Grant: Subatomic Physics Envelope - Project

The Helium and Lead Observatory (HALO) is a proposed supernova neutrino detector for SNOLAB. HALO is a long term, low cost, high livetime, and low maintenance, dedicated supernova detector. This grant request is for the capital funds to deploy an initial phase of HALO along with two years of operating funds and R&D funding for the design of a detector of at least 10 times the sensitivity of the initial phase. A type II supernova is powered by the energy liberated in the gravitational collapse of the core of a massive star. The core is transformed to a hot proto-neutron star that rapidly cools, by the emission of neutrinos, in some tens of seconds. In fact, about 99% of the energy is released in the form of ~ 10 MeV neutrinos. Direct measurement of the time evolution of the luminosity, flavour partition, and average neutrino energy are our best experimental window into the challenging field of supernova dynamics which would lead to an improved understanding of supernovae and of fundamental neutrino properties. The HALO detector takes advantage of the low cost, high neutrino cross-section and low neutron absorption cross-section of lead. Neutrino interactions in lead expel neutrons from the lead nuclei making a burst of detected neutrons the signature for the detection of a supernova. The concept for HALO is a volume of lead instrumented with neutron detectors. While other supernova detectors are primarily sensitive to electron antineutrinos HALO is sensitive to electron neutrinos through the charged current interaction and to all flavours through the neutral current interaction. These sensitivities ensure that supernova data from HALO would contribute to unravelling the supernova neutrino signal and extracting physics from the next galactic supernova. HALO benefits from having "on hand" 80 tonnes of lead, from the decommissioning of the Deep River Cosmic Ray Station, and approximately 600 meters of 3He neutron detectors from the final phase of the SNO experiment. These assets will be used to mount Phase I of HALO in SNOLAB.