The BINGO project is funded in large part through an ERC (2020-2025). BINGO is a project aiming to set the grounds for large-scale bolometric neutrinoless double-beta-decay experiments capable of investigating the effective Majorana neutrino mass at a few meV level. It focuses on developing innovative technologies to achieve a very low background index, of the order of 10−5 counts/(keV kg yr) in the region of interest. The BINGO demonstrator, called MINI-BINGO, will be composed of Li2MoO4 and TeO2 crystals coupled to bolometric light detectors designed to investigate the promising double-beta-decay isotopes 100Mo and 130Te. This will allow us to reject a significant background in bolometers caused by surface contamination from α-active radionuclides by means of light yield selection. In addition, BINGO introduces new methods to mitigate other sources of background, such as surface radioactive contamination, external γ radioactivity, and pile-up due to random coincidence of background events.

Collaboration website : http://www.bingo-neutrino.eu/

The DAMIC-M (DArk Matter In CCDs at Modane) experiment employs thick, fully depleted silicon charged-coupled devices (CCDs) to search for dark matter particles with a target exposure of 1 kg-year. It is funded in large part through an ERC (2018-2023) and by NSF. A novel skipper readout implemented in the CCDs provides single electron resolution through multiple non-destructive measurements of the individual pixel charge, pushing the detection threshold to the eV-scale. DAMIC-M will advance by several orders of magnitude the exploration of the dark matter particle hypothesis, in particular of candidates pertaining to the so-called "hidden sector." Indeed, DAMIC-M will search for low mass WIMPs (<5GeV/c2) through the nuclear recoil they would induce on silicon nuclei but will also probe much lighter candidate such as particles of the hidden sector through the electronic recoil they would provoke. DAMIC-M in its final stage will comprise 52 CCD modules for a total target mass of around 700 grams and a radioactive background goal of less than 1 event/keV/kg/day. It is going to be installed in the Modane Underground Laboratory in France in 2024. A prototype, the Low Background Chamber (LBC), with 20g of low background Skipper CCDs, has been successfully installed and commissioned in 2022 at LSM and is already giving world leading results in the search for leptophilic dark matter.

Collaboration website : https://damic.uchicago.edu/index.php

Directional Dark Matter Detection (DDM) can open a new signature for Weakly Massive Interacting Particles Dark Matter. The directional signature provides in addition, an unique way to overcome the neutron and neutrino backgrounds. In order to get the directional signature, the DDM detectors should be sensitive to low nuclear energy recoils in the keV range and have an angular resolution better than 20°.
The MIMAC detector consists of a matrix of micro-Time Projection Chamber (TPC) developed in a collaboration between LPSC (Grenoble) and IRFU (Saclay). The detector first commissioning was performed at LSM in 2018 and the collaboration foreseen new test of an upgraded detector in 2025.

An Advanced Spectrometer to Study Rare Radioactive Processes
OBELIX spectrometer plays a key role in a unique experiment searching for double beta decay of the isotope ⁸²Se to excited states of the daughter nucleus ⁸²Kr. This process has never been detected before, and its detection could open a new direction in fundamental physics.

Present status and next steps: Over three years of continuous research, sensitivity was achieved at a level of T_1/2 ∼ 4−5×10²² years. This is approximately three times higher than previously published limits for such measurements. During the measurements, the first statistically significant indicators of rare radioactive decay with a confidence level of ~3σ were found. This level is consistent with theoretical expectations. The additional detection of the double beta decay to excited states (in our case with ⁸²Se) is important for further understanding of the structure of the atomic nucleus and rare nuclear processes. The OBELIX experiment shows that the sensitivity achieved allows us to study phenomena that were previously considered inaccessible.

The studies will be continued over the next 1-2 years with the aim of confirming the observed effect with high reliability (>4−5σ) or denying it. In parallel, preparations are underway for new experiments aimed at studying other rare radioactive processes.

International cooperation

OBELIX experiment is the result of an international collaboration that brings together leading research centers, including IEAP CTU, JINR, CNRS and INFN. This project confirms the status of the LSM laboratory as one of the world leaders in the study of rare physical phenomena.

Studies of long-term cell culture storage in conditions of extremely low radiation background represent biological experiments in LSM. Normal human dermal fibroblasts are stored frozen in liquid nitrogen at - 196°C. Cell viability, level of apoptosis and changes of cell cycle are periodically evaluated for cell cultures stored as controls in normal laboratory conditions and at reduced radiation background in underground laboratory. Advanced characteristics of cell population are performed immediately upon cells thawing and after 24 hours incubation in normal cell culture media at 37°C. Level of DNA damage is assessed by immunoflurescent quantification of gamma-H2AX foci, which are sensitive molecular markers for DNA double-strand breaks.