Riding the Seesaw: What Higgsstrahlung May Reveal about Massive Neutrinos

TL;DR

This paper explores how future electron-positron colliders can indirectly detect massive neutrino models through precise measurements of the Higgsstrahlung process, comparing collider sensitivities to existing constraints.

Contribution

It assesses the potential of high-precision Higgsstrahlung measurements at future colliders to probe different Seesaw neutrino models, highlighting their sensitivity relative to current bounds.

Findings

Type-I Seesaw effects are highly constrained by existing data.

Type-III Seesaw can produce effects up to 10% in Higgsstrahlung cross section.

Future colliders could distinguish between Seesaw models based on these measurements.

Abstract

We investigate if the projected high-precision measurements of the cross section of the Higgsstrahlung process $e^+ e^- \to Zh$ at a future electron-positron collider can be utilised to indirectly probe the fermionic Seesaw models. We consider the two centre-of-mass energies $\sqrt{s}=240$ GeV and $365$ GeV, and compare the collider reaches to constraints from electroweak observables, probes of lepton flavour universality and the existing and prospective bounds from searches for lepton flavour violation. For the analysis we assume the limit of an exactly conserved lepton-number symmetry. We find that while any appreciable correction to the Higgsstrahlung cross section is already strictly constrained in the Type-I Seesaw model, effects of up to $\mathcal{O}(10\%)$ are possible within Type-III Seesaw.