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First-principles upper bounds on dark matter-electron scattering rates from condensed matter sum rules
Authors:
Bradford A. Barker,
Jay Epstein,
Luke James,
Yonatan Kahn,
Elizabeth A. Peterson,
Anirudh Prabhu,
Tanner Trickle,
Samuel L. Watkins
Abstract:
A wide variety of condensed matter systems are used or proposed as detectors to search for dark matter-electron scattering. In general, the scattering rate depends on detailed knowledge of the electronic properties of these systems. However, when dark matter couples to electron density, the dark matter-electron scattering rate can be related to the electron energy loss function, whose integrals ar…
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A wide variety of condensed matter systems are used or proposed as detectors to search for dark matter-electron scattering. In general, the scattering rate depends on detailed knowledge of the electronic properties of these systems. However, when dark matter couples to electron density, the dark matter-electron scattering rate can be related to the electron energy loss function, whose integrals are bounded by first-principles sum rules that rely on only a few macroscopic target properties. In this paper, we use these first-principles sum rules to derive upper bounds on the dark matter-electron scattering rate depending on only a few material properties: the plasma frequency $ω_\text{p}$, the target mass density $ρ_T$, and the static (longitudinal) dielectric function at finite momentum transfer, $\varepsilon(q, 0)$. The bulk material properties $ω_\text{p}$ and $ρ_T$ vary only over a limited range across a wide variety of materials, and to a good approximation, the generic large-$q$ dependence of $\varepsilon(q, 0)$ can be understood from a simple scaling law depending only on $ω_\text{p}$ which we verify with analytic and numerical examples. Thus, our upper bounds are largely material-agnostic, and place a fundamental limit on the sensitivity of any dark matter-electron direct detection experiment probing the coupling to electron density.
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Submitted 5 August, 2026;
originally announced August 2026.
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Correlated signals of ultralight scalar dark matter in pulsar timing
Authors:
Joshua W. Foster,
Kimberly K. Boddy,
Jeff A. Dror,
Vincent S. H. Lee,
Andrea Mitridate,
Tristan L. Smith,
Kelsie Taylor,
Tanner Trickle
Abstract:
Pulsar timing arrays (PTAs) are sensitive to ultralight dark matter (ULDM) in the $10^{-24}$-$10^{-20}\,\mathrm{eV}$ mass range, with existing datasets already probing otherwise open parameter space and future PTAs promising substantial improvements in reach. Thus far, however, PTA searches for ULDM have typically been formulated using limiting descriptions. Analyses are performed in either the fu…
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Pulsar timing arrays (PTAs) are sensitive to ultralight dark matter (ULDM) in the $10^{-24}$-$10^{-20}\,\mathrm{eV}$ mass range, with existing datasets already probing otherwise open parameter space and future PTAs promising substantial improvements in reach. Thus far, however, PTA searches for ULDM have typically been formulated using limiting descriptions. Analyses are performed in either the fully correlated limit, in which the local ULDM amplitude is shared across the array, or the fully uncorrelated limit, in which each pulsar has an independent local amplitude. Because the transition between these regimes occurs within the PTA-sensitive mass range, projected sensitivities and data-derived constraints can depend on which limiting description is assumed. For the first time, we develop a self-consistent analysis that treats the ULDM field as a Gaussian random field with finite spatial correlations, allowing the amplitude prior used in PTA signal models to interpolate continuously between the fully correlated and fully uncorrelated limits. We apply the framework to both linearly and quadratically coupled scalar ULDM, the latter including the universal gravitational signal sourced by the oscillating ULDM pressure. Pulsar-distance uncertainties are incorporated through an augmented latent-field prior, and the resulting distance-marginalized latent-amplitude distribution is represented with a normalizing-flow surrogate. We validate the method on mock PTA datasets, including blinded signal injection tests.
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Submitted 27 July, 2026;
originally announced July 2026.
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Projecting the ultimate pulsar timing sensitivity to dark matter substructure in a stochastic gravitational wave background
Authors:
Joshua W. Foster,
Tanner Trickle,
Fabrizio Vassallo
Abstract:
Pulsar timing arrays (PTAs) are sensitive to the gravitational influence of passing compact substructures, which can produce Doppler timing delays by accelerating pulsars or the Solar System barycenter, and Shapiro timing delays when passing near Earth--pulsar lines of sight. Projections for the complete PTA sensitivity to compact dark matter (DM) substructures, such as primordial black holes and…
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Pulsar timing arrays (PTAs) are sensitive to the gravitational influence of passing compact substructures, which can produce Doppler timing delays by accelerating pulsars or the Solar System barycenter, and Shapiro timing delays when passing near Earth--pulsar lines of sight. Projections for the complete PTA sensitivity to compact dark matter (DM) substructures, such as primordial black holes and axion miniclusters, are challenging due to the variety of signal types ranging from rare, nearly static encounters, to dynamic flybys, to the stochastic limit of many substructures. We address this challenge with a framework that combines Monte Carlo signal modeling and machine-learned surrogate likelihoods, enabling a unified likelihood-level analysis of signals previously treated only in simplified limiting regimes. We then use this framework to precisely assess the impact of a stochastic gravitational wave background (SGWB), for which evidence was recently found, on the PTA sensitivity to compact DM substructures. The SGWB substantially weakens the sensitivity, and we find that in even the most optimistic observing scenario only a Shapiro search retains sensitivity to subdominant DM components when assuming SGWB parameters inferred from current measurements.
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Submitted 17 June, 2026; v1 submitted 16 June, 2026;
originally announced June 2026.
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Electronic Direct Detection of Light Dark Matter with Intermediate-Mass Mediators
Authors:
Connor Stratman,
Tanner Trickle
Abstract:
Recent years have seen dramatic improvements in the sensitivity of electron-based direct detection experiments. Typically, the sensitivity to dark matter scattering is determined in the light and heavy mediator mass limits. In this paper we show that the light and heavy mediator mass limits are not separated by a single scale, but instead can be separated by up to three orders of magnitude in medi…
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Recent years have seen dramatic improvements in the sensitivity of electron-based direct detection experiments. Typically, the sensitivity to dark matter scattering is determined in the light and heavy mediator mass limits. In this paper we show that the light and heavy mediator mass limits are not separated by a single scale, but instead can be separated by up to three orders of magnitude in mediator mass for sub-GeV mass dark matter. We calculate the background-free sensitivity in Si and Ge targets, and a projected DAMIC-M sensitivity, to sub-GeV mass dark matter models with ``intermediate-mass" mediators between the light and heavy mediator limits. This allows us to determine the precise range of mediator masses that electron-based direct detection experiments are sensitive to when the dark matter relic abundance is generated via freeze-in. We make the calculations presented here publicly available in an updated release of EXCEED-DM (https://github.com/tanner-trickle/EXCEED-DM).
