Spin-Based Amplifier Constrains Hypothetical Axions

Axions and axion-like particles that have not yet been identified may hold the key to solving some of the universe’s greatest mysteries, including dark matter and charge-parity violation in strong interactions.

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According to a number of current theories, the masses of axions are likely located within the well-motivated “axion window” (0.01 meV–1 meV). But the majority of recent astrophysical observations and laboratory searches focus on looking for axions outside the axion window.

With the help of a recently created spin-based amplifier, the research team, headed by Prof. Xinhua Peng from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences and Prof. Dmitry Budker from the Helmholtz Institution in Mainz, was able to explore promising parameter space. The research was published in the Physical Review Letters journal.

An exotic dipole–dipole interaction produced by the exchange of axions between fermions may be observable in lab settings. Both polarized xeon-129 nuclear spins and a sizable collection of polarized rubidium-87 electrons were used as fermions in this study.

Rubidium could produce an exotic signal on the xeon nuclear spins as a result of the exchange of axions, and the polarized xeon-129 nuclear spins are then used to resonantly search for the signal.

The scientists specifically demonstrated how the long-lived xeon-129 spins function as a quantum preamplifier, which can boost the exotic signal by a factor of more than 40. With this method, they were able to provide the tightest restrictions on axion-mediated neutron –electron coupling for the axion mass range of 0.03 meV to 1 meV within the axion window.

In a mass region for axions that is theoretically intriguing, this work offers a sensitive quantum technique to understand the indirect axion searches with a recent advanced spin-based amplifier.

As a fresh implementation, the spin-based amplifier scheme broadens the scope of spin measurements and can be used to resonantly look for hypothetical particles outside the Standard Model, like new spin-1 dark photons.

Journal reference:

Wang, Y., et al. (2022) Limits on Axions and Axionlike Particles within the Axion Window Using a Spin-Based Amplifier. doi.org/10.1103/PhysRevLett.129.051801.

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