July 2, 2022

Theoretical calculations have predicted the now confirmed tetraneutron, a strange state of matter

Theoretical calculations have predicted the now confirmed tetraneutron, a strange state of matter

Andrey Shirokov, left, of Moscow State University in Russia, who was a visiting scientist in Iowa, and James Fary of Iowa, part of an international team of nuclear physicists who theorized, predicted and announced the tetraneutron structure in 2014 and 2016 .Credit: Christopher Gannon / Iowa State University College of Liberal Arts and Sciences

James Farey was waiting for nuclear physics experiments to confirm the reality of the “tetraneutron” that he and his colleagues theorized, predicted, and first reported during a presentation in the summer of 2014, followed by a research paper in the fall of 2016.


“When we present a theory, we always have to say we are waiting for experimental confirmation,” said Fary, a professor of physics and astronomy at Iowa State University.

If four (very, very) neutrons are bound together for a brief period in a temporary quantum state or echoon that day for Vary and an international team of theorists now exist.

The just-announced experimental discovery of a quadrotron by an international group led by researchers from Germany’s Technical University of Darmstadt opens the doors to new research and could lead to a better understanding of how the universe is held together. This new and exotic state of matter could also have useful properties in current or emerging technologies.

Neutrons, you might remember from science class, are subatomic particles Without a charge, it combines with the positively charged protons to form the nucleus of an atom. The individual neutrons are not stable and after a few minutes they turn into protons. The combinations of double and triple neutrons also do not form what physicists call resonance, a state of matter temporarily stable before it decays.

Enter the tetraotron. Using supercomputing power at Lawrence Berkeley National Laboratory in California, theorists have estimated that four neutrons can form a buzz state with a lifetime of only 3 x 10-22 Seconds, less than a billionth of a billionth of a second. It’s hard to believe, but that’s long enough for physicists to study it.

Theorists calculate that the tetratron should have an energy of about 0.8 million electronvolts (a common unit of measurement in nuclear physics and high energy – visible light has energies of about 2 to 3 electronvolts.) The calculations also stated the width of the schematic energy spike showing that the tetratron It would be about 1.4 million electron volts. Theorists published subsequent studies that indicated that the energy would likely lie between 0.7 and 1.0 MeV, while the width would be between 1.1 and 1.7 MeV. This sensitivity arose from the adoption of two different candidates available for the interaction between neutrons.

A paper just published in the magazine temper nature Reports indicate that experiments conducted at the Radioisotope Radiation Factory at the RIKEN Research Institute in Wako, Japan, found that the energy and width of the tetratron are about 2.4 and 1.8 million electronvolts, respectively. Both are greater than the theory results but Fary said the uncertainty in current theoretical and experimental results could cover these differences.

“The life of the tetratron is short, it’s too big a shock to the nuclear physicist world that its properties can be measured before it breaks down,” Fary said. “It’s a very strange system.”

It is, in fact, “completely new state of matter“It didn’t last very long,” he said, “but it does point out the possibilities. What happens if you put two or three of those together? Can you have more stability?”

Experiments trying to find the tetratron began in 2002 when the structure was proposed in certain reactions involving one of the elements, a metal called beryllium. A team at RIKEN found hints of tetratron in experimental results published in 2016.

“The tetratron will join the neutron as only the second element in the nuclear graph,” Fary wrote in the project summary. This “provides a valuable new platform for theories of strong interactions between neutrons.”

Mittal Doer of the Institute of Nuclear Physics at the Technical University of Darmstadt is the corresponding author of temper nature A paper entitled “Observing a free bound tetraneutron system” and announcing experimental confirmation of a tetraneutron. The results of the experiment are a five-sigma statistical indication, indicating a definitive finding with a probability of 1 in 3.5 million that the result is a statistical anomaly.

Theoretical prediction was published on October 28, 2016 in Physical Review LettersEntitled “Prediction of Tetraneutron Resonance”. Andrei Shirokov of the Skoplitsyn Institute of Nuclear Physics at Moscow State University in Russia, who was a visiting scientist in Iowa, is first author. Fary is one of the corresponding authors.

“Can we create a small neutron star on Earth?” Differ titled Summary of the Tetraneutron Project. A neutron star is what is left over when a massive star runs out of fuel and collapses into a super-dense neutron structure. A tetratron is also a neutron structure, one variant jokingly being “a short-lived, very light neutron star.”

Personal reaction varies? “I’ve pretty much given up on experiments,” he said. “I haven’t heard anything about this during the pandemic. This came as a huge shock. Oh my gosh, here we are, we may already have something new.”


Physicists prove the existence of a new subatomic structure


more information:
Doerr et al., Observation of a correlative free neutron system, temper nature (2022). DOI: 10.1038 / s41586-022-04827-6

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Iowa State University

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