Search

The cavity haloscope provides a highly sensitive method to search for dark matter axions in the microwave regime. Experimental attempts to enhance the sensitivity have focused on improving major aspects, such as producing strong magnetic fields, increasing cavity quality factors, and achieving lowest possible noise temperatures. Minor details, however, also need to be carefully considered in realistic experimental designs. They are associated with non-uniform magnetic fields over the detection volume, noise propagation under attenuation and temperature gradients, and thermal disequilibrium in the cavity system. We take analytical approaches to these topics and offer optimal treatments for improved performance. [ABSTRACT FROM AUTHOR]

The haloscope is one of the most sensitive approaches to the QCD axion physics within the region where the axion is considered to be a dark matter candidate. Current experimental sensitivities, which rely on the lowest fundamental TM010 mode of a cylindrical cavity, are limited to relatively low mass regions. Exploiting higher-order resonant modes would be beneficial because it will enable us to extend the search range with no volume loss and higher quality factors. This approach has been discarded mainly because of the significant degradation of form factor, and difficulty with frequency tuning. Here we introduce a new tuning mechanism concept which both enhances the form factor and yields reasonable frequency tunability. A proof of concept demonstration proved that this design is feasible for high mass axion search experiments. [ABSTRACT FROM AUTHOR]

In cavity-based axion dark matter search experiments exploring high mass regions, multiple-cavity design is under consideration as a method to increase the detection volume within a given magnet bore. We introduce a new idea, referred to as a multiple-cell cavity, which provides various benefits including a larger detection volume, simpler experimental setup, and easier phase-matching mechanism. We present the characteristics of this concept and demonstrate the experimental feasibility with an example of a double-cell cavity. [ABSTRACT FROM AUTHOR]

The invisible axion is a well-motivated hypothetical particle which could address two fundamental questions in modern physics—the CP symmetry problem in the strong interactions and the dark matter mystery of our universe. The plausible mass (frequency) range of the QCD axion as a dark matter candidate spans from μ eV to meV (O (GHz) to O (THz)). The axion haloscope using a resonant cavity has provided the most sensitive search method in the microwave region. However, experimental searches have been limited to relatively low mass regions mainly due to the reduced cavity volume at high masses. As an effective approach for high-mass axion searches, a unique cavity design, featured by multiple identical cells divided by equidistant thin metal partitions in a single cylindrical cavity, was proposed and successfully demonstrated. We perform an extended study to characterize the multiple-cell cavity design and discuss the various advantages it offers for high-mass axion searches. [ABSTRACT FROM AUTHOR]

Conventional axion dark matter search experiments employ cylindrical microwave cavities immersed in a solenoidal magnetic field. Exploring higher frequency regions requires smaller size cavities as the TM 010 resonant frequencies scale inversely with cavity radius. One intuitive way to make efficient use of a given magnet volume, and thereby to increase the experimental sensitivity, is to bundle multiple cavities together and combine their individual outputs, ensuring a phase-matching of the coherent axion signal. We perform an extensive study for realistic design of a phase-matching mechanism for multiple-cavity systems and demonstrate its experimental feasibility using a double-cavity system. [ABSTRACT FROM AUTHOR]

In this paper, we consider the effects of bound atomic electrons scattered by solar neutrinos due to the electromagnetic properties of neutrinos. This necessitates considering the recoil of atomic nucleus, which should be considered in the momentum conservation, but the effect to the energy conservation is negligible. This effect changes the kinematic behavior of the scattered electron compared to that scattered on free electrons. We apply this effect to the recent XENON1T data, but the bounds obtained from this are not very restrictive. We obtained the bounds: the (transition) magnetic moment | f α β | ≤ 0. 8 6 × 1 0 − 7 (times the electron Bohr magneton) and the charge radius | r ̃ | < 4. 3 0 × 1 0 − 1 7 cm. For a nonvanishing millicharge () , the allowed bound is shown in the r ̃ 2 − plane. [ABSTRACT FROM AUTHOR]