But soon, the excited expression on Qiao Anhua's face became calm.

"Professor Pang, it is undeniable that your theory is wonderful, but the problem is that we must find the lazy neutrino you mentioned to confirm that your theory is correct. According to the results calculated in your paper, this neutrino has existed for a short time and is difficult to react with other substances. How to design experiments and find it is a huge problem!"

Pang Xuelin smiled faintly and said, "Professor Qiao, do you still remember the mystery of the disappearance of the sun's neutrino?"

"The mystery of the disappearance of the sun's neutrino?"

Qiao Anhua was slightly stunned and his brows frowned slightly.

Of course he knew this famous problem in the history of science.

In the first half of the twentieth century, physicists generally believed that the sun was luminous due to the continuous nuclear fusion reaction from hydrogen to helium.

According to this theory, every 4 hydrogen nuclei (i.e. protons) inside the sun are converted into 1 helium nucleus, 2 positrons and 2 mysterious neutrinos.

It is the energy released by this nuclear fusion reaction that shines and heats, feeding all things on the earth.

As the thermonuclear reaction progresses, neutrinos are continuously released.

Since the mass of 4 protons is greater than the mass of 1 helium nucleus plus 2 positrons and 2 neutrinos, the reaction needs to release a large amount of energy.

A small portion of these energy eventually arrives at the earth in the form of sunlight.

This nuclear reaction is the most frequent reaction inside the sun.

Neutrinos can easily escape from the inside of the sun, and their energy does not appear in the form of light and heat.

Sometimes the neutrino energy produced by thermonuclear reactions is relatively low and the energy taken away is less, so the sun gains more energy.

If the energy of neutrinos is relatively high, the sun will get relatively less energy.

Neutrinos are not charged and have no internal structure.

In the standard model of elementary particle physics, neutrinos have no mass.

There are about 100 billion solar neutrinos per square centimeter per second, but we cannot feel them because the probability of neutrinos interacting with matter is very small. Whenever 100 billion solar neutrinos pass through the earth, only one will interact with the matter that makes up the earth. Since the probability of neutrinos interacting with other particles is minimal, it can easily escape from the sun and directly bring us important information about the internal nuclear reactions of the sun.

There are three different types of neutrinos in nature. The neutrinos produced by the nuclear reaction inside the sun are electron-type neutrinos, and the production of this neutrinos is associated with electrons. The other two neutrinos are muon neutrinos and t-on neutrinos, which can be produced in accelerators or exploded celestial bodies, and are associated with charged muons and t-ons respectively.

In 1964, Raymond Davis and John Baicao proposed an experimental plan to test whether the nuclear reaction that provides solar energy is a fusion reaction.

John Baicao and his colleagues used a fine computer model to calculate the number of sun neutrinos at different energies.

Since the sun's neutrinos react with chlorine to release radioactive argon atoms, they also calculated the number of observations in a giant barrel filled with tetrachloroethylene.

Although this idea seemed a bit unrealistic at the time, Davis believed that using a swimming pool-sized container filled with pure tetrachloroethylene as a detector could measure the amount of argon produced every month predicted by the theory.

Davis' earliest experimental results were published in 1968.

The number of cases he detected was only one-third of the theoretical prediction value. The problem of inconsistent with the experiment in this theoretical prediction was later called the "Sun Neutrino Difficulty", and the more popular saying is "the mystery of the disappearance of neutrinos".

In order to explain the problem of solar neutrinos, people have proposed three possible solutions.

The first solution believes that there may be problems in theoretical calculations, and there may be errors in two places: or there are problems with the solar model, which leads to the wrong number of solar neutrinos predicted by the theory, or the calculated generation rate is problematic.

The second explanation suggests that perhaps Davis's experiment went wrong.

The third solution is the boldest and the most discussed one. It believes that the sun's neutrino itself has changed as it passes through the universe from the sun to the earth.

In the next 20 years, many people carefully calculated the number of solar neutrinos produced. The data used for calculations has been continuously improved, and the results obtained are more accurate.

Finally, it was found that there were no obvious errors in the calculation of the number of neutrinos derived from the solar model and the number of neutrino cases that Davis could detect by the experimental device.

Meanwhile, Davis improved the experimental accuracy and conducted a series of different tests to confirm that he did not ignore certain neutrinos.

No error was found in his experimental device. The problem of inconsistency between experiments and theory has not been solved.

