Chapter 411 The most important achievement of high-energy physics after the founding of the People's Republic of China was born! (Part 1)
After introducing the B1 Experimental Hall to everyone.
Ji Xiangdong took everyone to visit B2, C1 and other special experimental locations.
After all, a lot of equipment still needs to be debugged, and the re-inspection process cannot be started immediately.
Secondly, some experimental areas of Jinping Laboratory are indeed quite special, and many of them are specialized equipment in the direction of dark matter.
Even if 90% of the people present are academicians, they actually don’t have many opportunities to come into contact with these things on weekdays - the same principle applies in reverse.
For example, Academician Pan and the others often use the Bell state integrated observation ring. Ji Xiangdong guesses that he can't even figure out how to explain the number.
Of course.
Wang Lao and other elderly meritorious deeds did not accompany him, but were placed in the lounge to take a nap.
that's all.
About an hour later.
Ji Xiangdong took a group of old academicians back to the equipment room behind the B1 laboratory hall.
This equipment room belongs to the research module of the B1 laboratory. It has many electronic devices and is mainly responsible for inputting various password schemes.
The equipment room covers an area of about three hundred square meters and looks very spacious. There is a huge LED screen placed on the middle wall.
Below the screen is a main console, which is almost 2X8 in size.
Generally speaking.
There should be some computers and other equipment placed under the stage in this arrangement, just like the command room for satellite launches that you usually see.
However, considering that there were many big bosses present today and they were older, the laboratory removed those tables.
Instead.
Then there are some ergonomic chairs or even recliners.
At the same time, each chair is also equipped with blankets, tea, and some snacks or grain porridge that are not very sugary.
Other than that.
Outside the laboratory, there is also a team of experts supported by Chengdu, all senior bosses from the Health Bureau, waiting on standby.
There are even helicopters outside, ready to take off at any time.
After all, these are a total of twenty-seven Chinese academicians, including a national treasure like Mr. Wang, so you can't be too careful.
soon.
Most of the academicians sat down and drank tea leisurely.
Several other liquid scintillation experts came to the console and listened to the experimental plan nearby.
After all, like Hou Xingyuan, they only received the notification of the discovery of dark matter from the University of Science and Technology yesterday, and immediately took a plane to Chengdu.
That is to say, they only know this thing, but they don't understand the specific discovery process.
Only someone with top-notch merit like Mr. Wang could grasp all the details of the whole matter before arriving in Chengdu.
“The whole thing can be traced back to October last year.”
Since there were many big guys present at the scene, Academician Pan took the role of commentator and pointed at Zhao Zhengguo beside him:
"At that time, Academician Zhao conducted an experiment on the decay parameters of Λ hyperon, and the polarization reached 27%, which was the first breakthrough in the world. The code name was 4685."
Zhao Zhengguo nodded after hearing this and added:
"Well, that was the second time I led a team to conduct a decay experiment. I didn't expect any good results at first, but I didn't expect that I actually made a breakthrough. I am ashamed and ashamed."
Hear this.
An old academician from the China Institute of High Energy Physics thought for a moment and nodded slightly:
"I have an impression of this. Xiao Zhao sent the newsletter to me that day. If I remember correctly, it rained very pleasantly that day."
Zhao Zhengguo recalled it for two seconds and then nodded:
"Oh, yes, it rained so much that the seat cushion of my e-mule was all wet, so I borrowed a towel from the security office before I could get home smoothly."
There was a burst of good-natured laughter all around.
Then Academician Pan paused, patted Xu Yun next to him on the shoulder, and pushed him forward:
"Then I, the student, calculated the probability orbit. After the experiment, we discovered the companion particle of the 4685Λ hyperon and gave it the name of a lone point particle."
"Then later comes the ground state processing, and."
After Academician Pan introduced the whole matter eloquently, many academicians suddenly looked at Xu Yun differently.
These old academicians are generally quite young. They started in their sixties or seventies, and there are several in their late teens.
