<p>The use of experiments searching for light axion dark matter as high-frequency gravitational wave detectors has garnered increasing attention in recent years. We explore the capabilities of the Broadband Reflector Experiment for Axion Detection (BREAD) in probing the GW parameter space and study the directional dependence of its coverage. This detector can investigate frequencies ranging from 0.05 to 200 THz. We find that by employing single photon detectors, BREAD is sensitive to GWs with characteristic strains as low as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>21</mn></mrow></msup></math> at 0.1 THz and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>25</mn></mrow></msup></math> at 200 THz with a year exposure time, making it competitive with other proposals operating at similar frequencies.</p>

United States

Rodolfo Capdevilla

Roni Harnik

South Korea

China

Taegyun Kim

Germany

Tom Krokotsch

High-frequency gravitational wave detection by the BREAD experiment

Millicharged particles appear in several extensions of the standard model, but have not yet been detected. These hypothetical particles could be produced by an intense proton beam striking a fixed target. We use data collected in 2020 by the SENSEI experiment in the MINOS cavern at the Fermi National Accelerator Laboratory to search for ultrarelativistic millicharged particles produced in collisions of protons in the NuMI beam with a fixed graphite target. The absence of any ionization events with 3 to 6 electrons in the SENSEI data allow us to place world-leading constraints on millicharged particles for masses between 30 to 380 MeV. This work also demonstrates the potential of utilizing low-threshold detectors to investigate new particles in beam-dump experiments, and motivates a future experiment designed specifically for this purpose.

Israel

Liron Barak

Itay M. Bloch

Ana M. Botti

Argentina

Mariano Cababie

Gustavo Cancelo

Brenda A. Cervantes-Vergara

Luke Chaplinsky

Michael Crisler

Alex Drlica-Wagner

Rouven Essig

Juan Estrada

Erez Etzion

Guillermo Fernandez Moroni

Stephen E. Holland

Yaron Korn

Canada

Ian Lawson

Steffon Luoma

Sravan Munagavalasa

Aviv Orly

Santiago E. Perez

Dario Rodrigues

Nathan A. Saffold

France

Silvia Scorza

Aman Singal

Miguel Sofo Haro

Leandro Stefanazzi

Kelly Stifter

Javier Tiffenberg

Sho Uemura

Tomer Volansky

Tien-Tien Yu

Zhen Liu

Ryan Plestid

Search by the SENSEI Experiment for Millicharged Particles Produced in the NuMI Beam

Oscura is a planned light-dark matter search experiment using Skipper-CCDs with a total active mass of 10 kg. As part of the detector development, the collaboration plans to build the Oscura Integration Test (OIT), an engineering test with 10% of the total mass. Here we discuss the early science opportunities with the OIT to search for millicharged particles (mCPs) using the NuMI beam at Fermilab. mCPs would be produced at low energies through photon-mediated processes from decays of scalar, pseudoscalar, and vector mesons, or direct Drell-Yan productions. Estimates show that the OIT would be a world-leading probe for mCPs in the ∼MeV mass range.

Santiago Perez

Mexico

Brenda Cervantes-Vergara

Juan D’Olivo

Alexis Aguilar-Arevalo

Fabricio Alcalde-Bessia

Nicolás Avalos

Paraguay

Oscar Baez

Daniel Baxter

Xavier Bertou

Carla Bonifazi

Ana Botti

Spain

Nuria Castelló-Mor

Alvaro Chavarria

Claudio Chavez

Fernando Chierchie

Juan Egea

Cyrus Dreyer

Ezequiel Estrada

Paul Grylls

Guillermo Fernandez-Moroni

Marivi Fernández-Serra

Santiago Ferreyra

Stephen Holland

Agustín Barreda

Andrew Lathrop

Ben Loer

Edgar Villalpando

Mauricio Montero

Kellie McGuire

Jorge Molina

Danielle Norcini

Alexander Piers

Paolo Privitera

Nathan Saffold

Richard Saldanha

Radomir Smida

Miguel Sofo-Haro

Diego Stalder

Michelangelo Traina

Yu-Dai Tsai

Brazil

Pedro Ventura

Rocío Cortabitarte

Rachana Yajur

Searching for millicharged particles with 1 kg of Skipper-CCDs using the NuMI beam at Fermilab

