arXiv subjects

Hooman Davoudiasl

Publications and source records attributed to Hooman Davoudiasl.

At least 19 recordsLinked to original sources

arXiv2026

Cosmic Overture Echoed in a Stellar Final Act: Implications of Nanohertz Gravitational Waves for Core Collapse Supernova Neutrinos

The growing evidence for nanohertz gravitational waves, from NANOGrav and other observations, may be pointing to a cosmological first-order phase transition at temperatures of $\mathcal{O}(10-100)\;\mathrm{MeV}$. Such an interpretation requires beyond the Standard Model dynamics in this energy range. If so, it may well be the case that galactic core-collapse supernova explosions would produce the key components related to the first-order phase transition, leaving detectable imprints on the spectrum of neutrinos emitted in the initial few seconds of the collapse. This might provide further evidence in support of the early universe interpretation of the nanohertz gravitational wave signal. The scenario proposed here is also suggestive of a low-mass seesaw mechanism to explain neutrino masses. We outline the prospects for future observations of Galactic supernovae to uncover the signals of this scenario, with further confirmation from future pulsar timing array measurements of primordial nanohertz gravitational waves.

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arXiv2026

Thermal Emission of Dark Photons from Earth's Core

Dark photons in the sub-eV regime may be produced by the Earth's hot core, representing a much less extreme environment than stellar cores. We consider this possibility and estimate constraints on the kinetic mixing parameter $\varepsilon$ that governs dark photon coupling to charged particles, using Earth core cooling arguments and via dark matter direct detection experiments. Our estimates do not find new constraints on the relevant parameter space from these considerations. Depending on the underlying parameters governing the thermal production of dark photons in the Earth, either core cooling or a future experiment, like Oscura with 30 kg-yr of exposure, can constrain $\varepsilon$ about one order of magnitude above the current astrophysical bounds, over the dark photon mass range $\sim 10^{-4}-0.1$~eV.

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arXiv2026

Novel Signatures of Matter-Induced Dark Matter Decay in Large-Volume Neutrino Telescopes

Large-volume neutrino telescopes offer a unique opportunity to search for decaying dark matter through events containing a pair of energetic, highly non-collimated muon tracks emerging from a common vertex. Such events would have negligible Standard Model backgrounds and would constitute a striking signature of new physics. Conventional dark matter annihilation or decay, however, is too strongly constrained to produce an observable rate of such events. We therefore consider scenarios in which an excited dark matter state is extremely long-lived in vacuum but decays much more rapidly in the presence of ordinary matter. We present two realizations of this mechanism. In the first, a long-range scalar field sourced by ordinary matter modifies the dark-sector mass spectrum, kinematically opening the decay $χ_2 \rightarrow χ_1 Z'$ near the Earth while leaving it forbidden in vacuum. In the second, the scalar background induces kinetic mixing between a heavy $Z'$ and the photon, greatly enhancing the three-body decay $χ_2\toχ_1μ^+μ^-$ in matter-rich environments. We calculate the resulting distributions of muon energies and opening angles and show that viable regions of parameter space can yield observable event rates in IceCube, KM3NeT, and other large-volume neutrino telescopes while remaining consistent with existing constraints. We also briefly consider the sensitivity of IceCube to multi-muon events produced by the decays of cosmologically long-lived charged particles with masses $\gtrsim 1$ TeV.

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arXiv2026

Neutron stars can shine a light on elusive lepton-flavor-violating dark matter

We investigate a scenario in which dark matter (DM) poses a challenge to conventional direct and indirect detection, making it much more elusive than typical candidates. We focus on thermally produced DM that couples to electrons and muons via a lepton-flavor-violating (LFV) axion-like particle (ALP). Given the DM kinematics and lack of muon targets on Earth, direct detection would be infeasible. Indirect detection of our DM candidate is also hampered by the dominance of $p$-wave annihilation. However, we demonstrate that neutron stars (NS) can serve as probes of such a scenario, through future dedicated observational campaigns. Infalling DM is accelerated to semi-relativistic velocities, triggering inelastic $χe \leftrightarrow χμ$ scattering off both electrons and muonic targets within the NS. We show that ``flavor blocking'' -- the kinematic suppression of LFV interactions at low energies -- prevents DM thermalization with the cold neutron star, enabling efficient $p$-wave annihilations. The resulting NS surface temperatures ($T_s \gtrsim 2 \times 10^3~\mathrm{K}$) offer a possible signature for future infrared searches, probing thermal relics beyond the reach of direct, indirect, and accelerator experiments.

