Probing ALPs and the Axiverse with Superconducting Radiofrequency Cavities

Abstract

Axion-like particles (ALPs) with couplings to electromagnetism have long been postulated as extensions to the Standard Model. String theory predicts an "axiverse" of many light axions, some of which may make up the dark matter in the universe and/or solve the strong CP problem. We propose a new experiment using superconducting radiofrequency (SRF) cavities which is sensitive to light ALPs independent of their contribution to the cosmic dark matter density. Off-shell ALPs will source cubic nonlinearities in Maxwell's equations, such that if a SRF cavity is pumped at frequencies ${\omega }_1$ and ${\omega }_2$, in the presence of ALPs there will be power in modes with frequencies $2{\omega }_1\pm {\omega }_2$. Our setup is similar in spirit to light-shining-through-walls (LSW) experiments, but because the pump field itself effectively converts the ALP back to photons inside a single cavity, our sensitivity scales differently with the strength of the external fields, allowing for superior reach as compared to experiments like OSQAR while utilizing current technology. Furthermore, a well-defined program of increasing sensitivity has a guaranteed physics result: the first observation of the Euler-Heisenberg term of low-energy QED at energies below the electron mass. We discuss how the ALP contribution may be separated from the QED contribution by a suitable choice of pump modes and cavity geometry, and conclude by describing the ultimate sensitivity of our proposed program of experiments to ALPs.

v2: 6+4 pages, 2+1 figures. Typos fixed, references added, matches PRL version. v1: 7+2 pages, 2+1 figures

References in corpus (5)

• Flux Compactification
• Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles
• The photo-philic QCD axion
• Ultra-high quality factors in superconducting niobium cavities in ambient magnetic fields up to 190 mG
• Relaxation from particle production

Cited by in corpus (7)

• Constraints on the Coupling between Axionlike Dark Matter and Photons Using an Antiproton Superconducting Tuned Detection Circuit in a Cryogenic Penning Trap
• Extending the constraint for axion-like particles as resonances at the LHC and laser beam experiments
• Theory of Disordered Superconductors with Applications to Nonlinear Current Response
• Examining axion-like particles with superconducting radio-frequency cavity
• Electromagnetic Response of Disordered Superconducting Cavities
• The radiation emitted from axion dark matter in a homogeneous magnetic field, and possibilities for detection
• Detector Challenges of the strong-field QED experiment LUXE at the European XFEL