Their interaction with the Internet is basically querying or publishing papers in journals, or at most remote meetings.
Therefore, not many people know about imidacloprid or the previous price war smear incident.
So from the beginning.
They thought that Xu Yun was just a junior brought by Academician Pan, mainly to support him and make him look familiar in front of many big bosses.
The result was unexpected.
Xu Yun made a surprising contribution to the whole thing?
Particle orbit was explained earlier. Although it is called an 'orbit', it is actually a probabilistic model.
This kind of probability model cannot be guessed by just guessing. It must have strong computing power and observation ability.
For example, the reason why Mr. Ding Zhaozhong was able to discover gluons was because he performed reduction calculations on the color flavor of bottom quarks on the spray column.
His calculations lasted for eight hours before finally locking in the then-undiscovered elementary particle.
Therefore, not just anyone can handle this particle trajectory - not to mention that Xu Yun is still so young.
Several academicians who were still leading projects couldn't help but think of the students in their research groups.
Although everyone who can enter the door of these big guys is a genius, they obviously cannot do this.
Academician Pan has accepted a good student
Of course.
This emotion is almost fleeting and lasts only a short time.
After all, these academicians who can be present have the most contact with geniuses in their lives. In their eyes, geniuses can be described as crucian carp across the river.
At this time, Xu Yun could only make their eyes shine, and that was all.
Compared with Cao Yuan and others, Xu Yun still lags behind - at least on the surface.
So it's quick.
Everyone still focused on preparations for the verification process.
Gululu——
With Ji Xiangdong's operation.
In the hemispherical detector that looks like an upside-down bowl on the ground floor of the B1 experimental hall next door, water-based liquid scintillator began to be filled through the pipes.
This is in preparation for the subsequent pure xenon.
Students who were exposed to dark matter in their previous lives should know this.
Although dark matter does not have standard weak interactions, there is a special case that is not included.
That's a xenon atom.
Xenon is an inert gas, and its well-known application is probably in the semiconductor field.
But actually.
Liquid xenon, which is liquefied xenon gas, is actually an extreme substance that weakly interacts with dark matter.
Liquid xenon has a very high density, about three kilograms per liter, which is denser than aluminum.
When dark matter interacts weakly with xenon nuclei.
The xenon nucleus will undergo nuclear recoil, and the momentum of the dark matter will be transferred to the xenon atom.
The xenon atoms will thus reach an excited state, forming a dimer, and a small number of electrons will be ionized.
These electrons drift to the gas-liquid surface under the action of an electric field, eventually forming electroluminescence.
There are two main reasons why this reaction is not considered an ordinary weak interaction.
First, the hit rate of dark matter is 1/100000000000000000000 - this is not a casual value, but a real probability.
Second, it is very difficult to produce pure xenon.
Currently, 100 countries can produce pure xenon with a purity of more than 99.00%, but which country can produce 99.98%?
There are only five:
Neon, across the sea, stuffed bears, rabbits and Sweden.
Well, Sweden.
so what.
Basically, the current weak interaction framework will not discuss the case of pure xenon - because the dark matter property framework we are talking about is a category of life, and the accuracy is different.
Because it takes a long, long time to pour 4,000 tons of water-based liquid scintillator.
Therefore, taking advantage of the opportunity, Ji Xiangdong introduced the specific experimental plan to everyone - so many big guys came to Jinping not only to watch the show, but also to audit the errors of the experiment.
"Fellow academicians, our preparations are as follows."
Next to the operating table.
Ji Xiangdong held a writing board and quickly drew a schematic diagram on it:
"Under normal circumstances, atoms will produce photons when they are de-excited, so just put a photon detector at the bottom of the device to receive the direct flash signal."
Ji Xiangdong said and drew a circle on [Direct Flash Signal].
At the same time, there is a letter marked on the side:
L1.
Then he paused and continued:
"But considering the interaction between dark matter and liquid xenon, transferring energy is a very complicated process and cannot be so smooth."
