Classically Scale-invariant B-L Model and Dilaton Gravity

TL;DR

This paper explores a classically scale-invariant B-L extended standard model coupled with dilaton gravity, showing B-L symmetry breaking occurs spontaneously at tree level, leading to a massive B-L gauge field without relying on the Coleman-Weinberg mechanism.

Contribution

It demonstrates that B-L symmetry can break spontaneously at tree level in a scale-invariant model coupled with dilaton gravity, bypassing the Coleman-Weinberg mechanism.

Findings

B-L gauge symmetry breaks spontaneously at tree level.

The B-L gauge field acquires mass via the Higgs mechanism.

Small coupling constants are required for TeV scale symmetry breaking.

Abstract

We consider a coupling of dilaton gravity to the classically scale-invariant B-L extended standard model which has been recently proposed as a phenomenologically viable model realizing the Coleman-Weinberg mechanism of breakdown of the electroweak symmetry. It is shown in the present model that without recourse to the Coleman-Weinberg mechanism, the B-L gauge symmetry is broken in the process of spontaneous symmetry breakdown of scale invariance at the tree level and as a result the B-L gauge field becomes massive via the Higgs mechanism. Since the dimensionful parameter is only the Planck mass in our model, one is forced to pick up very small coupling constants if one wishes to realize the breaking of the B-L symmetry at TeV scale.