New measurement yields smaller proton radius

Using the first new method in half a century for measuring the size of the proton via electron scattering, the PRad collaboration has produced a new value for the proton’s radius in an experiment conducted at the Department of Energy’s Thomas Jefferson National Accelerator Facility.

The result, recently published in the journal Nature, is one of the most precise measured from electron-scattering experiments. The new value for the proton radius that was obtained is 0.831 fm, which is smaller than the previous electron-scattering value of 0.88 fm and is in agreement with recent muonic atomic spectroscopy results.
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