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Submitted 11 May, 2026;
originally announced May 2026.
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Infrared Freeze-In of Magnetic Dipole Dark Matter
Authors:
Asher Berlin,
Jae Hyeok Chang,
Tanner Trickle
Abstract:
We propose a novel mechanism for the cosmological production of keV - GeV mass dark matter that interacts with the Standard Model through a small effective magnetic dipole moment. Such an interaction can be radiatively generated if dark matter couples to heavier charged particles. Previous studies have focused on the case where these charged states are much heavier than the reheat temperature, suc…
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We propose a novel mechanism for the cosmological production of keV - GeV mass dark matter that interacts with the Standard Model through a small effective magnetic dipole moment. Such an interaction can be radiatively generated if dark matter couples to heavier charged particles. Previous studies have focused on the case where these charged states are much heavier than the reheat temperature, such that freeze-in production of dark matter is sensitive to the ultraviolet details of reheating. Here, we instead consider the possibility that these heavy states have masses comparable to the dark matter mass and are charged under a new kinetically-mixed $U(1)'$. As a result, dark matter production is dominated by the infrared freeze-in of the heavy charged states that subsequently thermalize the rest of the dark sector to a temperature much below that of the visible bath. We delineate regions of parameter space consistent with cosmological and astrophysical constraints and identify benchmark scenarios that can guide the next generation of direct detection experiments searching for spin-dependent scattering of sub-GeV dark matter.
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Submitted 8 December, 2025;
originally announced December 2025.
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A Thermal Relic Encyclopedia: Dark Matter Candidates Coupled to Quarks
Authors:
Dan Hooper,
Gordan Krnjaic,
Tanner Trickle,
Isaac R. Wang
Abstract:
Thermal freeze-out is a compelling framework for naturally generating the dark matter abundance. We systematically study a broad range of dark matter and mediator particle combinations that can viably realize thermal freeze-out, focusing on models in which the mediator couples to Standard Model quarks. In each case, we calculate the relic density and consider existing constraints from accelerators…
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Thermal freeze-out is a compelling framework for naturally generating the dark matter abundance. We systematically study a broad range of dark matter and mediator particle combinations that can viably realize thermal freeze-out, focusing on models in which the mediator couples to Standard Model quarks. In each case, we calculate the relic density and consider existing constraints from accelerators, cosmology, direct detection, and indirect detection over the full range of dark matter and mediator masses. We present an encyclopedic catalog of matrix elements, cross sections, and decay rates which can be used as a reference for future studies of dark matter phenomenology.
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Submitted 2 December, 2025;
originally announced December 2025.
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MOSAIC: Magnonic Observations of Spin-dependent Axion-like InteraCtions
Authors:
Clarence Chang,
T. J. Hobbs,
Dafei Jin,
Yi Li,
Marharyta Lisovenko,
Valentine Novosad,
Zain H. Saleem,
Tanner Trickle,
Gensheng Wang
Abstract:
We introduce an array-scalable, magnon-based detector (MOSAIC) to search for the spin-dependent interactions of electron-coupled axion dark matter. These axions can excite single magnons in magnetic targets, such as the yttrium iron garnet (YIG) spheres used here, which are subsequently sensed by the detector. For MOSAIC, this sensing is implemented by coupling the magnons in the YIG spheres to ma…
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We introduce an array-scalable, magnon-based detector (MOSAIC) to search for the spin-dependent interactions of electron-coupled axion dark matter. These axions can excite single magnons in magnetic targets, such as the yttrium iron garnet (YIG) spheres used here, which are subsequently sensed by the detector. For MOSAIC, this sensing is implemented by coupling the magnons in the YIG spheres to magnetic-field-resilient single-electron charge-qubits, whose state is then interrogated with a quantum non-demolition measurement. Using standard superconducting fabrication techniques, MOSAIC can integrate many YIG sphere-qubit sensors, forming a large detector array. We outline the detector design and operation, and determine its sensitivity to axion dark matter. We find that a detector built with available technology will exceed the sensitivity of previous ferromagnetic haloscopes, and provides a platform where further improvements in performance would search for electron-coupled axion dark matter in unexplored parameter space.
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Submitted 22 April, 2025;
originally announced April 2025.
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Determining Spin-Dependent Light Dark Matter Rates from Neutron Scattering
Authors:
Asher Berlin,
Alexander J. Millar,
Tanner Trickle,
Kevin Zhou
Abstract:
The scattering and absorption rates of light dark matter with electron spin-dependent interactions depend on the target's spin response. We show how this response is encoded by the target's dynamical magnetic susceptibility, which can be measured using neutron scattering. We directly use existing neutron scattering data to compute the dark matter scattering rate in a candidate target material, fin…
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The scattering and absorption rates of light dark matter with electron spin-dependent interactions depend on the target's spin response. We show how this response is encoded by the target's dynamical magnetic susceptibility, which can be measured using neutron scattering. We directly use existing neutron scattering data to compute the dark matter scattering rate in a candidate target material, finding close agreement with the previous first-principles calculation at MeV dark matter masses. Complementary experiments and measurements can extend the reach of this technique to other dark matter models and masses, and identify promising target materials for future experiments.
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Submitted 21 August, 2025; v1 submitted 3 April, 2025;
originally announced April 2025.
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Piezoelectric Bulk Acoustic Resonators For Dark Photon Detection
Authors:
Tanner Trickle
Abstract:
The kinetically mixed dark photon is a simple, testable dark matter candidate with strong theoretical motivation. Detecting the feeble electric field dark photon dark matter produces requires extremely sensitive detectors. Bulk acoustic resonators (BARs), with their exceptionally high-quality phonon modes, are capable of achieving incredible sensitivity to gravitational waves in the MHz to GHz fre…
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The kinetically mixed dark photon is a simple, testable dark matter candidate with strong theoretical motivation. Detecting the feeble electric field dark photon dark matter produces requires extremely sensitive detectors. Bulk acoustic resonators (BARs), with their exceptionally high-quality phonon modes, are capable of achieving incredible sensitivity to gravitational waves in the MHz to GHz frequency range. The BAR phonons are typically read out by detecting the electric field generated by the BAR materials' piezoelectricity. Here we show that this piezoelectricity also rewards such detectors sensitivity to dark photon dark matter, as the dark electric field can resonantly excite BAR phonons. A single 10 g piezoelectric BAR in a large, cold, environment can be orders of magnitude more sensitive to the kinetic mixing parameter than any current experiment, with only a month-long exposure and thermally-limited backgrounds.
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Submitted 9 January, 2025;
originally announced January 2025.
