Grant: Subatomic Physics Envelope - Project

A type II supernova is powered by the energy liberated in the gravitational collapse of the core of a massive star. Post core collapse, the initially very hot proto-neutron star cools primarily by the emission of neutrinos, of all flavours, roughly equally partitioned. In fact, about 99% of the initial gravitational potential energy is released in a short burst of ~10 MeV neutrinos over a few tens of seconds. The measurement of the time evolution of the neutrino luminosity, flavour partition, and average energy is a direct window into supernova dynamics though a gravitational wave is also anticipated. The nuclear physics of lead, as a target material for the supernova neutrinos, provides for a dominant sensitivity to charged current (CC) interactions of the electron neutrino flux; complete insensitivity to CC interactions of the electron antineutrino flux; and minor sensitivity to all neutrino flavours through neutral current excitation channels. A detailed understanding of supernova dynamics is at the forefront of large-scale computational physics efforts and, when combined with observational data, offers the possibility of extracting fundamental neutrino properties as well as advancing our understanding of the supernova mechanism, heavy element nucleosynthesis, and other astrophysical questions. HALO-1kT is a proposed lead-based supernova neutrino detector to be constructed at the Laboratori Nazionali del Gran Sasso (LNGS) in Italy. It is an evolution of the successful, but smaller, HALO detector at SNOLAB. HALO-1kT is expected to outperform HALO by a factor of 25 in sensitivity. The scientific collaboration is Canadian-led with major participation by Italian and American groups. This SAP Project grant application is for stable and adequate funding for the Canadian group through the finalization of the full Experimental Proposal; the application for capital funding through CFI; and studies and preparations for experiment deployment. HALO-1kT is timely and possible due to the experience gained in the construction and operation of HALO at SNOLAB; the availability of 1000 tonnes of lead from the OPERA experiment and the enthusiasm at LNGS to re-invigorate their supernova detection capabilities; and the end of the American moratorium on the distribution of He-3 and its availability once again through the DOE Isotope Program. Neither HALO nor HALO-1kT can be claimed to be fully understood and calibrated until the neutrino-lead cross sections are known at supernova-relevant energies. A component of the funds requested here will support a measurement of these cross sections at Oak Ridge National Laboratory's Spallation Neutron Source. However, the bulk of the support for the cross section measurement is coming from a combination of the McDonald Institute (MI), Laurentian University, INFN, University of Washington, LNGS, and SNOLAB and a CFI-JELF submission in preparation.