Welcome address

• Matthias Neubert (Johannes Gutenberg University Mainz)

Room: 02.430

Introduction

• Derek Jackson Kimball

Room: 02.430

Results and future prospects of the search for Axion domain walls using the Global Network of Optical Magnetometers for Exotic physics (GNOME)

• Hector Masia-Roig (Helmholtz institute Mainz)

Room: 02.430 The Global Network of Optical Magnetometers for Exotic physics (GNOME) is a network of geographically separated, time-synchronized atomic magnetometers and co-magnetometers in magnetically shielded environments³. This configuration allows monitoring the Zeemann levels energy splitting of an atomic ensemble continuously and simultaneously at different places of the globe. Axion-like particles could form topological defects in the form of domain walls. The axion-like field gradient contained in the domain wall may couple with the spin of the Standard Model particles which will perturb the Zeemann levels. A time-domain analysis method was developed to look for signal patterns compatible with a domain-wall⁴. The results and methods of the analysis of the science run performed between the 29th of November and the 22nd of December 2017 will be presented⁵. Since then GNOME has gathered a large amount of data which possibilities reaching better sensitivity to domain walls. Additionally, the data quality have been improved by the implementation of check routines. Challenges and improvements posed by the new data will be discussed. ¹ This word is supported by the European Research Council under the European Union’s Horizon 2020 Research and Innovative Program under Grant agreement No. 695405 and the Cluster of Excellence PRISMA+ ² Helmholtz Institut Mainz, Johannes Gutenberg-Universitaet, 55099 Mainz, Germany ³ S. Afach, D. Budker et al., Physics of the Dark Universe, 22, 162-180 (2018). ⁴ H.Masia-Roig, J. A. Smiga et al., Physics of the Dark Universe, 28, 100494 (2020). ⁵ S. Afach, Ben C. Buchler et al., Nature Physics volume 17, pages 1396–1401 (2021)

Ultralight Dark Matter Searches Using the Global Network of Optical Magnetometers for Exotic Physics (GNOME)

• Grzegorz Lukasiewicz (Jagiellonian University)

Room: 02.430 Not only optical magnetometers are the most sensitive sensors of magnetic fields, but they may also be used for searches of non-magnetic spin couplings, including those associated with interaction with dark matter. In particular, GNOME uses the magnetometers to search for the ultralight dark matter (axions and axion-like particles). The talk will cover selected dark-matter spin-dependent scenarios that can be investigated using GNOME. They include searches for dark-matter topological defects (domain walls) and stochastic fluctuations of the dark-matter field. Specific attention will be paid to the presentation of data analysis methods.

New prospects for the axion dark-matter search brought by the advanced GNOME sensor

• Klinger Emmanuel (HIM)

Room: 02.430 In recent years, optically-pumped magnetometers (OPMs) have been successfully used for setting new constraints on possible parameters of transient exotic spin couplings of axion dark matter [1]. This was achieved with the help of the Global Network of Optical Magnetometers for Exotic physics searches (GNOME), being a world-wide network of synchronized magnetometers located in Europe, Asia, Australia, and USA. However, the GNOME network can be improved by implementing a new type of sensors that is less prone to magnetic-field noise. This can be achieved by implementation a noble-gas-alkali-metal comagnetometers [2]. These sensors allow a sensitivity gain to exotic spin couplings of protons and neutrons of three to five orders of magnitude. Moreover, in certain conditions comagnetometers allow to distinguish between magnetic and nonmagnetic spin perturbations [3]. This is a significant advantage of the system compared to the conventionally used OPMs, as it allows to discriminate nonmagnetic couplings events. We will present the results of the tests of the system with nonmagnetic spin couplings generated with rotation and AC Stark effect, which was used to simulate nonmagnetic spin perturbations targeted by GNOME. We will also discuss other particular dark-matter signatures, that can be observed with the sensor.

Presentation via Zoom by Noah Brayali Room: 02.430

Search for Boson Stars Using the Global Network of Optical Magnetometers for Exotic Physics (GNOME)

• Druhv Tandon (Oberlin College)

Room: 02.430 Since the discovery of dark matter in our universe, numerous possible candidates have been proposed to explain its existence and composition. One of the candidates is the Ultralight axion-like particles, existing in the form of domain walls or boson stars, caused by topology or self-interactions. The Global Network of Optical Magnetometers to search for Exotic Physics (GNOME) looks for a transient signal caused by exotic-spin couplings as the Earth passes through such composite dark matter objects. We describe an analysis method for the GNOME data that is sensitive to bosons stars based on the excess power technique.