We propose a novel search technique for axions with a <math><mrow><mi>C</mi><mi>P</mi></mrow></math>-violating monopole coupling <math><msub><mover><mi>g</mi><mo>˜</mo></mover><mi>Q</mi></msub></math> to bulk Standard Model charges <math><mi>Q</mi><mo>∈</mo><mo>{</mo><mi>B</mi><mo>,</mo><mi>L</mi><mo>,</mo><mi>B</mi><mo>−</mo><mi>L</mi><mo>}</mo></math>. Gradients in the static axion field configurations sourced by matter induce achromatic circular photon birefringence via the axion-photon coupling <math><msub><mi>g</mi><mrow><mi>ϕ</mi><mi>γ</mi></mrow></msub></math>. Circularly polarized light fed into an optical or (open) radio-frequency (RF) Fabry-Pérot (FP) cavity develops a phase shift that accumulates up to the cavity finesse: the fixed axion spatial gradient prevents a cancellation known to occur for an axion dark-matter search. The relative phase shift between two FP cavities fed with opposite circular polarizations can be detected interferometrically. This time-independent signal can be modulated up to nonzero frequency by altering the cavity orientations with respect to the field gradient. Multiwavelength co-metrology techniques can be used to address chromatic measurement systematics and noise sources. With Earth as the axion source, we project reach beyond current constraints on the product of couplings <math><msub><mover><mi>g</mi><mo>˜</mo></mover><mi>Q</mi></msub><msub><mi>g</mi><mrow><mi>ϕ</mi><mi>γ</mi></mrow></msub></math> for axion masses <math><msub><mi>m</mi><mi>ϕ</mi></msub><mo>≲</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></math>. If shot-noise-limited sensitivity can be achieved, an experiment using high-finesse RF FP cavities could reach a factor of <math><mo>∼</mo><msup><mn>10</mn><mn>5</mn></msup></math> into new parameter space for <math><msub><mover><mi>g</mi><mo>˜</mo></mover><mi>Q</mi></msub><msub><mi>g</mi><mrow><mi>ϕ</mi><mi>γ</mi></mrow></msub></math> for masses <math><msub><mi>m</mi><mi>ϕ</mi></msub><mo>≲</mo><mn>4</mn><mo>×</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>11</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>eV</mi></math>.

Michael A. Fedderke

Jedidiah O. Thompson

Raphael Cervantes

Bianca Giaccone

David E. Kaplan

Sam Posen

Surjeet Rajendran

Measuring axion gradients with photon interferometry

Superconducting cavities can operate analogously to Weber bar detectors of gravitational waves, converting mechanical to electromagnetic energy. The significantly reduced electromagnetic noise results in increased sensitivity to high-frequency signals well outside the bandwidth of the lowest mechanical resonance. In this work, we revisit such signals of gravitational waves and demonstrate that a setup similar to the existing MAGO prototype, operating in a scanning or broadband manner, could have sensitivity to strains of <math><mrow><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>22</mn></mrow></msup><mo>−</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>18</mn></mrow></msup></mrow></math> for frequencies of <math><mrow><mo>∼</mo><mn>10</mn><mtext> </mtext><mtext> </mtext><mi>kHz</mi><mi>–</mi><mn>1</mn><mtext> </mtext><mi>GHz</mi></mrow></math>.

Asher Berlin

Diego Blas

Raffaele Tito D’Agnolo

Switzerland

Sebastian A. R. Ellis

Yonatan Kahn

Jan Schütte-Engel

Michael Wentzel

Electromagnetic cavities as mechanical bars for gravitational waves

Flavour-changing-neutral currents (FCNCs) involving the top quark are highly suppressed within the Standard Model (SM). Hence, any signal in current or planned future collider experiments would constitute a clear manifestation of physics beyond the SM. We propose a novel, interference-based strategy to search for top-quark FCNCs involving the Z boson that has the potential to complement traditional search strategies due to a more favourable luminosity scaling. The strategy leverages on-shell interference between the FCNC and SM decay of the top quark into hadronic final states. We estimate the feasibility of the most promising case of anomalous tZc couplings using Monte Carlo simulations and a simplified detector simulation. We consider the main background processes and discriminate the signal from the background with a deep neural network that is parametrised in the value of the anomalous tZc coupling. We present sensitivity projections for the HL-LHC and the FCC-hh. We find an expected 95% CL upper limit of  $${\mathcal {B}}_{\textrm{excl}}(t\rightarrow Zc) = 6.4 \times 10^{-5}$$  <math> <mrow> <msub> <mi>B</mi> <mtext>excl</mtext> </msub> <mrow> <mo>(</mo> <mi>t</mi> <mo>→</mo> <mi>Z</mi> <mi>c</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>6.4</mn> <mo>×</mo> <msup> <mn>10</mn> <mrow> <mo>-</mo> <mn>5</mn> </mrow> </msup> </mrow> </math>   for the HL-LHC. In general, we conclude that the interference-based approach has the potential to provide both competitive and complementary constraints to traditional multi-lepton searches and other strategies that have been proposed to search for tZc FCNCs.

