Electroweak Phase Transition and Gravitational Waves in the Type-II Seesaw Model

TL;DR

This paper investigates the electroweak phase transition and gravitational wave signals in the type-II seesaw model, highlighting conditions for strong first-order transitions and potential detectability by future gravitational wave observatories.

Contribution

It provides a detailed analysis of phase transition patterns and gravitational wave production specific to the type-II seesaw model, identifying key parameter regions for observable signals.

Findings

Strong first-order phase transition prefers positive Higgs portal couplings.

Light triplet mass below approximately 550 GeV enhances transition strength.

Generated gravitational waves could be detectable by future observatories like Ultimate-DECIGO.

Abstract

The type-II seesaw model is a possible candidate for simultaneously explaining non-vanishing neutrino masses and the observed baryon asymmetry of the Universe. In this work, we study in detail the pattern of phase transition and the gravitational wave production of this model. We find a strong first-order electroweak phase transition generically prefers positive Higgs portal couplings and a light triplet below $\sim550$ GeV. In addition, we find the gravitational wave yield generated during the phase transition would be at the edge of BBO sensitivity and could be further examined by Ultimate-DECIGO.