In spite of its success, there are theoretical and observational reasons to think that the Standard Model (SM) of Particle Physics is part of a larger framework. Efforts at three basic frontiers are carried out to search for new phenomena, i.e. Beyond the Standard Model (BSM) effects. The Energy Frontier uses powerful colliders to discover heavy new particles, and it is currently led by the CERN Large Hadron Collider (LHC). The Intensity Frontier uses precision measurements to search for BSM physics through quantum effects. Last, the Cosmic Frontier uses the universe as a laboratory to search for new phenomena.
This action studies the synergy of the Energy and the Intensity Frontiers, with the focus on non-standard effects affecting light quarks (u,d,s) and any lepton flavour (e,μ,τ). The goal is follow a model-independent approach whose results can be easily applied to specific BSM scenarios. Such general approach is based on an Effective Field Theory (EFT) framework where the effects of heavy fields are parameterised by Wilson Coefficients that multiply high-dimensional operators.
The case of hadronic τ decays is particularly interesting, as it represents the only low-energy handle on non-standard duτν or suτν interactions. Inclusive decays have been the object of enormous experimental and theory efforts in the last decades, providing precise determinations of fundamental parameters such as the strong coupling constant. On the other hand, exclusive decays are also interesting BSM probes thanks to the impressive precision of Lattice QCD (LQCD) calculations. Although this makes these processes interesting BSM probes, they have received very little attention from this point of view. Finally, the interplay of these low-energy studies with direct searches at the LHC has not been studied either.
The Tau-SYNERGIES action proposes a model-independent study of current and future high-precision low-energy measurements. It includes also the study of the interplay with collider searches. The main research objectives are the following:
- An unprecedented model-independent analysis of hadronic tau decays including BSM effects, and their complementarity with LHC searches;
- A comprehensive EFT global fit of low-energy processes involving light quarks (u,d,s) and any lepton flavour (e,μ,τ).
These objectives were achieved during the realization of this action, and they were published through several scientific articles.
