Mr Tevong You (King's College London)
Particle physics in the last century can be described as a series of effective theories, each predicting its own range of validity beyond which a more fundamental theory must take over. This program culminated in the Standard Model (SM), with all its constituent particles now experimentally established following the 2012 discovery of a Higgs boson. The SM is a renormalizable theory valid to arbitrarily high scales but there is evidence new degrees of freedom must exist. If this new physics is decoupled at higher energies, as suggested by null experimental searches so far, then the SM must also be considered as an effective field theory with higher-dimensional operators suppressed by a cut-off scale. The sensitivity to this scale is quantified by the effects of operator coefficients on Higgs physics, triple-gauge couplings, and electroweak precision tests. Limits on these Wilson coefficients can be translated to a particular UV theory by integrating out heavy particles. As an example we illustrate this for a stop in the MSSM using the path integral method to obtain the one-loop effective Lagrangian. A universality in the result facilitates matching to any other model.