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Listening For New Physics With Quantum Acoustics
Authors:
Ryan Linehan,
Tanner Trickle,
Christopher R. Conner,
Sohitri Ghosh,
Tongyan Lin,
Mukul Sholapurkar,
Andrew N. Cleland
Abstract:
We present a novel application of a qubit-coupled phonon detector to search for new physics, e.g., ultralight dark matter (DM) and high-frequency gravitational waves. The detector, motivated by recent advances in quantum acoustics, is composed of superconducting transmon qubits coupled to high-overtone bulk acoustic resonators ($h$BARs) and operates in the GHz - 10 GHz frequency range. New physics…
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We present a novel application of a qubit-coupled phonon detector to search for new physics, e.g., ultralight dark matter (DM) and high-frequency gravitational waves. The detector, motivated by recent advances in quantum acoustics, is composed of superconducting transmon qubits coupled to high-overtone bulk acoustic resonators ($h$BARs) and operates in the GHz - 10 GHz frequency range. New physics can excite $O(10 \, μ\text{eV})$ phonons within the $h$BAR, which are then converted to qubit excitations via a transducer. We detail the design, operation, backgrounds, and expected sensitivity of a prototype detector, as well as a next-generation detector optimized for new physics signals. We find that a future detector can complement current haloscope experiments in the search for both dark photon DM and high-frequency gravitational waves. Lastly we comment on such a detector's ability to operate as a $10 \, μ\text{eV}$ threshold athermal phonon sensor for sub-GeV DM detection.
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Submitted 22 October, 2024;
originally announced October 2024.
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The Non-Relativistic Effective Field Theory Of Dark Matter-Electron Interactions
Authors:
Gordan Krnjaic,
Duncan Rocha,
Tanner Trickle
Abstract:
Electronic excitations in atomic, molecular, and crystal targets are at the forefront of the ongoing search for light, sub-GeV dark matter (DM). In many light DM-electron interactions the energy and momentum deposited is much smaller than the electron mass, motivating a non-relativistic (NR) description of the electron. Thus, for any target, light DM-electron phenomenology relies on understanding…
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Electronic excitations in atomic, molecular, and crystal targets are at the forefront of the ongoing search for light, sub-GeV dark matter (DM). In many light DM-electron interactions the energy and momentum deposited is much smaller than the electron mass, motivating a non-relativistic (NR) description of the electron. Thus, for any target, light DM-electron phenomenology relies on understanding the interactions between the DM and electron in the NR limit. In this work we derive the NR effective field theory (EFT) of general DM-electron interactions from a top-down perspective, starting from general high-energy DM-electron interaction Lagrangians. This provides an explicit connection between high-energy theories and their low-energy phenomenology in electron excitation based experiments. Furthermore, we derive Feynman rules for the DM-electron NR EFT, allowing observables to be computed diagrammatically, which can systematically explain the presence of in-medium screening effects in general DM models. We use these Feynman rules to compute absorption, scattering, and dark Thomson scattering rates for a wide variety of high-energy DM models.
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Submitted 16 April, 2025; v1 submitted 19 July, 2024;
originally announced July 2024.
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Physical Signatures of Fermion-Coupled Axion Dark Matter
Authors:
Asher Berlin,
Alexander J. Millar,
Tanner Trickle,
Kevin Zhou
Abstract:
In the presence of axion dark matter, fermion spins experience an "axion wind" torque and an "axioelectric" force. We investigate new experimental probes of these effects and find that magnetized analogs of multilayer dielectric haloscopes can explore orders of magnitude of new parameter space for the axion-electron coupling. We also revisit the calculation of axion absorption into in-medium excit…
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In the presence of axion dark matter, fermion spins experience an "axion wind" torque and an "axioelectric" force. We investigate new experimental probes of these effects and find that magnetized analogs of multilayer dielectric haloscopes can explore orders of magnitude of new parameter space for the axion-electron coupling. We also revisit the calculation of axion absorption into in-medium excitations, showing that axioelectric absorption is screened in spin-polarized targets, and axion wind absorption can be characterized in terms of a magnetic energy loss function. Finally, our detailed theoretical treatment allows us to critically examine recent claims in the literature. We find that axioelectric corrections to electronic energy levels are smaller than previously estimated and that the purported electron electric dipole moment due to a constant axion field is entirely spurious.
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Submitted 8 June, 2024; v1 submitted 18 December, 2023;
originally announced December 2023.
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Searching for High Frequency Gravitational Waves with Phonons
Authors:
Yonatan Kahn,
Jan Schütte-Engel,
Tanner Trickle
Abstract:
The gravitational wave (GW) spectrum at frequencies above a kHz is a largely unexplored frontier. We show that detectors with sensitivity to single-phonon excitations in crystal targets can search for GWs with frequencies, $\mathrm{THz} \lesssim f \lesssim 100 \, \mathrm{THz}$, corresponding to the range of optical phonon energies, $\mathrm{meV} \lesssim ω\lesssim 100 \, \mathrm{meV}$. Such detect…
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The gravitational wave (GW) spectrum at frequencies above a kHz is a largely unexplored frontier. We show that detectors with sensitivity to single-phonon excitations in crystal targets can search for GWs with frequencies, $\mathrm{THz} \lesssim f \lesssim 100 \, \mathrm{THz}$, corresponding to the range of optical phonon energies, $\mathrm{meV} \lesssim ω\lesssim 100 \, \mathrm{meV}$. Such detectors are already being built to search for light dark matter (DM), and therefore sensitivity to high-frequency GWs will be achieved as a byproduct. We begin by deriving the absorption rate of a general GW signal into single phonons. We then focus on carefully defining the detector sensitivity to monochromatic and chirp signals, and compute the detector sensitivity for many proposed light DM detection targets. The detector sensitivity is then compared to the signal strength of candidate high-frequency GW sources, e.g., superradiant annihilation and black hole inspiral, as well as other recent detector proposals in the $\mathrm{MHz} \lesssim f \lesssim 100 \, \mathrm{THz}$ frequency range. With a judicious choice of target materials, a collection of detectors could optimistically achieve sensitivities to monochromatic signals with $h_0 \sim 10^{-23} - 10^{-25}$ over $\mathrm{THz} \lesssim f \lesssim 100 \, \mathrm{THz}$.
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Submitted 28 November, 2023;
originally announced November 2023.
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Effective Field Theory for Dark Matter Absorption on Single Phonons
Authors:
Andrea Mitridate,
Kris Pardo,
Tanner Trickle,
Kathryn M. Zurek
Abstract:
Single phonon excitations, with energies in the $1-100 \, \text{meV}$ range, are a powerful probe of light dark matter (DM). Utilizing effective field theory, we derive a framework to compute DM absorption rates into single phonons starting from general DM-electron, proton, and neutron interactions. We apply the framework to a variety of DM models: Yukawa coupled scalars, axionlike particles (ALPs…
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Single phonon excitations, with energies in the $1-100 \, \text{meV}$ range, are a powerful probe of light dark matter (DM). Utilizing effective field theory, we derive a framework to compute DM absorption rates into single phonons starting from general DM-electron, proton, and neutron interactions. We apply the framework to a variety of DM models: Yukawa coupled scalars, axionlike particles (ALPs) with derivative interactions, and vector DM coupling via gauge interactions or Standard Model electric and magnetic dipole moments. We find that GaAs or $\text{Al}_2\text{O}_3$ targets can set powerful constraints on a $U(1)_{B-L}$ model, and targets with electronic spin ordering are similarly sensitive to DM coupling to the electron magnetic dipole moment. Lastly, we make the code, \textsf{PhonoDark-abs} (an extension of the existing \textsf{PhonoDark} code which computes general DM-single phonon scattering rates), publicly available.
