Displaced vertex searches for sterile neutrinos at future lepton colliders

TL;DR

This paper evaluates the potential of future lepton colliders like FCC-ee, CEPC, and ILC to detect sterile neutrinos via displaced vertices, highlighting their sensitivity to very small active-sterile mixing angles.

Contribution

It provides a detailed sensitivity analysis for detecting long-lived sterile neutrinos at future lepton colliders using displaced vertex signatures.

Findings

Displaced vertices are a highly sensitive channel for sterile neutrino detection.

Future colliders can probe active-sterile mixing angles as small as 10^{-11}.

The ILC's SiD detector effectively identifies displaced vertex signals.

Abstract

We investigate the sensitivity of future lepton colliders to displaced vertices from the decays of long-lived heavy (almost sterile) neutrinos with electroweak scale masses and detectable time of flight. As future lepton colliders we consider the FCC-ee, the CEPC, and the ILC, searching at the Z-pole and at the center-of-mass energies of 240, 350 and 500 GeV. For a realistic discussion of the detector response to the displaced vertex signal and the Standard Model background we consider the ILC's Silicon Detector (SiD) as benchmark for the future lepton collider detectors. We find that displaced vertices constitute a powerful search channel for sterile neutrinos, sensitive to squared active-sterile mixing angles as small as $10^{-11}$.