Experiment probes strength of the weak interaction

Published in Physics World, 16 Sep 2013

An international collaboration has made the first determination of the proton’s “weak charge” – a quantity that is related to the strength of the weak interaction. The Q-weak experimental collaboration, working at Jefferson Lab in Newport News, Virginia, says that the small number of data analysed so far agree with predictions of the Standard Model of particle physics but that it believes a full analysis could still reveal the existence of “new physics”.

All the fundamental forces in nature have a strength that is determined by a certain particle parameter. For instance, the strength of gravity is determined by particle mass, while the strength of electromagnetism is determined by electric charge. Similarly, the strength of the weak force, which governs radioactive decay, is determined by a property known as weak charge. In fact, physicists have known that the electric and weak charges are related to one another since the late 1960s, when the electromagnetic and weak forces were unified into a single electroweak theory, which forms part of the Standard Model of particle physics. […]

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