“Neutrino Physics with an Opaque Detector”

In 1956 Reines & Cowan discovered the neutrino using a liquid scintillator detector. Theneutrinos interacted with the scintillator, producing light that propagated across transparentvolumes to surrounding photo-sensors. This approach has remained one of the most wide-spread and successful neutrino detection technologies used since. This article introduces aconcept that breaks with the conventional paradigm of transparency by confining and col-lecting light near its creation point with an opaque scintillator and a dense array of opticalfibres. This technique, called LiquidO, can provide high-resolution imaging to enable efficientidentification of individual particles event-by-event. A natural affinity for adding dopants athigh concentrations is provided by the use of an opaque medium. With these and othercapabilities, the potential of our detector concept to unlock opportunities in neutrino physicsis presented here, alongside the results of thefirst experimental validation.