RELiCS - Revealing Elusive LIght particles with Cosmic microwave background surveys across cosmological Scales

Neutrinos and other well-motivated particles from the Big Bang are gateways to much awaited new physics that will sharpen our understanding of Nature. Cosmology offers a unique arena to unveil their secrets in a way that is separate from, but complementary to astrophysical and terrestrial searches. The next generation of cosmological surveys will supersede the current, which is already highly sensitive to these particles’ fundamental properties. The first-ever measurement of the neutrino mass scale, a handle to its beyond-standard-model origin, has never been so close. A novel approach to data exploitation is both necessary and timely. Perfect command of theoretical predictions of key observables and instrument knowledge must inform each other. A robust inference framework is required to compare and combine the wide datasets soon to be available. Without this interconnected analysis pipeline, the richness and complexity of new data will spoil detection prospects. RELiCS is the project to lead new Cosmic Microwave Background (CMB) experiments towards discoveries in particle physics. I propose a program built around my expertise in particle cosmology and CMB data analysis that will deliver new and robust limits on neutrino and light relics properties. The flagship experiment is the ground-based Simons Observatory, for which I already lead key parts of the analysis. RELiCS is timely: the analysis pipeline will be immediately applied to fresh data from 2024. The same pipeline will shape the analysis strategies of the two ultimate CMB experiments, of which I am a key member of: the ground-based CMB-S4, and the space-borne mission LiteBIRD. My expertise is unique in that embraces understanding of the theory, instrument, data analysis and high-level science exploitation. Through RELiCS, I will lead work that will crucially support cosmology towards first discoveries in the neutrino and light relics sector and pave the way to robust exploitation of ultimate surveys.

Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or European Research Council Executive Agency (ERCEA). Neither the European Union nor the granting authority can be held responsible for them