Scientists have announced the experimental discovery of a tetraneutron, a new and exotic state of matter that could also have useful properties in existing or emerging technologies.
Theoretical physicist James Vary has been waiting for nuclear physics experiments to confirm the reality of a “tetraneutron” that he and his colleagues theorized, predicted and announced for the first time during a presentation in the summer of 2014, followed of a research paper in the fall of 2016.
“Whenever we present a theory, we always have to say that we are waiting for experimental confirmation,” said Vary, a professor of physics and astronomy at Iowa State University.
In the case of four neutrons (very, very) briefly joined in a quantum state or temporal resonance, that day for Vary and an international team of physicists is already here.
The newly announced experimental discovery of a tetraneutron by an international group led by scientists at Darmstadt Technical University in Germany opens the door to new research and could lead to a better understanding of how universe. This new and exotic state of matter could also have useful properties in existing or emerging technologies.
Andrey Shirokov, left, of Moscow State University in Russia, who has been a visiting scientist in the state of Iowa, and James Vary, of the state of Iowa, are part of an international team of nuclear physicists who theorized, predicted, and predicted a four-neutron structure in 2014. and 2016. Credit: Christopher Gannon / Iowa State’s College of Liberal Arts and Sciences
First, how about a definition
Neutrons, probably remember from science class, are uncharged subatomic particles that combine with positively charged protons to form the nucleus of an atom. Well, individual neutrons are not stable and after a few minutes they become protons. Combinations of double and triple neutrons also do not form what physicists call a resonance, a state of matter that is temporarily stable before it decays.
Enter the tetraneutron
Using the supercomputing power of the Lawrence Berkeley National Laboratory in California, theorists calculated that four neutrons could form a resonant state with a lifetime of only 3 × 10 ^ (-22) seconds, less than a thousand. thousandth of a millionth of a second. It’s hard to believe, but that’s long enough for physicists to study it.
This graph shows experimental measurements and theoretical predictions of the energy and width of the tetraneutron, essential properties of this exotic state of matter. Measurements are made in millions of electron volts, a common unit of measurement in nuclear and high-energy physics. The most recent experimental results are the second from the left and are labeled 2022. The theoretical predictions of the research group that includes James Vary of the state of Iowa are the four columns labeled “NCSM” and represent results from different realistic interactions between neutrons. These results were published in 2016 and 2018. Theoretical predictions called “GSM” were published in 2019 by a group based in China. They use a different method that complements the NCSM method. The details of the publication are also listed. Credit: James Vary / Iowa State University
A detail or two
Theorists’ calculations say that the tetraneutron should have an energy of about 0.8 million volts (a unit of measurement common in nuclear and high-energy physics: visible light has energies between 2 and 3 electronvolts). The calculations also said that the width of the represented energy peak showing a tetraneutron would be about 1.4 million volts of electrons. Theorists published later studies indicating that the energy would probably be between 0.7 and 1.0 million volts of electrons while the width would be between 1.1 and 1.7 million volts of electrons. This sensitivity arose from the adoption of different candidates available for neutron interaction.
A recently published article in the journal Nature reports that experiments at the RIKEN Research Institute’s radioactive isotope beam factory in Wako, Japan, found that the energy and width of tetraneutrons were about 2.4 and 1.8 million volts of electrons respectively. Both are larger than the results of the theory, but Vary said that uncertainties in current theoretical and experimental results could cover these differences.
Why is it a big problem
“A tetraneutron has such a short life that it’s a pretty big shock to the world of nuclear physics that its properties can be measured before it breaks,” Vary said. “It’s a very exotic system.”
In fact, it is “a new state of matter,” he said. “It’s short-lived, but it points to possibilities. What if you put two or three together? Could you get more stability?”
Experiments trying to find a tetraneutron began in 2002 when the structure was proposed in certain reactions involving one of the elements, a metal called beryllium. A RIKEN team found clues to a tetraneutron in experimental results published in 2016.
“The tetraneutron will bind to the neutron as only the second uncharged element of the nuclear chart,” Vary wrote in a project summary. This “provides a valuable new platform for theories of strong neutron interactions.”
The papers, please
Meytal Duer, of the Institute of Nuclear Physics at the Technical University of Darmstadt, is the corresponding author of the Nature article – “Observation of a correlated four free neutron system” – announcing the experimental confirmation of a tetraneutron. The results of the experiment are considered a five-sigma statistical signal, denoting a definitive discovery with a 3.5 million chance that the finding will be a statistical anomaly.
The theoretical prediction was published on October 28, 2016 in the journal Physical Review Letters (Prediction for a Four-Neutron Resonance). Andrey Shirokov, of the Skobeltsyn Institute of Nuclear Physics at Moscow State University in Russia, who has been a visiting scientist in the state of Iowa, is the first author. Vary is one of the corresponding authors. Grants from the U.S. Department of Energy, the National Energy Research Scientific Computing Center, the German and U.S. Nuclear Theory Exchange Program, and the Russian Science Foundation supported the theoretical work.
Written with a smile
“Can we create a small neutron star on Earth?” Vary titled a summary of the tetraneutron project. A neutron star is what is left when a massive star runs out of fuel and collapses into a super-dense neutron structure. The tetraneutron is also a neutron structure, one of Vary’s jokes is a “very light, short-lived neutron star.”
A personal reaction
“I had practically abandoned the experiments,” Vary said. “I hadn’t heard anything about it during the pandemic. That was a big shock. My God, here we are, maybe we have something new.”
Reference: “Observation of a correlated system of four free neutrons” by M. Duer, T. Aumann, R. Gernhäuser, V. Panin, S. Paschalis, DM Rossi, NL Achouri, D. Ahn, H. Baba, CA Bertulani, M. Böhmer, K. Boretzky, C. Caesar, N. Chiga, A. Corsi, D. Cortina-Gil, CA Douma, F. Dufter, Z. Elekes, J. Feng, B. Fernandez-Dominguez, US Forsberg, Fukuda N, Gasparic I, Ge Z, Gheller JM, Gibelin J, Gillibert A, Hahn KI, Halász Z, Harakeh MN, Hirayama A, Holl M, Inabe N, Isobe T, Kahlbow J, Kalantar-Nayestanaki N, Kalantar -Nayestanaki, Kim S, Kobayashi T, Kondo Y, Körper D, Koseoglou P, Kubota Y, Kuti I, Li PJ, Lehr C,[PubMed ]Lindberg S., Liu Y., Marquis FM, Masuoka S., Matsumoto M., Mayer J., Miki K., Monteagudo B., Nakamura T., Nilsson T., Obertelli A., NA Orr, H. Otsu, Park SY, Parlog M, Potlog PM, Reichert S, Revel A, Saito AT, Sasano M, Scheit H, Schindler F, Shimoura S, Simon H, Stuhl LH, Suzuki H, D Symochko, Takeda H, Tanaka J, Togano Y , Tomai T, Törnqvist HT, Tscheuschner J, Uesaka T, Wagner V, Yamada H, Yang B, Yang L, Yang ZH, Yasuda M, Yoneda K, Zanetti L, Zenihiro J and Zhukov MV, June 22, 2022, Nature .DOI: 10.1038 / s41586 -022-04827-6
The theorists
In addition to Vary and Shirokov, others involved in the theoretical prediction of a tetraneutron were George Papadimitriou of the Lawrence Livermore National Laboratory in California (and a former postdoctoral research associate in Iowa State); Alexander Mazur of the Pacific National University in Khabarovsk, Russia; Igor Mazur, also of Pacific National University; and Robert Roth of Darmstadt Technical University in Germany.