June 29, 2022

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Physicists are elated by W Boson .’s new measurement

Physicists are elated by W Boson .'s new measurement

Workers at the particle collider at Fermilab.

A team of hundreds of scientists has precisely measured the mass of the W boson, an elementary particle responsible for the weak nuclear force. The researchers found, to their surprise, that The boson is more massive than expected Standard Form In particle physics, the working theory that describes many of the fundamental forces in the universe.

The new value was extracted from 10 years of experiences and calculations by 400 researchers in 54 different institutions around the world, an amazing effort. All data were collected from experiments on four floors, 4500-tons collider detector (CDF-II for short) at Fermilab’s Tevatron Accelerator near Chicago, Illinois.

CDF collaboration found W . group The mass of the boson is 80,433 +/- 9 MeV/c^2, which is a number Almost double the accuracy of its previous measurement collective. To get a sense of the scale, the new measurement places the W boson about 80 times the mass of the proton. Team results published Today in science.

“The truth is, what happened here is the number of times things happen in science. We looked at the number, And we said, “Huh, that’s funny,” David Tupac, a physicist at Texas A&M University and a spokesperson for the CDF Collaboration, said in a video call.. “You could see she was just washing people. It was quiet. We didn’t know what to make of it.”

“We were very pleasantly surprised [with the result]Wrote Ashutosh Kotwal, a physicist at Duke University and a member of the CDF Collaboration, in an email. “We were so focused on the accuracy and robustness of our analysis that the value itself came as a wonderful shock.”

W boson is related to weak nuclear powera primary reaction responsible for one type of radioactive decay and nuclear fusion that occurs in stars. Don’t worry – the boson has a much different mass than expected doesn’t mean we’ve misunderstood things like nuclear fusion – but it does mean that there’s still a lot we don’t understand about the particles that make up the universe and how they interact.

A graph showing the exact result of the last experiment.

“The Standard Model is the best we have for particle physics. It’s amazingly good. The problem is we know we’re wrong,” Tupac said. Doing the Standard Model correctly, which might give us an idea of ​​what’s more correct?

The standard model predicts a value for the mass of a W boson, a value the team sought to challenge with a rating of 4 One million filter bosons produced by collisions between protons and antiprotons at Fermilab. Their result was higher than the standard model predictions Huge seven standard deviations. Kotwal, who posted five Increasingly accurate measurements of the particle’s mass over the past 28 years, she said, “tThe odds of increasing the seven standard deviations are statistical luck less than 1 in a billion.”

Tupac likened the measurement to measuring a gorilla weighing 800 pounds in one ounce of its actual weight. As with many scientific experiments—particularly in particle physics, where masses are very slight—the researchers blinded their results, to ensure that the calculations weren’t affected by any expectations or hopes of the research team.

But now, with a very precise measurement that is much different than before, minimum By estimates, physicists have the unenviable task of figuring out what the Standard Model is not. It certainly isn’t the first time that subatomic physics has actually proven to be different from humanity’s best guesses. last AprilMuon g-2 Collaboration found additional evidence that the properties of MYUN (another subatomic particle) may not agree with the predictions of the Standard Model. And two of the most important facts of the universe – gravity and dark matter – are Famous that the model did not explain.

A worker looks at the huge detector.

The 4,500-ton Fermilab Collider Detector.
Photo: © Corbis / Corbis (Getty Images)

“In order to know what the most fundamental theory might be, it is important to find phenomena that cannot be explained by [Standard Model]”, By email Claudio Campaniari, a physicist at the University of California-Santa Barbara is not affiliated with the latest study. In other words, the phenomena in which the [Standard Model] The approximation is collapsing.” Campagmari Co-authored by Viewpoints article About The new measurement.

There are trials prepared to do this; they will Investigate the implications of today’s discovery through various collision experiments. Results are still forthcoming from ATLAS and Muon Compact Solenoid (CMS)two detectors at CERN’s Large Hadron Collider (the two detectors responsible for Discovering the Higgs boson Since 10 years). and the big high light hadron collider-that Development who – which The number of possible collisions will increase by a factor of 10– It will also boost Opportunities Seeing compelling new particles when they are completed in 2027.

CDF collisions were between protons and antiprotons, while the large hadron collider The collision of a proton and a proton results. Kotwal said if humans built an electron-positron collider, It will allow accurate measurements and search for large rare processes hadron collider can not be produced.

As Martijn Mulders, a physicist at CERN who co-wrote the Perspectives article said, In an email, the physicists will take a two-pronged approach to test the model: measure known particles (such as the W boson) with increasing accuracy, as well as discover entirely new particles. new particles They are often found by “hunting” hunting.: sifting through the subatomic Mush drilling noise to see what was generated unexpectedly.

The Tevatron accelerator was closed in 2011, right after the experimental collaboration ended. So today’s result is the afterlife for the storied instrument, and a huge W for the team and particle physics as a whole.

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