The quantum criticality of the Standard Model and the hierarchy problem

Abstract: The naturalness principle has long guided efforts to understand what lies beyond the Standard Model of particle physics, with the hierarchy problem being a prominent example. In this work, we revisit the impact of quantum corrections on the fine-tuning of the low-energy effective theory and its phase structure. For this purpose, we employ the Wilsonian functional renormalization group which conveniently captures both, logarithmic and polynomial, scalings in dimensionful parameters along the flow and allows for an interpretation in terms of critical phenomena. Within this framework, we show that crucial and scheme-independent information about the infrared Higgs phases and the associated quantum phase transition can be directly extracted. We build on the connection between the hierarchy problem and the near-criticality of the Standard Model, identifying a particularly enhanced tuning, and perform a comprehensive and model-independent analysis of the sensitivity to heavy new physics. Finally, we illustrate the versatility of this framework by performing a simplified search for new physics coupled to the Higgs sector which can soften the sensitivity to high-energy scales, rediscovering also the large-anomalous-dimension solution to the hierarchy problem.