Discriminative phenomenological features of scale invariant models for electroweak symmetry breaking

TL;DR

This paper explores scale-invariant models for electroweak symmetry breaking, highlighting their unique phenomenological features and making testable predictions for collider experiments, especially regarding additional scalar masses and Higgs couplings.

Contribution

It identifies discriminative phenomenological features of scale-invariant models, including bounds on scalar masses and deviations in Higgs couplings, providing clear experimental tests.

Findings

Upper bound of ~543 GeV on lightest additional scalar mass

Prediction of enhanced Higgs-photon-photon coupling based on charged scalars

Universal ~+70% deviation in triple Higgs coupling from SM

Abstract

Classical scale invariance (CSI) may be one of the solutions for the hierarchy problem. Realistic models for electroweak symmetry breaking based on CSI require extended scalar sectors without mass terms, and the electroweak symmetry is broken dynamically at the quantum level by the Coleman-Weinberg mechanism. We discuss discriminative features of these models. First, using the experimental value of the mass of the discovered Higgs boson $h(125)$, we obtain an upper bound on the mass of the lightest additional scalar boson (~543 GeV), which does not depend on its isospin and hypercharge. Second, a discriminative prediction on the Higgs-photon-photon coupling is given as a function of the number of charged scalar bosons, by which we can narrow down possible models using current and future data for the di-photon decay of $h(125)$. Finally, for the triple Higgs boson coupling a large deviation (~ +70 %) from the SM prediction is universally predicted, which is independent of masses, quantum numbers and even the number of additional scalars. These models based on CSI can be well tested at LHC Run II and at future lepton colliders.