arXiv subjects

Hannah Banks

Publications and source records attributed to Hannah Banks.

18 recordsLinked to original sources

arXiv2026

The Plan B Model: $Z^{\prime}$ collider phenomenology and discovery prospects

The Plan B Model was proposed by Allanach et al. (2023) and explains some gross features of the fermion mass spectrum. It also affects the predictions of various observables involving the $b \rightarrow s$ quark-flavour transition. The model predicts a new TeV-scale $Z^{\prime}$ which decays into various different final states. We constrain the viable parameter space of the model by re-casting several LHC direct searches for the $Z^{\prime}$ in addition to using Contur to test the model against unfolded measurements of various differential cross sections that are predicted to be non-zero in the Standard Model. We delineate the regions of parameter space that are excluded by current LHC data, and estimate the projected reach of the high luminosity LHC.

hep-ph↗

arXiv2026

Big Axions

We introduce big axions: axion models in which a Nambu-Goldstone mode emerges from the collective spontaneous breaking of a network of U(1) symmetries delocalized in theory space. Big axions naturally realize high-quality accidental global symmetries, admit both pre- and post-inflationary cosmological histories, and exhibit rich topological structures that interpolate between ordinary Peccei-Quinn axions and axions which descend from extra-dimensional gauge fields. We identify a minimal phenomenologically viable subclass, little big axions, and demonstrate that they provide a robust solution to the strong charge-parity problem in quantum chromodynamics while potentially accounting for some or all of the dark matter of the universe.

hep-ph↗

arXiv2026

Probing Solar Symmetrons with Direct Detection

We provide the first investigation of the solar production of symmetrons, a well-motivated class of screened scalar fields with density dependent couplings to the Standard Model, and their subsequent absorption in underground direct detection experiments. We compute the flux of symmetrons produced through photon conversion in the magnetic field of the solar tachocline, and constrain the resulting luminosity to not exceed 3% of the observed solar output. Even under the conservative assumption that production occurs only in the tachocline, this criterion yields robust astrophysical bounds on previously uncharted regions of symmetron parameter space, and predicts a keV-scale symmetron spectrum at Earth. We then derive the corresponding absorption signal in liquid xenon detectors, where symmetrons can interact with electrons through both conformal and disformal couplings. Using binned data from XENONnT, we obtain new direct-detection limits that are complementary to the solar luminosity constraint, further tightening the viable symmetron parameter space. Our results demonstrate that the Sun provides a testable, previously unexploited, source of symmetrons, and highlight that the interplay of astrophysical and laboratory searches offers a powerful strategy for probing screened scalar theories.

hep-ph↗

arXiv2025

Searching for Ultralight Dark Matter with MOLeQuTE: a Massive Optically Levitated Quantum Tabletop Experiment

Many well theoretically motivated models of ultralight dark matter are expected to give rise to feeble oscillatory forces on macroscopic objects. Optically trapped sensors have high force sensitivities but have remained relatively unexplored in this context. In this work we propose a new, tunable, optically trapped sensor specifically designed to detect such forces. Our design features a high-mass ($\sim$ mg) plate whose high aspect ratio allows its weight to be supported by a vertical beam without excessive heating. We present the first systematic analysis and optimisation of quantum noises in optically trapped systems and show that our setup has the potential to operate at the standard quantum limit with current off-the-shelf technologies. We demonstrate that our sensor could offer unique access to large regions of uncharted parameter space of vector B-L dark matter, with projected sensitivities that could advance existing limits by several orders of magnitude over a broad range of frequencies.

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arXiv2025

Searching for screened scalar forces with long-baseline atom interferometers

Screened scalars are ubiquitous in many dark-sector models. They give rise to non-trivial fifth forces whilst evading experimental constraints through density-dependent screening mechanisms. We propose equipping a 10\,m-scale long-baseline atom interferometer with an annular planar source mass inside the vacuum chamber to search for such screened fifth forces. Two key challenges arise: distinguishing the static fifth force from backgrounds, and isolating it from the plate's Newtonian gravity. We introduce the `$Q$-flip protocol', which alternates between interferometry sequences to induce controllable time-dependence, aiding signal extraction and de-trending of transient noise. We further develop an \emph{in situ} calibration procedure to characterise the plate's Newtonian gravity and reach shot-noise-limited sensitivity. We show that our proposal could test theoretically motivated parameter space, advancing existing bounds in chameleon and symmetron screened scalar models by $1$ to $1.5$ orders of magnitude. Our proposal is directly applicable to forthcoming experiments, such as AION-10 or VLBAI, and is readily extensible to broader theoretical models and longer baselines.

hep-ph↗

arXiv2025

Flavor hierarchies with nonminimal irreducible representations

We propose a new class of flavour models in which the spurion which breaks Standard Model flavour symmetries transforms in a non-minimal representation. Hierarchies in fermion masses, which arise from multiple insertions of this spurion, may be generated in a technically natural, accidental manner, from a handful of untuned $\mathcal{O}(1)$ elements in the UV. This relies explicitly on the non-Abelian nature of the symmetry, distinguishing it from standard Froggatt-Nielsen-like scenarios. The pattern of flavour violating operators at dimension-6 can radically differ from previously considered scenarios, and emphasises the need for a broad flavour programme across all generations.