Search for exotic low-mass fields with a global magnetometer network

• Sami Khamis (UCLA)

Room: 02.430 The Global Network of Optical Magnetometers for Exotic physics searches (GNOME) is a network of geographically separated, time-synchronized, optically pumped atomic magnetometers searching for correlated transient signals that might herald exotic physics [1]. Quantum sensor networks provide an additional tool in multi-messenger astronomy to prove high-energy astrophysical events for signals by beyond-standard-model theories. We present a method to use the GNOME to search for coherent, intense bursts of exotic low-mass fields (ELFs) that could be produced alongside gravitational waves (GWs) [2] and fast radio bursts (FRBs). Candidate events are first identified with a model agnostic excess power search [3] and then subjected to a generalized likelihood test. Empirical distributions are employed in both stages to remove explicit assumptions about noise characteristics. We construct Feldman-Cousins confidence belts [4] to constrain detectable ELF signal amplitudes and couplings to standard-model fermions. [1] S. Afach, D. Budker et al., Physics of the Dark Universe, 22, 162-180 (2018) [2] Dailey, C., Bradley, C., Jackson Kimball, D.F. et al., Nat Astron 5, 150–158 (2021) [3] W. G. Anderson, P. R. Brady, et al., Phys. Rev. D 63, 042003 (2001) [4] G. J. Feldman and R. D. Cousins Phys., Rev. D 57, 3873 (1998)

A novel mixed species In/Yb ion optical clock

• Tanja Mehlstaeubler (Physikalisch-Technische Bundesanstalt)

Room: 02.430 We present first optical clock measurements of an indium multi-ion clock with sympathetically cooled Coulomb crystals. The indium absolute frequency was measured against PTBs cesium fountains. The optical frequency ratio of the 115In+ ion clock transition has been measured against optical clocks at PTB, INRIM and SYRTE in an international clock comparison campaigne. The concept of a mixes-species optical clock and uncertainties of multi-ion operation are discussed.

Dark matter searches and Quantum techniques at the QDM labs at UWA

• Michael Tobar

Room: 02.430

Dark Spectroscopy

• Jose E.R. Cembranos (Universidad Complutense de Madrid & IPARCOS)

Room: 02.430 Dark matter could be made up of dark photons, massive but very light particles whose interactions with matter resemble those of usual photons but suppressed by a small mixing parameter. We analyze the main approaches to dark photon interactions and how they can be applied to direct detection experiments which test different ranges of masses and mixings. A new experiment based on counting dark photons from induced atomic transitions in a target material is proposed. This approach appears to be particularly appropriate for dark photon detection in the meV mass range, extending the constraints in the mixing parameter by up to eight orders of magnitude with respect to previous experiments.

Dissecting Axion and Dark Photon with A Network of Vector Sensors

• Yifan Chen (ITP-CAS)

Room: 02.430 We develop formalisms for a network of vector sensors, sensitive to certain spatial components of the signals, to identify the properties of light axion or dark photon background. These bosonic fields contribute to vector-like signals in the detectors, including effective magnetic fields triggering the spin precession, effective electric currents in a shielded room, and forces on the matter. The interplay between a pair of vector sensors and a baseline that separates them can potentially uncover rich information of the bosons, including angular distribution, polarization modes, source localization, and macroscopic circular polarization. Using such a network, one can identify the microscopic nature of a potential signal, such as distinguishing between the axion-fermion coupling and the dipole couplings with the dark photon.

Testing Lorentz symmetry in a single ytterbium ion

• Laura Dreissen (Physikalisch-Technische Bundesanstalt)

Room: 02.430 : In an effort to formulate a quantum consistent theory of gravitation, it is suggested that Lorentz symmetry might be broken. We search for such an effects with precision spectroscopy of a trapped ytterbium ion in a Michelson-Morley type experiment. Rf spectroscopy in the meta-stable F-manifold enables a direct comparison of the orthogonally oriented atomic orbitals with coherence times of more than 1s. With this scheme, we have reached the highest sensitivity to date and have improved the bounds of the Lorentz symmetry breaking coefficients to the 10^-21 level. These results represent the best test of Lorentz symmetry in the electron-photon sector.

