Calibration of Scintillating Bubble Chambers for Dark Matter and CEVNS Detection

The noble-liquid bubble chamber is a newly developed technology with a unique combination of high sensitivity to particle interactions with atomic nuclei, but extremely low sensitivity to interactions with atomic electrons. The Scintillating Bubble Chamber (SBC) Collaboration will develop this technique and use it in the study of dark matter and neutrinos. While astrophysical observations indicate that most of the matter in the universe is so-called ‘dark matter’, very little is known about the nature of dark matter. The SBC technique is complementary to many other experimental efforts also seeking to directly observe dark matter and would be an especially powerful experimental tool if it turns out that dark matter consists of particles of similar mass to protons – which make up most of the ‘normal matter’ in the universe. This project involves operation support, data analysis and calibration by graduate and undergraduate students at Drexel University of SBC noble-liquid bubble chambers for the low-background detection of sub-keV nuclear recoils. As a neutrino experiment, SBC’s unique capabilities enable the study of elastic scattering of neutrinos off atomic nuclei to reveal new insights. If successfully developed, this technology will enable searches for GeV-scale dark matter particles to the solar neutrino floor, and precision measurements of neutrino properties via coherent elastic scattering (CEvNS) of reactor neutrinos. The SBC Collaboration is commissioning a 10-kg liquid argon bubble chamber at Fermilab to calibrate the low-threshold reach of this technology. The unique sensitivity to sub-keV nuclear recoils motivates a novel in-situ calibration approach combining photoneutron sources to induce keV-scale nuclear recoils and an entirely new calibration technique employing elastic scattering of gamma rays to induce sub-keV nuclear recoils. Monte Carlo simulations and data analysis tools developed with this project will be used to interpret the response of the detector to the calibration sources and develop a precision data-driven response model to dark matter particles and neutrinos, enabling the physics goals of the SBC experimental program. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.