PROTON RADIUS PUZZLE
In 1987 Discrete Scale Relativity predicted that the radius of the proton would be approximately 0.81 x 10–13 cm, i.e., 0.81 fermi, on the basis of a Schwarzschild metric [Astrophysical Journal 322, 34–36, 1987]. Subsequently a more realistic Kerr-Newman metric yielded a refined DSR prediction of 0.8144 fermi. DSR’s prediction can be compared with the predicted radius of the proton of approximately 0.88 fermi produced by the Quantum Electrodynamics (QED) sector of the Standard Model (SM) of particle physics.
Much to the surprise of theoretical physicists, recent and repeated determinations of the proton radius have yielded a value of approximately 0.8418 fermi for the proton’s charge radius, which deviates from the SM/QED prediction at the 5-sigma level of confidence [Pohl et al, Nature 466, 213–216, 8 July 2010 and Antognini et al, Science 339, 417–420, 25 Jan 2013]. The newest 2017 measurement appears to reduce the proton radius estimate to 0.83 fermi [Beyer et al., Science, Oct 5, 2017]. Experimental determinations of the proton’s magnetic radius have ranged from 0.777 fermi to 0.863 fermi.
The full range of proton radius determinations is roughly 0.75 fermi to 0.88 fermi [see Carroll et al, http://arxiv.org/abs/1108.5785 , Figure 1, 2011]. The median value for this range of proton radius estimates is about 0.815 fermi, which is reasonably close to DSR’s prediction of 0.8144 fermi. So Discrete Scale Relativity’s prediction appears to be more accurate than the Standard Model/QED prediction. The empirical results clearly favor a significantly more compact proton.
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