Session R12: Axion and Dark Matter II

Results of a Microwave Cavity Search for Dark Matter Axion-Like-Particles

There is a strong physics case for new particles with very weak couplings and sub-eV mass, such as axions, axion-like particles (ALPs), and hidden photons. These particles arise naturally in many beyond the Standard Model theories, and as well, have the correct properties to form part or all of the cold dark matter. The Yale Microwave Cavity Experiment (YMCE) uses a microwave cavity in a strong magnetic field to search for conversions of these new particles to photons, if they form part of the galactic dark matter. YMCE has conducted axion-like-particle searches in the mass range 140.2 - 142.7 $\mu$eV (33.9-34.5 GHz). In this talk, we present preliminary results from this search.   

Mississippi State Axion Search

The Mississippi State Axion Search (MASS) is an attempt to improve the limit on the mass coupling parameter of the Axion. The design features a sealed cavity partitioned by a lead wall into which RF power is transmitted. Another antenna on the far end of the cavity serves as the detector. The signal acquired by this antenna is fed through an integrator and a series of pre-amps and lock-ins before reaching the data acquisition system. The data acquisition system, written in the LabView front end DASYLab, operates at 1kHz in synchronicity with a TTL pulse that resets the integrator. The value recorded by the DAQ is, therefore, the maximum voltage of integration in the millisecond period. The Axion signal would appear in the data as a voltage excess. Several measures have been implemented with more being developed to ensure the validity of detections. Large excesses are cut by an electronics system, and smaller anomalies will be excised in the data analysis. Results will also compared to a complete Monte Carlo simulation currently in development.   

Progress on the Axion Dark Matter eXperiment - High Frequency (ADMX-HF)

The Axion Dark Matter eXperiment - High Frequency (ADMX-HF) is a microwave cavity experiment at Yale specifically designed to be both a pathfinder for first data in the 4-10 GHz (20-100 microelectronvolt) range, and an innovation test-bed for new concepts with promise to dramatically increase the sensitivity, mass range and scanning rate, with the aim to migrate technology developments to ADMX. Built around a 9T superconducting magnet (16.5 cm I.D. x 40 cm long) and dilution refrigerator, ADMX-HF will utilize Josephson Parametric Amplifiers (JPA) from the outset, and is projected to achieve sensitivity within the axion model band, despite its small volume. It will explore concepts such as hybrid superconducting cavities to improve the cavity Q by an order of magnitude, and operation in squeezed-state mode to reduce the amplifier noise temperature below the quantum limit. The experiment, a collaboration of Yale, UC Berkeley, JILA/Colorado and LLNL is in final stages of integration and nearing commissioning phase.   

ADMX High-Frequency Microwave Cavity Development

The Axion Dark Matter eXperiment (ADMX), a direct-detection axion search, has just begun taking data with a redesigned system. Earlier phases conducted axion searches in the mass range of 1.9 -- 3.5 $\mu $eV (460 -- 850 MHz) setting upper limits below the theoretical KSVZ coupling strength of the axion to two photons. The current upgrades will allow ADMX to detect axions with even the most pessimistic couplings in this frequency range and in to the GHz regime. In order to expand its mass reach, ADMX is developing next-generation microwave cavities that will enable the search for axions with masses up to 12 $\mu $eV (3 GHz) at the more weakly interacting DFSZ coupling value. Testing and analysis has been performed on photonic band-gaps, regulating multi-vanes, segmented resonators, and slow wave cavities. Results of recent testing and future development plans will be presented.   

Progress towards a Hybrid Superconducting Microwave Cavity for ADMX

Axions are a well motivated dark matter candidate and can be detected by their resonant conversion into photons using a microwave resonant cavity in an axial magnetic field. This is the basis of both the ADMX and ADMX-HF experiments. The axion-photon conversion power is directly related to the quality factor (Q = resonant frequency over bandwidth) of the microwave cavity used. To date copper cavities have been used with Q $\sim 10^5$ at frequencies of 1 GHz. As one scales to higher frequencies this Q degrades substantially. Superconducting cavities can regularly be made with Q $> 10^9$ but would be driven normal in the high magnetic field of ADMX. Here we describe progress of R\&D efforts to make hybrid cavities with regular copper endcaps and a thin-film superconducting barrel that can maintain its superconducting properties in the presence of a strong axial magnetic field. This hybrid cavity system has a potential Q great than copper by an order of magnitude (or more) thus greatly increasing the sensitivity of the system to axions.   