"So we set up another electric field between the gas-liquid surface and the photoelectric effect tube on top of the detector."
"The intensity of this electric field is 10,000V/cm. Under this strong electric field, electrons are accelerated to bombard xenon atoms, which allows the electroluminescence phenomenon to be accepted by the photoelectric effect tube on the top."
"The signal received by the top photoelectric effect tube is called L2."
"With these two sets of signals, the final result can basically be determined."
Ji Xiangdong’s introduction was in human terms. It’s wrong. To put it in a layman’s terms, it’s
Put a basin of water, and then put the isolated particles in it. If it shines, it is dark matter.
Of course.
This is just a metaphor, it's actually much more complicated than this.
After Ji Xiangdong's introduction is completed.
The old academician from the China Institute of High Energy Physics who had reviewed Zhao Zhengguo’s correspondence thought about it and raised a question:
"Xiao Ji, the plan is feasible, but how to eliminate the impact of radioactive background?"
"Although the environment of Jinping Laboratory is very 'clean', there will still be some ordinary radiation that produces electromagnetic interactions and thus emits radiation signals."
"Whether it is a dark matter signal or a radiation signal, the carrier is photon, and the observation equipment does not care about their source."
"It would be okay if we were studying other substances, but the special characteristics of dark matter are there, so this kind of error must be avoided."
I heard what the old academician said.
The rest of the people also nodded in approval.
The full name of the old academician is Zhou Shaoping. He is almost 85 years old this year. He is a well-deserved pioneer of high-energy physics in China.
What he said about the radioactive background was not a nitpick, but an issue that must be taken into account.
After all, their verification data today may be related to one of the most important results in the high-energy field since the founding of the People's Republic of China, so one cannot be too cautious.
Ji Xiangdong had obviously thought of this a long time ago, and calmly continued to explain on the writing board:
"Mr. Zhou, we have also considered the situation you mentioned, and the laboratory has prepared a set of response plans in advance."
"As you said, ordinary radiation has electromagnetic interaction, so it reacts more with the extranuclear electrons of xenon atoms and less with the nucleus of xenon atoms."
"So they mainly cause electrons to recoil from the xenon atoms, so for a certain period of time, the L1 signal will have fewer counts."
"We are going to start from here and use the ΛCDM algorithm to compare the staged differences between L1 and L2 to distinguish the dark matter signal from the ordinary radiation signal, thereby reducing the impact of the radioactive background."
"ΛCDM algorithm?"
Zhou Shaoping repeated the word and frowned slightly.
The so-called ΛCDM.
Its pronunciation is actually Λ-CDM, which is a model of quantum field theory.
Λ in ΛCDM represents dark energy, and CDM represents cold dark matter.
Quantum field theory was developed in the 1960s and 1970s, and explained in a very concise form the elementary particles that had been discovered at that time.
As of the discovery of the Higgs boson in 2012, all particles predicted by the Standard Model have been discovered, and some predictions of quantum field theory deviate from experimental results by less than one billionth.
However, as a dark matter scenario model extended from quantum field theory, ΛCDM is relatively far-reaching.
As of now.
The error between it and the description of the existing universe model is about three percent.
In the micro field, this is actually a big difference.
no way.
The scientific community’s understanding of dark matter is too shallow.
More importantly.
It was said above.
In the liquid xenon scenario, the hit rate for dark matter is 1/100000000000000000000.
The model itself has errors, and the hit rate is uncertain.
Therefore, Ji Xiangdong's so-called "stage difference" is basically a false proposition.
Give an example.
If the model is correct and the hit rate is high, then there should be a result like this:
The report is divided into 20 intervals, and every 4 intervals has a peak - that is, a collision has occurred.
The period is fixed, and then all you have to do is compare the differences in the wave peaks.
However, due to the incorrect model, the actual results may be as follows:
There are still 20 intervals, the 1-4 interval is smooth, the 5 interval has a bulge, then 6-14 are all smoothed, and 15 and 17 have bulges.
