The Science Fiction World of Xueba - Chapter 512

In the following month, Pang Xuelin locked himself in the expert building of the Institute of High Energy Physics, Chinese Academy of Sciences and studied the papers on the basic physics of the world and the neutrino theory brought out from the world of Whale Song.

In this regard, the gains are not small.

In the “Earth Cannon” world, neutrino technology is the most widely used area in neutrino communication.

In the “Whale Song” world, neutrino technology is the most widely used field of detection. Instead, scientists use neutrino detectors to detect drugs in various layers.

In principle, both use high-energy proton accelerators to accelerate protons to obtain hundreds of billions of electron volts of high-energy electron beams. Then use it to bombard the target, thereby generating unstable particles.

Through continuous changes, these particles finally form neutrinos and other particles, and then pass them through a thick steel plate to sieve out the charged particles to obtain an uncharged neutrino beam.

Neutrino communication is to let these neutrinos pass through the water. At that time, the water will emit blue light, which is received by the photomultiplier, and the information can be obtained.

Neutrino detection is to determine the composition of different media through different photoelectric signals radiated by neutrinos passing through different media.

There is no big difference in the fundamental principles of the two.

However, Pang Xuelin found that the study of particle physics in the world of “Whale Song” is more neutrino than the world of “Earth Cannon”, that is, heavy neutrino.

As we all know, neutrinos are the same as electrons, muons, and τons, and there are several ways to produce neutrinos in the universe. One is native, produced during the Big Bang, and is now a neutrino with a very low temperature background.

The second type is the supernova explosion giant celestial activity, which is produced during the gravitational collapse process from the combination of protons and electrons into neutrons. This is the SN1987A neutrino.

The third type is neutrinos below a dozen MeV produced by light nuclear reactions on stars such as the Sun.

The fourth type is that high-energy cosmic ray particles hit the atmosphere and undergo nuclear reactions with the nuclei in them, producing π and K mesons. These mesons decay to produce neutrinos, which are called “atmospheric neutrinos”.

Fifth, high-energy protons in the cosmic rays collide with photons radiated by the cosmic microwave background to produce π mesons. This process is called “photo-induced pi mesons”. The decay of π mesons produces high-energy neutrinos, which have extremely high energy.

The sixth type is that cosmic ray high-energy protons hit the nucleus of the astral cloud or interstellar medium to produce a nuclear reaction. The mesons decay into neutrinos, especially in some neutron stars, pulsars and other stars.

The seventh type is the neutrinos produced by the spontaneous or induced fission product β decay on the earth. Such neutrinos are rare.

Although they are produced in different ways, through observation of the Z boson, scientists have discovered that neutrinos have three “flavors”: electric neutrinos (νe), μ neutrinos (νμ), and τ neutrinos (ντ) .

There is an anti-neutrino with the same charge neutrality and spin quantum number for each neutrino of each flavor.

In the standard model, the neutrino generation process follows the law of conservation of lepton numbers.

Because neutrinos are electrically neutral and also a lepton, they do not participate in strong interactions and electromagnetic interactions, but only participate in gravitational interactions and weak interactions.

The weak interaction distance is very short, and the gravitational interaction is very weak at the subatomic scale. Therefore, neutrinos will not be hindered too much when passing through general matter, and are difficult to detect.

At present, neutrinos can be produced by radioactive decay and nuclear reactions.

Nuclear reactions occur all the time inside the sun, and supernova generation and other processes are accompanied by violent nuclear reactions, so the presence of neutrinos can be detected in cosmic rays.

Most neutrinos detected near the earth originate from the sun.

In fact, the area of ​​the earth facing the sun passes through 65 billion neutrinos from the sun every square centimeter every second.

It is now recognized that neutrinos will oscillate between different flavors during flight, for example, electrical neutrinos generated in beta decay may become mu neutrinos or τ neutrinos during detection.

This phenomenon indicates that neutrinos have quality, and the quality of neutrinos with different flavors is also different.

According to the data of the current cosmological exploration, the sum of the masses of the three flavored neutrinos is less than one millionth of the mass of electrons.

Further research has found that neutrinos (ie, mass eigenstates) m1, m2, and m3 with definite quality are not the same as taste eigenstates—electric neutrinos, μ neutrinos, and τ neutrinos. correspond.

For example, m1 with a certain quality can be regarded as a combination of three flavored neutrinos in a certain ratio, and electronic neutrinos with a certain flavor are also composed of three different quality neutrinos.

It is this mixing that causes the neutrino to oscillate.

The oscillation of the third-generation neutrino can be described by six parameters, including two mass square differences, three mixing angles and a CP destruction phase angle.

The solar neutrino experiment measured m2^2-m1^2=7.5×10-5eV^2 and the mixing angle sin^2β12=0.86, and the atmospheric neutrino experiment measured m3^2-m2^2|=2.4× 10^-3eV^2 and sin^2β23≈1.

In the real world, the last mixing angle sin^2β13=0.09 was measured in the Daya Bay reactor neutrino experiment led by academician Wang Yifang of the Chinese Academy of Sciences.

In the “Whale Song” world, humans have measured the parameters of the neutrino CP destruction phase angle. At the same time, it also determines the quality order (or quality level) of m1, m2 and m3.

And on this basis, thoroughly understand the properties of electric neutrinos, μ neutrinos and τ neutrinos.

But there is a problem in it. Scientists in the world of “Whale Song” found that, according to the measured results, there should be a fourth kind of neutrino in theory. They named this neutrino as heavy neutrino. , Also known as inert neutrinos.

Under the existing conditions, the best measurement result for the number of neutrino species comes from the observation of the decay of the Z boson.

This kind of particle decay will produce various types of light neutrinos and their corresponding antineutrinos~www.mtlnovel.com~ And the more light neutrinos produced, the shorter the Z boson lifetime. .

But the existence of inert neutrinos cannot be determined by observing the decay of Z bosons.

The observation data of the microwave background radiation obtained by the microwave anisotropy detector is compatible with three or four neutrinos simultaneously.

…

Heavy neutrino!

Pang Xuelin wrote these four large characters on the manuscript paper and circled them.

No matter in the world of “Whale Song” or in the world of “Earth Cannon”, humans have failed to observe the existence of heavy neutrinos in experiments.

Pang Xuelin faintly felt that this heavy neutrino is probably the key to the development of a new generation of formation neutrino CT detection instruments.

The question is, how do you find the heavy neutrino described in the paper?

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