Chapter 268: Junior Brother Xu, can’t you understand?
At Geneva Airport, Xu Qingzhou had a half-hour phone call with School Beauty Song. After hearing her yawn, he hung up the phone and continued to look down at the information.
At 8 o'clock in the evening, he waited for Academician Yang Bing and Senior Brother Zhang Changqing.
"Academician Yang, Senior Brother Zhang." Xu Qingzhou put the manuscript paper into his computer bag and stood up to say hello.
"Xiao Xu, have you been waiting for a long time?" Academician Yang said with a smile.
"No." Xu Qingzhou shook his head.
Seeing that Xu Qingzhou was still reading the information just now, Academician Yang said with appreciation: "No wonder you can achieve such achievements. You use other people's time to have fun to do things, and you are rewarded for your hard work."
< br>Xu Qingzhou smiled helplessly: "Just looking at it, in front of seniors like Academician Yang, how can you boast of your hard work."
Academician Yang praised Xu Qingzhou even more in his heart. It can be seen that this young man I mean it sincerely when I say this. I am humble, studious, calm and hard-working. I am indeed the material for scientific research.
Zhang Changqing received a call at the side. After hanging up the phone, he said: "Professor, the car is here."
"Okay, let's go first." Academician Yang nodded.
"Let's go, junior brother."
"Okay."
Xu Qingzhou followed Academician Yang and the others out of the airport, got into a black Audi, and drove to the LHC on the outskirts of Geneva. Headquarters, European Organization for Nuclear Research (CERN).
"Junior brother, is this your first time in Switzerland?" Zhang Changqing asked with a smile.
"Yes, this is my first time here." Xu Qingzhou looked out the window. This was indeed his first time in this life.
Zhang Changqing said enthusiastically: "When we have time, let's go shopping together. This season, the scenery in Switzerland is just right."
"You, learn more from Xiao Xu, Don't think about going out all day." Before Xu Qingzhou could speak, Academician Yang had already said it.
"I'm just talking." Zhang Changqing smiled sarcastically.
Looking at his Guan disciple, Academician Yang shook his head helplessly and said, "If you are free, tell Xiao Xu about this experiment."
"That's no problem."
Zhang Changqing, like Gong Yunfei, is a talker. "In addition to professors from Peking University, the members of the CMS Xia Guo Group also have experts from the Institute of High Energy Physics of the Academy of Sciences. Plus you, there are 8 people. "
"The main goal of the first stage is to analyze the two-photon channel to find the Higgs particle. The yield of Higgs to two-photon is very low, and the background rate is very low. The productivity is 12 orders of magnitude higher."
Xu Qingzhou nodded slightly, he already knew these basic knowledge.
Background refers to the contribution of all other physical processes that have nothing to do with the Higgs signal during the detection process from the Higgs particle to the two-photon decay channel. Simply put, it is irrelevant debris. .
For example, the strong interaction between quarks and gluons can produce two high-energy photons, which may be mistaken for the products of Higgs decay.
Seeing Xu Qingzhou's calm expression, Zhang Changqing felt that his description was not profound enough. He thought about it and said, "This is like finding a golden sand in a lot of sand. It is very difficult."
< br>Seeing that Xu Qingzhou still nodded without a surprised expression, Zhang Changqing was helpless and said in his heart: "I'll go, does Junior Brother Xu have such a strong mentality? Or, do you have to wait until you are actually exposed to the experiment to fully understand it?"
< br>“For this experiment, in addition to the most basic CMS experiment, we also need the assistance of the ATLAS experiment, so the first stop is the Geneva headquarters, mainly to discuss the experimental plan with the ATLAS experimental team.”
ATLAS, the Torus Instrument Experiment, is one of the two large-scale experiments of the LHC.
Another large-scale experiment is the upcoming CMS experiment, which uses the LHC to generate high-energy proton beams and accelerates them to close to the speed of light, and then uses the detector CMS to record particle events generated by the collision of the proton beams.
Xu Qingzhou nodded again, the CMS detector is located in Segy, France.
Zhang Changqing is still talking: "In terms of the analysis plan for the two-photon channel, in addition to the Xia Guo group, the American group is also doing this."
"The distance is determined for the first time Two years have passed since the Higgs particle, but the number of real experiments can be counted on one's fingers, after all."
Speaking of this, Zhang Changqing shrugged and continued: "The LHC often breaks down, so that it requires long-term maintenance. It was only restarted in March this year.”
"This means that many things are still in the theoretical stage. Moreover, there is no guarantee that every theory is correct, experimental opportunities are limited, and the cost of trial and error is high."
