arXiv subjects

Ian M. Shoemaker

Publications and source records attributed to Ian M. Shoemaker.

At least 19 recordsLinked to original sources

arXiv2026

Astrophysical Neutrino Sources as Colliders

High-energy neutrinos arise from processes at large center-of-mass energies, offering a window to test physics at comparable scales or beyond those accessible in collider experiments on Earth. Here, we present a recipe for extracting two-sided bounds on the inelastic $pp$ and $p\gamma$ cross sections from neutrino point-source data, by independently constraining every astrophysical input (cosmic-ray luminosities and target densities) through electromagnetic observations or theoretical arguments. The cross section is then the only remaining free parameter. Applying this framework to the IceCube associations with TXS~0506+056, NGC~1068, and the Galactic Plane, to a stacked population of eleven X-ray bright Seyfert galaxies, to the ultra-high-energy KM3NeT event KM3-230213A, and to projected observations of ultra-high-energy neutrinos, we obtain constraints that span center-of-mass energies from $\sqrt{s}\sim 1$ GeV to $\sim 10^{5}$ GeV, some of which are well beyond the reach of the LHC and, for the $p\gamma$ channel, beyond HERA. Several of these bounds are more stringent than unitarity limits.

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arXiv2026

Dark matter energy exchange in stars orbiting supermassive black holes

Stars on tight orbits around the supermassive black hole at the Galactic Center pass through regions where the dark matter~(DM) density may be strongly enhanced. We compute the orbit-averaged DM-induced energy exchange for S4714 as an example. It is a star on an exceptionally close and relativistic orbit around Sagittarius~A*. For a spiked dark matter profile, the exchange reaches the stellar luminosity at $\sigma_{\chi p} \sim 10^{-36}~\mathrm{cm}^2$ for MeV-GeV masses and $\sigma_{\chi e} \sim 5\times10^{-38}~\mathrm{cm}^2$ for sub-MeV masses, opening a new annihilation-free route toward dark-star phases. These cross sections lie within the range predicted by freeze-in scenarios and are consistent with cosmic-ray--boosted and solar-reflection dark matter constraints.

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arXiv2026

Direct Detection of Millicharged Particles from Supernovae

This work proposes a new terrestrial probe for millicharged particles (mCPs) and demonstrates promising discovery prospects. mCPs can be copiously produced in core-collapse supernovae (SNe), and a fraction may escape, travel to Earth and yield distinct signals. The mCP mass induces a time-of-flight (ToF) delay relative to the SN neutrino burst, opening a clean search window after the neutrino signal has passed. We compute the mCP-induced electron-recoil signals at XENONnT, JUNO, DUNE, and Hyper-Kamiokande for benchmark SN scenarios, and find that for $\varepsilon = 10^{-9}$ and sub-MeV to MeV-scale masses, more than 10 events per year can be detected. This search can improve upon existing SN cooling bound on $\varepsilon$ by up to an order of magnitude.

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arXiv2026

The Cosmic Neutrino Background is within Reach of Future Neutrino Telescopes

The cosmic neutrino background (C$\nu$B) can be boosted to high energies due to scatterings with energetic cosmic rays (CRs) across cosmological scales. Previous calculations focused on neutral current incoherent and coherent elastic scatterings of cosmic-ray protons off relic neutrinos. However, charged current interactions and deep inelastic scatterings are also expected to occur, which enhances the boosted relic neutrino fluxes on Earth. Here, we compute the \textit{total} diffuse boosted cosmic neutrino background (DBC$\nu$B) arising from CRs at all redshifts in the Universe, accounting for neutral current and charged current elastic and deep inelastic scatterings. We find that IceCube already places an upper limit on the cosmic neutrino background overdensity in cosmological scales of ~$\mathcal{O}(100-1000)$ at $E_{\nu}=10^{10}$ GeV, for a lightest neutrino mass of $m_{\nu} \gtrsim 0.1$ eV. We further show that IceCube-Gen2 could test $\mathcal{O}(1-10)$ C$\nu$B overdensities, and the combination of $10$ future neutrino telescopes with similar sensitivity would allow us to test the $\Lambda$CDM expected C$\nu$B density for a lightest neutrino mass compatible with the KATRIN bound.

