Particle and Gravitational Wave Probes of Minimal Seesaw Neutrinos

Abstract

Observable gravitational waves (GWs) from first-order phase transitions (FOPTs) can coexist with distinct particle physics signatures. These include same-sign dilepton plus four~jet events at colliders, such as $e^+ e^-/μ^+μ^- \to \ell^\pm \ell^\pm 4j$, neutrinoless double beta decay, as well as charged lepton flavor violating (cLFV) processes such as $μ\to e γ$. We explore this synergy within the minimal low-scale linear seesaw model. This framework successfully reproduces neutrino oscillation data, providing a direct avenue to probe the neutrino mass ordering and Majorana nature at colliders. Crucially, the FOPT responsible for the GW background is driven by a leptophilic Higgs doublet, establishing a direct link between early-universe cosmology and terrestrial laboratory experiments.