Search for a Scalar Axion-like Particle at 34 GHz

TL;DR

This paper reports a pilot experiment searching for scalar axion-like particles at 34 GHz, setting new limits on their coupling strength using a cooled resonant cavity in a strong magnetic field.

Contribution

The study introduces a novel experimental setup to detect scalar ALPs near 0.1 meV and provides initial constraints on their photon coupling strength.

Findings

Excluded ALP-photon coupling g > 10^{-8}/GeV at 34 GHz with 5σ confidence

Demonstrated the feasibility of using a cryogenic resonant cavity for ALP searches

Discussed future improvements for increased sensitivity

Abstract

Light axion-like particles (ALPs) that couple to two photons are allowed in a number of proposed extensions to the Standard Model of elementary particles. Of particular interest from a theoretical and observational standpoint is the energy regime near 0.1 meV. We present results from a pilot experiment to search for a signal from a 0.14 meV scalar ALP by way of its coupling to two photons. Using a copper resonant cavity cooled to four degrees Kelvin while immersed in a seven Tesla magnetic field, and coupled to a low noise cryogenic amplifier and room temperature receiver, we exclude an ALP-driven excess of 34 GHz photons with g$>10^{-8}$/GeV with 5$\sigma$ confidence. We discuss the ramifications of this initial measurement as well as planned modifications to the experiment for increased sensitivity.