Dark matter

AXION DM DETECTORS

Staff

F. A. Borghesani, C. Braggio, G. Carugno, A. Ortolan (INFN_LNL), G. Ruoso (INFN- LNL)

PostDoc/PhD

F. Chiossi, N. Crescini

Research Activity

A well motivated dark matter (DM) candidate is the QCD axion, and high sensitivity Earth-based experiments are conceived for its detection via extremely weak, non-gravitational interactions with standard model particles (photons and fermions). 
Axion dark matter may be thought of as a background, classical oscillating field and in our experiments we exploit its interaction with the electron spin.
Therefore instead of searching for scattering events of a single dark matter particle as in WIMPS (Weakly Interacting Massive Particles) experiments, we search for the coherent effects of the entire classical dark matter field.
In the QUAX (QUest for AXions) experiment the signal for the direct detection is given by oscillations of the magnetization (magnons) of a ferrimagnetic sample in a strong magnetic field.
The static field determines the resonant interaction of the axions at the Larmor frequency as in electron paramagnetic resonance experiments.
To maximize the detection sensitivity, we conduct the experiment in the microwave cavity-QED and strong coupling regimes, with hybridization of the magnon (material) and photon (cavity) modes.
Detection of an equivalent power in the order of 10^{-26} W in microwave cavities is extremely challenging, and the development of a single photon detector is also devised to evade the quantum limit in low noise linear amplifiers.

For a detailed description see:
http://www.sciencedirect.com/science/article/pii/S2212686417300031

The AXIOMA experiment is based on the interaction of axions with the electron spin in optical crystals.
In this case the detection is accomplished by means of an all-optical scheme, whereby the axion causes transitions between Zeeman-split levels of suitable atomic species.
The devised detection scheme [1] involves transitions within the 4f shell between the atomic levels of trivalent rare earth ions regularly embedded in a transparent solid (inorganic crystals such as YLF, YAG, KPC, KPB, ...), and proper materials are selected by investigating their properties at ultracryogenic temperatures by laser-induced fluorescence studies [1], cathodo- and radio-luminescence measurements [2-4].
The AXIOMA detector may pave the way to develop new detector technologies with lowered recoil energy thresholds to probe low-mass dark matter.

References:
1. http://aip.scitation.org/doi/10.1063/1.4935151
2. https://arxiv.org/pdf/1612.05507.pdf
3. https://arxiv.org/pdf/1702.08386.pdf
4. https://arxiv.org/pdf/1703.10880.pdf

The parameter space probed by both these techniques is well beyond current astrophysical limits and significantly extends laboratory probes.