Probing flavored regimes of leptogenesis with gravitational waves from cosmic strings

TL;DR

This paper demonstrates that gravitational wave spectra from cosmic strings can reveal different flavored regimes of high-scale leptogenesis, providing a novel observational test for leptogenesis models.

Contribution

It introduces a new method to test flavored leptogenesis regimes via gravitational wave spectral features from cosmic strings, without constraining flavor structures.

Findings

Distinct spectral features correspond to different flavored regimes.

Characteristic fall-offs in GW spectrum can identify flavor regimes.

Proposes GW detection as a probe for leptogenesis models.

Abstract

Cosmic strings radiate detectable gravitational waves in models featuring high-scale symmetry breaking, e.g., high-scale leptogenesis. In this Letter, for the first time, we show that different flavored regimes of high-scale leptogenesis can be tested with the spectral features in cosmic string-radiated gravitational waves. This is possible if the scalar field that makes right-handed neutrinos massive is feebly coupled to the Standard Model Higgs. Each flavored regime, sensitive to low-energy neutrino experiments, leaves a marked imprint on the gravitational waves spectrum. A three-flavor and a two-flavor regime could be probed by a characteristic fall-off of the gravitational wave spectrum at the LISA-DECIGO-ET frequency bands with preceding scale-invariant amplitudes bounded from above and below. We present Gravitational Waves windows for Flavored Regimes of Leptogenesis (GWFRL) testable in the upcoming experiments. We also provide the first construction of a leptogenesis framework where a testable distinction of flavor regimes is possible without constraining the flavor structure of the theory.