In its standard form, double beta decay is a process in which a nucleus decays into a different nucleus and emits two electrons and two antineutrinos (2νββ). This nuclear transition is very rare, but it was detected in several nuclei with sophisticated experiments. If neutrinos are their own antiparticles, it’s possible that the antineutrinos emitted during double beta decay annihilate one another and disappear. This is called neutrinoless double beta decay (0νββ), a phenomenon never observed so far. If 0νββ is detected, we will ascertain that neutrinos are their own antiparticles, and this would be a clue as to why they get their tiny masses—and whether they played a part in the existence of our matter-dominated universe.
The CUPID-Mo experiment, installed at the Modane Underground Laboratory, after one year of data between March 2019 and April 2020 has just set a new global limit for the detection of the signature 0νββ.
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.
Photon-photon elastic scattering is a very rare phenomenon in which two real photons interact producing a new real photon pair. The direct observation of this process at high energy, impossible during decades, was done by ATLAS [1] and CMS [2] experiment at CERN between 2016 and 2019. These successes have led the two collaborations to strengthen their involvement in this new field, leading to a new measurement, currently being published by the ATLAS experiment [3]. Presented for the first time at the LHCP conference in May 2020, the new idea is to use photon collisions to search for a hypothetical axion-like particle. As with the first publications on the subject, IRFU members are at the origin of the ideas at work in the analyses carried out at CERN.
The Sloan Digital Sky Survey (SDSS) published in July a complete analysis of the largest three-dimensional map of the Universe ever created, reconstructing the history of its expansion over a period of 11 billion years.
Scientists from the large cosmological survey SDSS/eBOSS have constructed the first so-called "tomographic" map of the far Universe on a very large scale, which until now only existed in one dimension, along the line of sight of the ground-based telescope. To do this, they used the latest Lyman-alpha forest data, which indirectly plot the density of matter in the direction of bright objects, the quasars. The resulting map covers a cube of 3.26 billion light-years from observations of nearly 10,000 quasars. It is a new tool for studying the history of the Universe and its structures.
This work is published in the JCAP journal (arXiv:2004.01448).
The CMS collaboration presented its most achieved measurement of the Higgs boson properties in the two-photon decay channel at the ICHEP conference in August 2020. The results are based on the complete LHC Run 2 data recorded between 2016 and 2018 and show a level of accuracy never achieved before.
Thanks to this increased sample size, to sophisticated analysis methods using artificial intelligence and developed in part by the CMS group at IRFU, previously unimaginable measurements are now possible: the study of rare modes of production becomes possible. This painstaking work has made it possible to carry out increasingly precise measurements of the properties of the Higgs boson, making it possible to test the Standard Model of particle physics ever further. The latter has once again triumphed in this confrontation.
But with the restart of the LHC collider in 2022, and then its luminosity increase in 2027, the amount of data will be significantly larger, allowing the Standard Model to be examined from every angle.
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Dernière mise à jour : Feb 16th, 2024
