Updated sensitivities to heavy neutral leptons at the LHC far detectors and SHiP

TL;DR

This paper updates the sensitivity estimates for detecting heavy neutral leptons at various LHC far detectors and SHiP, incorporating recent experimental design changes and improved modeling tools.

Contribution

It provides revised sensitivity calculations for heavy neutral leptons using updated detector geometries and background estimates across multiple experiments.

Findings

Enhanced sensitivity estimates for heavy neutral leptons at MATHUSLA, ANUBIS, and SHiP.

Implementation of latest detector designs in the Displaced Decay Counter tool.

Revised projections showing improved detection prospects for LLP scenarios.

Abstract

In recent years, a number of experiments dedicated to searches for long-lived particles (LLPs) have been proposed, approved, or have entered operation. While the sensitivities of these experiments to various LLP scenarios have been extensively studied, key aspects--such as detector geometries, background estimates, and projected operational durations--for several facilities, including MATHUSLA, ANUBIS, and SHiP, have undergone significant updates. In this work, we implement the latest experimental designs in the Displaced Decay Counter tool for calculating detector acceptances and signal-event yields, and re-evaluate their sensitivity reach to one of the most widely studied LLP scenarios, namely minimal heavy neutral leptons.