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arXiv2025

Probing new physics in the top sector using quantum information

Recent studies have shown that quantitative concepts from quantum information theory can play a role in analysing collider physics, including elucidating new physics. In this paper, we study various QI measures including magic, trace distance and fidelity distance, in generic new physics scenarios modelled by the Standard Model Effective Field Theory. We argue that such measures can indeed show up differences with respect to the pure Standard Model, and we compare our results with similar findings for the concurrence discussed previously in the literature. We examine the relative sensitivity of different measures to new physics in two-dimensional bins of the top pair invariant mass and scattering angle, finding that the concurrence, magic and trace distance each emerge as the best measure in at least some regions of the phase space. This highlights the importance of exploring multiple quantum information measures in the hunt for beyond the Standard Model physics.

hep-ph↗

arXiv2025

Quantum Information meets High-Energy Physics: Input to the update of the European Strategy for Particle Physics

Some of the most astonishing and prominent properties of Quantum Mechanics, such as entanglement and Bell nonlocality, have only been studied extensively in dedicated low-energy laboratory setups. The feasibility of these studies in the high-energy regime explored by particle colliders was only recently shown and has gathered the attention of the scientific community. For the range of particles and fundamental interactions involved, particle colliders provide a novel environment where quantum information theory can be probed, with energies exceeding by about 12 orders of magnitude those employed in dedicated laboratory setups. Furthermore, collider detectors have inherent advantages in performing certain quantum information measurements, and allow for the reconstruction of the state of the system under consideration via quantum state tomography. Here, we elaborate on the potential, challenges, and goals of this innovative and rapidly evolving line of research and discuss its expected impact on both quantum information theory and high-energy physics.

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arXiv2024

Terrestrial Very-Long-Baseline Atom Interferometry: Summary of the Second Workshop

This summary of the second Terrestrial Very-Long-Baseline Atom Interferometry (TVLBAI) Workshop provides a comprehensive overview of our meeting held in London in April 2024, building on the initial discussions during the inaugural workshop held at CERN in March 2023. Like the summary of the first workshop, this document records a critical milestone for the international atom interferometry community. It documents our concerted efforts to evaluate progress, address emerging challenges, and refine strategic directions for future large-scale atom interferometry projects. Our commitment to collaboration is manifested by the integration of diverse expertise and the coordination of international resources, all aimed at advancing the frontiers of atom interferometry physics and technology, as set out in a Memorandum of Understanding signed by over 50 institutions.

hep-ex↗

arXiv2024

Simulation of thermal conduction by asymmetric dark matter in realistic stars and planets

Dark matter captured in stars can act as an additional heat transport mechanism, modifying fusion rates and asteroseismoloigcal observables. Calculations of heat transport rates rely on approximate solutions to the Boltzmann equation, which have never been verified in realistic stars. Here, we simulate heat transport in the Sun, the Earth, and a brown dwarf model, using realistic radial temperature, density, composition and gravitational potential profiles. We show that the formalism developed in arXiv:2111.06895 remains accurate across all celestial objects considered, across a wide range of kinematic regimes, for both spin-dependent and spin-independent interactions where scattering with multiple species becomes important. We further investigate evaporation rates of dark matter from the Sun, finding that previous calculations appear robust. Our Monte Carlo simulation software Cosmion is publicly available.

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arXiv2024

A Nuclear Interferometer for Ultra-Light Dark Matter Detection

We propose the nuclear interferometer - a single-photon interferometry experiment based upon the thorium-229 nuclear clock transition - as a novel detector for ultra-light dark matter. Thanks to the enhanced sensitivity of this transition to the variation of fundamental constants, we find that possible realisations of such an experiment deploying either single ions or clouds of atoms have the potential to complement advanced very-long-baseline terrestrial clock atom interferometers in the search for ultra-light dark matter with scalar couplings to photons in the future. Nuclear interferometry may also offer an unparalleled window to new physics coupling to the QCD sector via quarks or gluons, with a discovery reach that could enhance existing and proposed experiments over a range of frequencies in the direction of well-motivated parameter space.

hep-ph↗

arXiv2023

Broad Sterile Neutrinos & the Reactor/Gallium Tension

Significant evidence exists for the apparent disappearance of electron-type neutrinos in radioactive source experiments. Yet, interpreted within the standard `3+1 sterile neutrino scenario', precision short-baseline measurements of electron antineutrinos from nuclear reactors strongly disagree with these results. Recently, it has been demonstrated that allowing for a finite wavepacket size for the reactor neutrinos can ameliorate such a tension, however the smallness of the required wavepackets is a subject of intense debate. In this work, we demonstrate that a `broad' sterile neutrino may relax this tension in much the same way. Such a phenomenological possibility can arise in plausible hidden sector scenarios, such as a clockwork-style sector, for which we provide a concrete microscopic model.

