Four neutron confirmation!

The following article comes from the WeChat public account: principle, author takeko

Narrows are one of our most familiar particles. It seems to be a relatively "low -key" particle, but it actually hides a lot of interesting secrets to be discovered.

As early as 1920, Lutherford predicted the existence of neutron for the first time. Subsequently, after more than 10 years of painful struggle and almost "granular no harvest" experiments, Chadwick finally discovered this most elusive component in the atom.

The neutron is a sub -atomic particle without charge, which can be combined with a proton with positive electrical electrical electrical electrical electrical. Those free neutrons that are not restrained usually decline after about 15 minutes to produce protons, electronics and anti -neutrinos.

A long -term problem in nuclear physics is whether the non -power nuclear system can exist. At present, we know that in nature, only the neutron star represents the almost complete pure neutron system. It is a super -dense celestial body formed by the full quality star fuel. Together, reach extremely high density.

For decades, the exploration of the experimental exploration of the isolated multi -neutron system has been conducting. Until now, a group of international research teams passed the experimental observation and confirmed the four neutron systems. This result not only verifies the previous theoretical predictions, but also opened the door for new studies, which may give us a deeper understanding of how the universe constituted. The paper has been published in "Nature" recently.

From theoretical prediction to experimental verification

After many years of experiments and basic research, scientists have found that the combination of double neutron and three neutrons will not form resonance, which is a material state that is temporarily stable before decay.

However, the exploration of the four neutron systems, that is, the temporary quantum or resonance that combines the four neutron very, is very short, has continued for more than half a century. But most of these search returned.

The turn of the matter occurred in 2002. At that time, some reactions involved in the metal metal at the Ganil (national heavy ion accelerator) in France at that time found 6 events that could be explained as four neutrons. But unfortunately, repeated experiments failed. Some scientists believe that at least some of the original data analysis may have problems.

The new stage of the four middle searches began in 2016. In Japan's RIBF (radioactive ion beam factory), scientists use the ⁸He nuclear bombardment ⁴He target. The collision result is that the α particles (⁴He nucleus) are hit from ⁸He, leaving a system of four neutron composition. The experiments were initially discovered by four incidents suspected of somewhat resonance.

The α particles were hit out of the 子 子, leaving the four neighbors. (Figure / Andrey Shirokov)

In the same year, a group of international theoretical scholars published the theoretical predictions about the four neutron in the "Physics Review Express". With the help of the computing power of supercomputers, the theoretical calculation of the four neutron system based on the new calculation method and the interaction of new neutrons.

Studies believe that the life expectancy of the four middle sub -systems is only about (3 ~ 5) × 10 -second. This is incredible. But for physicists, this is long enough.

Theoretical scholars have also found that the four neutron should have about 800,000 electronic volt energy. As a comparison, the energy of visible light is about 2 to 3 electronic volts. The width of the four neutron energy peaks drawn is about 1.4 million electron volt.

Some subsequent research further restricted the energy between 700,000 and 1 million electron volt, while the width was between 1.1 million and 1.7 million electron volt. This sensitivity is caused by different neutron interaction candidates.

This picture shows the experimental measurement and theoretical prediction of the energy and width of the four neutrons, and is based on a million electron volt. The latest experimental results are second from the left (2022). The picture also shows different theoretical predictions, representing the results of the interaction between various reality. The corresponding research papers show the blue text in the figure. (Photo / iow state university)

In this new study, the experimental results took a big step forward.

Scientists observed in the experiment that the energy and width of the four neutrons were about 240 and 1.8 million electron volt, respectively. They are actually larger than the results of theoretical prediction, but researchers believe that considering the uncertainty of the current theory and experimental results, this difference can be included.

The result of this experiment is considered a statistical signal of 5σ. In other words, it is likely to have one -inch of 3.5 million in statistical abnormalities. This can be considered a certain discovery and confirmed the existence of the four neighborhoods in the experiment.

"Micro neutrons"

Scientists believe that the four neutron is a very strange system that can be called a brand new material state. Although its life span is short, it points to various possibilities, which also provides a valuable new platform for studying the theory of strong interaction between middle schools.

The four neutrons and neutron stars are a pure neutron structure. The researchers joked that it was like a "short life, very light micro -neutron star". What if you put two or three things together? Can you get greater stability? Or further, can we create a small "neutron star" on the earth?

#Groupe OD creation:

Written article: takeko

Capture: Wenwen#Reference Source:

https://www.news.iastate.edu/news/2022/06/22/Tetraneutron

https://www.eurekalert.org/news-releases/470699

https://www.nature.com/articleS/S41586-022-04827-6-6

https://journals.Aps.org/prl/abstract/10.1103/physrevlett.117.182502

#Image Source:

Cover & First Figure: Andrey Shirokov, Lomonosov Moscow State University

This article is authorized to reprint from WeChat public account: Principle (ID: Principia1687) Author: takeko

Reprinted content only represents the author's point of view

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It does not represent the high energy office of the Chinese Academy of Sciences

Edit: Liu Ming

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