Physicists at CERN in Geneva have obtained a new and more accurate measurement of the mass of the W boson, contradicting last year’s discovery by the Fermilab in Chicago that suggested a flaw in the Standard Model theory describing elementary particles and fundamental forces.
The W boson, discovered in 1983 by Carlo Rubbia and crucial in processes such as radioactive decay and nuclear fusion, cannot be measured directly. Rather, information can be obtained by measuring the mass and energy it releases during decay.
“Due to an undetected neutrino in the particle’s decay, the W mass measurement is among the most challenging precision measurements performed at hadron colliders,” says particle physicist Andreas Hoecker of the ATLAS experiment team at CERN.
Using a new statistical approach, his group has re-examined data obtained in 2011 using the Large Hadron Collider (LHC), arriving at an estimate of the W boson mass that is 16% more precise and with a smaller margin of uncertainty. According to the new calculations, the mass of the W boson is equal to 80.360 gigaelectronvolts, a value much closer to the one predicted by the Standard Model (80.357 gigaelectronvolts) than to the one calculated by the American researchers (80.4335 gigaelettronvolts).
New measurements confirming these data are expected not only from the ATLAS experiment, but also from CMS and LHCb.
© RIPRODUZIONE RISERVATA