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arXiv2026

Long-Lived Dark Hadrons at the Electron-Ion Collider

We study a dark non-Abelian gauge sector with GeV-scale confinement. The dark sector is assumed to couple only feebly to the Standard Model, while its low-energy spectrum may contain long-lived flavor-diagonal dark pions. Signals of these states are particularly well suited to the Electron-Ion Collider (EIC), where the absence of a hard trigger requirement and the capability to record soft final-state particles offer a complementary probe of dark hadronization dynamics. We present a benchmark portal construction, discuss the mixing between an axion-like mediator and dark pions, and identify the resulting displaced-decay signature.

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arXiv2026

Electron-Ion Collider as a Discovery Tool for Invisible Dark Bosons

We illustrate how the future Electron-Ion Collider (EIC) can be used to discover dark bosons with masses in the $\sim$ (10~MeV -- 10~GeV) regime, having a wide range of properties. We only require that the dark bosons have a non-negligible weak coupling to electrons and decay with $\ord{1}$ branching fraction into invisible final states. Our signal selection takes advantage of the excellent electron beam kinematic measurements and the capability to tag incoherent scattering, as envisioned at the EIC. This makes the EIC a powerful tool for uncovering potential dark sector forces, for a variety of possibilities.

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arXiv2026

Continuous coherent spin-frequency metrology in storage rings via resonant beam-driven detection

Precision measurements in storage rings are increasingly limited by the ability to monitor collective spin dynamics coherently over long time scales. Existing polarimetry techniques rely on destructive scattering processes that preclude continuous, non-intercepting tracking of spin evolution and constrain both statistical sensitivity and systematic control. Here we introduce a non-destructive, phase-coherent polarimetry method in which the stored beam polarization is treated as a continuous dynamical observable rather than a quantity inferred from scattering events. Spin-dependent electromagnetic fields generated by a polarized relativistic beam establish a symmetry-selected differential signal on pickup electrodes. This signal is transduced into a narrowband phase modulation of a high-Q resonator interrogated with a coherent probe, while dominant charge-induced backgrounds are rejected through geometric symmetry, helicity reversal, and synchronous demodulation. Controlled spin precession (spin-wheel operation) provides a stable phase reference enabling phase-coherent detection of slow spin evolution. Combined with optimized lattice symmetry and beam cooling, this approach can substantially extend the usable spin coherence time, with values approaching 10^5 s appearing realistic within existing accelerator technology. The resulting readout supports optimal slope-based estimation with T^{-3/2} statistical scaling while eliminating the efficiency penalties inherent to scattering-based polarimetry. For storage-ring EDM experiments, this combination enables sensitivity approaching the level expected within the Standard Model. More broadly, the method establishes a general phase-coherent architecture for collective spin measurements in storage rings, adapting resonant sensing concepts from axion dark-matter searches to charged-particle precision experiments.

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arXiv2026

Mesogenesis through the Ephemeral Dark Decay of Beauty

Mesogenesis provides a path for generating the baryon asymmetry of the Universe, using only the CP violation furnished by the Standard Model in the decay of $B$ mesons. While this is an intriguing possibility, it is largely constrained by the data on $B$ meson branching fractions into baryons and missing energy carried into the dark sector. We point out that it is possible to make this branching fraction dominant only in the early Universe, through an ultralight scalar coupled to the dark sector and the Standard Model leptons. A scenario is examined where the thermal density of muons in the early Universe temporarily lowers the mass of a dark fermion, allowing for efficient $B$ meson decays. This `dark' decay channel is shut off later when the muon number density falls, making the scenario compatible with flavor data. Our model can be consistent with the LHC constraints on color-charged heavy bosons required to implement Mesogenesis; such states may be discovered in the future runs as their masses cannot be far above the current bounds. We also outline other possible signals, which can arise in future displaced vertex searches, long range force searches, and observations of neutron star binary mergers.

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arXiv2026

Weak Charge Form Factor Determination at the Electron-Ion Collider

Determining the weak charge form factor, $F_W(Q^2)$, of nuclei over a continuous range of momentum transfers, $0\lesssim Q^2 \lesssim 0.1$ GeV$^2$, is essential for mapping out the distribution of neutrons in nuclei. The neutron density distribution has significant implications for a broad range of areas, including studies of nuclear structure, neutron stars, and physics beyond the Standard Model. Currently, our knowledge of $F_W(Q^2)$ comes primarily from fixed target experiments that measure the parity-violating asymmetry in coherent elastic electron-ion scattering. Fixed target experiments, such as CREX and PREX-1,2, have provided high-precision weak charge form factor extractions for the $^{48}{\rm Ca}$ and $^{208}{\rm Pb}$ nuclei, respectively. However, a major limitation of fixed target experiments is that they each provide data only at a single value of $Q^2$. With the proposed Electron-Ion Collider (EIC) on the horizon, we explore its potential to impact the determination of the weak charge form factor. While it cannot compete with the precision of fixed target experiments, it can provide data over a wide and continuous range of $Q^2$ values, and for a wide variety of nuclei. We show that with data corresponding to an integrated luminosity of ${\cal L} \sim $ 500/$A$ fb$^{-1}$, where $A$ is the nucleus atomic weight, the EIC can significantly impact constraints by lifting degeneracies in theoretical models of the neutron density distribution. Ensuring EIC detector coverage at low $Q^2$ and large negative pseudorapidities will be essential for such $F_W(Q^2)$ measurements.

