Electroweak and Strong Interactions at very High Energies: Precision Tests of the Standard Model and Beyond

Today, the Standard Model (SM) of particle physics provides a thoroughly tested framework for describing electromagnetic, weak and strong interactions of the fundamental constituents of matter. The SM successfully describes all presently observed electroweak and strong interactions of matter particles (quarks and leptons) and of the mediators of the fundamental forces (photon, W and Z bosons, and the gluon). However, due to apparent shortcomings of the SM (e.g., hierarchy problem, fine tuning, absence of gauge-coupling unification at high energies), it is commonly believed that it is merely the low-energy limit of a more fundamental theory, which has additional symmetries such as Supersymmetry (SUSY), an additional symmetry that connects fermions and bosons or which has extra spatial dimensions. The main goal of present and future collider experiments is to further test the SM and to detect signals of new physics, either directly (through the production of non-SM particles), or indirectly (as small deviations from the predicted properties of SM particles). The PIs propose to investigate possible deviations from the SM in the interactions of top quarks and Higgs bosons, and to develop improved theoretical calculations and computational tools which are needed to perform precision studies of SM and SUSY particles at the Fermilab Tevatron, the CERN Large Hadron collider (LHC), and a future International e+e− Linear Collider (ILC). In order to extract precise physics information from these experiments, theoretical predictions must match or exceed the experimental accuracy. In light of the anticipated experimental accuracy, current predictions must be improved. This will involve first the calculation of radiative corrections and then their implementation in Monte Carlo event generators for realistic simulations. The broader impact of the proposed activities is that the research will contribute to an improved understanding of the properties of elementary particles and their interactions. The tools developed will be made publicly available and will help the experimental high-energy physics community to fully exploit the potential of present and future collider experiments for testing the SM and searching for signals of new physics. This project will provide an excellent training ground for students at both the undergraduate and graduate level, teaching them skills valuable beyond the scope of particle physics research. The proposed activities will be pursued in collaboration with scientists worldwide, partly in context of the American Linear Collider Physics Group, and will further US-international joint scientific efforts.