Shen Jing thought for a while and said, "Okay, then let's talk about it, if you still can't think of a way to save me after a year, then you must agree to my request." ”

Pang Xuelin smiled: "No problem." ”

In the following time, the two put aside their minds and began to enjoy the holiday trip in a relaxed way.

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

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

It's just that Pang Xue was a little surprised that Shen Jing was not as sentimental as it was shown, and Shen Jing was quite open to the fact that he would be permanently trapped in the center of the earth and look at the surface world without a glance, and he didn't care too much.

While Pang Xuelin was surprised, he also secretly sighed that the crew members who could be selected for the Sunset series of ground spacecraft were very human.

At the same time, Pang Xuelin also faintly realized that the reason why Shen Jing had that kind of performance was more likely to be that when the male protagonist took Shen Jing to the grassland, Shen Jing was trapped in the center of the earth not long ago, and his mentality had not fully adapted to the life in the center of the earth.

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

At the end of the three-day journey, Pang Xuelin returned to the base with Shen Jing's "eyes", told Shen Yuan about his gamble with Shen Jing, and asked Shen Yuan to interrupt the communication between the base and Sunset Six.

Although Shen Yuan was curious about how Pang Xuelin could find a way to save Sunset Six within a year, since Pang Xuelin didn't say it, Shen Yuan didn't want to ask much for a while.

Subsequently, Pang Xuelin bid farewell to Shen Yuan, returned to the capital, and went to the Institute of High Energy Physics of the Chinese Academy of Sciences as the deputy chief engineer of the Earth Cannon Project, and began research on neutrinos.

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

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

The Higgs boson, the last component of the Standard Model of particle physics, was discovered, signaling the end of an era and the beginning of a new era.

The Standard Model is a system of theories that systematically describe the entire particle physics and has been tested by a large number of experiments.

After the discovery of the Higgs particle, the Standard Model was nearly perfected, with a beautiful structure and amazing predictive power.

On the other hand, there are some phenomena that cannot be accommodated by the Standard Model, such as dark matter, dark energy, cosmic positive and antimatter asymmetry, and neutrino mass, or are difficult to explain, indicating that there must be new physics outside the Standard Model.

In the Standard Model, neutrinos have no mass.

The discovery of neutrino oscillations shows that neutrinos have mass.

This is the only phenomenon that has been found to have solid experimental evidence beyond the standard model.

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

In the standard model, they have zero mass.

In 1956, Tsung-Dao Lee and Chen-Ning Yang predicted that the weak effect of the universe is not conserved, that is, the left and right asymmetry of space, which was quickly confirmed by Wu Chien-shiung experimentally.

Experiments have also found that in the weak action, the universal symmetry is not only not conserved, but also the most destructive.

The reason for this phenomenon is essentially that there are only left-handed neutrinos with helix (i.e., their spin is always opposite to the direction of motion), and there are no right-hand neutrinos.

This can only be true if the neutrino has a zero mass, because if the mass is not zero, then the velocity of the neutrino must be less than the speed of light, and you can choose a reference frame that is faster than it and let it spiral

Raw flipping.

Based on this phenomenon, Tsung-Dao Lee and Chen-Ning Yang proposed the two-component theory of neutrinos, which in turn gave rise to the V-A theory of weak action, which was inherited by the Standard Model and is in good agreement with various experimental data.

Therefore, in the Standard Model, neutrinos have no mass.

However, in 1998, Japan's Super-Kamiokande experiment (Super-K) discovered that atmospheric neutrinos oscillate, that is, neutrinos can transform into other kinds of neutrinos in flight.

Together with the earlier mystery of the disappearance of solar neutrinos, the results of experiments with SNO (solar neutrino), KamLAND (reactor neutrino), K2K (accelerator neutrino), etc., form solid evidence of neutrino oscillation.

Neutrino oscillations indicate that neutrinos have mass, but they are very, very small, so that even with the level of human technology in this world, there is still no way to accurately measure the mass of neutrinos.

Including neutrino mass in the Standard Model doesn't seem like a big deal, and adding a mass term to it like an electron seems fine.

But there are two problems that come into it right away.

One question is how to add. The neutrino spin is 1/2 and is a fermion.

All other fermions are charged, whereas neutrinos are not charged.

In this way, the neutrino can be a Dirac particle, like other fermions, with a Dirac mass term, or a special Majorana particle, i.e. its antiparticle is itself, but the helicity is reversed.

Another problem is that the neutrino mass is too small, and if you simply add a Dirac mass term, then its mass is a trillion times different from the heaviest top quark.

The same Higgs particle has to produce a mass as large as a top quark and a mass as small as a neutrino, and such a huge difference is hard to believe.

There is a popular theory among physicists, called the "seesaw mechanism", which assumes that neutrinos are Majorana particles and that there are heavy neutrinos that have not yet been discovered and whose masses are much larger than the electroweak energy target, so that the tiny masses of neutrinos can be explained naturally.

However, heavy neutrinos cannot fit into the three-generation structure of the Standard Model.

Whether it is for the physics community of this world or for the physics community on Earth, neutrinos have a large number of mysteries that have not yet been solved.

First of all, its mass has not been directly measured, and its size is unknown; Second, it is not known whether the neutrino and its antiparticle are the same kind of particle; Third, there are two parameters of neutrino oscillations that have not been measured, and these two parameters are likely related to the mystery of the absence of antimatter in the universe. Fourth, it has no magnetic moment; Wait a minute.

Therefore, neutrinos have become an interdisciplinary and hot topic of particle physics, astrophysics, cosmology, and geophysics.

At present, in this world, neutrinos have two main applications.

One of them is neutrino communication.

Since the earth is spherical, and the surface buildings and terrain are occluded, electromagnetic wavelength transmission over long distances must be transmitted through communication satellites and ground stations.

Neutrinos, on the other hand, can penetrate the Earth directly, and they lose very little when they pass through the Earth, and neutrinos that produce 1 billion electron volts with a high-energy accelerator only decay by one thousandth of a thousandth when they pass through the Earth, so they can be transmitted directly to China from South America using neutrino beams across the Earth.

By modulating the neutrino beam, it is possible to contain useful information and communicate at any two points on Earth, without the need for expensive and complex satellites or microwave stations.

The second application is neutrino earth tomography, i.e., stratigraphic CT.

The cross-section of the interaction between neutrinos and matter increases with the increase of neutrino energy, and the neutrino beam with an energy of more than one trillion electron volts generated by a high-energy accelerator is used to irradiate the stratum directionally, and the action with the stratum matter can produce local small "earthquakes", similar to seismic exploration, which can also explore the deep strata and scan the strata layer by layer.

However, the accuracy of this kind of earth tomography is quite limited, with an error of tens of kilometers, and under such conditions, trying to locate the location of Sunset 6 in the core through stratigraphic CT is tantamount to looking for a needle in a haystack.

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