The ANUBIS detector and its sensitivity to neutral long-lived particles

TL;DR

The ANUBIS detector aims to significantly improve sensitivity to long-lived particles at the LHC, enabling detection of rare Higgs decays into scalar particles with various masses and lifetimes.

Contribution

This paper proposes the design and physics potential of the ANUBIS detector, highlighting its superior sensitivity to long-lived particles compared to existing experiments.

Findings

ANUBIS can probe Higgs exotic decays with branching ratios down to 10^{-6}.

It can detect long-lived scalars with masses of 10-60 GeV and lifetimes up to 18 meters.

The detector's background contributions are manageable and well-understood.

Abstract

Long-lived particles (LLPs), i.e., particles with macroscopic lifetimes $\tau>10$~ns, appear in various extensions of the Standard Model (SM) that address fundamental questions like the particulate nature of dark matter or baryogenesis. The ANUBIS detector will achieve unprecedented sensitivity to such models compared to existing and approved experiments by instrumenting a large decay volume adjacent to the ATLAS experiment at the High-Luminosity LHC with tracking detectors. This paper outlines the proposed detector layouts for ANUBIS, explores their physics potential with a scalar LLP model, and identifies the preferred layout, comparing it to other experiments. The potential background contributions to ANUBIS are estimated using a data-driven method, and the topology of potential background events is studied using Monte Carlo simulations. Overall, ANUBIS is expected to probe branching ratios down to $\mathcal{O}$(10$^{-6})$ for exotic decays of the Higgs boson to scalar long-lived particles with masses of 10, 15, 40, and 60 GeV and proper lifetimes of $c\tau=2.4,\, 3.0,\, 12$, and 18 m, respectively. Moreover, for branching ratios of 0.1\% of the Higgs boson into long-lived scalars with a mass of 15 GeV, ANUBIS can probe a $c\tau$ range between $1.1\times10^{-1}$~m and $4.0\times10^3$~m.