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arXiv2025

Millicharged Particle Production in Pulsars via the Schwinger Effect

Low mass particles with small electric charges can be produced abundantly in large electric fields via the Schwinger effect. We study the production rate of such particles inside the polar gap of nearby pulsars. After production they are accelerated above MeV energies by the local electric fields. These pulsar-produced millicharged particles can be detected at Earth in low-threshold dark matter direct detection experiments. We find that the current XENONnT data constrains millicharged particles produced in the Crab pulsar to have charges less than $O(10^{-6})$ for sub-eV masses.

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arXiv2025

Probing Dark Matter Interactions with Stellar Motion near Sagittarius A*

Stars orbiting Sgr A* at the Milky Way's center provide a unique laboratory to test gravity and dark matter (DM). We demonstrate that DM interactions in stellar interiors induce a novel momentum transfer force, altering orbits beyond gravitational effects. Using S2's 2000-2019 orbital data we derive the first astrophysical constraints on DM-nucleon scattering, excluding new sub-GeV parameter space. Stellar lifetime constraints over Myr timescales complement these, surpassing some direct detection and cosmological limits. This establishes stellar dynamics as a novel probe of DM interactions.

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arXiv2025

Cosmic-ray boosted inelastic dark matter from neutrino-emitting active galactic nuclei

Cosmic rays may scatter off dark matter particles in active galactic nuclei, where both the densities of cosmic rays and dark matter are expected to be very large. These scatterings could yield a flux of boosted dark matter particles directly detectable on Earth, which enhances the sensitivity of dark matter direct detection and neutrino experiments to light and inelastic dark matter models. Here we calculate the cosmic-ray boosted dark matter flux from the neutrino-emitting active galactic nuclei, NGC 1068 and TXS 0506+056, by considering realistic cosmic-ray distributions, deep inelastic scatterings, and mass splittings in the dark sector. From this we derive novel bounds from these sources on light and/or inelastic dark matter models with Super-K and XENONnT. We find that cosmic-ray boosted dark matter from neutrino-emitting active galactic nuclei can test regions of parameter space favored to reproduce the observed relic abundance of dark matter in the Universe, and that are otherwise experimentally inaccessible.

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arXiv2025

Finding BSM Needles in Electromagnetic Haystacks at DUNE

In this work, motivated by several beyond the Standard Model signal topologies, we perform detailed background mitigation analyses for the DUNE near detector. Specifically, we investigate $e^+ e^-$, $e^- \gamma$, $\gamma$, and $\gamma\gamma$ final states that may arise from long-lived particles, including light mediators, dark matter, heavy neutral leptons, and axion-like particles (ALPs), decaying or scattering inside the liquid argon detector. To this end, we employ both photophilic and leptophilic ALPs as phenomenological benchmarks. The aforementioned final states leave a hard electromagnetic signature with no hadronic activity above the detector energy thresholds. Nevertheless, such signatures are not immune to backgrounds from neutrino scattering in the detector, which are in the focus of our study. In order to model realistic experimental analyses, we take into account particle misidentification rates, cross-contamination effects, and detector responses. We calculate confidence limit projections for DUNE, thereby presenting realistic capabilities for constraining or discovering new physics manifested through electromagnetic showers.

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arXiv2025

Sub-GeV Dark Matter Under Pressure from Direct Detection

The DAMIC-M collaboration recently reported impressive bounds on sub-GeV dark matter, robustly testing both thermal and non-thermal models for the very first time. In this work we derive novel bounds from the recent PandaX-4T ionization S2-only search for Coherent Elastic Neutrino-Nucleus Scattering (CE$\nu$NS). We find that the PandaX-4T S2-only data is able to compete with the DAMIC-M results, providing the best constraints for scalar and asymmetric thermal dark matter models for masses between 20 to 200 MeV. We further discuss the implications of recent direct detection results for several other sub-GeV dark matter models, highlighting their complementarity with astrophysical, cosmological and laboratory probes.

