Mar 10, 2021
The ATLAS detector equipped with a new charged particle tracking device for the HL-LHC.
The high luminosity phase of the LHC (HL-LHC) should enable the collection of a dataset unprecedented in the history of particle physics. In order to record these data, the Atlas detector will undergo a major upgrade. IRFU, via the Paris-Cluster in synergy with two other laboratories in Ile de France, is committed to the construction of a part of the internal tracker.
Jan 13, 2021
Nearly 200 researchers were involved in collecting, processing and assembling images of half the sky to prepare for the start of observations by DESI, the Dark Energy Spectroscopic Instrument, which aims to solve the mystery of dark energy. In order for DESI to begin its 5-year mission (2021-2026) to produce the largest 3D sky map ever made, researchers first needed a gigantic 2D map of the Universe.
Dec 18, 2020
The main objective of the KATRIN experiment is the measurement of the mass of the three neutrinos of the Standard Model of Particle Physics. But the analysis of the beta decay spectrum of tritium also allows to search for the trace of a hypothetical fourth neutrino, called sterile neutrino. The collaboration has just published its first analysis in Physical Review Letters (see article) based on four weeks of data acquired in 2019.
Dec 10, 2020
Within the framework of a collaborative project between the DES/DDSD and the DRF/IRFU, a feasibility study of muography potential for the auscultation of nuclear reactors was initiated in 2017. After an initial evaluation phase carried out by IRFU using numerical modelling, first data were taken on the G2 reactor block, located at CEA Marcoule and shut down in the early 1980s, from February 2020.
Oct 02, 2020
Precision measurements via the decay of the Higgs boson into light particles, the photons
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.
Aug 03, 2020
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].
Jul 20, 2020
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.
Jul 08, 2020
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.
Jun 28, 2020
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.
Jan 08, 2020
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.
Dec 20, 2019
A team from IRFU's Department of Particle Physics (DPhP) has just conducted the most accurate study to date of the mass of cosmic neutrinos, including both standard model neutrinos and sterile neutrinos contributing to dark matter. The researchers used the spectra of nearly 200,000 distant quasars measured by the Sloan Digital Sky Survey (SDSS) eBOSS project to map the distribution of hydrogen at very remote times in the history of our universe, ten to twelve billion years ago.
Nov 21, 2019
The missing mass of the universe or non-baryonic dark matter is probably made up of particles that remain to be discovered. Massive and neutral, with very weak interactions, they still escape a detection that would identify them. While conventional photons are massless, dark matter could be made up of particles of a new type, similar to massive photons.
Nov 20, 2019
After a decade-long search, scientists have for the first time detected a gamma-ray burst in very-high-energy gamma light. This discovery was made in July 2018 by the H.E.S.S. collaboration using the  huge 28-m telescope of the H.E.S.S. array in Namibia. Surprisingly, this Gamma-ray burst, an extremely energetic flash following a cosmological cataclysm, was found to emit very-high-energy gamma-rays long after the initial explosion. This discovery was published in Nature.    
Oct 28, 2019
‘First light’ for the Dark Energy Spectroscopic Instrument (DESI): as the installation phase nears completion, this new instrument is due to undergo final tests before starting to create a giant map of the sky in early 2020, a mission that is scheduled to run for five years.
Jul 23, 2019
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.
Jul 12, 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.
Apr 11, 2019
The Dark Energy Spectroscopic Instrument (DESI) is intended to make the spectroscopic survey of 35 million galaxies and quasars from 2020 onwards, to study precisely the properties of dark energy. Its installation, started in 2018, has recently entered a new phase with the reception and assembly of the first two spectrographs out of the 10 that the instrument will include.
Feb 25, 2019
Neutrinos from the Big Bang have been traveling the Universe for more than 13 billion years. They are almost undetectable but their footprint on the formation of large structures in the Universe, such as galaxies, can be detected. For the first time, this trace of the "diffuse neutrino background" from the Big Bang on the "baryonic acoustic oscillations" (BAO) has been deduced from the survey of 1.2 million galaxies of the "Sloan Digital Sky Survey" (SDSS).
