Posted on Mar 28, 2019
While they are thought to be everywhere, axions are virtually ghost-like, having only tiny interactions with anything else in the universe. "As dark matter, they should not affect your everyday life," says physicist Lindley Winslow.
Physicists from MIT and elsewhere have the the axions-hypothetical particles that are predicted to be among the lightest particles in the universe. If they exist, axions would be virtually invisible, yet inescapable;
Axions are particularly unusual in that they are expected to modify the rules of electricity and magnetism at a minute level. In a paper published today in Physical Review Letters, the MIT-led team reports that in the first month of observations the experiment detected no axions within the range of 0.31 to 8.3 nanoelectronvolts.
"This is the first time anyone has looked at this axion space, "says Winslow, principal investigator of the experiment and the Jerrold R. Zacharias Career Development Assistant Professor of Physics at MIT. "Mounting Suspense" Consistent Detection of a Dark-Matter Signal ” width=”928″ height=”522″ srcset=”https://dailygalaxy.com/wp-content/uploads/2019/03/galaxia-vulcao-espaco-20100820-original1.jpeg 928w, https://dailygalaxy.com/wp-content/uploads/2019/03/galaxia-vulcao-espaco-20100820-original1-300×169.jpeg 300w, https://dailygalaxy.com/wp-content/uploads/2019/03/galaxia-vulcao-espaco-20100820-original1-768×432.jpeg 768w” sizes=”(max-width: 928px) 100vw, 928px” />
Winslow's co-authors include lead author Jonathan Ouellet, Chiara Salemi, Zachary Bogorad, Janet Conrad, Joseph Formaggio, Joseph Minervini, Alexey Radovinsky, Jesse Thaler, and Daniel Winklehner, along with researchers from eight other institutions.
Because of their interaction with electromagnetism, the axons are theorized to behave in a magnetic field.
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In 2016, a trio of MIT theorists drew up a thought experiment for detecting axions, inspired by the magnetar. The experiment was dubbed ABRACADABRA, for the A Broadband / Resonant Approach to Cosmic Axion Detection with Amplifying B-field Ring Apparatus, and what is conceived by Thaler, who is an associate professor of physics and a researcher in the Laboratory for Nuclear Science and the Center for Theoretical Physics, along with Benjamin Safdi, then MIT Pappalardo Fellow and former graduate student Yonatan Kahn.
The team proposed a design for a small, donut-shaped magnet kept in a refrigerator at just above absolute zero. Winslow puts it, "where the munchkin should be." However, if axions exist, a detector should "a magnetic field in the middle of the donut.
Winslow, an experimentalist, set about finding ways to actually build the experiment.
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"We wanted to look for a signal of an axion where, if we see it, it's really the axion," Winslow says. "That's what was elegant about this experiment. Technically, if you saw this magnetic field, it could only be the axion because of the particular geometry they thought of. "
It is a challenging experiment because the expected signal is less than 20 atto-tesla. For reference, the Earth's magnetic field is 30 micro-Tesla and human brain waves are 1 pico-Tesla. In building the experiment, Winslow and her colleagues had to contend with two main design challenges. Winslow worried could mask an axion signal.
The second challenge had to do with noise in the environment, as well as nearby radio stations, electronics throughout the building Turning on and off, and even
The first problem is by hanging the entire contraption, using a thread as thin as a dental floss.
"We could finally take data, and there was a sweet region in which we were above the vibrations of the fridge,
The researchers first ran a series of tests to confirm the experiment. The most important test of the invention is that of the experimental signal that it would produce. At this point the experiment was ready to go.
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"If you take the data and run it through an audio program, you can hear the sounds that make the fridge," Winslow says. "So we see other noise going on and off, from someone next door doing something, and then that noise goes away. In 1968, the team carried out ABRACADABRA's first run, continuously sampled between July and August. After analyzing the data from this period, they found no evidence of axions within the range of 0.31 to 8.3 nanoelectronvolts that change electricity and magnetism by more than one part in 10 billion.
The experiment is designed to detect axons of even smaller masses, down to about 1 femtoelectronvolts, as well as axions as large as 1 microelectronvolts.
The team wants to continue running the current experiment, which is about the size of a basketball, to look for even smaller and weaker axions. Meanwhile, Winslow is in the process of figuring out how to scale it up to the size of a compact car-dimension.
"There is a real possibility of a big discovery in the next stages of the experiment, "Winslow says. "What motivates us is the possibility of seeing something which would change the field. It's high-risk, high-reward physics. "
The supergiant elliptical galaxy M87 in the constellation Virgo, one of the most massive galaxies in the world clusters. M87 is in the X-ray from Chandra (blue) and in radio emission from the Very Large Array (red-orange). Astronomers use the X-ray emission from M87 to hopefullt the properties of axions. (X-ray NASA / CXC / KIPAC / N. Werner, E. Million et al., Radio NRAO / AUI / NSF / F. Owen)
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