French laboratories of IN2P3, CEA/IRFU and CEA/IRAMIS has been testing the use of Molybdenum-based crystals since last April to detect double beta decay without neutrino emission. The experiment is gradually gaining strength and already shows a near-zero background in the region of interest, which is very promising. The scientists of the collaboration made an update in the occasion of the official inauguration on 11 and 12 December 2019.


Nucleons (protons and neutrons), the components of the atomic nucleus, can be polarized. This means that their spins are preferentially aligned along a quantization axis. The spin is a quantum property of a particle and has its classical analogue in a spinning top. The strong interaction that acts among nucleons in the atomic nucleus is sensitive to the polarization. Therefore, for a better understanding of the strong interaction, it may be interesting to measure the polarization of the particles produced in a nuclear reaction. The devices to measure the polarization are called polarimeters. Conceiving, building, testing and validating polarimeters requires proton and neutron polarized beams, of known polarization. Today, such beams of energy in the GeV range are available only at the Nuclotron complex of JINR, Dubna, in Russia. In order to optimize neutron and proton polarimetry at energies of few GeV, analyzing powers have been measured with Nuclotron beams on different targets: Carbone, mylar, paraffine, as well as on a heavier target, cupper, for beam momenta in the range 3 – 4.2 GeV/c. The present work indicates that high-energy polarimetry shows specific characteristics, opening the way to innovative experimental approaches. These results have been published in EPJA, as ‘Special article’, section ‘New Tools and Methods’ [1].


INCL (Liège intranuclear cascade) is a simulation code known for its ability to model light particle-nucleus interactions. It is used in very various fields, such as proton therapy, neutron sources, radioactive ion beams or ADS's (Accelerator Driven Systems). In order to extend its capabilities in the field of higher energy reactions, in connection with cosmic rays or with the study of hypernuclei, a team of physicists led by Irfu has recently developed a new version of the code involving strange particles. This work was at the heart of a recently defended thesis (2019) and the new possibilities offered by this code were published in early 2020 in the journal Physical Review C [1].


Following SPIRAL2's commissioning authorization issued by the French Nuclear Safety Authority (ASN) on July 8, 2019, many crucial steps were successfully completed by the end of 2019. A first proton beam was accelerated to 33 MeV, the nominal energy by the SPIRAL2 linear accelerator (LINAC) and a first test experiment was achieved the Neutron For Science (NFS) experimental room.

These first results in 2019 are very promising. They will continue in 2020 with the increase in beam power up to 10% of the maximum design power. In parallel test experiments in NFS will be carried out.



A few microseconds after the Big Bang the Univers may have gone through a deconfined state of quarks and gluons, the Quark–Gluon Plasma (QGP). The QGP can be recreated in high-energy heavy-ion collisions. In particular at the LHC at CERN, the QGP behaves like a fluid. All particles, light, strange, or charmed flow collectively as if being carried by the same fluid, proving the strength of the interactions between QGP constituents. The ALICE Collaboration at the LHC, with decisive contributions from the Irfu teams, has just published, in the prestigious Physical Review Letters journal, the first measurement of the elliptic flow of Υ(1S) (a particle composed of a beauty quark and its antiquark). This resonance appears as the first particle at the LHC not flowing with the fluid. This pioneering result opens up the path for deeper studies of the QGP.


To measure cosmological parameters, the Euclid space telescope will use two main probes: gravitational lensing (Weak Gravitational Lensing) and galaxy distribution (Galaxy Clustering). These measurements will allow us to study dark energy and dark matter, which affect the growth of cosmic structures and the accelerated expansion of the Universe.

In addition to its implications on instrumental developments and data processing, Irfu is actively involved in the development of algorithms needed to prepare the extraction of cosmological parameters that will be derived from Euclid measurements.

Coordinated by Valeria Pettorino, physicist at Irfu's CosmoStat laboratory, in collaboration with Tom Kitching (UCL[1]) and Ariel Sanchez (MPE[2]), an international team from the Euclid collaboration with complementary expertise in theory and observation has just completed a 3-year study characterizing the performances expected from Euclid for these observational probes.

Publication an Arxiv: https://arxiv.org/pdf/1910.09273.pdf

[1] University College London ; [2] Max Planck Institute for extraterrestrial physics
A collision of the Milky Way with a small galaxy accurately dated by the study of the star ν Indi

ν Indi is a bright star (visual magnitude mv = 5.3) visible with the naked-eye from the southern hemisphere. By using ground data (ESO telescopes), space data (Gaia and Tess missions) and by combining very diverse spectroscopic, astrometric, kinematic or asteroseismological information, an international team including two researchers from the Department of Astrophysics / AIM Laboratory of CEA-Saclay was able to determine the epoch, between 11.6 and 13.2 billion years ago, of a collision between our galaxy and a small dwarf galaxy, Gaia-Enceladus. This work is published in the journal Nature Astronomy, January 2020.


The EUPRAXIA project has just completed its design study phase with the delivery of the Conceptual Design Report (CDR) at the end of 2019. The strong involvement of IRFU, particularly in the field of particle beam physics, has made it possible to show that solutions exist for the realization of a plasma wakefield accelerator, with a beam quality approaching that of conventional accelerators.
Detailed studies of the physical mechanisms involved have efficiently guided the numerical simulations, each lasting more than 10 hours on 2048 computing nodes, to demonstrate that all the objectives on the output beam can be achieved with a plasma of 30 cm long, 1.1017 cm-3 electronic density and a laser of 400 terawatts power, 50 joules energy. Innovative methods have been developed for accelerating and driving the beam through the two plasma stages to the end user without degrading the beam. A first analysis of error tolerances allowed to identify the most sensitive components to which particular care should be taken during the fabrication and implementation.


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