The most precise measurement of the mass of the W boson deviates from the standard model
After 10 years of analysis and multiple validation, researchers of the CDF collaborative project led by the Fermi National Accelerator Laboratory (Fermilab) announced that they have the most accurate measurements of the mass of the W bosons, the bearer of one of the four fundamental physical interactions. The results suggest that the standard model should be improved or extended.
We know the four basic physical interactions: Gravitation, weakness, electromagnetic and strong interaction. The w-Boson is the carrier of the weak interaction. Based on data from Collider Detector at Fermilab (CDF), the scientists at Fermilab have determined the mass of the W boson with an accuracy of 0,01%. The measurement is twice as accurate as before. Once established, scientists used the new value to test the standard model.
We made a large number of fixes and additional checks. In doing so, we have our improved understanding of the particle detector itself as well as advances in the theoretical and experimental understanding of the interaction of the W bosons with other particles considered. When we finally did all the calculations, we found that they deviated from the Standard Model's predictions," says Ashutosh V. Kotwal of Duke University, who led the group that performed the calculations. He is one of 400 scientists working in the framework of CDF cooperation work together.
The new measurements agree in many respects with earlier measurements w bosonagree, but deviate from them in a number of respects. Therefore, further investigations are required. These are very intriguing results, but they need to be confirmed by other experiments to fully explain them, says Fermilab Associate Director Joe Lykken.
The W boson, a carrier of the weak interaction, is responsible, among other things, for the processes that make the sun shine and cause the particles to decay. The Fermilab, which is very valuable for science Tevatron accelerator has an enormous amount of data collected between 1985 and 2011. The CDF measurements have been carried out over many years. The results of these measurements were hidden in the data that had to be analyzed in detail. When we finally got them, we were amazed, says Oxford University physicist Chris Hays.
The mass of W boson is about 80 times larger than that of the proton and is about 80.000 MeV/c2. Scientists at Fermilab have now specified the method. Thanks to their work, we now know that it is 80 ± 433 MeV/c9. This result is based on research by 4,2 million W bosonsn carried out at Fermilab.
Over the past 40 years, experiments at numerous accelerators have made it possible to study the W bosons allows. These are very difficult and complex measurements that are constantly being refined. Our work has lasted for many years. We made the most accurate measurements, so we could conclude that there is a discrepancy between the measured and the expected value," says CDF collaboration spokesman Giogrio Chiarelli of Italy's National Institute for Nuclear Physics.
The most accurate calculation of the mass of the W bosons based on the Standard Model - those based on measurements of the masses of the top quark and the Higgs bosons - gives a result of 80 357 ± 6 MeV/c2. So the difference between the theoretical calculations and the measurements carried out is obvious. Now the authors of further experiments and theoretical physicists should try to explain them. If the difference between the experimental results and the theoretical calculations is due to the presence of a new interaction - and this is only one possibility - then future experiments should reveal it.