Without periodic peaks and troughs, it is almost impossible to eliminate the influence of radioactive background.
So although this solution is feasible, it is definitely not very accurate - at least it is not worthy of the accuracy that the concept of dark matter should have.
The gathering of these big guys here today clearly shows the attitude of the superiors:
Dark matter must be retested as soon as possible and then announced.
Zhou Shaoping didn't understand the reason behind it. Maybe it was Hou Xingyuan's temporary intention after he learned from Academician Pan that they wanted to come to Jinping, or maybe it was some other idea from a higher level.
In short, this is the reality.
Therefore, there is no possibility for them to use ordinary means to verify one round first, and then conduct a more precise retest a few months later - what they are conducting now is the final exam.
Otherwise, if you want to complete the ordinary re-inspection, there is no need to go to such trouble.
Think of this.
Zhou Shaoping couldn't help but look at Ji Xiangdong and asked him:
"Xiao Ji, can this part of the plan be optimized a little more?"
Ji Xiangdong thought for a moment, with a trace of embarrassment on his face.
It's obvious.
Zhou Shaoping's problem obviously couldn't be solved for a while.
This is not to say that Ji Xiangdong is not capable enough, or that the Jinping Laboratory, an important tool in the country, is at this level.
It's because solitary point particles are so special.
Mentioned before.
Currently, the hottest dark matter candidates in the industry include two particles.
The first is sterile neutrinos - ordinary neutrinos are hot dark matter, so relatively 'lazy' neutrinos should theoretically meet the requirements of cold dark matter.
The second is WIMP.
WIMP perfectly fits the supersymmetric model, and the theory is quite elegant, convincing most physicists.
Right.
When I introduced WIMP before, I once said that there was an old professor at the Academy of Sciences who liked fairy novels very much, and gave WIMP the nickname "Daobiao".
This person is none other than Zhou Shaoping.
all in all.
Because this thing fits the model so well, in the past few decades, countless of the world's best experimental physicists have been searching for dark matter in this direction.
The result?
HKUST quietly discovered an isolated point particle. At the same time, due to the accompanying nature of 4685Λ hyperon, it was completely different from all previous research directions.
When this situation comes to reality, the most intuitive reaction is.
Many devices that were WIMP in advance are suddenly useless.
If you have enough time, then it's better to say that. At the worst, we can work together to debug the equipment, and maybe it can be used in a month or two.
But don't forget.
It only took more than 20 hours for Jinping Laboratory to receive the news.
At the same time, due to the special nature of dark matter, it is impossible for the Academy of Sciences and even higher authorities to give so much time to prepare - otherwise, everyone would not rush to Jinping in a hurry.
in this case.
Do you want the laboratory to come up with a complete and perfect plan without any errors?
It's better to ask them to tinker with colorful black.
Actually.
Just the plan proposed by Ji Xiangdong caused more than a hundred scientific researchers to lose most of their hair.
Zhou Shaoping and others soon realized this, and then.
The eyes of several old academicians suddenly lit up.
The more capable a person is, the more he refuses to accept old age.
As veteran scientific researchers, they have been eager to contribute something almost since they arrived at the Jinping Underground Laboratory.
It's just that this is Ji Xiangdong's home court, so it's obviously not appropriate to speak rashly.
There are flaws in the current plan. Isn't this a huge opportunity?
After all, one of the names of their trip is to serve as an external consultant for the verification plan.
In fact, Ji Xiangping's previous words may not have included the idea of asking these big guys to help.
So it's quick.
A group of gray-haired academicians gathered around the table and started discussing the experimental plan on the spot.
After the discussion begins.
Zhou Shaoping first came up with an idea:
"Everyone, we have limited time, so I will shamelessly throw some light on it - my idea is, can we start with the strong PC problem?"
"Strong PC problem?"
