The feeble interaction frontier of flavour physics

Informations projet

FlavourFIPs

N° de convention de subvention: 101028626

DOI

10.3030/101028626

Projet clôturé

Date de signature de la CE 31 Mars 2021

Date de début 1 Septembre 2021

Date de fin 31 Août 2023

Financé au titre de

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Coût total

€ 196 707,84

Contribution de l’UE

€ 196 707,84

Coordonné par

CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE CNRS
France

Periodic Reporting for period 1 - FlavourFIPs (The feeble interaction frontier of flavour physics)

Période du rapport: 2021-09-01 au 2023-08-31

Résumé du contexte et des objectifs généraux du projet

Despite all its successes, the shortcomings of the Standard Model of particle physics are well-known: for instance, the origin of its flavour structure remains a mystery, the absence of a dark matter candidate is puzzling, and more technical issues such as the strong CP problem remain. While many of the new physics models aiming at solving them rely on new particles around the TeV scale, this is neither a requirement nor the simplest solution in many cases. In fact, new light but Feebly Interacting Particles (FIPs) often represent the most straightforward solution, with deep implications for flavour physics, dark matter, astrophysics and cosmology. As particle physics enters a new era of “precision”, dozens of experiments, ranging from the High Luminosity LHC to neutrinos experiments, will have the potential to search for such particles.

The FlavourFIPs MSCA project explored the uncharted links between such versatile new physics candidates and the Standard Model flavour problem. The main research objectives have been to study the low-energy couplings of such new light particles, develop their possible impacts on current experimental challenges and anomalies, and finally explore the relationship between a theory of flavour at energies above the TeV and the new light particles.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

Along with several collaborators across Europe, the fellow explored both the theoretical and experimental aspects of postulating the existence of new light but flavourful particles.
In an important first step, it was shown that one of the most well-known light new physics candidates, the axion, could arise from ultraviolet model explaining the SM flavour structure, while solving simultaneously the main long-standing technical issues with axion: the so-called “quality problem”. Long-term theoretical work then followed on other light new particle candidates, eventually uncovering a distinct pattern of experimental flavour signatures called “flavour transfer processes” which arises naturally from new horizontal gauge symmetries linked to the fermions generation indices.

Exploring the experimental consequences of postulating the presence of new light particles constituted the second pillar of this project. The project led to the only complete theoretical explanation of the 4σ discrepancies between lattice and data-driven determinations of the hadronic vacuum polarization contribution to the muon anomalous magnetic moment. It showed that a new light vector particles interacting with muons and electrons could significantly reduce the numerous tensions in the current experimental datasets. Finally, an in-depth work on the electron-positrons couplings of light new particles led to designing a new type of experimental approaches based on resonant production. Demonstrated by an analysis currently under way by the PADME collaboration to confirm or infirm the new physics origin of the so-called X17 anomaly, this strategy will likely be an important part of future intensity frontier experimental searches.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

Overall, this Horizon 2020 project opened new avenues for research around the flavour problem in the Standard Model, bringing closer an answer to the question of the origin of the three copies of matter present in nature. It further provided clear paths in testing and assessing the possibility that several current experimental anomalies in particle physics could be linked to the presence of new light particles.

Extracted from 2307.09595. Projection of a resonant-search strategy in the PADME run-3 of Sept. 2023

Extracted from 2307.09595. Competition between LHC and flavour limits for flavour-transfer processes

Extracted from 2212.03877. Illustration of the improved agreement between (g-2)-related observables