Refined W-boson mass points to physics beyond the Standard Model
(ORDO NEWS) — Long-term experiments at the Tevatron collider have made it possible to determine the mass of W-bosons with unprecedented accuracy, but the obtained value does not coincide with the predictions of the standard model.
An analysis of data from a long-closed collider made it possible to find millions of events – candidates for W ± -bosons and calculate the mass of these particles with record accuracy.
However, the number obtained by physicists differs markedly from the predictions of the standard model. Perhaps this result indicates a long-awaited breakthrough in the search for a more complete picture of the physical world.
Modern physics is based on the standard model of quantum mechanics, which describes elementary particles and fundamental interactions between them.
The carriers of these interactions are bosons: photons are “responsible” for the electromagnetic, gluons for the strong, and uncharged Z-bosons and charge-carrying W ± -bosons for the weak.
The weak force is responsible for some forms of radioactive decay and many other processes that occur with particles and with the nuclei of atoms.
The Standard Model is in excellent agreement with most experiments, giving correct and accurate predictions that have been verified many times over.
However, it also offers a far from complete picture of the physical world. In particular, this concept does not describe gravity in any way; there are no particles that could play the role of dark matter, and so on.
In an effort to find the foundations of a new, comprehensive theory, physicists are experimenting with accelerators and colliders.
Most of this work is connected with the search for new particles unknown to the Standard Model or with the refinement of the characteristics of already known ones. Such data can at least indicate the direction of the search for a new theory.
This was also done by physicists from the CDF international collaboration, calculating data collected by the Tevatron collider at the American Fermi National Accelerator Observatory.
The experiments themselves were completed in 2011, but the analysis of the information received is still ongoing. The scientists tracked the W-bosons produced by proton-antiproton collisions on the CDF-II detector.
In the experiments of 1985-2011, about 4.2 million such candidates were registered. The calculations were carried out with an accuracy of about 0.01 percent (twice as good as the previous ones) and showed that the mass of the W-bosons is 80433 MeV/c 2.
This is about 80 times more massive than a proton. But the main thing is that the value predicted by the standard model is 80357 MeV/c 2.
The difference from the new estimate of the W-boson mass is more than enough (seven sigma) in order not to consider this discrepancy as something accidental or insignificant.
However, it is not yet clear how to interpret this result: perhaps new particle accelerators and colliders, which are planned or are already being built in different countries, will help this. They will make it possible to register W-bosons arising from other processes in order to additionally verify and refine the result obtained.
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