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Submitted 11 August, 2023;
originally announced August 2023.
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PTArcade
Authors:
Andrea Mitridate,
David Wright,
Richard von Eckardstein,
Tobias Schröder,
Jonathan Nay,
Ken Olum,
Kai Schmitz,
Tanner Trickle
Abstract:
This is a lightweight manual for PTArcade, a wrapper of ENTERPRISE and ceffyl that allows for easy implementation of new-physics searches in PTA data. In this manual, we describe how to get PTArcade installed (either on your local machine or an HPC cluster). We discuss how to define a stochastic or deterministic signal and how PTArcade implements these signals in PTA-analysis pipelines. Finally, w…
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This is a lightweight manual for PTArcade, a wrapper of ENTERPRISE and ceffyl that allows for easy implementation of new-physics searches in PTA data. In this manual, we describe how to get PTArcade installed (either on your local machine or an HPC cluster). We discuss how to define a stochastic or deterministic signal and how PTArcade implements these signals in PTA-analysis pipelines. Finally, we show how to handle and analyze the PTArcade output using a series of utility functions that come together with PTArcade.
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Submitted 28 June, 2023;
originally announced June 2023.
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The NANOGrav 15-year Data Set: Search for Signals from New Physics
Authors:
Adeela Afzal,
Gabriella Agazie,
Akash Anumarlapudi,
Anne M. Archibald,
Zaven Arzoumanian,
Paul T. Baker,
Bence Bécsy,
Jose Juan Blanco-Pillado,
Laura Blecha,
Kimberly K. Boddy,
Adam Brazier,
Paul R. Brook,
Sarah Burke-Spolaor,
Rand Burnette,
Robin Case,
Maria Charisi,
Shami Chatterjee,
Katerina Chatziioannou,
Belinda D. Cheeseboro,
Siyuan Chen,
Tyler Cohen,
James M. Cordes,
Neil J. Cornish,
Fronefield Crawford,
H. Thankful Cromartie
, et al. (98 additional authors not shown)
Abstract:
The 15-year pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) shows positive evidence for the presence of a low-frequency gravitational-wave (GW) background. In this paper, we investigate potential cosmological interpretations of this signal, specifically cosmic inflation, scalar-induced GWs, first-order phase transitions, cosmic string…
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The 15-year pulsar timing data set collected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) shows positive evidence for the presence of a low-frequency gravitational-wave (GW) background. In this paper, we investigate potential cosmological interpretations of this signal, specifically cosmic inflation, scalar-induced GWs, first-order phase transitions, cosmic strings, and domain walls. We find that, with the exception of stable cosmic strings of field theory origin, all these models can reproduce the observed signal. When compared to the standard interpretation in terms of inspiraling supermassive black hole binaries (SMBHBs), many cosmological models seem to provide a better fit resulting in Bayes factors in the range from 10 to 100. However, these results strongly depend on modeling assumptions about the cosmic SMBHB population and, at this stage, should not be regarded as evidence for new physics. Furthermore, we identify excluded parameter regions where the predicted GW signal from cosmological sources significantly exceeds the NANOGrav signal. These parameter constraints are independent of the origin of the NANOGrav signal and illustrate how pulsar timing data provide a new way to constrain the parameter space of these models. Finally, we search for deterministic signals produced by models of ultralight dark matter (ULDM) and dark matter substructures in the Milky Way. We find no evidence for either of these signals and thus report updated constraints on these models. In the case of ULDM, these constraints outperform torsion balance and atomic clock constraints for ULDM coupled to electrons, muons, or gluons.
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Submitted 28 June, 2023;
originally announced June 2023.
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Absorption of Axion Dark Matter in a Magnetized Medium
Authors:
Asher Berlin,
Tanner Trickle
Abstract:
Detection of axion dark matter heavier than a meV is hindered by its small wavelength, which limits the useful volume of traditional experiments. This problem can be avoided by directly detecting in-medium excitations, whose $\sim \text{meV} - \text{eV}$ energies are decoupled from the detector size. We show that for any target inside a magnetic field, the absorption rate of electromagnetically-co…
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Detection of axion dark matter heavier than a meV is hindered by its small wavelength, which limits the useful volume of traditional experiments. This problem can be avoided by directly detecting in-medium excitations, whose $\sim \text{meV} - \text{eV}$ energies are decoupled from the detector size. We show that for any target inside a magnetic field, the absorption rate of electromagnetically-coupled axions into in-medium excitations is determined by the dielectric function. As a result, the plethora of candidate targets previously identified for sub-GeV dark matter searches can be repurposed as broadband axion detectors. We find that a $\text{kg} \cdot \text{yr}$ exposure with noise levels comparable to recent measurements is sufficient to probe parameter space currently unexplored by laboratory tests. Noise reduction by only a few orders of magnitude can enable sensitivity to the QCD axion in the $\sim 10 \ \text{meV} - 10 \ \text{eV}$ mass range.
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Submitted 9 May, 2023;
originally announced May 2023.
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Absorption of Vector Dark Matter Beyond Kinetic Mixing
Authors:
Gordan Krnjaic,
Tanner Trickle
Abstract:
Massive vector particles are minimal dark matter candidates that motivate a wide range of laboratory searches, primarily exploiting a postulated kinetic mixing with the photon. However, depending on the high energy field content, the dominant vector dark matter (VDM) coupling to visible particles may arise at higher operator dimension, motivating efforts to predict direct detection rates for more…
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Massive vector particles are minimal dark matter candidates that motivate a wide range of laboratory searches, primarily exploiting a postulated kinetic mixing with the photon. However, depending on the high energy field content, the dominant vector dark matter (VDM) coupling to visible particles may arise at higher operator dimension, motivating efforts to predict direct detection rates for more general interactions. Here we present the first calculation of VDM absorption through its coupling to electron electric (EDM) or magnetic (MDM) dipole moments, which can be realized in minimal extensions to the Standard Model and yield the observed abundance through a variety of mechanisms across the eV\,-\,MeV mass range. We compute the absorption rate of the MDM and EDM models for a general target, and then derive direct detection constraints from targets currently in use: Si and Ge crystals and Xe and Ar atoms. We find that current experiments are already sensitive to VDM parameter space corresponding to a cosmological freeze-in scenario, and future experiments will be able to completely exclude MDM and EDM freeze-in models with reheat temperatures below the electroweak scale. Additionally, we find that while constraints on the MDM interaction can be related to constraints on axion-like particles, the same is not true for the EDM model, so the latter absorption rate must be computed from first principles. To achieve this, we update the publicly available program EXCEED-DM to perform these new calculations.
