Prof. Ashutosh Kotwal

The mass of the W boson, a mediator of the weak force between elementary particles, is calculable in the standard model of particle physics. The Higgs boson was the last missing component of the model. After observation of the Higgs boson, a measurement of the W boson mass provides a stringent test of the model. We measure the W boson mass, MW, using the full dataset of the CDF II detector which operated at the Fermilab Tevatron collider. We obtain MW = 80,433.5 ± 9.4 MeV/c2, the precision of which exceeds that of all previous measurements combined. This measurement is in significant tension with the standard model expectation of MW = 80,357 ± 6 MeV/c2, a 7sigma difference. We will survey the concepts and assumptions of the standard model, which over the last century has been one of the most successful theories in physics. We will discuss how the W boson mass points towards a more complete theory of fundamental particles and interactions in nature.