Cosmic Axion Spin Precession Experiment (CASPEr) (1306.6089v2)

Abstract: We propose an experiment to search for QCD axion and axion-like-particle (ALP) dark matter. Nuclei that are interacting with the background axion dark matter acquire time-varying CP-odd nuclear moments such as an electric dipole moment. In analogy with nuclear magnetic resonance, these moments cause precession of nuclear spins in a material sample in the presence of an electric field. Precision magnetometry can be used to search for such precession. An initial phase of this experiment could cover many orders of magnitude in ALP parameter space beyond the current astrophysical and laboratory limits. And with established techniques, the proposed experimental scheme has sensitivity to QCD axion masses m_a < 10^-9 eV, corresponding to theoretically well-motivated axion decay constants f_a > 10^16 GeV. With further improvements, this experiment could ultimately cover the entire range of masses m_a < 10^-6 eV, complementary to cavity searches.

• The paper presents an innovative method using nuclear spin precession to detect QCD axions and ALPs as dark matter candidates.
• It leverages precision magnetometry techniques, including SQUID and atomic magnetometers, to probe axion-induced electric dipole moments.
• The experimental design expands sensitivity to axion masses up to 10⁻⁹ eV, addressing limitations of previous dark matter search methods.

Overview of the Cosmic Axion Spin Precession Experiment (CASPEr)

The paper, "Cosmic Axion Spin Precession Experiment (CASPEr)," presents a proposal for an innovative experimental approach designed to detect the presence of QCD axions and axion-like particles (ALPs), posited components of dark matter. Through detailed theoretical analysis and experimental design concepts, it outlines how axion interactions could manifest as measurable effects in nuclear systems, notably through inducing time-varying CP-odd nuclear moments.

Conceptual Framework

One of the foundational aspects of the proposal is the exploration of nuclear spin precession in environments where an axion-induced electric dipole moment (EDM) can be probed using precision magnetometry—a technique analogous to that used in nuclear magnetic resonance. This experiment would address some of the gaps left by prior methods which primarily explored WIMP candidates, supplementing these with a search for ultra-light particles like axions.

Key Experimental Layout

The envisioned experiment utilizes a ferroelectric or polar crystal material subjected to a controlled magnetic and electric field environment. The interaction of nuclei within this crystalline medium with the present axion field is predicted to generate a characteristic nuclear spin precession—detectable as resonant signals at specific mass frequencies corresponding to dark matter candidates.

Methodologies and Sensitivity

The sensitivity of the proposed experiment is highlighted as notably advanced, leveraging techniques such as SQUID magnetometry and atomic magnetometers. This experimental design holds promise for exploring the QCD axion mass range up to $10^{-9}$ eV, significantly expanding the detectability beyond current astrophysical and laboratory constraints. Contemporary challenges such as sample magnetization noise and other technical noise sources are addressed through calculable bounds and innovative measurement techniques to minimize these interferences.

Implications and Future Directions

The CASPEr experiment represents a significant push towards the direct detection of axion dark matter, with its sensitivity poised to explore previously inaccessible parameter spaces. The experiment could potentially pave the way for diverse future developments in the direct detection of both QCD axions and broader classes of ALPs. The long-term impact of these findings could be profound, informing new theoretical frameworks regarding high-energy physics and addressing longstanding questions about the nature of dark matter.

Conclusion

In conclusion, CASPEr stands as a well-reasoned proposal that could extraordinarily further our understanding of dark matter. By pushing the frontiers of axion detection technology, it not only complements existing WIMP search efforts but may also significantly advance our comprehension of fundamental particle physics. Continued innovation in this line of research could unveil vital insights into the characteristics and behaviors of dark matter within a cosmological context.