Quantum Networks of Sensors

• Julian Martinez-Rincon

Room: 02.430

Ultralight dark matter searches at the mHz frontier with atom multi-gradiometry

• Leonardo Badurina (King’s College London)

Room: 02.430 Single-photon atom gradiometry is a powerful experimental technique that can be employed to search for the oscillation of atomic transition energies induced by ultra-light scalar dark matter (ULDM). Previous studies have focused on the sensitivity reach of these experiments down to ULDM masses of order ~0.1 Hz, below which gravity gradient noise (GGN) is expected to dominate over atom shot noise (ASN). In this work, after presenting a likelihood-based analysis that simultaneously accounts for a DM signal in an underground GGN and ASN background, we quantify for ULDM searches the potential benefit of a vertical multi-gradiometer experiment, which consists of three or more coupled atom interferometers along the same baseline, thus showing how GGN underground can be mitigated if not entirely cancelled in specific gradiometer configurations. Hence, we provide more robust projections for the sensitivity of vertical gradiometers like AION to scalar ULDM down to e-3 Hz, where scalar DM parameter space is still unconstrained by other experiments.

Earth as a transducer for ultralight dark-matter detection

• Saarik Kalia (Stanford University)

Room: 02.430 In this talk, I will propose the use of the Earth as a transducer for ultralight dark-matter detection. In particular I will point out a novel signal of both kinetically mixed dark-photon dark matter and axionlike dark matter: a monochromatic oscillating magnetic field generated at the surface of the Earth. Similar to the signal in a laboratory experiment in a shielded box (or cavity), this signal arises because the lower atmosphere is a low-conductivity air gap sandwiched between the highly conductive interior of the Earth below and ionosphere or interplanetary medium above. For dark-photon dark matter, the kinetic mixing with the Standard Model photon allows dark matter to convert into an observable magnetic field inside this cavity, while for axion dark matter, the background geomagnetic field of the Earth allows the axion to convert through its coupling to photons. The magnetic field signal of ultralight dark matter in a laboratory detector is usually suppressed by the size of the detector. Crucially, in our case the suppression is by the radius of the Earth, and not by the (much smaller) height of the atmosphere. The magnetic field signal exhibits a global vectorial pattern that is spatially coherent across the Earth, which enables sensitive searches for this signal using unshielded magnetometers dispersed over the surface of the Earth. I will summarize the results of such a search using a publicly available dataset from the SuperMAG collaboration. The dark-photon dark matter constraints from this search are complementary to existing astrophysical bounds, and the axion dark matter constraints are comparable to the bounds obtained by the CAST helioscope. Future searches for this signal may improve the sensitivity over a wide range of masses for both ultralight dark-matter candidates.

Testing the mean field description of scalar field dark matter

• Andrew Eberhardt (Stanford University)

Room: 02.430 The nature of dark matter, one of the major components of the cosmic standard model, remains one of the outstanding problems in physics. One interesting model is scalar field dark matter (SFDM), which fits naturally into observations in both particle physics and cosmology. Simulations and calculations using SFDM often use a classical field approximation (MFT) of the underlying quantum field theory. And while it is suspected that large occupation numbers make this description good in the early universe, it is possible that this approximation fails during nonlinear structure growth and begins to admit important quantum corrections. To investigate this possibility, we compare simulations using the MFT to those that take into account these corrections. By studying their behavior as we scale the total number of particles in the system we can estimate how long the MFT remains an accurate description of the system. We estimate this time scale for a typical halo may be of order ~300 Myr. In this talk we will explain how these simulations are performed, as well as their results, and their potential implications.

The Cosmic Axion Spin Precession Experiments

• Hendrik Bekker (Helmholtz Institute Mainz, JGU Mainz)

Room: 02.430

The Sensitivity of Spin-Precession Axion Experiments

• Jacob Leedom

Room: 02.430

Formation of axion stars and halos

• Joshua Eby

Room: 02.430