  Recent developments in the field of liquid scintillator chemistry and
fast-timing photosensors paved the way for a new generation of large-scale
detectors capable of tackling a broad range of physics issues. Water-based
Liquid Scintillator is a novel detection medium that combines the advantages of
pure water, including low attenuation, accurate direction reconstruction, and
low cost, and those of liquid scintillator, including high light yield and
low-threshold detection. When coupled with high efficiency, fast-timing
photosensors, such as Large Area Picosecond PhotoDetectors, Water-based Liquid
Scintillator exhibits an immense potential for neutrino physics and BSM
searches. Theia is a 50-kiloton multi-purpose neutrino detector that aims to
jointly deploy these two technologies in order to fulfill its physics program
objectives, including the determination of the neutrino mass hierarchy and the
CP violation phase in the leptonic sector, the detection of solar, reactor, and
supernova neutrinos, and the search for neutrinoless double beta decay and
proton decay.