Hearing Zhou Shaoping's words, another old academician with a heavy Sichuan accent frowned:
"Laos Zhou, isn't that the category of the strong nuclear force?"
"That's right."
Zhou Shaoping nodded slightly, but quickly said:
"But Lao Chen, don't forget, there is a Peccei-Quinn metric in the strong PC problem, which is consistent with the dark matter model"
The old academician surnamed Chen was slightly startled, then patted his head:
"Mmp, how could I forget that thing?"
Strong PC problem.
This is a complex content of quantum chromodynamics, and there is no need to delve into the details.
all in all.
The "strong" here corresponds to the strong nuclear force, and CP refers to ChargeParity, which is charge-parity.
Students who are familiar with advanced physics should know this.
Many problems in advanced physics often have different solutions under different circumstances, and these solutions have a unified name:
Metrics.
The most famous one is Einstein's field equations.
There are currently several metrics for Einstein's field equations, such as Kerr metric, Schwarzschild metric, etc.
At the same time, these metrics also correspond to a certain model.
For example, the Kerr metric corresponds to the Kerr black hole.
The Gödel metric corresponds to the Gödel universe and so on.
By the way.
Einstein's equations also have a special space-time metric called the Alcubierre metric.
It is the "bubble curvature engine" often mentioned in science fiction movies.
The weird thing about this thing is that its concept first appeared in science fiction movies, and then Alcubierre came up with the solution in 1994.
That is to say, fantasy comes first and theory comes last.
Did science guide science fiction, or did science fiction inspire science?
alright.
The topic returns to its original place.
Just like the rules mentioned above.
The Peccei-Quinn metric is also a specific solution to the strong PC problem.
This is the Peccei-Quinn mechanism proposed by Peccei and Quinn in the 1970s. Helen Quinn is also the female physicist most promising to win the Nobel Prize in high energy physics.
It can construct a testing framework for dark matter at a certain energy level, and the supersymmetric partner also conforms to the characteristics of the 4685Λ hyperon.
At the same time, it can adjust the dispersion angle and eliminate errors through the most reliable optical path difference.
Of course.
The Peccei-Quinn metric also has some technical difficulties, and whether it is feasible requires a more detailed discussion.
What these academicians need to do now is to roughly screen out some relatively feasible plans and then screen them one by one.
So it's quick.
Many academicians continued to start a new round of brainstorming:
"In addition to the Peccei-Quinn metric, I think it is also a good idea to let charged particles pass through the TPC."
"How about using deuterium in heavy water to detect neutrinos like Kamiokande did? There should be a lot of heavy water in Xiaoji."
"How about ionization plus phonons?"
"I think the CQ mechanism we used in Gundam before is feasible."
More than an hour later.
Five candidates were put in front of everyone:
Peccei-Quinn metric.
Go up to 9 kilograms of target material.
Detecting the effects of dark matter on atomic clocks.
Further capturing secondary particles of dark matter.
and
Errors are allowed, and fitting analysis is performed through multi-discussion measured curves.
Then quickly.
The secondary particle scenario was first ruled out.
Secondary particles belong to the category of indirect detection, and its principle is very simple:
It is to allow the secondary particles of dark matter particles to interact with the detector, thereby indirectly obtaining information about dark matter particles.
Just like the mother is the dark matter particle, and the child is the secondary particle produced by the decay of the dark matter particle.
According to the first law of thimbles, it is the mother who saves the child.
Next.
Scientists used cameras to take pictures of the children and use the children's faces to infer the mother's face.
This approach is an idea in conventional research, the difficulty is relatively low, and it is also very interesting.
But in this situation, it is obviously not suitable.
Then quickly.
Options two and three were also eliminated.
These two solutions are also difficult to reduce the impact of radioactive background and have little practical effect.
Therefore, there are only two options left before everyone:
Retest using the Peccei-Quinn scale.
Or allow errors to exist and conduct fitting analysis through multiple rounds of measured curves.
Then
There were serious differences of opinion among the people.