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Submitted 15 August, 2023; v1 submitted 20 March, 2023;
originally announced March 2023.
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EXCEED-DM: Extended Calculation of Electronic Excitations for Direct Detection of Dark Matter
Authors:
Tanner Trickle
Abstract:
Direct detection experiments utilizing electronic excitations are spearheading the search for light, sub-GeV, dark matter (DM). It is thus crucial to have accurate predictions for any DM-electron interaction rate in this regime. EXCEED-DM (EXtended Calculation of Electronic Excitations for Direct detection of Dark Matter) computes DM-electron interaction rates with inputs from a variety of ab init…
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Direct detection experiments utilizing electronic excitations are spearheading the search for light, sub-GeV, dark matter (DM). It is thus crucial to have accurate predictions for any DM-electron interaction rate in this regime. EXCEED-DM (EXtended Calculation of Electronic Excitations for Direct detection of Dark Matter) computes DM-electron interaction rates with inputs from a variety of ab initio electronic structure calculations. The purpose of this manuscript is two-fold: to familiarize the user with the formalism and inputs of EXCEED-DM, and perform novel calculations to showcase what EXCEED-DM is capable of. We perform four calculations which extend previous results: the scattering rate in the dark photon model, screened with the numerically computed dielectric function, the scattering rate with an interaction potential dependent on the electron velocity, an extended absorption calculation for scalar, pseudoscalar, and vector DM, and the annual modulation of the scattering rate in the dark photon model.
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Submitted 15 March, 2023; v1 submitted 26 October, 2022;
originally announced October 2022.
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Constraining Fundamental Constant Variations from Ultralight Dark Matter with Pulsar Timing Arrays
Authors:
David E. Kaplan,
Andrea Mitridate,
Tanner Trickle
Abstract:
Pulsar Timing Arrays (PTAs) are exceptionally sensitive detectors in the frequency band $\text{nHz} \lesssim f \lesssim μ\text{Hz}$. Ultralight dark matter (ULDM), with mass in the range $10^{-23}\,\text{eV} \lesssim m_φ\lesssim 10^{-20}\,\text{eV}$, is one class of DM models known to generate signals in this frequency window. While purely gravitational signatures of ULDM have been studied previou…
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Pulsar Timing Arrays (PTAs) are exceptionally sensitive detectors in the frequency band $\text{nHz} \lesssim f \lesssim μ\text{Hz}$. Ultralight dark matter (ULDM), with mass in the range $10^{-23}\,\text{eV} \lesssim m_φ\lesssim 10^{-20}\,\text{eV}$, is one class of DM models known to generate signals in this frequency window. While purely gravitational signatures of ULDM have been studied previously, in this work we consider two signals in PTAs which arise in presence of direct couplings between ULDM and ordinary matter. These couplings induce variations in fundamental constants, i.e., particle masses and couplings. These variations can alter the moment of inertia of pulsars, inducing pulsar spin fluctuations via conservation of angular momentum, or induce apparent timing residuals due to reference clock shifts. By using mock data mimicking current PTA datasets, we show that PTA experiments outperform torsion balance and atomic clock constraints for ULDM coupled to electrons, muons, or gluons. In the case of coupling to quarks or photons, we find that PTAs and atomic clocks set similar constraints. Additionally, we discuss how future PTAs can further improve these constraints, and detail the unique properties of these signals relative to the previously studied effects of ULDM on PTAs.
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Submitted 13 May, 2022;
originally announced May 2022.
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Snowmass2021 Cosmic Frontier: The landscape of low-threshold dark matter direct detection in the next decade
Authors:
Rouven Essig,
Graham K. Giovanetti,
Noah Kurinsky,
Dan McKinsey,
Karthik Ramanathan,
Kelly Stifter,
Tien-Tien Yu,
A. Aboubrahim,
D. Adams,
D. S. M. Alves,
T. Aralis,
H. M. Araújo,
D. Baxter,
K. V. Berghaus,
A. Berlin,
C. Blanco,
I. M. Bloch,
W. M. Bonivento,
R. Bunker,
S. Burdin,
A. Caminata,
M. C. Carmona-Benitez,
L. Chaplinsky,
T. Y. Chen,
S. E. Derenzo
, et al. (68 additional authors not shown)
Abstract:
The search for particle-like dark matter with meV-to-GeV masses has developed rapidly in the past few years. We summarize the science case for these searches, the recent progress, and the exciting upcoming opportunities. Funding for Research and Development and a portfolio of small dark matter projects will allow the community to capitalize on the substantial recent advances in theory and experime…
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The search for particle-like dark matter with meV-to-GeV masses has developed rapidly in the past few years. We summarize the science case for these searches, the recent progress, and the exciting upcoming opportunities. Funding for Research and Development and a portfolio of small dark matter projects will allow the community to capitalize on the substantial recent advances in theory and experiment and probe vast regions of unexplored dark-matter parameter space in the coming decade.
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Submitted 27 April, 2023; v1 submitted 15 March, 2022;
originally announced March 2022.
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Snowmass White Paper: Light Dark Matter Direct Detection at the Interface With Condensed Matter Physics
Authors:
Andrea Mitridate,
Tanner Trickle,
Zhengkang Zhang,
Kathryn M. Zurek
Abstract:
Direct detection experiments for light (sub-GeV) dark matter are making enormous leaps in reaching previously unexplored theory space. The need for accurate characterizations of target responses has led to a growing interplay between particle and condensed matter physics. This white paper summarizes recent progress on direct detection calculations that utilize state-of-the-art numerical tools in c…
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Direct detection experiments for light (sub-GeV) dark matter are making enormous leaps in reaching previously unexplored theory space. The need for accurate characterizations of target responses has led to a growing interplay between particle and condensed matter physics. This white paper summarizes recent progress on direct detection calculations that utilize state-of-the-art numerical tools in condensed matter physics and effective field theory techniques. These new results provide the theoretical framework for interpreting ongoing and planned experiments using electronic and collective excitations, and for optimizing future searches.
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Submitted 14 March, 2022;
originally announced March 2022.
