PRISMA + and HIM scientists report the latest findings of CASPEr's Science Advances research program.
A team led by Prof. Dmitry Budker continued his search for dark matter within the Cosmic Axion Spin Precession Experiment (or "CASPEr" for short). The CASPEr Group conducts its experiments in the PRISMA + Cluster of Excellence at the Johannes Gutenberg Mainz University (JGU) and the Helmholtz Mainz Institute (HIM). CASPEr is an international research program that uses nuclear magnetic resonance techniques to identify and analyze dark matter.
Very little is known about the exact nature of dark matter. Currently, some of the most promising candidates for dark matter are extremely light bosonic particles such as axions, axial particles, or even dark photons. "They can also be seen as a classical field oscillating with a certain frequency. But we still can't put a digit on that frequency ̵
For this purpose, the CASPEr team develops different special magnetic resonance (NMR) techniques, each aimed at a specific frequency range and therefore within a certain range of dark matter arrays. NMR generally relies on the fact that nuclear spins respond to magnetic fields that oscillate with a specific “resonance frequency.” The resonance frequency is tuned by a second, usually static, magnetic field. The main idea behind the CASPEr research program is that the field of dark matter can affect nuclear spins in the same way. As the Earth moves through this field, the nuclear spins behave as if they were going to experience an oscillating magnetic field, thus generating a dark matter-induced NMR spectrum.
In the present work, the first author Antoine Garson and his colleagues used a more exotic technique: ZULF NMR (zero to ultra low field). "ZULF NMR provides a mode in which nuclear spins interact more strongly with each other than with an external magnetic field," says author John W Blanchard. "To make the turns sensitive to dark matter, all we have to do is apply a very small external magnetic field, which is much easier to stabilize." In addition, for the first time, researchers investigated 13C-shaped ZULF NMR spectra acid with respect to dark-matter sidebands, using a novel scheme for the analysis of coherent midbands with arbitrary frequency on multiple measurements.
This particular form of sideband analysis allowed scientists to search for dark matter in a new frequency range. No dark matter signal was detected, as reported by the CASPEr team in the latest issue of Science Advances which allows authors to exclude excess dark matter with connectors above a certain threshold. At the same time, these results provide another piece of the dark matter puzzle and complement previous CASPEr results reported in June, when scientists tested even lower frequencies using another specialized NMR method called "comagnetometry."
"Like a puzzle, we combine different pieces within the CASPEr program to narrow the scope for dark matter further," says Dmitry Budker. John Blanchard adds, "This is just the first step. We are currently implementing some very promising modifications to increase the sensitivity of our experiment.
Reference: "Limitations on boson dark matter by super-magnetic field magnetic resonance imaging" by Antoine Garson, John W. Blanchard, Gary P. Centers, Nathaniel L. Figueroa, Peter W. Graham, Derek F. Jackson Kimball, Surjeet Rajendran, Alexander O. Sushkov, Yevgeny V. Stadnik, Arne Wickenbrock, Teng Wu, and Dmitry Budker, October 25, 2019, Advances in Science .
doi: 10.1126 / sciadv.aax4539