One of the fundamental particles of physics may be much heavier than the traditional laws of physics allow. So the measurement could be a sign of a long-awaited “new physics” that goes beyond what was previously known. But independent confirmation is still pending.
In the famous trade magazine Science He has an international team on Thursday mentioned in the data analysis, collected over nearly ten years in the CDF detector of the Tevatron accelerator. The giant machine ran at Fermilab in the US state of Illinois until 2011, but researchers around the world are still analyzing data from collisions of protons and antiprotons. If these particles collide, a large number of other particles are generated as debris from the collision, which is then recorded by detectors. These can also be much heavier than the original protons because the energy of the collision can be converted into mass.
The current post is about the W boson, a particle unknown to the public but also quite fundamental. Just as the particle of light – the photon – is responsible for transmitting the electromagnetic force, the W boson, along with the Z boson, is the carrier of the so-called weak nuclear force, which is one of the four fundamental forces of physics, along with electromagnetism, the strong nuclear force and gravity. Unlike the massless photon, the W boson is very heavy. It weighs up to 80 hydrogen nuclei – this is still even a trillionth of a gram, but for an elementary particle at the lush end.
The measurement caused some excitement in professional circles
Although the Standard Model of particle physics does not provide a direct prediction for the mass of the W boson, it does set narrow limits, which in turn depend on other measured masses, for example the mass of the top quark or the Higgs particle. According to previous measurements, the mass of the W boson should correspond to about 80.37 GeV in the usual unit of particle physics. However, CDF researchers now reach 80.43 GeV, with an uncertainty as low as 0.01 percent. This may not sound like much, but it does not fit the previous measurement. More importantly, it’s much more difficult than the Standard Model allows, with seven massive “standard deviations” – a measure of how much a measurement differs from the expected value given the spread of the data, and seven standard deviations considered a lot.
The analogy caused some excitement in professional circles. After all, physicists have long cursed the Standard Model for being perfect and incomplete. On the other hand, it cannot explain what the mysterious dark matter that fills space is, or why some clumps of particles are very small and others are very large. On the other hand, it has not yet been possible to prove the error. All experiments only confirm the model’s predictions in a frustrating way – apart from recent findings about the muon’s magnetic moment or indicators of so-called leptoquarks, which could also point to new physics. That’s why it’s always exciting when the measurement doesn’t match the prediction. It could be an indicator of unknown particles or new interactions.
But will the current result last? Matthias Schütte of the University of Mainz, who is conducting research at the LHC particle accelerator at CERN near Geneva, is skeptical. “It’s a shame that the work wasn’t posted to the prepress server, as it usually is,” says Schott, who has also been working on the W bosons for a long time. “These measurements are very complex and one can discuss beforehand how to take the various sources of error into account.” for this in Science-Article but not much to read. Schott thinks that before you start speculating why a measurement doesn’t fit the Standard Model, you need to understand why it doesn’t fit past results. Since all measurements to date agree to some extent within the uncertainties, the new measurement is the only one that stands out. First of all, this is fishy.
But does that mean that the work might be fake and worthless? Not for long. “All of the researchers on the CDF team are excellent physicists and the experimental part of the work is really cool,” Schott says. It may turn out that the new measured value is too high and the measurement uncertainty is slightly larger, so that the discrepancy with the previous results is resolved. Then one can combine the measurement with the previous data and the average mass of the W boson on all measurements will be no longer quite extreme, but still higher than the Standard Model allows. “So it gets a lot more exciting again,” Schott says. “It’s definitely worth looking at W boson more.”
This is exactly what many researchers are currently planning: While the Tevatron has long been decommissioned, the LHC particle accelerator is still active, and all data from the last round of measurements is far from evaluating. Measurements of the W boson can also be expected from there in the future.
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