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Paul Swallow

Publications and source records attributed to Paul Swallow.

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SET-ANUBIS: a modular pipeline for ANUBIS long-lived particle sensitivity studies

The proposed ANUBIS detector has been designed to search for Long-Lived Particle (LLP) signatures, which have become a focus for a variety of experiments within recent years. Due to the variety of possible LLP models and the need for directly comparable sensitivity results highlighting the potential coverage of ANUBIS, the SET-ANUBIS (Simulation, accEptance and sensiTivity studies framework for ANUBIS) framework has been developed. SET-ANUBIS is a flexible open-source Python framework that can perform full sensitivity studies of LLP signatures for the ANUBIS detector, allowing others to directly produce ANUBIS-like limits or even implement other geometries and detectors. It starts from a Universal FeynRules Output model or user-supplied rates; it exposes model parameters and particle content for user modification, and evaluates decay widths, branching ratios and lifetimes. MARTY can also be used to compute matrix elements, decay widths, branching ratios, and cross-sections. Then the framework prepares or runs event generation through Pythia8 or MadGraph, ingests HepMC event records, models the geometry of the ATLAS cavern and ANUBIS tracking stations, and applies a configurable sequence of geometric, kinematic and isolation requirements to select a set of surviving LLP candidates for evaluation. The implementation follows a ports-and-adapters architecture so that the core logic remains separate from external generators, persistent storage and visualisation. A scan-aware SQLite catalogue and content-addressed store preserve cards, metadata and compact selection-ready event bundles while avoiding duplicate artifacts. A pre-release version of the SET-ANUBIS framework has already been used to successfully derive the sensitivity of ANUBIS to three LLP benchmark models involving a Higgs portal and a Heavy Neutral Lepton model.

hep-ph

Calibration and Performance of proANUBIS: A proof-of-concept detector for the ANUBIS experiment

Long-lived particles with lifetimes $\tau>10$~ps are predicted by many extensions of the Standard Model with viable dark matter candidates. The ANUBIS experiment proposes to extend the experimental sensitivity to long-lived particles by instrumenting the ceiling of the ATLAS cavern with Resistive Plate Chamber detectors in order to reconstruct vertices from long-lived particle decays in the air-filled volume above the ATLAS detector. The proANUBIS detector has been installed in the ATLAS cavern to validate the detector technology planned for ANUBIS and to take in-situ measurements of muon and hadron fluxes inside the ATLAS cavern using $pp$ collision data from the LHC. In this paper, the data collected, reconstruction techniques used, and performance of the \proanubis detector are discussed. The detection efficiency and timing resolution are found to be consistent with expectations and to meet the performance requirements of ANUBIS.

hep-ex

Projected sensitivity of the ANUBIS detector to heavy neutral leptons

Long-Lived Particles (LLPs) are a common feature in various extensions to the Standard Model (SM) that seek to address known limitations. The ANUBIS detector has been proposed to extend the sensitivity of the ATLAS experiment at the LHC to LLPs by instrumenting the ceiling of the ATLAS detector cavern. This article presents the projected sensitivity of ANUBIS to Heavy Neutral Leptons (HNLs). For a minimal Majorana HNL model that only couples to a single flavour of lepton ($e$ or $\mu$) ANUBIS reaches a maximum sensitivity of $|V_{1e}|^2=1.8\times10^{-8}$ and $|V_{1\mu}|^2=1.9\times10^{-8}$ for a HNL mass of $m_{N_1}=6.4$ GeV and 6.3 GeV respectively. This provides complementary coverage to other proposed LLP experiments in the HNL parameter-space, with potential for significant improvement during ANUBIS data-taking through advances in analysis strategies. The results are obtained with SET-ANUBIS, a flexible framework to evaluate the sensitivity of ANUBIS to a variety of LLP models.

hep-ex

Commissioning of proANUBIS: A proof-of-concept detector for the ANUBIS experiment

Long-lived particles (LLPs), predicted by various extensions of the Standard Model (SM), have become a key focus of the contemporary search programme for physics beyond the SM. To enhance LLP discovery potential at the LHC, the ANUBIS experiment has been proposed to instrument the ceiling of the ATLAS experiment's underground cavern with dedicated tracking detectors. This report summarises recent progress towards realising ANUBIS. Specifically, a key milestone has been achieved with the installation and commissioning of proANUBIS, a prototype that serves as a proof-of-concept for ANUBIS. We describe the proANUBIS setup, including its remotely-operated data acquisition system and automatic signal processing chain. The proANUBIS demonstrator is used to evaluate the detector performance under realistic conditions in the UX1 ATLAS experimental cavern, including readout synchronisation with the ATLAS experiment. Furthermore, proANUBIS allows for the direct measurement of relevant background processes in a representative location within the ATLAS cavern, providing input for the simulation of such processes for the future ANUBIS detector. The paper concludes with an update on the current status of the ANUBIS project and its roadmap toward a full-scale implementation in the ATLAS cavern.

hep-ex

ANUBIS: Projected Sensitivities and Initial Results from the proANUBIS demonstrator with Run 3 LHC data