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Dark Matter Direct Detection in Materials with Spin-Orbit Coupling
Authors:
Hsiao-Yi Chen,
Andrea Mitridate,
Tanner Trickle,
Zhengkang Zhang,
Marco Bernardi,
Kathryn M. Zurek
Abstract:
Semiconductors with $\mathcal{O}(\text{meV})$ band gaps have been shown to be promising targets to search for sub-MeV mass dark matter (DM). In this paper we focus on a class of materials where such narrow band gaps arise naturally as a consequence of spin-orbit coupling (SOC). Specifically, we are interested in computing DM-electron scattering and absorption rates in these materials using state-o…
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Semiconductors with $\mathcal{O}(\text{meV})$ band gaps have been shown to be promising targets to search for sub-MeV mass dark matter (DM). In this paper we focus on a class of materials where such narrow band gaps arise naturally as a consequence of spin-orbit coupling (SOC). Specifically, we are interested in computing DM-electron scattering and absorption rates in these materials using state-of-the-art density functional theory (DFT) techniques. To do this, we extend the DM interaction rate calculation to include SOC effects which necessitates a generalization to spin-dependent wave functions. We apply our new formalism to calculate limits for several DM benchmark models using an example ZrTe$_{5}$ target and show that the inclusion of SOC can substantially alter projected constraints.
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Submitted 23 February, 2022;
originally announced February 2022.
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Radiative Semileptonic $\bar{B}$ Decays
Authors:
Michele Papucci,
Tanner Trickle,
Mark B. Wise
Abstract:
We consider the form factors for the radiative semileptonic decays $\bar{B}(v) \rightarrow D^{(*)}(v') \ell {\bar ν}_\ell γ$ in the kinematic region where the photon momentum, $k$, is small enough that heavy quark symmetry (HQS) can be applied without the radiated photon changing the heavy quark velocity (i.e., $v^{(\prime)} \cdot k < m_{(b,c)}$). We find that HQS is remarkably powerful, leaving o…
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We consider the form factors for the radiative semileptonic decays $\bar{B}(v) \rightarrow D^{(*)}(v') \ell {\bar ν}_\ell γ$ in the kinematic region where the photon momentum, $k$, is small enough that heavy quark symmetry (HQS) can be applied without the radiated photon changing the heavy quark velocity (i.e., $v^{(\prime)} \cdot k < m_{(b,c)}$). We find that HQS is remarkably powerful, leaving only four new undetermined form factors at leading order in $1/m_{(b,c)}$. In addition, one of them is fixed in terms of the leading order Isgur-Wise function in the kinematic region, $v^{(\prime)}\cdot k < Λ_\text{QCD}$.
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Submitted 25 October, 2021;
originally announced October 2021.
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Dark Matter Absorption via Electronic Excitations
Authors:
Andrea Mitridate,
Tanner Trickle,
Zhengkang Zhang,
Kathryn M. Zurek
Abstract:
We revisit the calculation of bosonic dark matter absorption via electronic excitations. Working in an effective field theory framework and consistently taking into account in-medium effects, we clarify the relation between dark matter and photon absorption. As is well-known, for vector (dark photon) and pseudoscalar (axion-like particle) dark matter, the absorption rates can be simply related to…
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We revisit the calculation of bosonic dark matter absorption via electronic excitations. Working in an effective field theory framework and consistently taking into account in-medium effects, we clarify the relation between dark matter and photon absorption. As is well-known, for vector (dark photon) and pseudoscalar (axion-like particle) dark matter, the absorption rates can be simply related to the target material's optical properties. However, this is not the case for scalar dark matter, where the dominant contribution comes from a different operator than the one contributing to photon absorption, which is formally next-to-leading-order and does not suffer from in-medium screening. It is therefore imperative to have reliable first-principles numerical calculations and/or semi-analytic modeling in order to predict the detection rate. We present updated sensitivity projections for semiconductor crystal and superconductor targets for ongoing and proposed direct detection experiments.
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Submitted 23 June, 2021;
originally announced June 2021.
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Extended Calculation of Dark Matter-Electron Scattering in Crystal Targets
Authors:
Sinéad M. Griffin,
Katherine Inzani,
Tanner Trickle,
Zhengkang Zhang,
Kathryn M. Zurek
Abstract:
We extend the calculation of dark matter direct detection rates via electronic transitions in general dielectric crystal targets, combining state-of-the-art density functional theory calculations of electronic band structures and wave functions near the band gap, with semi-analytic approximations to include additional states farther away from the band gap. We show, in particular, the importance of…
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We extend the calculation of dark matter direct detection rates via electronic transitions in general dielectric crystal targets, combining state-of-the-art density functional theory calculations of electronic band structures and wave functions near the band gap, with semi-analytic approximations to include additional states farther away from the band gap. We show, in particular, the importance of all-electron reconstruction for recovering large momentum components of electronic wave functions, which, together with the inclusion of additional states, has a significant impact on direct detection rates, especially for heavy mediator models and at $\mathcal{O}(10\,\text{eV})$ and higher energy depositions. Applying our framework to silicon and germanium (that have been established already as sensitive dark matter detectors), we find that our extended calculations can appreciably change the detection prospects. Our calculational framework is implemented in an open-source program $\texttt{EXCEED-DM}$ (EXtended Calculation of Electronic Excitations for Direct detection of Dark Matter), to be released in an upcoming publication.
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Submitted 11 May, 2021;
originally announced May 2021.
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Bayesian Forecasts for Dark Matter Substructure Searches with Mock Pulsar Timing Data
Authors:
Vincent S. H. Lee,
Stephen R. Taylor,
Tanner Trickle,
Kathryn M. Zurek
Abstract:
Dark matter substructure, such as primordial black holes (PBHs) and axion miniclusters, can induce phase shifts in pulsar timing arrays (PTAs) measurements due to gravitational effects. In order to gain a more realistic forecast for the detectability of such models of dark matter with PTAs, we propose a Bayesian inference framework to search for phase shifts generated by PBHs and perform the analy…
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Dark matter substructure, such as primordial black holes (PBHs) and axion miniclusters, can induce phase shifts in pulsar timing arrays (PTAs) measurements due to gravitational effects. In order to gain a more realistic forecast for the detectability of such models of dark matter with PTAs, we propose a Bayesian inference framework to search for phase shifts generated by PBHs and perform the analysis on mock PTA data. For most PBH masses the constraints on the dark matter abundance agree with previous (frequentist) analyses (without mock data) to $\mathcal{O}(1)$ factors. This further motivates a dedicated search for PBHs (and dense small scale structures) in the mass range from $10^{-8}\,M_{\odot}$ to well above $10^2\,M_{\odot}$ with the Square Kilometer Array. Moreover, with a more optimistic set of timing parameters, future PTAs are predicted to constrain PBHs down to $10^{-11}\,M_{\odot}$. Lastly, we discuss the impact of backgrounds, such as Supermassive Black Hole Mergers, on detection prospects, suggesting a future program to separate a dark matter signal from other astrophysical sources.
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Submitted 1 October, 2021; v1 submitted 12 April, 2021;
originally announced April 2021.
