Final Report Summary - EFT4LHC (An Effective Field-Theory Assault on the Zeptometer Scale: Exploring the Origins of Flavour and Electroweak Symmetry Breaking) Questions about the origins of electroweak symmetry breaking and of the striking hierarchies observed in the spectrum of fermion masses and mixing angles are among the most pressing problems in fundamental physics. While the Large Hadron Collider at CERN was built to explore the physics of electroweak symmetry breaking on tiny distance scales of an attometer, the absence of clear hints for new particles in existing high-energy physics experiments suggests that new phenomena might only occur at distances still smaller than this. We have shown that significantly shorter distances of only a few zeptometer (10-21 m) can be probed in precision measurements of rare weak decay processes and of the couplings of the Higgs boson. We have developed a broad theoretical approach to precision physics in and beyond the Standard Model based on effective field-theory tools. In the context of warped extra-dimension models, the genuine quantum structure of fundamental physics has been probed in loop-mediated processes, including Higgs-boson production and decay as well as rare flavor-changing neutral current processes. These explorations have been complemented by high-precision calculations of important collider-physics processes, such as Higgs, top, and electroweak gauge-boson production in association with jets. The multi-loop anomalous dimensions required for these calculations offer a deeper understanding of the structure of infrared singularities of scattering amplitudes in non-abelian gauge theories. The results obtained from this research have helped to reveal the deep common origins of flavor and electroweak symmetry breaking.
