Gravitational wave signals from leptoquark-induced first order electroweak phase transitions

TL;DR

This paper explores how scalar leptoquarks can induce first order electroweak phase transitions, producing gravitational waves detectable by current or future observatories, and distinguishes leptoquark representations via these signals.

Contribution

It demonstrates that scalar leptoquarks can trigger first order EWPTs and predicts gravitational wave signatures that depend on their $SU(2)$ representations and Higgs portal couplings.

Findings

Leptoquark-Higgs coupling thresholds for first order EWPT

Gravitational wave signals within detector sensitivities

Differentiation of leptoquark representations by gravitational wave profiles

Abstract

We consider the extension of the Standard Model (SM) with scalar leptoquarks in $SU(2)$ singlet, doublet and triplet representations. Through the coupling between leptoquark and the SM Higgs field, the electroweak phase transition (EWPT) can turn into first order and consequently produce gravitational wave signals. We compute the required value of the leptoquark-Higgs for first order EWPT to happen and discuss about the possible constraint from Higgs phenomenology. Choosing some benchmarks, we present the strength of the gravitational waves produced during the leptoquark-induced first order EWPT and compare them to detector sensitivities. We find that the $SU(2)$ representations of the leptoquark can be distinguished by gravitational waves in the parameter space where first order EWPT can happen as a function of the Higgs portal coupling.