Standard Model with hidden scale invariance and light dilaton

Understand

We consider the minimal Standard Model as an effective low-energy description of an unspecified fundamental theory with spontaneously broken conformal symmetry.

• The effective theory exhibits classical scale invariance which manifest itself through the dilaton field.
• The mass of the dilaton is generated via the quantum scale anomaly at two-loop level and is proportional to the techically stable hierarchy between the electroweak scale and a high energy scale given by a dilaton vacuum expectation value.
• We find that a generic prediction of this class of models is the existence of a very light dilaton with mass between $\sim 0.01$ $\mu$eV to $\sim 100$ MeV, depending on the hierarchy of scales.