Event

The mass of the W boson, a mediator of the weak force between elementary particles, is tightly constrained by the symmetries of the standard model of particle physics. We have performed the most precise measurement of the W boson mass using data corresponding to 8.8 inverse femtobarns of integrated luminosity collected in proton-antiproton collisions at 1.96 TeV center-of-mass energy with the CDF II detector at the Fermilab Tevatron collider. The measured value is in significant tension with the prediction.