Detecting Low-Energy Astrophysical Neutrinos with KM3NeT/ORCA: the Transient Neutrino Sky at the GeV Scale

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"The era of Multi-Messenger (MM) astronomy has started with the joint observations of gravitational and electromagnetic waves in August 2017, and the announcement of a common source of high-energy neutrinos and gamma rays in July 2018. The ""Low-Energy Astrophysical Neutrinos in ORca"" (LEANOR) project aspires to be the next MM observation, coupling low-energy (GeV) neutrinos with electromagnetic and gravitational waves emitted during short gamma-ray bursts (SGRBs). While the signal/background differentiation is more challenging for low energy neutrinos, they have the advantage to be more abundant than their high-energy counterpart. Produced as a consequence of the accelerated proton flux colliding with the matter surrounding the source, they stand as promising messengers to constrain the local environment and would furthermore be of great help to identify new cosmic sources. To reach this goal, we propose to convert the KM3NeT-ORCA detector, initially designed for neutrino oscillation studies, into a telescope able to study astrophysical GeV neutrinos. A detailed study of the environmental noise will be coupled to a specific selection of ORCA data targeting GeV neutrino interactions. The data sample acquired will then be used to search for statistically significant excess of neutrinos during SGRBs. Three different analyses, based on electromagnetic or gravitational wave observations, will be developed. These analyses will allow to constrain the source environment as well as the hadronic acceleration process taking place in SGRBs. The project will lead to either the first joint observation of GeV neutrinos, electromagnetic and gravitational waves, or the first observational limits set in this energy range for the studied source population. Opening a new line of research in ORCA, LEANOR will also provide the KM3NeT collaboration with new tools to develop a variety of searches for low energy neutrinos emitted during transient events, such as Novae or Fast radio bursts."