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Utilizing information from over one billion proton-colliding occasions gathered at CERN’s Large Hadron Collider (LHC), physicists have actually determined the mass of the W boson with record precision. The worth matches the Standard Model’s forecast, providing the scientists self-confidence that no unanticipated force is concealing in the measurement.
CMS prospect crash occasion for a W boson decomposing into a muon(red line)and a neutrino that leaves detection( pink arrow). Image credit: CMS/ CERN.
Found in 1983, the W boson is one of 2 primary particles that embody the weak force, which is one of the 4 essential forces of nature.
The weak force makes it possible for particular particles to alter identities, such as from protons to neutrons and vice versa. This morphing is what drives radioactive decay, in addition to nuclear combination, which powers the Sun.
Capturing a W boson is almost difficult, as it decomposes nearly instantly into 2 kinds of particles, among which, a neutrino, is so evasive that it can not be discovered.
Physicists are delegated determine the other particle, referred to as a muon, and design how it may amount to the overall mass of its moms and dad, the W boson.
In the brand-new research study, the physicists utilized the Compact Muon Solenoid (CMS) experiment, a particle detector at the LHC that exactly tracks muons and other particles produced in the after-effects of proton crashes.
From billions of proton-proton accidents, they recognized 100 million occasions that produced a W boson decomposing to a muon and a neutrino.
For each of these occasions, they performed comprehensive analyses to narrow in on an accurate mass measurement.
In the end, they identified that the W boson has a mass of 80360.2 ± 9.9 megaelectron volts (MeV).
This brand-new mass remains in line with forecasts of the Standard Model, which is physicists’ finest rulebook for explaining the basic particles and forces of nature.
The accuracy of the brand-new measurement is on par with a previous measurement made in 2022 by the Collider Detector at Fermilab (CDF).
That measurement took physicists by surprise, as it was substantially much heavier than what the Standard Model forecasted, and for that reason raised the possibility of brand-new physics, such as particles and forces that have yet to be found.
Due to the fact that the brand-new CMS measurement is simply as accurate as the CDF outcome and concurs with the Standard Model in addition to a variety of other experiments, it is most likely that physicists are on strong ground in regards to how they comprehend the W boson.
“It’s simply a big relief, to be sincere,” stated Dr. Kenneth Long, a physicist at MIT.
“This brand-new measurement is a strong verification that we can rely on the Standard Model.”
The group’s work was released this month in the journal Nature
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CMS Collaboration. 2026. High-precision measurement of the W boson mass with the CMS experiment. Nature 652, 321-327; doi: 10.1038/ s41586-026-10168-5
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