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Particle physics

A weighty mass difference

Nature volume 520, pages 303–304 (2015)Cite this article

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The neutron–proton mass difference, one of the most consequential parameters of physics, has now been calculated from fundamental theories. This landmark calculation portends revolutionary progress in nuclear physics.

Nuclear physics, and many major aspects of the physical world as we know it, hinges on the 0.14% difference in mass between neutrons and protons. Theoretically, that mass difference ought to be a calculable consequence of the quantum theory of the strong nuclear force (quantum chromodynamics; QCD) and the electromagnetic force (quantum electrodynamics; QED). But the required calculations are technically difficult and have long hovered out of reach. In a paper published in Science, Borsanyi et al.1 report breakthrough progress on this problem.

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References

  1. Borsanyi, Sz. et al. Science 347, 1452–1455 (2015).

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  2. Particle Data Group. http://pdg.lbl.gov

  3. Kinoshita, T. (ed.) Quantum Electrodynamics (World Scientific, 1990).

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  4. Kronfeld, A. S. & Quigg, C. Am. J. Phys. 78, 1081–1116 (2010).

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  1. Frank Wilczek is at the Center for Theoretical Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,

    Frank Wilczek

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  1. Frank Wilczek
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Correspondence to Frank Wilczek.

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Wilczek, F. A weighty mass difference. Nature 520, 303–304 (2015). https://doi.org/10.1038/nature14381

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