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arXiv2026

Cosmic Axions Revealed via Amplified Modulation of Ellipticity of Laser (CARAMEL)

We propose a new axion dark matter detection strategy that employs optical readout of laser-beam ellipticity modulations caused by axion-induced electric fields in a microwave cavity, using electro-optic (EO) crystals, enhanced by externally injected radio-frequency (rf) power. Building upon the variance-based probing method~\cite{Omarov_2023}, we extend this concept to the optical domain: a weak probe laser interacts with an EO crystal coupled to the resonant microwave cavity field at cryogenic temperatures, and the axion-induced electric field is revealed through induced ellipticity. The injected rf signal coherently interferes with that of the axion field, amplifying the optical response and significantly improving sensitivity. While our EO-based method employs a Fabry-Pérot resonator, we do not require Michelson interferometers. Our method hence enables compact, high-frequency axion searches across the $0.5$--$50\,\mathrm{GHz}$ range. Operating at cryogenic temperatures not only suppresses thermal backgrounds but, critically, allows the probing method to mitigate quantum noise. This approach offers a scalable path forward for axion detection over the $\sim(\text{few}--200)\,μ\mathrm{eV}$ mass range -- covering the preferred parameter space for post-inflationary Peccei--Quinn axion dark matter -- using compact, tunable systems. \noindent Published in \textit{Phys. Rev. D} \textbf{113}, 032012 (2026).\\ DOI: 10.1103/PhysRevD.113.032012. This version includes further experimental details.

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arXiv2025

Higgs Potential from Instantons

We propose that the Higgs potential, a key element in our understanding of Nature, is partially generated by the instantons of new confining dynamics, perhaps from a hidden sector. In this picture, while the Higgs itself is a fundamental field, it controls the strength of the non-perturbative interactions that give rise to its potential. We examine a simple setup in which this instanton contribution is augmented by a quartic term, which is sufficient for a realistic electroweak symmetry breaking mechanism. The minimum of the potential is given by the Lambert $W_0$ function, with these assumptions. We discuss the predictions of this model and how it may be tested through measurements of the Higgs self coupling. Given the connection with non-trivial dynamics, one may also consider the prospects of accessing hidden sector states at colliders; this seems to be typically challenging in our setup. Symmetry restoration in the early Universe in this scenario is briefly examined. We also comment on the possible connection of our general setup with recent work on the physics of field space end points.

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arXiv2025

Astrophysical Consequences of an Electroweak $η_{\rm w}$ Pseudo-Scalar

Recently, it has been suggested that the spectrum of physical states in the Standard Model may include an ultralight pseudo-scalar, denoted by $η_{\rm w}$, in analogy with the $η'$ state arising from the strong interactions. We find that typical expectations for the properties of $η_{\rm w}$ get challenged by astrophysical constraints on the couplings of ultralight bosons. Our strongest limit sets a lower bound of $\mathcal{O}({\rm 100~TeV})$ on the decay constant of the hypothesized pseudo-scalar. We also briefly discuss whether $η_{\rm w}$ could be a dark matter candidate, or the origin of dark energy, but conclude that those identifications appear unlikely. Given the important implications of a potentially overlooked $η_{\rm w}$ state for a more complete understanding of the electroweak interactions and a fundamental description of Nature, further theoretical and phenomenological investigations of this possibility and its associated physics are warranted.

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arXiv2025

Status of the Proton EDM Experiment (pEDM)

The Proton EDM Experiment (pEDM) is the first direct search for the proton electric dipole moment (EDM) with the aim of being the first experiment to probe the Standard Model (SM) prediction of any particle EDM. Phase-I of pEDM will achieve $10^{-29} e\cdot$cm, improving current indirect limits by four orders of magnitude. This will establish a new standard of precision in nucleon EDM searches and offer a unique sensitivity to better understand the Strong CP problem. The experiment is ideally positioned to explore physics beyond the Standard Model (BSM), with sensitivity to axionic dark matter via the signal of an oscillating proton EDM and across a wide mass range of BSM models from $\mathcal{O}(1\text{GeV})$ to $\mathcal{O}(10^3\text{TeV})$. Utilizing the frozen-spin technique in a highly symmetric storage ring that leverages existing infrastructure at Brookhaven National Laboratory (BNL), pEDM builds upon the technological foundation and experimental expertise of the highly successful Muon $g$$-$$2$ Experiments. With significant R\&D and prototyping already underway, pEDM is preparing a conceptual design report (CDR) to offer a cost-effective, high-impact path to discovering new sources of CP violation and advancing our understanding of fundamental physics. It will play a vital role in complementing the physics goals of the next-generation collider while simultaneously contributing to sustaining particle physics research and training early-career researchers during gaps between major collider operations.

