Collaborative Research: NSF-BSF: Continuation of the XENON Program at LNGS

Identifying the nature of dark matter remains one of the most pressing problems in physics today. The direct search for dark matter particles with the XENON family of experiments using liquid xenon time projection chambers (LXeTPCs) of increasing target mass and decreasing background has led to the most stringent constraints on many different dark matter candidates, over a broad range of mass, type of coupling, cross-section, and particle type. Building on the success of the first multi-tonne LXeTPC, XENON1T, this collaboration has expanded the scientific reach of this technology by building a new LXeTPC, XENONnT, of larger target mass and with lower intrinsic background but re-using infrastructure and already tested systems.

Liquid xenon detector technologies are unique training grounds for undergraduate and graduate students, and postdoctoral scientists, in that they combine significant hardware involvement with advanced data analysis skills. Technologies span from sophisticated detector design to cyber-infrastructure and innovative data analysis, with applications in other fields such as medical imaging and nuclear nonproliferation. The entire project employs an open data policy to foster benefits in other areas of research and education. the participating groups facilitate and encourage public interest in science through targeted talks and outreach activities with particular focus to support members of underrepresented and underserved groups.

The XENONnT experiment, with its multi-tonnes fiducial mass and ultra-low background will reach a sensitivity to various dark matter models more than an order of magnitude beyond current knowledge. XENONnT will be sensitive to a variety of interactions, including spin-independent, spin-dependent, and other couplings; to a variety of particles, including WIMPs, axion-like particles, solar axions and dark photons; and at the same time, XENONnT will cover particle masses ranging from kilo-electronvolts almost up to the Planck mass. It will also be an observatory for other highly interesting physics. Examples in neutrino physics include a measurement of the Solar neutrino luminosity through pp neutrinos and a first measurement of the Solar metallicity through boron-8 neutrinos. The detector might also observe neutrinos from a Galactic supernova and potentially issue early multi-messenger alerts to telescopes.

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.