The top student must be diligent

While talking, Xiao Yi also came to the blackboard next to him and wrote on it: [W±→±+ν].

"The data I chose is a combination of W boson decay into high-energy electrons and neutrinos, where the electrons are detected by the electromagnetic calorimeter in the detector, and the electron energy is given as 45.38GeV."

"Since neutrinos cannot be detected directly, their existence is manifested by missing transverse momentum. Here we get a missing transverse momentum of 35.31GeV."

"Okay, now, we use traditional methods to analyze and process the errors."

"First, consider the energy resolution error of the detector, calculate the measurement errors of electron momentum and MET..."

"Then we calculate it through the error propagation formula."

[σM=√￣[(MσE/E)^2+(MσMET/MET)^2]]

...

"Finally, we calculate the partial derivatives and substitute the values, and the final mass is 80.31V, According to the calculation of the standard model, the mass of the W boson should be 80.379, with an error within 2 standard deviations. "

Xiao Yi turned his head and looked at the people present, saying: "Obviously, whether it is the 79.319 we calculated or the standard deviation of 0.044, the gap is really large. Of course, this may also be because the confidence of a single data volume is too low. "

"However, please let me continue to borrow this data and use my new method to analyze and process it. "

"First, we need to recalibrate the data of the detector. Here, the method I use is the maximum likelihood estimation. Of course, if we just use the maximum likelihood estimation, there must be a gap. Then, I will need to introduce some new methods here..."

Xiao Yi's mouth curled up slightly, turned around, and began to write on the blackboard.

As he showed a few simple steps, Tang Yifang and Parisi both squinted their eyes.

This mathematical method...

seems a little different?

Xiao Yi actually introduced a new algorithm to optimize the maximum likelihood estimation!

Among the others, some people also saw some of the mysteries and showed surprised expressions.

"... In this way, we have calibrated the data of this detector, and the data we finally obtained is: electron momentum 45.84GeV, missing transverse momentum 35.65GeV."

After getting this result, Xiao Yi did not stop and continued to the next step: "Next, we will analyze the error."

"Using the error propagation formula in general here will definitely not meet our requirements."

"Other existing system error analysis methods have limitations when dealing with complex data, and cannot fully separate and quantify the impact of various error sources."

"For this, we need to introduce an Error Matrix first."

Error Matrix.

Under the stage, Tang Yifang heard Xiao Yi mention this and quickly recalled the method that Xiao Yi introduced to him ten days ago. It must be said that the error matrix is ​​indeed a very clever method.

And Parisi, who was sitting next to him, didn't know when he took out paper and pen, but followed Xiao Yi to calculate.

It is obvious that he has been completely attracted by what Xiao Yi said.

When he heard the error matrix proposed by Xiao Yi, he raised his head again and listened carefully.

In this way, time passed slowly, and Xiao Yi finally finished explaining the error analysis framework.

"... In the end, we combine all the independent error components and substitute them into such a new error propagation formula to calculate the overall system error."

"This new error propagation formula can help us divide the nonlinear relationship and interaction between various error sources more finely."

"In this way, we can finally get a cleaner data."

"Now, we substitute the initial data into it..."

"We can get the final result that the mass of this W boson is 80.471±0.027GeV!"

Seeing this result, Parisi narrowed his eyes immediately.

This result...

If the range of 5 standard deviations is considered, it is [80.336, 80.606].

Compared with the 80.379 predicted by the standard model, this lower limit is a bit dangerous!

This is almost a gap of 4 standard deviations!

He suddenly realized why Xiao Yi used the W boson as an example.

Could it be...

"Of course, this result is relatively general."

"I don't see anything special. The only thing worth noting is that it is close to 4 standard deviations away from the mass of the W boson predicted by the standard model."

"But if we use this data method to process 2000 sets of data, what will the final result be?"

Xiao Yi smiled and revealed the answer.

As the pages on the PPT turned, the result finally appeared.

【80.438±0.011GeV】

Just now, because Xiao Yi mentioned the standard deviation, when the people in the audience saw this result, they immediately calculated the five standard deviation lower bound of this result.

80.383!

"Fuck?!"

"Oh my god!"

The audience screamed in surprise.

"What is this?!"

"It means that the mass of the W boson is higher than the predicted value of the standard model?"

"This value is really more than 5 standard deviations!"

"Not that much...just more than 4MeV?"

"Not that much? Even if the lower limit is only more than 4MeV, it's enough! Is this enough to publish a PRL?"

...

The whole lecture hall began to hear various low-pitched discussions, from the previous silence to the noise.

How can they not be excited about a discovery beyond the standard model?

This means a new discovery in physics!

But Xiao Yi did not stop them, after all, this is what he wanted.

At this time, Professor Parisi in the first row suddenly asked: "Your data volume is only 2,000?"

Xiao Yi nodded: "Yes, and these data are all from the most recent collision result of BEPC."

"The data volume is still a little small..." Parisi pondered for a moment, and finally said: "I must say that your report really brought me a great surprise."

"It's not just the problem of the W boson being overweight. We all know that the mass of the W boson is given by the Higgs mechanism. Once the mass of the W boson does not match the predicted value under the standard model, it is very likely that the Higgs mechanism is problematic, or in other words, imperfect."

"However, as I said just now, the data volume is still too small."

"If you can use more data to get the result, I think it will help prove your result."

After listening to Parisi's words, Xiao Yi nodded.

At this time, Tang Yifang said: "Professor Parisi, this also needs your help. The data from LHC may help to get a more accurate result."

"This..."

Parisi thought about it, and finally said: "It is possible, but you also know that the latest data of LHC will not be released in the first few years. Xiao Yi needs to come up with something that can convince CERN."

Then, he turned to look at Xiao Yi and said: "If you can write the content of this report into a paper and publish it, I can convince CERN to provide this part of the data."

In response, Xiao Yi naturally nodded: "Of course no problem."

"Okay." Parisi smiled and said: "Then I will wait for you to finish the paper."

...

Chapter 165 CERN's attention

With the end of the report meeting, the speculation about the overweight of the W boson spread directly throughout the Institute of High Energy Physics.

Suddenly, those assistant researchers, intern researchers, and graduate students and postdoctoral students who did not attend the report meeting regretted it.

Such an important discovery, how did you secretly say it at the report meeting?

Wasn't it agreed that this report would only talk about data processing and error analysis?

They just felt that this report was about mathematical methods and they couldn't listen to it, so they didn't come. Anyway, Director Tang only emphasized that researchers and associate researchers must be present.

For a moment, they wanted to cry but had no tears.

However, for those who attended the report, in addition to being amazed at the importance of Xiao Yi's conclusion, they also began to realize how great the role of the new error processing method proposed by Xiao Yi was.

It can be said that the entire achievement originated from this error processing method.

So, those researchers who originally had some complaints about having to attend the report meeting now only had gratitude to Director Tang.

If they hadn't attended this report meeting, they would not have become the first scholars to learn about this method.

Of course, the normal report was also recorded in a video, which has been circulated within the institute.

For example, Tang Yifang also asked everyone to watch it once, including those who did not attend the report meeting.