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Directional Detectability of Dark Matter With Single Phonon Excitations: Target Comparison
Authors:
Ahmet Coskuner,
Tanner Trickle,
Zhengkang Zhang,
Kathryn M. Zurek
Abstract:
Single phonon excitations are sensitive probes of light dark matter in the keV-GeV mass window. For anisotropic target materials, the signal depends on the direction of the incoming dark matter wind and exhibits a daily modulation. We discuss in detail the various sources of anisotropy, and carry out a comparative study of 26 crystal targets, focused on sub-MeV dark matter benchmarks. We compute t…
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Single phonon excitations are sensitive probes of light dark matter in the keV-GeV mass window. For anisotropic target materials, the signal depends on the direction of the incoming dark matter wind and exhibits a daily modulation. We discuss in detail the various sources of anisotropy, and carry out a comparative study of 26 crystal targets, focused on sub-MeV dark matter benchmarks. We compute the modulation reach for the most promising targets, corresponding to the cross section where the daily modulation can be observed for a given exposure, which allows us to combine the strength of DM-phonon couplings and the amplitude of daily modulation. We highlight Al$_2$O$_3$ (sapphire), CaWO$_4$ and h-BN (hexagonal boron nitride) as the best polar materials for recovering a daily modulation signal, which feature $\mathcal{O}(1 - 100)\%$ variations of detection rates throughout the day, depending on the dark matter mass and interaction. The directional nature of single phonon excitations offers a useful handle to mitigate backgrounds, which is crucial for fully realizing the discovery potential of near future experiments.
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Submitted 11 January, 2022; v1 submitted 18 February, 2021;
originally announced February 2021.
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Probing Small-Scale Power Spectra with Pulsar Timing Arrays
Authors:
Vincent S. H. Lee,
Andrea Mitridate,
Tanner Trickle,
Kathryn M. Zurek
Abstract:
Models of Dark Matter (DM) can leave unique imprints on the Universe's small scale structure by boosting density perturbations on small scales. We study the capability of Pulsar Timing Arrays to search for, and constrain, subhalos from such models. The models of DM we consider are ordinary adiabatic perturbations in $Λ$CDM, QCD axion miniclusters, models with early matter domination, and vector DM…
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Models of Dark Matter (DM) can leave unique imprints on the Universe's small scale structure by boosting density perturbations on small scales. We study the capability of Pulsar Timing Arrays to search for, and constrain, subhalos from such models. The models of DM we consider are ordinary adiabatic perturbations in $Λ$CDM, QCD axion miniclusters, models with early matter domination, and vector DM produced during inflation. We show that $Λ$CDM, largely due to tidal stripping effects in the Milky Way, is out of reach for PTAs (as well as every other probe proposed to detect DM small scale structure). Axion miniclusters may be within reach, although this depends crucially on whether the axion relic density is dominated by the misalignment or string contribution. Models where there is matter domination with a reheat temperature below 1 GeV may be observed with future PTAs. Lastly, vector DM produced during inflation can be detected if it is lighter than $10^{-16} \,{\rm GeV}$. We also make publicly available a Python Monte Carlo tool for generating the PTA time delay signal from any model of DM substructure.
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Submitted 17 December, 2020;
originally announced December 2020.
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Effective Field Theory of Dark Matter Direct Detection With Collective Excitations
Authors:
Tanner Trickle,
Zhengkang Zhang,
Kathryn M. Zurek
Abstract:
We develop a framework for computing light dark matter direct detection rates through single phonon and magnon excitations via general effective operators. Our work generalizes previous calculations focused on spin-independent interactions involving the total nucleon and electron numbers $N$ (the usual route to excite phonons) and spin-dependent interactions involving the total electron spin $S$ (…
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We develop a framework for computing light dark matter direct detection rates through single phonon and magnon excitations via general effective operators. Our work generalizes previous calculations focused on spin-independent interactions involving the total nucleon and electron numbers $N$ (the usual route to excite phonons) and spin-dependent interactions involving the total electron spin $S$ (the usual route to excite magnons), leading us to identify new responses involving the orbital angular momenta $L$, as well as spin-orbit couplings $L\otimes S$ in the target. All four types of responses can excite phonons, while couplings to electron's $S$ and $L$ can also excite magnons. We apply the effective field theory approach to a set of well-motivated relativistic benchmark models, including (pseudo-)scalar mediated interactions, and models where dark matter interacts via a multipole moment, such as a dark electric dipole, magnetic dipole or anapole moment. We find that couplings to point-like degrees of freedom $N$ and $S$ often dominate dark matter detection rates, implying that exotic materials with orbital $L$ order or large spin-orbit couplings $L\otimes S$ are not necessary to have strong reach to a broad class of DM models. We highlight that phonon based crystal experiments in active R&D (such as SPICE) will probe light dark matter models well beyond those having a simple spin-independent interaction, including e.g. models with dipole and anapole interactions. Lastly, we make publicly available a code, PhonoDark, which computes single phonon production rates in a wide variety of materials with the effective field theory framework.
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Submitted 19 October, 2021; v1 submitted 28 September, 2020;
originally announced September 2020.
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Detectability of Axion Dark Matter with Phonon Polaritons and Magnons
Authors:
Andrea Mitridate,
Tanner Trickle,
Zhengkang Zhang,
Kathryn M. Zurek
Abstract:
Collective excitations in condensed matter systems, such as phonons and magnons, have recently been proposed as novel detection channels for light dark matter. We show that excitation of i) optical phonon polaritons in polar materials in an ${\mathcal O}$(1 T) magnetic field (via the axion-photon coupling), and ii) gapped magnons in magnetically ordered materials (via the axion wind coupling to th…
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Collective excitations in condensed matter systems, such as phonons and magnons, have recently been proposed as novel detection channels for light dark matter. We show that excitation of i) optical phonon polaritons in polar materials in an ${\mathcal O}$(1 T) magnetic field (via the axion-photon coupling), and ii) gapped magnons in magnetically ordered materials (via the axion wind coupling to the electron spin), can cover the difficult-to-reach ${\mathcal O}$(1-100) meV mass window of QCD axion dark matter with less than a kilogram-year exposure. Finding materials with a large number of optical phonon or magnon modes that can couple to the axion field is crucial, suggesting a program to search for a range of materials with different resonant energies and excitation selection rules; we outline the rules and discuss a few candidate targets, leaving a more exhaustive search for future work. Ongoing development of single photon, phonon and magnon detectors will provide the key for experimentally realizing the ideas presented here.
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Submitted 20 May, 2020;
originally announced May 2020.
