The CMS experiment at CERN is the latest to weigh in on the mass of the W boson—an elementary particle that, along with the Z boson, mediates the weak force, which is responsible for a form of radioactivity and initiates the nuclear fusion reaction that powers the sun. The CMS experiment at CERN is the latest to weigh in on the mass of the W boson—an elementary particle that, along with the Z boson, mediates the weak force, which is responsible for a form of radioactivity and initiates the nuclear fusion reaction that powers the sun. General Physics Phys.org – latest science and technology news stories