"So, the analysis plan of the two-photon channel Our Xia Guo group and the American group will each submit one plan. After the meeting, only one plan will be approved. This also means that whoever has the best plan can take the lead in the analysis of the two-photon channel. "< br>
Xu Qingzhou was not surprised. Although most of the LHC experiments were completed under the mode of international cooperation, what they have been promoting is to bring together scientists from research institutions around the world to witness the exciting moment.
But as long as it involves matters between countries, it is never simple.
Let’s not talk about the skew in the number of places. The number of places in the Xia Kingdom is pitifully small. Even if they do join the experiment, everyone is from different countries and will compete overtly and covertly in the hope of having more in the experiment. right to speak.
Zhang Changqing took a breath and said helplessly: "We are under great pressure this time. Compared with the United States, Xia Guo is indeed at a disadvantage in high-energy physics."
Hearing this, Academician Yang put down the information and smiled. He said: "We don't need to be pessimistic. Xia Guo's research in this area has made a lot of gratifying progress in recent years, and it is even leading in some fields."
"The teacher is right, hehe. Our Xia Kingdom is no longer weak," Zhang Changqing said.
Xu Qingzhou agrees very much that modern physical theories basically come from the West. It is remarkable that Xia Guo can catch up and achieve the current development.
What's more, in the next few decades, Xia Guo will already be able to dominate.
Half an hour later, the three people got off the bus in front of the hotel.
Two figures are already waiting at the door. The one on the left is a middle-aged Xia Guo, and the one on the right is an old European man.
"Team Leader Yang." The middle-aged man shouted.
Academician Yang nodded, then turned to look at the old European man next to him: "Mr. Collins, we meet again."
"I heard that you were coming, and I even recommended the cocktail party tonight. ”
"Then I'll buy you a drink."
"Thank you. To be honest, in my opinion, meeting old friends is much more interesting than going to a cocktail party."
The two smiled and shook hands.
Through the introduction, Xu Qingzhou learned that this old man’s name was Francesca Collins, the head of the CMS Laboratory and a world-class particle physicist.
The middle-aged man is Shen Yuanjie, the deputy leader of the Xia Guo Group.
"This is Mr. Xu."
Xu Qingzhou smiled and stretched out his hand: "Nice to meet you, Professor Collins."
"Mr. Xu, welcome to the LHC."
"Thank you."
The group of people laughed and entered the hotel together to check in. Professor Collins had something to do and had to leave first.
Before leaving, Professor Collins reminded: "Yang, the American team is very strong, you have to hurry up."
"We will not be worse than them." Academician Yang smiled.
Professor Collins smiled faintly, nodded with Xu Qingzhou and the others, and turned around to leave. After a day of flying, everyone was very tired. We agreed to have a meeting at 8 o'clock tomorrow and go back to our rooms.
When he arrived at his residence, Xu Qingzhou took a photo, reported his itinerary, and told Song Yao that he had arrived.
After doing this, he went to take a bath to refresh himself.
According to Xia Guo's schedule, it is now time to sleep. Although he slept for three or four hours during the day, his biological clock has been fixed, so he is very sleepy now.
After taking a shower, before 11 o'clock, Xu Qingzhou took out the manuscript paper that he had not finished calculating on the plane during the day and continued to calculate.
At the same time, in the room on the 8th floor.
The middle-aged man put down his mobile phone and reported to the old man drinking next to him: "Professor Baker, everyone from Xia Kingdom has arrived."
Abby Baker, head of the U.S. group.
Abby Baker picked up the information on the side, which showed the participants in the CMS experiment of the Xia Guo Group.
There are 8 people in total.
5 physicists, 2 mathematics experts.
“Yang Bing, he and I are also old friends.”
Abby Baker said to herself, her eyes fell on the last person, and she smiled, "Xu Qingzhou is a genius in mathematics. Unfortunately, this is physics, not mathematics."
He was actually quite surprised, old-fashioned When did the stubborn Xia people become so adventurous that they actually gave their place to a young man.
"This young man is also very knowledgeable in quantum physics. I have read one of his articles and it is very good."
The middle-aged man smiled and said: "You know , Xia Guo has too few talents in this field, and this young man is worthy of training."
Abby Baker was noncommittal, looking into the distance through the window, and said slowly: "I am an economist. My friend said that there will be a 'war' between Xia and the United States in the future, but I disagree. ”
"Because, I feel that war has always been there."
At 12 o'clock local time, Xu Qingzhou closed the computer and went to bed. Perhaps because he was too tired, he fell into a deep sleep as soon as he touched the bed and stayed there until the next day. I woke up at 7 o'clock in the morning.
On the first day of their foreign relationship, school beauty Song sent a photo of herself and Ermiao, said good morning to Xu Qingzhou, and said that she was going to the countryside to visit her grandparents.
