A team of scientists led by Professor Dmitry Budker have continued their search for dark matter within the framework of the ‘Cosmic Axion Sip Precession Experiment’ (CASPEr).
The CASPEr group conducts experiment at the PRSMA+ Cluster of Excellence at Johannes Gutenberg University Mainz (JGU) and the Helmholtz Institute Mainz (HIM). The international research program, CASPEr, uses nuclear magnetic resonance techniques to identify and analyse dark matter.
The exact nature of dark matter has eluded scientists since its discovery. Currently, some of the most promising dark matter candidates are extremely light bosonic particles, like dark photons, axions and other similar particles.
“These can also be regarded as a classical field oscillating at a certain frequency. But we can’t yet put a figure on this frequency – and therefore the mass of the particles,” explains Dmitry Budker. “That is why in the CASPEr research program we are systematically investigating different frequency ranges looking for hints of dark matter.”
The CASPEr team is developing various special nuclear magnetic resonance (NMR) techniques, each of which target a specific frequency rage of dark-matter particle masses. NMR generally relies on the fact that the nuclear spins react to magnetic fields oscillating at a specific resonance frequency. Such frequency is tuned via a second, usually static magnetic field.
The CASPEr initiated the study based on the idea that a dark matter field can influence the nuclear spins in the same manner. As the Earth moves through this field, nuclear spins behave as if they would experience an oscillating magnetic field, thus generating a dark matter induced NMR spectrum.
“ZULF NMR provides a regime where nuclear spins interact more strongly with each other than they do with an external magnetic field,” says corresponding author Dr. John W Blanchard. “In order to make the spins sensitive to dark matter, we only have to apply a very small external magnetic field, which is much easier to stabilise.”