19 Jan 07

An international collaboration including Oxford scientists has produced the world's most precise measurement by a single experiment of the mass of the W boson, a key parameter of the Standard Model of particles and forces.

The Standard Model in Physics describes three types of forces which reflect our current understanding of fundamental particles and forces of nature: electromagnetic interactions, which cause all phenomena associated with electric and magnetic fields; strong interactions, which bind atomic nuclei; and the weak nuclear force, which governs a form of natural radioactivity and hydrogen fusion, the source of the sun's energy.

The W boson is an elementary particle that mediates the weak nuclear force. Its discovery in 1983 supported the theory of the Standard Model.

The new mass has been determined by CDF collaborators in an experiment at the Tevatron particle collider at Fermilab, near Chicago in the USA.

The Oxford researchers involved are Dr Oliver Stelzer-Chilton, Dr Chris Hays and Professor Peter Renton, Chairman of the CDF committee overseeing the measurement.

Professor Renton said: 'Having been able to determine the new W-mass value with a precision of 0.06 per cent is important because it will lead to a better understanding of another fundamental particle, the Higgs boson. This particle has to date not been discovered by experiments but we can now estimate its mass more accurately: we now know that it is lighter than previously predicted. We are also hoping to be able to observe this elusive particle by experiments at the Tevatron particle collider at Fermilab.'