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arXiv2025

How fast can protons decay?

Current laboratory bounds imply that protons are extremely long-lived. However, this conclusion may not hold for all time and in all of space. We find that the proton lifetime can be $\sim 15$ orders of magnitude shorter in the relatively recent past on Earth, or at the present time elsewhere in the Milky Way. A number of terrestrial and astrophysical constraints are examined and potential signals are outlined. We also sketch possible models that could lead to spatial or temporal variations in the proton lifetime. A positive signal could be compelling evidence for a new long range force of Nature, with important implications for the limitations of fundamental inferences based solely on laboratory measurements.

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arXiv2024

New Physics at the Muon (Synchrotron) Ion Collider: MuSIC for several scales

A Muon (Synchrotron) Ion Collider (MuSIC) can be the successor to the Electron-Ion Collider at Brookhaven National Laboratory, as well as the ideal demonstrator facility for a future multi-TeV Muon Collider. Besides its rich nuclear physics and Standard Model particle physics programs, in this work we show that the MuSIC with a TeV-scale muon beam offers also a unique opportunity to probe New Physics. In particular, the relevant searches have the potential to surpass current experimental limits and explore new regimes of the parameter space for a variety of Beyond the Standard Model scenarios including: lepton-flavor violating leptoquarks, muonphilic vector boson interactions, axion-like particles coupling to photons, and heavy sterile neutrinos. Depending on the particular case, the sensitivity of the searches in the MuSIC may span a wide range of energy scales, namely from sub-GeV particles to the few TeV New Physics mediators. Our analysis demonstrates that the MuSIC can strike a powerful chord in the search for New Physics, thanks to unique combination of features that amplify its capabilities.

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arXiv2024

Gravitationally Misaligned Ultralight Dark Matter and Implications for Neutron Stars

We examine the possibility that dark matter (DM) may be an ultralight scalar that was misaligned via non-minimal coupling to gravity, in the early Universe. For a certain regime of scalar masses, gravitational effects in neutron stars could place interesting bounds on the viable parameter space of the model, even in the absence of non-gravitational interactions between DM and ordinary matter.

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arXiv2024

Lepton-Flavor-Violating ALP Signals with TeV-Scale Muon Beams

We explore the feasibility of using TeV-energy muons to probe lepton-flavor-violating (LFV) processes mediated by an axion-like particle (ALP) $a$ with mass $\mathcal{O}(10~\textrm{GeV})$. We focus on $μτ$ LFV interactions and assume that the ALP is coupled to a dark state $χ$, which can be either less or more massive than $a$. Such a setup is demonstrated to be consistent with $χ$ being a candidate for dark matter, in the experimentally relevant regime of parameters. We consider the currently operating NA64-$μ$ experiment and proposed FASER$ν$2 detector as both the target and the detector for the process $μA \to τA\, a$, where $A$ is the target nucleus. We also show that a possible future active muon fixed-target experiment operating at a 3 TeV muon collider or in its preparatory phase can provide an impressive reach for the LFV process considered, with future FASER$ν$2 data providing a pilot study towards that goal. The implications of the muon anomalous magnetic moment $(g-2)_μ$ measurements for the underlying model, in case of a positive signal, are also examined, and a sample UV completion is outlined.

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arXiv2024

Flavor-Violating ALPs, Electron g-2, and the Electron-Ion Collider

We revisit the possibility that light axion-like particles (ALPs) with lepton flavor violating couplings could give significant contributions to the electron's anomalous magnetic moment $g_e-2$. Unlike flavor diagonal lepton-ALP couplings, which are exclusively axial, lepton flavor violating couplings can have arbitrary chirality. Focusing on the $e$-$τ$ ALP coupling, we find that the size of the contribution to $g_e-2$ depends strongly on the chirality of the coupling. A significant part of the parameter space for which such a coupling can explain experimental anomalies in $g_e-2$ can be probed at the Electron-Ion Collider, which is uniquely sensitive to the chirality of the coupling using the polarization of the electron beam.

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