Lucas Cremer

Johannes Erdmann

Jan Späh

Emmanuel Stamou

Leveraging on-shell interference to search for FCNCs of the top quark and the Z boson

We propose using trapped electrons as high-<math><mi>Q</mi></math> resonators for detecting meV dark photon dark matter. When the rest energy of the dark photon matches the energy splitting of the two lowest cyclotron levels, the first excited state of the electron cyclotron will be resonantly excited. A proof-of-principle measurement, carried out with one electron, demonstrates that the method is background free over a 7.4 day search. It sets a limit on dark photon dark matter at 148 GHz (0.6 meV) that is around 75 times better than previous constraints. Dark photon dark matter in the 0.1–1 meV mass range (20–200 GHz) could likely be detected at a similar sensitivity in an apparatus designed for dark photon detection.

Xing Fan

Gerald Gabrielse

Peter W. Graham

Thomas G. Myers

Harikrishnan Ramani

Benedict A. D. Sukra

Samuel S. Y. Wong

Yawen Xiao

One-Electron Quantum Cyclotron as a Milli-eV Dark-Photon Detector

We give a detailed treatment of electromagnetic signals generated by gravitational waves (GWs) in resonant cavity experiments. Our investigation corrects and builds upon previous studies by carefully accounting for the gauge dependence of relevant quantities. We work in a preferred frame for the laboratory, the proper detector frame, and show how to resum short-wavelength effects to provide analytic results that are exact for GWs of arbitrary wavelength. This formalism allows us to firmly establish that, contrary to previous claims, cavity experiments designed for the detection of axion dark matter only need to reanalyze existing data to search for high-frequency GWs with strains as small as <math><mrow><mi>h</mi><mo>∼</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>22</mn></mrow></msup><mi>–</mi><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>21</mn></mrow></msup></mrow></math>. We also argue that directional detection is possible in principle using readout of multiple cavity modes. Further improvements in sensitivity are expected with cutting-edge advances in superconducting cavity technology.

Detecting high-frequency gravitational waves with microwave cavities

We propose an experimental setup to search for Axion-like particles (ALPs) using two superconducting radio-frequency cavities. In this light-shining-through-wall setup the axion is sourced by two modes with large fields and nonzero   <math> <mover> <mi>E</mi> <mo>→</mo> </mover> <mo>⋅</mo> <mover> <mi>B</mi> <mo>→</mo> </mover> </math>  $$ \overrightarrow{E}\cdot \overrightarrow{B} $$  in an emitter cavity. In a nearby identical cavity only one of these modes, the spectator, is populated while the other is a quiet signal mode. Axions can up-convert off the spectator mode into signal photons. We discuss the physics reach of this setup finding potential to explore new ALP parameter space. Enhanced sensitivity can be achieved if high-level modes can be used, thanks to improved phase matching between the excited modes and the generated axion field. We also discuss the potential leakage noise effects and their mitigation, which is aided by   <math> <mi>O</mi> </math>  $$ \mathcal{O} $$ (GHz) separation between the spectator and signal frequencies.

Christina Gao

Axion searches with two superconducting radio-frequency cavities

We consider the production of a “fast flux” of hypothetical millicharged particles (mCPs) in the interstellar medium. We consider two possible sources induced by cosmic rays: (a) <math><mrow><mi>p</mi><mi>p</mi><mo>→</mo><mo>(</mo><mi>meson</mi><mo>)</mo><mo>→</mo><mspace></mspace><mo>(</mo><mi>mCP</mi><mo>)</mo></mrow></math>, which adds to atmospheric production of mCPs, and (b) cosmic-ray upscattering on a millicharged component of dark matter. We notice that the galactic magnetic fields retain mCPs for a long time, leading to an enhancement of the fast flux by many orders of magnitude. In both scenarios, we calculate the expected signal for direct dark matter detection aimed at electron recoil. We observe that in scenario (a) neutrino detectors (ArgoNeuT and Super-Kamiokande) still provide superior sensitivity compared to dark matter detectors (XENON1T). However, in scenarios with a boosted dark matter component, the dark matter detectors perform better, given the enhancement of the upscattered flux at low velocities. Given the uncertainties, both in the flux generation model and in the actual atomic physics leading to electron recoil, it is still possible that the XENON1T-reported excess may come from a fast mCP flux, which will be decisively tested with future experiments.

Maxim Pospelov

Millicharged cosmic rays and low recoil detectors