Rubbia’s W boson mass is ‘larger than expected’. What could change for this matter? – Corriere.it –

Rubbia’s W boson mass is larger than expected. What could change for this matter? Forget for a moment the most famous Higgs boson, discovered at CERN in Geneva. One now on the cover of “Science” is W boson, whose theory was elaborated in the 1960s and discovered by Carlo Rubbia who, thanks to him, shared the Nobel Prize in Physics in 1984 with Simon van der Meer: With the Z boson it is one of the two intermediate particles of the weak force and is responsible, among other things, for the processes of nuclear decay that fuel our Sun. In short: understanding it from the point of view of physics is not so easy. But intuition does matter, yes. To relate it, or rather to associate it with the Higgs boson, is the weak nuclear force, originally discovered by Enrico Fermi and later perfected by the introduction of electromagnetism into the theory. This is to explain the importance of Italian physics up to this point. Now the problem is the metrics. do not return. And they don’t return, they question the so-called Standard Model, the reference theory of physics that describes the world of elementary particles and fundamental forces (in short, matter). For this to know Dedicate his newsstand cover to the new measurement of the mass of the W boson by FermiLab in Chicago. Title: “Heavyweight” Under Fat W Actually: Too Heavy.

Are we experiencing “new physics” as expected, with excessive enthusiasm, through a previous contact from Chicago FermiLab about a year ago? What we can say today, with greater caution, is that we are dealing with “the most accurate measurement of the mass of the W boson ever” As reported by the National Institute of Nuclear Physics, which coordinated participation in the Italian project: “It is the result of a ten-year analysis conducted by the collaboration of the CDF experiment (Collider Detector at Fermilab, a particle accelerator), which has been operating for more than 25 years at the Fermi Laboratory’s Tevatron accelerator. National Accelerator in the US The value obtained from scientific cooperation through this careful analysis differs from that predicted by the Standard Model, which describes the world of elementary particles and fundamental forces.” Technical language to say it was not easy to make such statements.

“We did everything we could to be strict before opening the ‘box’ of results,” Giorgio Chiarelli, a researcher in the Pisa department of Infn and co-chair of scientific collaboration at CDF, told Corriere della Sera.. “For ten years, we validated the method without knowing the result. This is so that we don’t get swayed: we’re all men and women…sometimes we risk deceiving ourselves that we’ll find exactly what we’re looking for. That’s why we waited so long. I still remember when we opened the “box” in November 2000. It was a very special moment. We were all on Zoom. But even at that moment there was a very calm discussion.” “As the sociologist Robert Merton has stated, Chiarelli adds, one of the pillars of science is organized skepticism. Now I’m expecting some excitement, but I’m also expecting organized skepticism. We realize that the absolute truth of science does not exist. Truth is only nature..

“Over the past 40 years, many accelerator experiments have measured the mass of the W boson: these are complex measurements but over time increasing levels of accuracy have been achieved,” Chiarelli commented. “It has taken us many years to fully evaluate all the different aspects that need to be taken into account and to carry out all the necessary audits and verifications. To date, this is our strongest metric, and the discrepancy between the expected and measured value still exists.”

The measurement of the mass of mediators W and Z is particularly important, because unlike other particles in the Standard Model, their value is predicted by theory. Thanks to this new CDF measurement, the researchers determined the mass of the W particle with an accuracy of 0.01%, which is two times greater than previous best measurements, and this allows them to test the current theoretical framework that describes nature at the level of its basic components. The result was based on the observation and analysis of 4.2 million candidate W particles, four times that of the analysis published by the same collaboration in 2012. The new value of the W particle is consistent with many previous measurements, but there are also others that differ from them. . Therefore, future steps will be needed to clarify this aspect.

In short, either the analogy is wrong or the theory is incomplete: “It’s the first crack that opens up in the Standard Model,” Chiarelli added. But the ball, in fact the particle, now passes to CERN which will have to re-measure. For now, the yellow color of physics is destined to remain so: it will take years.

“If confirmed, the discrepancy between the measurement we obtained and the one perceived in the Standard Model would be very significant,” Chiarelli added. A conclusion also shared by another great expert in particle physics, scientist Fernando Veroney: “If confirmed, we must conclude that in the Standard Model theory there is at least one subtle effect on which we have not yet focused. We must question the global picture.” The Standard Model describes – continues Chiarelli – The material we made, but we’ve known for some time that it couldn’t be the final theory. Small differences were observed here and there, not nearly as important as our group. If our result is confirmed, it will give directions for consideration.” It is now a matter of verifying the data by repeating the experiment, and this will be possible at CERN. “It will take years,” he notes. “So far, this is our most solid measure, and the discrepancy between the expected value and the measured value still exists,” Chiarelli says. It’s a measurement ‘accurate to 0.01%, hard to reproduce. It’s a challenge.”

Matter can wait: The age of the universe is 13.7 billion years. Homo sapiens 100-200 thousand years old. The scientific method is 400 years old. Particles, patience and prudence must have something in common.