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Observability of Dark Matter Substructure with Pulsar Timing Correlations
Authors:
Harikrishnan Ramani,
Tanner Trickle,
Kathryn M. Zurek
Abstract:
Dark matter substructure on small scales is currently weakly constrained, and its study may shed light on the nature of the dark matter. In this work we study the gravitational effects of dark matter substructure on measured pulsar phases in pulsar timing arrays (PTAs). Due to the stability of pulse phases observed over several years, dark matter substructure around the Earth-pulsar system can imp…
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Dark matter substructure on small scales is currently weakly constrained, and its study may shed light on the nature of the dark matter. In this work we study the gravitational effects of dark matter substructure on measured pulsar phases in pulsar timing arrays (PTAs). Due to the stability of pulse phases observed over several years, dark matter substructure around the Earth-pulsar system can imprint discernible signatures in gravitational Doppler and Shapiro delays. We compute pulsar phase correlations induced by general dark matter substructure, and project constraints for a few models such as monochromatic primordial black holes (PBHs), and Cold Dark Matter (CDM)-like NFW subhalos. This work extends our previous analysis, which focused on static or single transiting events, to a stochastic analysis of multiple transiting events. We find that stochastic correlations, in a PTA similar to the Square Kilometer Array (SKA), are uniquely powerful to constrain subhalos as light as $\sim 10^{-13}~M_\odot$, with concentrations as low as that predicted by standard CDM.
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Submitted 6 May, 2020;
originally announced May 2020.
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Multi-Channel Direct Detection of Light Dark Matter: Target Comparison
Authors:
Sinead M. Griffin,
Katherine Inzani,
Tanner Trickle,
Zhengkang Zhang,
Kathryn M. Zurek
Abstract:
Direct detection experiments for light dark matter are making enormous leaps in reaching previously unexplored model space. Several recent proposals rely on collective excitations, where the experimental sensitivity is highly dependent on detailed properties of the target material, well beyond just nucleus mass numbers as in conventional searches. It is thus important to optimize the target choice…
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Direct detection experiments for light dark matter are making enormous leaps in reaching previously unexplored model space. Several recent proposals rely on collective excitations, where the experimental sensitivity is highly dependent on detailed properties of the target material, well beyond just nucleus mass numbers as in conventional searches. It is thus important to optimize the target choice when considering which experiment to build. We carry out a comparative study of target materials across several detection channels, focusing on electron transitions and single (acoustic or optical) phonon excitations in crystals, as well as the traditional nuclear recoils. We compare materials currently in use in nuclear recoil experiments (Si, Ge, NaI, CsI, CaWO$_4$), a few which have been proposed for light dark matter experiments (GaAs, Al$_2$O$_3$, diamond), as well as 16 other promising polar crystals across all detection channels. We find that target- and dark matter model-dependent reach is largely determined by a small number of material parameters: speed of sound, electronic band gap, mass number, Born effective charge, high frequency dielectric constant, and optical phonon energies. We showcase, for each of the two benchmark models, an exemplary material which has a better reach than in any currently proposed experiment.
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Submitted 19 October, 2021; v1 submitted 23 October, 2019;
originally announced October 2019.
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Multi-Channel Direct Detection of Light Dark Matter: Theoretical Framework
Authors:
Tanner Trickle,
Zhengkang Zhang,
Kathryn M. Zurek,
Katherine Inzani,
Sinéad M. Griffin
Abstract:
We present a unified theoretical framework for computing spin-independent direct detection rates via various channels relevant for sub-GeV dark matter -- nuclear recoils, electron transitions and single phonon excitations. Despite the very different physics involved, in each case the rate factorizes into the particle-level matrix element squared, and an integral over a target material- and channel…
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We present a unified theoretical framework for computing spin-independent direct detection rates via various channels relevant for sub-GeV dark matter -- nuclear recoils, electron transitions and single phonon excitations. Despite the very different physics involved, in each case the rate factorizes into the particle-level matrix element squared, and an integral over a target material- and channel-specific dynamic structure factor. We show how the dynamic structure factor can be derived in all three cases following the same procedure, and extend previous results in the literature in several aspects. For electron transitions, we incorporate directional dependence and point out potential daily modulation signals in anisotropic target materials. For single phonon excitations, we present a new derivation of the rate formula from first principles for generic spin-independent couplings, and include the first calculation of phonon excitation through electron couplings. We also discuss the interplay between single phonon excitations and nuclear recoils, and clarify the role of Umklapp processes, which can dominate the single phonon production rate for dark matter heavier than an MeV. Our results highlight the complementarity between various search channels in probing different kinematic regimes of dark matter scattering, and provide a common reference to connect dark matter theories with ongoing and future direct detection experiments.
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Submitted 27 October, 2021; v1 submitted 17 October, 2019;
originally announced October 2019.
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Detecting Light Dark Matter with Magnons
Authors:
Tanner Trickle,
Zhengkang Zhang,
Kathryn M. Zurek
Abstract:
Scattering of light dark matter with sub-eV energy deposition can be detected with collective excitations in condensed matter systems. When dark matter has spin-independent couplings to atoms or ions, it has been shown to efficiently excite phonons. Here we show that, if dark matter couples to the electron spin, magnon excitations in materials with magnetic dipole order offer a promising detection…
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Scattering of light dark matter with sub-eV energy deposition can be detected with collective excitations in condensed matter systems. When dark matter has spin-independent couplings to atoms or ions, it has been shown to efficiently excite phonons. Here we show that, if dark matter couples to the electron spin, magnon excitations in materials with magnetic dipole order offer a promising detection path. We derive general formulae for single magnon excitation rates from dark matter scattering, and demonstrate as a proof of principle the projected reach of a yttrium iron garnet target for several dark matter models with spin-dependent interactions. This highlights the complementarity of various collective excitations in probing different dark matter interactions.
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Submitted 15 May, 2020; v1 submitted 31 May, 2019;
originally announced May 2019.
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Pulsar Timing Probes of Primordial Black Holes and Subhalos
Authors:
Jeff A. Dror,
Harikrishnan Ramani,
Tanner Trickle,
Kathryn M. Zurek
Abstract:
Pulsars act as accurate clocks, sensitive to gravitational redshift and acceleration induced by transiting clumps of matter. We study the sensitivity of pulsar timing arrays (PTAs) to single transiting compact objects, focusing on primordial black holes and compact subhalos in the mass range from $10^{-12} M _{\odot}$ to well above $100~M_\odot$. We find that the Square Kilometer Array can constra…
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Pulsars act as accurate clocks, sensitive to gravitational redshift and acceleration induced by transiting clumps of matter. We study the sensitivity of pulsar timing arrays (PTAs) to single transiting compact objects, focusing on primordial black holes and compact subhalos in the mass range from $10^{-12} M _{\odot}$ to well above $100~M_\odot$. We find that the Square Kilometer Array can constrain such objects to be a subdominant component of the dark matter over this entire mass range, with sensitivity to a dark matter sub-component reaching the sub-percent level over significant parts of this range. We also find that PTAs offer an opportunity to probe substantially less dense objects than lensing because of the large effective radius over which such objects can be observed, and we quantify the subhalo concentration parameters which can be constrained.
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Submitted 24 July, 2019; v1 submitted 14 January, 2019;
originally announced January 2019.