The third explanation mentioned above was proposed by former Soviet scientists Bruno Pontekwe and Vladimir Gliboff in 1969.

This idea suggests that the properties of neutrinos are not as simple as physicists originally thought, that neutrinos may have static mass and that different types of neutrinos can transform into each other, the latter known as neutrino oscillation.

When this idea was first proposed, it was not accepted by most physicists. But over time, more and more evidence began to tend to the existence of neutrino oscillations. This is a new physics beyond the framework of the Standard Model.

In 1989, 20 years after the first solar neutrino experiment results were released, a Japanese-US experimental group led by Masato Toshiko and Yoji Tozuka (Kamikaoka cooperation group). They filled the huge detector with pure water to detect the scattering rate between electrons in the water and high-energy neutrinos from the sun.

This experimental device has high accuracy, but can only detect high-energy solar neutrinos. This high-energy neutrinos come from a relatively rare process in the internal thermonuclear reaction of the sun, namely the decay of elements. Davis's initial experimental device used chlorine, but could also detect neutrinos in this energy region.

The Kamioka experiment verified that the number of observed neutrinos is indeed less than the theoretical prediction value of the solar model, but the degree of inconsistency between the theory and experiment is smaller than that of Davis's experiment.

Over the next 10 years, three new solar neutrino experiments have made the problem of neutrino disappearance more complicated.

The Gallex Laboratory, led by German Til Kstan, and the Sage Laboratory led by Vladimir Glibow, respectively used detectors filled with gallium to detect low-energy solar neutrinos, and found that low-energy neutrinos also had the problem of loss.

In addition, the Super Kaguoka Experiment led by Yoji Tozuka and Yoichiro Suzuki used a huge detection device containing a total of 50,000 tons of water to conduct more precise measurements of high-energy solar neutrinos, convincingly confirming the neutrino loss phenomenon observed by Davis's experiment and Kaguoka Experiment.

In this way, both high-energy solar neutrinos and low-energy solar neutrinos are missing, but the proportion of losses is different.

At 12:15 noon on June 18, 2001, a neutrino experimental team composed of American, British and Canadian scientists led by Canadian Arthur MacDonald announced an exciting news: they solved the solar neutrino problem.

The international cooperation team used 1,000 tons of heavy water to detect neutrinos.

The detector is placed in a mine 2,000 meters deep underground in Sudbury, a southern Canadian city. They used a new method different from the Kamioka experiment and the Super Kamioka experiment to detect solar neutrinos in high-energy areas. This experiment is called the Sno experiment.

In Sno's initial experiment, the heavy water detection device they used was in a state that was sensitive to electron neutrinos only.

The number of electron neutrinos observed by scientists in Sno is about one-third of the predicted value of the standard solar model. The previous Super Kaguoka experiment is not only sensitive to electron neutrinos, but also has certain sensitivity to other types of neutrinos, so the number of observed neutrinos is about half of the theoretical expected value.

If the standard model is correct, Sno's experimental results should be consistent with that of Super Kanoka, that is, all neutrinos from the sun should be electron neutrinos. The results of the two experiments are inconsistent, indicating that the standard model that describes the properties of neutrinos is problematic, at least incomplete.

Combining the experiments of Sno and Super Kaguoka, the Sno collaboration not only determined the number of electron neutrinos, but also determined the total number of three types of neutrinos from the sun, and the results were consistent with the predictions of the solar model.

Electron neutrinos account for one-third of the total number of all neutrinos.

In this way, the problem is clear: although the number of electron neutrinos observed on the ground accounts for only one-third of the total number of sun neutrinos, the latter has not decreased; the lost electron neutrinos did not "disappear", but just turned into difficult to detect muon neutrinos and t-on neutrinos.

This epoch-making result was published in June 2001 and was soon supported by a series of other experiments.

The sno team measured the number of all three high-energy neutrinos on their heavy water detection device, which was unique at the time. Their experimental results showed that most neutrinos were generated inside the sun and were electron neutrinos when they were produced.

When they reach the earth, some electron neutrinos are converted into muon neutrinos and t-on neutrinos.

The key to the sno experiment is to measure the total number of three neutrinos. It is precisely because the total number of three neutrinos is determined that physicists can convincingly explain the mystery of the disappearance of the sun's neutrinos without relying on specific theoretical models.

...

"Professor Pang, what do you mean is that the existence of this inert neutrino can be found through the experiment of solar neutrinos?"
Chapter completed!