FlavourFIPs · The feeble interaction frontier of flavour physics

Despite all its successes, the shortcomings of the Standard Model of particle physics are well-known: for instance the origin of its flavour structure, the absence of a dark matter candidate, or the strong CP problem. 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. FlavourFIPs aims at exploring the uncharted links between such versatile new physics candidates and the Standard Model flavour problem. The applicant will develop novel cutting-edge theoretical tools to study the GeV-scale phenomenology of FIPs, including in particular a unified effective field theory description of new flavoured light particles at this scale. Postulating the existence of a UV-theory designed to solve the flavour problem, FlavourFIPs will then reshape the FIPs parameter space for current and upcoming intensity frontier experiments. In particular, the project will explore how a long-lived FIP could be produced via flavour-violating processes then detected in neutrinos or dedicated LHC-based detectors. Closing the loop, FlavourFIPs will finally investigate if FIPs can participate in creating the flavour anomalies potentially observed in B-mesons decays, and beyond, investigate FIPs role in complete theories of flavour.Throughout the fellowship, the dissemination activities will reinforce the position of Europe in the intensity frontier international community and will participate in shaping the future experimental landscape, in particular for future HL-LHC-based experiments.