Worldwide coordinated search for dark matter

Date:
January 20, 2022
Source:
Johannes Gutenberg Universitaet Mainz
Summary:
An international team of researchers has published comprehensive
data on the search for dark matter using a worldwide network of
optical magnetometers. According to the scientists, dark matter
fields should produce a characteristic signal pattern that can be
detected by correlated measurements at multiple stations of the
GNOME network.



FULL STORY ==========================================================================
An international team of researchers with key participation from the
PRISMA+ Cluster of Excellence at Johannes Gutenberg University Mainz
(JGU) and the Helmholtz Institute Mainz (HIM) has published for the
first time comprehensive data on the search for dark matter using a
worldwide network of optical magnetometers. According to the scientists,
dark matter fields should produce a characteristic signal pattern that can
be detected by correlated measurements at multiple stations of the GNOME network. Analysis of data from a one-month continuous GNOME operation
has not yet yielded a corresponding indication.

However, the measurement allows to formulate constraints on the
characteristics of dark matter, as the researchers report in the journal
Nature Physics.


========================================================================== GNOME stands for Global Network of Optical Magnetometers for Exotic
Physics Searches. Behind it are magnetometers distributed around the
world in Germany, Serbia, Poland, Israel, South Korea, China, Australia,
and the United States.

With GNOME, the researchers particularly want to advance the search
for dark matter -- one of the most exciting challenges of fundamental
physics in the 21st century. After all, it has long been known that
many puzzling astronomical observations, such as the rotation speed of
stars in galaxies or the spectrum of the cosmic background radiation,
can best be explained by dark matter.

"Extremely light bosonic particles are considered one of the most
promising candidates for dark matter today. These include so-called
axion-like particles -- ALPs for short," said Professor Dr. Dmitry
Budker, professor at PRISMA+ and at HIM, an institutional collaboration
of Johannes Gutenberg University Mainz and the GSI Helmholtzzentrum
fu"r Schwerionenforschung in Darmstadt. "They can also be considered as
a classical field oscillating with a certain frequency. A peculiarity
of such bosonic fields is that -- according to a possible theoretical
scenario -- they can form patterns and structures. As a result, the
density of dark matter could be concentrated in many different regions
- - discrete domain walls smaller than a galaxy but much larger than
Earth could form, for example." "If such a wall encounters the Earth,
it is gradually detected by the GNOME network and can cause transient characteristic signal patterns in the magnetometers," explained Dr. Arne Wickenbrock, one of the study's co-authors.

"Even more, the signals are correlated with each other in certain
ways - - depending on how fast the wall is moving and when it reaches
each location." The network meanwhile consists of 14 magnetometers
distributed over eight countries worldwide, nine of them provided data
for the current analysis. The measurement principle is based on an
interaction of dark matter with the nuclear spins of the atoms in the magnetometer. The atoms are excited with a laser at a specific frequency, orienting the nuclear spins in one direction. A potential dark matter
field can disturb this direction, which is measurable.

Figuratively speaking, one can imagine that the atoms in the magnetometer initially dance around in confusion, as clarified by Hector Masia-Roig,
a doctoral student in the Budker group and also an author of the current
study.

"When they 'hear' the right frequency of laser light, they all spin
together.

Dark matter particles can throw the dancing atoms out of balance. We
can measure this perturbation very precisely." Now the network of
magnetometers becomes important: When the Earth moves through a spatially limited wall of dark matter, the dancing atoms in all stations are
gradually disturbed. One of these stations is located in a laboratory
at the Helmholtz Institute in Mainz.

"Only when we match the signals from all the stations can we assess
what triggered the disturbance,"said Masia-Roig. "Applied to the image
of the dancing atoms, this means: If we compare the measurement results
from all the stations, we can decide whether it was just one brave dancer dancing out of line or actually a global dark matter disturbance." In the current study, the research team analyzes data from a one-month continuous operation of GNOME. The result: Statistically significant signals did not appear in the investigated mass range from one femtoelectronvolt (feV)
to 100,000 feV. Conversely, this means that the researchers can narrow
down the range in which such signals could theoretically be found even
further than before. For scenarios that rely on discrete dark matter
walls, this is an important result -- "even though we have not yet been
able to detect such a domain wall with our global ring search," added
Joseph Smiga, another PhD student in Mainz and author of the study.

Future work of the GNOME collaboration will focus on improving both
the magnetometers themselves and the data analysis. In particular,
continuous operation should be even more stable. This is important to
reliably search for signals that last longer than an hour. In addition,
the previous alkali atoms in the magnetometers are to be replaced by
noble gases. Under the title Advanced GNOME, the researchers expect this
to result in considerably better sensitivity for future measurements in
the search for ALPs and dark matter.

========================================================================== Story Source: Materials provided by
Johannes_Gutenberg_Universitaet_Mainz. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Samer Afach, Ben C. Buchler, Dmitry Budker, Conner Dailey, Andrei
Derevianko, Vincent Dumont, Nataniel L. Figueroa, Ilja Gerhardt,
Zoran D.

Grujić, Hong Guo, Chuanpeng Hao, Paul S. Hamilton, Morgan
Hedges, Derek F. Jackson Kimball, Dongok Kim, Sami Khamis,
Thomas Kornack, Victor Lebedev, Zheng-Tian Lu, Hector Masia-Roig,
Madeline Monroy, Mikhail Padniuk, Christopher A. Palm, Sun Yool
Park, Karun V. Paul, Alexander Penaflor, Xiang Peng, Maxim
Pospelov, Rayshaun Preston, Szymon Pustelny, Theo Scholtes,
Perrin C. Segura, Yannis K. Semertzidis, Dong Sheng, Yun Chang
Shin, Joseph A. Smiga, Jason E. Stalnaker, Ibrahim Sulai, Dhruv
Tandon, Tao Wang, Antoine Weis, Arne Wickenbrock, Tatum Wilson,
Teng Wu, David Wurm, Wei Xiao, Yucheng Yang, Dongrui Yu, Jianwei
Zhang. Search for topological defect dark matter with a global
network of optical magnetometers. Nature Physics, 2021; 17 (12):
1396 DOI: 10.1038/s41567- 021-01393-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220120125419.htm

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