Probing Leptogenesis at Future Colliders

TL;DR

This paper explores the potential of future colliders to test leptogenesis, focusing on heavy neutrinos in the 5-50 GeV range, and assesses how collider measurements could confirm the mechanism behind the universe's matter-antimatter asymmetry.

Contribution

It identifies the parameter space for successful leptogenesis with two right-handed neutrinos and evaluates collider prospects for detecting and measuring heavy neutrinos to test leptogenesis.

Findings

Future colliders can detect heavy neutrinos via displaced vertices.

Precision measurements of active-sterile mixing angles are feasible.

Collider data can potentially confirm the minimal seesaw mechanism as the origin of neutrino masses.

Abstract

We investigate the question whether leptogenesis, as a mechanism for explaining the baryon asymmetry of the universe, can be tested at future colliders. Focusing on the minimal scenario of two right-handed neutrinos, we identify the allowed parameter space for successful leptogenesis in the heavy neutrino mass range between $5$ and $50$ GeV. Our calculation includes the lepton flavour violating contribution from heavy neutrino oscillations as well as the lepton number violating contribution from Higgs decays to the baryon asymmetry of the universe. We confront this parameter space region with the discovery potential for heavy neutrinos at future lepton colliders, which can be very sensitive in this mass range via displaced vertex searches. Beyond the discovery of heavy neutrinos, we study the precision at which the flavour-dependent active-sterile mixing angles can be measured. The measurement of these mixing angles at future colliders can test whether a minimal type I seesaw mechanism is the origin of the light neutrino masses, and it can be a first step towards probing leptogenesis as the mechanism of baryogenesis. We discuss how a stronger test could be achieved with an additional measurement of the heavy neutrino mass difference.