The search for double beta decay without neutrino emission (0νββ) is one of the major challenges of contemporary physics, because its observation would make a clear statement about the nature of the neutrino itself and potentially on the origin of the matter/antimatter asymmetry of our universe. The CUPID collaboration, in which several researchers from IRFU and IN2P3 are involved, is actively researching this process using scintillating bolometers as detectors. In June 2020, the CUPID-Mo demonstrator experiment, which is located at the Modane underground laboratory, demonstrated the excellent potential of this detection method with only 2.264 kg of 100Mo and one year of data collection. In the coming years, the objective of the CUPID collaboration is to design one of the most sensitive experiments ever built by increasing the total mass of 100Mo to 250 kg. Three articles have just been published on the technological and methodological choices needed for this change of scale, while maintaining the required performances of the final experiment.
As part of the luminosity increase of the Large Hadron Collider (LHC), the first phase of the ATLAS experiment upgrade is coming to an end, before a restart planned for early 2022. To meet the requirements of physics in a highly radiative environment with a high particle flux, the two internal wheels of the muon spectrometer will be replaced by new devices: the New Small Wheels (NSW).
After several years of R&D and production, IRFU has just sent the last of the 32 detection modules that will be integrated into the NSW at CERN. This corresponds to the assembly of about 400 m2 of gas detectors based on Micromegas technology: a record!
The muon spectrometer of the ATLAS experiment has been an important contribution of IRFU since the design, and IRFU is still in charge of the alignment today. The spectrometer plays a key role in the reconstruction of high-energy muons, the detection of which is crucial for the search of phenomena beyond the Standard Model. The spectrometer consists of about 1200 muon chambers that form a gigantic edifice 44 m long and 24 m in diameter. Despite these imposing proportions, the relative positions of the chambers must be known with an accuracy of the order of 50 μm in order to achieve the optimum performance of the spectrometer. To this end, a network of optical lines is used to continuously monitor the positions of the chambers relative to each other, as well as their deformations. An elaborate procedure for reconstructing the 56,000 parameters determining the alignment (for the central part) has been developed by a team at IRFU in order to obtain the precision required for the reconstruction of high-energy muons. This method, adopted by the ATLAS collaboration, is presented for the first time in an ATLAS note.
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. The year 2021 is brilliantly starting for the Paris-Cluster, which has just passed an important milestone in this endeavour: the first phase of the assembly and testing processes developed by our teams has been validated by the Atlas collaboration.
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. Based on 200,000 images from 1405 nights of observations on three telescopes and several years of satellite data, this 2D map is the largest ever produced, based on the area of sky covered, the depth of the imagery and the more than one billion images of galaxies it contains.
After three years of reflection and development, the "Astro-Colibri" application has just been launched. This digital interface, created by researchers at Irfu/DPhP, aims to make information on transient and multi-messenger phenomena easily accessible in real time. The need to react quickly to the most violent explosions in the universe and the large amount of information provided by the global network of observatories requires new approaches and new tools. Through "Astro-Colibri", several observatories now have the capacity to coordinate in monitoring and identifying the sources of physical phenomena in the transient sky.
The platform, which exists in the form of a smartphone application (IOS and Android) and a website, allows alerts to be put into their observational context by cross-referencing them with already known data. This saves researchers a considerable amount of time. In addition, the application anticipates the best possible observation periods for a given observatory. This free interface is also a fun and practical tool for astrophysics enthusiasts who will be able to easily move around this functional application.
Space-based experiments such as the Fermi satellite's Large Area (LAT), which detects gamma rays above 100 MeV, reveal a population of sources with no astrophysical counterpart at other wavelengths. Some of these have the characteristics required to be "dark matter subhalo" candidates predicted by cosmological simulations to populate the Milky Way halo. The range of dark matter candidates with masses below a few hundred GeV are already excluded by Fermi observations. To test the higher masses, higher energy range observations are needed and the H.E.S.S. ground-based Cherenkov telescope array is the ideal instrument. Thus, a team of physicists from Irfu and laboratories in Heildelberg and Tübingen conducted a thorough selection of some of the most promising objects to be observed by H.E.S.S. to elucidate their possible identification as 'dark matter subhaloes' at TeV. The H.E.S.S. results exclude this interpretation for dark matter particles in the TeV range. This work was published in the Astrophysical Journal in July 2021 (arxiv link).
On 29 August 2019, scientists from the H.E.S.S. collaboration recorded one of the brightest cosmic explosions ever observed in the Universe. This gamma-ray burst emitted the most energetic photons ever detected in this type of event. Under the direction of Irfu researchers, the observations continued for several days. The analysis of the data collected calls into question the origin of the rays produced during the explosion. These results has been published by the international team, which includes researchers from CEA and CNRS, in the journal Science on 4 June 2021.
H.E.S.S., located in Namibia, is a system of five imaging atmospheric Cherenkov telescopes that has been studying cosmic rays since 2003. In 2016, the cameras of the first four telescopes were completely refurbished using state-of-the-art electronics and in particular the NECTAr readout chip designed by the the DEDIP/Irfu laboratory.
The analysis of this exceptional gamma-ray burst was led by a physicist from the DPHP/Irfu astroparticle group.
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Dernière mise à jour : Feb 16th, 2024
