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Scientists Measure the Weak Charge of the Proton

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An international collaboration of scientists has for the first time directly measured the strength of the weak nuclear force acting between a single electron and a single proton. Published in Nature (https://goo.gl/qZ1hdP), the measurement supports the Standard Model of particle physics, and places constraints on the possibilities for new types of forces beyond our present knowledge.

“This is the first time a dedicated experiment has directly measured the strength of the weak nuclear force acting between a single electron and a single proton,” said A/Prof Ross Young of the University of Adelaide’s School of Physical Sciences, who collaborated on the experiment. “The strength of this force is governed by the ‘weak charge’ of the proton, in much the same way as the strength of the electromagnetic force is governed by the proton’s electric charge. Measuring this effect has proven difficult because the weak force is so much weaker than the electro­magnetic.”

To measure the proton’s weak charge, an intense beam of highly polarised electrons was directed onto a target containing cold liquid hydrogen, and the electrons scattered from this target were then detected.

The key to the experiment was that the electrons in the beam were mostly spinning in one direction, parallel or anti-parallel to...

The full text of this article can be purchased from Informit.