Status of the MiniCLEAN Dark Matter Experiment

The MiniCLEAN dark matter experiment is an ultra-low background single phase liquid argon and neon detector with a fiducial mass of 150 kg. The ability to exchange targets, the background rejection offered by noble liquids, and the scalability of the single phase approach allow MiniCLEAN to demonstrate the technologies required for the construction and operation of next generation multi-ton WIMP dark matter and precision low-energy solar neutrino experiments. MiniCLEAN utilizes a modular design with cold photomultiplier tubes in a spherical geometry to maximize light yield which allows highly efficient rejection of nuclear recoils from electronic recoil backgrounds using pulse shape discrimination (PSD) techniques. To demonstrate the effective reach of single phase PSD, MiniCLEAN will be spiked with additional $^{39}$Ar. MiniCLEAN's inner detector has recently completed construction underground at SNOLAB, and the detector is being commissioned for operation at room temperature under vacuum and with purified argon gas. An update on the inner detector commissioning and construction of the infrastructure to operate the detector in the liquid phase will be given.   

Mini-LENS: developing a charged-current approach to measuring CNO and pp solar neutrinos

The Low-Energy Neutrino Spectroscopy (LENS) experiment is based on neutrino detection via a charged-current interaction with $^{\mathrm{115}}$In and offers the ability to cleanly observe both pp and CNO neutrinos. In contrast, elastic-scattering detectors, such as Borexino and SNO$+$ suffer from virtually inseparable backgrounds. Thus, LENS might be uniquely positioned to resolve the solar metallicity question via measurement of the CNO neutrino flux, as well as test the predicted equivalence of solar luminosity as measured by photons versus neutrinos The mini-LENS program is testing the performance of the optically-segmented 3D lattice geometry unique to LENS. This first-of-a-kind lattice design is also suited for a range of other applications where high segmentation and large light collection are required (eg: sterile neutrinos with sources, double beta decay, and surface detection of reactor neutrinos). The current status and recent design changes of miniLENS at KURF will be presented.   

A search for WIMPs and tests of local dark matter velocity distributions with the CoGeNT public dataset

Since December 2009, the CoGeNT experiment has recorded interactions in the detector with the goal of either detecting dark matter or setting stringent limits on the mass and cross section of these particles, assuming that dark matter is a form of WIMP (Weakly Interacting Massive Particle). The collaboration has made public this dataset to the broader community and this analysis is based on that dataset. We perform an unbinned, maximum likelihood fit to the data, accounting for known backgrounds and systematic effects. We model the WIMP signal, parametrized by energy deposition and time of year, mass, cross-section, and choice of local WIMP velocity distribution. The velocity distribution is modeled with a Maxwellian-Boltzman distribution, as well as more directional streams. The current status of this analysis will be presented.   

The DRIFT Directional Dark Matter Experiments

The DRIFT dark matter collaboration aims to detect the sidereal modulation of the dark matter signal through measurement of spatial components of the recoil nucleus direction from WIMP-nucleon interactions. DRIFT uses low-pressure negative-ion time projection chambers to measure recoil nuclei, and the recoiling nuclei, from a standard WIMP halo, would typically leave a millimeter-scale ionization track in the chamber. The rotation of the Earth on its axis combined with the motion of the solar system through the WIMP halo creates the sidereal modulation. This sidereal (``daily'') modulation is the change in average direction of the recoils over the course of the sidereal day, which for the DRIFT detector, located in England, changes from generally down to south once a (sidereal) day. Recent advances in background rejection are allowing DRIFT-IId to run background free. And measurement of the interaction location along the ion drift direction has recently been enabled by adding a small amount of oxygen to the drift gas. This talk will report on these recent advances and show current limits, as well as describe plans for future DRIFT detectors.