Chapter 268 Junior Brother Xu doesn’t understand? At the Geneva Airport, Xu Qingzhou and School Beauty Song had a half-hour phone call. After hearing her yawn, he hung up the phone and continued to look down at the documents. 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, stood up and greeted them. "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, Academician Yang said with appreciation: "No wonder you can achieve such success. You use the time that others spend having fun to do things. Hard work pays off." Xu Qingzhou smiled helplessly: "I was just taking a look. How dare I boast of my hard work in front of seniors like Academician Yang?" Academician Yang praised Xu Qingzhou even more in his heart. He could see that this young man was sincere when he said this. He was humble, studious, calm and hardworking. He was indeed a good candidate for scientific research. Zhang Changqing received a call nearby. After hanging up, he said, "Professor, the car is here."
"Okay, let's go first." Academician Yang nodded. "Let's go, junior brother." "it is good." Xu Qingzhou followed Academician Yang and his colleagues out of the airport, got into a black Audi, and drove to the LHC headquarters, the European Organization for Nuclear Research (CERN), in the suburbs of Geneva. "Junior brother, is this your first time in Switzerland?" Zhang Changqing asked with a smile. "Yes, it's my first time here." Xu Qingzhou looked out the window. This was indeed the first time he came here in his life. Zhang Changqing said enthusiastically: "Then when we have time, let's go for a walk together. The scenery in Switzerland is just right at this season." "You should learn more from Xiao Xu and stop thinking about going out to play all day." Academician Yang said before Xu Qingzhou could say anything. "I was just talking." Zhang Changqing smiled awkwardly. Looking at his last disciple, Academician Yang shook his head helplessly and said, "If you have time, tell Xiao Xu about this experiment." "That's no problem." Zhang Changqing, like Gong Yunfei, is a chatterbox. "The members of the CMS Xia Guo group include professors from Peking University and experts from the Institute of High Energy Physics of the Academy of Sciences. Including you, there are a total of 8 people." "The main goal of the first phase is to analyze the two-photon channel to find the Higgs boson. The yield of the Higgs to two-photons is very low, while the background yield is 12 orders of magnitude higher." Xu Qingzhou nodded slightly. He already knew all this basic knowledge. Background refers to the contribution of all other physical processes unrelated to the Higgs signal during the detection of the Higgs particle to 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. After thinking for a while, he said, "It's like finding a grain of gold in a pile of sand. It's very difficult." Seeing that Xu Qingzhou still nodded without any surprise, Zhang Changqing was helpless and thought to himself, "Oh my god, is Junior Brother Xu's mentality so strong? Or...I need to wait until I actually get involved in the experiment to deeply understand it?" "In addition to the most basic CMS experiment, our experiment also requires the assistance of the ATLAS experiment, so our first stop is the Geneva headquarters, mainly to discuss the experimental plan with the ATLAS experimental team."
ATLAS, or the Hyper-Toroidal Instrument Experiment, is one of two large-scale experiments at the LHC. Another large-scale experiment is the upcoming CMS experiment, which uses the LHC to generate a high-energy proton beam and accelerate it to nearly the speed of light, and then uses the detector CMS to record particle events produced by proton beam collisions. Xu Qingzhou nodded again. The CMS detector is located in Cechy, France. Zhang Changqing continued, "In terms of the analysis of the two-photon path, in addition to the Xia group, the American group is also working on this." "It has been two years since the Higgs particle was first confirmed, but the number of real experiments has been very small, after all." At this point, Zhang Changqing shrugged and continued: "The LHC often malfunctioned, requiring a long period of maintenance, and 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 for the two-photon channel will be submitted by our Xiaguo group and the American group respectively. After five days of review, only one plan will be approved. This also means that whoever has the best plan can lead the analysis of the two-photon channel experiment." Xu Qingzhou was not surprised. Although most of the LHC experiments are completed under the mode of international cooperation, it has always been promoted to bring together scientists from research institutions around the world to witness the exciting moment together. But as long as it involves matters between countries, nothing is simple. Not to mention the bias in quotas, Xia Country has very few places. Even if it really joins the experiment, everyone comes from different countries and will compete openly or secretly in the hope of having more say in the experiment. Zhang Changqing exhaled and said helplessly: "We are under great pressure this time. Compared with the United States, Xiaguo is indeed at a disadvantage in high-energy physics." Hearing this, Academician Yang put down the materials and said with a smile: "We don't need to be pessimistic. In recent years, Xiaguo has made many gratifying progress in this area of research, and is even in the leading position in some areas." "Teacher is right. Hehe, our Xia country is not weak now." Zhang Changqing said. Xu Qingzhou agreed that modern physics theories basically originated from the West. It was already remarkable that Xiaguo was able to catch up and achieve its current development. What's more, in the next few decades, Xia Kingdom will be able to take the lead. Half an hour later, three people got off the car in front of the hotel. Two figures were already waiting at the door, a middle-aged man with a Xia Guo face on the left, and an old European man on the right. "Team Leader Yang." the middle-aged man shouted. Academician Yang nodded, then turned to look at the European old man next to him: "Mr. Collins, we meet again." "I heard you were coming over, so I even canceled my cocktail party tonight." "Then I'll buy you a drink." "Thank you. To be honest, I think meeting old friends is much more interesting than going to a cocktail party." The two men smiled and shook hands. Through the introduction, Xu Qingzhou learned that the old man was called Francesca Collins, the head of the CMS laboratory and a world-class particle physicist. The middle-aged man is called Shen Yuanjie, the deputy leader of the Xiaguo Group. "This must be Mr. Xu." Xu Qingzhou smiled and extended his hand: "It's great to meet you, Professor Collins."
