MTL - The Science Fiction World of Xueba-Chapter 511 Neutrino

Shen Jing thought about it and said, "Okay, then let's say it. If you still can't think of a way to save me a year later, then you must agree to my request."

Pang Xuelin smiled: "No problem."

The next time, the two put down their respective thoughts and began to enjoy this holiday trip with ease.

Because of the flying cars, the complex landscape of the Qinghai-Tibet Plateau is no longer an obstacle.

The towering Himalayas, the winding Yarlung Zangbo Grand Canyon, and the large and small lakes like sapphires inlaid on the Qinghai-Tibet Plateau allow Pang Xuelin and Shen Jing to fully appreciate the beauty of the roof of the world.

It was just a surprise to Pang Xue that Shen Jing was not as sentimental as the one shown in the book. He felt that he would be trapped in the earth forever, and the surface world looked at one less thing, but Shen Jing was quite open, not Too much care.

While Pang Xuelin was surprised, he secretly lamented that the crew members who could be selected for the sunset series of spaceships are very human.

At the same time, Pang Xuelin also faintly realized that the reason why Zhong Shen Jing had that kind of performance was more likely that when the male lead Shen Jing went to the grassland, Shen Jing was trapped in the ground soon, and his mentality had not fully adapted to the life of the ground.

And now, she is ready to live in the earth for the rest of her life. When she looks at the outside world, her mood will naturally be different.

After completing the three-day journey, Pang Xuelin returned to the base with Shen Jing's "eyes", told Shen Yuan that he and Shen Jing were gambling, and let Shen Yuan interrupt the communication between the base and the sunset.

Although Shen Yuan was curious about how Pang Xuelin found a way to save the sunset on the 6th, but since Pang Xuelin didn't say it, Shen Yuan wasn't much to ask for a while.

Afterwards, Pang Xuelin bid farewell to Shen Yuan and returned to the capital. As the deputy chief engineer of the Earth Cannon Engineering, he went to the Institute of High Energy Physics of the Chinese Academy of Sciences to start research on neutrinos.

Although the overall technological level of this world is higher than that of the real world, the gap between the two in the fields of basic physics and basic mathematics is not large.

Similar to the real world, in this world, after the discovery of the Higgs boson, particle physics has entered a new stage.

The Higgs boson is the last component of the standard model of particle physics. Its discovery means the end of an era and heralds the beginning of a new era.

The standard model is a theoretical system that systematically describes the entire particle physics and has been tested by a large number of experiments.

After finding the Higgs particles, the standard model is getting closer to perfection, with beautiful structure and amazing prediction ability.

But on the other hand, there are phenomena that cannot be accommodated or difficult to explain by some standard models such as dark matter, dark energy, asymmetry of positive and negative matter in the universe, and mass of neutrinos, indicating that there must be new physics beyond the standard model.

In the standard model, neutrinos have no mass.

The discovery of neutrino oscillation indicates that neutrinos have mass.

This is the only phenomenon discovered so far that has solid experimental evidence beyond the standard model.

There are three types of neutrinos, namely electron neutrinos, m neutrinos, and t neutrinos.

In the standard model their mass is zero.

In 1956, Li Zhengdao and Yang Zhenning predicted that the weak effect parity is not conserved, that is, the left-right asymmetry of the space, which was quickly confirmed by Wu Jianxiong through experiments.

Experiments also found that parity is not only not conserved but also the most destructive in weak action.

The essence of this phenomenon is that there are only neutrinos with left-handed helicity (that is, its spin is always opposite to the direction of motion), and there are no right-handed neutrinos.

This can only be established if the mass of the neutrino is zero, because if the mass is not zero, then the speed of the neutrino must be less than the speed of light. You can choose a reference frame that is faster than it to let its helicity develop

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According to this phenomenon, Li Zhengdao and Yang Zhenning proposed the two-component theory of neutrinos, which gave birth to the weak-acting V-A theory, which was inherited by the standard model and was in good agreement with various experimental data.

Therefore, in the standard model, neutrinos have no mass.

However, in 1998, the Super-K experiment in Japan (Super-K) found that there were oscillations of atmospheric neutrinos, that is, neutrinos could become other types of neutrinos in flight.

Together with the earlier mystery of the disappearance of solar neutrinos, the results of later experiments such as SNO (solar neutrinos), (reactor neutrinos), and K2K (accelerator neutrinos) formed neutrino oscillations. Solid evidence.

The neutrino oscillation shows that neutrino has mass, but it is very, very small, so that even at the level of human science and technology in this world, there is still no way to accurately measure the quality of neutrino.

Incorporating the mass of neutrinos into the standard model does not seem to be a big problem. It seems to be enough to add a mass term to it like electrons.

But there will be two problems immediately.

One question is how to add. The neutrino spin is 1/2, which is fermion.

Other fermions are charged, while neutrinos are not charged.

In this way, the neutrino can be a Dirac particle like other fermions, with a Dirac mass term, or it can be a special Majorana particle, that is, its antiparticle is itself, but the helix is ​​opposite .

Another problem is that the mass of the neutrino is too small. If a Dirac mass term is simply added, its mass is one trillion times different from the heaviest top quark.

The same Higgs particle needs to produce not only a mass as large as the top quark but also a mass as small as the neutrino. It is hard to believe such a wide gap.

There is a kind of theory that is popular with physicists. It is called "seesaw mechanism". It assumes that the neutrino is a Majorana particle, and there are still undiscovered heavy neutrinos whose mass is much larger than the weak electric energy scale. The tiny mass of neutrinos can be explained naturally.

However, heavy neutrinos cannot be filled into the three-generation structure of the standard model.

Whether it is for the physics community of this world or the physics community on earth, there are a lot of mysteries of neutrinos yet to be solved.

First, its mass has not been directly measured and its size is unknown; secondly, it is unknown whether the neutrino and its antiparticle are the same particle; third, there are two parameters of the neutrino oscillation that are not measured, and this The two parameters are probably related to the mystery of the lack of antimatter in the universe; fourth, whether it has a magnetic moment; and so on.

Therefore, neutrino has become the intersection and hot subject of particle physics, astrophysics, cosmology and geophysics.

At present, there are two main applications of neutrino in this world.

One is neutrino communication.

Since the earth is spherical, coupled with the occlusion of surface structures and terrain, the transmission of electromagnetic wavelength distances must pass through communication satellites and ground stations. UU reading www.uukanshu. com

The neutrino can penetrate the earth directly, and it has very little loss when passing through the earth. The neutrino that produces 1 billion electron volts with a high-energy accelerator only attenuates by a thousandth when passing through the earth, so neutrino can be used from South America The sub-beam passes directly through the earth to China.

By modulating the neutrino beam, it can contain useful information and communicate at any two points on the earth without expensive and complicated satellites or microwave stations.

The second application is the neutrino earth tomography, or stratum CT.

The cross section of neutrino-matter interaction increases with the increase of neutrino energy. A high-energy accelerator generates a neutrino beam with an energy of more than 1 trillion electron volts to irradiate the formation directionally. The interaction with the formation material can produce a local small "earthquake" Similar to seismic exploration, deep formations can also be surveyed, scanning the formations layer by layer.

However, the accuracy of this earth tomography scan is quite limited, and the error reaches tens of kilometers. Under this condition, if you want to lock the position of the sunset 6 in the core through the formation CT, it is tantamount to finding a needle in a haystack.

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