# Heavy neutrino searches at future $Z$-factories

## TL;DR

This paper evaluates the potential of future Z-factories to detect heavy neutrinos with masses between 10 and 85 GeV, providing bounds on production cross sections and mixing parameters through Monte Carlo simulations.

## Contribution

It introduces a detailed simulation-based analysis of heavy neutrino searches at future Z-factories, improving current constraints on neutrino mixing parameters.

## Key findings

- Upper bounds on production cross sections are established for various luminosities.
- Constraints on heavy neutrino mixing parameters are improved by at least an order of magnitude.
- The analysis covers a broad mass range from 10 to 85 GeV.

## Abstract

We analyze the capacity of future $Z$-factories to search for heavy neutrinos with their mass from 10 to 85 GeV. The heavy neutrinos $N$ are considered to be produced via the process $e^+e^-\to Z\to \nu N$ and to decay into an electron or muon and two jets. By means of Monte Carlo simulation of such signal events and the Standard Model background events, we obtain the upper bounds on the cross sections $\sigma(e^+e^-\to \nu N\to \nu\ell jj)$ given by the $Z$-factories with integrated luminosities of 0.1, 1 and 10 ab$^{-1}$ if no signal events are observed. Under the assumption of a minimal extension of the Standard Model in the neutrino sector, we also present the corresponding constraints on the mixing parameters of the heavy neutrinos with the Standard Model leptons, and find they are improved by at least one order compared to current experimental constraints.