"Mr. Xu, welcome to the LHC." "Thank you." The group chatted and laughed as they entered the hotel and checked in. Professor Collins had something else to do, so he had to leave first. Before leaving, Professor Collins reminded: "Yang, the American team is very strong, you have to hurry up." "We are no worse than them." Academician Yang smiled. Professor Collins smiled faintly, nodded to Xu Qingzhou and the others, and turned away. After a day of flying, everyone was very tired. They agreed to have a meeting at 8 o'clock tomorrow and went back to their rooms. After arriving at his residence, Xu Qingzhou took a photo, reported his itinerary, and told Song Yao that he had arrived. After doing all this, he went to take a bath to refresh himself. According to Xia Guo's schedule, now is the time to go to bed. 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 phone and reported to the old man drinking next to him: "Professor Baker, everyone from Xia Country has arrived." Abby Baker, head of the US team. Abby Baker picked up a document beside her, which listed the participants of Xia Guo's CMS experiment. There were 8 people in total. 5 physicists and 2 mathematicians. "Yang Bing, he and I are old friends too." Abby Baker muttered 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. When did the old-fashioned and stubborn Xia people become so adventurous that they actually gave the quota to a young man. "This young man is also very insightful in quantum physics. I have read one of his articles, and it is very well written." The middle-aged man smiled and said, "You know, Xiaguo has too few reserve talents in this field. This young man is worth training." Abby Baker did not comment, looking out the window into the distance, and said slowly: "An economist friend of mine said that there will be a 'war' between Xiaguo and the United States in the future. I disagree." "Because, I feel like the war is always there." At 12 noon local time, Xu Qingzhou closed his 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 did not wake up until 7 o'clock the next morning. On the first day of the long-distance relationship, School Beauty Song posted a photo of herself and Er Miao, 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 meeting room at 7:. There are only two people in the conference room. A middle-aged man with a handsome face, wearing glasses, was looking down at some information, and the other one was of similar age.
"Professor Mao, Professor Wang." Xu Qingzhou greeted them. Both of them were experts in particle physics. "Xiao Xu, sit down." Mao Yi looked up. Wang Qiming glanced at Xu Qingzhou indifferently and nodded slightly. He was not enthusiastic at all, and 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, who couldn't sleep on the first day I came." "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. There were 8 people. The younger ones were Xu Qingzhou and a girl who looked to be around or years old. Without any extra greetings, 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 any greetings. We are short of time, so let's get straight to the point." "Task: Analysis of the two-photon tract." "Analysis of the two-photon path of the Higgs particle is a complex and delicate process" Xu Qingzhou listened quietly. In fact, he already understood what Academician Yang said. The experiment mainly aims to find the Higgs boson from the two decay channels of diphoton and quadruple-lepton. After that, the decay mode of the particle, signal strength, and interaction strength with other particles will be studied. The first step at present is to analyze the two decay channels of diphoton and four-lepton. For two-photons, Xia and the United States are responsible, for four-leptons, Germany and India are responsible, and the rest of the member countries will play a role later. "We all know that the yield of Higgs to diphotons is very low, so the question before us is how to effectively eliminate the background." "The first one uses a data-driven approach to estimate background levels, either the sideband data approach or the control sample approach. These approaches use the experimental data themselves to build the background model, thus reducing the reliance on external simulations." Xu Qingzhou tapped his fingertips and thought of a solution in his mind. A common approach is to reduce the contribution of background events by optimizing photon screening conditions, such as energy threshold, angle restriction, isolation requirements, etc. Alternatively, a discriminator can be constructed using multivariate analysis techniques, which can assess the likelihood of an event being a signal or background based on multiple input variables such as the energy, momentum, and angular distribution of photons. Zhang Changqing couldn't help but look at Xu Qingzhou. Junior Brother Xu, is he in a daze? Doesn't he understand? But it's normal when you think about it. The teacher's pace is too fast. It's Junior Brother Xu's first time with the experimental group, so it's normal that he can't keep up. Seeing Xu Qingzhou in a daze, Wang Qiming looked up with even more resentment in his eyes. Xu Qingzhou noticed something strange, looked up, and saw Wang Qiming giving him a faint glance. He couldn't help but have a strange expression on his face. Does this guy have a grudge against him? After an hour, Academician Yang waved his hand, indicating that it was time for a break. Xu Qingzhou was originally thinking about how to solve the background 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 get some fresh air and asked, "Junior brother, how do you feel?" "good." Xu Qingzhou nodded.
Quantum mechanics describes the behavior and interactions of microscopic particles. The existence and characteristics of the Higgs boson are predicted and understood on the basis of quantum mechanics. Its existence and properties also follow the laws of quantum field theory. For him, the Higgs stuff wasn't hard to understand. On the balcony, Zhang Changqing looked up and around. Seeing that there was no one else, he asked Xu Qingzhou in a low voice: "Did Professor Wang Qiming give you the cold shoulder?" "It seems like he really doesn't like me." Xu Qingzhou said. "In fact, the experimental team originally had only six places, but because the LHC was under maintenance for too long, not many results were produced, but the membership fee was collected without any reduction. Therefore, two more places were given for each experiment." "Among the many candidates this time, one is Xiao Chen from the Academy of Sciences, and the other is you." Zhang Changqing spread his hands and said, "Professor Wang Qiming originally wanted to let his doctoral students come, but..." Xu Qingzhou suddenly realized, no wonder he was unhappy with him. (End of this chapter)