The most accurate measurement of the mass of the W-boson differs from the prediction of the standard model

The most accurate W-boson mass measurement shows the tension with the standard model.

After 10 years of careful analysis and verification, scientists from the CDF’s collaboration at the US Department of Energy’s National Fermi Accelerator Laboratory announced on April 7, 2022, that they had achieved the most accurate measurement to date of the mass of W-boson, one of nature’s force particles. Using data collected by a collider detector in Fermilab, or CDF, scientists have now determined the mass of the particle with an accuracy of 0.01% – twice as accurate as the previous best measurement. This corresponds to a weight measurement of an 800-pound gorilla up to 1.5 ounces.

A new measurement of accuracy published in the journal Science, allows scientists to test a standard model of particle physics, a theoretical basis that describes nature at its most fundamental level. Result: The new mass value shows the tension with the value that scientists obtain using experimental and theoretical data in the context of a standard model.

Collider detector Fermilab

The collider detector at Fermilab recorded high-energy particle collisions created by the Tevatron collider from 1985 to 2011. About 400 scientists from 54 institutions in 23 countries are still working on a large amount of data collected as a result of the experiment. Credit: Fermilab

“The number of improvements and additional tests that have resulted in us is huge,” said Ashutosh W. Kotval of Duke University, who led the analysis and is one of 400 scientists in the CDF’s collaboration. “We have taken into account our best understanding of our particle detector, as well as advances in the theoretical and experimental understanding of the interaction of the W-boson with other particles. When we finally published the result, we found that it differed from the forecast of the standard model.

If confirmed, this measurement indicates the potential need to improve the calculation of the standard model or extend the model.

Now scientists have determined the mass of the W-boson with an accuracy of 0.01%. This is twice as accurate as the previous best measurement, and shows the voltage with the standard model.

The new value is consistent with many previous measurements of W-boson mass, but there are some disagreements. Future measurements will be needed to shed more light on the result.

“While this is an intriguing result, the measurement needs to be confirmed by other experiments before it can be fully interpreted,” said Fermilab Deputy Director Joe Liken.

The W-boson is a messenger particle of weak nuclear power. It is responsible for nuclear processes that cause the sun to shine and particles to disintegrate. Using high-energy particle collisions created by the Tevatron collider at Fermilab, the CDF collaboration collected a huge amount of data containing W-bosons from 1985 to 2011.

Standard particle model

The W-boson is a messenger particle of a weak nuclear power. It is responsible for nuclear processes that cause the sun to shine and particles to disintegrate. CDF scientists are studying the properties of the W-boson using data collected by them on the Tevatron collider at the Fermila laboratory. Credit: Fermi National Accelerator Laboratory

CDF physicist Chris Hayes from Comparison of W-boson masses

The mass of the W-boson is about 80 times the mass of the proton, or about 80,000 MeV / s2. Collider Detector scientists in the Fermilab collaboration have achieved the most accurate measurement in the world. The CDF value has an accuracy of 0.01 percent and coincides with many measurements of W-boson mass. It shows the tension with the expected value based on the standard model of elementary particle physics. Horizontal bands show the uncertainty of the measurements achieved by the various experiments. The LHCb result was published after the submission of this paper and is 80354 + – 32 MeV / s2. Credit: CDF collaboration

“Many collide experiments have measured the mass of the W-boson over the past 40 years,” said CDF co-secretary Giorgio Chiarelli, Italian National Institute of Nuclear Physics (INFN-Pisa). “These are complex, complex measurements, and they have achieved increasing accuracy. It took us many years to go through all the details and necessary checks. This is our most reliable measurement to date, and the mismatch between measured and expected values ​​persists. ”

The collaboration also compared their result with the best value expected for the W-boson mass using a standard model of 80,357 ± 6 MeV / c2. This value is based on complex calculations of the standard model, which intricately correlate the mass of the W-boson with measurements of the masses of two other particles: the upper quark discovered at the Tevatron collider in Fermilab in 1995, and the Higgs boson Related

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