The PSI Theory Group of Particle Physics mainly works on projects related to particle physics at PSI and CERN in direct connection to the activities of 3202, 3203 and 3204. Particular emphasis is put on higher-order calculations and applications of effective field theory. These methods are applied to the physics at the energy frontier (such as Higgs bosons and other Standard Model processes as well as supersymmetry and other physics beyond the Standard Model) and the low-energy high-precision frontier (QED corrections to muon decays and scattering as well as lepton-flavour violating processes). This effort includes methods for the automatization of higher-order corrections. In addition, part of the theory group is involved in precision calculations for B-physics with particular emphasis on global fits and potential explanations of the B anomalies.
The activities of the theory group related to low-energy hadronic effects have been strengthened recently. With this strategic move, expertise in non-perturbative methods is now also present in the theory group. This allows to cover aspects such as electric dipole moments of the neutron as well as hadronic effects in the anomalous magnetic moment, muonic atoms, and lepton-proton scattering.