Search for Heavy Right Handed Neutrinos at the FCC-ee

TL;DR

This paper explores the potential of the FCC-ee collider to detect heavy right-handed neutrinos, providing sensitivity estimates for their masses and mixing angles, which could significantly advance understanding of neutrino mass generation.

Contribution

It presents the first sensitivity analysis for heavy neutrino searches at the FCC-ee, including neutrino counting and decay-based detection methods.

Findings

Neutrino counting can achieve a precision of 0.001 to 0.0004.

Direct searches are promising due to heavy neutrino long lifetime.

Sensitivity to heavy-light mixing down to 10^{-12} for masses 10-80 GeV/c2.

Abstract

The Standard Model of particle physics is still lacking an understanding of the generation and nature of neutrino masses. A favorite theoretical scenario (the see-saw mechanism) is that both Dirac and Majorana mass terms are present, leading to the existence of heavy partners of the light neutrinos, presumably massive and nearly sterile. These heavy neutrinos can be searched for at high energy lepton colliders of very high luminosity, such as the Future electron-positron e+e- Circular Collider, FCC-ee (TLEP), presently studied within the Future Circular Collider design study at CERN, as a possible first step. A first look at sensitivities, both from neutrino counting and from direct search for heavy neutrino decay, are presented. The number of neutrinos should be measurable with a precision between 0.001 - 0.0004, while the direct search appears very promising due to the long lifetime of heavy neutrinos for small mixing angles. A sensitivity down to a heavy-light mixing of 10^{-12} is obtained, covering a large phase-space for heavy neutrino masses between 10 and 80 GeV/c2.