Among these 27 academicians.
Except for Mr. Wang, Mr. Zhang and Mr. Hou Xingyuan who did not take a stand, half of the academicians supported the two plans.
"Everyone, I still stick to the Peccei-Quinn metric."
Zhou Shaoping first picked up the tea on the table and took a sip, then looked around, and then continued:
"The hit probability of 1/100000000000000000000 is really too low. I don't think a normal curve can be fitted through multiple measurements."
"Even if we do 100,000 experiments a day, the decimal point will still not advance to within ten places."
"This plan is not so much about eliminating errors as it is about hypnotizing yourself."
After Zhou Shaoping said these words, people around him reacted in different ways.
Some academicians nodded in agreement.
Some academicians were expressionless.
Some other academicians frowned and clearly disagreed.
After a while.
The only female academician present spoke:
"Lao Zhou, you are right. Everyone knows that the Peccei-Quinn metric is obviously more appropriate."
"But the question is. How do we construct a wide-area gauge field configuration?"
"There are now more than a dozen schools of thought in the axion field alone, not to mention the unfamiliar particle, the solitary point particle."
"If you can't even bring out the Void Field, no matter how applicable it is in theory, it's just a mirror image in reality."
When Zhou Shaoping heard this, he pinched the bridge of his nose a little irritably.
The situation described by the female academician was also the core of the different opinions of everyone at the scene.
Everyone knows it.
The Peccei-Quinn metric or Peccei-Quinn energy scale is obviously very helpful at present.
But the problem is
The dark matter framework it establishes is more biased towards the axion field.
Although it can control the emission angle θ of particles, it allows the upper and lower signal receivers to avoid radioactive background errors through optical path differences.
But for isolated point particles, it is very troublesome to construct a wide-area gauge field configuration.
This is not a problem that can be solved by spending more time. It involves the local u1 symmetry of the gauge field extended by Maxwell's equations.
At least during the discussion just now, no one could think of a suitable cut point - again, everyone is too unfamiliar with solitary point particles.
Looking at Zhou Shaoping, whose face was gloomy and uncertain, the female academician comforted him again:
"Old Zhou, I think you have fallen into a certain misunderstanding."
"The probability of multiple fittings is indeed not high, but the conditions of Jinping Laboratory itself are very good. The so-called influence of radioactive background is actually not large."
"If we can construct a suitable gauge field, then of course we can use this idea, but right now"
Zhou Shaoping continued to be silent.
What the female academician said made sense, and he naturally knew this.
But as a physicist from the last century, Zhou Shaoping or all rabbits have a kind of obsessive-compulsive disorder in their hearts:
To be ours, we have to be the best, so good that others can’t find fault with it.
Then he gritted his teeth, still not ready to give up:
"We can start calculations now. The equipment here in Jinping is very advanced, and we may not be able to get results in a short time!"
Hear what he said.
Another academician who had previously opposed the attitude shook his head and his tone was also very candid:
"Lao Zhou, it's okay to give you some time, but what about the idea?"
"If you want to calculate and construct a wide-area field, you must have an idea, right?"
"For example, how much does the scintillation weigh, whether it needs isotopes, the direction of the field strength, and most importantly, how it interacts with dark matter - is it collision, annihilation or sliding?"
"It's not that everyone is against you. If you can come up with a suitable idea, I will be the first to attack you!"
"."
Hear these words.
Zhou Shaoping opened his mouth, but in the end he remained silent.
After all.
Still not reconciled
Looking at the silent Zhou Shaoping.
Hou Xingyuan on the side shook his head, ready to speak and make the final decision.
If you can't do something, then you can't blame others for choosing other ways.
This is a very realistic truth.
However, just when Hou Xingyuan was about to give up.
In the area on the left side of the scene, a weak voice suddenly sounded:
"Well, Academician Zhou, as for the Peccei-Quinn metric, can we try it without using the double electron capture angle?" (End of Chapter)