Synergy between measurements of the gravitational wave and the triple Higgs coupling in probing first order phase transition

TL;DR

This paper explores how measurements of gravitational waves and the triple Higgs coupling at future colliders can jointly probe the nature of the electroweak phase transition, especially its first order type, in models with additional scalar fields.

Contribution

It demonstrates the complementary roles of gravitational wave observations and collider measurements in testing the electroweak phase transition in extended Higgs models.

Findings

Gravitational wave signals can indicate a strongly first order phase transition.

Triple Higgs coupling measurements can constrain the Higgs potential.

Combined methods improve model discrimination.

Abstract

Probing the Higgs potential and new physics behind the electroweak symmetry breaking is one of the most important issues of particle physics. In particular, nature of electroweak phase transition is essential for understanding physics at the early Universe, such that the strongly first order phase transition is required for a successful scenario of electroweak baryogenesis. The strongly first order phase transition is expected to be tested by precisely measuring the triple Higgs boson coupling at future colliders like the International Linear Collider. It can also be explored via the spectrum of stochastic gravitational waves to be measured at future space-based interferometers such as eLISA and DECIGO. We discuss complementarity of both the methods in testing the strongly first order phase transition of the electroweak symmetry in models with additional isospin singlet scalar fields with and without classical scale invariance. We find that they are synergetic in identifying specific models of electroweak symmetry breaking in more details.