Despite the success of the Standard Model (SM) there remains behaviour it cannot describe, in particular the presence of non-interacting Dark Matter. Many models that describe dark matter can generically introduce exotic Long-Lived Particles (LLPs). The proposed ANUBIS experiment is designed to search for these LLPs within the ATLAS detector cavern, located approximately 20-30 m from the Interaction Point (IP). A prototype detector, proANUBIS, has taken data within the ATLAS detector cavern since 2024, corresponding to 104 $fb^{-1}$ of pp data. We report on the potential sensitivity of ANUBIS to a selection of LLP models, i.e. Higgs Portal and Heavy Neutral Leptons, as well as future planned studies. Additionally, we will show the first results of the proANUBIS demonstrator, and how it will be used to study the expected backgrounds for the ANUBIS detector.

hep-ex

Construction of proANUBIS: A proof-of-concept detector for the ANUBIS experiment

The ANUBIS experiment aims to search for long-lived particles at the Large Hadron Collider (LHC) at CERN. To assess the feasibility of the project, a prototype detector, proANUBIS, was designed, constructed, and prepared for installation in the UX1 ATLAS experimental cavern at the LHC. The primary physics goals of proANUBIS are to determine the technical limitations of the detector technology and to explore the ANUBIS detector concept through in-situ measurements of muon and hadron fluxes inside the ATLAS cavern, which can be used to refine Monte Carlo simulations of such fluxes further. This report describes the design and construction of the proANUBIS experimental setup using Resistive Plate Chambers (RPCs), highlighting the possible future use case of the technology for ANUBIS. Details on the RPC technology, construction processes, quality control measures, and performance studies are discussed. Furthermore, the RPC front-end on-detector electronics and data acquisition components of proANUBIS are presented.

hep-ex

2026 ESPPU input from the ANUBIS Collaboration

It is imperative for us as a particle physics community to fully exploit the physics potential of the High-Luminosity LHC. This calls for us not to leave any stone unturned in the search for Beyond the Standard Model (BSM) physics. Many BSM models that address fundamental questions of physics like the particulate nature of dark matter, the matter-antimatter asymmetry in the Universe, small but non-zero neutrino masses etc, predict Long-Lived Particles (LLPs) with macroscopic lifetimes of $\tau>10^{-10}$ s. The challenge in searching for BSM models with LLP signatures at the HL-LHC is that it requires the complementary interplay of general purpose detectors like ATLAS, CMS, and LHCb; dedicated detectors situated close to the beamline including the proposed Forward Physics Facility (FPF); and dedicated detectors covering a large decay volume at a reasonable solid angle transverse to the beamline, i.e., a Transverse Physics Facility (TPF). Hence, it is of vital importance to realise a TPF in order to expand dramatically the physics coverage within long-lived particle searches to harvest the physics at the HL-LHC fully. A TPF may be composed of several experiments based at the HL-LHC. In this document, we propose that the community realise the ANUBIS experiment as part of a TPF.

hep-ex

Technical design report for the CODEX-$\beta$ demonstrator

The CODEX-$\beta$ apparatus is a demonstrator for the proposed future CODEX-b experiment, a long-lived-particle detector foreseen for operation at IP8 during HL-LHC data-taking. The demonstrator project, intended to collect data in 2025, is described, with a particular focus on the design, construction, and installation of the new apparatus.

physics.ins-det

The Road Ahead for CODEX-b

In this Snowmass contribution we present a comprehensive status update on the progress and plans for the proposed CODEX-b detector, intended to search for long-lived particles beyond the Standard Model. We review the physics case for the proposal and present recent progress on optimization strategies for the detector and shielding design, as well as the development of new fast and full simulation frameworks. A summary of the technical design for a smaller demonstrator detector (CODEX-$β$) for the upcoming Run~3 of the LHC is also discussed, alongside the road towards realization of the full experiment at the High-Luminosity LHC.

hep-ex

Expression of Interest for the CODEX-b Detector

This document presents the physics case and ancillary studies for the proposed CODEX-b long-lived particle (LLP) detector, as well as for a smaller proof-of-concept demonstrator detector, CODEX-$β$, to be operated during Run 3 of the LHC. Our development of the CODEX-b physics case synthesizes `top-down' and `bottom-up' theoretical approaches, providing a detailed survey of both minimal and complete models featuring LLPs. Several of these models have not been studied previously, and for some others we amend studies from previous literature: In particular, for gluon and fermion-coupled axion-like particles. We moreover present updated simulations of expected backgrounds in CODEX-b's actively shielded environment, including the effects of shielding propagation uncertainties, high-energy tails and variation in the shielding design. Initial results are also included from a background measurement and calibration campaign. A design overview is presented for the CODEX-$β$ demonstrator detector, which will enable background calibration and detector design studies. Finally, we lay out brief studies of various design drivers of the CODEX-b experiment and potential extensions of the baseline design, including the physics case for a calorimeter element, precision timing, event tagging within LHCb, and precision low-momentum tracking.

hep-ex