Exclusion of Axionlike-Particle Cogenesis Dark Matter in a Mass Window above 100 µeV.

We report the results of Phase 1b of the ORGAN experiment, a microwave cavity haloscope searching for dark matter axions in the 107.42-111.93 µeV mass range. The search excludes axions with two-photon coupling g_{aγγ}≥4×10^{-12} GeV^{-1} with 95% confidence interval, setting the best upper bound to date and with the required sensitivity to exclude the axionlike particle cogenesis model for dark matter in this range. This result was achieved using a tunable rectangular cavity, which mitigated several practical issues that become apparent when conducting high-mass axion searches, and was the first such axion search to be conducted with such a cavity. It also represents the most sensitive axion haloscope experiment to date in the ∼100 µeV mass region.

Direct search for dark matter axions excluding ALP cogenesis in the 63- to 67-µeV range with the ORGAN experiment.

The standard model axion seesaw Higgs portal inflation (SMASH) model is a well-motivated, self-contained description of particle physics that predicts axion dark matter particles to exist within the mass range of 50 to 200 micro-electron volts. Scanning these masses requires an axion haloscope to operate under a constant magnetic field between 12 and 48 gigahertz. The ORGAN (Oscillating Resonant Group AxioN) experiment (in Perth, Australia) is a microwave cavity axion haloscope that aims to search the majority of the mass range predicted by the SMASH model. Our initial phase 1a scan sets an upper limit on the coupling of axions to two photons of ∣gaγγ∣ ≤ 3 × 10-12 per giga-electron volts over the mass range of 63.2 to 67.1 micro-electron volts with 95% confidence interval. This highly sensitive result is sufficient to exclude the well-motivated axion-like particle cogenesis model for dark matter in the searched region.

Erratum: Upconversion Loop Oscillator Axion Detection Experiment: A Precision Frequency Interferometric Axion Dark Matter Search with a Cylindrical Microwave Cavity [Phys. Rev. Lett. 126, 081803 (2021)].

This corrects the article DOI: 10.1103/PhysRevLett.126.081803.

Searching for Scalar Dark Matter via Coupling to Fundamental Constants with Photonic, Atomic, and Mechanical Oscillators.

We present a way to search for light scalar dark matter (DM), seeking to exploit putative coupling between dark matter scalar fields and fundamental constants, by searching for frequency modulations in direct comparisons between frequency stable oscillators. Specifically we compare a cryogenic sapphire oscillator (CSO), hydrogen maser (HM) atomic oscillator, and a bulk acoustic wave quartz oscillator (OCXO). This work includes the first calculation of the dependence of acoustic oscillators on variations of the fundamental constants, and demonstration that they can be a sensitive tool for scalar DM experiments. Results are presented based on 16 days of data in comparisons between the HM and OCXO, and 2 days of comparison between the OCXO and CSO. No evidence of oscillating fundamental constants consistent with a coupling to scalar dark matter is found, and instead limits on the strength of these couplings as a function of the dark matter mass are determined. We constrain the dimensionless coupling constant d_{e} and combination |d_{m_{e}}-d_{g}| across the mass band 4.4×10^{-19}≲m_{φ}≲6.8×10^{-14} eV c^{-2}, with most sensitive limits d_{e}≳1.59×10^{-1}, |d_{m_{e}}-dg|≳6.97×10^{-1}. Notably, these limits do not rely on maximum reach analysis (MRA), instead employing the more general coefficient separation technique. This experiment paves the way for future, highly sensitive experiments based on state-of-the-art acoustic oscillators, and we show that these limits can be competitive with the best current MRA-based exclusion limits.

Upconversion Loop Oscillator Axion Detection Experiment: A Precision Frequency Interferometric Axion Dark Matter Search with a Cylindrical Microwave Cavity.

First experimental results from a room-temperature tabletop phase-sensitive axion haloscope experiment are presented. The technique exploits the axion-photon coupling between two photonic resonator oscillators excited in a single cavity, allowing low-mass axions to be upconverted to microwave frequencies, acting as a source of frequency modulation on the microwave carriers. This new pathway to axion detection has certain advantages over the traditional haloscope method, particularly in targeting axions below 1 µeV (240 MHz) in energy. At the heart of the dual-mode oscillator, a tunable cylindrical microwave cavity supports a pair of orthogonally polarized modes (TM_{0,2,0} and TE_{0,1,1}), which, in general, enables simultaneous sensitivity to axions with masses corresponding to the sum and difference of the microwave frequencies. However, in the reported experiment, the configuration was such that the sum frequency sensitivity was suppressed, while the difference frequency sensitivity was enhanced. The results place axion exclusion limits between 7.44-19.38 neV, excluding a minimal coupling strength above 5×10^{-7} 1/GeV, after a measurement period of two and a half hours. We show that a state-of-the-art frequency-stabilized cryogenic implementation of this technique, ambitious but realizable, may achieve the best limits in a vast range of axion space.

Searching for Dark Matter with an Optical Cavity and an Unequal-Delay Interferometer.

We propose a new type of experiment that compares the frequency of a clock (an ultrastable optical cavity in this case) at time t to its own frequency some time t-T earlier, by "storing" the output signal (photons) in a fiber delay line. In ultralight oscillating dark matter (DM) models, such an experiment is sensitive to coupling of DM to the standard model fields, through oscillations of the cavity and fiber lengths and of the fiber refractive index. Additionally, the sensitivity is significantly enhanced around the mechanical resonances of the cavity. We present experimental results of such an experiment and report no evidence of DM for masses in the [4.1×10^{-11}, 8.3×10^{-10}] eV region. In addition, we improve constraints on the involved coupling constants by one order of magnitude in a standard galactic DM model, at the mass corresponding to the resonant frequency of our cavity. Furthermore, in the model of relaxion DM, we improve on existing constraints over the whole DM mass range by about one order of magnitude, and up to 6 orders of magnitude at resonance.

Cross-Correlation Signal Processing for Axion and WISP Dark Matter Searches.

The search for dark matter is of fundamental importance to our understanding of the universe. Weakly interacting slim particles (WISPs) such as axions and hidden sector photons are well-motivated candidates for the dark matter. Some of the most sensitive and mature experiments to detect WISPs rely on microwave cavities, and the detection of weak photon signals. It is often suggested to power combine multiple cavities, which creates a host of technical concerns. We outline a scheme based on cross correlation for power combining cavities and increasing the signal-to-noise ratio of a candidate WISP signal.

Erratum: Axion Dark Matter Coupling to Resonant Photons via Magnetic Field [Phys. Rev. Lett. 116, 161804 (2016)].

This corrects the article DOI: 10.1103/PhysRevLett.116.161804.

Axion Dark Matter Coupling to Resonant Photons via Magnetic Field.

We show that the magnetic component of the photon field produced by dark matter axions via the two-photon coupling mechanism in a Sikivie haloscope is an important parameter passed over in previous analysis and experiments. The interaction of the produced photons will be resonantly enhanced as long as they couple to the electric or magnetic mode structure of the haloscope cavity. For typical haloscope experiments the electric and magnetic couplings are equal, and this has implicitly been assumed in past sensitivity calculations. However, for future planned searches such as those at high frequency, which synchronize multiple cavities, the sensitivity will be altered due to different magnetic and electric couplings. We define the complete electromagnetic form factor and discuss its implications for current and future dark matter axion searches over a wide range of masses.