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arXiv2025

Monophotons at Neutrino Experiments from Neutrino Polarizability

Nontrivial electromagnetic properties of neutrinos are an avenue to physics beyond the Standard Model. To this end, we investigate the power of monophoton signals at neutrino experiments to probe a higher-dimensional operator connecting neutrinos to SM photons dubbed, neutrino polarizability. A simplified scenario giving rise to this operator involves a new pseudo-scalar that couples to both neutrinos and photons, with clear implications for axion-like particle (ALP) and Majoron physics. By analyzing the photon energy spectrum and angular distributions, we find that NOMAD and MiniBooNE currently set the most stringent limits, while SBND and the DUNE near detector will soon provide significantly improved constraints.

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arXiv2025

Nucleon Decays into Light New Particles in Neutrino Detectors

Proton and neutron decays into light new particles $X$ can drastically change the experimental signatures and benefit from the complementarity of large water-Cherenkov neutrino detectors such as Super/Hyper-Kamiokande and tracking detectors such as JUNO and DUNE. The proton decays $p\to \ell^+ X$ and $p\to \pi^+ X$ with $m_X$ near phase-space closure lead to charged particles below Cherenkov threshold, rendering them practically invisible in Super- and Hyper-Kamiokande but not in JUNO and DUNE, which are therefore uniquely positioned for these baryon-number-violating signatures despite their smaller size. As an additional signature, such nucleon decays in Earth can produce a sizable flux of $X$ particles in underground detectors. We present a simple model in which nucleons decay into sub-GeV sterile neutrinos that subsequently decay through active-sterile neutrino mixing, with a promisingly large number of events in Super-Kamiokande even in the seesaw-motivated parameter space.

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arXiv2025

Neutrino Theory in the Precision Era

This document summarises discussions on future directions in theoretical neutrino physics, which are the outcome of a neutrino theory workshop held at CERN in February 2025. The starting point is the realisation that neutrino physics offers unique opportunities to address some of the most fundamental questions in physics. This motivates a vigorous experimental programme which the theory community fully supports. \textbf{A strong effort in theoretical neutrino physics is paramount to optimally take advantage of upcoming neutrino experiments and to explore the synergies with other areas of particle, astroparticle, and nuclear physics, as well as cosmology.} Progress on the theory side has the potential to significantly boost the physics reach of experiments, as well as go well beyond their original scope. Strong collaboration between theory and experiment is essential in the precision era. To foster such collaboration, \textbf{we propose to establish a CERN Neutrino Physics Centre.} Taking inspiration from the highly successful LHC Physics Center at Fermilab, the CERN Neutrino Physics Centre would be the European hub of the neutrino community, covering experimental and theoretical activities.

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arXiv2025

Supernova Gamma-Ray Constraints from Heavy Sterile Neutrino Decays

Heavy sterile neutrinos can be produced in core-collapse supernovae (CCSNe), which are superb particle generators because of their high densities and temperatures. If the sterile neutrinos are long-lived, these may be produced inside the supernova core and escape the stellar envelope, later decaying into SM particles like photons and neutrinos. In this work, we first improve the calculation of the $\gamma$-ray fluxes. We then revisit the bounds on the sterile neutrino parameter space from the non-observation of $\gamma$-rays from SN1987A by the Solar Maximum Mission (SMM) and constraints from the diffuse $\gamma$-ray background arising from sterile neutrino decays. We find that the constraints arising from both the SMM data and the diffuse $\gamma$-ray background are weaker than those that have previously appeared in the literature. Finally, we study the sensitivity of several present and near-future $\gamma$-ray telescopes such as e-ASTROGAM and Fermi-LAT, assuming a nearby future galactic CCSN. We show that future observations can probe mixing angles as low as $|U_{\tau/\mu4}|^2\sim 5\times10^{-17}$.