After chatting with Song Yao, Xu Qingzhou got up, washed up, went to the restaurant to have breakfast, and arrived at the conference room at 7:30.
There are only two people in the conference room.
A middle-aged man with a clear face, wearing glasses, is looking down at the information, and the other is of a similar age.
"Professor Mao, Professor Wang."
Xu Qingzhou greeted, both of them are experts in particle physics.
"Xiao Xu, sit down." Mao Yi raised his head.
Wang Qiming glanced at Xu Qingzhou lightly and nodded slightly. He was not enthusiastic at all, but even a little hostile.
"Did you sleep well last night?" Mao Yi asked with a smile.
"Not bad." Xu Qingzhou nodded.
Mao Yi smiled and joked: "Young people are in good health. Unlike me, I couldn't sleep on the first day here."
"You are still young too."
At almost 8 o'clock, Academician Yang and Senior Brother Zhang also arrived.
The members of Xia Guo's group gradually arrived, 8 of them, the slightly younger ones were Xu Qingzhou and a girl who looked to be in her twenties or seventies.
Without unnecessary pleasantries, Academician Yang looked around and said: "This is the second time our group has participated in the CMS experiment. I am too lazy to say small things. We are pressed for time and will go directly to the topic."
"Task: Analysis of the two-photon channel."
"Analysis of the two-photon channel of the Higgs particle is a complex and delicate process"
Xu Qingzhou quietly Listen, I have actually understood what Academician Yang said for a long time.
The experiment is mainly to find the Higgs particle from the two decay channels of diphoton and 4-lepton. After that, the particle's decay mode, signal strength, and interaction strength with other particles are studied.
The current first step is the analysis of the two decay channels of diphotons and 4-lepton.
In terms of two-photons, Xia Guo and the United States are responsible. As for 4-lepton, Germany and India are responsible, and the remaining member states can play their role in the follow-up.
“We all know that the yield of Higgs to two-photon is very low, so the problem before us arises – how to effectively eliminate the background.”
“ The first one uses data-driven methods to estimate background levels, such as sideband data methods or control sample methods. These methods use the experimental data itself to build the background model, thereby reducing the reliance on external simulations. ”
< br>
Xu Qingzhou tapped his fingertips and thought about the solution in his mind.
A common approach is to reduce the contribution of background events by optimizing photon screening conditions, such as energy thresholds, angle restrictions, isolation requirements, etc.
Or use multi-variable analysis technology to build a discriminator that can evaluate the possibility of an event being a signal or background based on the energy, momentum, angular distribution, etc. of multiple input variable photons.< br>
Zhang Changqing couldn't help but look at Xu Qingzhou, Junior Brother Xu was in a daze. Did he not understand?
But it’s normal when you think about it. The teacher’s pace is too fast. It’s the first time for Junior Brother Xu to be with the experimental group, so it’s normal for him to be unable to keep up.
Seeing that Xu Qingzhou was lost in thought, Wang Qiming raised his head and his eyes showed more dissatisfaction.
Xu Qingzhou noticed something strange and raised his head. When he saw Wang Qiming looking at him lightly, he couldn't help but have a strange expression on his face. Does this person have a grudge against him?
After one hour passed, Academician Yang waved his hand, indicating that it was time for an intermission.
Xu Qingzhou was thinking about how to solve the underlying problem, when he was dragged to the toilet by Senior Brother Zhang.
After going to the toilet, Zhang Changqing took him to the balcony to breathe fresh air, and at the same time asked: "Junior brother, how do you feel?"
"It's okay."
Xu Qingzhou nodded.
Quantum mechanics describes the behavior and interaction of microscopic particles. The existence and characteristics of the Higgs particle were predicted and understood on the basis of quantum mechanics. Its existence and properties also follow the quantum field. The laws of theory.
For him, the Higgs particle stuff is not difficult to understand.
On the balcony, Zhang Changqing raised his head and looked around. Seeing no one else, he asked Xu Qingzhou in a low voice: "Did Professor Wang Qiming embarrass you?"
"It seems that I really don't like it." Xu Qingzhou said.
“Actually, there were only 6 places in the experimental team originally, but because the LHC maintenance took too long, not many results were produced, but the membership fee was not reduced at all. So, every experiment is given more "There are two places available."
"One of the many places this time is Xiao Chen from the Academy of Sciences, and the other one is you."
Zhang Changqing spread his hands: "Professor Wang Qiming originally wanted to. I asked my Ph.D. student to come, and the result..."
Xu Qingzhou suddenly realized that no wonder he was unhappy.
(End of this chapter)