Standard Model with spontaneously broken quantum scale invariance

TL;DR

This paper investigates a quantum scale symmetry in the Standard Model, demonstrating that the Higgs mass can be protected by spontaneous breaking of scale invariance, with quantum corrections computed in a scale-invariant framework.

Contribution

It introduces a scale-invariant extension of the Standard Model with non-polynomial operators and shows quantum corrections preserve scale invariance with a dynamically generated scale.

Findings

Quantum corrections preserve scale invariance at one-loop.

Higgs mass remains protected by spontaneous scale symmetry.

Non-polynomial operators have computable beta functions.

Abstract

We explore the possibility that scale symmetry is a quantum symmetry that is broken only spontaneously and apply this idea to the Standard Model (SM). We compute the quantum corrections to the potential of the higgs field ($\phi$) in the classically scale invariant version of the SM ($m_\phi=0$ at tree level) extended by the dilaton ($\sigma$). The tree-level potential of $\phi$ and $\sigma$, dictated by scale invariance, may contain non-polynomial effective operators, e.g. $\phi^6/\sigma^2$, $\phi^8/\sigma^4$, $\phi^{10}/\sigma^6$, etc. The one-loop scalar potential is scale invariant, since the loop calculations manifestly preserve the scale symmetry, with the DR subtraction scale $\mu$ generated spontaneously by the dilaton vev $\mu\sim\langle\sigma\rangle$. The Callan-Symanzik equation of the potential is verified in the presence of the gauge, Yukawa and the non-polynomial operators. The couplings of the non-polynomial operators have non-zero beta functions that we can actually compute from the quantum potential. At the quantum level the higgs mass is protected by spontaneously broken scale symmetry, even though the theory is non-renormalizable. We compare the one-loop potential to its counterpart computed in the "traditional" DR scheme that breaks scale symmetry explicitly ($\mu=$constant) in the presence at the tree level of the non-polynomial operators.