Supernova relic neutrino detection with neutron tagging

When a massive star exhausts all sources of fuel, its existence ends in a core-collapse supernova explosion. This events involve all four forces of nature and, as yet, are not well understood. During the core-collapse, over 99% of the gravitational energy of the star is converted into neutrinos. To date, we have only detected one burst of supernova neutrinos, from SN1987a.

Since the neutrinos effectively travel forever, the universe should be filled with an isotropic signal of neutrinos from all of the core-collapse supernovae that have ever exploded. These neutrinos are known as "supernova relic neutrinos" (SRN) and have not yet been observed.

The primary SRN interaction is inverse beta decay, in which an electron antineutrino interacts with a free proton to produce a positron and a neutron.

The recent loading of gadolinium into the Super-Kamiokande water Cherenkov detector allows the neutron to be detected, in addition to the positron signal.

This coincidence tagging is a powerful tool for removing the previously irreducible backgrounds that have prevented SRN detection.

During his PhD, the student will work as a member of the Super-Kamiokande collaboration to make a first detection of the SRN.

This is the first step towards collecting a high-statistics sample, which can then be used to determine the supernova history of the universe.