From Jefferson Lab: “Proton’s Weak Charge Determined for First Time”

Sept. 17, 2013
No Writer Credit

Researchers have made the first experimental determination of the weak charge of the proton in research carried out at the Department of Energy’s Thomas Jefferson National Accelerator Facility (Jefferson Lab).

The results, accepted for publication in Physical Review Letters, also include the determinations of the weak charge of the neutron, and of the up quark and down quark. These determinations were made by combining the new data with published data from other experiments. Although these preliminary figures are the most precise determinations to date, they were obtained from an analysis of just 4 percent of the total data taken by the experiment, with the full data analysis expected to take another year to complete.

Q-weak at Jefferson Lab has measured the proton’s weak charge. No image credit.

The weak force is one of the four fundamental forces in our universe, along with gravity, electromagnetism and the strong force. Although the weak force acts only on the sub-atomic level, we can see its effects in our everyday world. The weak force plays a key role in the nuclear reaction processes that take place in stars and is responsible for much of the natural radiation present in our universe.

The Q-weak experiment was designed by an international group of nuclear physicists who came together more than a decade ago to propose a new measurement at Jefferson Lab. They proposed the world’s first direct measurement of the proton’s weak charge, denoted by the symbol “qyw” represents the strength of the weak force’s pull on the proton, a measure of how strongly a proton interacts via the weak force. Since the weak charge of the proton is precisely predicted by the Standard Model, which is a well-tested theoretical framework that describes the elementary particles and the details of how they interact, it is an ideal parameter to measure experimentally as a test of the Standard Model.

See the full article here, and there is much more.

Thomas Jefferson National Accelerator Facility is managed by Jefferson Science Associates, LLC for the U.S. Department of Energy

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