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arXiv2024

Cosmology-Independent Constraints on Irreducible Magnetic Monopole Background

We present a novel mechanism for the irreducible production of magnetic monopoles from interactions of cosmic rays and interstellar medium (ISM). Resulting monopoles drain energy from galactic magnetic fields, disrupting their formation and sustainability. We generalize conventional Parker bounds to monopoles with extended energy spectrum and, considering cosmic ray ISM monopole production, set novel constraints from disruption of Milky Way Galactic magnetic fields and their seeds. Further, we set first constraints on disruption of galactic magnetic fields and their seeds of Andromeda galaxy, with results being competitive with distinct existing bounds. Unlike Parker limits of previous works that relied on cosmological monopoles, our constraints are independent of cosmological monopole production or their primordial abundance. Besides, we estimate new constraints on dipole magnetic moments generated from cosmic ray ISM interactions. We discuss implications for monopoles with generalized magnetic charges.

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arXiv2024

Clarity through the Neutrino Fog: Constraining New Forces in Dark Matter Detectors

The PANDAX-4T and XENONnT experiments present indications of Coherent Elastic Neutrino Nucleus Scattering (CE$\nu$NS) from ${}^{8}$B solar neutrinos at 2.6$\sigma$ and 2.7$\sigma$, respectively. This constitutes the first observation of the neutrino "floor" or "fog", an irreducible background that future dark matter searches in terrestrial detectors will have to contend with. Here, we first discuss the contributions from neutrino-electron scattering and from the Migdal effect in the region of interest of these experiments, and we argue that they are non-negligible. Second, we make use of the recent PANDAX-4T and XENONnT data to derive novel constraints on light scalar and vector mediators coupling to neutrinos and quarks. We demonstrate that these experiments already provide world-leading laboratory constraints on new light mediators in some regions of parameter space.

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arXiv2024

Enhancing the Sensitivity to Seesaw Predictions in Gauged $B-L$ Scenarios

New gauge bosons coupled to heavy neutral leptons (HNLs) are simple and well-motivated extensions of the Standard Model. In searches for HNLs in proton fixed-target experiments, we find that a large population of gauge bosons ($Z^\prime$) produced by proton bremsstrahlung may decay to HNLs, leading to a significant improvement in existing bounds on the ($m_{HNL}, U_{\alpha}$), where $U_\alpha$ represent the mixing between HNL and the active neutrinos with flavor $\alpha$. We study this possibility in fixed target experiments with the 8 GeV proton beams, including SBND, MicroBooNE, and ICARUS, as well as DUNE and DarkQuest at 120 GeV. We find the projected sensitivities to additional $Z^\prime$-mediated HNL production can bring the seesaw mechanism of the neutrino masses within a broadened experimental reach.

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arXiv2024

Upper Limits on the Cosmic Neutrino Background from Cosmic Rays

Extragalactic and galactic cosmic rays scatter with the cosmic neutrino background during propagation to Earth, yielding a flux of relic neutrinos boosted to larger energies. If an overdensity of relic neutrinos is present in galaxies, and neutrinos are massive enough, this flux might be detectable by high-energy neutrino experiments. For a lightest neutrino of mass $m_ν \sim 0.1$ eV, we find an upper limit on the local relic neutrino overdensity of $\sim 10^{13}$ and an upper limit on the relic neutrino overdensity at TXS 0506+056 of $\sim 10^{10}$. Future experiments like GRAND or IceCube-Gen2 could improve these bounds by orders of magnitude.

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arXiv2024

Neutrino Portals, Terrestrial Upscattering, and Atmospheric Neutrinos

We consider the upscattering of atmospheric neutrinos in the interior of the Earth producing heavy neutral leptons (HNLs) which subsequently decay inside large volume detectors (e.g. Super-Kamiokande or DUNE). We compute the flux of upscattered HNLs arriving at a detector, and the resultant event rate of visible decay products. Using Super-Kamiokande's atmospheric neutrino dataset we find new leading constraints for dipole couplings to any flavor with HNL masses between roughly 10 MeV and 100 MeV. For mass mixing with tau neutrinos, we probe new parameter space near HNL masses of $\sim 20$ MeV with prospects for substantial future improvements. We also discuss prospects at future experiments such as DUNE, JUNO, and Hyper-Kamiokande.

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