Measuring the Lightest Neutrino Mass with synergies between the Euclid Space Telescope and the Planck Satellite

This project addresses the pivotal scientific question of determining the mass of the lightest neutrino, a mystery central to both particle physics and cosmology.

The complex nature of neutrinos, particularly their subtle influence on the large-scale structure of the Universe, demands a multidisciplinary approach that combines extensive cosmological observations with constraints from particle physics experiments.

In this project, I will leverage data from the newly launched ESA´s Euclid Space Telescope, which began its main survey in 2024, along with Cosmic Microwave Background data from the Planck Satellite.

This combination of datasets exploits the perfect overlap of these missions by using cross-correlations between Euclid and Planck observables to understand the effects of massive neutrinos across different cosmic epochs.

Euclid´s detailed survey, capturing billions of galaxies using advanced photometry and spectroscopy, is uniquely positioned to observe the imprint of neutrinos for over 10 billion years in cosmic history in a large fraction of the sky.

At the same time, Planck´s measurements offer critical insights into how neutrinos affected the early Universe while still behaving as relativistic particles.

My research methodology employs two distinct analysis techniques to enhance the precision and reliability of our findings.

The first technique involves a robust two-point (2pt) summary statistics approach, which has been proven effective in earlier cosmological surveys and serves as a reliable method for initial analyses.

It synergistically combines Euclid´s spectroscopic and photometric galaxy clustering and weak lensing measurements with Planck´s CMB observables, such as the Integrated Sachs-Wolfe effect, thermal Sunyaev-Zeldovich, and CMB lensing.

Complementarily, I explore the potential of Field-Level Inference (FLI), a more sophisticated method that uses Bayesian Hierarchical Models to directly analyse full-sky cosmological fields from partial observations.

This approach is designed to enhance the precision of cosmological measurements and the lightest neutrino mass while managing the complex nature of the data involved.This project´s strategic, multidisciplinary nature aims to provide unprecedented insights into neutrinos, focusing on the lightest neutrino mass.

Discovering a massless neutrino could radically transform our understanding of particle physics and cosmology, hinting that neutrinos might be Majorana particles and suggesting a potential link to dark matter as a heavy right-handed neutrino.

Conversely, detecting a non-zero mass for the lightest neutrino could equally revolutionise the standard model of particle physics, allowing us to understand better what lies beyond the Standard Model of Particle Physics.

These findings could pave the way for new theories and models in both Cosmology and Particle Physics, significantly impacting our understanding of the Universe´s fundamental constituents.