학술논문
Precision measurement of Compton scattering in silicon with a skipper CCD for dark matter detection
Document Type
Working Paper
Author
Norcini, D.; Castello-Mor, N.; Baxter, D.; Corso, N. J.; Cuevas-Zepeda, J.; De Dominicis, C.; Matalon, A.; Munagavalasa, S.; Paul, S.; Privitera, P.; Ramanathan, K.; Smida, R.; Thomas, R.; Yajur, R.; Chavarria, A. E.; McGuire, K.; Mitra, P.; Piers, A.; Settimo, M.; Gutierrez, J. Cortabitarte; Duarte-Campderros, J.; Lantero-Barreda, A.; Lopez-Virto, A.; Vila, I.; Vilar, R.; Avalos, N.; Bertou, X.; Dastgheibi-Fard, A.; Deligny, O.; Estrada, E.; Gadloa, N.; Gaior, R.; Hossbach, T.; Khalil, L.; Kilminster, B.; Lawson, I.; Lee, S.; Letessier-Selvon, A.; Loaiza, P.; Papadopoulos, G.; Robmann, P.; Traina, M.; Warot, G.; Zopounidis, J-P.
Source
3 November 2022
Subject
Language
Abstract
Experiments aiming to directly detect dark matter through particle recoils can achieve energy thresholds of $\mathcal{O}(1\,\mathrm{eV})$. In this regime, ionization signals from small-angle Compton scatters of environmental $\gamma$-rays constitute a significant background. Monte Carlo simulations used to build background models have not been experimentally validated at these low energies. We report a precision measurement of Compton scattering on silicon atomic shell electrons down to 23$\,$eV. A skipper charge-coupled device (CCD) with single-electron resolution, developed for the DAMIC-M experiment, was exposed to a $^{241}$Am $\gamma$-ray source over several months. Features associated with the silicon K, L$_{1}$, and L$_{2,3}$-shells are clearly identified, and scattering on valence electrons is detected for the first time below 100$\,$eV. 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 0.5$\,$keV. The data are in better agreement with $ab$ $initio$ calculations originally developed for X-ray absorption spectroscopy.
Comment: 12 pages, 10 figures
Comment: 12 pages, 10 figures