PheNUmenal · Phenomenological implications of neutrino effective theories

Phenomenological implications of neutrino effective theories

Particle Physics is the branch of Physics that studies the fundamental components of our Universe—what they are and how they behave. In essence, it seeks to explain what the Universe is made of. Theoretical physics has developed the Standard Model of Particle Physics (SM), one of the most successful theories in Physics. However, the SM fails to account for certain experimental observations, such as those related to neutrino masses or the nature of dark matter in the Universe. Addressing these mysteries is the current driving force in particle physics. Today, there is a multitude of new theories proposed to extend the SM into a more comprehensive framework capable of explaining these unresolved questions. This variety of theories is collectively referred to as Beyond the Standard Model (BSM) theories, and they often predict the existence of new particles or phenomena. Discovering these would be our best opportunity to validate which BSM theory accurately describes nature. Unfortunately, no current experiments have detected any new signals from these BSM theories, which in turn sets strong constraints on their viability. The growing number of BSM proposals aimed at addressing these open questions, combined with the lack of new particle discoveries at the LHC, is motivating the use of effective field theories (EFTs) to explore new scenarios. This framework is appealing as it allows the exploration of multiple BSM theories simultaneously. However, this highly active field often overlooks the existence of new light particles, such as sterile neutrinos, which are predicted by many theories that attempt to explain the origin of neutrino masses—one of the most compelling indicators of new physics. As a result, the most widely used EFT extension of the SM, the SMEFT, cannot accommodate several well-motivated BSM scenarios. In this context, the overarching aim of PheNUmenal was to develop a new framework incorporating sterile neutrinos within the EFT formalism and to identify and classify its most significant experimental implications.

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