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arXiv2023

Terrestrial Very-Long-Baseline Atom Interferometry: Workshop Summary

This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more km-scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions.

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arXiv2023

Gravitational Wave Backgrounds from Colliding ECOs

Long baseline atom interferometers offer an exciting opportunity to explore mid-frequency gravitational waves. In this work we survey the landscape of possible contributions to the total 'gravitational wave background' in this frequency band and advocate for targeting this observable. Such an approach is complimentary to searches for resolved mergers from individual sources and may have much to reveal about the Universe. We find that the inspiral phases of stellar-mass compact binaries cumulatively produce a signal well within reach of the proposed AION-km and AEDGE experiments. Hypothetical populations of dark sector exotic compact objects, harbouring just a tiny fraction of the dark energy density, could also generate signatures unique to mid- and low-frequency gravitational wave detectors, providing a novel means to probe complexity in the dark sector.

gr-qc↗

arXiv2022

How Broad is a Neutrino?

Canonical neutrino oscillations arise due to the propagation of three mass eigenstates from production to detection. We aspire to capture, in one simple framework, a broad range of new physics effects on neutrino propagation beyond this canonical picture - this can be done by promoting the neutrino propagators to the general K\"all\'en-Lehmann form. In this work we demonstrate how models predicting additional light propagating species of neutrino are naturally accommodated in this language and propose a simple model spectrum composed of just three `broadened' states as a flexible ansatz by which to explore the phenomenology of new physics in neutrino propagation. Reinterpreting existing neutrino oscillation measurements, we illustrate how this framework provides the capacity to probe deviations from the standard three-neutrino scenario systematically and generally. Whilst current data allows for relatively strong constraints on broadened neutrinos, we find the upcoming JUNO experiment will yield significant improvements, particularly for the heaviest neutrino, paving the way to a clearer understanding of how neutrinos propagate in vacuum.

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arXiv2022

Simulation of energy transport by dark matter scattering in stars

Asymmetric dark matter (ADM) that is captured in stars can act as an efficient conductor of heat. Small ADM-induced changes in a star's temperature gradient are known to alter neutrino fluxes and asteroseismological signatures, erase convective cores and modify a star's main sequence lifetime. The Sun's proximity to us makes it an ideal laboratory for studying these effects. However, the two formalisms commonly used to parametrize such heat transport were developed over 30 years ago, and calibrated with a single set of simulations. What's more, both are based on assumptions that break down at the Knudsen transition, where heat transport is maximized. We construct a Monte Carlo simulation to exactly solve the Boltzmann collision equation, determining the steady-state distribution and luminosity carried in stars by ADM with cross sections that depend on velocity and momentum. We find that, although the established (Gould and Raffelt) formalism based on local thermal equilibrium does well for constant cross sections, the isothermal (Spergel and Press) method actually performs better across all models with a simple, universal rescaling function. Based on simulation results, we provide recommendations on the parametrization of DM heat transport in stellar evolution models.

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arXiv2021

Hide and Seek with the Third Family Hypercharge Model's $Z^\prime$ at the Large Hadron Collider

The Third Family Hypercharge Model predicts a $Z^\prime$ gauge boson with flavour dependent couplings which has been used to explain anomalies in meson decay processes which involve the $b\rightarrow s\mu^+\mu^-$ transition. The model predicts that a TeV-scale $Z^\prime$ should decay to particle-antiparticle pairs of muons, taus, top quarks and bottom quarks with appreciable branching ratios. We reinterpret various ATLAS and CMS search limits for $Z^\prime$ production followed by such decays at the LHC over a parameter space of the model that results from a successful combined fit to the $b\rightarrow s l^+ l^-$ data and precision electroweak observables. Current exclusions in parameter space and expected sensitivities of the various different channels in the high-luminosity run are compared. We find that the high-luminosity run of the LHC will significantly increase the sensitivity to the model beyond the existing observational limits, which we find to be surprisingly weak.

hep-ph↗

arXiv2020

Charting the Fifth Force Landscape

Fifth forces arising from hidden sector scalar operator exchange, as probed in a variety of present and planned experiments, can be captured by a general dispersion relation involving one real, positive, spectral density function. Previously considered scalar fifth forces, from tree-level to more exotic loop-level possibilities, are derived in this formalism, without explicitly performing conventional loop calculations. A variety of experimental observables commonly used in fifth force searches are also presented in the same formalism, allowing the straightforward extraction of limits on any specific model. The speculative possibility of probing hidden sector violations of unitarity, causality, or locality, manifested as a breakdown of the positivity of the spectral density, is also discussed.

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