Dec 10, 2018
In 2018, IRFU is participating  in a publication CUPID-0: the first array of enriched scintillating bolometers for 0νββ decay investigations which reviews a first matrix of bolometers installed in the Gran Sasso laboratory in Italy, with the objective of tracking the double beta decay without neutrino emission (0νββ) that will reveal the nature of neutrinos.
Oct 10, 2018
What is the mass of neutrinos? To answer this fundamental question, the KATRIN experiment was designed and built by an international collaboration at the Karlsruhe Institute of Technology. On June 11, 2018, an international symposium marked the beginning of data acquisition. The first electron spectra from tritium decay have been analyzed with an analysis chain developed at IRFU. Everything conforms to the required specifications and the first long data taking campaign for physics can start.
Jul 13, 2018
A hundred years old mystery might get resolved with the detection of neutrinos by the IceCube collaboration coming from a known active black hole. Irfu, which coordinate those observations with the H.E.S.S. telescope, did not detect anything for now but the multi-messenger astronomy has just begun…
Jun 19, 2018
The ATLAS and CMS collaborations, involving teams from CEA/IRFU and CNRS/IN2P3, announced on 4 June 2018 at the LHCP conference the direct observation of the coupling of the quark top to the Higgs boson. Studying the interaction between the Higgs boson and the heaviest elementary particle known, the quark top, is a way of investigating the effects of new physics, which must take over from the standard model.
Jun 18, 2018
A new project is opening today, Friday, June 15, 2018, at the LHC, the large Hadron Collider. Initiated in 2011, this project aims to bring into service by 2026 a high-luminosity LHC (HL-LHC) that will increase the number of proton-proton collisions and collect more data. France contributes significantly to this project (up to € 180 million, including payroll).
Apr 09, 2018
The HESS international collaboration, to which CNRS and CEA contribute, has published the results of fifteen years of gamma ray observations of the Milky Way. Its telescopes installed in Namibia have studied populations of pulsar wind nebulae and supernova remnants, as well as microquasars, never before detected in gamma rays. These studies are supplemented by precise measurements such as those of the diffuse emission at the center of our Galaxy.
Mar 07, 2018
The T2K collaboration, whose goal is to study and measure neutrino oscillations, is publishing new results on the interaction of neutrinos with nuclei. This study, in which the T2K group of the IRFU plays a major role, is crucial in that it allows the dominant uncertainty on the oscillation parameters to be restrained. For the first time, protons emerging from the neutrino-nucleus interaction have been characterized using new variables capable of exposing and characterizing nuclear effects.
Feb 27, 2018
More than twenty years after the discovery of the acceleration of the expansion of the Universe, the nature of the physical phenomenon at the origin of this acceleration, called "dark energy", is still unknown. The current model of cosmology is based on general relativity as a theory of gravitation and establishes a theoretical prediction for the quantity of galaxies that form at a given period of the Universe. This cosmological parameter is called the growth rate of cosmic structures.
Dec 06, 2017
For more than 10 years now, Irfu physicists and engineers have been developing in Saclay the necessary equipment for the GBAR experiment, designed to test the behaviour of antimatter under terrestrial gravity. An important step has just been taken with the installation at the Cern of a new positron source using on an electron linac, and the transport to the Cern of the positron trapping system built at Saclay. The new source produced its first positrons on November 17, 2017.
Nov 21, 2017
Under the dome of the Palais de l'Institut de France of the Académie des Sciences, a prize-giving ceremony took place on Tuesday 21 November. Three researchers from Irfu were rewarded for their outstanding work, in the field of cosmology for Nathalie Palanque-Delabrouille (DPhP) and David Elbaz (DAp), and on the properties of dust and interstellar gas in the Near Universe for Suzanne Madden (DAp).
Nov 09, 2017
The LHC's Atlas collaboration at Cern has observed a rare process: the production of Higgs bosons in association with a top quark and top antiquark pair. This work, supervised by an Irfu researcher, opens up perspectives on the study of the Higgs mechanism that gives mass to particles.
Oct 19, 2017
Data collected at the LHC (Cern) were processed to provide the most accurate assessment of an asymmetry in top quark and top antiquark production. The result is that the measured value is compatible with the prediction of the standard particle model.


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