Dilaton Interactions and the Anomalous Breaking of Scale Invariance of the Standard Model

TL;DR

This paper explores the interactions of dilatons within the Standard Model, emphasizing the role of conformal anomalies in their couplings and decay processes, including radiative corrections and the effects of conformal coupling of the Higgs.

Contribution

It provides a detailed analysis of dilaton interactions, especially the impact of conformal anomalies and the conditions for renormalization in the Standard Model with dilatons.

Findings

Dilatons can significantly enhance decay rates into photons and gluons due to trace anomaly coupling.

Renormalization in the electroweak sector requires the Higgs to be conformally coupled.

Radiative corrections to dilaton decay channels are explicitly computed and analyzed.

Abstract

We discuss the main features of dilaton interactions for fundamental and effective dilaton fields. In particular, we elaborate on the various ways in which dilatons can couple to the Standard Model and on the role played by the conformal anomaly as a way to characterize their interactions. In the case of a dilaton derived from a metric compactification (graviscalar), we present the structure of the radiative corrections to its decay into two photons, a photon and a $Z$, two $Z$ gauge bosons and two gluons, together with their renormalization properties. We prove that, in the electroweak sector, the renormalization of the theory is guaranteed only if the Higgs is conformally coupled. For such a dilaton, its coupling to the trace anomaly is quite general, and determines, for instance, an enhancement of its decay rates into two photons and two gluons. We then turn our attention to theories containing a non-gravitational (effective) dilaton, which, in our perturbative analysis, manifests as a pseudo-Nambu Goldstone mode of the dilatation current ($J_D$). The infrared coupling of such a state to the two-photons and to the two-gluons sector, and the corresponding anomaly enhancements of its decay rates in these channels, is critically analyzed.