First Evaluation of Meson and $\tau$ lepton Spectra and Search for Heavy Neutral Leptons at ILC Beam Dump

TL;DR

This paper evaluates the potential of the ILC beam dump experiment to search for heavy neutral leptons by simulating meson and tau spectra, and compares its sensitivity with other methods.

Contribution

It introduces a novel evaluation of the ILC beam dump's sensitivity to heavy neutral leptons, including production via meson decay, deep inelastic scattering, and Z decay.

Findings

The ILC beam dump can effectively search for heavy neutral leptons across a wide mass range.

Multi-track signals significantly extend the detection reach.

The sensitivity surpasses other proposed experimental searches.

Abstract

A beam dump experiment can be seamlessly added to the {proposed} International Linear Collider (ILC) program because the high energy electron beam should be dumped after the collision point. The ILC beam dump experiment will provide an excellent opportunity to search for new long-lived particles. Since many of them can be produced by a rare decay of standard model particles, we evaluate spectra of the mesons and $\tau$ lepton at the decay based on the PHITS and PYTHIA8 simulations. As a motivated physics case, we study the projected sensitivity of heavy neutral leptons at the ILC beam dump experiment. The heavy neutral leptons can also be produced via deep inelastic scattering and $Z$ boson decay at the ILC main detector, which we include in the projection. With the multi-track signal, the reach would be greatly extended in mass and coupling, even compared with the other proposed searches.