We report a precision measurement of Compton scattering on silicon atomic shell electrons down to 23eV. A skipper charge-coupled device (CCD) with single-electron resolution, developed for the DAMIC-M experiment, was exposed to a 241Am γ-ray source over several months. Features associated with the silicon K, L1, and L2,3-shells are clearly identified, and scattering on valence electrons is detected for the first time below 100eV. We find that the relativistic impulse approximation for Compton scattering, which is implemented in Monte Carlo simulations commonly used by direct detection experiments, does not reproduce the measured spectrum below 0.5keV. The data are in better agreement with ab initio calculations originally developed for X-ray absorption spectroscopy.Learn more >>

The Low Background Chamber (LBC) has been installed and commissioned at the LSM in 2022. The LBC cryostat is open in the photo, showing the ancient Roman lead shielding surrounding the copper box with the CCDs.

Results from the first underground operation of DAMIC-M, with an integrated exposure of 85.23 g days. The figure shows 90% C.L. upper limits on dark matter interacting with electrons through a ultralight mediator, obtained with DAMIC-M prototype skipper CCDs installed in the Low Background Chamber. These results were highlighted as Editors' Suggestion by Physical Review Letters and published on 28 April, 2023.Learn more >>

Dark Matter (DM) particles with sufficiently large cross sections may scatter as they travel through Earth's bulk, giving rise to a characteristic daily modulation signal. The figure shows 90% C.L. upper limits on DM interacting with electrons through a ultralight mediator, obtained by searching for a daily modulation signal in DAMIC-M skipper CCDs installed in the Low Background Chamber. This work was published in Physical Review Letters on 7 March, 2024.Learn more >>

New results on the search for dark matter particles with the LBC operating at the Modane Underground Laboratory. With an improvement of orders of magnitude in sensitivity with respect to any other detector technology, DAMIC-M new results exclude for the first time that dark matter may be primarily composed of hidden-sector particles with sub-GeV mass ("freeze in" light blue line in figure).Learn more >>

The DAMIC-M Collaboration at the John W. Boyer Center of the University of Chicago in Paris on February 10-12.Learn more >>